Like many states, the UK government has committed to supporting disruptive innovations.1 These are considered to hold greater potential for economic growth and development than incremental advances in established technologies. Within this broad strategy the bioeconomy, the area of industrial activity based on commercialising life sciences research is given a particular importance. The bioeconomy includes sectors like biofuels, agricultural biotechnology, and medical biotechnology.2 In the latter case, advances in medical biotechnologies hold promise for treating, and even curing, serious and chronic diseases as well as driving growth and prosperity. Regenerative medicine (RM), the biotechnology-based use of cells, tissues, and genes as medicinal products, is certainly disruptive in that they differ in important ways from traditional pharmaceuticals and medical devices.3

The UK has taken a number of policy measures to support the development of the RM industry. The Regenerative Medicine Platform funding schemes promote and co-ordinate academic translational research. The Catapult centres, including the Cell and Gene Therapy Catapult, the Medicines Discovery Catapult and the High Value Manufacturing Catapult, provide advice, facilities and infrastructure to support businesses, especially Small and Medium-sized Enterprises (SMEs); with potential to contribute to the RM value chain. The Medicines and Healthcare products Regulatory Agency (MHRA) Innovation Office offers a RM advice service to help academic and commercial developers navigate the complex regulatory framework for biological therapies, while the recent Accelerated Access Review proposed a raft of measures to speed up the regulatory timeline for transformative new therapies more generally.4

However, it does not necessarily follow that all parts of the biomedical sector will be equally disrupted by any given RM technology, nor that all RM technologies will be disruptive in exactly the same way.5 The ESRC-funded Biomodifying Technologies project6 analysed three case studies of biotechnologies with disruptive potential: gene-editing which allows faster, more accurate genetic modification, induced pluripotent stem cell (iPSC) technology that allows an ordinary skin or blood cell to be turned into a stem cell capable of producing any tissue type in the human body, and 3D bioprinting which can produce three-dimensional structures made from living tissues.

Gene editing and iPSC are advances on earlier generations of genetic engineering and stem cell technologies. They align reasonably well with the existing skill sets, goals, equipment, and techniques of researchers working in both academic and commercial settings. They are not especially disruptive at the level of basic research. Bioprinting requires skills, tools and techniques from engineering, materials chemistry, computer-aided design, biology, and medicine. This has necessitated greater disruption in the form of organisational change, to create new research groups and foster collaborative learning across disciplines.

For all three technologies, there are also well-established pathways to extract near-term value from basic research: peer-reviewed publications, patent applications, and the market for reagents, tools, and equipment. Each case demonstrates clear growth in the number of papers, patents, and reagent/equipment sales, although the rate of acceleration is greatest for CRISPR-based gene editing and slowest for bioprinting.

The pathways to realise longer-term, clinical, and economic value are less well established for RM. The healthcare sector is seen as particularly resistant to disruptive innovations, due to the lengthy regulatory process and powerful incumbent firms, which have historically been wary of investing in RM.7 The process of scaling laboratory protocols for cell or gene-based therapies into industrial procedures, taking products through clinical trials to establish safety and efficacy, and securing reimbursement, is every bit as experimental and involves as much learning by trial and error as exploratory laboratory research, but with much higher financial stakes. Interest from incumbents appears to be growing, as recent years have seen an increase in the number of cell or gene-based therapies reaching the market. However, there is no off the shelf manufacturing solution, as different RM products have different attributes: in the industry there is a popular idiom the product is the process. This means that the acceleration seen at the basic R&D stage does not unproblematically translate into speedy translation further down the pathway.

Rather, initial clinical applications of gene editing, iPSC and bioprinting are targeted at a more limited range of niche applications. The niches for each technology are shaped by a number of critical factors. Smaller tissues, such as the eye require fewer replacement cells or lower titres of gene editing vector, which are more manageable with current manufacturing capacity. The challenges of manufacturing at scale, combined with high anticipated costs, combine to make narrowly defined subsets of disease categories, with high unmet need, a preferred route for commercial development, especially where there is potential for a disruptive new product to demonstrate significant Quality of Life gains over the current standard of care.

Indications that draw on procedures, standards and requirements established for previous therapies are seen as less risky and thus promising clinical targets. Gene editing to treat thalassemia and other blood disorders builds on decades of clinical expertise with the bodys haematopoietic (blood-forming) system, gained by treating leukaemia patients. Even treatments that were not ultimately successful such as foetal stem cell transplants for Parkinsons disease (PD) can provide expertise with clinical trials and regulation to support a next-generation iPSC-based cell therapy for PD.

While the government has rightly been wary of picking winners, as particular niches for early clinical adoption of biomodifying technologies become apparent they may require specific, targeted support, to complement the broader support for the field already provided by polices described above. Innovations in related fields such as biomaterials and automation, potentially supported by the High Value Manufacturing Catapult, are likely to improve manufacturing capacity and speed over time. These innovations may be relatively incremental in the manufacturing phase but could have disruptive effects further down the value chain at the clinical delivery phase, as greater supply makes biomodifying RM therapies accessible to less tightly defined patient cohorts. The next policy challenge will be to provide targeted support for clinical delivery whilst avoiding lock-in to infrastructure or procedures that would inhibit the evolution of the field over time.

The research underpinning this piece was supported by the Economic and Social Research Council grant number ES/P002943/1 and the Leverhulme Trust grant number RPG-2017-330

References

1 Department for Business, Industry and Industrial strategy (2017) Industrial Strategy: building a Britain fit for the future. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/730048/industrial-strategy-white-paper-web-ready-a4-version.pdf

2 Department for Business, Industry and Industrial strategy (2018) Bioeconomy strategy: 2018 to 2030. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/761856/181205_BEIS_Growing_the_Bioeconomy__Web_SP_.pdf

3 Open Access Government (2019) The promises and challenges of biomodifying technologies for the UK https://www.openaccessgovernment.org/biomodifying-technologies/68041/

4 Accelerated Access Review (AAR). (2016). Final Report: Review of Innovative Medicines and Medical Technologies. London: The Crown.

5 Joyce Tait & David Wield (2019) Policy support for disruptive innovation in the life sciences, Technology Analysis & Strategic Management, DOI: 10.1080/09537325.2019.1631449

6 Open Access Government (2019) The promises and challenges of biomodifying technologies for the UK https://www.openaccessgovernment.org/biomodifying-technologies/68041/

7 Joyce Tait & David Wield (2019) Policy support for disruptive innovation in the life sciences, Technology Analysis & Strategic Management, DOI: 10.1080/09537325.2019.1631449

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Targeted policy support for emerging biomedical innovations - Open Access Government

TORONTO, March 31, 2020 /CNW/ - The Gairdner Foundation is pleased to announce the 2020 Canada Gairdner Award laureates, recognizing some of the world's most significant biomedical research and discoveries. During these challenging times, we believe it is important to celebrate scientists and innovators from around the world and commend them for their tireless efforts to conduct research that impacts human health.

2020 Canada Gairdner International AwardThe five 2020 Canada Gairdner International Award laureates are recognized for seminal discoveries or contributions to biomedical science:

Dr. Masatoshi TakeichiSenior Visiting Scientist, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan; Professor Emeritus, Kyoto University, Kyoto, Japan

Dr. Rolf KemlerEmeritus Member and Director, Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany

Awarded "For their discovery, characterization and biology of cadherins and associated proteins in animal cell adhesion and signalling."

Dr. Takeichi

The Work: The animal body is made up of numerous cells. Dr. Takeichi was investigatinghow animal cells stick together to form tissues and organs, and identified a key protein which he named 'cadherin'.Cadherin is present on the surface of a cell and binds to the same cadherin protein on the surface of another cell through like-like interaction, thereby binding the cells together. Without cadherin, cell to cell adhesion becomes weakened and leads to the disorganization of tissues. Dr. Takeichi found that there are multiple kinds of cadherin within the body, each of which are made by different cell types, such as epithelial and neuronal cells. Cells with the same cadherins tend to cluster together, explaining the mechanism of how different cells are sorted out and organized to form functional organs.

Further studies by Dr. Takeichi's group showed that cadherin function is supported by a number of cytoplasmic proteins, includingcatenins, and their cooperation is essential for shaping of tissues. His studies also revealed that the cadherin-dependent adhesion mechanism is involved in synaptic connections between neurons, which are important for brain wiring.

Dr. Kemler

The Work: Dr. Kemler, using an immunological approach, developed antibodies directed against surface antigens of early mouse embryos. These antibodies were shown to prevent compaction of the mouse embryo and interfered with subsequent development. Both Dr. Kemler and Dr. Takeichi went on to clone and sequence the gene encoding E-cadherin and demonstrate that it was governing homophilic cell adhesion.

Dr. Kemler also discovered the other proteins that interact with the cadherins, especially the catenins, to generate the machinery involved in animal cell-to-cell adhesion. This provided the first evidence of their importance in normal development and diseases such as cancer. It has been discovered that cadherins and catenins are correlated to the formation and growth of some cancers and how tumors continue to grow. Beta catenin is linked to cell adhesion through interaction with cadherins but is also a key component of the Wnt signalling pathway that is involved in normal development and cancer. There are approximately 100 types of cadherins, known as the cadherin superfamily.

Dr. Takeichi

The Impact: The discovery of cadherins, which are found in all multicellular animalspecies, has allowed us to interpret how multicellular systems are generated and regulated. Loss of cadherin function has been implicated as the cause of certain cancers, as well as in invasiveness of many cancers. Mutations in special types of cadherin result in neurological disorders, such as epilepsy and hearing loss. The knowledge of cadherin function is expected to contribute to the development of effective treatments against such diseases.

Dr. Kemler

The Impact: Human tumors are often of epithelial origin. Given the role of E-cadherin for the integrity of an epithelial cell layer, the protein can be considered as a suppressor of tumor growth. The research on the cadherin superfamily has had great impact on fields as diverse as developmental biology, cell biology, oncology, immunology and neuroscience. Mutations in cadherins/catenins are frequently found in tumors. Various screens are being used to identify small molecules that might restore cell adhesion as a potential cancer therapy.

Dr. Roel NusseProfessor & Chair, Department of Developmental Biology; Member, Institute for StemCell Biology andRegenerativeMedicine, Stanford University, School of Medicine.Virginia and Daniel K. Ludwig Professor of Cancer Research. Investigator, Howard Hughes Medical Institute

Awarded"For pioneering work on the Wnt signaling pathway and its importance in development, cancer and stem cells"

The Work: Dr. Nusse's research has elucidated the mechanism and role of Wnt signaling, one of the most important signaling systems in development. There is now abundant evidence that Wnt signaling is active in cancer and in control of proliferation versus differentiation of adult stem cells, making the Wnt pathway one of the paradigms for the fundamental connections between normal development and cancer.

Among Dr. Nusse's contributions is the original discovery of the first Wnt gene (together with Harold Varmus) as an oncogene in mouse breast cancer. Afterwards Dr. Nusse identified the Drosophila Wnt homolog as a key developmental gene, Wingless. This led to the general realization of the remarkable links between normal development and cancer, now one of the main themes in cancer research. Using Drosophila genetics, he established the function of beta-catenin as a mediator of Wnt signaling and the Frizzleds as Wnt receptors (with Jeremy Nathans), thereby establishing core elements of what is now called the Wnt pathway. A major later accomplishment of his group was the first successful purification of active Wnt proteins, showing that they are lipid-modified and act as stem cell growth factors.

The Impact: Wnt signaling is implicated in the growth of human embryos and the maintenance of tissues. Consequently, elucidating the Wnt pathway is leading to deeper insights into degenerative diseases and the development of new therapeutics. The widespread role of Wnt signaling in cancer is significant for the treatment of the disease as well. Isolating active Wnt proteins has led to the use of Wnts by researchers world-wide as stem cell growth factors and the expansion of stem cells into organ-like structures (organoids).

Dr. Mina J. Bissell Distinguished Senior Scientist, Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory; Faculty; Graduate Groups in Comparative Biochemistry, Endocrinology, Molecular Toxicology and Bioengineering, University of California Berkeley, Berkeley, CA, USA

Awarded "For characterizing "Dynamic Reciprocity" and the significant role that extracellular matrix (ECM) signaling and microenvironment play in gene regulation in normal and malignant cells, revolutionizing the fields of oncology and tissue homeostasis."

The Work: Dr. Mina Bissell's career has been driven by challenging established paradigms in cellular and developmental biology. Through her research, Dr. Bissell showed that tissue architecture plays a dominant role in determining cell and tissue phenotype and proposed the model of 'dynamic reciprocity' (DR) between the extracellular matrix (ECM) and chromatin within the cell nucleus. Dynamic reciprocity refers to the ongoing, bidirectional interaction between cells and their microenvironment. She demonstrated that the ECM could regulate gene expression just as gene expression could regulate ECM, and that these two phenomena could occur concurrently in normal or diseased tissue.

She also developed 3D culture systems to study the interaction of the microenvironment and tissue organization and growth, using the mammary gland as a model.

The Impact:Dr. Bissell's model of dynamic reciprocity has been proven and thoroughly established since its proposal three decades ago and the implications have permeated every area of cell and cancer biology, with significant implications for current and future therapies. Dr. Bissell's work has generated a fundamental and translationally crucial paradigm shift in our understanding of both normal and malignant tissues.

Her findings have had profound implications for cancer therapy by demonstrating that tumor cells can be influenced by their environment and are not just the product of their genetic mutations. For example, cells from the mammary glands grown in two-dimensional tissue cultures rapidly lose their identity, but once placed in proper three-dimensional microenvironments, they regain mammary form and function. This work presages the current excitement about generation of 3D tissue organoids and demonstrates Dr. Bissell's creative and innovative approach to science.

Dr. Elaine FuchsHoward Hughes Medical Institute Investigator and Rebecca C. Lancefield Professor and Head of the Robin Chemers Neustein Laboratory of Mammalian Cell Biology and Cell Biology; The Rockefeller University, New York, NY, USA

Awarded"For her studies elucidating the role of tissue stem cells in homeostasis, wound repair, inflammation and cancer."

The Work: Dr. Fuchs has used skin to study how the tissues of our body are able to replace dying cells and repair wounds. The skin must replenish itself constantly to protect against dehydration and harmful microbes. In her research, Fuchs showed that this is accomplished by a resident population of adult stem cells that continually generates a shell of indestructible cells that cover our body surface.

In her early research, Fuchs identified the proteins---keratinsthat produce the iron framework of the skin's building blocks, and showed that mutations in keratins are responsible for a group of blistering diseases in humans. In her later work, Fuchs identified the signals that prompt skin stem cells to make tissue and when to stop. In studying these processes, Fuchs learned that cancers hijack the fundamental mechanisms that tissue stem cells use to repair wounds. Her team pursued this parallel and isolated and characterized the malignant stem cells that are responsible for propagating a type of cancer called "squamous cell carcinoma." In her most recent work, she showed that these cells can be resistant to chemotherapies and immunotherapies and lead to tumor relapse.

The Impact: All tissues of our body must be able to replace dying cells and repair local wounds. Skin is particularly adept at performing these tasks. The identification and characterization of the resident skin stem cells that make and replenish the epidermis, sweat glands and hair provide important insights into this fountain of youth process and hold promise for regenerative medicine and aging. In normal tissues, the self-renewing ability of stem cells to proliferate is held in check by local inhibitory signals coming from the stem cells' neighbours. In injury, stimulatory signals mobilize the stem cells to proliferate and repair the wound. In aging, these normal balancing cues are tipped in favour of quiescence. In inflammatory disorders, stem cells become hyperactivated. In cancers, the wound mechanisms to mobilize stem cells are hijacked, leading to uncontrolled tissue growth. Understanding the basic mechanisms controlling stem cells in their native tissue is providing new strategies for searching out refractory tumor cells in cancer and for restoring normalcy in inflammatory conditions.

2020 John Dirks Canada Gairdner Global Health AwardThe 2020 John Dirks Canada Gairdner Global Health Award laureate is recognized for outstanding achievements in global health research:

Professor Salim S. Abdool KarimDirector of CAPRISA (Centre for the AIDS Program of Research in South Africa), the CAPRISA Professor in Global Health at Columbia University, New York and Pro Vice-Chancellor (Research) at the University of KwaZulu-Natal, Durban, South Africa

Professor Quarraisha Abdool KarimAssociate Scientific Director of CAPRISA, Professor in Clinical Epidemiology, Columbia University, New York and Professor in Public Health at the Nelson Mandela Medical School and Pro Vice-Chancellor (African Health) at the University of KwaZulu-Natal, Durban, South Africa

Awarded"For their discovery that antiretrovirals prevent sexual transmission of HIV, which laid the foundations for pre-exposure prophylaxis (PrEP), the HIV prevention strategy that is contributing to the reduction of HIV infection in Africa and around the world."

The Work: UNAIDS estimates that 37 million people were living with HIV and 1.8 million people acquired HIV in 2017. In Africa, which has over two thirds of all people with HIV, adolescent girls and young women have the highest rates of new HIV infections. ABC (Abstinence, Be faithful, and use Condoms) prevention messages have had little impact - due to gender power imbalances, young women are often unable to successfully negotiate condom use, insist on mutual monogamy, or convince their male partners to have an HIV test.

In responding to this crisis, Salim and Quarraisha Abdool Karim started investigating new HIV prevention technologies for women about 30 years ago. After two unsuccessful decades, their perseverance paid off when they provided proof-of-concept that antiretrovirals prevent sexually acquired HIV infection in women. Their ground-breaking CAPRISA 004 trial showed that tenofovir gel prevents both HIV infection and genital herpes. The finding was ranked inthe "Top 10 Scientific Breakthroughs of 2010" by the journal, Science. The finding was heralded by UNAIDS and the World Health Organization (WHO) as one of the most significant scientific breakthroughs in AIDS and provided the first evidence for what is today known as HIV pre-exposure prophylaxis (PrEP).

The Abdool Karims have also elucidated the evolving nature of the HIV epidemic in Africa, characterising the key social, behavioural and biological risk factors responsible for the disproportionately high HIV burden in young women. Their identification of the "Cycle of HIV Transmission", where teenage girls acquire HIV from men about 10 years older on average, has shaped UNAIDS policies on HIV prevention in Africa.

The impact: CAPRISA 004 and several clinical trials of oral tenofovir led tothe WHO recommending a daily tenofovir-containing pill for PrEP as a standard HIV prevention tool for all those at high risk a few years later. Several African countries are among the 68 countries across all continents that are currently making PrEP available for HIV prevention. The research undertaken in Africa by this South African couple has played a key role in shaping the local and global response to the HIV epidemic.

2020 Canada Gairdner Wightman AwardThe 2020 Canada Gairdner Wightman Award laureate is a Canadian scientist recognized for outstanding leadership in medicine and medical science throughout their career:

Dr. Guy Rouleau Director of the Montreal Neurological Institute-Hospital (The Neuro); Professor & Chair of the Department of Neurology and Neurosurgery, McGill University; Director of the Department of Neuroscience, McGill University Health Center

Awarded "For identifying and elucidating the genetic architecture of neurological and psychiatric diseases, including ALS, autism and schizophrenia, and his leadership in the field of Open Science."

The Work: Dr. Rouleau has identified over 20 genetic risk factors predisposing to a range of brain disorders, both neurological and psychiatric, involving either neurodevelopmental processes or degenerative events. He has defined a novel disease mechanism for diseases related to repeat expansions that are at play in some of the most severe neurodegenerative conditions. He has significantly contributed to the understanding of the role of de novo variants in autism and schizophrenia. In addition, he has made important advances for various neuropathies, in particular for amyotrophic lateral sclerosis (ALS) where he was involved in the identification of the most prevalent genetic risk factors -which in turn are now the core of innumerable ALS studies worldwide.

Dr. Rouleau has also played a pioneering role in the practice of Open Science (OS), transforming the Montreal Neurological Institute-Hospital (The Neuro) into the first OS institution in the world. The Neuro now uses OS principles to transform research and careand accelerate the development of new treatments for patients through Open Access, Open Data, Open Biobanking, Open Early Drug Discovery and non-restrictive intellectual property.

The Impact: The identification of genetic risk factors has a number of significant consequences. First, allowing for more accurate genetic counselling, which reduces the burden of disease to affected individuals, parents and society. A revealing case is Andermann syndrome, a severe neurodevelopmental and neurodegenerative condition that was once relatively common in the Saguenay-Lac-St-Jean region of Quebec. Now this disease has almost disappeared from that population. Second, identifying the causative gene allows the development of treatments. For instance, his earlier work on a form of ALS linked to the superoxide dismutase-1 gene (SOD1) opened up studies which are now the focal point of phase 2 clinical studies showing great promise.

Byactingasalivinglabforthelast coupleofyears,TheNeuroisspearheading the practice of OpenScience (OS).TheNeurois alsoengagingstakeholdersacross Canadawiththegoal of formalizinganational OSallianceforthe neurosciences.Dr.Rouleau'sworkinOScontributesfundamentallytothetransformationoftheveryecosystemofsciencebystimulatingnewthinkingandfosteringcommunitiesofsharing.InspiredbyTheNeuro'svision,theglobalsciencecommunityisreflecting oncurrentresearchconventionsandcollaborativeprojects,andthemomentumforOSisgainingafootholdinorganizationsandinstitutionsinallcornersoftheearth.

About the Gairdner Foundation:

The Gairdner Foundation was established in 1957 by Toronto stockbroker, James Gairdner to award annual prizes to scientists whose discoveries have had major impact on scientific progress and on human health. Since 1959 when the first awards were granted, 387scientists have received a Canada Gairdner Award and 92 to date have gone on to receive the Nobel Prize.The Canada Gairdner Awards promote a stronger culture of research and innovation across the country through our Outreach Programs including lectures and research symposia. The programs bring current and past laureates to a minimum of 15 universities across Canada to speak with faculty, trainees and high school students to inspire the next generation of researchers. Annual research symposia and public lectures are organized across Canada to provide Canadians access to leading science through Gairdner's convening power.

http://www.gairdner.org

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2020 Canada Gairdner Awards Recognize World-renowned Scientists for Transformative Contributions to Research That Impact Human Health - Benzinga

Today, we will see why Fate Therapeutics (FATE) is an attractive pick in March 2020.

Fate Therapeutics is a clinical-stage biopharmaceutical company focused on the development of next-generation cellular immunotherapies for cancer and immune disorders. The company has pioneered proprietary iPSC (induced pluripotent stem cell) platform technology to develop off-the-shelf cell-based cancer immunotherapy products. Current patient-derived autologous and allogeneic cell therapies suffer from drawbacks such as high costs, manufacturing complexity, product heterogeneity, and high turnaround time. These methods, including patient and donor-derived approaches to cell therapy, also require batch-to-batch sourcing and engineering of millions of primary cells.

Fate Therapeutics aims to be the game-changer in cell-based cancer immunotherapy space by enabling the development of off-the-shelf cell products derived from master cell lines. The company aims to develop less costly, homogenous, and multi-dose or multi-cycle cell therapies with small turnaround time. The resultant cell therapy products are expected to be well-defined and uniform in the composition and can be mass-produced at a significant scale in a cost-effective manner and can be delivered off-the-shelf for broad patient accessibility.

The company's cell therapy pipeline comprises immune-oncology programs including off-the-shelf NK- and T-cell product candidates derived from master iPSC lines, and immuno-regulatory programs, including product candidates to prevent life-threatening complications in patients undergoing hematopoietic cell transplantation and to promote immune tolerance in patients with autoimmune disease.

Human-induced Pluripotent Stem cells are generated by reprogramming adult somatic cells to a pluripotent state. Fibroblasts are the most commonly used primary somatic cell type for the generation of induced pluripotent stem cells. They are reprogrammed using retroviruses. Pluripotent cells are capable of differentiating in all cell types that make up the body.

A single human iPSC can potentially differentiate into more than 200 cell types and provides a renewable source for making cells.

NK (natural killer) cells are the body's first line of defense against tumors and various pathogens. Fate Therapeutics is leveraging its iPSC platform to produce off-the-shelf NK cell therapy products.

FT500 is Fate Therapeutics' first off-the-shelf iPSC-derived NK-cell product candidate. The FT500 study is an open-label, multi-dose Phase 1 clinical trial designed to evaluate FT500 for the treatment of advanced solid tumors.

The dose-escalation stage of the study was originally designed to assess the safety and tolerability of three once-weekly doses of FT500, without IL-2 cytokine support, as a monotherapy and in combination with one of three FDA-approved ICI (immune checkpoint inhibitor) therapies in patients that have failed prior ICI therapy.

Data for the first 12 patients in the Phase 1 study has demonstrated clean safety for the iPSC platform. The cutoff date considered was November 28, 2019. It was seen that there were no reported dose-limiting toxicities, no FT500 related Grade 3 or greater adverse events or serious adverse events, and no incidents of cytokine release syndrome, neurotoxicity, or graft-versus-host disease.

Further, the trial also involved the evaluation of a multi-dose treatment course consisting of outpatient lympho-conditioning followed by three once-weekly doses of FT500 over up to two 30-day treatment cycles. Here, based on patients' T-cell and antibody repertoire, no anti-product immune responses against FT500 were evident over the multi-dose treatment course.

A total of 62 doses of FT500 were administered to these 12 patients in a safe and well-tolerated manner. Initial clinical data thus provides strong evidence that multiple doses of iPSC-derived NK-cells can be delivered off-the-shelf without patient matching.

In December 2019, the company disclosed plans to amend the trial protocol by including IL-2 cytokine support with each dose of FT500 after completion of 300 million cells per dose cohort in the ICI combination arm. The company has commenced dose-expansion part of Phase 1 trial with 300 million cells per dose and is focusing on enrolling NSCLC patients who are refractory to or have relapsed following CBT. This tumor type is highly susceptible to NK-cell recognition and killing. The study is enrolling at three clinical sites in the U.S. Fate Therapeutics expects expansion data readout from the trial in the second half of 2020.

Fate Therapeutics is studying the second product candidate from iPSC product platform and off-the-shelf NK-cell cancer immunotherapy, FT516, in an open-label, multi-dose Phase 1 trial. This product has been engineered to augment antibody-dependent cellular cytotoxicity.

In December 2019, the company announced results for two patients dosed with FT516. FT516 was administered as a monotherapy to the first patient who was suffering from relapsed/refractory AML (acute myeloid leukemia). The company dosed FT516 in combination with rituximab to the second patient who was suffering from high-risk DLBCL (diffuse large B-cell lymphoma) and had relapsed after multiple rituximab combination regimens, autologous hematopoietic stem cell transplant, and CAR (chimeric antigen receptor) T-cell therapy. The patients had received a first treatment cycle consisting of outpatient lympho-conditioning, three once-weekly doses of FT516 and IL-2 to better promote NK-cell activity.

Initial clinical data based on bone marrow biopsy at day 42 demonstrated no morphologic evidence of leukemia. There was even evidence of hematopoietic recovery following the completion of the first FT516 treatment cycle in the AML patient. There was also no circulating leukemia cells in the patient's peripheral blood. The patient even reported the recovery of neutrophils without growth factor support. The data did not demonstrate dose-limiting toxicities, although serious adverse events were seen. Initial dose escalation data may be read out in the second half of 2020.

This initial clinical evidence highlights the high probability of engineered iPSC-derived NK-cells demonstrating anti-tumor activity in AML indication. Besides, there is a body of data that has demonstrated clinical proof-of-concept for donor-derived NK-cell therapy in relapsed refractory AML and relapsed refractory DLBCL.

In December 2019, FDA accepted FT516's second IND application for studying the product in combination with PDL1, PD1, EGFR and HER2-targeting monoclonal antibody therapies in solid tumor indications. Initially, the company plans to prioritize the combination of FT516 and avelumab in patients with advanced solid tumors who are refractory to or have relapsed following, at least one line of anti-PDL1 monoclonal antibody therapy. The company plans to initiate enrollment in a clinical trial for FT516 and avelumab in mid-2020.

Fate Therapeutics is studying off-the-shelf multi-antigen targeted CAR NK-cell product candidate, FT596, in solid tumor indications.

In December 2019, Fate Therapeutics reported favorable in vivo preclinical data for FT596.

Here, in humanized mouse models of lymphoma and leukemia, FT596's efficacy was comparable to that of primary CAR T-cells in promoting tumor clearance and extending survival. FT596 combined with rituximab also showed the enhanced killing of lymphoma cells in vivo as compared to rituximab alone. FT596 can thus emerge to be best-in-class off-the-shelf treatment in B-cell malignancies. Fate Therapeutics has started enrolling patients in the open-label Phase I study. Initial dose escalation data readout on FT596 is expected in the second half of 2020.

Fate Therapeutics has high hopes for FT596, considering that initial clinical data from a donor-derived CAR19 NK-cell program at MD Anderson, demonstrated a 73% overall response rate in patients with relapsed refractory non-Hodgkin's lymphoma and chronic lymphocytic leukemia with no major toxicities. Hence, while the efficacy seemed similar to CAR T therapy, the safety profile was differentiated in favor of CAR NK-cell therapies.

Although early, this data has highlighted CAR NK-cells' capacity to confer a high level of efficacy without the CAR-T cell therapy-related toxicities. Fate Therapeutics expects FT596 to effectively replace patient-specific and allogeneic CAR19 T-cell immunotherapies. The latter single-antigen specific and hence pose a risk of disease relapse due to antigen escape as well as cause significant toxicities due to off-target activity. FT596, on the other hand, has been engineered with three active anti-tumoral functional components.

Fate Therapeutics aims to be the first company to introduce off-the-shelf iPSC-derived CAR T-cell therapy to patients, FT819, by submitting IND in the second quarter of 2020. The company expects to file an IND application for off-the-shelf CRISPR-edited, iPSC-derived NK-cell product candidate, FT538, by early May 2020. The company has also planned IND submission for FT576 in the second half of 2020.

Although Fate Therapeutics is pioneering a revolutionary approach for mass production of off-shelf cell therapy products, its pipeline is very early stage. There has not been sufficient data from its clinical programs to make an informed estimate about the success probability of these programs. In this backdrop, the company is exposed to significant R&D failure risks. In case data readouts from FT500 and FT596 clinical programs do not match expectations, the company may witness increased share price volatility.

At the end of 2019, the company had cash worth $261 million on its balance sheet. The company spent cash worth $83.2 million on operating activities in 2019. This is a proxy for the 2019 cash burn rate. We assume that the annual cash burn rate in 2020 will be around $120 million, considering that three assets have entered in-human trials. Hence, the company seems to have cash that can sustain operations until the end of 2021. However, if cash is needed at a faster pace, the company may land up requiring more funds. This can lead to equity dilution.

According to finviz, the 12-month consensus target price of Fate Therapeutics is $37.94. On March 4, Citi analyst Yigal Nochomovitz reiterated the "Buy" rating and increased target price from $26 to $41. On March 4, Barclays analyst Peter Lawson also initiated coverage of Fate Therapeutics with an Overweight rating and $40 price target.

On March 3, BMO Capital analyst Do Kim raised the firm's price target on Fate Therapeutics to $28 from $22 and reiterated the "Market Perform" rating. On March 3, Guggenheim analyst Michael Schmidt reiterated the "Buy" rating and increased target price from $25 to $41. On March 3, Roth Capital analyst Tony Butler reiterated the "Neutral" rating but increased the target price from $20 to $30. On March 3, BTIG analyst Amanda Murphy reiterated the "Buy" rating and increased target price from $27 to $42. The analyst has also raised the estimated value of the company's iPSC platform from $740 million to $2.0 billion.

On March 3, Oppenheimer analyst Matthew Biegler reiterated the "Outperform" rating and increased the target price from $27 to $36. Piper Sandler analyst, Edward Tenthoff also reiterated the "Overweight" rating and raised the target price from $28 to $57.

In September 2019, Fate Therapeutics launched in-house GMP (Good Manufacturing Practices) manufacturing facility at headquarters in San Diego, California. This is custom designed to use clonal master iPSC lines as a renewable cell source for the consistent and scaled manufacture of off-the-shelf NK-cell and CAR T-cell products. The company has already produced hundreds of cryopreserved, infusion-ready doses of FT500, FT516, and FT596 at a low cost per dose. Currently stored in inventory, these doses are immediately available for use in the clinical settings.

The full control of cGMP production and the technical expertise to genetically engineer iPSCs and create qualified clonal master lines for clinical use implies that the company has operational expertise and redundancies required for the consistent cost-effective manufacturing and clinical supply of off-the-shelf cell products.

I believe that the 12-month target price of $30 fairly reflects the growth potential as well as risks associated with early-stage Fate Therapeutics. I consider this company to be a good pick for aggressive biotech investors with an investment horizon of at least one year.

Disclosure: I/we have no positions in any stocks mentioned, and no plans to initiate any positions within the next 72 hours. I wrote this article myself, and it expresses my own opinions. I am not receiving compensation for it (other than from Seeking Alpha). I have no business relationship with any company whose stock is mentioned in this article.

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Fate Therapeutics: Potential Catalysts Ahead - Seeking Alpha

Abstract

Mesenchymal stem cells (MSCs) encapsulation by three-dimensionally (3D) printed matrices were believed to provide a biomimetic microenvironment to drive differentiation into tissue-specific progeny, which made them a great therapeutic potential for regenerative medicine. Despite this potential, the underlying mechanisms of controlling cell fate in 3D microenvironments remained relatively unexplored. Here, we bioprinted a sweat gland (SG)like matrix to direct the conversion of MSC into functional SGs and facilitated SGs recovery in mice. By extracellular matrix differential protein expression analysis, we identified that CTHRC1 was a critical biochemical regulator for SG specification. Our findings showed that Hmox1 could respond to the 3D structure activation and also be involved in MSC differentiation. Using inhibition and activation assay, CTHRC1 and Hmox1 synergistically boosted SG gene expression profile. Together, these findings indicated that biochemical and structural cues served as two critical impacts of 3D-printed matrix on MSC fate decision into the glandular lineage and functional SG recovery.

Mesenchymal stem cells (MSCs) hold great promise for therapeutic tissue engineering and regenerative medicine, largely because of their capacity for self-renewal and multipotent properties (1). However, their uncertain fate has a major impact on their envisioned therapeutic use. Cell fate regulation requires specific transcription programs in response to environmental cues (2, 3). Once stem cells are removed from their microenvironment, their response to environmental cues, phenotype, and functionality could often be altered (4, 5). In contrast to growing information concerning transcriptional regulation, guidance from the extracellular matrix (ECM) governing MSC identity and fate determination is not well understood. It remains an active area of investigation and may provide previously unidentified avenues for MSC-based therapy.

Over the past decade, engineering three-dimensional (3D) ECM to direct MSC differentiation has demonstrated great potential of MSCs in regenerative medicine (6). 3D ECM has been found to be useful in providing both biochemical and biophysical cues and to stabilize newly formed tissues (7). Culturing cells in 3D ECM radically alters the interfacial interactions with the ECM as compared with 2D ECM, where cells are flattened and may lose their differentiated phenotype (8). However, one limitation of 3D materials as compared to 2D approaches was the lack of spatial control over chemistry with 3D materials. One possible solution to this limitation is 3D bioprinting, which could be used to design the custom scaffolds and tissues (9).

In contrast to traditional engineering techniques, 3D cell printing technology is especially advantageous because it can integrate multiple biophysical and biochemical cues spatially for cellular regulation and ensure complex structures with precise control and high reproducibility. In particular, for our final goal of clinical practice, extrusion-based bioprinting may be more appropriate for translational application. In addition, as a widely used bioink for extrusion bioprinting, alginate-based hydrogel could maintain stemness of MSC due to the bioinert property and improve biological activity and printability by combining gelatin (10).

Sweat glands (SGs) play a vital role in thermal regulation, and absent or malfunctioning SGs in a hot environment can lead to hyperthermia, stroke, and even death in mammals (11, 12). Each SG is a single tube consisting of a functionally distinctive duct and secretory portions. It has low regenerative potential in response to deep dermal injury, which poses a challenge for restitution of lost cells after wound (13). A major obstacle in SG regeneration, similar to the regeneration of most other glandular tissues, is the paucity of viable cells capable of regenerating multiple tissue phenotypes (12). Several reports have described SG regeneration in vitro; however, dynamic morphogenesis was not identified nor was the overall function of the formed tissues explored (1416). Recent advances in bioprinting and tissue engineering led to the complexities in the matrix design and fabrication with appropriate biochemical cues and biophysical guidance for SG regeneration (1719).

Here, we adopted 3D bioprinting technique to mimic the regenerative microenvironment that directed the specific SG differentiation of MSCs and ultimately guided the formation and function of glandular tissue. We used alginate/gelatin hydrogel as bioinks in this present study due to its good cytocompatibility, printability, and structural maintenance in long-time culture. Although the profound effects of ECM on cell differentiation was well recognized, the importance of biochemical and structural cues of 3D-printed matrix that determined the cell fate of MSCs remained unknown; thus, the present study demonstrated the role of 3D-printed matrix cues on cellular behavior and tissue morphogenesis and might help in developing strategies for MSC-based tissue regeneration or directing stem cell lineage specification by 3D bioprinting.

The procedure for printing the 3D MSC-loaded construct incorporating a specific SG ECM (mouse plantar region dermis, PD) was shown schematically in Fig. 1A. A 3D cellular construct with cross section 30 mm 30 mm and height of 3 mm was fabricated by using the optimized process parameter (20). The 3D construct demonstrated a macroporous grid structure with hydrogel fibers evenly distributed according to the computer design. Both the width of the fibers and the gap between the fibers were homogeneous, and MSCs were embedded uniformly in the hydrogel matrix fibers to result in a specific 3D microenvironment. (Fig. 1B).

(A) Schematic description of the approach. (B) Full view of the cellular construct and representative microscopic and fluorescent images and the quantitative parameters of 3D-printed construct (scale bars, 200 m). Photo credit: Bin Yao, Wound Healing and Cell Biology Laboratory, Institute of Basic Medical Sciences, General Hospital of PLA. (C) Representative microscopy images of cell aggregates and tissue morphology at 3, 7, and 14 days of culture (scale bars, 50 m) and scanning electron microscopy (sem) images of 3D structure (scale bars, 20 m). PD+/PD, 3D construct with and without PD. (D) DNA contents, collagen, and GAGs of native tissue and PD. (E) Proliferating cells were detected through Ki67 stain at 3, 7, and 14 days of culture. (F) Live/dead assay show cell viability at days 3, 7, and 14. *P < 0.05.

During the maintenance of constructs for stem cell expansion, MSCs proliferated to form aggregates of cells but self-assembled to an SG-like structure only with PD administration (Fig. 1C and fig. S1, A to C). We carried out DNA quantification assay to evaluate the cellular content in PD and found the cellular matrix with up to 90% reduction, only 3.4 0.7 ng of DNA per milligram tissue remaining in the ECM. We also estimated the proportions of collagen and glycosaminoglycans (GAGs) in ECM through hydroxyproline assay and dimethylmethylene blue assay, the collagen contents could increase to 112.6 11.3%, and GAGs were well retained to 81 9.6% (Fig. 1D). Encapsulated cells were viable, with negligible cell death apparent during extrusion and ink gelation by ionic cross-linking, persisting through extended culture in excess of 14 days. The fluorescence intensity of Ki67 of MSCs cultured in 2D condition decreased from days 3 (152.7 13.4) to 14 (29.4 12.9), while maintaining higher intensity of MSCs in 3D construct (such as 211.8 19.4 of PD+3D group and 209.1 22.1 of PD3D group at day 14). And the cell viability in 3D construct was found to be sufficiently high (>80%) when examined on days 3, 7, and 14. The phenomenon of cell aggregate formation and increased cell proliferation implied the excellent cell compatibility of the hydrogel-based construct and promotion of tissue development of 3D architectural guides, which did not depend on the presence or absence of PD (Fig. 1, E and F).

The capability of 3D-printed construct with PD directing MSC to SGs in vitro was investigated. The 3D construct was dissolved, and cells were isolated at days 3, 7, and 14 for transcriptional analysis. Expression of the SG markers K8 and K18 was higher from the 3D construct with (3D/PD+) than without PD (3D/PD); K8 and K18 expression in the 3D/PD construct was similar to with control that MSCs cultured in 2D condition, which implied the key role of PD in SG specification. As compared with the 2D culture condition, 3D administration (PD+) up-regulated SG markers, which indicated that the 3D structure synergistically boosted the MSC differentiation (Fig. 2A).

(A) Transcriptional expression of K8, K18, Fxyd2, Aqp5, and ATP1a1 in 3D-bioprinted cells with and without PD in days 3, 7, and 14 culture by quantitative real-time polymerase chain reaction (qRT-PCR). Data are means SEM. (B) Comparison of SG-specific markers K8 and K18 in 3D-bioprinted cells with and without PD (K8 and K18, red; DAPI, blue; scale bars, 50 m). (C and D) Comparison of SG secretion-related markers ATP1a1 (C) and Ca2+ (D) in 3D-bioprinted cells with and without PD [ATP1a1 and Ca2+, red; 4,6-diamidino-2-phenylindole (DAPI), blue; scale bars, 50 m].

In addition, we tested secretion-related genes to evaluate the function of induced SG cells (iSGCs). Although levels of the ion channel factors of Fxyd2 and ATP1a1 were increased notably in 2D culture with PD and ATP1a1 up-regulated in the 3D/PD construct, all the secretory genes of Fxyd2, ATP1a1, and water transporter Aqp5 showed the highest expression level in the 3D/PD+ construct (Fig. 2A). Considering the remarkable impact, further analysis focused on 3D constructs.

Immunofluorescence staining confirmed the progression of MSC differentiation. At day 7, cells in the 3D/PD+ construct began to express K8 and K18, which was increased at day 14, whereas cells in the 3D/PD construct did not express K8 and K18 all the time (Fig. 2B and fig. S2A). However, the expression of ATP1a1 (ATPase Na+/K+ transporting subunit alpha 1) and free Ca2+ concentration did not differ between cells in the 3D/PD+ and 3D/PD constructs (Fig. 2, C and D). By placing MSCs in such a 3D environment, secretion might be stimulated by rapid cell aggregation without the need for SG lineage differentiation. Cell aggregationimproved secretion might be due to the benefit of cell-cell contact (fig. S2B) (21, 22).

To map the cell fate changes during the differentiation between MSCs and SG cells, we monitored the mRNA levels of epithelial markers such as E-cadherin, occludin, Id2, and Mgat3 and mesenchymal markers N-cadherin, vimentin, Twist1, and Zeb2. The cells transitioned from a mesenchymal status to a typical epithelial-like status accompanied by mesenchymal-epithelial transition (MET), then epithelial-mesenchymal transition (EMT) occurred during the further differentiation of epithelial lineages to SG cells (fig. S3A). In addition, MET-related genes were dynamically regulated during the SG differentiation of MSCs. For example, the mesenchymal markers N-cadherin and vimentin were down-regulated from days 1 to 7, which suggested cells losing their mesenchymal phenotype, then were gradually up-regulated from days 7 to 10 in their response to the SG phenotype and decreased at day 14. The epithelial markers E-cadherin and occludin showed an opposite expression pattern: up-regulated from days 1 to 5, then down-regulated from days 7 to 10 and up-regulated again at day 14. The mesenchymal transcriptional factors ZEB2 and Twist1 and epithelial transcriptional factors Id2 and Mgat3 were also dynamically regulated.

We further analyzed the expression of these genes at the protein level by immunofluorescence staining (figs. S3B and S4). N-cadherin was down-regulated from days 3 to 7 and reestablished at day 14, whereas E-cadherin level was increased from days 3 to 7 and down-regulated at day 14. Together, these results indicated that a sequential and dynamic MET-EMT process underlie the differentiation of MSCs to an SG phenotype, perhaps driving differentiation more efficiently (23). However, the occurrence of the MET-EMT process did not depend on the presence of PD. Thus, a 3D structural factor might also participate in the MSC-specific differentiation (fig. S3C).

To investigate the underlying mechanism of biochemical cues in lineage-specific cell fate, we used quantitative proteomics analysis to screen the ECM factors differentially expressed between PD and dorsal region dermis (DD) because mice had eccrine SGs exclusively present in the pads of their paws, and the trunk skin lacks SGs. In total, quantitative proteomics analyses showed higher expression levels of 291 proteins in PD than DD. Overall, 66 were ECM factors: 23 were significantly up-regulated (>2-fold change in expression). We initially determined the level of proteins with the most significant difference after removing keratins and fibrin: collagen triple helix repeat containing 1 (CTHRC1) and thrombospondin 1 (TSP1) (fig. S5). Western blotting was performed to further confirm the expression level of CTHRC1 and TSP1, and we then confirmed that immunofluorescence staining at different developmental stages in mice revealed increased expression of CTHRC1 in PD with SG development but only slight expression in DD at postnatal day 28, while TSP1 was continuously expressed in DD and PD during development (Fig. 3, A to C). Therefore, TSP1 was required for the lineage-specific function during the differentiation in mice but was not dispensable for SG development.

(A and B) Differential expression of CTHRC1 and TSP1in PD and back dermis (DD) ECM of mice by proteomics analysis (A) and Western blotting (B). (C) CTHRC1 and TSP1 expression in back and plantar skin of mice at different developmental times. (Cthrc1/TSP1, red; DAPI, blue; scale bars, 50 m).

According to previous results of the changes of SG markers, 3D structure and PD were both critical to SG fate. Then, we focused on elucidating the mechanisms that underlie the significant differences observed in 2D and 3D conditions with or without PD treatment. To this end, we performed transcriptomics analysis of MSCs, MSCs treated with PD, MSCs cultured in 3D construct, and MSC cultured in 3D construct with PD after 3-day treatment. We noted that the expression profiles of MSCs treated with 3D, PD, or 3D/PD were distinct from the profiles of MSCs (Fig. 4A). Through Gene Ontology (GO) enrichment analysis of differentially expressed genes, it was shown that PD treatment in 2D condition induced up-regulation of ECM and inflammatory response term, and the top GO term for MSCs in 3D construct was ECM organization and extracellular structure organization. However, for the MSCs with 3D/PD treatment, we found very significant overrepresentation of GO term related to branching morphogenesis of an epithelial tube and morphogenesis of a branching structure, which suggested that 3D structure cues and biochemical cues synergistically initiate the branching of gland lineage (fig S6). Heat maps of differentially expressed ECM organization, cell division, gland morphogenesis, and branch morphogenesis-associated genes were shown in fig. S7. To find the specific genes response to 3D structure cues facilitating MSC reprogramming, we analyzed the differentially expressed genes of four groups of cells (Fig. 4B). The expression of Vwa1, Vsig1, and Hmox1 were only up-regulated with 3D structure stimulation, especially the expression of Hmox1 showed a most significant increase and even showed a higher expression addition with PD, which implied that Hmox1 might be the transcriptional driver of MSC differentiation response to 3D structure cues. Differential expression of several genes was confirmed by quantitative polymerase chain reaction (qPCR): Mmp9, Ptges, and Il10 were up-regulated in all the treated groups. Likewise, genes involving gland morphogenesis and branch morphogenesis such as Bmp2, Tgm2, and Sox9 showed higher expression in 3D/PD-treated group. Bmp2 was up-regulated only in 3D/PD-treated group, combined with the results of GO analysis, we assumed that Bmp2 initiated SG fate through inducing branch morphogenesis and gland differentiation (Fig. 4C).

(A) Gene expression file of four groups of cells (R2DC, MSCs; R2DT, MSC with PD treatment; R3DC, MSC cultured in 3D construct; and R3DT, MSC treated with 3D/PD). (B) Up-regulated genes after treatment (2DC, MSCs; 2DT, MSC with PD treatment; 3DC, MSC cultured in 3D construct; and 3DT, MSC treated with 3D/PD). (C) Differentially expressed genes were further validated by RT-PCR analysis. [For all RT-PCR analyses, gene expression was normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) with 40 cycles, data are represented as the means SEM, and n = 3].

To validate the role of HMOX1 and CTHRC1 in the differentiation of MSCs to SG lineages, we analyzed the gene expression of Bmp2 by regulating the expression of Hmox1 and CTHRC1 based on the 3D/PD-treated MSCs. The effects of caffeic acid phenethyl ester (CAPE) and tin protoporphyrin IX dichloride (Snpp) on the expression of Hmox1 were evaluated by quantitative real-time (qRT)PCR. Hmox1 expression was significantly activated by CAPE and reduced by Snpp. Concentration of CTHRC1 was increased with recombinant CTHRC1 and decreased with CTHRC1 antibody. That is, it was negligible of the effects of activator and inhibitor of Hmox1 and CTHRC1 on cell proliferation (fig. S8, A and B). Hmox1 inhibition or CTHRC1 neutralization could significantly reduce the expression of Bmp2, while Hmox1 activation or increased CTHRC1 both activated Bmp2 expression. Furthermore, Bmp2 showed highest expression by up-regulation of Hmox1 and CTHRC1 simultaneously and sharply decreased with down-regulation of Hmox1 and CTHRC1 at the same time (Fig. 5A). Immunofluorescent staining revealed that the expression of bone morphogenetic protein 2 (BMP2) at the translational level with CTHRC1 and Hmox1 regulation showed a similar trend with transcriptional changes (Fig. 5B). Likewise, the expression of K8 and K18 at transcriptional and translational level changed similarly with CTHRC1 and Hmox1 regulation (fig. S9, A and B). These results suggested that CTHRC1 and Hmox1 played an essential role in SG fate separately, and they synergistically induced SG direction from MSCs (Fig. 5C).

(A and B) Transcriptional analysis (A) and translational analysis (PD, MSCs; PD+, MSCs with 3D/PD treatment; CAPE, MSCs treated with 3D/PD and Hmox1 activator; Snpp, MSCs treated with 3D/PD and Hmox1 inhibitor; Cthrc1, MSCs treated with 3D/PD and recombinant CTHRC1; anti, MSCs treated with 3D/PD and CTHRC1 antibody: +/+, MSCs treated with 3D/PD and Hmox1 activator and recombinant CTHRC1; and /, MSCs treated with 3D/PD and Hmox1 inhibitor and CTHRC1 antibody. Data are represented as the means SEM and n = 3) (B) of bmp2 with regulation of CTHRC1 and Hmox1. (C) The graphic illustration of 3D-bioprinted matrix directed MSC differentiation. CTHRC1 is the main biochemical cues during SG development, and structural cues up-regulated the expression of Hmox1 synergistically initiated branching morphogenesis of SG. *P < 0.05.

Next, we sought to assess the repair capacity of iSGCs for in vivo implications, the 3D-printed construct with green fluorescent protein (GFP)labeled MSCs was transplanted in burned paws of mice (Fig. 6A). We measured the SG repair effects by iodine/starch-based sweat test at day 14. Only mice with 3D/PD treatment showed black dots on foot pads (representing sweating), and the number increased within 10 min; however, no black dots were observed on untreated and single MSC-transplanted mouse foot pads even after 15 min (Fig. 6B). Likewise, hematoxylin and eosin staining analysis revealed SG regeneration in 3D/PD-treated mice (Fig. 6C). GFP-positive cells were characterized as secretory lumen expressing K8, K18, and K19. Of note, the GFP-positive cells were highly distributed in K14-positive myoepithelial cells of SGs but were absent in K14-positive repaired epidermal wounds (Fig. 6, D and E). Thus, differentiated MSCs enabled directed restitution of damaged SG tissues both at the morphological and functional level.

(A) Schematic illustration of approaches for engineering iSGCs and transplantation. (B) Sweat test of mice treated with different cells. Photo credit: Bin Yao, Wound Healing and Cell Biology Laboratory, Institute of Basic Medical Sciences, General Hospital of PLA. (C) Histology of plantar region without treatment and transplantation of MSCs and iSGCs (scale bars, 200 m). (D) Involvement of GFP-labeled iSGCs in directed regeneration of SG tissue in thermal-injured mouse model (K14, red; GFP, green; DAPI, blue; scale bar, 200 m). (E) SG-specific markers K14, K19, K8, and K18 detected in regenerated SG tissue (arrows). (K14, K19, K8, and K18, red; GFP, green; scale bars, 50 m).

A potential gap in MSC-based therapy still exists between current understandings of MSC performance in vivo in their microenvironment and their intractability outside of that microenvironment (24). To regulate MSCs differentiation into the right phenotype, an appropriate microenvironment should be created in a precisely controlled spatial and temporal manner (25). Recent advances in innovative technologies such as bioprinting have enabled the complexities in the matrix design and fabrication of regenerative microenvironments (26). Our findings demonstrated that directed differentiation of MSCs into SGs in a 3D-printed matrix both in vitro and in vivo was feasible. In contrast to conventional tissue-engineering strategies of SG regeneration, the present 3D-printing approach for SG regeneration with overall morphology and function offered a rapid and accurate approach that may represent a ready-to-use therapeutic tool.

Furthermore, bioprinting MSCs successfully repaired the damaged SG in vivo, suggesting that it can improve the regenerative potential of exogenous differentiated MSCs, thereby leading to translational applications. Notably, the GFP-labeled MSC-derived glandular cells were highly distributed in K14-positive myoepithelial cells of newly formed SGs but were absent in K14-positive repaired epidermal wounds. Compared with no black dots were observed on single MSC-transplanted mouse foot pads, the black dots (representing sweating function) can be observed throughout the entire examination period, and the number increased within 10 min on MSC-bioprinted mouse foot pads. Thus, differentiated MSCs by 3D bioprinting enabled exclusive restitution of damaged SG tissues morphologically and functionally.

Although several studies indicated that engineering 3D microenvironments enabled better control of stem cell fates and effective regeneration of functional tissues (2730), there were no studies concerning the establishment of 3D-bioprinted microenvironments that can preferentially induce MSCs differentiating into glandular cells with multiple tissue phenotypes and overall functional tissue. To find an optimal microenvironment for promoting MSC differentiation into specialized progeny, biochemical properties are considered as the first parameter to ensure SG specification. In this study, we used mouse PD as the main composition of a tissue-specific ECM. As expected, this 3D-printed PD+ microenvironment drove the MSC fate decision to enhance the SG phenotypic profile of the differentiated cells. By ECM differential protein expression analysis, we identified that CTHRC1 was a critical biochemical regulator of 3D-printed matrix for SG specification. TSP1 was required for the lineage-specific function during the differentiation in mice but was not dispensable for SG development. Thus, we identified CTHRC1 as a specific factor during SG development. To our knowledge, this is the first demonstration of CTHRC1 involvement in dictating MSC differentiation to SG, highlighting a potential therapeutic tool for SG injury.

The 3D-printed matrix also provided architectural guides for further SG morphogenesis. Our results clearly show that the 3D spatial dimensionality allows for better cell proliferation and aggregation and affect the characteristics of phenotypic marker expression. Notably, the importance of 3D structural cues on MSC differentiation was further proved by MET-EMT process during differentiation, where the influences did not depend on the presence of biochemical cues. To fully elucidate the underlying mechanisms, we first examined how 3D structure regulating stem cell fate choices. According to our data, Hmox1 is highly up-regulated in 3D construct, which were supposed to response to hypoxia, with a previously documented role in MSC differentiation (31, 32). It is suggested that 3D microenvironment induced rapid cell aggregation leading to hypoxia and then activated the expression of Hmox1.

Through regulation of the expression of Hmox1 and addition or of CTHRC1 in the matrix, we confirmed that each of them is critical for SG reprogramming, respectively. Thus, biochemical and structural cues of 3D-printed matrix synergistically creating a microenvironment could enhance the accuracy and efficiency of MSC differentiation, thereby leading to resulting SG formation. Although we further need a more extensive study examining the role of other multiple cues and their possible overlap function in regulating MSC differentiation, our findings suggest that CTHRC1 and Hmox1 provide important signals that cooperatively modulate MSC lineage specification toward sweat glandular lineage. The 3D structure combined with PD stimulated the GO functional item of branch morphogenesis and gland formation, which might be induce by up-regulation of Bmp2 based on the verification of qPCR results. Although our results could not rule out the involvement of other factors and their possible overlapping role in regulating MSC lineage specification toward SGs, our findings together with several literatures suggested that BMP2 plays a critical role in inducing branch morphogenesis and gland formation (3335).

In summary, our findings represented a novel strategy of directing MSC differentiation for functional SG regeneration by using 3D bioprinting and pave the way for a potential therapeutic tool for other complex glandular tissues as well as further investigation into directed differentiation in 3D conditions. Specifically, we showed that biochemical and structural cues of 3D-printed matrix synergistically direct MSC differentiation, and our results highlighted the importance of 3D-printed matrix cues as regulators of MSC fate decisions. This avenue opens up the intriguing possibility of shifting from genetic to microenvironmental manipulations of cell fate, which would be of particular interest for clinical applications of MSC-based therapies.

The main aim and design of the study was first to determine whether by using 3D-printed microenvironments, MSCs can be directed to differentiate and regenerate SGs both morphologically and functionally. Then, to investigate the underlying molecular mechanism of biochemical and structural cues of 3D-printed matrix involved in MSCs reprogramming. The primary aims of the study design were as follows: (i) cell aggregation and proliferation in a 3D-bioprinted construct; (ii) differentiation of MSCs at the cellular phenotype and functional levels in the 3D-bioprinted construct; (iii) the MET-EMT process during differentiation; (iv) differential protein expression of the SG niche in mice; (v) differential genes expression of MSCs in 3D-bioprinted construct; (vi) the key role of CTHRC1 and HMOX1 in MSCs reprogramming to SGCs; and (vii) functional properties of regenerated SG in vivo.

Gelatin (Sigma-Aldrich, USA) and sodium alginate (Sigma-Aldrich, USA) were dissolved in phosphate-buffered saline (PBS) at 15 and 1% (w/v), respectively. Both solutions were sterilized under 70C for 30 min three times at an interval of 30 min. The sterilized solutions were packed into 50-ml centrifuge tubes, stored at 4C, and incubated at 37C before use.

From wild-type C57/B16 mice (Huafukang Co., Beijing) aged 5 days old, dermal homogenates were prepared by homogenizing freshly collected hairless mouse PD with isotonic phosphate buffer (pH 7.4) for 20 min in an ice bath to obtain 25% (w/v) tissue suspension. The supernatant was obtained after centrifugation at 4C for 20 min at 10,000g. The DNA content was determined using Hoechst 33258 assay (Beyotime, Beijing). The fluorescence intensity was measured to assess the amount of remaining DNA within the decellularized ECMs and the native tissue using a fluorescence spectrophotometer (Thermo Scientific, Evolution 260 Bio, USA). The GAGs content was estimated via 1,9-dimethylmethylene blue solution staining. The absorbance was measured with microplate reader at wavelength of 492 nm. The standard curve was made using chondroitin sulfate A. The total COL (Collagen) content was determined via hydroxyproline assay. The absorbance of the samples was measured at 550 nm and quantified by referring to a standard curve made with hydroxyproline.

MSCs were bioprinted with matrix materials by using an extrusion-based 3D bioprinter (Regenovo Co., Bio-Architect PRO, Hangzhou). Briefly, 10 ml of gelatin solution (10% w/v) and 5 ml of alginate solution (2% w/v) were warmed under 37C for 20 min, gently mixed as bioink and used within 30 min. MSCs were collected from 100-mm dishes, dispersed into single cells, and 200 l of cell suspension was gently mixed with matrix material under room temperature with cell density 1 million ml1. PD (58 g/ml) was then gently mixed with bioink. Petri dishes at 60 mm were used as collecting plates in the 3D bioprinting process. Within a temperature-controlled chamber of the bioprinter, with temperature set within the gelation region of gelatin, the mixture of MSCs and matrix materials was bioprinted into a cylindrical construct layer by layer. The nozzle-insulation temperature and printing chamber temperature were set at 18 and 10C, respectively; nozzles with an inner diameter of 260 m were chosen for printing. The diameter of the cylindrical construct was 30 mm, with six layers in height. After the temperature-controlled bioprinting process, the printed 3D constructs were immersed in 100-mM calcium chloride (Sigma-Aldrich, USA) for 3 min for cross-linking, then washed with Dulbeccos modified Eagle medium (DMEM) (Gibco, USA) medium for three times. The whole printing process was finished in 10 min. The 3D cross-linked construct was cultured in DMEM in an atmosphere of 5% CO2 at 37C. The culture medium was changed to SG medium [contains 50% DMEM (Gibco, New York, NY) and 50% F12 (Gibco) supplemented with 5% fetal calf serum (Gibco), 1 ml/100 ml penicillin-streptomycin solution, 2 ng/ml liothyronine sodium (Gibco), 0.4 g/ml hydrocortisone succinate (Gibco), 10 ng/ml epidermal growth factor (PeproTech, Rocky Hill, NJ), and 1 ml/100 ml insulin-transferrin-selenium (Gibco)] 2 days later. The cell morphology was examined and recorded under an optical microscope (Olympus, CX40, Japan).

Fluorescent live/dead staining was used to determine cell viability in the 3D cell-loaded constructs according to the manufacturers instructions (Sigma-Aldrich, USA). Briefly, samples were gently washed in PBS three times. An amount of 1 M calcein acetoxymethyl (calcein AM) ester (Sigma-Aldrich, USA) and 2 M propidium iodide (Sigma-Aldrich, USA) was used to stain live cells (green) and dead cells (red) for 15 min while avoiding light. A laser scanning confocal microscopy system (Leica, TCSSP8, Germany) was used for image acquisition.

The cell-printed structure was harvested and fixed with a solution of 4% paraformaldehyde. The structure was embedded in optimal cutting temperature (OCT) compound (Sigma-Aldrich, USA) and sectioned 10-mm thick by using a cryotome (Leica, CM1950, Germany). The sliced samples were washed repeatedly with PBS solution to remove OCT compound and then permeabilized with a solution of 0.1% Triton X-100 (Sigma-Aldrich, USA) in PBS for 5 min. To reduce nonspecific background, sections were treated with 0.2% bovine serum albumin (Sigma-Aldrich, USA) solution in PBS for 20 min. To visualize iSGCs, sections were incubated with primary antibody overnight at 4C for anti-K8 (1:300), anti-K14 (1:300), anti-K18 (1:300), anti-K19 (1:300), anti-ATP1a1 (1:300), anti-Ki67 (1:300), antiN-cadherin (1:300), antiE-cadherin (1:300), anti-CTHRC1 (1:300), or anti-TSP1 (1:300; all Abcam, UK) and then incubated with secondary antibody for 2 hours at room temperature: Alexa Fluor 594 goat anti-rabbit (1:300), fluorescein isothiocyanate (FITC) goat anti-rabbit (1:300), FITC goat anti-mouse (1:300), or Alexa Fluor 594 goat anti-mouse (1:300; all Invitrogen, CA). Sections were also stained with 4,6-diamidino-2-phenylindole (Beyotime, Beijing) for 15 min. Stained samples were visualized, and images were captured under a confocal microscope.

To harvest the cells in the construct, the 3D constructs were dissolved by adding 55 mM sodium citrate and 20 mM EDTA (Sigma-Aldrich, USA) in 150 mM sodium chloride (Sigma-Aldrich, USA) for 5 min while gently shaking the petri dish for better dissolving. After transfer to 15-ml centrifuge tubes, the cell suspensions were centrifuged at 200 rpm for 3 min, and the supernatant liquid was removed to harvest cells for further analysis.

Total RNA was isolated from cells by using TRIzol reagent (Invitrogen, USA) following the manufacturers protocol. RNA concentration was measured by using a NanoPhotometer (Implen GmbH, P-330-31, Germany). Reverse transcription involved use of a complementary DNA synthesis kit (Takara, China). Gene expression was analyzed quantitatively by using SYBR green with the 7500 Real-Time PCR System (Takara, China). The primers and probes for genes were designed on the basis of published gene sequences (table S1) (National Center for Biotechnology Information and PubMed). The expression of each gene was normalized to that for glyceraldehyde-3-phosphate dehydrogenase and analyzed by the 2-CT method. Each sample was assessed in triplicate.

The culture medium was changed to SG medium with 2 mM CaCl2 for at least 24 hours, and cells were loaded with fluo-3/AM (Invitrogen, CA) at a final concentration of 5 M for 30 min at room temperature. After three washes with calcium-free PBS, 10 M acetylcholine (Sigma-Aldrich, USA) was added to cells. The change in the Fluo 3 fluorescent signal was recorded under a laser scanning confocal microscopy.

Cell proliferation was evaluated through CCK-8 (Cell counting kit-8) assay. Briefly, cells were seeded in 96-well plates at the appropriate concentration and cultured at 37C in an incubator for 4 hours. When cells were adhered, 10 l of CCK-8 working buffer was added into the 96-well plates and incubated at 37C for 1 hour. Absorbance at 450 nm was measured with a microplate reader (Tecan, SPARK 10M, Austria).

Proteomics of mouse PD and DD involved use of isobaric tags for relative and absolute quantification (iTRAQ) in BGI Company, with differentially expressed proteins detected in PD versus DD. Twofold greater difference in expression was considered significant for further study.

Tissues were grinded and lysed in radioimmunoprecipitation assay buffer (Beyotime, Nanjing). Proteins were separated by 12% SDSpolyacrylamide gel electrophoresis and transferred to a methanol-activated polyvinylidene difluoride membrane (GE Healthcare, USA). The membrane was blocked for 1 hour in PBS with Tween 20 containing 5% bovine serum albumin (Sigma-Aldrich, USA) and probed with the antibodies anti-CTHRC1 (1:1000) and anti-TSP1 (1:1000; both Abcam, UK) overnight at 4C. After 2 hours of incubation with goat anti-rabbit horseradish peroxidaseconjugated secondary antibody (Santa Cruz Biotechnology, CA), the protein bands were detected by using luminal reagent (GE Healthcare, ImageQuant LAS 4000, USA).

Total RNA was prepared with TRIzol (Invitrogen), and RNA sequencing was performed using HiSeq 2500 (Illumina). Genes with false discovery rate < 0.05, fold difference > 2.0, and mean log intensity > 2.0 were considered to be significant.

CAPE or Snpp was gently mixed with bioink at a concentration of 10 M. Physiological concentration of CTHRC1 was measured by enzyme linked immunosorbent assay (ELISA) (80 ng/ml), and then recombinant CTHRC1 or CTHRC1 antibody was added into the bioink at a concentration of 0.4 g/ml. The effect of inhibitor and activator was estimated by qRT-PCR or ELISA.

Mice were anesthetized with pentobarbital (100 mg/kg) and received subcutaneous buprenorphine (0.1 mg/kg) preoperatively. Full-thickness scald injuries were created on paw pads with soldering station (Weller, WSD81, Germany). Mice recovered in clean cages with paper bedding to prevent irritation or infection. Mice were monitored daily and euthanized at 30 days after wounding. Mice were maintained in an Association for Assessment and Accreditation of Laboratory Animal Careaccredited animal facility, and procedures were performed with Institutional Animal Care and Use Committeeapproved protocols.

MSCs in 3D-printed constructs with PD were cultured with DMEM for 2 days and then replaced with SG medium. The SG medium was changed every 2 days, and cells were harvested on day 12. The K18+ iSGCs were sorting through flow cytometry and injected into the paw pads (1 106 cells/50 l) of the mouse burn model by using Microliter syringes (Hamilton, 7655-01, USA). Then, mice were euthanized after 14 days; feet were excised and fixed with 10% formalin (Sigma-Aldrich, USA) overnight for paraffin sections and immunohistological analysis.

The foot pads of anesthetized treated mice were first painted with 2% (w/v) iodine/ethanol solution then with starch/castor oil solution (1 g/ml) (Sigma-Aldrich, USA). After drying, 50 l of 100 M acetylcholine (Sigma-Aldrich, USA) was injected subcutaneously into paws of mice. Pictures of the mouse foot pads were taken after 5, 10, and 15 min.

All data were presented as means SEM. Statistical analyses were performed using GraphPad Prism7 statistical software (GraphPad, USA). Significant differences were calculated by analysis of variance (ANOVA), followed by the Bonferroni test when performing multiple comparisons between groups. P < 0.05 was considered as a statistically significant difference.

Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/10/eaaz1094/DC1

Fig. S1. Biocompatibility of 3D-bioprinted construct and cellular morphology in 2D monolayer culture.

Fig. S2. Expression of SG-specific and secretion-related markers in MSCs and SG cells in vitro.

Fig. S3. Transcriptional and translational expression of epithelial and mesenchymal markers in 3D-bioprinted cells with and without PD.

Fig. S4. Expression of N- and E-cadherin in MSCs and SG cells in 2D monolayer culture.

Fig. S5. Proteomic microarray assay of differential gene expression between PD and DD ECM in postnatal mice.

Fig. S6. GO term analysis of differentially expressed pathways.

Fig. S7. Heat maps illustrating differential expression of genes implicated in ECM organization, cell division, and gland and branch morphogenesis.

Fig. S8. The expression of Hmox1 and the concentration of CTHRC1 on treatment and the related effects on cell proliferation.

Fig. S9. The expression of K8 and K18 with Hmox1 and CTHRC1 regulation.

Table S1. Primers for qRT-PCR of all the genes.

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.

Acknowledgments: Funding: This study was supported in part by the National Nature Science Foundation of China (81571909, 81701906, 81830064, and 81721092), the National Key Research Development Plan (2017YFC1103300), Military Logistics Research Key Project (AWS17J005), and Fostering Funds of Chinese PLA General Hospital for National Distinguished Young Scholar Science Fund (2017-JQPY-002). Author contributions: B.Y. and S.H. were responsible for the design and primary technical process, conducted the experiments, collected and analyzed data, and wrote the manuscript. Y.W. and R.W. helped perform the main experiments. Y.Z. and T.H. participated in the 3D printing. W.S. and Z.L. participated in cell experiments and postexamination. S.H. and X.F. collectively oversaw the collection of data and data interpretation and revised the manuscript. Competing interests: The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.

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Biochemical and structural cues of 3D-printed matrix synergistically direct MSC differentiation for functional sweat gland regeneration - Science...

The challenges of gene and cell therapists can be divided into three broad categories based on disease, development of therapy, and funding.

Challenges based on the disease characteristics: Disease symptoms of most genetic diseases, such as Fabrys, hemophilia, cystic fibrosis, muscular dystrophy, Huntingtons, and lysosomal storage diseases are caused by distinct mutations in single genes. Other diseases with a hereditary predisposition, such as Parkinsons disease, Alzheimers disease, cancer, and dystonia may be caused by variations/mutations in several different genes combined with environmental causes. Note that there are many susceptible genes and additional mutations yet to be discovered. Gene replacement therapy for single gene defects is the most conceptually straightforward. However, even then the gene therapy agent may not equally reduce symptoms in patients with the same disease caused by different mutations, and even the samemutationcan be associated with different degrees of disease severity. Gene therapists often screen their patients to determine the type of mutation causing the disease before enrollment into a clinical trial.

The mutated gene may cause symptoms in more than one cell type. Cystic fibrosis, for example, affects lung cells and the digestive tract, so the gene therapy agent may need to replace the defective gene or compensate for its consequences in more than one tissue for maximum benefit. Alternatively, cell therapy can utilizestem cellswith the potential to mature into the multiple cell types to replace defective cells in different tissues.

In diseases like muscular dystrophy, for example, the high number of cells in muscles throughout the body that need to be corrected in order to substantially improve the symptoms makes delivery of genes and cells a challenging problem.

Some diseases, like cancer, are caused by mutations in multiple genes. Although different types of cancers have some common mutations, every tumor from a single type of cancer does not contain the same mutations. This phenomenon complicates the choice of a single gene therapy tactic and has led to the use of combination therapies and cell elimination strategies. For more information on gene and cell therapy strategies to treat cancer, please refer to the Cancer and Immunotherapy summary in the Disease Treatment section.

Disease models in animals do not completely mimic the human diseases and viralvectorsmay infect various species differently. The testing of vectors in animal models often resemble the responses obtained in humans, but the larger size of humans in comparison to rodents presents additional challenges in the efficiency of delivery and penetration of tissue.Gene therapy, cell therapy, and oligonucleotide-based therapy agents are often tested in larger animal models, including rabbit, dog, pig and nonhuman primate models. Testing human cell therapy in animal models is complicated by immune rejections. Furthermore, humans are a very heterogeneous population. Their immune responses to the vectors, altered cells, or cell therapy products may differ or be similar to results obtained in animal models.

Challenges in the development of gene and cell therapy agents: Scientific challenges include the development of gene therapy agents that express the gene in the relevant tissue at the appropriate level for the desired duration of time. There are a lot of issues in that once sentence, and while these issues are easy to state, each one requires extensive research to identify the best means of delivery, how to control sufficient levels or numbers of cells, and factors that influence duration of gene expression or cell survival. After the delivery modalities are determined, identification and engineering of a promoter and control elements (on/off switch and dimmer switch) that will produce the appropriate amount of protein in the target cell can be combined with the relevant gene. This gene cassette is engineered into a vector or introduced into thegenomeof a cell and the properties of the delivery vehicle are tested in different types of cells in tissue culture. Sometimes things go as planned and then studies can be moved onto examination in animal models. In most cases, the gene/cell therapy agent may need to be improved further by adding new control elements to obtain the desired responses in cells and animal models.

Furthermore, the response of the immune system needs to be considered based on the type of gene or cell therapy being undertaken. For example, in gene or cell therapy for cancer, one aim is to selectively boost the existing immune response to cancer cells. In contrast, to treat genetic diseases like hemophilia and cystic fibrosis the goal is for the therapeutic protein to be accepted as an addition to the patients immune system.

If the new gene is inserted into the patients cellularDNA, the intrinsic sequences surrounding the new gene can affect its expression and vice versa. Scientists are now examining short DNA segments that may insulate the new gene from surrounding control elements. Theoretically, these insulator sequences would also reduce the effect of vector control signals in the gene cassette on adjacent cellular genes. Studies are also focusing on means to target insertion of the new gene into safe areas of the genome, to avoid influence on surrounding genes and to reduce the risk of insertional mutagenesis.

Challenges of cell therapy include the harvesting of the appropriate cell populations and expansion or isolation of sufficient cells for one or multiple patients. Cell harvesting may require specific media to maintain the stem cells ability toself-renew and mature into the appropriate cells. Ideally extra cells are taken from the individual receiving therapy. Those additional cells can expand in culture and can be induced to becomepluripotent stem cells(iPS), thus allowing them to assume a wide variety of cell types and avoiding immune rejection by the patient. The long term benefit of stem cell administration requires that the cells be introduced into the correct target tissue and become established functioning cells within the tissue. Several approaches are being investigated to increase the number of stem cells that become established in the relevant tissue.

Another challenge is developing methods that allow manipulation of the stem cells outside the body while maintaining the ability of those cells to produce more cells that mature into the desired specialized cell type. They need to provide the correct number of specialized cells and maintain their normal control of growth and cell division, otherwise there is the risk that these new cells may grow into tumors.

Challenges in funding: In most fields, funding for basic or applied research for gene and cell therapy is available through the National Institutes of Health (NIH) and private foundations. These are usually sufficient to cover the preclinical studies that suggest a potential benefit from a particular gene and cell therapy. Moving into clinical trials remains a huge challenge as it requires additional funding for manufacturing of clinical grade reagents, formal toxicology studies in animals, preparation of extensive regulatory documents, and costs of clinical trials.Biotechnology companies and the NIH are trying to meet the demand for this large expenditure, but many promising therapies are slowed down by lack of funding for this critical next phase.

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Theranostics 2018; 8(3):815-829. doi:10.7150/thno.19577

Review

Dong Wang1*, LeeAnn K. Li1,2*, Tiffany Dai3, Aijun Wang4, Song Li1,5

1. Department of Bioengineering, University of California, Los Angeles, CA 90095, USA;2. David Geffen School of Medicine, University of California, Los Angeles, CA 90024, USA;3. Department of Bioengineering, University of California, Berkeley, CA 94720, USA;4. Surgical Bioengineering Laboratory, Department of Surgery, School of Medicine, University of California, Davis, Sacramento, CA 95817, USA;5. Department of Medicine, University of California, Los Angeles, CA 90095, USA.* Equal contribution

This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/). See http://ivyspring.com/terms for full terms and conditions.

Understanding the contribution of vascular cells to blood vessel remodeling is critical for the development of new therapeutic approaches to cure cardiovascular diseases (CVDs) and regenerate blood vessels. Recent findings suggest that neointimal formation and atherosclerotic lesions involve not only inflammatory cells, endothelial cells, and smooth muscle cells, but also several types of stem cells or progenitors in arterial walls and the circulation. Some of these stem cells also participate in the remodeling of vascular grafts, microvessel regeneration, and formation of fibrotic tissue around biomaterial implants. Here we review the recent findings on how adult stem cells participate in CVD development and regeneration as well as the current state of clinical trials in the field, which may lead to new approaches for cardiovascular therapies and tissue engineering.

Keywords: Cardiovascular disease, Stem cell, atherosclerosis, vascular grafts, vascular smooth muscle cell.

Cardiovascular diseases (CVDs) such as ischemic heart disease, stroke, and peripheral artery disease are the leading cause of mortality and morbidity around the world: about 30% of global deaths and 10% of global disease burden a year are due to CVDs [1, 2]. In the past three decades, these diseases have been increasing in underdeveloped and developing countries. Although deaths from CVDs have declined in some developed countries with better healthcare interventions and systems and primary prevention, population growth and aging will drive up global CVDs in coming decades [1, 2].

Atherosclerosis is a chronic inflammatory disease resulting in clogged arteries or unstable plaque rupture [3, 4]. Currently, treatment of atherosclerosis includes reducing risk factors such as treatment of hypercholesterolemia and hypertension [1, 2] and, for advanced disease, surgery such as stent implantation and bypass surgery using autologous vessels or tissue-engineered vascular grafts [5]. However, thrombosis and secondary atherosclerosis are common complications following stent and graft implantation, particularly in small-diameter arteries and grafts [6]. New therapies are thus urgently needed for better prevention and treatment of atherosclerosis.

It is widely accepted that endothelial cell (EC) dysfunction, inflammatory cell recruitment, and vascular smooth muscle cell (SMC) de-differentiation contribute to atherogenesis [3, 4, 7]. In the past two decades, several types of vascular stem cells (VSCs), in addition to circulating progenitors, have been identified and characterized, with evidence that they are not only involved, but also play pivotal roles in blood vessel remodeling and disease development. VSCs or similar stem cells in mesenchymal tissues, for instance, also participate in the regeneration of blood vessels following the implantation of vascular grafts. Elucidating the regulatory mechanisms of these VSCs is fundamental to understanding vascular remodeling and may pave the way to developing novel, successful therapies for atherosclerosis. In this review, we analyze vascular remodeling through the lens of stem cells, and discuss the challenges we face in developing improved therapies for vascular diseases and regeneration.

Large and medium size blood vessels have three distinct layers: 1) the tunica intima, an inner lining of ECs, which may contain a small number of endothelial progenitor cells (EPCs) [8, 9]; 2) the tunica media, a thick middle layer composed of smooth muscle cells (SMCs) and a small number of stem cells; and 3) the tunica adventitia, an outer layer of connective tissue containing a heterogeneous population of cells, including fibroblasts, resident inflammatory cells (including macrophages, dendritic cells, T cells and B cells), microvascular (vasa vasorum) ECs around which pericytes reside, adrenergic nerves, and also stem cells (including multipotent mesenchymal stem cells, or MSCs) and progenitor cells (including those with macrophage, endothelial, smooth muscle, and hematopoietic potential) [10-18]. All these cells contribute, to varying extents, to the pathogenesis of atherosclerosis and vascular remodeling.

Atherosclerosis is thought to be initiated by dysfunctional or activated ECs [3, 7]. Various risk factors include genetic defects and environmental risks, behaviors like cigarette smoking and harmful use of alcohol, as well as disturbed blood flow, hypertension, hypercholesterolemia, infections, and other chronic conditions such as diabetes, obesity, autoimmune diseases, and aging [1, 2]. The injured endothelial area may be repaired by adjacent EC proliferation or EPCs from bone marrow or resident endothelium [19]. Disease begins when such endothelial repair does not occur properly.

Malfunctioning ECs secrete cytokines and upregulate expression of surface adhesive molecules to recruit circulating platelets, monocytes, T cells, neutrophils, dendritic cells, and mast cells to adhere to the site of endothelial injury and infiltrate into the subendothelial space. Within this space, monocytes differentiate into macrophages and scavenge lipid deposited from the circulation, becoming foam cells in the process [3, 20-22]. Notably, most of these foam cells are initially derived from preexisting intimal-resident myeloid progenitors rather than recently recruited blood monocytes [23]. In addition, the inflammatory cells activate medial SMCs and stem cells, prompting adventitial stem cells to proliferate and migrate into the intima, where they may differentiate and also obtain some properties of myofibroblasts and macrophages [3, 20-22, 24, 25]. Disease proceeds as the abnormal vascular wall processes prompt macrophages, together with leukocytes, activated ECs, and SMCs, to secrete increasing amounts of inflammatory cytokines to recruit more inflammatory cells from the circulation and resident adventitial tissues. This forms a cycle of inflammatory responses in local atherosclerotic lesions [3, 4, 26-28]. All these events lead to the development of fatty streaks, formation of neointima, and thickening of arterial walls seen at the early stages of atherosclerosis [3, 26]. The extracellular matrix, too, may play a role in lipid retention [29]. As these atherosclerotic lesions continue to grow and narrow the lumen, arteries may attempt to compensate by gradual dilation; however, this compensation reaches its limit beyond a certain size of atherosclerotic lesion.

Advanced atherosclerotic plaques have developed a fibrous cap that sequesters the underlying inflammatory mixture, which includes foam cells and extracellular lipid droplets, infiltrated T cells, macrophages, and mast cells, and necrotic tissue [3, 26]. The cap itself is mainly comprised of SMCs and collagen matrix, which can be degraded and ruptured by metalloproteases released by macrophages and mast cells. Stability of plaques is thus defined by thickness of the fibrous cap. Severe thrombosis may occur upon fibrous cap rupture, leading to acute coronary artery disease (myocardial infarction) and stroke [3, 26].

Several groups provide direct evidence that smooth muscle myosin heavy chain (SM-MHC)+ SMCs are a major contributor to neointimal thickening and atherosclerotic lesions, using transgenic mice with tamoxifen-regulated CreER under the control of a SM-MHC promoter (SM-MHC-CreER) [22, 30-33]. Interestingly, some studies suggest that SMCs in human atherosclerotic lesions are monoclonal [34, 35], implying heterogeneity of the SMC population. By using multi-colored lineage tracing in ApoE-/-/SM-MHC-CreER/Rosa26-Confetti transgenic mice, a recent study demonstrates that only a small number of SMCs proliferate and contribute to atherosclerotic plaques [36]. This is consistent with our single-cell analysis of SMCs showing that only a small subpopulation of SMCs is capable of proliferation and differentiation (unpublished data). However it is worth noting that, in addition to medial SMCs, other non-SMCs such as stem cells and ECs also contribute to the SMCs of neointima and atherosclerotic lesions [22, 33, 37, 38], while lesional macrophage-like cells can also be derived from SMCs [39], suggesting alternative mechanisms may also account for vascular disease development.

Endothelial to mesenchymal transition (EndoMT) is one possible mechanism. Some studies utilized Tie2-Cre mice for lineage tracing ECs and found that ECs contribute to pulmonary artery neointimal formation by differentiating into cells positive for smooth muscle -actin (-SMA) [40, 41]. However, other researchers found a very low frequency, in contrast, of EndoMT in the neointima [38]. Similarly, using Tie2-Cre mice to trace ECs in carotid artery neointimal formation, we found that although ECs contributed to neointimal formation, they still maintained endothelial identities and expressed CD31 but no or low -SMA expression [37]. This discrepancy requires further investigation with different animal models and tissue locations, and still leaves open the possibility of additional mechanisms for neointimal pathogenesis.

In addition to vascular SMCs and ECs, vascular stem and progenitor cells have been isolated from the circulation and from different layers of the artery wall, and have been implicated in vascular disease development. Key examples found in or around the vasculature are summarized in Table 1. The list is organized based on differentiation potential and tissue(s) of origin, and is discussed in detail below.

Vascular stem cells and progenitors

Bone marrow cells were reported to differentiate into SMCs in neointima and atherosclerotic lesions in the early 2000s [42-45]. These findings, however, remain controversial, as later studies in vascular transplant and injury models countered by arguing that bone marrow-derived cells did not in fact differentiate into neointimal SMCs, although they did participate in the inflammatory response [46-48]. A mouse wire injury model, for instance, found that some bone marrow cells were recruited to the neointima and expressed -SMA, but never became positive for mature SMC marker SM-MHC. Rather, these bone marrow cells expressed markers of monocytes and macrophages [48].

Other bone marrow-derived cells - specifically, certain EPCs - have also been identified as important for endothelial regeneration. It should be noted that the term endothelial progenitor cell has been applied to many different cell types, and defining what precisely it means to be an EPC is a source of controversy. Classification traditionally is divided into two methods: antigen classification, and culture-based classification. Both have been used to identify vascular-relevant EPCs.

Using the first method, cell-surface antigens are examined typically with flow cytometry to quantify relevant populations. Putative EPCs were first isolated by Asahara et al. (1997) from human peripheral blood by flow cytometry using surface markers CD34 and vascular endothelial growth factor receptor 2 (VEGFR-2, also known as kinase insert domain receptor, KDR, or fetal liver kinase 1, Flk1), both of which are characteristically expressed by ECs [49]. These circulating cells could contribute to neoangiogenesis postnatally by homing to angiogenic sites and acquiring characteristics of endothelium. Thereafter, other groups reported that EPCs contribute to endothelial regeneration in rodent models after various arterial injuries including vein graft atherosclerosis and mechanical injury [50-52], as well as in human diabetic wound healing [53].

Studies further showed that EPCs are in fact a heterogeneous population comprised of different subpopulations with different cell surface markers. In addition to CD34 and VEGFR-2, in an attempt to distinguish between immature and mature endothelial cells, investigators also commonly use markers like CD133 (also known as AC133), which is lost during endothelial maturation [54]. For example, Peichev et al. (2000) identified a unique subpopulation of EPCs (CD34+/VEGFR-2+/AC133+) in human fetal liver and peripheral blood [55]; another subpopulation of Flk1+/AC133+/CD34-/VE-cadherin- cells were also identified as EPCs in human bone marrow [56]. Despite the advantages of having specific markers for lineage tracing and drawing ties between disparate populations, one can see here too how antigen-based definitions may still be somewhat nonspecific in phenotype. The more antigen markers utilized, the more specific the definition, but also the fewer the cells identified - particularly considering the inherently probabilistic nature of antigen carriage for given cell types.

In the second method of classification, cells are isolated based on in vitro culture. Given the difficulties of finding specific surface markers for EPCs, some research groups isolated EPCs by single-cell colony-formation assay (SCCFA) based on the high self-renewal and proliferation potential of stem cells. Some studies subdivided EPCs based on their time of appearance in culture into populations which, interestingly, have different differentiation potential: early EPCs cannot differentiate into ECs, but only differentiate into macrophages and contribute to angiogenesis through paracrine factors, and thus were named as myeloid angiogenic cells (MACs); and late EPCs can differentiate into ECs and contribute to de novo blood vessel formation, and were dubbed endothelial colony forming cells (ECFCs) [57-61].

In addition to circulation-derived EPCs, EPCs with similar properties have been derived based on colony-formation assay from the vascular endothelium of large human blood vessels, placenta, and adipose tissue [62-64]. Mouse ECFCs have also been isolated from endothelial culture by surface markers lin-CD31+CD105+Sca1+c-Kit+, with c-Kit expression found to be critical for the clonal expansion of these ECFCs [65].

Beyond the nature of EPC classification, their functions, too, remain controversial. The concept of bone marrow-derived EPCs playing a fundamental role in the mechanism of vascular repair and regeneration has acquired many proponents as we described, though it remains hotly debated [66]. Pre-clinical animal studies showed that transplanted human EPCs formed microvessels and promoted vascular regeneration in vivo [49, 55, 56, 67, 68]. In mouse models of vascular graft transplantation, for instance, bone marrow cells contributed to the regenerated ECs of the grafts [50, 69, 70]. Nevertheless, another study countered that bone marrow-derived EPCs do not contribute to vascular endothelium in mouse models of bone marrow transplantation, tumor formation, and a parabiotic system [71].

A role for bone marrow-derived EPCs in atherogenesis similarly has been inferred, but accumulation of solid evidence in this role is mixed and still work in progress [52]. In an ApoE-/- mouse model, bone marrow-derived Sca-1+/CD34+/Flk-1+/CD133+ EPCs were found in the lesion-prone area of endothelium, possibly for repairing the injured endothelium [72]. However, other studies have said that, although there may exist a population of bone marrow-derived EPCs, ECs derived from the vascular bed are instead responsible for the EC replacement and regeneration seen in transplant arteriosclerosis [73].

In the clinical context, the role of EPCs remains unclear. Large-scale clinical studies suggested that high levels of EPCs were associated with reduced risk of cardiovascular diseases [74, 75] and improved outcomes after acute ischemic stroke [76-78] (versus poorer stroke outcomes if blood EPCs failed to increase [79]), and that vascular trauma, acute coronary diseases, and stroke induced elevated level of EPCs [76, 80, 81], presumably for purposes of vascular repair and maintenance. However, some also found no clear correlation between EPC level and endothelial function [82].

To date, much ambiguity and controversy remains in regards to the existence of true EPCs that can differentiate into ECs, their marker expression, location, and contribution to endothelial regeneration. It is possible that EPCs are a rare but dynamic population that respond to specific stimuli such as severe endothelial injury of large arteries or vascular transplantation [50, 69, 70], but not to tumor growth, which involves microvessels [71].

Stem and progenitor cells resident to vasculature have been identified across the different vessel wall layers. Similar to the bone marrow-derived progenitor cells, isolation has relied on antigen selection or culture-based characterization. Although those derived from the adventitia are better characterized and supported - evidence which will be elaborated momentarily - a few groups of stem cells have also been characterized in the media.

A population of calcifying vascular cells (CVCs) was first isolated from human atherosclerotic lesions in the arterial medial layer by Bostrm et al. (1993) and Tintut et al. (2003) and found to differentiate into SMC, osteogenic, and chondrogenic lineages [83, 84]. CVCs were harvested by tissue explant culture and were identified as expressing CD29 and CD44, two non-specific mesenchymal cell markers (adhesion receptors). However, no specific transcriptional markers were identified.

Later, in 2006, Sainz et al. isolated a small population of Sca-1+, c-kit (-/low), Lin-, CD34-/low cells from the media layer (around 60.8% prevalence in tunica media) of healthy murine thoracic and abdominal aortas [85]. They used a Hoechst DNA binding dye method to identify non-tissue-specific stem/progenitor cells based on their ability to expel the dye via the transmembrane transporter ATP-binding cassette transporter subfamily G member 2 (ABCG2). These cells gave rise to ECs (as determined by VE-cadherin, CD31, and von Willebrand factor expression) and SMCs (determined by -SMA, calponin, and SM-MHC expression) when cultured with vascular endothelial growth factor (VEGF) and transforming growth factor 1 (TGF-1)/platelet-derived growth factor BB (PDGF-BB) respectively, similar to Flk-1+ mesoangioblasts found in the embryonic dorsal aorta, and also produced (VE-cadherin+ and -SMA+) vascular-like branching structures of cells [85, 86].

Another population of vascular progenitors were isolated by Zaniboni, et al. from the media by internal digestion of porcine aortas with collagenase [87]. These cells were described as similar to both MSCs and pericytes. Like MSCs, they had elongated, spindle-shaped, fibroblast-like morphology, and met minimum MSC criteria [88] for CD90 and CD105 positivity while lacking expression of CD34 and CD45. They also expressed additional MSC markers CD44 and CD56 and displayed classic MSC differentiation potential into adipocytes, chondrocytes, and osteocytes. At the same time, in behavior considered distinctive of pericytes, in coculture with human umbilical vein endothelial cells they were able to form network-like structures [87].

MSCs themselves have also been implicated in atherosclerosis [89]. MSCs expressing Oct-4, Stro-1, Sca-1, and Notch-1, for instance, were identified in the wall of a range of vessel segments such as the aortic arch, and thoracic and femoral arteries. These multipotent cells exhibited adipogenic, chondrogenic, and leiomyogenic potential [14, 15].

Our group, too, has identified a population of multipotent vascular stem cells (MVSCs) in the arterial medial and adventitial layers that could significantly contribute to the population of traditionally defined proliferative and synthetic SMCs in SMC culture and in neointima [25, 37]. Upon vascular injury (e.g., denudation injury), Sox10+ MVSCs are activated, become proliferative, and migrated from both medial and adventitial layers to contribute to neointima formation [25, 37]. In addition, some Sox10- cells became Sox10+, suggesting Sox10 may be a marker of activated cells (Fig. 1). In wound healing and scar formation, MVSC-like Sox10+ cells (which are also found in soft tissues around blood vessels and throughout the body) can differentiate into both myofibroblasts and SMCs [24]. Following the implantation of polymer vascular grafts for instance, these cells, rather than SMCs, are recruited to the outer surface of the grafts and gradually differentiate into SMCs [70], recapitulating some aspect of vascular development.

Of special note is that vessel-derived stem/progenitor cells as well as MSCs isolated from ApoE-/- mice respond to the inflammatory environment and undergo calcification in the form of significantly greater osteogenesis and chondrogenesis [90]. MVSCs can also differentiate mesenchymally into osteogenic, chondrogenic, and adipogenic cells in vitro [25] and in vivo (unpublished observation), suggesting a possible role for them in vascular fat accumulation and calcification. As CVCs, in contrast, can differentiate into osteogenic and chondrogenic cells but not adipogenic cells in vitro, it is possible that CVCs are derived from MVSCs that have partially differentiated. Because almost all VSCs share some characteristics of MSCs, it is also possible that MSCs are derived from one or multiple subpopulations of VSCs.

The adventitia is the outermost layer of a blood vessel and is composed of a collagen-rich extracellular matrix embedded with a mixture of cells. The complexity of cellular composition reflects the pivotal role of the adventitia in vascular remodeling. Indeed, of the three blood vessel layers, evidence for vascular stem/progenitor cell enrichment in the adventitia, specifically along its border with the media, is the most abundant and robust. Its significance makes physiological and anatomical sense. Proximity to the vasa vasorum, which connect to the peripheral circulation, enable vessel wall communication with otherwise removed stem cell niches including the aforementioned bone marrow [14, 15], and the pivotal role of vasa vasorum density, structural integrity, and expansion in atheroma development and complications is well documented [91].

In human arteries, in addition to the Sox10+ MVSCs we described in the previous section [25], a population of vascular wall-resident multipotent stem cells (VW-MPSCs) were isolated from the adventitia by Klein, et al. [92]. They expressed certain MSC surface markers (including Stro1, CD105, CD73, CD44, CD90 and CD29) and positivity for stem cell-associated transcription factors Oct4 and Sox2, and demonstrated lack of contaminating mature EC or EPCs and hematopoietic stem cells (HPCs) by negativity for CD31, CD34, CD45, CD68, CD11b, and CD19. These VW-MPSCs also demonstrated adipocyte, chondrocyte, and osteocyte differentiation in culture conditions. In vivo transplantation with human umbilical vein endothelial cells (HUVECs) into immunodeficient mice via Matrigel resulted in new vessel formation covered with VW-MPSC-derived pericyte- and smooth muscle-like cells, an effect enhanced by VEGF, FGF-2, and TGF1 stimulation [92]. These authors more recently identified that HOX genes may epigenetically regulate VW-MPSC differentiation into SMCs, potentially contributing to neointimal formation and tumor vascularization [93].

Sox10+ MVSCs in aorta ring ex vivo culture. Aorta rings of Sox10-Cre/Rosa-RFP mice were cultured ex vivo, and imaged by two-photon microscopy. Arrows indicate the emerging Sox10+ cells. Scale bar, 100 m.

Progenitors have also been derived from human veins, dubbed saphenous vein-derived progenitor cells (SVPs) for their specific location of origin. Assessing endothelial markers CD34, CD31, and von Willebrand factor (vWF) in these cells showed CD34+, CD31-, vWF-. These highly proliferative cells were found to be localized around adventitial vasa vasorum, and expressed pericyte/mesenchymal antigens as well as stem cell marker Sox2. In an ischemic hindlimb model in immunodeficient mice, intramuscular injection of SVPs improved neovascularization and blood flow recovery, and the cells established N-cadherin-mediated physical contact with the capillary endothelium by day 14 post-transplantation [94]. These therapeutic benefits of vein-derived adventitial stem cells have been replicated in other studies using mouse models of ischemia, with one beginning to look towards manufacturing these cells for human angina therapy [95-97]. Spindle shaped MSCs (CD13+, CD29+, CD44+, CD54+) have also been isolated from human varicose saphenous vein intima. Displaying a similar gene expression profile to bone marrow-derived MSCs, these could differentiate into osteoblasts, chondrocytes, and adipocytes [98].

In rodents, another important progenitor population, Sca-1+ stem cells, has been described in the adventitia along the medial border. This population also expresses other stem cell markers including c-kit, CD34, and Flk1 and was first identified by Hu et al. in the aortic roots of ApoE-/- mice [99]. They had demonstrated capacity to differentiate into SMCs in vivo, with LacZ-labeled Sca-1+ cells found in vein graft atherosclerotic lesions after transplantation in the adventitial space, implying the migration of Sca-1+ cells from the adventitia to the neointima [99]. Years later, the same group illustrated the multipotency of the cells by demonstrating in a decellularized vessel graft mouse model the cells' in vitro differentiation into SMCs (with PDGF) and ECs (with VEGF) [100]. Implications to reduce neointimal thickness by applying VEGF to the adventitial layer, promoting stem cell differentiation into ECs rather than SMCs, were made clear as well [100].

Other studies have since further implicated Sca-1+ stem cells in atherosclerosis and adventitial remodeling [28, 101, 102]. The later stages of atherosclerosis, for instance, mainly involve resident proliferating macrophages rather than those differentiated from bone marrow monocytes [27]. These local resident proliferating macrophages were found to be derived from a subpopulation of Sca-1+ stem cells, resident macrophage progenitors, that also expressed CD45 [28]. In aging, Sca1+ adventitial cells enriched for monocyte/macrophage markers and CD45 were shown to be depleted by 3-fold in mature versus young mice, raising the question of whether age-related vascular degeneration may be due to such effects on progenitors in the vascular wall [103].

Recently, Majesky et al. used two in vivo SMC lineage-tracing approaches and showed that some Sca1+ vascular adventitial progenitors (CD34+) are derived from differentiated SMCs, potentially thereby contributing to maintenance of the resident vascular progenitor cell population [33]. In an earlier study, Shankman et al. had suggested that SMCs could de-differentiate into progenitor-like cells capable of differentiating into MSC- and macrophage-like cells [32]. Interestingly, in both cases, KLF4 was identified as a key modulator of cell phenotypic changes. This intriguing relationship between SMCs and VSCs (or VSC-like cells) warrants further investigation.

Overall, although a human ortholog of Sca-1 has yet to be identified, study of pathways and mechanisms surrounding these cells have been of great value, and results suggest that locally manipulating microenvironment is a possible angle for treating atherosclerotic disease [104].

Pericytes play important roles in regulating microvascular stability and dynamics [105]. They were first described over a century ago, and defined as another type of vascular mural cell that surround microvessels, forming an incomplete envelope around ECs and found within the microvascular basement membrane [106]. Pericyte-like cells have also been reported in the inner intima (mostly subendothelium) in human arteries of all sizes [107]. Several markers have been used to identify pericytes, including NG2 [108], CD146 [109, 110], PDGFR, and -SMA [111].

In recent years, accumulating studies have discovered important roles for pericytes in development and diseases. Pericyte-like cells were identified in atherosclerotic lesions and thought to be one of the sources of atherosclerotic cells [83, 112], which may come from the vasa vasorum, a specialized microvessel inside large vessel walls [91]. Cells histologically characterized as true pericytes were also found to comprise a second net-like subendothelial tissue layer, which combines with the endothelium to form the intimal barrier in healthy human and bovine microvasculature. In contrast with the endothelium, these pericytes were highly prothrombotic when exposed to serum and display overshooting growth behavior in endothelium-denuded vascular areas, making them potential key players in atherosclerosis, thrombosis, and thrombotic side-effects of venous coronary bypass grafting [92].

In the porcine aortic media, novel vascular progenitor cells with pericyte- and MSC-like properties were also found capable of differentiating into osteocytes, chondrocytes, and adipocytes [87]. Pericytes around microvessels in skeletal muscle are another type of myogenic progenitor cell distinct from satellite cells [113, 114].

Pericytes in multiple organs have been reported to have properties of MSCs [111]. Moreover, pericytes can differentiate into myofibroblasts and are another important cellular source of organ fibrosis [115-117]. It is likely that pericytes include subpopulations of stem cells or progenitors. In our recent work, we found Sox10+ stem cells in the stroma of subcutaneous connective tissues which had the same properties as MVSCs in large vessels [24, 25]. These Sox10+ stem cells are precursors of pericytes and fibroblasts, as described in the previous section, and contribute to both fibrosis and microvessel formation during tissue repair and regeneration [24]. Gli1+ stem cells had similarly wide distribution as the Sox10+ stem cells and were found in the perivascular space and also adventitial layer of large arteries. They could differentiate into myofibroblasts contributing to organ fibrosis, and neointimal SMCs contributing to atherosclerotic lesions and arterial calcification [115, 118].

Therapeutically, two separate studies examined the benefit of pericyte transplantation in mouse models of myocardial infarction. They found that pericytes from both saphenous vein [119] and skeletal muscle [120] attenuated left ventricular dilation, improved cardiac contractility and ejection fraction, reduced myocardial fibrosis and scarring, and improved neovascularization and angiogenesis. Saphenous vein-derived pericytes also reduced cardiomyocyte apoptosis, attenuated vascular permeability, and improved myocardial blood flow [119], while the skeletal muscle-derived pericytes significantly diminished host inflammatory cell infiltration at the infarct site as well [120]. Both studies attributed benefits to cellular interactions and paracrine effects [119, 120].

Dellavalle, et al. demonstrated the skeletal muscle-regenerating properties of both normal human pericytes and dystrophin-reprogrammed human Duchenne patient pericytes when transplanted into mouse models of muscular dystrophy [113]. In small-diameter tissue-engineered vascular grafts (TEVGs), exogenously seeded pericytes improved maintenance of patency after TEVG implantation into the aorta of rats (100% at 8 weeks, versus 38% unseeded controls) [121]. An endogenous approach has met with similar success, where promoting the differentiation of Sca-1+ stem/progenitor cells into the endothelial lineage has reduced neointimal thickness by up to 80% [100]. Altogether, these findings highlight stem cells as important players and potentially significant therapeutic targets in vascular remodeling, and underscore the multifactorial complexity of vascular disease pathogenesis.

The microenvironment plays important roles in regulating vascular cell function and the stem cell renewal and fate decision, and includes both biochemical factors (e.g., growth factors, cytokines) and biophysical factors (e.g., extracellular matrix, stiffness, flow shear stress and mechanical stretch).

Inflammatory cytokines, in addition to adhesion molecules, govern recruitment of relevant immune cells to the arterial wall in atherosclerosis. Beyond these traditional roles in regulating cell function and homeostasis, though, and notably for our discussion here, in recent years cytokines have also been found to regulate stem cell recruitment and activation during vascular remodeling [122, 123]. Cytokines like stromal cell-derived factor 1 (SDF-1), for example, has been shown to recruit bone marrow EPCs to form microvessels in hindlimb ischemic angiogenesis [124, 125] and to promote adventitial Sca1+ stem cells to migrate through vein graft walls and differentiate into neointimal SMCs [126]. In advanced atherosclerotic plaques, it is also believed that SDF-1 recruits SMC progenitor cells from bone marrow to the fibrotic cap [127]. Another cytokine, tumor necrosis factor- (TNF-), induces adventitial Sca1+ stem cells to differentiate into ECs, while suppressing SMC gene activation [128]. Growth factors like VEGF and PDGF-BB/TGF-1 can stimulate adventitial and medial stem cells to differentiate into ECs and SMCs, respectively [85, 100].

Among the biophysical factors found important for vascular cells, local disturbed flow is a major factor that induces EC dysfunction in the branches and curvatures of the arterial tree [129]. Disturbed flow shear stress can induce a series of intracellular signaling pathways in ECs and activate proliferative and inflammatory gene expression, initiating neointimal formation and atherosclerosis even in newborns [129, 130].

The extracellular matrix (ECM) is also important in regulating vascular dynamics. Subendothelial matrix proteoglycans are thought to contribute to lipid retention in the early stages of atherosclerosis [29]. ECM stiffness and embedded growth factors are critical in regulating cell functions. Our previous work has showed that stiff surfaces, together with TGF, promoted MSC differentiation into SMCs in vitro [131]. Collagen IV, too, has been reported to be critical in promoting embryonic stem cell differentiation into Sca-1+ stem cells, and to act together with aforementioned cytokines and growth factors to promote differentiation [132, 133]. Mechanical stretch and microtopography can regulate SMC differentiation and function as well [134, 135].

To date, the niche of VSCs has not been well defined. Although we know connection to the peripheral circulation via the vasa vasorum enables vessel niche communication with other stem cell niches like the bone marrow, how VSCs are activated by such communication, inflammatory signals, and local microenvironmental changes remains to be investigated.

As our understanding of the importance and mechanism of stem and progenitor cell involvement in human vascular remodeling has evolved, two therapeutic angles have arisen: 1) influencing endogenous VSC behavior to prevent initiation and progression of disease, and 2) exogenous stem cell delivery to promote disease reversal and healing of tissue injury. The application of more immature stem cells with greater differentiation potential such as embryonic and induced pluripotent stem cells to cardiovascular disease (including myocardial infarction, vascular regeneration in coronary and peripheral artery disease) has been reviewed elsewhere [136-138]. Adult stem cells such as those we have discussed pose multiple advantages in their accessibility (e.g., the stromal vascular fraction of adipose aspirates contain human blood vessel fragments; coronary bypass surgery makes pieces of aorta or segments of internal thoracic artery, radial artery, and saphenous vein readily available), decreased risk of uncontrolled differentiation (e.g., teratomas), and immune-privileged nature (in the case of MSCs and pericytes) that enables allogeneic use as well [139].

That said, clinical trials and therapies utilizing such VSCs are still sadly lacking. No human clinical trials to date have examined application of pericytes or resident VSCs for vascular disease. MSCs and EPCs, perhaps because of the broadness of their definition, have accumulated a more substantial body of clinically relevant evidence. The majority of clinical trials for atherosclerosis and diseases for which it is the primary cause - such as angina, myocardial ischemia, and ischemic stroke, all diseases primarily of the macrovasculature - utilize MSCs and EPCs instead. These trials focus, too, more on stem cell/progenitors for disease treatment rather than disease prevention. Limited evidence for underlying mechanisms suggests stem cell angiogenic roles play a large part in measurable therapeutic benefit; evidence for a therapeutic role in neointimal regression, in contrast, is lacking [140, 141]. It should be noted that MSCs and EPCs have also been utilized therapeutically to promote angiogenesis in diseases of the microvasculature such as diabetic ischemia-induced chronic wounds [53, 142] and peripheral occlusive disease [140, 141, 143], but we focus on macrovascular plaque-related diseases here instead.

In 2013, a phase III trial for refractory angina locally transplanted (G-CSF-stimulated) autologous blood cells positive for the EPC marker CD34 via percutaneous intramyocardial injection. The trial showed preliminary results consistent with those of earlier phase studies [144], although with higher placebo effects than previously detected, and animal studies lead us to believe benefit is derived from cell contribution to myocardial neoangiogenesis, and possible differentiation into cardiomyocytes and ECs [145-147]. If completed, it would have provided the requisite information for regulatory approval of the first cellular therapeutic for a cardiovascular indication [148]. Results may merit an expanded examination of therapeutic EPC transplantation, perhaps in combination with other vasculogenic mediators and scaffolds to improve EPC survival and function.

Other clinical trials have also attempted direct exogenous transplantation of adult bone-marrow-derived stem cells, but for myocardial ischemia (MI) and ischemic stroke patients. Several have found such intracoronary transplantation improves regional systolic function recovery and infarct size reduction in MI patients [149, 150], and a number of recent meta-analyses have confirmed improvements in not only left ventricular contractility after therapy [151-153] but also decreased mortality, acute MI recurrence, and readmission for heart failure [150, 152]. Still, effects of transplantation on infarct volume and remodeling are contradictory and inconclusive [150, 152-156]. BM cells, rather than incorporating, may prompt ischemic tissues to secrete paracrine signals (e.g., angiogenic factors); these signals in conjunction with transdifferentiation potential may underlie functional recovery [149, 156-158].

In stroke, promising results in experimental models [159] prompted clinical trials of intra-arterial or intravenous transplantation of autologous bone marrow mononuclear cells (including CD34+ progenitors). A phase I/II clinical trial in middle cerebral artery stroke patients transplanted 5-9 days after stroke found that changes in serum levels of GM-CSF, PDGF-BB, and MMP-2 associated with better functional outcomes were induced; however, varied impact on functional outcomes themselves was not measured [160]. Another phase II randomized control trial (RCT) found that cell therapy was safe, but had no beneficial effect on stroke outcome [161]. The first trial to explore dose-dependent efficacy of intra-arterial transplantation of bone marrow mononuclear cells in moderate-to-severe acute ischemic stroke patients is currently ongoing (IBIS trial, prospective phase II RCT) [162]. Despite promising animal studies, which suggest BM cell-based treatments can benefit endogenous neurorestoration by promoting contralesional pyramidal axon sprouting and preservation, increasing neurotrophic factor secretion, and possible synergistic effects between microvascular angiogenesis and neurogenesis, demonstrable long-term clinical therapeutic benefit of cell therapies for stroke is still being determined [141].

Secondary stimulation of endogenous progenitors has also been attempted. Granulocyte colony-stimulating factor (G-CSF) is one agent that can stimulate the bone marrow to release EPCs, in addition to release of granulocytes and hematopoietic stem cells [18]. Multiple clinical trials, encouraged by prior positive results in various animals [163], sought to assess its utility in upregulating endogenous EPC release in patients with ischemic heart disease. Results, however, have been mixed: although one study found an improvement of severe ischemia in severe MI patients [164] and a meta-analysis of seven RCTs including 364 acute MI patients found improvement of left ventricular ejection fraction (LVEF) [165], others (including an RCT and a meta-analysis of ten clinical trials including 445 patients) concluded no impact on infarct size, LV function, or coronary restenosis [166-168]. Interestingly, physical exercise, strongly established by many large-scale epidemiological studies as being robustly associated with decreased cardiovascular mortality and potent primary and secondary CVD prevention [169-173], has been found to mobilize EPCs from the bone marrow and is thought to exert its benefits mechanistically via the maintenance of an intact endothelial layer [174].

Using G-CSF in stroke patients has been less studied. A phase IIb RCT concluded in 2012 that G-CSF successfully and safely increased CD34+ cells by 9.5-fold relative to placebo, with a trend of reducing ischemic lesion volume [175]. Further study, though, is necessary.

The majority of completed clinical trials (as reported on clinicaltrials.gov) involving MSC transplantation for vascular disease focuses on treatment of myocardial ischemia, finding that treatment is tolerable and safe with improvements seen in metrics such as LVEF [176-178] and global EF [179], LV end-systolic [176, 178, 179] and diastolic volumes [178], and functional walk and cardiac tests [176] and global symptom scores [177]. A phase I/II clinical trial for patients with severe stable coronary artery disease and refractory angina transplanted autologous bone marrow-derived MSCs into their viable myocardium, and found similarly promising results. The trial showed sustained safety three years post-transplantation, significant clinical improvements in symptomatic and functional metrics, as well as reduced hospital admissions for CV disease [180].

Delivery route of MSCs, furthermore, was found by meta-analysis of six clinical trials involving 334 MI patients to shape efficacy of treatment. Greatest improvement in LVEF was seen if transendocardial injection and intravenous infusion, rather than intracoronary infusion, were used to deliver MSCs [181].

In 2015 an observational clinical study for coronary atherosclerosis examined outcomes of plasmonic resonance therapy using silica-gold nanoparticles that had been incubated with allogeneic mesenchymal CD73+ CD105+ stem-progenitor cells. Results showed highly safe, significant plaque regression relative to stenting controls (reduction of total atheroma volume up to 60mm3, or 37.8% of plaque burden, relative to current maximal success of conventional drugs of 6-14mm3) and late lumen enlargement without arterial remodeling [182].

Overall, although animal and preliminary clinical studies have revealed much promise, there remains much to be done in understanding the mechanism of VSC therapeutic benefits in order to appropriately target them for effective therapy.

Strong evidence has accumulated to demonstrate the involvement of various stem and progenitor cells in vascular regeneration and disease, including atherosclerotic neointimal formation. These stem cells display a nonuniform distribution both across the vessel wall as well as across different vascular territories, a distribution perhaps contributing to explanations of why different vascular segments may have variable susceptibility to vascular disease despite similar hemodynamics and environment [183]. Different populations of vascular cells, including SMCs, ECs, inflammatory cells (including macrophage and dendritic cell progenitors), and stem cells, may interact with and be subject to regulation by each other and by the local microenvironment during neointimal thickening. Recent studies show exosomes, nanometer lipid bilayer signaling particles secreted by cells with important roles in many physiological and pathological processes [184-187], have a hand in this regulation by mediating vascular calcification as found in atherosclerosis [188], atheroprotective communication between ECs and SMCs [189], and anti-inflammatory effects of MSCs [187]. Exosomes could thus be therapeutic targets of interest as well [190].

Identifying proper cellular targets (e.g., using screening methods such as RNA-sequencing and epigenetic profiling to characterize VSCs, along with other techniques such as laser microdissection and immunofluorescence to identify key VSC markers) and understanding the underlying regulatory mechanisms will facilitate the development of successful therapies for vascular disease. Given their differentiation potential into SMCs and ECs, these stem cells could also be good cellular sources for fabricating vascular grafts or otherwise promoting vascular regeneration.

Far as the field has come, several critical questions remain to be addressed. First, given the diversity of stem cells discovered by different research groups, confirming whether these cells are distinct populations and determining their relationship with proliferative/synthetic SMCs will be necessary. It will be helpful to obtain consensus on specific panels of markers to define different stem cell populations. Examining to what degree the difference in their marker expression profiles may be a result of different culture conditions in vitro, too, will be of importance.

Second, the niche of VSCs needs to be further characterized to define the macro and microenvironmental factors that maintain VSCs in a quiescent versus activated state, and how such factors promote healthy survival.

Third, stem cell fate needs to be determined in long-term in vivo experiments. However, stem cells may become activated and differentiated quickly at the early phase of neointimal thickening in vivo, which makes capture of the phenotype by immunohistology difficult. Genetic lineage tracing techniques would address this problem, if obstacles of selection of good markers and of availability of transgenic animal models can be surmounted. Such techniques could also address the relative contributions of different cell types, and multi-color reporter mice could be used to investigate heterogeneity within the same population.

Fourth, the behavior of VSCs under various pathological conditions should be elucidated. Stem cell activation and differentiation are regulated by various microenvironmental factors. Changes in biochemical and biophysical factors in a disease state and the effects of these factors, individually or in combination, may have profound effects on stem cell functions. Conversely, taking creative inspiration from current successful therapies for atherosclerosis and brainstorming approaches for cellular therapies to target their same mechanisms could yield therapies with fewer side-effects and more targeted results. For instance, any conversation on atherosclerosis would be incomplete without mention of statins, the current mainstay of treatment [191, 192]. Research has shown that, independent of cholesterol reduction, statins may exert their beneficial effects via EPC mobilization. This may be a promising direction for future therapies [52]. Similarly, piggybacking on the putative plaque-stabilizing mechanism of statins by use of the chemokine SDF-1 to recruit bone marrow-derived SM progenitor cells to the fibrous cap has yielded increases in cap thickness without altering artery diameter in mice [127]. This finding may prove useful for unstable atherosclerosis if further studies in large animals and humans continue to yield promising results.

Fifth, especially with sourcing of vascular wall MSCs becoming increasingly feasible [17], there is great promise in cell therapies if details on differences in identity and manufacturing based on specific vascular and cell source can be fleshed out. Despite their mechanistic significance, EPCs and other progenitors without immune-privilege, in contrast with MSCs and pericytes which do, may pose a challenge in clinical application if the goal is exogenous transplantation [139]. Endogenous recruitment and processes may be more feasible for these other progenitors. Although stem cell transplantation has been proven to be safe and benefit tissue regeneration, the mechanisms of benefit, too, are unclear at present. Overall, clinical trials certainly remain of value - as phenomena in humans are ultimately distinct from those in animals - but it is clear that such applications are yet in the early stages. The mixed results clearly indicate that an improved understanding of underlying mechanisms is necessary not only for effective design of therapeutic translation and study, but also for interpretation of results. Ongoing risk and safety assessment will continue to be necessary in parallel.

Finally, besides delivery of exogenous stem cells for therapies, the potential of endogenous recruitment or of using stem cells as novel targets of therapies needs to be further investigated in vitro and in vivo. In vitro isolated VSCs can be used for drug screening. A well-defined culture model, such as co-culture with SMCs, mechanical loading, and 3D culture that mimics the in vivo microenvironment, would be valuable. Blood vessel tissue ex vivo culture is better than cell culture as it mimics the niche of cell-cell interactions and native extracellular matrix, which may be useful when combined with tissue clarity techniques and transgenic animal models. All these new tools and technologies will continue to facilitate further discoveries in vascular stem cell biology, enabling development of diagnostic and therapeutic strategies with unprecedented efficacy and capability to combat vascular disease and promote regeneration.

CVD: cardiovascular disease; EC: endothelial cell; EPC: endothelial progenitor cell; SMC: smooth muscle cell; VSC: vascular stem cell; MSC: mesenchymal stem cell; MVSC: multipotent vascular stem cell; CVC: calcifying vascular cells; -SMA: smooth muscle -actin; SM-MHC: smooth muscle myosin heavy chain.

This work was supported by grants from the National Institutes of Health (HL117213 and HL121450 to S.L.) and the Medical Scientist Training Program at UCLA (NIH T32 GM008042 to L.L.).

The authors have declared that no competing interest exists.

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Adult Stem Cells in Vascular Remodeling - Theranostics

Theranostics 2017; 7(7):2067-2077. doi:10.7150/thno.19427

Review

Kiwon Ban1, Seongho Bae2, Young-sup Yoon2, 3

1. Department of Biomedical Sciences, City University of Hong Kong, Hong Kong;2. Department of Medicine, Division of Cardiology, Emory University, Atlanta, Georgia, USA;3. Severance Biomedical Science Institute, Yonsei University College of Medicine, Seoul, Korea.

This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/). See http://ivyspring.com/terms for full terms and conditions.

Cardiomyocytes (CMs) derived from human pluripotent stem cells (hPSCs) are considered a most promising option for cell-based cardiac repair. Hence, various protocols have been developed for differentiating hPSCs into CMs. Despite remarkable improvement in the generation of hPSC-CMs, without purification, these protocols can only generate mixed cell populations including undifferentiated hPSCs or non-CMs, which may elicit adverse outcomes. Therefore, one of the major challenges for clinical use of hPSC-CMs is the development of efficient isolation techniques that allow enrichment of hPSC-CMs. In this review, we will discuss diverse strategies that have been developed to enrich hPSC-CMs. We will describe major characteristics of individual hPSC-CM purification methods including their scientific principles, advantages, limitations, and needed improvements. Development of a comprehensive system which can enrich hPSC-CMs will be ultimately useful for cell therapy for diseased hearts, human cardiac disease modeling, cardiac toxicity screening, and cardiac tissue engineering.

Keywords: Cardiomyocytes, hPSCs

Heart failure is the leading cause of death worldwide [1]. Approximately 6 million people suffer from heart failure in the United States every year [1]. Despite this high incidence, existing surgical and pharmacological interventions for treating heart failure are limited because these approaches only delay the progression of the disease; they cannot directly repair the damaged hearts [2]. In the case of large myocardial infarction (MI), patients progress to heart failure and die within short time from the onset of symptoms [3].

The adult human heart has minimal regenerative capacity, because during mammalian development, the proliferative capacity of cardiomyocytes (CMs) progressively diminishes and becomes terminally differentiated shortly after birth [4].Therefore, once CMs are damaged, they are rarely restored [5]. When MI occurs, the infarcted area is easily converted to non-contractile scar tissue due to loss of CMs and replacement by fibrosis [6]. Development of a fibroblastic scar initiates a series of events that lead to adverse remodeling, hypertrophy, and eventual heart failure [2, 3, 7].

While heart transplantation is considered the most viable option for treating advanced heart failure, the number of available donor hearts is always less than needed [6]. Therefore, more realistic therapeutic options have been required [2]. Accordingly, over the past two decades, cell-based cardiac repair has been intensively pursued [2, 7]. Several different cell types have been tested and varied outcomes were obtained. Indeed, the key factor for successful cell-based cardiac repair is to find the optimal cell type that can restore normal heart function. Naturally, CMs have been considered the best cell type to repair a damaged heart [8]. In fact, many scientists hypothesized that implanted CMs would survive in damaged hearts and form junctions with host CMs and synchronously contract with the host myocardium [9]. In fact, animal studies with primary fetal or neonatal CMs demonstrated that transplanted CMs could survive in infarcted hearts [9-11]. These primary CMs reduced scar size, increased wall thickness, and improved cardiac contractile function with signs of electro-mechanical integration [9-11]. These studies strongly suggest that CMs can be a promising source to repair the heart. However, the short supply and ethical concerns disallow using primary human CMs. In a patient with ischemic cardiomyopathy, about 40-50% of the CMs are lost in 40 to 60 grams of heart tissue [7]. Even if we seek to regenerate a fairly small portion of the damaged myocardium, a large number of human primary CMs would be required, which is impossible.

Accordingly, CMs differentiated from human pluripotent stem cells (hPSCs) including both embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have emerged as a promising option for candidate CMs for cell therapy [12, 13]. hPSCs have many advantages as a source for CMs. First, hPSCs have obvious cardiomyogenic potential. hPSC derived-CMs (hPSC-CMs) possess a clear cardiac phenotype, displaying spontaneous contraction, cardiac excitation-contraction (EC) coupling, and expression of cardiac transcription factors, cardiac ion channels, and cardiac structural proteins [14, 15]. Second, undifferentiated hPSCs and their differentiated cardiac progeny display significant proliferation capacity, allowing generation of a large number of hPSC-CMs. Lastly, many pre-clinical studies demonstrated that implantation of hPSC-CMs can repair injured hearts and improve cardiac function [16-19]. Histologically, implanted hPSC-CMs are engrafted, aligned and coupled with the host CMs in a synchronized manner [16-19].

In the last two decades, various protocols for differentiating hPSCs into CMs have been developed to improve the efficiency, purity and clinical compatibility [20] [18]. The reported differentiation methods include, but are not limited to: differentiation via embryoid body (EB) formation [20], co-culture with END-2 cells [18], and monolayer culture [15, 21, 22]. The EB-mediated CM differentiation protocol is one of the most widely employed methods due to its simple procedure and low cost. However, it often becomes labor-intensive to produce scalable EBs for further differentiation, which makes it difficult for therapeutic applications. EB-mediated differentiation also produces inconsistent results, showing beating CMs from 5% to 70% of EBs. Recently, researchers developed monolayer methods to complement the problems of EB-based methods [15, 21, 22]. In one representative protocol, hPSCs are cultured at a high density (up to 80%) and treated with a high concentration of Activin A (100 ng/ml) for 1 day and BMP4 (10 ng/ml) for 4 days followed by continuous culture on regular RPMI media with B27 [15]. This protocol induces spontaneous beating at approximately 12 days and produces approximately 40% CMs after 3 weeks. These hPSC-CMs can be further cultured in RPMI-B27 medium for another 2-3 weeks without significant cell damage [15]. However, these protocols use media with proprietary formulations, which complicates clinical application. As shown, most monolayer-based methods employ B27, which is a complex mix of 21 components. Some of the components of B27, including bovine serum albumin (BSA), are animal-derived products, and the effects of B27 components on differentiation, maturation or subtype specification processes are poorly defined. In 2014, Burridge and his colleagues developed an advanced protocol that is defined, cost-effective and efficient [22]. By subtracting one component from B27 at a time and proceeding with cardiac differentiation, the researchers reported that BSA and L-ascorbic acid 2-phosphate are essential components in cardiac differentiation. Subsequently, by replacing BSA with rice-derived recombinant human albumin, the chemically defined medium with 3 components (CDM3) was produced. The application of a GSK-inhibitor, CHIR99021, for the first 2 days followed by 2 days of the Wnt-inhibitor Wnt-59 to cells is an optimal culture condition in CDM3 resulting in similar levels of live-cell yields and CM differentiation [22].

Despite remarkable improvement in the generation of hPSC-CMs, obtaining pure populations of hPSC-CMs still remains challenging. Currently available methods can only generate a mixture of cells which include not only CMs but other cell types. This is one of the most critical barriers for applications of hPSC-CMs in regenerative therapy, drug discovery, and disease investigation. For Instance, cardiac transplantation of non-pure hPSC-CMs mixed with undifferentiated hPSCs or other cell types may produce tumors or unwanted cell types in hearts [23-28]. Accordingly, a pure or enriched population of hPSC-CMs would be required, particularly for cardiac cell therapy. Enriched hPSC-CMs would also be more beneficial for myocardial repair due to improved electric and mechanical properties [29]. A pure, homogeneous population of hPSC-CMs would pose less arrhythmic risk and have enhanced contractile performance, and would be more useful in disease modeling as they better reflect native CM physiology. Finally, purified hPSC-CMs would better serve for testing drug efficacy and toxicity. Therefore, many researchers have tried to develop methods to purify CMs from cardiomyogenically differentiated hPSCs.

There are three important topics that are not addressed in this review. First is the beneficial role of other cell types such as endothelial cells and fibroblasts in the integration, survival, and function of CMs [30-32]. We did not discuss this issue because it would need a separate review due to the volume of material. While the roles of such cells are important, the value of having purified hPSC-CMs is not diminished. Although cell mixtures or tissue engineered products can be used, unless purified CMs are employed, they would form tumors or other cells/tissues when implanted in vivo. Our point here is that even if cardiomyocytes are mixed with non-CMs, all cells should be clearly defined and purified as well. If the mixture is made in a non-purified or non-defined manner (for example, an unsophisticated top-down approach), there would be undefined cells that are neither CMs, ECs, nor fibroblasts and these unidentified cells will make aberrant tissues or tumors. Second, we did not deal with maturation of hPSC-CMs because of its broad scope and depth [33, 34]. Third is direct reprogramming or conversion of somatic cells into CMs. There has been another advancement in the generation of CMs by directly reprogramming or converting somatic cells into CM-like cells by introducing a combination of cardiac transcription factors (TFs) or muscle-specific microRNAs (miRNAs) both in vitro and in vivo [35-41]. These cells are referred to as induced CMs (iCMs) or cardiac-like myocytes (iCLMs). While this is an important advancement, we did not cover this topic either due to its size. Accordingly, this review will focus on the various strategies for purifying or enriching hPSC-CMs reported to date (Figure 1).

Early on, researchers isolated hPSC-CMs manually under microscopy by mechanically separating out the beating areas from myogenically differentiating hPSC cultures [18, 20, 42]. This method usually generates 5-70% hPSC-CMs. Although generally crude, it can enrich even higher percentages of CMs with further culture. This manual isolation method has the advantage of being easy, but while it can be useful for small-scale research, it is very labor intensive and not scalable, precluding large scale research or clinical application.

Currently available strategies for enriching cardiomyocytes derived from human pluripotent stem cells.

Xu et el. reported that hPSC-CMs, due to their physical and structural properties, can be enriched by Percoll density gradient centrifugation [43]. Percoll was first formulated by Pertoft et al [44] and it was originally developed for the isolation of cells, organelles, or viruses by density centrifugation. The Percoll-based method has several advantages. The procedure for Percoll-based separation is very simple and easy, it is inexpensive, and its low viscosity allows more rapid sedimentation and lower centrifugal forces compared to a sucrose density gradient. Lastly, it can be prepared and kept for a long time in an isotonic solution to maintain osmolarity. Although Percoll separation has resulted in major improvements in hPSC-CM isolation procedures, it has clear limitations with regard to purity and scalability. Previous studies found that Percoll separation is only able to enrich 40 -70% of hPSC-CMs. It is also not compatible with large-scale enrichment of hPSC-CMs.

Another traditional method for purifying hPSC-CMs is based on the expression of a drug resistant gene or a fluorescent reporter gene such as eGFP or DsRed, which is driven by a cardiac specific promoter in genetically modified hPSC lines [45, 46]. Here, enrichment of hPSC-CMs can be achieved by either drug treatment to eliminate cells that do not express the drug resistant gene or with FACS to isolate fluorescent cells [47, 48].

Briefly, enrichment of PSC-CMs by genetically based selection was first reported by Klug et al [49]. The authors generated murine ES cell lines via permanent gene transfection of the aminoglycoside phosphotransferase gene driven by the MHC (MYH7) promoter. With this approach, highly purified murine ESC-CMs up to 99% were achieved. Next, several studies reported the use of various CM-specific promoters to enrich ESC-CMs such as Mhc (Myh6), Myh7, Ncx (Sodium Calcium exchanger) and Mlc2v (Myl2) [46, 50, 51]. In the case of hESCs, MHC/EGFP hESCs were generated by permanent transfection of the EGFP-tagged MHC promoter [52]. Similarly, an NKX2.5/eGFP hESC line was generated to enrich GFP positive CMs [53]. However, since MHC and NKX2.5 are expressed in general CMs, the resulting CMs contain a mixture of the three subtypes of CMs, nodal-, atrial-, and ventricular-like CMs. To enrich only ventricular-like CMs, Huber et al. generated MLC2v/GFP ESCs to be able to isolate MLC2v/GFP positive ventricular-like cells by FACS [52] [54-57]. In addition, the cGATA6 gene was used to purify nodal-like hESC-CMs [58]. Future studies should focus on testing new types of cardiac specific promoters and devising advanced selection procedures to improve this strategy.

While fluorescence-based cell sorting is more widely used, the drug selection method may be a better approach to enrich high purity of hPSC-CMs during differentiation/culture as it does not require FACS. The advantage is its capability for high-purity cell enrichment due to specific gene-based cell sorting. These highly pure cells can allow more precise mechanistic studies and disease modeling. Despite its many advantages, the primary weakness of genetic selection is genetic manipulation, which disallows its use for therapeutic application. Insertion of reporter genes into the host genome requires viral or nonviral transfection/transduction methods, which can induce mutagenesis and tumor formation [50, 59-61].

Practically, antibody-based cell enrichment is the best method for cell purification to date. When cell type-specific surface proteins or marker proteins are known, one can tag cells with antibodies against the proteins and sort the target cells by FACS or magnetic-activated cell sorting (MACS). The main advantage is its specificity and sensitivity, and its utility is well demonstrated in research and even in clinical therapy with hematopoietic cells [62]. Another advantage is that multiple surface markers can be used at the same time to isolate target cells when one marker is not sufficient. However, no studies have reported surface markers that are specific for CMs, even after many years. Recently, though, several researchers demonstrated that certain proteins can be useful for isolating hPSC-CMs.

In earlier studies, KDR (FLK1 or VEGFR2) and PDGFR- were used to isolate cardiac progenitor cells [63]. However, since these markers are also expressed on hematopoietic cells, endothelial cells, and smooth muscle cells, they could not enrich only hPSC-CMs. Next, two independent studies reported two surface proteins, SIRPA [64] and VCAM-1 [65], which it was claimed could specifically identify hPSC-CMs. Dubois et al. screened a panel of 370 known antibodies against CMs differentiated from hESCs and identified SIRPA as a specific surface protein expressed on hPSC-CMs [64]. FACS with anti-SIRPA antibody enabled the purification of CMs and cardiac precursors from cardiomyogenically differentiating hPSC cultures, producing cardiac troponin T (TNNT2, also known as cTNT)-positive cells, which are generally considered hPSC-CMs, with up to 98% purity. In addition, a study performed by Elliot and colleagues identified another cell surface marker, VCAM1 [53]. In this study, the authors used NKX2.5/eGFP hESCs to generate hPSC-CMs, allowing the cells to be sorted by their NKX2.5 expression. NKX2.5 is a well-known cardiac transcription factor and a specific marker for cardiac progenitor cells [66, 67]. To identify CM-specific surface proteins, the authors performed expression profiling analyses and found that expression levels of both VCAM1 and SIRPA were significantly upregulated in NKX2.5/eGFP+ cells. Flow cytometry results showed that both proteins were expressed on the cell surface of NKX2.5/eGFP+ cells. Differentiation day 14 NKX2.5/eGFP+ cells expressed VCAM1 (71 %) or SIRPA (85%) or both VCAM1 and SIRPA (37%). When the FACS-sorted SIRPA-VCAM1-, SIRPA+ or SIRPA+VCAM1+ cells were further cultured, only SIRPA+ or SIRPA+VCAM1+ cells showed NKX2.5/eGFP+ contracting portion. Of note, NKX2.5/eGFP and SIRPA positive cells showed higher expression of smooth muscle cell and endothelial cell markers indicating that cells sorted solely based on SIRPA expression may not be of pure cardiac lineage. Hence, the authors concluded that a more purified population of hPSC-CMs could be isolated by sorting with both cell surface markers. Despite significant improvements, it appears that these surface markers are not exclusively specific for CMs as these antibodies also mark other cell types including smooth muscle cells and endothelial cells. Furthermore, they are also known to be expressed in the brain and the lung, which raises concerns whether these surface proteins can be used as sole markers for the purification of hPSC-CMs compatible for clinical applications.

More recently, Protze et al. reported successful differentiation and enrichment of sinoatrial node-like pacemaker cells (SANLPCs) from differentiating hPSCs by using cell surface markers and an NKX2-5-reporter hPSC line [68]. They found that BMP signaling specified cardiac mesoderm toward the SANLPC fate and retinoic acid signaling enhanced the pacemaker phenotype. Furthermore, they showed that later inhibition of the FGF pathway, the TFG pathway, and the WNT pathway shifted cell fate into SANLPCs, and final cell sorting for SIRPA-positive and CD90-negative cells resulted in enrichment of SANLPCs up to ~83%. These SIRPA+CD90- cells showed the molecular, cellular and electrophysiological characteristics of SANLPCs [68]. While this study makes important progress in enriching SANLPCs by modulating signaling pathways, no specific surface markers for SANLPCs were identified and the yield was still short of what is usually expected for cells purified via FACS.

Hattori et al. developed a highly efficient non-genetic method for purifying hPSC-derived CMs, in which they employed a red fluorescent dye, tetramethylrhodamine methyl ester perchlorate (TMRM), that can label active mitochondria. Since CMs contain a large number of mitochondria, CMs from mice and marmosets (monkey) could be strongly stained with TMRM [69]. They further found that primary CMs from several different types of animals and CMs derived from both mESCs and hESCs were successfully purified by FACS up to 99% based on the TMRM signals. In addition to its efficiency for CM enrichment, TMRM did not affect cell viability and disappeared completely from the cells within 24 hrs. Importantly, injected hPSC-CMs purified in this way did not form teratoma in the heart tissues. However, since TMRM only functions in CMs with high mitochondrial density, this method cannot purify entire populations of hPSC-CMs [64]. While originally TMRM was claimed to be able to isolate mature hPSC-CMs, mounting evidence indicates that hPSC-CMs are similar to immature human CMs at embryonic or fetal stages. Therefore, both the exact phenotype of the cells isolated by TMRM and its utility are rather questionable [33, 34]. Two subsequent studies demonstrated that TMRM failed to accurately distinguish hPSC-CMs due to the insufficient amounts of mitochondria [64].

Employing the unique metabolic properties of CMs, Tohyama et al. developed an elegant purification method to enrich PSC-CMs [70]. This approach is based on the remarkable biochemical differences in lactate and glucose metabolism between CMs and non-CMs, including undifferentiated cells. Mammalian cells use glucose as their main energy source [71]. However, CMs are capable of energy production from different sources such as lactate or fatty acids [71]. A comparative transcriptome analysis was performed to detect metabolism-related genes which have different expression patterns between newborn mouse CMs and undifferentiated mouse ESCs. These results showed that CMs expressed genes encoding tricarboxylic acid (TCA) cycle enzymes more than genes related to lipid and amino acid synthesis and the pentose phosphate cycle compared to undifferentiated ESCs. To further prove this observation, they compared the metabolites of these pathways using fluxome analysis between CMs and other cell types such as ESCs, hepatocytes and skeletal muscle cells, and found that CMs have lower levels of metabolites related to lipid and amino acid synthesis and pentose phosphate. Subsequently, authors cultured newborn rat CMs and mouse ESCs in media with lactate, forcing the cells to use the TCA cycle instead of glucose, and they observed that CMs were the only cells to survive this condition for even 96 hrs. They further found that when PSC derivatives were cultured in lactate-supplemented and glucose-depleted culture medium, only CMs survived. Their yield of CM population was up to 99% and no tumors were formed when these CMs were transplanted into hearts. This lactate-based method has many advantages: its simple procedures, ease of application, no use of FACS for cell sorting, and relatively low cost. More recently, this method was applied to large-scale CM aggregates to ensure scalability. As a follow-up study, the same group recently reported a more refined lactate-based enrichment method which further depletes glutamine in addition to glucose [72]. The authors found that glutamine is essential for the survival of hPSCs since hPSCs are highly dependent on glycolysis for energy production rather than oxidative phosphorylation. The use of glutamine- and glucose-depleted lactate-containing media resulted in more highly purified hPSC-CMs with less than 0.001% of residual PSCs [72]. One concern of this lactate-based enrichment method is the health of the purified hPSC-CMs, because physiological and functional characteristics of hPSC-CMs cultured in glucose- and glutamine-depleted media for a long time may have functional impairment since CMs with mature mitochondria were not able to survive without glucose and glutamine, although they were able to use lactate to synthesize pyruvate and glutamate [72]. In addition, this lactate-based strategy can only be applied to hPSC- CMs, but not other hPSC derived cells such as neuron or -cells.

Our group also recently reported a new method to isolate hPSC-CMs by directly labelling cardiac specific mRNAs using nano-sized probes called molecular beacons (MBs) [29, 73, 74]. Designed to detect intracellular mRNA targets, MBs are dual-labeled antisense oligonucleotide (ODN) nano-scale probes with a DNA or RNA backbone, a Cy3 fluorophore at the 5' end, and a Black Hole quencher 2 (BHQ2) at the 3' end [75, 76]. They form a stem-loop (hairpin) structure in the absence of a complementary target, quenching the fluorescence of the reporter. Hybridization with the target mRNA opens the hairpin and physically separates the reporter from the quencher, allowing a fluorescence signal to be emitted upon excitation. The MB-based method can be applied to the purification of any cell type that has known specific gene(s) [77].

In one study [29], we designed five MBs targeting unique sites in TNNT2 or MYH6/7 mRNA in both mouse and human. To determine the most efficient transfection method to deliver MBs into living cells, various methods were tested and nucleofection was found to have the highest efficiency. Next, we tested the sensitivity and specificity of MBs using an immortalized mouse CM cell line, HL-1, and other cell types. Finally, we narrowed it down to one MB, MHC-MB, which showed >98% sensitivity and > 95% specificity. This MHC-MB was applied to cardiomyogenically differentiated mouse and human PSCs and FACS sorting was performed. The resultant MHC-MB-positive cells expressed cardiac proteins at ~97% when measured by flow cytometry. These sorted cells also demonstrated spontaneous contraction and all the molecular and electrophysiological signatures of human CMs. Importantly, when these purified CMs were injected into the mouse infarcted myocardium, they were well integrated into the myocardium without forming any tumors, and they improved cardiac function.

In a subsequent study [74], we refined a method to enrich ventricular CMs from differentiating PSCs (vCMs) by targeting a transcription factor which is not robustly expressed in cells. Since vCMs are the main source for generating cardiac contractile forces and the most frequently damaged in the heart, there has been great demand to develop a method that can obtain a pure population of vCMs for cardiac repair. Despite this critical unmet need, no studies have demonstrated the feasibility of isolating ventricular CMs without permanently altering their genome. Accordingly, we first designed MBs targeting the Iroquois homeobox protein 4 (Irx4) mRNA, a vCM specific transcription factor [78, 79]. After testing sensitivity and specificity, one IRX4-MB was selected and applied to myogenically differentiated mPSCs. The FACS-sorted IRX4-MB-positive cells exhibited vCM-like action potentials in more than 98% of cells when measured by several electrophysiological analyses including patch clamp and Ca2+ transient analyses. Furthermore, these cells maintained spontaneous contraction and expression of vCM-specific proteins.

The MB-based cell purification method is theoretically the most broadly applicable technology among the purification methods because it can isolate any target cells expressing any specific gene. Thus, the MB-based sorting technique can be applied to the isolation of other cell types such as neural-lineage cells or islet cells, which are critical elements in regenerative medicine but do not have specific surface proteins identified to date. In addition, theoretically, this technology may have the highest efficiency when MBs are designed to have the maximum sensitivity and specificity for the cells of interest, but not others. These characteristics are particularly important for cell therapy. Despite these advantages, the delivery method of MB into the cells needs to be improved. So far, nucleofection is the best delivery method, but caused some cell damage with < 70% cell viability. Thus, development of a safer delivery method will enable wider application of MB-based cell enrichment.

Recently, Miki and colleagues reported a novel method for purifying cells of interest based on endogenous miRNA activity [80]. Miki et al. employed several synthetic mRNA switches (= miRNA switch), which consist of synthetic mRNA sequences that include a recognition sequence for miRNA and an open reading frame that codes a desired gene, such as a regulatory protein that emits fluorescence or promotes cell death. If the miRNA recognition sequence binds to miRNA expressed in the desired cells, the expression of the regulatory protein is suppressed, thus distinguishing the cell type from others that do not contain the miRNA and express the protein.

Briefly, the authors first identified 109 miRNA candidates differentially expressed in distinct stages of hPSC-CMs (differentiation day 8 and 20). Next, they found that 14 miRNAs were co-expressed in hPSC-CMs at day 8 and day 20 and generated synthetic mRNAs that recognize these 14 miRNA, called miRNA switches. Among those miRNA switches, miR-1-, miR-208a-, and miR-499a-5p-switches successfully enriched hPSC-CMs with purity of sorted cells up to 96% determined by TNNT2 intracellular flow cytometry. Particularly, hPSC-CMs enriched by the miR-1-switch showed substantially higher expression of several cardiac specific genes/proteins and lower expression of non-CM genes/proteins compared with control cells. Patch clamp confirmed that these purified hPSC-CMs possessed both ventricular-like and atrial-like action potentials.

One of the major advantages of this technology is its wider applicability to other cell types. miRNA switches have the flexibility to design the open reading frame in the mRNA sequence such that any desired transgene can be incorporated into the miRNA switches to regulate the cell phenotype based on miRNA activity. The authors tested this possibility by incorporating BIM sequence, an apoptosis inducer, into the cardiac specific miR-1- and miR-208a switches and tested whether they could selectively induce apoptosis in non-CMs. They found that miR-1- and miR-208a-Bim-switches successfully enriched cTNT-positive hPSC-CMs without cell sorting. Enriched hPSC-CMs by 208a-Bim-switch were injected into the hearts of mice with acute MI and they engrafted, survived, expressed both cTNT and CX43, and formed gap junctions with the host myocardium. No teratoma was detected. In addition, other miRNA switches such as miR-126-, miR-122-5p-, and miR-375-switches targeting endothelial cells, hepatocytes, and -cells, respectively, successfully enriched these cell types differentiated from hPSCs. However, identification of specific miRNAs expressed only in the specific cell type of interest and verification of their specificity in target cells will be key issues for continuing to use this miRNA-based cell enrichment method.

Recent advances in biomedical engineering have contributed to developing systems that can isolate target cells using physicochemical properties of the cells. Microfluidic systems have been intensively applied for cell separation due to recent improvements in miniaturizing a cell culture system [81-83]. These advances made possible the design of automated microfluidic devices with cellular microenvironments and controlled fluid flows that save time and cost in experiments. Thus, there have been an increasing number of studies seeking to apply the microfluidic system for cell separation. Among the first, Singh et al. tested the possibility of using a microfluidic system for the separation of hPSC [84] by preparative detachment of hPSCs from differentiating cultures based on differences in the adhesion properties of different cell types. Distinct streams of buffer that generated varying levels of shear stress further allowed selective enrichment of hPSC colonies from mixed populations of adherent non-hPSCs, achieving up to 95% purity. Of note, this strategy produced hPSC survival rates almost two times higher than FACS, reaching 80%.

Subsequently, for hPSC-CMs purification, Xin et al. developed a microfluidic system with integrated ridge-like flow derivations and fishnet-like microcolumns for the enrichment of hiPSC-CMs [85]. This device is composed of a 250 mm-long microfluidic channel, which has two integrated parallel microcolumns with surfaces functionalized with anti-human TRA-1 antibody for undifferentiated hiPSC trapping. Aided by the ridge-like surface patterns on the upper wall of the channel, micro-streams are generated so that the cell suspension of mixed undifferentiated hiPSCs and hiPSC-CMs are forced to cross the functionalized fishnet-like microcolumns, resulting in trapping of undifferentiated hiPSCs due to the interaction between the hiPSCs and the columns, and the untrapped hiPSC-CMs are eventually separated. By modulating flow and coating with anti-human TRA-1 antibody, they were able to enrich CMs to more than 80% purity with 70% viability. While this study demonstrated that a microfluidic device could be used for purifying hPSC-CMs, it was not realistic because the authors used a mixture of only undifferentiated hiPSCs and hiPSC-CMs. In real cardiomyogenically differentiated hiPSCs, undifferentiated hiPSCs are rare and many intermediate stage cells or other cell types are present, so the idea that this simple device can select only hiPSC-CMs from a complex mixture is uncertain.

Overall, the advantages of microfluidic system based cell isolation include fast speed, improved cell viability and low cost owing to the automated microfluidic devices that can control cellular microenvironments and fluid flows [86-88]. However, microfluidic-based cell purification methods have limitations in terms of low purity and scalability [89-92]. In fact, there have been only a few studies demonstrating the feasibility that microfluidic device-based cell separation could achieve higher than 80% purity of target cells. Furthermore, currently available microfluidic devices allow only separation of a small number of cells (< 1011). To employ microfluidic devices for large-scale cell production, we need to develop a next generation of microfluidic devices that can achieve a throughput greater than 1011 sorted cells per hour with > 95% purity.

Having available a large quantity of a homogeneous population of cells of interest is an important factor in advancing biomedical research and clinical medicine, and is especially true for hPSC-CMs. While remarkable progress has been made in the methods for differentiating hPSCs into CMs, technologies to enrich hPSC-CMs, particularly those which are clinically applicable, have been emerging only over the last few years. Contamination with other cell types and even the heterogeneous nature of hPSC-CMs significantly hinder their use for several future applications such as cardiac drug toxicology screening, human cardiac disease modeling, and cell-based cardiac repair. For instance, cardiac drug-screening assays require pure populations of hPSC-CMs, so that the observed signals can be attributed to effects on human CMs. Studies of human cardiac diseases can also be more adequately interpreted with purified populations of patient derived hiPSC-CMs. Clinical applications with hPSC-CMs will need to be free of other PSC derivatives to minimize the risk of teratoma formation and other adverse outcomes.

Summary of representative methods for hPSC-CM purification

Schematic pictures of microfluidic device for enriching hiPSC-CMs. (A) The part of the device designed for trapping undifferentiated hiPSCs. (B) (Left) Illustration of the overall microfluidic device assembled with peristaltic pump, cell suspension reservoirs, and a serpentine channel. (Right) Magnified image showing a channel combining microcolumns and ridge-like flow derivation structures. Modified from Li et al. On chip purification of hiPSC-derived cardiomyocytes using a fishnet-like microstructure. Biofabrication. 2016 Sep 8;8(3): 035017

Therefore, development of reproducible, effective, non-mutagenic, scalable, and economical technologies for purifying hPSC-CMs, independent of hPSC lines or differentiation protocols, is a fundamental requirement for the success of hPSC-CM applications. Fortunately, new technologies based on the biological specificity of CMs such as MITO-tracker, molecular beacons, lactate-enriched-glucose depleted-media, and microRNA switches have been developed. In addition, technologies based on engineering principles have recently yielded a promising platform using microfluidic technology. While due to the short history of this field, more studies are needed to verify the utility of these technologies, the growing attention toward this research is a welcome move.

Another important question raised recently is how to non-genetically purify chamber-specific subtypes of CMs such as ventricular-like, atrial-like and nodal-like hPSC-CMs. So far, only a few studies have addressed this potential with human PSCs. We also showed that a molecular beacon-based strategy could enrich ventricular CMs differentiated from PSCs [74]. Another study demonstrated generation of SA-node like pacemaker cells by using a stepwise treatment of various morphogens and small molecules followed by cell sorting with several sub-specific surface markers. However, the yield of both studies was relatively low (<85%). Given the growing clinical importance of chamber-specific CMs, the strategies for purifying specific subtypes of CM that are independent of hPSC lines or differentiation protocols should be continuously developed. A recently reported cell surface capture-technology [93, 94] may facilitate identification of chamber specific CM proteins that will be useful for target CM isolation.

In summary, technological advances in the purification of hPSC-CMs have opened an avenue for realistic application of hPSC-CMs. Although initial success was achieved for purification of CMs from differentiating hPSC cultures, questions such as scalability, clinical compatibility, and cellular damage remain to be answered and isolation of human subtype CMs has yet to be demonstrated. While there are other challenges such as maturity, in vivo integration, and arrhythmogenecity, this development of purification technology represents major progress in the field and will provide unprecedented opportunities for cell-based therapy, disease modeling, drug discovery, and precision medicine. Furthermore, the availability of chamber-specific CMs with single cell analyses will facilitate more sophisticated investigation of human cardiac development and cardiac pathophysiology.

This work was supported by the Bio & Medical Technology Development Program of the National Research Foundation (NRF) funded by the Korean government (MSIP) (No 2015M3A9C6031514), the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (HI15C2782, HI16C2211) and grants from NHLBI (R01HL127759, R01HL129511), NIDDK (DP3-DK108245). This work was also supported by a CityU Start-up Grant (No 7200492), a CityU Research Project (No 9610355), and a Georgia Immuno Engineering Consortium through funding from Georgia Institute of Technology, Emory University, and the Georgia Research Alliance.

The authors have declared that no competing interest exists.

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Current Strategies and Challenges for Purification of ...

Stem cell, an undifferentiated cell that can divide to produce some offspring cells that continue as stem cells and some cells that are destined to differentiate (become specialized). Stem cells are an ongoing source of the differentiated cells that make up the tissues and organs of animals and plants. There is great interest in stem cells because they have potential in the development of therapies for replacing defective or damaged cells resulting from a variety of disorders and injuries, such as Parkinson disease, heart disease, and diabetes. There are two major types of stem cells: embryonic stem cells and adult stem cells, which are also called tissue stem cells.

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cardiovascular disease: Cardiac stem cells

Cardiac stem cells, which have the ability to differentiate (specialize) into mature heart cells and therefore could be used to repair damaged or diseased heart tissue, have garnered significant interest in the development of treatments for heart disease and cardiac defects. Cardiac stem

Embryonic stem cells (often referred to as ES cells) are stem cells that are derived from the inner cell mass of a mammalian embryo at a very early stage of development, when it is composed of a hollow sphere of dividing cells (a blastocyst). Embryonic stem cells from human embryos and from embryos of certain other mammalian species can be grown in tissue culture.

The most-studied embryonic stem cells are mouse embryonic stem cells, which were first reported in 1981. This type of stem cell can be cultured indefinitely in the presence of leukemia inhibitory factor (LIF), a glycoprotein cytokine. If cultured mouse embryonic stem cells are injected into an early mouse embryo at the blastocyst stage, they will become integrated into the embryo and produce cells that differentiate into most or all of the tissue types that subsequently develop. This ability to repopulate mouse embryos is the key defining feature of embryonic stem cells, and because of it they are considered to be pluripotentthat is, able to give rise to any cell type of the adult organism. If the embryonic stem cells are kept in culture in the absence of LIF, they will differentiate into embryoid bodies, which somewhat resemble early mouse embryos at the egg-cylinder stage, with embryonic stem cells inside an outer layer of endoderm. If embryonic stem cells are grafted into an adult mouse, they will develop into a type of tumour called a teratoma, which contains a variety of differentiated tissue types.

Mouse embryonic stem cells are widely used to create genetically modified mice. This is done by introducing new genes into embryonic stem cells in tissue culture, selecting the particular genetic variant that is desired, and then inserting the genetically modified cells into mouse embryos. The resulting chimeric mice are composed partly of host cells and partly of the donor embryonic stem cells. As long as some of the chimeric mice have germ cells (sperm or eggs) that have been derived from the embryonic stem cells, it is possible to breed a line of mice that have the same genetic constitution as the embryonic stem cells and therefore incorporate the genetic modification that was made in vitro. This method has been used to produce thousands of new genetic lines of mice. In many such genetic lines, individual genes have been ablated in order to study their biological function; in others, genes have been introduced that have the same mutations that are found in various human genetic diseases. These mouse models for human disease are used in research to investigate both the pathology of the disease and new methods for therapy.

Extensive experience with mouse embryonic stem cells made it possible for scientists to grow human embryonic stem cells from early human embryos, and the first human stem cell line was created in 1998. Human embryonic stem cells are in many respects similar to mouse embryonic stem cells, but they do not require LIF for their maintenance. The human embryonic stem cells form a wide variety of differentiated tissues in vitro, and they form teratomas when grafted into immunosuppressed mice. It is not known whether the cells can colonize all the tissues of a human embryo, but it is presumed from their other properties that they are indeed pluripotent cells, and they therefore are regarded as a possible source of differentiated cells for cell therapythe replacement of a patients defective cell type with healthy cells. Large quantities of cells, such as dopamine-secreting neurons for the treatment of Parkinson disease and insulin-secreting pancreatic beta cells for the treatment of diabetes, could be produced from embryonic stem cells for cell transplantation. Cells for this purpose have previously been obtainable only from sources in very limited supply, such as the pancreatic beta cells obtained from the cadavers of human organ donors.

The use of human embryonic stem cells evokes ethical concerns, because the blastocyst-stage embryos are destroyed in the process of obtaining the stem cells. The embryos from which stem cells have been obtained are produced through in vitro fertilization, and people who consider preimplantation human embryos to be human beings generally believe that such work is morally wrong. Others accept it because they regard the blastocysts to be simply balls of cells, and human cells used in laboratories have not previously been accorded any special moral or legal status. Moreover, it is known that none of the cells of the inner cell mass are exclusively destined to become part of the embryo itselfall of the cells contribute some or all of their cell offspring to the placenta, which also has not been accorded any special legal status. The divergence of views on this issue is illustrated by the fact that the use of human embryonic stem cells is allowed in some countries and prohibited in others.

In 2009 the U.S. Food and Drug Administration approved the first clinical trial designed to test a human embryonic stem cell-based therapy, but the trial was halted in late 2011 because of a lack of funding and a change in lead American biotech company Gerons business directives. The therapy to be tested was known as GRNOPC1, which consisted of progenitor cells (partially differentiated cells) that, once inside the body, matured into neural cells known as oligodendrocytes. The oligodendrocyte progenitors of GRNOPC1 were derived from human embryonic stem cells. The therapy was designed for the restoration of nerve function in persons suffering from acute spinal cord injury.

Embryonic germ (EG) cells, derived from primordial germ cells found in the gonadal ridge of a late embryo, have many of the properties of embryonic stem cells. The primordial germ cells in an embryo develop into stem cells that in an adult generate the reproductive gametes (sperm or eggs). In mice and humans it is possible to grow embryonic germ cells in tissue culture with the appropriate growth factorsnamely, LIF and another cytokine called fibroblast growth factor.

Some tissues in the adult body, such as the epidermis of the skin, the lining of the small intestine, and bone marrow, undergo continuous cellular turnover. They contain stem cells, which persist indefinitely, and a much larger number of transit amplifying cells, which arise from the stem cells and divide a finite number of times until they become differentiated. The stem cells exist in niches formed by other cells, which secrete substances that keep the stem cells alive and active. Some types of tissue, such as liver tissue, show minimal cell division or undergo cell division only when injured. In such tissues there is probably no special stem-cell population, and any cell can participate in tissue regeneration when required.

The epidermis of the skin contains layers of cells called keratinocytes. Only the basal layer, next to the dermis, contains cells that divide. A number of these cells are stem cells, but the majority are transit amplifying cells. The keratinocytes slowly move outward through the epidermis as they mature, and they eventually die and are sloughed off at the surface of the skin. The epithelium of the small intestine forms projections called villi, which are interspersed with small pits called crypts. The dividing cells are located in the crypts, with the stem cells lying near the base of each crypt. Cells are continuously produced in the crypts, migrate onto the villi, and are eventually shed into the lumen of the intestine. As they migrate, they differentiate into the cell types characteristic of the intestinal epithelium.

Bone marrow contains cells called hematopoietic stem cells, which generate all the cell types of the blood and the immune system. Hematopoietic stem cells are also found in small numbers in peripheral blood and in larger numbers in umbilical cord blood. In bone marrow, hematopoietic stem cells are anchored to osteoblasts of the trabecular bone and to blood vessels. They generate progeny that can become lymphocytes, granulocytes, red blood cells, and certain other cell types, depending on the balance of growth factors in their immediate environment.

Work with experimental animals has shown that transplants of hematopoietic stem cells can occasionally colonize other tissues, with the transplanted cells becoming neurons, muscle cells, or epithelia. The degree to which transplanted hematopoietic stem cells are able to colonize other tissues is exceedingly small. Despite this, the use of hematopoietic stem cell transplants is being explored for conditions such as heart disease or autoimmune disorders. It is an especially attractive option for those opposed to the use of embryonic stem cells.

Bone marrow transplants (also known as bone marrow grafts) represent a type of stem cell therapy that is in common use. They are used to allow cancer patients to survive otherwise lethal doses of radiation therapy or chemotherapy that destroy the stem cells in bone marrow. For this procedure, the patients own marrow is harvested before the cancer treatment and is then reinfused into the body after treatment. The hematopoietic stem cells of the transplant colonize the damaged marrow and eventually repopulate the blood and the immune system with functional cells. Bone marrow transplants are also often carried out between individuals (allograft). In this case the grafted marrow has some beneficial antitumour effect. Risks associated with bone marrow allografts include rejection of the graft by the patients immune system and reaction of immune cells of the graft against the patients tissues (graft-versus-host disease).

Bone marrow is a source for mesenchymal stem cells (sometimes called marrow stromal cells, or MSCs), which are precursors to non-hematopoietic stem cells that have the potential to differentiate into several different types of cells, including cells that form bone, muscle, and connective tissue. In cell cultures, bone-marrow-derived mesenchymal stem cells demonstrate pluripotency when exposed to substances that influence cell differentiation. Harnessing these pluripotent properties has become highly valuable in the generation of transplantable tissues and organs. In 2008 scientists used mesenchymal stem cells to bioengineer a section of trachea that was transplanted into a woman whose upper airway had been severely damaged by tuberculosis. The stem cells were derived from the womans bone marrow, cultured in a laboratory, and used for tissue engineering. In the engineering process, a donor trachea was stripped of its interior and exterior cell linings, leaving behind a trachea scaffold of connective tissue. The stem cells derived from the recipient were then used to recolonize the interior of the scaffold, and normal epithelial cells, also isolated from the recipient, were used to recolonize the exterior of the trachea. The use of the recipients own cells to populate the trachea scaffold prevented immune rejection and eliminated the need for immunosuppression therapy. The transplant, which was successful, was the first of its kind.

Research has shown that there are also stem cells in the brain. In mammals very few new neurons are formed after birth, but some neurons in the olfactory bulbs and in the hippocampus are continually being formed. These neurons arise from neural stem cells, which can be cultured in vitro in the form of neurospheressmall cell clusters that contain stem cells and some of their progeny. This type of stem cell is being studied for use in cell therapy to treat Parkinson disease and other forms of neurodegeneration or traumatic damage to the central nervous system.

Following experiments in animals, including those used to create Dolly the sheep, there has been much discussion about the use of somatic cell nuclear transfer (SCNT) to create pluripotent human cells. In SCNT the nucleus of a somatic cell (a fully differentiated cell, excluding germ cells), which contains the majority of the cells DNA (deoxyribonucleic acid), is removed and transferred into an unfertilized egg cell that has had its own nuclear DNA removed. The egg cell is grown in culture until it reaches the blastocyst stage. The inner cell mass is then removed from the egg, and the cells are grown in culture to form an embryonic stem cell line (generations of cells originating from the same group of parent cells). These cells can then be stimulated to differentiate into various types of cells needed for transplantation. Since these cells would be genetically identical to the original donor, they could be used to treat the donor with no problems of immune rejection. Scientists generated human embryonic stem cells successfully from SCNT human embryos for the first time in 2013.

While promising, the generation and use of SCNT-derived embryonic stem cells is controversial for several reasons. One is that SCNT can require more than a dozen eggs before one egg successfully produces embryonic stem cells. Human eggs are in short supply, and there are many legal and ethical problems associated with egg donation. There are also unknown risks involved with transplanting SCNT-derived stem cells into humans, because the mechanism by which the unfertilized egg is able to reprogram the nuclear DNA of a differentiated cell is not entirely understood. In addition, SCNT is commonly used to produce clones of animals (such as Dolly). Although the cloning of humans is currently illegal throughout the world, the egg cell that contains nuclear DNA from an adult cell could in theory be implanted into a womans uterus and come to term as an actual cloned human. Thus, there exists strong opposition among some groups to the use of SCNT to generate human embryonic stem cells.

Due to the ethical and moral issues surrounding the use of embryonic stem cells, scientists have searched for ways to reprogram adult somatic cells. Studies of cell fusion, in which differentiated adult somatic cells grown in culture with embryonic stem cells fuse with the stem cells and acquire embryonic stem-cell-like properties, led to the idea that specific genes could reprogram differentiated adult cells. An advantage of cell fusion is that it relies on existing embryonic stem cells instead of eggs. However, fused cells stimulate an immune response when transplanted into humans, which leads to transplant rejection. As a result, research has become increasingly focused on the genes and proteins capable of reprogramming adult cells to a pluripotent state. In order to make adult cells pluripotent without fusing them to embryonic stem cells, regulatory genes that induce pluripotency must be introduced into the nuclei of adult cells. To do this, adult cells are grown in cell culture, and specific combinations of regulatory genes are inserted into retroviruses (viruses that convert RNA [ribonucleic acid] into DNA), which are then introduced to the culture medium. The retroviruses transport the RNA of the regulatory genes into the nuclei of the adult cells, where the genes are then incorporated into the DNA of the cells. About 1 out of every 10,000 cells acquires embryonic stem cell properties. Although the mechanism is still uncertain, it is clear that some of the genes confer embryonic stem cell properties by means of the regulation of numerous other genes. Adult cells that become reprogrammed in this way are known as induced pluripotent stem cells (iPS).

Similar to embryonic stem cells, induced pluripotent stem cells can be stimulated to differentiate into select types of cells that could in principle be used for disease-specific treatments. In addition, the generation of induced pluripotent stem cells from the adult cells of patients affected by genetic diseases can be used to model the diseases in the laboratory. For example, in 2008 researchers isolated skin cells from a child with an inherited neurological disease called spinal muscular atrophy and then reprogrammed these cells into induced pluripotent stem cells. The reprogrammed cells retained the disease genotype of the adult cells and were stimulated to differentiate into motor neurons that displayed functional insufficiencies associated with spinal muscular atrophy. By recapitulating the disease in the laboratory, scientists were able to study closely the cellular changes that occurred as the disease progressed. Such models promise not only to improve scientists understanding of genetic diseases but also to facilitate the development of new therapeutic strategies tailored to each type of genetic disease.

In 2009 scientists successfully generated retinal cells of the human eye by reprogramming adult skin cells. This advance enabled detailed investigation of the embryonic development of retinal cells and opened avenues for the generation of novel therapies for eye diseases. The production of retinal cells from reprogrammed skin cells may be particularly useful in the treatment of retinitis pigmentosa, which is characterized by the progressive degeneration of the retina, eventually leading to night blindness and other complications of vision. Although retinal cells also have been produced from human embryonic stem cells, induced pluripotency represents a less controversial approach. Scientists have also explored the possibility of combining induced pluripotent stem cell technology with gene therapy, which would be of value particularly for patients with genetic disease who would benefit from autologous transplantation.

Researchers have also been able to generate cardiac stem cells for the treatment of certain forms of heart disease through the process of dedifferentiation, in which mature heart cells are stimulated to revert to stem cells. The first attempt at the transplantation of autologous cardiac stem cells was performed in 2009, when doctors isolated heart tissue from a patient, cultured the tissue in a laboratory, stimulated cell dedifferentiation, and then reinfused the cardiac stem cells directly into the patients heart. A similar study involving 14 patients who underwent cardiac bypass surgery followed by cardiac stem cell transplantation was reported in 2011. More than three months after stem cell transplantation, the patients experienced a slight but detectable improvement in heart function.

Patient-specific induced pluripotent stem cells and dedifferentiated cells are highly valuable in terms of their therapeutic applications because they are unlikely to be rejected by the immune system. However, before induced pluripotent stem cells can be used to treat human diseases, researchers must find a way to introduce the active reprogramming genes without using retroviruses, which can cause diseases such as leukemia in humans. A possible alternative to the use of retroviruses to transport regulatory genes into the nuclei of adult cells is the use of plasmids, which are less tumourigenic than viruses.

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stem cell | Definition, Types, Uses, Research, & Facts ...

Editor's Note: This story, originally printed in the September 1999 issue of Scientific American, is being posted due to a new study showing that nerve cells can be regenerated by knocking out genes that typically inhibit their growth.

For Chinese gymnast Sang Lan, the cause was a highly publicized headfirst fall during warm-ups for the 1998 Goodwill Games. For Richard Castaldo of Littleton, Colo., it was bullets; for onetime football player Dennis Byrd, a 1992 collision on the field; and for a child named Samantha Jennifer Reed, a fall during infancy. Whatever the cause, the outcome of severe damage to the spinal cord is too often the same: full or partial paralysis and loss of sensation below the level of the injury.

Ten years ago doctors had no way of limiting such disability, aside from stabilizing the cord to prevent added destruction, treating infections and prescribing rehabilitative therapy to maximize any remaining capabilities. Nor could they rely on the cord to heal itself. Unlike tissue in the peripheral nervous system, that in the central nervous system (the spinal cord and brain) does not repair itself effectively. Few scientists held out hope that the situation would ever change.

Then, in 1990, a human trial involving multiple research centers revealed that a steroid called methylprednisolone could preserve some motor and sensory function if it was administered at high doses within eight hours after injury. For the first time, a therapy had been proved to reduce dysfunction caused by spinal cord trauma. The improvements were modest, but the success galvanized a search for additional therapies. Since then, many investigatorsincluding us have sought new ideas for treatment in studies of why an initial injury triggers further damage to the spinal cord and why the disrupted tissue fails to reconstruct itself.

In this article we will explain how the rapidly burgeoning knowledge might be harnessed to help people with spinal cord injuries. We should note, however, that workers have also been devising strategies that compensate for cord damage instead of repairing it. In the past two years, for example, the U.S. Food and Drug Administration has approved two electronic systems that regulate muscles by sending electrical signals through implanted wires. One returns certain hand movements (such as grasping a cup or a pen) to patients who have shoulder mobility; another restores a measure of control over the bladder and bowel.

A different approach can also provide grasping ability to certain patients. Surgeons identify tendons that link paralyzed forearm muscles to the bones of the hand, disconnect them from those muscles and connect them to arm muscles regulated by parts of the spine above the injury (and thus still under voluntary control). Further, many clinicians suspect that initiating rehabilitative therapy earlyexercising the limbs almost as soon as the spine is stabilizedmay enhance motor and sensory function in limbs. Those perceptions have not been tested rigorously in people, but animal studies lend credence to them.

The Cord at Work The organ receiving all this attention is no thicker than an inch but is the critical highway of communication between the brain and the rest of the body. The units of communication are the nerve cells (neurons), which consist of a bulbous cell body (home to the nucleus), trees of signal-detecting dendrites, and an axon that extends from the cell body and carries signals to other cells. Axons branch toward their ends and can maintain connections, or synapses, with many cells at once. Some traverse the entire length of the cord.

The soft, jellylike cord has two major systems of neurons. Of these, the descending, motor pathways control both smooth muscles of internal organs and striated muscles; they also help to modulate the actions of the autonomic nervous system, which regulates blood pressure, temperature and the bodys circulatory response to stress. The descending pathways begin with neurons in the brain, which send electrical signals to specific levels, or segments, of the cord. Neurons in those segments then convey the impulses outward beyond the cord.

The other main system of neurons the ascending, sensory pathwaystransmit sensory signals received from the extremities and organs to specific segments of the cord and then up to the brain. Those signals originate with specialized, transducer cells, such as sensors in the skin that detect changes in the environment or cells that monitor the state of internal organs. The cord also contains neuronal circuits (such as those involved in reflexes and certain aspects of walking) that can be activated by incoming sensory signals without input from the brain, although they can be influenced by messages from the brain.

The cell bodies in the trunk of the cord reside in a gray, butterfly-shaped core that spans the length of the spinal cord. The ascending and descending axonal fibers travel in a surrounding area known as the white matter, so called because the axons are wrapped in myelin, a white insulating material. Both regions also house glial cells, which help neurons to survive and work properly. The glia include star-shaped astrocytes, microglia (small cells that resemble components of the immune system) and oligodendrocytes, the myelin producers. Each oligodendrocyte myelinates as many as 40 different axons simultaneously.

The precise nature of a spinal cord injury can vary from person to person. Nevertheless, certain commonalities can be discerned.

When Injury Strikes When a fall or some other force fractures or dislocates the spinal column, the vertebral bones that normally enclose and protect the cord can crush it, mechanically killing and damaging axons. Occasionally, only the gray matter in the damaged area is significantly disrupted. If the injury ended there, muscular and sensory disturbances would be confined to tissues that send input to or receive it from neurons in the affected level of the cord, without much disturbing function below that level.

For instance, if only the gray matter were affected, a cervical 8 (C8) lesion involving the cord segment where the nerves labeled C8 originatewould paralyze the hands without impeding walking or control over the bowel and bladder. No signals would go out to, or be received from, the tissues connected to the C8 nerves, but the axons conveying signals up and down the surrounding white matter would keep working.

In contrast, if all the white matter in the same cord segment were destroyed, the injury would now interrupt the vertical signals, stopping messages that originated in the brain from traveling below the damaged area and blocking the flow to the brain of sensory signals coming from below the wound. The person would become paralyzed in the hands and lower limbs and would lose control over urination and defecation.

Sadly, the initial insult is only the beginning of the trouble. The early mechanical injury triggers a second wave of damageone that, over the subsequent minutes, hours and days, progressively enlarges the lesion and thus the extent of functional impairment. This secondary spread tends to occur longitudinally through the gray matter at first before expanding into the white matter (roughly resembling the inflation of a footballshaped balloon). Eventually the destruction can encompass several spinal segments above and below the original wound.

The end result is a complex state of disrepair. Axons that have been damaged become useless stumps, connected to nothing, and their severed terminals disintegrate. Often many axons remain intact but are rendered useless by loss of their insulating myelin. A fluid-filled cavity, or cyst, sits where neurons, other cells and axons used to be. And glial cells proliferate abnormally, creating clusters termed glial scars. Together the cyst and scars pose a formidable barrier to any cut axons that might somehow try to regrow and connect to cells they once innervated. A few axons may remain whole, myelinated and able to carry signals up or down the spine, but often their numbers are too small to convey useful directives to the brain or muscles.

First, Contain the Damage If all these changes had to be fully reversed to help patients, the prospects for new treatments would be grim. Fortunately, it appears that salvaging normal activity in as little as 10 percent of the standard axon complement would sometimes make walking possible for people who would otherwise lack that capacity. In addition, lowering the level of injury by just a single segment (about half an inch) can make an important difference to a persons quality of life. People with a C6 injury have no power over their arms, save some ability to move their shoulders and flex their elbows. But individuals with a lower, C7 injury can move the shoulders and elbow joints and extend the wrists; with training and sometimes a tendon transfer, they can make some use of their arms and hands.

Because so much damage arises after the initial injury, clarifying how that secondary destruction occurs and blocking those processes are critical. The added wreckage has been found to result from many interacting mechanisms.

Within minutes of the trauma, small hemorrhages from broken blood vessels appear, and the spinal cord swells. The blood vessel damage and swelling prevent the normal delivery of nutrients and oxygen to cells, causing many of them to starve to death.

Meanwhile damaged cells, axons and blood vessels release toxic chemicals that go to work on intact neighboring cells. One of these chemicals in particular triggers a highly disruptive process known as excitotoxicity. In the healthy cord the end tips of many axons secrete minute amounts of glutamate. When this chemical binds to receptors on target neurons, it stimulates those cells to fire impulses. But when spinal neurons, axons or astrocytes are injured, they release a flood of glutamate. The high levels overexcite neighboring neurons, inducing them to admit waves of ions that then trigger a series of destructive events in the cellsincluding production of free radicals. These highly reactive molecules can attack membranes and other components of formerly healthy neurons and kill them.

Until about a year ago, such excitotoxicity, also seen after a stroke, was thought to be lethal to neurons alone, but new results suggest it kills oligodendrocytes (the myelin producers) as well. This effect may help explain why even unsevered axons become demyelinated, and thus unable to conduct impulses, after spinal cord trauma.

Prolonged inflammation, marked by an influx of certain immune system cells, can exacerbate these effects and last for days. Normally, immune cells stay in the blood, unable to enter tissues of the central nervous system. But they can flow in readily where blood vessels are damaged. As they and microglia become activated in response to an injury, the activated cells release still more free radicals and other toxic substances.

Methylprednisolone, the first drug found to limit spinal cord damage in humans, may act in part by reducing swelling, inflammation, the release of glutamate and the accumulation of free radicals. The precise details of how it helps patients remain unclear, however.

Studies of laboratory animals with damaged spinal cords indicate that drugs able to stop cells from responding to excess glutamate could minimize destruction as well. Agents that selectively block glutamate receptors of the so-called AMPA class, a kind abundant on oligodendrocytes and neurons, seem to be particularly effective at limiting the final extent of a lesion and the related disability. Certain AMPA receptor antagonists have already been tested in early human trials as a therapy for stroke, and related compounds could enter safety studies in patients with spinal cord injury within several years.

Much of the early cell loss in the injured spinal cord occurs by necrosis, a process in which cells essentially become passive victims of murder. In the past few years, neurobiologists have also documented a more active form of cell death, somewhat akin to suicide, in the cord. Days or weeks after the initial trauma, a wave of this cell suicide, or apoptosis, frequently sweeps through oligodendrocytes as many as four segments from the trauma site. This discovery, too, has opened new doors for protective therapy. Rats given apoptosisinhibiting drugs retained more ambulatory ability after a traumatic spinal cord injury than did untreated rats.

In the past few years, biologists have identified many substances, called neurotrophic factors, that also promote neuronal and glial cell survival. A related substance, GM-1 ganglioside (Sygen), is now being evaluated for limiting cord injury in humans. Ultimately, interventions for reducing secondary damage in the spinal cord will probably enlist a variety of drugs given at different times to thwart specific mechanisms of death in distinct cell populations.

The best therapy would not only reduce the extent of an injury but also repair damage. A key component of that repair would be stimulating the regeneration of damaged axonsthat is, inducing their elongation and reconnection with appropriate target cells.

Although neurons in the central nervous system of adult mammals generally fail to regenerate damaged axons, this lapse does not stem from an intrinsic property of those cells. Rather the fault lies with shortcomings in their environment. After all, neurons elsewhere in the body and in the immature spinal cord and brain regrow axons readily, and animal experiments have shown that the right environment can induce axons of the spinal cord to extend quite far.

Then, Induce Regeneration One shortcoming of the cord environment turns out to be an overabundance of molecules that actively inhibit axonal regenerationsome of them in myelin. The scientists who discovered these myelin-related inhibitors have produced a molecule named IN-1 (inhibitorneutralizing antibody) that blocks the action of those inhibitors. They have also demonstrated that infusion of mouse-derived IN-1 into the injured rat spinal cord can lead to long-distance regrowth of some interrupted axons. And when pathways controlling front paw activity are severed, treated animals regain some paw motion, whereas untreated animals do not. The rodent antibody would be destroyed by the human immune system, but workers are developing a humanized version for testing in people.

Many other inhibitory molecules have now been found as well, including some produced by astrocytes and a number that reside in the extracellular matrix (the scaffolding between cells). Given this array, it seems likely that combination therapies will be needed to counteract or shut down the production of multiple inhibitors at once.

Beyond removing the brakes on axonal regrowth, a powerful tactic would supply substances that actively promote axonal extension. The search for such factors began with studies of nervous system development. Decades ago scientists isolated nerve growth factor (NGF), a neurotrophic factor that supports the survival and development of the peripheral nervous system. Subsequently, this factor turned out to be part of a family of proteins that both enhance neuronal survival and favor the outgrowth of axons. Many other families of neurotrophic factors with similar talents have been identified as well. For instance, the molecule neurotrophin- 3 (NT-3) selectively encourages the growth of axons that descend into the spinal cord from the brain.

Luckily, adult neurons remain able to respond to axon-regenerating signals from such factors. Obviously, however, natural production of these substances falls far short of the amount needed for spinal cord repair. Indeed, manufacture of some of the compounds apparently declines, instead of rising, for weeks after a spinal trauma occurs. According to a host of animal studies, artificially raising those levels after an injury can enhance regeneration. Some regeneration- promoting neurotrophic factors, such as basic fibroblast growth factor, have been tested in stroke patients. None has been evaluated as an aid to regeneration in people with spinal cord damage, but many are being assessed in animals as a prelude to such studies.

Those considering neurotrophic factors for therapy will have to be sure that the agents do not increase pain, a common long-term complication of spinal cord injury. This pain has many causes, but one is the sprouting of nascent axons where they do not belong (perhaps in a failed attempt to address the injury) and their inappropriate connection to other cells. The brain sometimes misinterprets impulses traveling through those axons as pain signals. Neurotrophic factors can theoretically exacerbate that problem and can also cause pain circuits in the spiral cord and pain-sensing cells in the skin to become oversensitive.

After axons start growing, they will have to be guided to their proper targets, the cells to which they were originally wired. But how? In this case, too, studies of embryonic development have offered clues.

During development, growing axons are led to their eventual targets by molecules that act on the leading tip, or growth cone. In the past five years especially, a startling number of substances that participate in this process have been uncovered. Some, such as a group called netrins, are released or displayed by neurons or glial cells. They beckon axons to grow in some directions and repel growth in others. Additional guidance molecules are fixed components of the extracellular matrix. Certain of the matrix molecules bind well to specific molecules (cell adhesion molecules) on the growth cones and thus provide anchors for growing axons. During development, the required directional molecules are presented to the growth cones in specific sequences.

Establish Proper Connections At the moment, no one knows how to supply all the needed chemical road signs in the right places. But some findings suggest that regeneration may be aided by supplying just a subset of those targeting moleculessay, a selection of netrins and components from the extracellular matrix. Substances already in the spinal cord may well be capable of supplying the rest of the needed guidance.

A different targeting approach aims to bridge the gap created by cord damage. It directs injured axons toward their proper destinations by supplying a conduit through which they can travel or by providing another friendly scaffolding able to give physical support to the fibers as they try to traverse the normally impenetrable cyst. The scaffolding can also serve as a source of growth-promoting chemicals.

For instance, researchers have implanted tubes packed with Schwann cells into the gap where part of the spinal cord was removed in rodents. Schwann cells, which are glia of the peripheral nervous system, were chosen because they have many attributes that favor axonal regeneration. In animal experiments, such grafts spurred some axonal growth into the tubes.

A second bridging material consists of olfactory-ensheathing glial cells, which are found only in the tracts leading from the nose to the olfactory bulbs of the brain. When those cells were put into the rat spinal cord where descending tracts had been cut, the implants spurred partial regrowth of the axons over the implant. Transplanting the olfactory-ensheathing glia with Schwann cells led to still more extensive growth.

In theory, a biopsy could be performed to obtain the needed olfactory ensheathing glia from a patient. But once the properties that enable them (or other cells) to be competent escorts for growing axons are determined, researchers may instead be able to genetically alter other cell types if desired, giving them the required combinations of growthpromoting properties.

Fibroblasts (cells common in connective tissue and the skin) are among those already being engineered to serve as bridges. They have been altered to produce the neurotrophic molecule NT-3 and then transplanted into the cut spinal cord of rodents. The altered fibroblasts have resulted in partial regrowth of axons. Along with encouraging axonal regrowth, NT-3 stimulates remyelination. In these studies the genetically altered fibroblasts have enhanced myelination of regenerated axons and improved hind limb activity.

Replace Lost Cells Other transplantation schemes would implant cells that normally occur in the central nervous system. In addition to serving as bridges and potentially releasing proteins helpful for axonal regeneration, certain of these grafts might be able to replace cells that have died.

Transplantation of tissue from the fetal central nervous system has produced a number of exciting results in animals treated soon after a trauma. This immature tissue can give rise to new neurons, complete with axons that travel long distances into the recipients tissues (up and down several segments in the spinal cord or out to the periphery). It can also prompt host neurons to send regenerating axons into the implanted tissue. In addition, transplant recipients, unlike untreated animals, may recover some limb function, such as the ability to move the paw in useful ways. What is more, studies of fetal tissue implants suggest that axons can at times find appropriate targets even in the absence of externally supplied guidance molecules. The transplants, however, are far more effective in the immature spinal cord than in the injured adult cordan indication that young children would probably respond to such therapy much better than adolescents or adults would.

Some patients with long-term spinal cord injuries have received human fetal tissue transplants, but too little information is available so far for drawing any conclusions. In any case, application of fetal tissue technology in humans will almost surely be limited by ethical dilemmas and a lack of donor tissue. Therefore, other ways of achieving the same results will have to be devised. Among the alternatives is transplanting stem cells: immature cells that are capable of dividing endlessly, of making exact replicas of themselves and also of spawning a range of more specialized cell types.

Various kinds of stem cells have been identified, including ones that generate all the cell types in the blood system, the skin, or the spinal cord and brain. Stem cells found in the human adult central nervous system have, moreover, been shown capable of producing neurons and all their accompanying glia, although these so-called neural stem cells seem to be quiescent in most regions of the system. In 1998 a few laboratories also obtained much more versatile stem cells from human tissue. These human embryonic stem cells (in common with embryonic stem cells obtained previously from other vertebrates) can be grown in culture and, in theory, can yield almost all the cell types in the body, including those of the spinal cord.

Stem Cell Strategies How might stem cells aid in spinal cord repair? A great deal will be possible once biologists learn how to obtain those cells readily from a patient and how to control the cells differentiation. Notably, physicians might be able to withdraw neural stem cells from a patients brain or spinal cord, expand the numbers of the still undifferentiated cells in the laboratory and place the enlarged population in the same persons cord with no fear that the immune system will reject the implant as foreign. Or they might begin with frozen human embryonic stem cells, coax those cells to become precursors, or progenitors, of spinal cells and implant a large population of the precursors. Studies proposing to examine the effects on patients with spinal cord injuries of transplanting neural stem cells (isolated from the patients brains by biopsy) are being considered.

Simply implanting progenitor cells into the cord may be enough to prod them to multiply and differentiate into the needed lineages and thus to replace useful numbers of lost neurons and glial cells and establish the proper synaptic connections between neurons. Stem cells transplanted into the normal and injured nervous systems of animals can form neurons and glia appropriate for the region of transplantation. Combined with the fetal tissue results, this outcome signifies that many important cues for differentiation and targeting preexist in the injured nervous system. But if extra help is needed, scientists might be able to deliver it through genetic engineering. As a rule, to be genetically altered easily, cells have to be able to divide. Stem cells, unlike mature neurons, fit that bill.

Scenarios involving stem cell transplants are admittedly futuristic, but one day they themselves may become unnecessary, replaced by gene therapy alone. Delivery of genes into surviving cells in the spinal cord could enable those cells to manufacture and release a steady supply of proteins able to induce stem cell proliferation, to enhance cell differentiation and survival, and to promote axonal regeneration, guidance and remyelination. For now, though, technology for delivering genes to the central nervous system and for ensuring that the genes survive and work properly is still being refined.

Until, and even after, cell transplants and gene therapies become commonplace for coping with spinal cord injury, patients might gain help through a different avenuedrugs that restore signal conduction in axons quieted by demyelination. Ongoing clinical tests are evaluating the ability of a drug called 4-aminopyridine to compensate for demyelination. This agent temporarily blocks potassium ion channels in axonal membranes and, in so doing, allows axons to transmit electrical signals past zones of demyelination. Some patients receiving the drug have demonstrated modest improvement in sensory or motor function.

At first glance, this therapy might seem like a good way to treat multiple sclerosis, which destroys the myelin around axons of neurons in the central nervous system. Patients with this disease are prone to seizures, however, and 4-aminopyridine can exacerbate that tendency.

Neurotrophic factors, such as NT-3, that can stimulate remyelination of axons in animals could be considered for therapy as well. NT-3 is already entering extensive (phase III) trials in humans with spinal cord injury, though not to restore myelin. It will be administered by injection in amounts capable of acting on nerves in the gut and of enhancing bowel function, but the doses will be too low to yield high concentrations in the central nervous system. If the drug proves to be safe in this trial, though, that success could pave the way for human tests of doses large enough to enhance myelination or regeneration.

The Years Ahead Clearly, the 1990s have seen impressive advances in understanding of spinal cord injury and the controls on neuronal growth. Like axons inching toward their targets, a growing number of investigators are pushing their way through the envelope of discovery and generating a rational game plan for treating such damage. That approach will involve delivery of multiple therapies in an orderly sequence. Some treatments will combat secondary injury, some will encourage axonal regrowth or remyelination, and some will replace lost cells.

When will the new ideas become real treatments? We wish we had an answer. Drugs that work well in animals do not always prove useful in people, and those that show promise in small human trials do not always pan out when examined more extensively. It is nonetheless encouraging that at least two human trials are now under way and that others could start in the next several years.

Limiting an injury will be easier than reversing it, and so treatments for ameliorating the secondary damage that follows acute trauma can be expected to enter human testing most quickly. Of the repair strategies, promoting remyelination will be the simplest to accomplish, because all it demands is the recoating of intact axons. Remyelination strategies have the potential to produce meaningful recovery of function, such as returning control over the bladder or bowel abilities that uninjured people take for granted but that would mean the world to those with spinal cord injuries.

Of course, tendon-transfer surgery and advanced electrical devices can already restore important functions in some patients. Yet for many people, a return of independence in daily activities will depend on reconstruction of damaged tissue through the regrowth of injured axons and the reconnection of disrupted pathways.

So far, few interventions in animals with well-established spinal cord injuries have achieved the magnitude of regrowth and synapse formation that would be needed to provide a hand grasp or the ability to stand and walk in human adults with long-term damage. Because of the great complexities and difficulties involved in those aspects of cord repair, we cannot guess when reconstructive therapies might begin to become available. But we anticipate continued progress toward that end.

Traditionally, medical care for patients with spinal cord injury has emphasized compensatory strategies that maximize use of any residual cord function. That focus is now expanding, as treatments designed to repair the damaged cord and restore lost functionscience fiction only a decade agoare becoming increasingly plausible.

See original here:
Repairing the Damaged Spinal Cord - Scientific American

Biol Res 45: 279-287, 2012

RESEARCH ARTICLES

In Osteoporosis, differentiation of mesenchymal stem cells (MSCs) improves bone marrow adipogenesis

Ana Mara Pino1, Clifford J. Rosen2 and J. Pablo Rodrguez1*

1Laboratorio de Biologa Celular y Molecular, INTA, Universidad de Chile, 2Maine Medical Center Research Institute, Scarborough, Maine, USA.

ABSTRACT

The formation, maintenance, and repair of bone tissue involve close interlinks between two stem cell types housed in the bone marrow: the hematologic stem cell originating osteoclasts and mesenchymal stromal cells (MSCs) generating osteoblasts. In this review, we consider malfunctioning of MSCs as essential for osteoporosis. In osteoporosis, increased bone fragility and susceptibility to fractures result from increased osteoclastogenesis and insufficient osteoblastogenesis.

MSCs are the common precursors for both osteoblasts and adipocytes, among other cell types. MSCs' commitment towards either the osteoblast or adipocyte lineages depends on suitable regulatory factors activating lineage-specific transcriptional regulators. In osteoporosis, the reciprocal balance between the two differentiation pathways is altered, facilitating adipose accretion in bone marrow at the expense of osteoblast formation; suggesting that under this condition MSCs activity and their microenvironment may be disturbed. We summarize research on the properties of MSCs isolated from the bone marrow of control and osteoporotic post-menopausal women. Our observations indicate that intrinsic properties of MSCs are disturbed in osteoporosis. Moreover, we found that the regulatory conditions in the bone marrow fluid of control and osteoporotic patients are significantly different. These conclusions should be relevant for the use of MSCs in therapeutic applications.

Key words: MSCs, osteoporosis, adipogenesis, bone marrow microenvironment

BACKGROUND

The formation, maintenance, and repair of bone tissue depend on fine-tuned interlinks in the activities of cells derived from two stem cell types housed in the bone marrow interstice. A hematologic stem cell originates osteoclasts, whereas osteoblasts derive from mesenchymal stem cells (MSCs). Bone tissue is engaged in an unceasing process of remodelling through the turnover and replacement of the matrix: while osteoblasts deposit new bone matrix, osteoclasts degrade the old one.

Bone marrow provides an environment for maintaining bone homeostasis. The functional relationship among the different cells found in bone marrow generates a distinctive microenvironment via locally produced soluble factors, the extracellular matrix components, and systemic factors (Raisz, 2005; Sambrook and Cooper, 2006), allowing for autocrine, paracrine and endocrine activities. If only the main cellular components of the marrow stroma are considered, the activity of adipocytes, macrophages, fibroblasts, hematopoietic, endothelial and mesenchymal stem cells and their progeny bring about a complex range of signals.

Osteoporosis is a bone disease characterized by both decreased bone quality and mineral density. In postmenopausal osteoporosis, increased bone fragility and susceptibility to fractures result from increased osteoclastogenesis, inadequate osteoblastogenesis and altered bone microarchitecture.

The pathogenesis of the disease is hitherto unknown, hence the interest in basic and clinical research on the mechanisms involved (Raisz, 2005; Sambrook and Cooper, 2006). Cell studies on the origin of postmenopausal osteoporosis initially focused on osteoclastic activity and bone resorption processes; then on osteoblastogenesis, and more recently on the differentiation potential of mesenchymal stem cells (MSCs) (Shoback, 2007). Moreover, distinctive environmental bone marrow conditions appear to provide support for the development and maintenance of unbalanced bone formation and resorption (Nuttall and Gimble, 2004; Tontonoz et al., 1994). In this review, we consider the participation of the differentiation potential of MSCs, the activity of bone marrow adipocytes and the generation of a distinctive bone marrow microenvironment.

MESENCHYMAL STEM CELLS (MSCs)

Bone marrow contains stem-like cells that are precursors of nonhematopoietic tissues. These cells were initially referred to as plastic-adherent cells or colony forming-unit fibroblasts and subsequently as either mesenchymal stem cells or marrow stromal cells (MSCs) (Minguell et al., 2001; Lindnera et al., 2010; Kolf et al., 2007). There is much interest in these cells because of their ability to serve as a feeder layer for the growth of hematopoietic stem cells, their multipotentiality for differentiation, and their possible use for both cell and gene therapy (Minguell et al., 2001; Kolf et al., 2007). Friedenstein et al. (1970) initially isolated MSCs by their adherence to tissue culture surfaces, and essentially the same protocol has been used by other investigators. The isolated cells were shown to be multipotential in their ability to differentiate in culture or after implantation in vivo, giving rise to osteoblasts, chondrocytes, adipocytes, and/or myocytes.

MSCs populations in the bone marrow or those that are isolated and maintained in culture are not homogenous, but rather consist of a mixture of uncommitted, partially committed and committed progenitors exhibiting divergent stemness (Baksh et al., 2004). These heterogeneous precursor cells are morphologically similar to the multipotent mesenchymal stem cells, but differ in their gene transcription range (Baksh et al., 2004). It has been proposed that in such populations, cell proliferation, differentiation and maturation are in principle independent; stem cells divide without maturation, while cells close to functional competence may mature, but do not divide (Song et al., 2006).

Several molecular markers identify committed progenitors and the end-stage phenotypes, but at present there are no reliable cell markers to identify the uncommitted mesenchymal stem cells. Given the difficulty to identify a single marker to evaluate the population of stem cells, various combinations of these markers may be used (Seo et al., 2004; Lin et al., 2008; Xu et al., 2009). Therefore, MSCs are mainly defined in terms of their functional capabilities: self-renewal, multipotential differentiation and transdifferentiation (Baksh et al., 2004).

Hypothetically, the fate of MSCs appears to be determined during very early stages of cell differentiation ("commitment"). During this mostly unknown period, both intrinsic (genetic) and environmental (local and/or systemic) conditions interplay to outline the cell's fate towards one of the possible lineages. Based on microarray assays comparing gene expression at the stem state and throughout differentiation, it has been proposed that MSCs multilineage differentiation involves a selective mode of gene expression (Baksh et al., 2004; Song et al., 2006). It appears that "stemness" is characterized by promiscuous gene expression, where pluripotential differentiation results from the maintenance of thousands of genes at their intermediate expression levels. Upon commitment to one fate, only the few genes that are needed for differentiation towards the target tissue are selected for continuous expression, while the rest are downregulated (Zipori, 2005; Zipori, 2006).

The gene expression profile of undifferentiated human MSCs (h-MSCs) show high expression of several genes (Song et al., 2006; Tremain et al., 2001), but the contribution of such genes in preserving h-MSC properties, such as self-renewal and multilineage differentiation potential, or in regulating essential signalling pathways is largely unknown (Song et al., 2006). Several factors like age (Zhou et al., 2008), culture condition (Kultere et al., 2007), microenvironment (Kuhn and Tuan, 2010), mechanical strain (McBride et al., 2008) and some pathologies (Seebach et al., 2007; Hofer et al., 2010) appear to affect MSCs' intrinsic activity.

MSCs' commitment towards either the osteoblast or adipocyte lineage is determined by a combination of regulatory factors in the cells' microenvironment. The adequate combination leads to the activation of lineage-specific transcriptional regulators, including Runx2, Dlx5, and osterix for osteoblasts, and PPARy2 and a family of CAAT enhancer binding proteins for adipocytes (Murunganandan et al., 2009). Although the appropriate collection of regulatory factors required for suitable differentiation of MSCs is largely unknown, the TGF/BMPs, Wnt and IGF-I signals are briefly considered.

Several components of the BMP family are secreted in the MSCs' microenvironment (Lou et al., 1999, Gori et al., 1999; Gimble et al., 1995); BMP-2/4/6/7 have been identified as mediators for MSCs differentiation into osteoblasts or adipocytes (Muruganadan et al., 2009). The intracellular effects of BMPs are mediated by an interaction with cell surface BMP receptors (BMPRs type I and type II) (Gimble et al., 1995). It seems that differentiation into adipocytes or osteoblasts is highly dependent on the type of receptor I expressed by the cells, so that adipogenic differentiation requires signaling through BMPR IA, while osteogenic differentiation is dependent on BMPR IB activation (Gimble et al., 1995). The active receptors trigger the activation of Smad proteins, which induce specific genes. Under osteogenic differentiation, BMP action promotes osterix formation through Runx2-dependent and Runx2-independent pathways, thereby triggering osteogenic differentiation (Gori et al., 1999; Shapiro, 1999).

In addition to the role of BMPs in bone formation, BMPs also positively mediate the adipogenic differentiation pathways (Haiyan et al., 2009). It has been demonstrated that there is a binding site for Smad proteins in the promoter region of PPARy2 (Lecka-Czernik et al., 1999), and over-expression of Smad2 protein suppresses the expression of Runx2 (Li et al., 1998). These observations suggest that adequate content of osteoblasts and adipocytes in the bone marrow is dependent on balanced signaling through this pathway. Moreover, considering the distinct role assigned to BMPRIA and BMPRIB, the temporal gain or loss of a subtype of BMP receptors by MSCs could be critical for commitment and subsequent differentiation (Gimble et al., 1995144).

Wnt signaling in MSCs is also decisive for the reciprocal relationship among the osteo/adipogenic pathways. Activation of the Wnt/p-catenin pathway directs MSCs differentiation towards osteoblasts instead of adipocytes (Bennett et al., 2005; Ross et al., 2000; Moldes et al., 2003). Animal studies have shown that activation of the Wnt signaling pathway increases bone mass, preventing both hormone-dependent and age-induced bone loss (Bennett et al., 2005). Furthermore, Wnt activation may control cell commitment towards osteoblasts by blocking adipogenesis through the inhibition of the expression of both C/EBP and PPARy adipogenic transcription factors, as demonstrated in vivo in humans (Qiu et al., 2007), in transgenic mice expressing Wnt 10b (Bennett et al., 2005) and in vitro (Rawadi et al., 2003). MSCs' self-renewing and maintenance of the undifferentiated state appear to be dependent on appropriate canonical Wnt signaling, promoting increased proliferation and decreased apoptosis (Boland et al., 2004; Cho et al., 2006). The overexpression of LRP5, an essential co-receptor specifically involved in canonical Wnt signaling, has been reported to increase proliferation of MSCs (Krishnan et al., 2006). In addition, disruption in vivo or in vitro of -catenin signaling promoted spontaneous conversion of various cell types into adipocytes (Bennett et al., 2002). Moreover, the importance of this pathway for bone mineral density has been highlighted by the observation that genetic variations at either the LRP5 or Wnt10b gene locus are associated with osteoporosis (Brixen et al., 2007; Usui et al., 2007).

Also, insulin-like growth factor-I (IGF-I) signalling is clearly an important factor in skeletal development. The IGF regulatory system consists of IGFs (IGF-I and IGF-II), Type I and Type II IGF receptors, and regulatory proteins including IGF-binding proteins (IGFBP-1-6) and the acid-labile subunit (ALS) (Rosen et al., 1994). The ligands in this system (i.e. IGFs) are potent mitogens, and in some circumstances differentiation factors, that are bound in the circulation and interstitial fluid as binary (to IGFBPs) or ternary complexes (IGF-ALS-IGFBP-3 or -5) with little free IGF-I or -II. IGF bio-availability is regulated by the interaction of these molecules at the receptor level; hence changes in any component of the system will have profound effects on the biologic activity of the ligand. The IGFBPs have a particularly important role in regulating IGF-I access to its receptor, since their binding affinity exceeds that of the IGF receptors. The IGF system is unique because the IGFBPs are regulated in a cell-specific manner at the pericellular microenvironment, such that small changes in their concentrations could strongly influence the mitogenic activity of IGF-I (Jones and Clemmons, 1995; Hwa and Rosenfeld, 1999; Firth and Baxter, 2002). IGFs are expressed virtually by all tissues, and circulate in high concentrations. Although nearly 80% of the circulating IGF-I comes from hepatic sources, both bone and fat synthesize IGF-I and these tissues contribute to the total circulating pool. Locally produced IGF-I predominates over circulating IGF-I in maintaining skeletal integrity (Rosen et al., 1994; Kawai and Rosen, 2010), and both ALS and IGFBP-3 participate in regulating bone function. However, the possible autocrine/paracrine roles of IGF-I and IGFBPs in marrow (Liu et al., 1993; Peng et al., 2003) or in osteoblast (Zhao et al., 2000; Zhang et al., 2002; Wang et al., 2007) are practically unknown.

RELATIONSHIP BETWEEN THE OSTEO- / ADIPOGENESIS PROCESSES - THE FAT THEORY FOR OSTEOPOROSIS

Since in the bone marrow MSCs are the common precursor cells for osteoblast and adipocytes, adequate osteoblast formation requires diminished adipogenesis. As pointed out above, MSCs commitment and differentiation into a specific phenotype depends on hormonal and local factors (paracrine/autocrine) regulating the expression and/or activity of master differentiation genes (Nuttall and Gimble, 2004; Muruganadan et al., 2009) (Figure 1). A reciprocal relationship has been postulated to exist between the two differentiation pathways whose alteration would facilitate adipose accretion in the bone marrow, at the expense of osteoblast formation, thus decreasing bone mass (Reviewed in Rosen et, al 2009; Rodrguez et al.. 2008; Rosen and Bouxtein, 2006). Such unbalanced conditions prevail in the bone marrow of osteoporosis patients, upsetting MSC activity and the microenvironment (Nuttall and Gimble, 2004; Moerman et al., 2004; Rosen and Bouxtein, 2006). This proposition is known as the fat theory for osteoporosis. Moreover, this alteration of osteo-/adipogenic processes is also observed in other conditions characterized by bone loss, such as aging, immobilization, microgravity, ovariectomy, diabetes, and glucocorticoid or tiazolidindione treatments, highlighting the harmful consequence of marrow adipogenesis in osteogenic disorders (Wronski et al., 1986; Moerman et al., 2004; Zayzafon et al., 2004; Forsen et al., 1999).

Cell studies comparing the differentiation potential of MSCs derived from osteoporotic patients (o-MSCs) with that of control MSCs (c-MSCs) have shown unbalanced osteogenic/adipogenic processes, including increased adipose cell formation, counterbalanced by reduced production of osteogenic cells (Nuttall and Gimble, 2004; Rodrguez et al., 2008; Rosen and Bouxtein, 2006). Further research on MSC differentiation has shown that activation of PPARy2, a master transcription factor of adipogenic differentiation, positively regulates adipocyte differentiation while acting as a dominant negative regulator of osteogenic differentiation (Lecka-Czernik et al., 1999; Jeon et al., 2003; Khan and Abu-Amer, 2003). In contrast, an increase in bone mass density was observed in a PPARy deficient mice model; even the heterozygous deficient animals showed high bone mass and increased osteoblastogenesis (Cock et al., 2004). On the other hand, Runx2 expression by MSCs inhibits their differentiation into adipocytes, as may be concluded from experiments in Runx2-/- calvarial cells, which spontaneously differentiate into adipocytes (Kobayashi et al., 2000).

In vivo observations further support the fat theory. Early studies observed that osteoporosis was strongly associated with bone marrow adipogenesis. Iliac crest biopsies showed that bone marrow from osteoporotic patients had a considerable accumulation of adipocytes in relation to that of healthy elderly women (Moerman et al., 2004; Meunier et al., 1971). More recently, increased bone marrow adiposity measured by in vivo proton magnetic resonance (1H-MRS) has been associated with decreased bone mineral density in patients with low bone density (Griffith et al., 2005; Yeung et al., 2005; Blake et al., 2008).

In newborn mammals there is no marrow fat; however the number of adipocytes increases with age such that in humans over 30 years of age, most of the femoral cavity is occupied by adipose tissue (Moore and Dawson, 1990). The function of marrow fat is largely unknown; in humans it was first considered to be 'filler' for the void left by trabecular bone during aging or after radiation. Later, these cells have been proposed to have a role as an energy source, or as modulators of adjacent tissue by the production of paracrine, and autocrine factors (reviewed in Rosen et al., 2009). In fact, adipokines, steroids, and cytokines (Lee et al., 2002; Pino et al., 2010; Rosen et al., 2009;) can exert profound effects on neighboring marrow cells, sustaining or suppressing hematopoietic and osteogenic processes (Omatsu et al., 2010; Krings et al., 2012; Rosen et al., 2009; Rodrguez et al., 2008).

Thus, the function of bone marrow adipose tissue may be similar to that of extra medullary fat. As such, it has been well established that unbalanced production of signaling products from subcutaneous or visceral fat modulates several human conditions including obesity, lipodystrophy, atherogenesis, diabetes and inflammation. Recent studies in mice, suggest a complex fat phenotype in the bone marrow, presenting mixed brown and white adipose properties (Lecka-Czernik, 2012). Further work is needed to find out whether differences in the quality or quantity of marrow fat, take part in deregulated bone remodelling in some bone diseases.

STUDIES ON THE ACTIVITY OF OSTEOPOROTIC MSCs

Because of their ability to self-renew, human MSCs can be expanded and differentiated in vitro, offering many perspectives for tissue engineering and regenerative medicine approaches. However, there is scarce information on whether specific diseases affect the properties of MSCs, because of the difficult accessibility to human bone marrow in health and disease (Cipriani et al., 2011; Corey et al., 2007).

Our research has focused on the properties of MSCs isolated from bone marrow of control and osteoporotic post-menopausal women. We grouped our observations on functional characteristics of o-MSCs and c- MSCs in three categories, which are summarized in Table I, as follows:

General activities: h-MSCs isolated from osteoporotic and control donors have similar CFU-F, but different proliferation rates. O-MSCs showed significantly diminished proliferation rate and decreased mitogenic response to IGF-I. The pERK/ERK ratio is increased in o-MSCs, compared with control c-MSCs. In other cell types, activation of the MEK/ERK signalling pathway enhances the activity of adipogenic transcription factors (Prusty et al., 2002). We also observed decreased TGF- production by o-MSCs, as well as decreased capacity to generate and maintain a type I collagen-rich extracellular matrix, both conditions supporting cell differentiation into the adipocyte phenotype. Then, considering that the lineage fate of MSCs is dependent on early activation by specific BMPs, PPARy and Wnt signaling (Ross et al., 2000; Rawadi et al., 2003; Westendorf et al., 2004; Baron and Rawadi, 2007), we compared the expression level of some genes related to these pathways in c- and o- MSCs. Results obtained by RT-PCR showed that in c- and o-MSCs the expression level of mRNA for -catenin, Dkk-1, and BMPRIB was similar; while the level of mRNA for Wnt 3a was undetectable in both types of samples. The expression level of mRNA for GSK-3p, LRP6 and Osx was lower in o-MSCs than in c-MSCs, while the mRNA level for Ror2, Wnt 5a, BMPRIA showed doubtful. To further quantify the expression level of GSK-3P, LRP6, Osx, Ror2, Wnt 5a, BMPRIA real time RT-PCR was performed. As shown in Table I, statistically significant decreased mRNA levels for GSK-3p, LRP6 and Osx (0.64, 0.26 and 0.18 fold, respectively) were observed in o-MSCs, as compared to c-MSCs. In addition, mRNA levels for Ror2, Wnt 5a, and BMPRIA were similar in both types of cell samples.

These data suggest impaired regulation by the BMPs and Wnt pathways in o-MSCs, representing some intrinsic deviation from control cells that might underlie the impaired self-renewal, and adipogenic/osteogenic differentiation potential observed in o-MSCs. mRNA levels for Ror2, Wnt 5a, and BMPRIA were similar in both types of cell samples.

STUDIES ON THE ACTIVITY OF BONE MARROW FLUID OF POST-MENOPAUSAL WOMEN

Distinctive environmental bone marrow conditions appear to support the development and maintenance of the balance between bone resorption and bone formation. Knowledge is scarce about the intramedullar concentration of compounds with recognized regulatory effects on bone formation or resorption and is limited to some pathologic conditions or estimated from measurements in plasma (Wiig et al., 2004; Iversen and Wiig, 2005; Lee et al., 2002; Khosla et al., 1994).

Measurement of soluble molecules found in human bone marrow has been particularly difficult, not only because of tissue seclusion, but also because of the complicated anatomy and blood perfusion of bone. Since it may be expected that concentrations measured in the bone marrow fluid (BMF) more reliably reflect the physiologically relevant levels in the interstitial compartment surrounding the bone cells than values found in blood, we isolated the extracellular bone marrow fluid by directly spinning bone marrow samples for 20 min at 900xg. Considering the complex organization in such a regulatory milieu, we opted for evaluating some molecules recognized as markers of adipocyte, proinflammatory or osteoclastic/osteoblastic activity (Pino et al., 2010).

The concentrations of cytokines or receptors measured in the bone marrow extracellular fluid from control and osteoporotic human donors are indicated in Table II. In addition, the concentrations of IGF-I and its IGFBPs were analyzed, as well as the C-terminal telopeptide cross-links of type I collagen (CTX). Results summarized in Table II indicate significantly different concentrations of regulatory molecules in the extracellular fluid of control versus osteoporotic women; this last group was characterized by higher content of proinflammatory and adipogenic cytokines. Also, osteoporotic samples showed decreased leptin bioavailability, suggesting that insufficient leptin action may characterize the osteoporotic bone marrow (Pino et al., 2010). In addition, bioavailability of IGF-I appears diminished in o-BMF, as shown by the increased IGFBP3/IGF-I ratio.

TABLE II

Regulatory activity in bone marrow fluid of post-menopausal women

Taken together our results and those of other researchers identify significant differences between functional properties of control and osteoporotic MSCs, displayed in vitro, in cells under basal or differentiating conditions. Moreover, it can be concluded that such divergence prevails also in vivo, because the bone marrow fluid of osteoporotic patients characterizes by unfavourable content of several regulatory molecules. Therefore, the properties of both MSCs and bone marrow microenvironment are significantly impaired in osteoporotic patients, negatively affecting bone formation.

CONCLUSIONS

In the pathogenesis of osteoporosis, impairment of both MSCs functionality and microenvironment add to the known detrimental effect of increased osteoclast activity, resulting in decreased bone formation.

O-MSCs are characterized by intrinsic functional alteration leading to poor osteogenic capability and increased adipogenesis. Osteoporotic bone marrow microenvironment differs from the control microenvironment by increased concentration of pro-adipogenic and pro-inflammatory regulatory factors.

The content and/or quality of adipocytes in the bone marrow appear critical to delineate impairing of MSCs; in this sense osteoporosis could be homologated to other age-related diseases such as obesity, atherogenesis and diabetes, which are characterized by extramedullar unbalanced adipocyte formation and signaling.

Currently it is not known how damaged o-MSCs emerge, further work is needed to ascertain the role of the microenvironment, and genetic and epigenetic factors, as proposed for other stem cells-related pathologies.

The conclusion that intrinsic properties of MSCs are altered in osteoporosis should be relevant for the therapeutic use of MSCs, which represent an interesting promise for regenerative medicine for several severe human diseases.

The possibility of reversing o-MSCs impairment opens new perspectives for osteoporosis therapy.

ACKNOWLEDGEMENTS

We thank Dr. Mariana Cifuentes for her critical review of the manuscript and valuable comments. This work was supported by a grant from the Fondo Nacional de Ciencia y Tecnologa (FONDECYT # 1090093)

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In Osteoporosis, differentiation of mesenchymal stem cells ...

Skin transplantation could be an effective way to deliver gene therapy to treat type 2 diabetes and obesity, new research in mice suggests.

The technique could enable a wide range of gene-based therapies to treat many human diseases.

We think this can provide a long-term safe option for the treatment of many diseases

We resolved some technical hurdles and designed a mouse-to-mouse skin transplantation model in animals with intact immune systems, says study author Xiaoyang Wu, assistant professor in the cancer research department at the University of Chicago.

We think this platform has the potential to lead to safe and durable gene therapy in mice and, we hope, in humans, using selected and modified cells from skin.

Beginning in the 1970s, physicians learned how to harvest skin stem cells from a patient with extensive burn wounds, grow them in the laboratory, then apply the lab-grown tissue to close and protect a patients wounds. This approach is now standard. However, the application of skin transplants is better developed in humans than in mice.

The mouse system is less mature, Wu says. It took us a few years to optimize our 3D skin organoid culture system.

This study is the first to show that an engineered skin graft can survive long term in wild-type mice with intact immune systems.

We have a better than 80 percent success rate with skin transplantation, Wu says. This is exciting for us.

The researchers focused on diabetes because it is a common non-skin disease that can be treated by the strategic delivery of specific proteins.

They inserted the gene for glucagon-like peptide 1 (GLP1), a hormone that stimulates the pancreas to secrete insulin. This extra insulin removes excessive glucose from the bloodstream, preventing the complications of diabetes. GLP1 can also delay gastric emptying and reduce appetite.

Using CRISPR, a tool for precise genetic engineering, they modified the GLP1 gene. They inserted one mutation, designed to extend the hormones half-life in the blood stream, and fused the modified gene to an antibody fragment so that it would circulate in the blood stream longer. They also attached an inducible promoter, which enabled them to turn on the gene to make more GLP1, as needed, by exposing it to the antibiotic doxycycline. Then they inserted the gene into skin cells and grew those cells in culture.

When these cultured cells were exposed to an air/liquid interface in the laboratory, they stratified, generating what the authors referred to as a multi-layered, skin-like organoid.

Next, they grafted this lab-grown gene-altered skin onto mice with intact immune systems. There was no significant rejection of the transplanted skin grafts.

When the mice ate food containing minute amounts of doxycycline, they released dose-dependent levels of GLP1 into the blood. This promptly increased blood-insulin levels and reduced blood-glucose levels.

When the researchers fed normal or gene-altered mice a high-fat diet, both groups rapidly gained weight. They became obese. When normal and gene-altered mice got the high-fat diet along with varying levels of doxycycline, to induce GLP1 release, the normal mice grew fat and mice expressing GLP1 showed less weight gain.

Expression of GLP1 also lowered glucose levels and reduced insulin resistance.

Together, our data strongly suggest that cutaneous gene therapy with inducible expression of GLP1 can be used for the treatment and prevention of diet-induced obesity and pathologies, the authors write.

When they transplanted gene-altered human cells to mice with a limited immune system, they saw the same effect. These results, the authors wrote, suggest that cutaneous gene therapy for GLP1 secretion could be practical and clinically relevant.

This approach, combining precise genome editing in vitro with effective application of engineered cells in vivo, could provide significant benefits for the treatment of many human diseases, the authors note.

We think this can provide a long-term safe option for the treatment of many diseases, Wu says. It could be used to deliver therapeutic proteins, replacing missing proteins for people with a genetic defect, such as hemophilia. Or it could function as a metabolic sink, removing various toxins.

Skin progenitor cells have several unique advantages that are a perfect fit for gene therapy. Human skin is the largest and most accessible organ in the body. It is easy to monitor. Transplanted skin can be quickly removed if necessary. Skins cells rapidly proliferate in culture and can be easily transplanted. The procedure is safe, minimally invasive, and inexpensive.

There is also a need. More than 100 million US adults have either diabetes (30.3 million) or prediabetes (84.1 million), according the Centers for Disease Control and Prevention. More than two out of three adults are overweight. More than one out of three are considered obese.

Additional authors of the study are from the University of Chicago and the University of Illinois at Chicago. The National Institutes of Health, the American Cancer Society, and the V Foundation funded the study.

Source: University of Chicago

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Skin transplants could treat diabetes and obesity - Futurity - Futurity: Research News

A University of Chicago-based research team has overcome challenges that have limited gene therapy and demonstrated how their novel approach with skin transplantation could enable a wide range of gene-based therapies to treat many human diseases.

In a study inthe journal Cell Stem Cell, the researchers provide proof-of-concept. They describe gene-therapy administered through skin transplants to treat two related and extremely common human ailments: Type 2 diabetes and obesity.

We resolved some technical hurdles and designed a mouse-to-mouse skin transplantation model in animals with intact immune systems, said study author Xiaoyang Wu, assistant professor in the Ben May Department for Cancer Research at the University of Chicago. We think this platform has the potential to lead to safe and durable gene therapy in mice and, we hope, in humans, using selected and modified cells from skin.

Beginning in the 1970s, physicians learned how to harvest skin stem cells from a patient with extensive burn wounds, grow them in the laboratory, then apply the lab-grown tissue to close and protect a patients wounds. This approach is now standard. However, the application of skin transplants is better developed in humans than in mice.

The mouse system is less mature, Wu said. It took us a few years to optimize our 3-D skin organoid culture system.

This study is the first to show that an engineered skin graft can survive long term in wild-type mice with intact immune systems. We have a better than 80 percent success rate with skin transplantation, Wu said. This is exciting for us.

The researchers focused on diabetes because it is a common non-skin disease that can be treated by the strategic delivery of specific proteins.

They inserted the gene for glucagon-like peptide 1 (GLP1), a hormone that stimulates the pancreas to secrete insulin. This extra insulin removes excessive glucose from the bloodstream, preventing the complications of diabetes. GLP1 can also delay gastric emptying and reduce appetite.

Using CRISPR, a tool for precise genetic engineering, they modified the GLP1 gene. They inserted one mutation, designed to extend the hormones half-life in the blood stream, and fused the modified gene to an antibody fragment so that it would circulate in the blood stream longer. They also attached an inducible promoter, which enabled them to turn on the gene to make more GLP1, as needed, by exposing it to the antibiotic doxycycline. Then they inserted the gene into skin cells and grew those cells in culture.

When these cultured cells were exposed to an air/liquid interface in the laboratory, they stratified, generating what the authors referred to as a multi-layered, skin-like organoid. Next, they grafted this lab-grown gene-altered skin onto mice with intact immune systems. There was no significant rejection of the transplanted skin grafts.

When the mice ate food containing minute amounts of doxycycline, they released dose-dependent levels of GLP1 into the blood. This promptly increased blood-insulin levels and reduced blood-glucose levels.

When the researchers fed normal or gene-altered mice a high-fat diet, both groups rapidly gained weight. They became obese. When normal and gene-altered mice got the high-fat diet along with varying levels of doxycycline, to induce GLP1 release, the normal mice grew fat and mice expressing GLP1 showed less weight gain.

Expression of GLP1 also lowered glucose levels and reduced insulin resistance.

Together, our data strongly suggest that cutaneous gene therapy with inducible expression of GLP1 can be used for the treatment and prevention of diet-induced obesity and pathologies, the authors wrote.

When they transplanted gene-altered human cells to mice with a limited immune system, they saw the same effect. These results, the authors wrote, suggest that cutaneous gene therapy for GLP1 secretion could be practical and clinically relevant.

This approach, combining precise genome editing in vitro with effective application of engineered cells in vivo, could provide significant benefits for the treatment of many human diseases, the authors note.

We think this can provide a long-term safe option for the treatment of many diseases, Wu said. It could be used to deliver therapeutic proteins, replacing missing proteins for people with a genetic defect, such as hemophilia. Or it could function as a metabolic sink, removing various toxins.

Skin progenitor cells have several unique advantages that are a perfect fit for gene therapy. Human skin is the largest and most accessible organ in the body. It is easy to monitor. Transplanted skin can be quickly removed if necessary. Skins cells rapidly proliferate in culture and can be easily transplanted. The procedure is safe, minimally invasive and inexpensive.

There is also a need. More than 100 million U.S. adults have either diabetes (30.3 million) or prediabetes (84.1 million), according the Centers for Disease Control and Prevention. More than two out of three adults are overweight. More than one out of three are considered obese.

Additional authors of the study were Japing Yue, Queen Gou, and Cynthia Li from the University of Chicago and Barton Wicksteed from the University of Illinois at Chicago. The National Institutes of Health, the American Cancer Society and the V Foundation funded the study.

Article originally appeared on Science Life.

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Gene therapy via skin could treat diseases such as obesity - UChicago News

By Jacqueline Howard CNN

(CNN) -- Scientists are getting one step closer to snipping inherited genetic diseases out of human offspring using a gene-editing technique called CRISPR.

For the first time, scientists said, they corrected a gene mutation linked to inherited heart conditions in human embryos using the approach. A study demonstrating the technique was published in the journal Nature on Wednesday (PDF).

Last week, the MIT Technology Review released the first news of this scientific feat, describing the research as the first-known attempt at creating genetically modified human embryos in the United States.

However, Juan Carlos Izpisua Belmonte, a co-author of the study, described it as the first in the world to demonstrate gene-editing to be safe, accurate and efficient in correcting a pathogenic gene mutation in human embryos. Previous attempts by Chinese researchers were unsuccessful at achieving this without safety concerns.

"This is the first that has been demonstrated as safe and working," said Belmonte, a professor at the Salk Institute for Biological Studies' gene expression laboratory in La Jolla, California.

"All cells of the embryo were corrected," he said. "It seems to be working from these samples that we have chosen, but we need to do much more basic research with many other genes."

The study was a collaboration between the Salk Institute, the Oregon Health & Science University in Portland and Korea's Institute for Basic Science.

Scientists estimate that more than 10,000 human diseases may result from mutations to a single gene occurring in all cells of the body, according to the World Health Organization.

Cutting and correcting gene mutations

The study used 75 human zygotes in which the father carried a mutation on the MYBPC3 gene, Belmonte said. The eggs used to produce the zygotes did not carry that gene mutation. The researchers noted that they received informed consent from the donors of the eggs, sperm and embryos used in the study.

The goal was to correct a type of inherited heart condition. A mutation called MYBPC3 is associated with inherited heart conditions, including left ventricular noncompaction, familial dilated cardiomyopathy and familial hypertrophic cardiomyopathy, which affects an estimated one in 500 people worldwide.

Hypertrophic cardiomyopathy also is thought to be the most common inherited or genetic heart disease in the US, according to the Centers for Disease Control and Prevention.

In a lab dish, the researchers used CRISPR, a gene-editing technique, to remove the harmful MYBPC3 mutation from the human zygotes. Then, the zygotes' own DNA-repair mechanism replaced what was cut out with a copy of a MYBPC3 gene from the mother, which did not carry a mutation, Belmonte said.

"A male research subject known to be heterozygous for this gene mutation was recruited for the study, as were several healthy young egg donors," Dr. Paula Amato, an obstetrician-gynecologist at Oregon Health & Science University, said Tuesday. She was a co-author of the study.

"CRISPR was introduced at the time of sperm injection," she said. "Then, DNA repair of the embryos was assessed."

The researchers found that about 72% of zygotes were properly and safely corrected on the MYBPC3 gene, Belmonte said.

This method significantly differed from studies in which scientists used the CRISPR tool to manually replace what was cut out with whatever the scientists desired.

Researchers in China were the first to reveal attempts to modify genes in human embryos using CRISPR. Three separate studies were published in scientific journals describing Chinese experiments on gene editing in human embryos.

"The previous human studies done in China had very small numbers, and one of them used abnormal embryos," Amato said. "So we think this is the first, largest study from which you could draw some reasonable conclusions."

Some gene-editing attempts in human embryos have been problematic, resulting in an issue called mosaicism, in which the corrections made in one gene failed to replicate once that cell divided into two cells, those two cells divided into four cells and so on.

"So when the baby is born, all the cells do not have the mutation anymore. ... This study, it shows that we can correct the embryo and then, after the division, all the cells are corrected, so there's not what we call mosaicism," said Belmonte, who is also a member of the National Academies of Sciences, Engineering and Medicine's committee on human gene editing.

This year, the academies published a report on human genome editing that addressed potential applications of the technology, including the possible prevention or treatment of inherited diseases or conditions.

The future of gene editing

Though the researchers have expressed enthusiasm around their new study, they also noted that the findings must be replicated in followup research before this gene-editing approach can move forward to clinical trials.

"The fact that it is, apparently, a new and poorly understood mechanism and it is not the now standard CRISPR 'cut and replace' method adds to the time needed for research into its safety and effectiveness," said Hank Greely, professor of law and genetics at Stanford University, who was not involved in the new study.

Yet future research can come with some political challenges, Amato said.

"First of all, there are regulations regarding use of federal funds for embryo research, so the (US National Institutes of Health) does not currently support embryo research, so that's one barrier. The other barrier is, the (US Food and Drug Administration) is prohibited from considering any clinical trials related to germline genetic modification," she said.

In this new study the embryos were only allowed to mature to day three after fertilization before they were disaggregated, or isolated into various components, for further analysis.

In the far-off future, a clinical trial could include transplanting corrected embryos into a uterus with the goal of establishing pregnancy and then monitoring the embryos as they develop into children.

Still, "it is way too early to contemplate implanting the edited embryos for the purpose of actually establishing a pregnancy," said Dana Carroll, a professor of biochemistry at the University of Utah who was not involved in the new study but has used CRISPR in his own research.

"The genome editing tools are currently not sufficiently efficient and specific to be reliable, and regulatory and oversight processes have not been established," Carroll said, adding that the work on the new study was "well-done" and "well-presented."

"The authors have made an important discovery regarding the repair of CRISPR-induced DNA breaks in human eggs just at the time of fertilization," he said.

"This information will help to guide ongoing research, and it demonstrates that research on early-stage human embryos will be necessary to establish safe and effective procedures in the long run," he said. "There is still a lot of work to do to understand repair processes in very early embryos and to optimize the use of the CRISPR reagents, but this study makes a valuable contribution."

Some CRISPR critics have argued that gene editing may give way to eugenics and to allowing embryos to be edited with certain features in order to develop so-called designer babies.

However, the researchers wrote in their study that they hope CRISPR could be considered as an alternative option to preimplantation genetic diagnosis, also known as PGD, for couples at risk of passing on an inherited disease.

'This opens up the possibility for those embryos'

PGD, developed about a quarter-century ago, is a genetic testing procedure typically conducted after in vitro fertilization to diagnose a genetic disease or condition in an embryo before it is implanted.

Since the human genome contains two copies of each gene -- paternal and maternal alleles, or variant forms of genes -- a mutation affecting only one allele is called heterozygous.

When only one parent carries a heterozygous mutation on a gene, about half of the embryos from that parent should be mutation-free while the others would have the mutation. Selectively, the parents' doctor would chose the healthy embryos to be implanted and discard the embryos with the mutations, Belmonte said.

Sometimes, "a couple that wants to have a baby and they have a mutation, they may not have enough embryos to choose from," he said. This is when CRISPR can come in.

"This technology, independent of the embryos that are there, it would go on and correct all of them. ... This opens up the possibility for those embryos," he said. "That's important because after the first implantation, if it doesn't work, you can do it again."

The researchers wrote in their study, "PGD may be a viable option for heterozygous couples at risk of producing affected offspring. In cases when only one parent carries a heterozygous mutation, 50% of embryos should be mutant. In contrast, targeted gene correction can potentially rescue a substantial portion of mutant human embryos, thus increasing the number of embryos available for transfer."

Nonetheless, using CRISPR in that way remains a long way off.

Shoukhrat Mitalipov, director of the Oregon Health & Science University's Center for Embryonic Cell and Gene Therapy, helped lead the new study. In 2013, Mitalipov and his colleagues reported the first success in cloning human stem cells, reprogramming human skin cells back to their embryonic state. In 2007, a research team led by Mitalipov announced that they created the first cloned monkey embryo and extracted stem cells from it.

Now, when it comes to using CRISPR to correct gene mutations in embryos, Mitalipov said Tuesday, "We've done some ground work. ... There is still a long road ahead, and it's unclear at this point when we will be allowed to move on."

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Stem Cell Research is an amazing field right now, and promises to be a powerful and potent tool to help us live longer and healthier lives. Just last month, for example, Stem Cell Therapy was used to restore sight in patients with severe retinal deterioration, allowing them to see clearer than they had in years, or even decades.

Now, there is another form of Stem Cell Treatment on the horizonthis one of a very different form. Stem Cells have now been used as a mechanism to deliver medical treatment designed to eliminate cancer cells, even in hard to reach places. One issue with current cancer treatments is that, treatments that are effective at treating tumors on the surface of the brain cannot be performed safely when the tumor is deeper within the brains tissues.

Stem Cells have the fantastic ability to transform into any other kind of cell within the human body, given the appropriate stimulation. As of today, most of these cells come from Embryonic Lines, but researchers are learning how to backwards engineer cells in the human body, reverting them back to their embryonic state. These cells are known as Induced Pluripotent Stem Cells.

How Does This Stem Cell Cancer Treatment Work?

Using genetic engineering, it is possible to create stem cells that are designed to release a chemical known as Pseudomonas Exotoxin, which has the ability to destroy certain tumor cells in the human brain.

What is Pseudomonas Exotoxin?

Pseudomonas Exotoxin is a compound that is naturally released by a form of bacteria known as Pseudomonas Aeruginosa. This chemical is toxic to brain tumor cells because it prevents polypeptides from growing longer, essentially preventing the polypeptides from growing and reproducing. When used in a specific manner, this toxin has the ability to destroy cancerous and malignant tissue without negatively impacting healthy tissue. In addition to its potential as a cancer treatment, there is also evidence that the therapy could be used for the treatment of Hepatitis B.

PE and Similar Toxins Have been Used Therapeutically in the Past

As of now, this chemical, which we will refer to for the rest of the article as PE, has been used as a cancer treatment before, but there are major limitations regarding the use of PE for particular cancers, not because of the risks of the treatment, but because of the lack of an effective method to deliver the medication to where it is needed.

For example, similar chemicals have been highly effective in the treatment of a large number of blood cancers, but havent been nearly as effective in larger, more inaccessible tumors. The chemicals break down or become metabolized before they can fully do their job.

How do Stem Cells Increase the Effectiveness of PE Cancer Treatment

Right now, PE has to be created in a laboratory before it is administered, which is not very effective for these embedded cancers. By using Stem Cells as an intermediary, it is possible to deliver the medication to deeper areas of the brain more effectively, theoretically highly increasing the efficacy of the treatment.

The leader of this Stem Cell Research is Harvard researcher Dr. Khalis Shah. His goal was to find an effective means to treat these deep brain tumors which are not easily treated by methods available today. In utilizing Stem Cells, Dr. Shah has potentially found a means by which the stem cells can constantly deliver this Cancer Toxin to the tumor area. The cells remain active and are fed by the body, which allows them to provide a steady stream of treatment that is impossible to provide via any other known method.

This research is still in its early stages, and has not yet reached human trials, but in mice, the PE Toxin worked exactly as hypothesized and was able to starve out tumors by preventing them from replicating effectively.

Perhaps this might seem a bit less complicated than it actually is. One of the major hurdles that had to be overcome was that this Toxin would normally be strong enough to kill the cell that hosted it. In order for the Stem Cells to release the cancer, they had to be able to withstand the effects of PE, themselves. Using genetic engineering, Dr. Shah and his associates were able to create a cell that is capable of both producing and withstanding the effects of the toxin.

Stem Cell delivered medical therapy is a 21st century form of medical treatment that researchers are just beginning to learn how to effectively utilize. Essentially, this treatment takes a stem cell and converts it into a unique symbiotic tool capable of feeding off of the host for energy in order to perform a potentially life-saving function. Its really quite fascinating.

How Does PE Not Damage or Kill Brain Cells Indiscriminately?

You might be concerned about the idea of a patient having a toxin injected into the brain to cure a disease. It sounds almost like a dangerous, tribal, homeopathic remedy. In reality, the researchers have been able to harness the destructive power of the toxin and re-engineer it so that it directly targets cancer cells while having limited negative effects on healthy, non-cancerous tissue.

The toxin does its damage after it has been absorbed by a cell. By retooling the toxin so that it does not readily absorb into healthy cells, the dangers associated with having such a potentially dangerous toxin in the brain are seriously and significantly mitigated.

Beyond that, Dr. Shah and his associates have been able to take steps to effectively turn off PE while it is inside the host stem cell, and only activates when it has entered the cancerous tissue. Dr. Shah explains that, although this research has only been conducted in animal subjects, there is no known reason why the effectiveness and safety of the treatment would not be applicable to human patients.

In this treatment, surgeons remove as much of the tumor as possible from the brain, and insert the engineered Stem Cells submerged in a sterile gel in the area where the tumor was removed or partially still exists. Researchers found that, when they used this treatment on laboratory rats, they could tell through imaging and analysis that the modified PE toxin effectively killed the cancer cells, and that this cancer treatment effectively lengthened the life of the rat, as compared to control subjects.

Whats the Next Step?

Of course, cancer treatment is far more complex than a single treatment, no matter how effective that treatment may be. Because human cancer treatment is a comprehensive therapy approach, the end goal of this research is to create a form of therapy in which the method used in animal subjects is combined with other existing approaches, increasing and maximizing the effectiveness of the comprehensive treatment.

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A recent change in how well we understand stem cells may make it easier for scientists and researchers to gather stem cells for use in scientific research as well as medical application. A new study was released in the research publication, Cell, which was performed by representatives from the University of California San Francisco.

One of the issues which hinder the use of stem cells as a more widespread treatment or field of research is that researchers and patients have a bottleneck of available healthy stem cell lines which can be used for research. Researchers hope that this new discovery will allow future scientific discoveries and applications in the areas of creating new and healthy tissue for patients with kidney failure or any other form of organ tissue failure. The future of medical therapy lies with Stem Cell Research, but many other forms of treatment, including Hormone Replacement Therapy, are already in practice today.

Researchers have discovered that it is possible to essentially flip a switch in an adult cell, reverting it back to the preliminary state at which cells existed in one of the earliest stages of developmentthe embryonic stem cell. Medical researchers hypothesize that Stem Cell treatments could be used for a variety of medical health issues which plague the world today, including kidney failure, liver disease, and Type-1 and Type-2 Diabetes.

Use of Embryonic Stem Cells Contentious

There is an ethical issue in Stem Cell Research today. Many Pro-Life Advocates are vociferously against the use of Embryonic Stem Cells harvested from procedures such as fertility treatments designed for conception. They believe that the use of embryonic stem cells harvested from donors and couples looking to conceive is unethical.

Using current research, it may be possible to bypass this ethical quandary completely by using adult cells and converting them into embryonic stem cells. Furthermore, because these stem cells are genetic derivatives of the patient from which the adult cells were harvested, this potentially paves the way for patient-specific medical treatments using stem cells.

After adult cells have been converted back into Embryonic Stem Cells, it will be possible to convert them into any possible cell that the patient needs or would benefit from.

Hijacking the Blueprint of the Cell Allows Scientists to Revert Adult Cells to their Earliest State

Researchers have increased the capacity to produce Embryonic Stem Cells by identifying previously unrecognized biochemical processes which tell human cells how to develop. In essence, researchers have discovered how the body blueprints cells, and can change the blueprints so that a new cell is made.

By utilizing these newly recognized pathways, it is possible to create new stem cells more quickly than ever before. One of the researchers explains the implications of this research. Dr. Miguel Ramalho-Santos is an associate professor of obstetrics, medicine, and cancer research at the University of California San Francisco. Dr. Ramalho-Santos is also a member of the Broad Center of Regenerative Medicine and Stem Cell Research.

He explains that these stem cell discoveries have the ability to alter the way that the medical sciences can take advantage of stem cells with regard to both cancer research and regenerative medicine. Dr. Ramalho-Santos was the lead researcher for this study, and the research was largely funded by the Director of the National Institutes of Health New Innovator Award, granted to promising young researchers which are leading highly innovative and promising medical research studies.

Dr. Ramalho-Santos research builds off of earlier research which discovered that it was possible to take adult cells and turn them back into embryonic stem cells. These stem cells dont have any inherent aging processes, and they can be turned into any other kind of tissue. In the process of this conversion, the adult cells lose all of their unique characteristics, leaving them in an ultimately immature and malleable state.

This earlier research was conducted by researchers from UC San Francisco in partnership with Dr. Shinya Yamanaka from Kyoto University and Gladstone Institutes. These entities all gained a piece of the Nobel Prize in Physiology or Medicine from their part in the study.

Pluripotent Stem Cells vs. Embryonic Stem Cells

Thus far, weve described these cells as Embryonic Stem Cells, but in fact, the more accurate term for these cells are Induced Pluripotent Stem Cells (IPS). These cells are biologically and functionally similar to Embryonic Stem Cells, but have a different name because they are sourced from adult cells. The difference between Induced Pluripotent Stem Cells and Embryonic Stem Cells is that Induced Pluripotent Stem Cells do seem to retain some of the characteristics of their previous state, which appears to limit their ability to convert into any other type of cell. This new research identifies new pathways by which it may be possible to increase the number of cells that an individual IPS Cell can turn into, perhaps allowing them to convert into any other kind of human cell.

Induced Pluripotent Stem Cells are not explicitly considered an alternative to Embryonic Stem Cells, but are considered a different approach to produce similar cells. If researchers fully uncover the mechanisms of how to reprogram these cells, it will lower many barriers to stem cell research and the availability of stem cell treatments.

As of today, researchers have figured out how to make these Induced Pluripotent Stem Cells, but the percentage of adult cells which are reverted successfully is quite low, and frequently, these cells still show some aspects of specialization, which limits their use.

How Do Scientists Make Stem Cells From Adult Cells?

There are genes within every cell which have the ability to induce pluripotency, reverting the cell to an earlier stage of specialization. The initial stage of this process is the result of activating Yamanaka Factors, specific genes that initiate this reversion process.

As of today, this process of de-maturation is not completely understood, and researchers realized from the start that the cells they created were not truly identical to Embryonic Stem Cells, because they still showed signs of their former lives, which often prevented them from being successfully reprogrammed.

The new research conducted by Dr. Ramalho-Santos appears to increase our knowledge regarding how these cells work, and how to program them more effectively. Dr. Ramalho-Santos and his team discovered more genes associated with these programming/reprogramming processes, and by manipulating them, they have increased the viability and range of particular stem cells.

It appears that these genetic impulses are constantly at play to maintain the structure and function of a cell, and that by systematically removing these safeguards, it is possible to increase the ability to alter these cells.

This research increases researchers ability to produce these stem cells, by increasing the ability of medical scientists to produce adequate numbers of stem cells, while also increasing the range of potential treatment options by more effectively inducing the total pluripotency which is available in Embryonic Stem Cells. This research may also help scientists treat certain forms of cancer which are the result of malfunctions of these genes.

Introduction

[Note: Many of the medical and scientific terms used in this summary are found in the NCI Dictionary of Genetics Terms. When a linked term is clicked, the definition will appear in a separate window.]

[Note: Many of the genes described in this summary are found in the Online Mendelian Inheritance in Man (OMIM) database. When OMIM appears after a gene name or the name of a condition, click on OMIM for a link to more information.]

The genetics of skin cancer is an extremely broad topic. There are more than 100 types of tumors that are clinically apparent on the skin; many of these are known to have familial components, either in isolation or as part of a syndrome with other features. This is, in part, because the skin itself is a complex organ made up of multiple cell types. Furthermore, many of these cell types can undergo malignant transformation at various points in their differentiation, leading to tumors with distinct histology and dramatically different biological behaviors, such as squamous cell carcinoma (SCC) and basal cell cancer (BCC). These have been called nonmelanoma skin cancers or keratinocytic cancers.

Figure 1 is a simple diagram of normal skin structure. It also indicates the major cell types that are normally found in each compartment. Broadly speaking, there are two large compartmentsthe avascular cellular epidermis and the vascular dermiswith many cell types distributed in a largely acellular matrix.[1]

Figure 1. Schematic representation of normal skin. The relatively avascular epidermis houses basal cell keratinocytes and squamous epithelial keratinocytes, the source cells for BCC and SCC, respectively. Melanocytes are also present in normal skin and serve as the source cell for melanoma. The separation between epidermis and dermis occurs at the basement membrane zone, located just inferior to the basal cell keratinocytes.

The outer layer or epidermis is made primarily of keratinocytes but has several other minor cell populations. The bottom layer is formed of basal keratinocytes abutting the basement membrane. The basement membrane is formed from products of keratinocytes and dermal fibroblasts, such as collagen and laminin, and is an important anatomical and functional structure. As the basal keratinocytes divide and differentiate, they lose contact with the basement membrane and form the spinous cell layer, the granular cell layer, and the keratinized outer layer or stratum corneum.

The true cytologic origin of BCC remains in question. BCC and basal cell keratinocytes share many histologic similarities, as is reflected in the name. Alternatively, the outer root sheath cells of the hair follicle have also been proposed as the cell of origin for BCC.[2] This is suggested by the fact that BCCs occur predominantly on hair-bearing skin. BCCs rarely metastasize but can invade tissue locally or regionally, sometimes following along nerves. A tendency for superficial necrosis has resulted in the name rodent ulcer.[3]

Some debate remains about the origin of SCC; however, these cancers are likely derived from epidermal stem cells associated with the hair follicle.[4] A variety of tissues, such as lung and uterine cervix, can give rise to SCC, and this cancer has somewhat differing behavior depending on its source. Even in cancer derived from the skin, SCC from different anatomic locations can have moderately differing aggressiveness; for example, SCC from glabrous (smooth, hairless) skin has a lower metastatic rate than SCC arising from the vermillion border of the lip or from scars.[3]

Additionally, in the epidermal compartment, melanocytes distribute singly along the basement membrane and can transform into melanoma. Melanocytes are derived from neural crest cells and migrate to the epidermal compartment near the eighth week of gestational age. Langerhans cells, or dendritic cells, are a third cell type in the epidermis and have a primary function of antigen presentation. These cells reside in the skin for an extended time and respond to different stimuli, such as ultraviolet radiation or topical steroids, which cause them to migrate out of the skin.[5]

The dermis is largely composed of an extracellular matrix. Prominent cell types in this compartment are fibroblasts, endothelial cells, and transient immune system cells. When transformed, fibroblasts form fibrosarcomas and endothelial cells form angiosarcomas, Kaposi sarcoma, and other vascular tumors. There are a number of immune cell types that move in and out of the skin to blood vessels and lymphatics; these include mast cells, lymphocytes, mononuclear cells, histiocytes, and granulocytes. These cells can increase in number in inflammatory diseases and can form tumors within the skin. For example, urticaria pigmentosa is a condition that arises from mast cells and is occasionally associated with mast cell leukemia; cutaneous T-cell lymphoma is often confined to the skin throughout its course. Overall, 10% of leukemias and lymphomas have prominent expression in the skin.[6]

Epidermal appendages are also found in the dermal compartment. These are derivatives of the epidermal keratinocytes, such as hair follicles, sweat glands, and the sebaceous glands associated with the hair follicles. These structures are generally formed in the first and second trimesters of fetal development. These can form a large variety of benign or malignant tumors with diverse biological behaviors. Several of these tumors are associated with familial syndromes. Overall, there are dozens of different histological subtypes of these tumors associated with individual components of the adnexal structures.[7]

Finally, the subcutis is a layer that extends below the dermis with varying depth, depending on the anatomic location. This deeper boundary can include muscle, fascia, bone, or cartilage. The subcutis can be affected by inflammatory conditions such as panniculitis and malignancies such as liposarcoma.[8]

These compartments give rise to their own malignancies but are also the region of immediate adjacent spread of localized skin cancers from other compartments. The boundaries of each skin compartment are used to define the staging of skin cancers. For example, an in situ melanoma is confined to the epidermis. Once the cancer crosses the basement membrane into the dermis, it is invasive. Internal malignancies also commonly metastasize to the skin. The dermis and subcutis are the most common locations, but the epidermis can also be involved in conditions such as Pagetoid breast cancer.

The skin has a wide variety of functions. First, the skin is an important barrier preventing extensive water and temperature loss and providing protection against minor abrasions. These functions can be aberrantly regulated in cancer. For example, in the erythroderma associated with advanced cutaneous T-cell lymphoma, alterations in the regulations of body temperature can result in profound heat loss. Second, the skin has important adaptive and innate immunity functions. In adaptive immunity, antigen-presenting cells engender a TH1, TH2, and TH17 response.[9] In innate immunity, the immune system produces numerous peptides with antibacterial and antifungal capacity. Consequently, even small breaks in the skin can lead to infection. The skin-associated lymphoid tissue is one of the largest arms of the immune system. It may also be important in immune surveillance against cancer. Immunosuppression, which occurs during organ transplant, is a significant risk factor for skin cancer. The skin is significant for communication through facial expression and hand movements. Unfortunately, areas of specialized function, such as the area around the eyes and ears, are common places for cancer to occur. Even small cancers in these areas can lead to reconstructive challenges and have significant cosmetic and social ramifications.[1]

While the appearance of any one skin cancer can vary, there are general physical presentations that can be used in screening. BCCs most commonly have a pearly rim (see Figure 3) or can appear somewhat eczematous. They often ulcerate (see Figure 3). SCCs frequently have a thick keratin top layer (see Figure 4). Both BCCs and SCCs are associated with a history of sun-damaged skin. Melanomas are characterized by asymmetry, border irregularity, color variation, a diameter of more than 6 mm, and evolution (ABCDE criteria). (Refer to What Does Melanoma Look Like? on NCIs website for more information about the ABCDE criteria.) Photographs representing typical clinical presentations of these cancers are shown below.

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Figure 2. Superficial basal cell carcinoma (left panel) and nodular basal cell carcinoma (right panel).

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Figure 3. Ulcerated basal cell carcinoma (left panel) and ulcerated basal cell carcinoma with characteristic pearly rim (right panel).

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Figure 4. Squamous cell carcinoma on the face with thick keratin top layer (left panel) and squamous cell carcinoma on the leg (right panel).

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Figure 5. Melanomas with characteristic asymmetry, border irregularity, color variation, and large diameter.

Basal cell carcinoma (BCC) is the most common malignancy in people of European descent, with an associated lifetime risk of 30%.[1] While exposure to ultraviolet (UV) radiation is the risk factor most closely linked to the development of BCC, other environmental factors (such as ionizing radiation, chronic arsenic ingestion, and immunosuppression) and genetic factors (such as family history, skin type, and genetic syndromes) also potentially contribute to carcinogenesis. In contrast to melanoma, metastatic spread of BCC is very rare and typically arises from large tumors that have evaded medical treatment for extended periods of time. BCCs can invade tissue locally or regionally, sometimes following along nerves. A tendency for superficial necrosis has resulted in the name rodent ulcer. With early detection, the prognosis for BCC is excellent.

Sun exposure is the major known environmental factor associated with the development of skin cancer of all types. There are different patterns of sun exposure associated with each major type of skin cancer (BCC, squamous cell carcinoma [SCC], and melanoma).

While there is no standard measure, sun exposure can be generally classified as intermittent or chronic, and the effects may be considered acute or cumulative. Intermittent sun exposure is obtained sporadically, usually during recreational activities, and particularly by indoor workers who have only weekends or vacations to be outdoors and whose skin has not adapted to the sun. Chronic sun exposure is incurred by consistent, repetitive sun exposure, during outdoor work or recreation. Acute sun exposure is obtained over a short time period on skin that has not adapted to the sun. Depending on the time of day and a persons skin type, acute sun exposure may result in sunburn. In epidemiology studies, sunburn is usually defined as burn with pain and/or blistering that lasts for 2 or more days. Cumulative sun exposure is the additive amount of sun exposure that one receives over a lifetime. Cumulative sun exposure may reflect the additive effects of intermittent sun exposure, chronic sun exposure, or both.

Specific patterns of sun exposure appear to lead to different types of skin cancer among susceptible individuals. Intense intermittent recreational sun exposure has been associated with melanoma and BCC,[2,3] while chronic occupational sun exposure has been associated with SCC. Given these data, dermatologists routinely counsel patients to protect their skin from the sun by avoiding mid-day sun exposure, seeking shade, and wearing sun-protective clothing, although evidence-based data for these practices are lacking. The data regarding skin cancer risk reduction by regular sunscreen use are variable. One randomized trial of sunscreen efficacy demonstrated statistically significant protection for the development of SCC but no protection for BCC,[4] while another randomized study demonstrated a trend for reduction in multiple occurrences of BCC among sunscreen users [5] but no significant reduction in BCC or SCC incidence.[6]

Level of evidence (sun-protective clothing, avoidance of sun exposure): 4aii

Level of evidence (sunscreen): 1aii

Tanning bed use has also been associated with an increased risk of BCC. A study of 376 individuals with BCC and 390 control subjects found a 69% increased risk of BCC in individuals who had ever used indoor tanning.[7] The risk of BCC was more pronounced in females and individuals with higher use of indoor tanning.[8]

Environmental factors other than sun exposure may also contribute to the formation of BCC and SCC. Petroleum byproducts (e.g., asphalt, tar, soot, paraffin, and pitch), organophosphate compounds, and arsenic are all occupational exposures associated with cutaneous nonmelanoma cancers.[9-11]

Arsenic exposure may occur through contact with contaminated food, water, or air. While arsenic is ubiquitous in the environment, its ambient concentration in both food and water may be increased near smelting, mining, or coal-burning establishments. Arsenic levels in the U.S. municipal water supply are tightly regulated; however, control is lacking for potable water obtained through private wells. As it percolates through rock formations with naturally occurring arsenic, well water may acquire hazardous concentrations of this material. In many parts of the world, wells providing drinking water are contaminated by high levels of arsenic in the ground water. The populations in Bangladesh, Taiwan, and many other locations have high levels of skin cancer associated with elevated levels of arsenic in the drinking water.[12-16] Medicinal arsenical solutions (e.g., Fowlers solution and Bells asthma medication) were once used to treat common chronic conditions such as psoriasis, syphilis, and asthma, resulting in associated late-onset cutaneous malignancies.[17,18] Current potential iatrogenic sources of arsenic exposure include poorly regulated Chinese traditional/herbal medications and intravenous arsenic trioxide utilized to induce remission in acute promyelocytic leukemia.[19,20]

Aerosolized particulate matter produced by combustion of arsenic-containing materials is another source of environmental exposure. Arsenic-rich coal, animal dung from arsenic-rich regions, and chromated copper arsenatetreated wood produce airborne arsenical particles when burned.[21-23] Burning of these products in enclosed unventilated settings (such as for heat generation) is particularly hazardous.[24]

Clinically, arsenic-induced skin cancers are characterized by multiple recurring SCCs and BCCs occurring in areas of the skin that are usually protected from the sun. A range of cutaneous findings are associated with chronic or severe arsenic exposure, including pigmentary variation (poikiloderma of the skin) and Bowen disease (SCC in situ).[25]

However, the effect of arsenic on skin cancer risk may be more complex than previously thought. Evidence from in vivo models indicate that arsenic, alone or in combination with itraconazole, can inhibit the hedgehog pathway in cells with wild-type or mutated Smoothened by binding to GLI2 proteins; in this way, these drugs demonstrated inhibition of BCC growth in these animal models.[26,27] Additionally, the effect of arsenic on skin cancer risk may be modified by certain variants in nucleotide excision repair genes (xeroderma pigmentosum [XP] types A and D).[28]

The high-risk phenotype consists of individuals with the following physical characteristics:

Specifically, people with more highly pigmented skin demonstrate lower incidence of BCC than do people with lighter pigmented skin. Individuals with Fitzpatrick skin types I or II were shown to have a twofold increased risk of BCC in a small case-control study.[29] (Refer to the Pigmentary characteristics section in the Melanoma section of this summary for a more detailed discussion of skin phenotypes based upon pigmentation.) Blond or red hair color was associated with increased risk of BCC in two large cohorts: the Nurses Health Study and the Health Professionals Follow-Up Study.[30]

Immunosuppression also contributes to the formation of nonmelanoma (keratinocyte) skin cancers. Among solid-organ transplant recipients, the risk of SCC is 65 to 250 times higher, and the risk of BCC is 10 times higher than in the general population.[31-33] Nonmelanoma skin cancers in high-risk patients (i.e., solid-organ transplant recipients and chronic lymphocytic leukemia patients) occur at a younger age and are more common, more aggressive, and have a higher risk of recurrence and metastatic spread than nonmelanoma skin cancers in the general population.[34,35] Among patients with an intact immune system, BCCs outnumber SCCs by a 4:1 ratio; in transplant patients, SCCs outnumber BCCs by a 2:1 ratio.

This increased risk has been linked to the level of immunosuppression and UV exposure. As the duration and dosage of immunosuppressive agents increases, so does the risk of cutaneous malignancy; this effect is reversed with decreasing the dosage of, or taking a break from, immunosuppressive agents. Heart transplant recipients, requiring the highest rates of immunosuppression, are at much higher risk of cutaneous malignancy than liver transplant recipients, in whom much lower levels of immunosuppression are needed to avoid rejection.[31,36] The risk appears to be highest in geographic areas of high UV radiation exposure: when comparing Australian and Dutch organ transplant populations, the Australian patients carried a fourfold increased risk of developing SCC and a fivefold increased risk of developing BCC.[37] This speaks to the importance of rigorous sun avoidance among high-risk immunosuppressed individuals.

Individuals with BCCs and/or SCCs report a higher frequency of these cancers in their family members than do controls. The importance of this finding is unclear. Apart from defined genetic disorders with an increased risk of BCC, a positive family history of any skin cancer is a strong predictor of the development of BCC.

A personal history of BCC or SCC is strongly associated with subsequent BCC or SCC. There is an approximate 20% increased risk of a subsequent lesion within the first year after a skin cancer has been diagnosed. The mean age of occurrence for these nonmelanoma skin cancers is the mid-60s.[38-43] In addition, several studies have found that individuals with a history of skin cancer have an increased risk of a subsequent diagnosis of a noncutaneous cancer;[44-47] however, other studies have contradicted this finding.[48-51] In the absence of other risk factors or evidence of a defined cancer susceptibility syndrome, as discussed below, skin cancer patients are encouraged to follow screening recommendations for the general population for sites other than the skin.

Mutations in the gene coding for the transmembrane receptor protein PTCH1, or PTCH, are associated with basal cell nevus syndrome (BCNS) and sporadic cutaneous BCCs. PTCH1, the human homolog of the Drosophila segment polarity gene patched (ptc), is an integral component of the hedgehog signaling pathway, which serves many developmental (appendage development, embryonic segmentation, neural tube differentiation) and regulatory (maintenance of stem cells) roles.

In the resting state, the transmembrane receptor protein PTCH1 acts catalytically to suppress the seven-transmembrane protein Smoothened (Smo), preventing further downstream signal transduction.[52] Stoichiometric binding of the hedgehog ligand to PTCH1 releases inhibition of Smo, with resultant activation of transcription factors (GLI1, GLI2), cell proliferation genes (cyclin D, cyclin E, myc), and regulators of angiogenesis.[53,54] Thus, the balance of PTCH1 (inhibition) and Smo (activation) manages the essential regulatory downstream hedgehog signal transduction pathway. Loss-of-function mutations of PTCH1 or gain-of-function mutations of Smo tip this balance toward constitutive activation, a key event in potential neoplastic transformation.

Demonstration of allelic loss on chromosome 9q22 in both sporadic and familial BCCs suggested the potential presence of an associated tumor suppressor gene.[55,56] Further investigation identified a mutation in PTCH1 that localized to the area of allelic loss.[57] Up to 30% of sporadic BCCs demonstrate PTCH1 mutations.[58] In addition to BCC, medulloblastoma and rhabdomyosarcoma, along with other tumors, have been associated with PTCH1 mutations. All three malignancies are associated with BCNS, and most people with clinical features of BCNS demonstrate PTCH1 mutations, predominantly truncation in type.[59]

Truncating mutations in PTCH2, a homolog of PTCH1 mapping to chromosome 1p32.1-32.3, have been demonstrated in both BCC and medulloblastoma.[60,61] PTCH2 displays 57% homology to PTCH1, differing in the conformation of the hydrophilic region between transmembrane portions 6 and 7, and the absence of C-terminal extension.[62] While the exact role of PTCH2 remains unclear, there is evidence to support its involvement in the hedgehog signaling pathway.[60,63]

BCNS, also known as Gorlin Syndrome, Gorlin-Goltz syndrome, and nevoid basal cell carcinoma syndrome, is an autosomal dominant disorder with an estimated prevalence of 1 in 57,000 individuals.[64] The syndrome is notable for complete penetrance and extremely variable expressivity, as evidenced by evaluation of individuals with identical genotypes but widely varying phenotypes.[59,65] The clinical features of BCNS differ more among families than within families.[66] BCNS is primarily associated with germline mutations in PTCH1, but families with this phenotype have also been associated with alterations in PTCH2 and SUFU.[67-69]

As detailed above, PTCH1 provides both developmental and regulatory guidance; spontaneous or inherited germline mutations of PTCH1 in BCNS may result in a wide spectrum of potentially diagnostic physical findings. The BCNS mutation has been localized to chromosome 9q22.3-q31, with a maximum logarithm of the odd (LOD) score of 3.597 and 6.457 at markers D9S12 and D9S53.[64] The resulting haploinsufficiency of PTCH1 in BCNS has been associated with structural anomalies such as odontogenic keratocysts, with evaluation of the cyst lining revealing heterozygosity for PTCH1.[70] The development of BCC and other BCNS-associated malignancies is thought to arise from the classic two-hit suppressor gene model: baseline heterozygosity secondary to germline PTCH1 mutation as the first hit, with the second hit due to mutagen exposure such as UV or ionizing radiation.[71-75] However, haploinsufficiency or dominant negative isoforms have also been implicated for the inactivation of PTCH1.[76]

The diagnosis of BCNS is typically based upon characteristic clinical and radiologic examination findings. Several sets of clinical diagnostic criteria for BCNS are in use (refer to Table 1 for a comparison of these criteria).[77-80] Although each set of criteria has advantages and disadvantages, none of the sets have a clearly superior balance of sensitivity and specificity for identifying mutation carriers. The BCNS Colloquium Group proposed criteria in 2011 that required 1 major criterion with molecular diagnosis, two major criteria without molecular diagnosis, or one major and two minor criteria without molecular diagnosis.[80] PTCH1 mutations are found in 60% to 85% of patients who meet clinical criteria.[81,82] Most notably, BCNS is associated with the formation of both benign and malignant neoplasms. The strongest benign neoplasm association is with ovarian fibromas, diagnosed in 14% to 24% of females affected by BCNS.[74,78,83] BCNS-associated ovarian fibromas are more likely to be bilateral and calcified than sporadic ovarian fibromas.[84] Ameloblastomas, aggressive tumors of the odontogenic epithelium, have also been proposed as a diagnostic criterion for BCNS, but most groups do not include it at this time.[85]

Originally posted here: IPS Cell Therapy IPS Cell Therapy

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IPS Cell Therapy IPS Cell Therapy - genetherapy.me

On a cold, bright January morning I walked south across Westminster Bridge to St Thomas Hospital, an institution with a proud tradition of innovation: I was there to observe a procedure generally regarded as the greatest advance in cardiac surgery since the turn of the millennium and one that can be performed without a surgeon.

The patient was a man in his 80s with aortic stenosis, a narrowed valve which was restricting outflow from the left ventricle into the aorta. His heart struggled to pump sufficient blood through the reduced aperture, and the muscle of the affected ventricle had thickened as the organ tried to compensate. If left unchecked, this would eventually lead to heart failure. For a healthier patient the solution would be simple: an operation to remove the diseased valve and replace it with a prosthesis. But the mans age and a long list of other medical conditions made open-heart surgery out of the question. Happily, for the last few years, another option has been available for such high-risk patients: transcatheter aortic valve implantation, known as TAVI for short.

This is a non-invasive procedure, and takes place not in an operating theatre but in the catheterisation laboratory, known as the cath lab. When I got there, wearing a heavy lead gown to protect me from X-rays, the patient was already lying on the table. He would remain awake throughout the procedure, receiving only a sedative and a powerful analgesic. I was shown the valve to be implanted, three leaflets fashioned from bovine pericardium (a tough membrane from around the heart of a cow), fixed inside a collapsible metal stent. After being soaked in saline it was crimped on to a balloon catheter and squeezed, from the size and shape of a lipstick, into a long, thin object like a pencil.

The consultant cardiologist, Bernard Prendergast, had already threaded a guidewire through an incision in the patients groin, entering the femoral artery and then the aorta, until the tip of the wire had arrived at the diseased aortic valve. The catheter, with its precious cargo, was then placed over the guidewire and pushed gently up the aorta. When it reached the upper part of the vessel we could track its progress on one of the large X-ray screens above the table. We watched intently as the metal stent described a slow curve around the aortic arch before coming to rest just above the heart.

There was a pause as the team checked everything was ready, while on the screen the silhouette of the furled valve oscillated gently as it was buffeted by pulses of high-pressure arterial blood. When Prendergast was satisfied that the catheter was precisely aligned with the aortic valve, he pressed a button to inflate the tiny balloon. As it expanded it forced the metal stent outwards and back to its normal diameter, and on the X-ray monitor it suddenly snapped into position, firmly anchored at the top of the ventricle. For a second or two the patient became agitated as the balloon obstructed the aorta and stopped the flow of blood to his brain; but as soon as it was deflated he became calm again.

Prendergast and his colleagues peered at the monitors to check the positioning of the device. In a conventional operation the diseased valve would be excised before the prosthesis was sewn in; during a TAVI procedure the old valve is left untouched and the new one simply placed inside it. This makes correct placement vital, since unless the device fits snugly there may be a leak around its edge. The X-ray picture showed that the new valve was securely anchored and moving in unison with the heart. Satisfied that everything had gone according to plan, Prendergast removed the catheter and announced the good news in a voice that was probably audible on the other side of the river. Just minutes after being given a new heart valve, the patient raised an arm from under the drapes and shook the cardiologists hand warmly. The entire procedure had taken less than an hour.

According to many experts, this is what the future will look like. Though available for little more than a decade, TAVI is already having a dramatic impact on surgical practice: in Germany the majority of aortic valve replacements, more than 10,000 a year, are now performed using the catheter rather than the scalpel.

In the UK, the figure is much lower, since the procedure is still significantly more expensive than surgery this is largely down to the cost of the valve itself, which can be as much as 20,000 for a single device. But as the manufacturers recoup their initial outlay on research and development, it is likely to become more affordable and its advantages are numerous. Early results suggest that it is every bit as effective as open-heart surgery, without many of surgerys undesirable aspects: the large chest incision, the heart-lung machine, the long period of post-operative recovery.

The essential idea of TAVI was first suggested more than half a century ago. In 1965, Hywel Davies, a cardiologist at Guys Hospital in London, was mulling over the problem of aortic regurgitation, in which blood flows backwards from the aorta into the heart. He was looking for a short-term therapy for patients too sick for immediate surgery something that would allow them to recover for a few days or weeks, until they were strong enough to undergo an operation. He hit upon the idea of a temporary device that could be inserted through a blood vessel, and designed a simple artificial valve resembling a conical parachute. Because it was made from fabric, it could be collapsed and mounted on to a catheter. It was inserted with the top of the parachute uppermost, so that any backwards flow would be caught by its inside surface like air hitting the underside of a real parachute canopy. As the fabric filled with blood it would balloon outwards, sealing the vessel and stopping most of the anomalous blood flow.

This was a truly imaginative suggestion, made at a time when catheter therapies had barely been conceived of, let alone tested. But, in tests on dogs, Davies found that his prototype tended to provoke blood clots and he was never able to use it on a patient.

Another two decades passed before anybody considered anything similar. That moment came in 1988, when a trainee cardiologist from Denmark, Henning Rud Andersen, was at a conference in Arizona, attending a lecture about coronary artery stenting. It was the first he had heard of the technique, which at the time had been used in only a few dozen patients, and as he sat in the auditorium he had a thought, which at first he dismissed as ridiculous: why not make a bigger stent, put a valve in the middle of it, and implant it into the heart via a catheter? On reflection, he realised that this was not such an absurd idea, and when he returned home to Denmark he visited a local butcher to buy a supply of pig hearts. Working in a pokey room in the basement of his hospital with basic tools obtained from a local DIY warehouse, Andersen constructed his first experimental prototypes. He began by cutting out the aortic valves from the pig hearts, mounted each inside a home-made metal lattice then compressed the whole contraption around a balloon.

Within a few months Andersen was ready to test the device in animals, and on 1 May 1989 he implanted the first in a pig. It thrived with its prosthesis, and Andersen assumed that his colleagues would be excited by his works obvious clinical potential. But nobody was prepared to take the concept seriously folding up a valve and then unfurling it inside the heart seemed wilfully eccentric and it took him several years to find a journal willing to publish his research.

When his paper was finally published in 1992, none of the major biotechnology firms showed any interest in developing the device. Andersens crazy idea worked, but still it sank without trace.

Andersen sold his patent and moved on to other things. But at the turn of the century there was a sudden explosion of interest in the idea of valve implantation via catheter. In 2000, a heart specialist in London, Philipp Bonhoeffer, replaced the diseased pulmonary valve of a 12-year-old boy, using a valve taken from a cows jugular vein, which had been mounted in a stent and put in position using a balloon catheter.

In France, another cardiologist was already working on doing the same for the aortic valve. Alain Cribier had been developing novel catheter therapies for years; it was his company that bought Andersens patent in 1995, and Cribier had persisted with the idea even after one potential investor told him that TAVI was the most stupid project ever heard of.

Eventually, Cribier managed to raise the necessary funds for development and long-term testing, and by 2000 had a working prototype. Rather than use an entire valve cut from a dead heart, as Andersen had, Cribier built one from bovine pericardium, mounted in a collapsible stainless-steel stent. Prototypes were implanted in sheep to test their durability: after two-and-a-half years, during which they opened and closed more than 100m times, the valves still worked perfectly.

Cribier was ready to test the device in humans, but his first patient could not be eligible for conventional surgical valve replacement, which is safe and highly effective: to test an unproven new procedure on such a patient would be to expose them to unnecessary risk.

In early 2002, he was introduced to a 57-year-old man who was, in surgical terms, a hopeless case. He had catastrophic aortic stenosis which had so weakened his heart that with each stroke it could pump less than a quarter of the normal volume of blood; in addition, the blood vessels of his extremities were ravaged by atherosclerosis, and he had chronic pancreatitis and lung cancer. Several surgeons had declined to operate on him, and his referral to Cribiers clinic in Rouen was a final roll of the dice. An initial attempt to open the stenotic valve using a simple balloon catheter failed, and a week after this treatment Cribier recorded in his notes that his patient was near death, with his heart barely functioning. The mans family agreed that an experimental treatment was preferable to none at all, and on 16 April he became the first person to receive a new aortic valve without open-heart surgery.

Over the next couple of days the patients condition improved dramatically: he was able to get out of bed, and the signs of heart failure began to retreat. But shortly afterwards complications arose, most seriously a deterioration in the condition of the blood vessels in his right leg, which had to be amputated 10 weeks later. Infection set in, and four months after the operation, he died.

He had not lived long nobody expected him to but the episode had proved the feasibility of the approach, with clear short-term benefit to the patient. When Cribier presented a video of the operation to colleagues they sat in stupefied silence, realising that they were watching something that would change the nature of heart surgery.

When surgeons and cardiologists overcame their initial scepticism about TAVI they quickly realised that it opened up a vista of exciting new surgical possibilities. As well as replacing diseased valves it is now also possible to repair them, using clever imitations of the techniques used by surgeons. The technology is still in its infancy, but many experts believe that this will eventually become the default option for valvular disease, making surgery increasingly rare.

While TAVI is impressive, there is one even more spectacular example of the capabilities of the catheter. Paediatric cardiologists at a few specialist centres have recently started using it to break the last taboo of heart surgery operating on an unborn child. Nowhere is the progress of cardiac surgery more stunning than in the field of congenital heart disease. Malformations of the heart are the most common form of birth defect, with as many as 5% of all babies born with some sort of cardiac anomaly though most of these will cause no serious, lasting problems. The heart is especially prone to abnormal development in the womb, with a myriad of possible ways in which its structures can be distorted or transposed. Over several decades, specialists have managed to find ways of taming most; but one that remains a significant challenge to even the best surgeon is hypoplastic left heart syndrome (HLHS), in which the entire left side of the heart fails to develop properly. The ventricle and aorta are much smaller than they should be, and the mitral valve is either absent or undersized. Until the early 1980s this was a defect that killed babies within days of birth, but a sequence of complex palliative operations now makes it possible for many to live into adulthood.

Because their left ventricle is incapable of propelling oxygenated blood into the body, babies born with HLHS can only survive if there is some communication between the pulmonary and systemic circulations, allowing the right ventricle to pump blood both to the lungs and to the rest of the body. Some children with HLHS also have an atrial septal defect (ASD), a persistent hole in the tissue between the atria of the heart which improves their chances of survival by increasing the amount of oxygenated blood that reaches the sole functioning pumping chamber. When surgeons realised that this defect conferred a survival benefit in babies with HLHS, they began to create one artificially in those with an intact septum, usually a few hours after birth. But it was already too late: elevated blood pressure was causing permanent damage to the delicate vessels of the lungs while these babies still in the womb.

The logical albeit risky response was to intervene even earlier. In 2000, a team at Boston Childrens Hospital adopted a new procedure to create an ASD during the final trimester of pregnancy: they would deliberately create one heart defect in order to treat another. A needle was passed through the wall of the uterus and into the babys heart, and a balloon catheter used to create a hole between the left and right atria. This reduced the pressures in the pulmonary circulation and hence limited the damage to the lungs; but the tissues of a growing foetus have a remarkable ability to repair themselves, and the artificially created hole would often heal within a few weeks. Cardiologists needed to find a way of keeping it open until birth, when surgeons would be able to perform a more comprehensive repair.

In September 2005 a couple from Virginia, Angela and Jay VanDerwerken, visited their local hospital for a routine antenatal scan. They were devastated to learn that their unborn child had HLHS, and the prognosis was poor. The ultrasound pictures revealed an intact septum, making it likely that even before birth her lungs would be damaged beyond repair. They were told that they could either terminate the pregnancy or accept that their daughter would have to undergo open-heart surgery within hours of her birth, with only a 20% chance that she would survive.

Devastated, the VanDerwerkens returned home, where Angela researched the condition online. Although few hospitals offered any treatment for HLHS, she found several references to the Boston foetal cardiac intervention programme, the team of doctors that had pioneered the use of the balloon catheter during pregnancy.

They arranged an appointment with Wayne Tworetzky, the director of foetal cardiology at Boston Childrens Hospital, who performed a scan and confirmed that their unborn childs condition was treatable. A greying, softly spoken South African, Tworetzky explained that his team had recently developed a new procedure, but that it had never been tested on a patient. It would mean not just making a hole in the septum, but also inserting a device to prevent it from closing. The VanDerwerkens had few qualms about accepting the opportunity: the alternatives gave their daughter a negligible chance of life.

The procedure took place at Brigham and Womens Hospital in Boston on 7 November 2005, 30 weeks into the pregnancy, in a crowded operating theatre. Sixteen doctors, with a range of specialisms, took part: cardiologists, surgeons, and four anaesthetists two to look after the mother, two for her unborn child. Mother and child needed to be completely immobilised during a delicate procedure lasting several hours, so both were given a general anaesthetic. The team watched on the screen of an ultrasound scanner as a thin needle was guided through the wall of the uterus, then the foetuss chest and finally into her heart an object the size of a grape.

A guidewire was placed in the cardiac chambers, then a tiny balloon catheter was inserted and used to create an opening in the atrial septum. This had all been done before; but now the cardiologists added a refinement. The balloon was withdrawn, then returned to the heart, this time loaded with a 2.5 millimetre stent that was set in the opening between the left and right atria. There was a charged silence as the balloon was inflated to expand the stent; then, as the team saw on the monitor that blood was flowing freely through the aperture, the room erupted in cheers.

Grace VanDerwerken was born in early January after a normal labour, and shortly afterwards underwent open-heart surgery. After a fortnight she was allowed home, her healthy pink complexion proving that the interventions had succeeded in producing a functional circulation.

But just when she seemed to be out of danger, Grace died suddenly at the age of 36 days not as a consequence of the surgery, but from a rare arrhythmia, a complication of HLHS that occurs in just 5%. This was the cruellest luck, when she had seemingly overcome the grim odds against her. Her death was a tragic loss, but her parents courage had brought about a new era in foetal surgery.

Much of the most exciting contemporary research focuses on the greatest, most fundamental cardiac question of all: what can the surgeon do about the failing heart? Half a century after Christiaan Barnard performed the first human heart transplant, transplantation remains the gold standard of care for patients in irreversible heart failure once drugs have ceased to be effective. It is an excellent operation, too, with patients surviving an average of 15 years. But it will never be the panacea that many predicted, because there just arent enough donor hearts to go round.

With too few organs available, surgeons have had to think laterally. As a result, a new generation of artificial hearts is now in development. Several companies are now working on artificial hearts with tiny rotary electrical motors. In addition to being much smaller and more efficient than pneumatic pumps, these devices are far more durable, since the rotors that impel the blood are suspended magnetically and are not subject to the wear and tear caused by friction. Animal trials have shown promising results, but, as yet, none of these have been implanted in a patient.

Another type of total artificial heart, as such devices are known, has, however, recently been tested in humans. Alain Carpentier, an eminent French surgeon still active in his ninth decade, has collaborated with engineers from the French aeronautical firm Airbus to design a pulsatile, hydraulically powered device whose unique feature is the use of bioprosthetic materials both organic and synthetic matter. Unlike earlier artificial hearts, its design mimics the shape of the natural organ; the internal surfaces are lined with preserved bovine pericardial tissue, a biological surface far kinder to the red blood cells than the polymers previously used. Carpentiers artificial heart was first implanted in December 2013. Although the first four patients have since died two following component failures the results were encouraging, and a larger clinical trial is now under way.

One drawback to the artificial heart still leads many surgeons to dismiss the entire concept out of hand: the price tag. These high-precision devices cost in excess of 100,000 each, and no healthcare service in the world, publicly or privately funded, could afford to provide them to everybody in need of one. And there is one still more tantalising notion: that we will one day be able to engineer spare parts for the heart, or even an entire organ, in the laboratory.

In the 1980s, surgeons began to fabricate artificial skin for burns patients, seeding sheets of collagen or polymer with specialised cells in the hope that they would multiply and form a skin-like protective layer. But researchers had loftier ambitions, and a new field tissue engineering began to emerge.

High on the list of priorities for tissue engineers was the creation of artificial blood vessels, which would have applications across the full range of surgical specialisms. In 1999 surgeons in Tokyo performed a remarkable operation in which they gave a four-year-old girl a new artery grown from cells taken from elsewhere in her body. She had been born with a rare congenital defect which had completely obliterated the right branch of her pulmonary artery, the vessel conveying blood to the right lung. A short section of vein was excised from her leg, and cells from its inside wall were removed in the laboratory. They were then left to multiply in a bioreactor, a vessel that bathed them in a warm nutrient broth, simulating conditions inside the body.

After eight weeks, they had increased in number to more than 12m, and were used to seed the inside of a polymer tube which functioned as a scaffold for the new vessel. The tissue was allowed to continue growing for 10 days, and then the graft was transplanted. Two months later the polymer scaffold around the tissue, designed to break down inside the body, had completely dissolved, leaving only new tissue that would it was hoped grow with the patient.

At the turn of the millennium, a new world of possibility opened up when researchers gained a powerful new tool: stem cell technology. Stem cells are not specialised to one function but have the potential to develop into many different tissue types. One type of stem cell is found in growing embryos, and another in parts of the adult body, including the bone marrow (where they generate the cells of the blood and immune system) and skin. In 1998 James Thomson, a biologist at the University of Wisconsin, succeeded in isolating stem cells from human embryos and growing them in the laboratory.

But an arguably even more important breakthrough came nine years later, when Shinya Yamanaka, a researcher at Kyoto University, showed that it was possible to genetically reprogram skin cells and convert them into stem cells. The implications were enormous. In theory, it would now be possible to harvest mature, specialised cells from a patient, reprogram them as stem cells, then choose which type of tissue they would become.

Sanjay Sinha, a cardiologist at the University of Cambridge, is attempting to grow a patch of artificial myocardium (heart muscle tissue) in the laboratory for later implantation in the operating theatre. His technique starts with undifferentiated stem cells, which are then encouraged to develop into several types of specialised cell. These are then seeded on to a scaffold made from collagen, a tough protein found in connective tissue. The presence of several different cell types means that when they have had time to proliferate, the new tissue will develop its own blood supply.

Clinical trials are still some years away, but Sinha hopes that one day it will be possible to repair a damaged heart by sewing one of these patches over areas of muscle scarred by a heart attack.

Using advanced tissue-engineering techniques, researchers have already succeeded in creating replacement valves from the patients own tissue. This can be done by harvesting cells from elsewhere in the body (usually the blood vessels) and breeding them in a bioreactor, before seeding them on to a biodegradable polymer scaffold designed in the shape of a valve. Once the cells are in place they are allowed to proliferate before implantation, after which the scaffold melts away, leaving nothing but new tissue. The one major disadvantage of this approach is that each valve has to be tailor-made for a specific patient, a process that takes weeks. In the last couple of years, a group in Berlin has refined the process by tissue-engineering a valve and then stripping it of cellular material, leaving behind just the extracellular matrix the structure that holds the cells in position.

The end result is therefore not quite a valve, but a skeleton on which the body lays down new tissue. Valves manufactured in this way can be implanted, via catheter, in anybody; moreover, unlike conventional prosthetic devices, if the recipient is a child the new valve should grow with them.

If it is possible to tissue-engineer a valve, then why not an entire heart? For many researchers this has come to be the ultimate prize, and the idea is not necessarily as fanciful as it first appears.

In 2008, a team led by Doris Taylor, a scientist at the University of Minnesota, announced the creation of the worlds first bioartificial heart composed of both living and manufactured parts. They began by pumping detergents through hearts excised from rats. This removed all the cellular tissue from them, leaving a ghostly heart-shaped skeleton of extracellular matrix and connective fibre, which was used as a scaffold onto which cardiac or blood-vessel cells were seeded. The organ was then cultured in a bioreactor to encourage cell multiplication, with blood constantly perfused through the coronary arteries. After four days, it was possible to see the new tissue contracting, and after a week the heart was even capable of pumping blood though only 2% of its normal volume.

This was a brilliant achievement, but scaling the procedure up to generate a human-sized heart is made far more difficult by the much greater number of cells required. Surgeons in Heidelberg have since applied similar techniques to generate a human-sized cardiac scaffold covered in living tissue. The original heart came from a pig, and after it had been decellularised it was populated with human vascular cells and cardiac cells harvested from a newborn rat. After 10 days the walls of the organ had become lined with new myocardium which even showed signs of electrical activity. As a proof of concept, the experiment was a success, though after three weeks of culture the organ could neither contract nor pump blood.

Growing tissues and organs in a bioreactor is a laborious business, but recent improvements in 3D printing offer the tantalising possibility of manufacturing a new heart rapidly and to order. 3D printers work by breaking down a three-dimensional object into a series of thin, two-dimensional slices, which are laid down one on top of another. The technology has already been employed to manufacture complex engineering components out of metal or plastic, but it is now being used to generate tissues in the laboratory. To make an aortic valve, researchers at Cornell University took a pigs valve and X-rayed it in a high-resolution CT scanner. This gave them a precise map of its internal structure which could be used as a template. Using the data from the scan, the printer extruded thin jets of a hydrogel, a water-absorbent polymer that mimics natural tissue, gradually building up a duplicate of the pig valve layer by layer. This scaffold could then be seeded with living cells and incubated in the normal way.

Pushing the technology further, Adam Feinberg, a materials scientist at Carnegie Mellon University in Pittsburgh, recently succeeded in fabricating the first anatomically accurate 3D-printed heart. This facsimile was made of hydrogel and contained no tissue, but it did show a remarkable fidelity to the original organ. Since then, Feinberg has used natural proteins such as fibrin and collagen to 3D-print hearts. For many researchers in this field, a fully tissue-engineered heart is the ultimate prize.

We are left with several competing visions of the future. Within a few decades it is possible that we will be breeding transgenic pigs in vast sterile farms and harvesting their hearts to implant in sick patients. Or that new organs will be 3D-printed to order in factories, before being dispatched in drones to wherever they are needed. Or maybe an unexpected breakthrough in energy technology will make it possible to develop a fully implantable, permanent mechanical heart.

Whatever the future holds, it is worth reflecting on how much has been achieved in so little time. Speaking in 1902, six years after Ludwig Rehn became the first person to perform cardiac surgery, Harry Sherman remarked that the road to the heart is only two or three centimetres in a direct line, but it has taken surgery nearly 2,400 years to travel it. Overcoming centuries of cultural and medical prejudice required a degree of courage and vision still difficult to appreciate today. Even after that first step had been taken, another 50 years elapsed before surgeons began to make any real progress. Then, in a dizzying period of three decades, they learned how to open the heart, repair and even replace it. In most fields, an era of such fundamental discoveries happens only once if at all and it is unlikely that cardiac surgeons will ever again captivate the world as Christiaan Barnard and his colleagues did in 1967. But the history of heart surgery is littered with breakthroughs nobody saw coming, and as long as there are surgeons of talent and imagination, and a determination to do better for their patients, there is every chance that they will continue to surprise us.

Main photograph: Getty Images

This is an adapted extract from The Matter of the Heart by Thomas Morris, published by the Bodley Head

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Robot hearts: medicine's new frontier - The Guardian

While a number of companies have dabbled in this space, the following players are facilitating the development of iPS cell therapies: Cellular Dynamics International (CDI),Cynata Therapeutics, RIKEN, and Astellas (previously Ocata Therapeutics).

While each iPS cell therapy group is considered in detail below, Cellular Dynamics International (CDI) is featured first, because it dominates the iPSC industry. CDI also recently split into two business units, a Life Science Unit and a Therapeutics Unit, demonstrating a commercial strategy for its iPS cell therapy development.

Founded in 2004 and listed on NASDAQ in July 2013, Cellular Dynamics International (CDI) is headquartered in Madison, Wisconsin. The company is known for itsextremely robust patent portfolio containing more than 900 patents.

According to the company, CDI is the worlds largest producer of fully functional human cells derived from induced pluripotent stem (iPS) cells.[1] Their trademarked, iCell Cardiomyocytes, derived from iPSCs, are human cardiac cells used to aid drug discovery, improve the predictability of a drugs worth, and screen for toxicity. In addition, CDI provides: iCell Endothelial Cells for use in vascular-targeted drug discovery and tissue regeneration, iCell Hepatocytes, and iCell Neurons for pre-clinical drug discovery, toxicity testing, disease prediction, and cellular research.[2]

Induced pluripotent stem cells were first produced in 2006 from mouse cells and in 2007 from human cells, by Shinya Yamanaka at Kyoto University,[3] who also won the Nobel Prize in Medicine or Physiology for his work on iPSCs.[4] Yamanaka has ties toCellular Dynamics International as a member of the scientific advisory board of iPS Academia Japan. IPS Academia Japan was originally established to manage the patents and technology of Yamanakas work, and is now the distributor of several of Cellular Dynamics products, including iCell Neurons, iCell Cardiomyocytes, and iCell Endothelial Cells.[5]

Importantly, in 2010 Cellular Dynamics became the first foreign company to be granted rights to use Yamanakas iPSC patent portfolio.Not only has CDI licensed rights to Yamanakas patents, but it also has a license to use Otsu, Japan-based Takara Bios RetroNectin product, which it uses as a tool to produce its iCell and MyCell products.[6]

Furthermore, in February 2015, Cellular Dynamics International announcedit would be manufacturing cGMP HLA Superdonor stem cell lines that will support cellular therapy applications through genetic matching.[8] Currently, CDI has two HLA superdonor cell lines that provide a partial HLA match to approximately 19% of the population within the U.S., and it aims to expand its master stem cell bank by collecting more donor cell lines that will cover 95% of the U.S. population.[9]The HLA superdonor cell lines were manufactured using blood samples, and used to produce pluripotent iPSC lines, giving the cells the capacity to differentiate into nearly any cell within the human body.

On March 30, 2015, Fujifilm Holdings Corporation announced that it was acquiring CDI for $307 million, allowingCDI tocontinue to run its operations in Madison, Wisconsin, and Novato, California as a consolidated subsidiary of Fujifilm.[14] A key benefit of the merger is that CDIs technology platform enables the production of high-quality fully functioning iPSCs (and other human cells) on an industrial scale, while Fujifilm has developed highly-biocompatible recombinant peptidesthat can be shaped into a variety of forms for use as a cellular scaffoldin regenerative medicinewhen used in conjunction with CDIs products.[15]

Additionally, Fujifilm has been strengthening its presence in the regenerative medicine field over the past several years, including a recent A$4M equity stake in Cynata Therapeutics and anacquisition ofJapan Tissue Engineering Co. Ltd.in December 2014. Most commonly called J-TEC, Japan Tissue Engineering Co. Ltd. successfully launched the first two regenerative medicine products in the country of Japan.According toKaz Hirao, CEO of CDI, It is very important for CDI to get into the area of therapeutic products, and we can accelerate this by aligning it with strategic and technical resources present within J-TEC.

Kaz Hirao also states,For our Therapeutic businesses, we will aim to file investigational new drugs (INDs) with the U.S. FDA for the off-the-shelf iPSC-derived allogeneic therapeutic products. Currently, we are focusing on retinal diseases, heart disorders, Parkinsons disease, and cancers. For those four indicated areas, we would like to file several INDs within the next five years.

Finally, in September 2015, CDI againstrengthened its iPS cell therapycapacity by setting up a new venture, Opsis Therapeutics. Opsis is focused on discovering and developing novel medicines to treat retinal diseases and is apartnership with Dr. David Gamm, the pioneer of iPS cell-derived retinal differentiation and transplantation.

In summary, several key events indicate CDIs commitment to developing iPS cell therapeutics, including:

Australian stem cell company Cynata Therapeutics (ASX:CYP) is taking a unique approachby creating allogeneic iPSC derived mesenchyal stem cell (MSCs)on a commercial scale.Cynatas Cymerus technology utilizes iPSCs provided by Cellular Dynamics International, a Fujifilm company, as the starting material for generating mesenchymoangioblasts (MCAs), and subsequently, for manufacturing clinical-gradeMSCs.According to Cynatas Executive Chairman Stewart Washer who was interviewed by The Life Sciences Report, The Cymerus technology gets around the loss of potency with the unlimited iPS cellor induced pluripotent stem cellwhich is basically immortal.

OnJanuary 19, 2017, Fujifilm took anA$3.97 million (10%) strategic equity stakein Cynata, positioning the parties to collaborate on the further development and commercialisation of Cynatas lead Cymerus therapeutic MSC product CYP-001 for graft-versus-host disease (GvHD). (CYP-001 is the product designation unique to the GVHD indication). The Fujifilm partnership also includes potential future upfront and milestone payments in excess of A$60 million and double-digit royalties on CYP-001 product net sales for Cynata Therapeutics, as well as strategic relationship for potential future manufacture of CYP-001 and certain rights to other Cynata technology.

One of the key inventors of Cynatas technology is Igor Slukvin, MD, Ph.D., Scientific Founder of Cellular Dynamics International (CDI) and Cynata Therapeutics. Dr. Slukvin has released more than 70 publications about stem cell topics, including the landmark article in Cell describing the now patented Cymerus technique. Dr. Slukvins co-inventor is Dr. James Thomson, the first person to isolate an embryonic stem cell (ESC) and one of the first people to create a human induced pluripotent stem cell (hiPSC). Dr. James Thompson was theFounder of CDI in 2004.

There are three strategic connections between Cellular Dynamics International (CDI) and Cynata Therapeutics, which include:

Recently, Cynata received advice from the UK Medicines and Healthcare products Regulatory Agency (MHRA) that its Phase I clinical trial application has been approved, titledAn Open-Label Phase 1 Study to Investigate the Safety and Efficacy of CYP-001 for the Treatment of Adults With Steroid-Resistant Acute Graft Versus Host Disease. It will be the worlds first clinical trial involving a therapeutic product derived from allogeneic (unrelated to the patient) induced pluripotent stem cells (iPSCs).

Participants for Cynatas upcoming Phase I clinical trial will be adults who have undergone an allogeneic haematopoietic stem cell transplant (HSCT) to treat a haematological disorder and subsequently been diagnosed with steroid-resistant Grade II-IV GvHD.The primary objective of the trial is to assess safety and tolerability, while the secondary objective is to evaluate the efficacy of two infusions of CYP-001 in adults with steroid-resistant GvHD.

Using Professor Yamankas Nobel Prize winning achievement of ethically uncontentious iPSCs and CDIs high quality iPSCs as source material, Cynata has achieved two world firsts:

Cynata has also released promising pre-clinical data in Asthma, Myocardial Infarction (Heart Attack), andCritical Limb Ischemia.

There are four key advantages of Cynatas proprietary Cymerus MSC manufacturing platform.Because the proprietary Cymerus technology allows nearly unlimited production of MSCs from a single iPSC donor, there is batch-to-batch uniformity. Utilizing a consistent starting material allows for a standardized cell manufacturing process and a consistent cell therapy product. Unlike other companies involved with MSC manufacturing, Cynata does not require a constant stream of new donors in order to source fresh stem cells for its cell manufacturing process, nor does it require the massive expansion of MSCs necessitated by reliance on freshly isolated donations.

Finally, Cynata has achieved a cost-savings advantage through its uniqueapproach to MSCmanufacturing. Its proprietary Cymerus technology addresses a critical shortcoming in existing methods of production of MSCs for therapeutic use, which is the ability to achieve economic manufacture at commercial scale.

On June 22, 2016, RIKEN announced that it is resuming its retinal induced pluripotent stem cell (iPSC) study in partnership with Kyoto University.

2013 was the first time in which clinical research involving transplant of iPSCs into humans was initiated, led by Masayo Takahashi of the RIKEN Center for Developmental Biology (CDB)in Kobe, Japan. Dr. Takahashi and her team wereinvestigating the safety of iPSC-derived cell sheets in patients with wet-type age-related macular degeneration. Althoughthe trial was initiated in 2013 and production of iPSCs from patients began at that time, it was not until August of 2014 that the first patient, a Japanese woman, was implanted with retinal tissue generated using iPSCs derived from her own skin cells.

A team of three eye specialists, led by Yasuo Kurimoto of the Kobe City Medical Center General Hospital, implanted a 1.3 by 3.0mm sheet of iPSC-derived retinal pigment epithelium cells into the patients retina.[196]Unfortunately, the study was suspended in 2015 due to safety concerns. As the lab prepared to treat the second trial participant, Yamanakas team identified two small genetic changes in the patients iPSCs and the retinal pigment epithelium (RPE) cells derived from them. Therefore, it is major news that theRIKEN Institute will now be resuming the worlds first clinical study involving the use of iPSC-derived cells in humans.

According to the Japan Times, this attempt at the clinical studywill involve allogeneic rather than autologous iPSC-derived cells for purposes of cost and time efficiency.Specifically,the researchers will be developing retinal tissues from iPS cells supplied by Kyoto Universitys Center for iPS Cell Research and Application, an institution headed by Nobel prize winner Shinya Yamanaka. To learn about this announcement, view this article fromAsahi Shimbun, aTokyo- based newspaper.

In November 2015 Astellas Pharma announced it was acquiring Ocata Therapeutics for $379M. Ocata Therapeutics is a biotechnology company that specializes in the development of cellular therapies, using both adult and human embryonic stem cells to develop patient-specific therapies. The companys main laboratory and GMP facility is in Marlborough, Massachusetts, and its corporate offices are in Santa Monica, California.

When a number of private companies began to explore the possibility of using artificially re-manufactured iPSCs for therapeutic purposes, one such company that was ready to capitalize on the breakthrough technology was Ocata Therapeutics, at the time called Advanced Cell Technology. In 2010, the company announced that it had discovered several problematic issues while conducting experiments for the purpose of applying for U.S. Food and Drug Administration approval to use iPSCs in therapeutic applications. Concerns such as premature cell death, mutation into cancer cells, and low proliferation rates were some of the problems that surfaced. [17]

As a result, the company shifted its induced pluripotent stem cell approach to producingiPS cell-derived human platelets, as one of the benefits of a platelet-based product is that platelets do not contain nuclei, and therefore, cannot divide or carry genetic information. While the companys Induced Pluripotent Stem Cell-Derived Human Platelet Program received a great deal of media coverage in late 2012, including being awarded the December 2012 honor of being named one of the 10 Ideas that Will Shape the Yearby New Scientist Magazine,[178] unfortunately the company did not succeed in moving the concept through to clinical testing in 2013.

Nonetheless, Astellas is clearly continuing to develop Ocatas pluripotent stem cell technologies involving embryonic stem cells (ESCs) and induced pluripotent stem cells (iPS cells). In a November 2015 presentation by Astellas President and CEO, Yoshihiko Hatanaka, he indicated that the company will aim to develop an Ophthalmic Disease Cell Therapy Franchise based around its embryonic stem cell (ESC) and induced pluripotent stem cell (iPS cell) technology. [19]

Footnotes [1] CellularDynamics.com (2014). About CDI. Available at: http://www.cellulardynamics.com/about/index.html. Web. 1 Apr. 2015. [2] Ibid. [3] Takahashi K, Yamanaka S (August 2006).Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors.Cell126(4): 66376. [4] 2012 Nobel Prize in Physiology or Medicine Press Release. Nobelprize.org. Nobel Media AB 2013. Web. 7 Feb 2014. Available at: http://www.nobelprize.org/nobel_prizes/medicine/laureates/2012/press.html. Web. 1 Apr. 2015. [5] Striklin, D (Jan 13, 2014). Three Companies Banking on Regenerative Medicine. Wall Street Cheat Sheet. Retrieved Feb 1, 2014 from, http://wallstcheatsheet.com/stocks/3-companies-banking-on-regenerative-medicine.html/?a=viewall. [6] Striklin, D (2014). Three Companies Banking on Regenerative Medicine. Wall Street Cheat Sheet [Online]. Available at: http://wallstcheatsheet.com/stocks/3-companies-banking-on-regenerative-medicine.html/?a=viewall. Web. 1 Apr. 2015. [7] Cellular Dynamics International (July 30, 2013). Cellular Dynamics International Announces Closing of Initial Public Offering [Press Release]. Retrieved from http://www.cellulardynamics.com/news/pr/2013_07_30.html. [8] Investors.cellulardynamics.com,. Cellular Dynamics Manufactures Cgmp HLA Superdonor Stem Cell Lines To Enable Cell Therapy With Genetic Matching (NASDAQ:ICEL). N.p., 2015. Web. 7 Mar. 2015. [9] Ibid. [10] Cellulardynamics.com,. Cellular Dynamics | Mycell Products. N.p., 2015. Web. 7 Mar. 2015. [11]Sirenko, O. et al. Multiparameter In Vitro Assessment Of Compound Effects On Cardiomyocyte Physiology Using Ipsc Cells.Journal of Biomolecular Screening18.1 (2012): 39-53. Web. 7 Mar. 2015. [12] Sciencedirect.com,. Prevention Of -Amyloid Induced Toxicity In Human Ips Cell-Derived Neurons By Inhibition Of Cyclin-Dependent Kinases And Associated Cell Cycle Events. N.p., 2015. Web. 7 Mar. 2015. [13] Sciencedirect.com,. HER2-Targeted Liposomal Doxorubicin Displays Enhanced Anti-Tumorigenic Effects Without Associated Cardiotoxicity. N.p., 2015. Web. 7 Mar. 2015. [14] Cellular Dynamics International, Inc. Fujifilm Holdings To Acquire Cellular Dynamics International, Inc.. GlobeNewswire News Room. N.p., 2015. Web. 7 Apr. 2015. [15] Ibid. [16]Cyranoski, David. Japanese Woman Is First Recipient Of Next-Generation Stem Cells. Nature (2014): n. pag. Web. 6 Mar. 2015. [17] Advanced Cell Technologies (Feb 11, 2011). Advanced Cell and Colleagues Report Therapeutic Cells Derived From iPS Cells Display Early Aging [Press Release]. Available at: http://www.advancedcell.com/news-and-media/press-releases/advanced-cell-and-colleagues-report-therapeutic-cells-derived-from-ips-cells-display-early-aging/. [18] Advanced Cell Technology (Dec 20, 2012). New Scientist Magazine Selects ACTs Induced Pluripotent Stem (iPS) Cell-Derived Human Platelet Program As One of 10 Ideas That Will Shape The Year [Press Release]. Available at: http://articles.latimes.com/2009/mar/06/science/sci-stemcell6. Web. 9 Apr. 2015. [19] Astellas Pharma (2015). Acquisition of Ocata Therapeutics New Step Forward in Ophthalmology with Cell Therapy Approach. Available at: https://www.astellas.com/en/corporate/news/pdf/151110_2_Eg.pdf. Web. 29 Jan. 2017.

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Market Players Developing iPS Cell Therapies

While a number of companies have dabbled in this space, the following players are facilitating the development of iPS cell therapies: Cellular Dynamics International (CDI), RIKEN, Cynata Therapeutics, and Astellas (previously Ocata Therapeutics).

While each iPS cell therapy group is considered in detail below, Cellular Dynamics International (CDI) is featured first, because it dominates the iPSC industry. CDI also recently split into two business units, a Life Science Unit and a Therapeutics Unit, demonstrating a commercial strategy for its iPS cell therapy development.

Cellular Dynamics International (CDI) is headquartered in Madison, Wisconsin, although it provides technical support and sales information from both the United States and Japan. CDI was founded in 2004 and listed on NASDAQ in July 2013. The company had global revenues of $16.7 million in 2014 and currently has 150+ employees. It also has an extremely robust patent portfolio containing more than 800 patents, of which 130 pertain to iPSCs.

According to the company, CDI is the worlds largest producer of fully functional human cells derived from induced pluripotent stem (iPS) cells.[1] Their trademarked, iCell Cardiomyocytes, derived from iPSCs, are human cardiac cells used to aid drug discovery, improve the predictability of a drugs worth, and screen for toxicity. In addition, CDI provides: iCell Endothelial Cells for use in vascular-targeted drug discovery and tissue regeneration, iCell Hepatocytes, and iCell Neurons for pre-clinical drug discovery, toxicity testing, disease prediction, and cellular research.[2] As such, CDIs main role with regard to iPCS therapy development is the production of industrial-scale, clinical-grade iPSCs.

As mentioned previously, induced pluripotent stem cells were first produced in 2006 from mouse cells and in 2007 from human cells, by Shinya Yamanaka at Kyoto University,[3] who also won the Nobel Prize in Medicine or Physiology for his work on iPSCs.[4] Yamanaka has ties toCellular Dynamics International as a member of the scientific advisory board of iPS Academia Japan.

IPS Academia Japan was originally established to manage the patents and technology of Yamanakas work, and is now the distributor of several of Cellular Dynamics products, including iCell Neurons, iCell Cardiomyocytes, and iCell Endothelial Cells.[5] Importantly, in 2010 Cellular Dynamics became the first foreign company to be granted rights to use Yamanakas iPSC patent portfolio.Not only has CDI licensed rights to Yamanakas patents, but it also has a license to use Otsu, Japan-based Takara Bios RetroNectin product, which it uses as a tool to produce its iCell and MyCell products.[6] Through its licenses and intellectual property, CDI currently uses induced pluripotent stem cells to produce human heart cells (cardiomyocytes), brain cells (neurons), blood vessel cells (endothelial cells), and liver cells (hepatocytes), manufacturing them in high quantity, quality, and purity.

These human cells produced by the company are used for both in vitro and in vivo applications that range from basic and applied research to drug discovery research that includes target identification and validation, toxicity testing, safety and efficacy testing, and more. As such, CDI has emerged as a global leader with the ability to generate iPSCs that have the potential to be used for a wide range of research and possibly therapeutic purposes.

In a landmark event with the iPSC market, the company had an initial public offering (IPO) in July of 2013, in which it sold 38,460,000 shares of common stock to the public at $12.00 per share, to raise proceeds of approximately $43 million.[7] This event secured the companys position as the global leader in producing high-quality human iPSCs and differentiated cells in industrial quantities.

In addition, in March of 2013, Celullar Dynamics International and the Coriell Institute for Medical Research announced receiving multi-million dollars grants from the California Institute for Regenerative Medicine (CIRM) for the creation of iPSC lines from 3,000 healthy and diseased donors, a result that will create the worlds largest human iPSC bank.

Not surprisingly, Cellular Dynamics International has continued its innovation, announcing in February of 2015 that it would be manufacturing cGMP HLA Superdonor stem cell lines that will support cellular therapy applications through genetic matching.[8] Currently, CDI has two HLA superdonor cell lines that provide a partial HLA match to approximately 19% of the population within the U.S., and it aims to expand its master stem cell bank by collecting more donor cell lines that will cover 95% of the U.S. population.[9]

The HLA superdonor cell lines were manufactured using blood samples, and used to produce pluripotent iPSC lines, giving the cells the capacity to differentiate into nearly any cell within the human body.

CDI also leads the iPSC market in terms of supporting drug development and discovery. For example, CDIs MyCell products are created using custom iPSC reprogramming and differentiation methods, thereby providing biologically relevant human cells from patients with unique disease-associated genotypes and phenotypes.[10] The companys iCell and MyCell cells can also be adapted to screening platforms and are matched to function with common readout technologies.[11] CDIs products are also used for high-throughput screening,[12] and have been used as supporting data for Investigational New Drug (IND) applications submitted to the Federal Drug Administration (FDA).[13]

On March 30, 2015, Fujifilm Holdings Corporation announced that it was acquiring CDI, in which Fujifilm will acquire CDI through all-cash offer followed by a second step merger. Specifically, Fujifilm will acquire all issued and outstanding shares of CDIs common stock for $16.5 per share or approximately $ 307 million, after which CDI will continue to run its operations in Madison, Wisconsin, and Novato, California as a consolidated subsidiary of Fujifilm.[14]

CDIs technology platform enables the production of high-quality fully functioning iPSCs (and other human cells) on an industrial scale, while Fujifilm has developed highly-biocompatible recombinant peptidesthat can be shaped into a variety of forms for use as a cellular scaffoldin regenerative medicinewhen used in conjunction with CDIs products.[15] Fujifilm has been strengthening its presence in the regenerative medicine field over several years, including by acquiring a majority of shares of Japan Tissue Engineering Co. in December 2014, so while the acquisition was unexpected, it as not fully suprising.

In summary, the acquisition of CDI will allow Fujifilm to gaindominance in the areaof iPS cell-based drug discovery services and will position it to strategically combine CDIs iPS cell technologywithFujifilms expertise in material science and engineering systems, creating a powerhouse within the iPSC market. It is yet to be seen whether Fujifilm will try to commercialize CDIs iPS cell production technologies by making the cells available for clinical use or whether they will choose to focus their attention on iPS cell-based drug discovery services.

In November 2015 Astellas Pharma announced it was acquiring Ocata Therapeutics for $379M. Ocata Therapeutics is a biotechnology company that specializes in the development of cellular therapies, using both adult and human embryonic stem cells to develop patient-specific therapies. The companys main laboratory and GMP facility is in Marlborough, Massachusetts, and its corporate offices are in Santa Monica, California.

When a number of private companies began to explore the possibility of using artificially re-manufactured iPSCs for therapeutic purposes, one such company that was ready to capitalize on the breakthrough technology was Ocata Therapeutics (at the time called Advanced Cell Technology or ACT). In 2010, the company announced that it had discovered several problematic issues while conducting experiments for the purpose of applying for U.S. Food and Drug Administration approval to use iPSCs in therapeutic applications. Concerns such as premature cell death, mutation into cancer cells, and low proliferation rates were some of the problems that surfaced. [16]

As a result, the company has since shifted its induced pluripotent stem cell approach to producingiPS cell-derived human platelets, as one of the benefits of a platelet-based product is that platelets do not contain nuclei, and therefore, cannot divide or carry genetic information. Although nothing is completely safe, iPS cell-derived platelets are likely to be much safer than other iPSC therapies, in which uncontrolled proliferation is a major concern.

While the companys Induced Pluripotent Stem Cell-Derived Human Platelet Program received a great deal of media coverage in late 2012, including being awarded the December 2012 honor of being named one of the 10 Ideas that Will Shape the Yearby New Scientist Magazine,[17] unfortunately the company did not succeed in moving the concept through to clinical testing in 2013.

Nonetheless, in a November 2015 presentation by Astellas President and CEO, Yoshihiko Hatanaka, he indicated that the company will aim to develop an Ophthalmic Disease Cell Therapy Franchise based around its embryonic stem cells (ESCs) and induced pluripotent stem cell (iPS cells) technology. [18]

On June 22, 2016, RIKEN announced that it is resuming its retinal induced pluripotent stem cell (iPSC) study in partnership with Kyoto University.

2013 was the first time in which clinical research involving transplant of iPSCs into humans was initiated, led by Masayo Takahashi of the RIKEN Center for Developmental Biology (CDB)in Kobe, Japan. Dr. Takahashi and her team wereinvestigating the safety of iPSC-derived cell sheets in patients with wet-type age-related macular degeneration. Althoughthe trial was initiated in 2013 and production of iPSCs from patients began at that time, it was not until August of 2014 that the first patient, a Japanese woman, was implanted with retinal tissue generated using iPSCs derived from her own skin cells.

A team of three eye specialists, led by Yasuo Kurimoto of the Kobe City Medical Center General Hospital, implanted a 1.3 by 3.0mm sheet of iPSC-derived retinal pigment epithelium cells into the patients retina.[19]Unfortunately, the study was suspended in 2015 due to safety concerns. As the lab prepared to treat the second trial participant, Yamanakas team identified two small genetic changes in the patients iPSCs and the retinal pigment epithelium (RPE) cells derived from them. Therefore, it is major news that theRIKEN Institute will now be resuming the worlds first clinical study involving the use of iPSC-derived cells in humans.

According to the Japan Times, this attempt at the clinical studywill involve allogeneic rather than autologous iPSC-derived cells for purposes of cost and time efficiency.Specifically,the researchers will be developing retinal tissues from iPS cells supplied by Kyoto Universitys Center for iPS Cell Research and Application, an institution headed by Nobel prize winner Shinya Yamanaka. To learn about this announcement, view this article fromAsahi Shimbun, aTokyo- based newspaper.

Australian stem cell company Cynata Therapeutics (ASX:CYP) is taking a unique approach. It is creating allogeneic iPS cell derived mesenchyal stem cell (MSCs).Cynatas Cymerus technology utilizes iPSCs originating from an adult donor as the starting material for generating mesenchymoangioblasts (MCAs), and subsequently, for manufacturing clinical-gradeMSCs.

One of the key inventors of the approach is Igor Slukvin, who has released more than 70 publications about stem cell topics, including the landmark article in Cell describing the now patented Cymerus technique. Dr. Slukvins co-inventor is James Thomson, the first person to isolate an embryonic stem cell (ESC) and one of the first people to create a human-induced, pluripotent stem cell (hiPSC).

Recently, Cynata received advice from the UK Medicines and Healthcare products Regulatory Agency (MHRA) that its Phase I clinical trial application has been approved, titledAn Open-Label Phase 1 Study to Investigate the Safety and Efficacy of CYP-001 for the Treatment of Adults With Steroid-Resistant Acute Graft Versus Host Disease. It will be the worlds first clinical trial involving a therapeutic product derived from allogeneic (unrelated to the patient) induced pluripotent stem cells (iPSCs).

Participants for Cynatas upcoming Phase I clinical trial will be adults who have undergone an allogeneic haematopoietic stem cell transplant (HSCT) to treat a haematological disorder and subsequently been diagnosed with steroid-resistant Grade II-IV GvHD.The primary objective of the trial is to assess safety and tolerability, while the secondary objective is to evaluate the efficacy of two infusions of CYP-001 in adults with steroid-resistant GvHD.

There are four key advantages of Cynatas proprietary Cymerus MSC manufacturing platform, as described below.

Unlimited Quantities Cynatas Cymerus technology utilizes iPSCs originating from an adult donor as the starting material for generating mesenchymoangioblasts (MCAs), and subsequently, for manufacturing clinical-gradeMSCs. According to Cynatas Executive Chairman Stewart Washer who was recently interviewed by The Life Sciences Report, The Cymerus technology gets around the loss of potency with the unlimited iPS cellor induced pluripotent stem cellwhich is basically immortal.

Uniform Batches Because the proprietary Cymerus technology allows nearly unlimited production of MSCs from a single iPSC donor, there is batch-to-batch uniformity. Utilizing a consistent starting material allows for a standardized cell manufacturing process and a consistent cell therapy product.

Single Donor As described previously, Cynatas Cymerus technology creates iPSC-derived mesenchymoangioblasts (MCAs), which are differentiated into MSCs. Unlike other companies involved with MSC manufacturing, Cynata does not require a constant stream of new donors in order to source fresh stem cells for its cell manufacturing process, nor does it require the massive expansion of MSCs necessitated by reliance on freshly isolated donations.

Economic Manufacture at Commercial Scale (Low Cost) Finally, Cynata has achieved a cost-savings advantage through its uniqueapproach to MSCmanufacturing. Its proprietary Cymerus technology addresses a critical shortcoming in existing methods of production of MSCs for therapeutic use, which is the ability to achieve economic manufacture at commercial scale.

Footnotes [1] CellularDynamics.com (2014). About CDI. Available at: http://www.cellulardynamics.com/about/index.html. Web. 1 Apr. 2015. [2] Ibid. [3] Takahashi K, Yamanaka S (August 2006).Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors.Cell126(4): 66376. [4] 2012 Nobel Prize in Physiology or Medicine Press Release. Nobelprize.org. Nobel Media AB 2013. Web. 7 Feb 2014. Available at: http://www.nobelprize.org/nobel_prizes/medicine/laureates/2012/press.html. Web. 1 Apr. 2015. [5] Striklin, D (Jan 13, 2014). Three Companies Banking on Regenerative Medicine. Wall Street Cheat Sheet. Retrieved Feb 1, 2014 from, http://wallstcheatsheet.com/stocks/3-companies-banking-on-regenerative-medicine.html/?a=viewall. [6] Striklin, D (2014). Three Companies Banking on Regenerative Medicine. Wall Street Cheat Sheet [Online]. Available at: http://wallstcheatsheet.com/stocks/3-companies-banking-on-regenerative-medicine.html/?a=viewall. Web. 1 Apr. 2015. [7] Cellular Dynamics International (July 30, 2013). Cellular Dynamics International Announces Closing of Initial Public Offering [Press Release]. Retrieved from http://www.cellulardynamics.com/news/pr/2013_07_30.html. [8] Investors.cellulardynamics.com,. Cellular Dynamics Manufactures Cgmp HLA Superdonor Stem Cell Lines To Enable Cell Therapy With Genetic Matching (NASDAQ:ICEL). N.p., 2015. Web. 7 Mar. 2015. [9] Ibid. [10] Cellulardynamics.com,. Cellular Dynamics | Mycell Products. N.p., 2015. Web. 7 Mar. 2015. [11]Sirenko, O. et al. Multiparameter In Vitro Assessment Of Compound Effects On Cardiomyocyte Physiology Using Ipsc Cells.Journal of Biomolecular Screening18.1 (2012): 39-53. Web. 7 Mar. 2015. [12] Sciencedirect.com,. Prevention Of -Amyloid Induced Toxicity In Human Ips Cell-Derived Neurons By Inhibition Of Cyclin-Dependent Kinases And Associated Cell Cycle Events. N.p., 2015. Web. 7 Mar. 2015. [13] Sciencedirect.com,. HER2-Targeted Liposomal Doxorubicin Displays Enhanced Anti-Tumorigenic Effects Without Associated Cardiotoxicity. N.p., 2015. Web. 7 Mar. 2015. [14] Cellular Dynamics International, Inc. Fujifilm Holdings To Acquire Cellular Dynamics International, Inc.. GlobeNewswire News Room. N.p., 2015. Web. 7 Apr. 2015. [15] Ibid. [16] Advanced Cell Technologies (Feb 11, 2011). Advanced Cell and Colleagues Report Therapeutic Cells Derived From iPS Cells Display Early Aging [Press Release]. Available at: http://www.advancedcell.com/news-and-media/press-releases/advanced-cell-and-colleagues-report-therapeutic-cells-derived-from-ips-cells-display-early-aging/. [17] Advanced Cell Technology (Dec 20, 2012). New Scientist Magazine Selects ACTs Induced Pluripotent Stem (iPS) Cell-Derived Human Platelet Program As One of 10 Ideas That Will Shape The Year [Press Release]. Available at: http://articles.latimes.com/2009/mar/06/science/sci-stemcell6. Web. 9 Apr. 2015. [18] Astellas Pharma (2015). Acquisition of Ocata Therapeutics New Step Forward in Ophthalmology with Cell Therapy Approach. Available at: https://www.astellas.com/en/corporate/news/pdf/151110_2_Eg.pdf. Web. 29 Jan. 2017. [19]Cyranoski, David. Japanese Woman Is First Recipient Of Next-Generation Stem Cells. Nature (2014): n. pag. Web. 6 Mar. 2015.

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Companies Developing Induced Pluripotent Stem Cell (iPS ...

On behalf of the organizing committee, it is my distinct pleasure to invite you to attend the Stem Cell Congress-2017. After the success of the Cell Science-2011, 2012, 2013, 2014, 2015, Conference series.LLC is proud to announce the 6th World Congress and expo on Cell & Stem Cell Research (Stem Cell Congress-2017) which is going to be held during March 20-22, 2017, Orlando, Florida, USA. The theme of Stem Cell Congress-2017 is Explore and Exploit the Novel Techniques in Cell and Stem Cell Research.

This annual Cell Science conference brings together domain experts, researchers, clinicians, industry representatives, postdoctoral fellows and students from around the world, providing them with the opportunity to report, share, and discuss scientific questions, achievements, and challenges in the field.

Examples of the diverse cell science and stem cell topics that will be covered in this comprehensive conference include Cell differentiation and development, Cell metabolism, Tissue engineering and regenerative medicine, Stem cell therapy, Cell and gene therapy, Novel stem cell technologies, Stem cell and cancer biology, Stem cell treatment, Tendency in cell biology of aging and Apoptosis and cancer disease, Drugs and clinical developments. The meeting will focus on basic cell mechanism studies, clinical research advances, and recent breakthroughs in cell and stem cell research. With the support of many emerging technologies, dramatic progress has been made in these areas. In Stem Cell Congress-2017, you will be able to share experiences and research results, discuss challenges encountered and solutions adopted and have opportunities to establish productive new academic and industry research collaborations.

In association with the Stem Cell Congress-2017 conference, we will invite those selected to present at the meeting to publish a manuscript from their talk in the journal Cell Science with a significantly discounted publication charge. Please join us in Philadelphia for an exciting all-encompassing annual Stem Cell get together with the theme of better understanding from basic cell mechanisms to latest Stem Cell breakthroughs!

Haval Shirwan, Ph.D. Executive Editor, Journal of Clinical & Cellular Immunology Dr. Michael and Joan Hamilton Endowed Chair in Autoimmune Disease Professor, Department of Microbiology and Immunology Director, Molecular Immunomodulation Program, Institute for Cellular Therapeutics, University of Louisville, Louisville, KY

Track01:Stem Cells

The most well-established and widely used stem cell treatment is thetransplantationof blood stem cells to treat diseases and conditions of the blood and immune system, or to restore the blood system after treatments for specific cancers. Since the 1970s,skin stem cellshave been used to grow skin grafts for patients with severe burns on very large areas of the body. Only a few clinical centers are able to carry out this treatment and it is usually reserved for patients with life-threatening burns. It is also not a perfect solution: the new skin has no hair follicles or sweat glands. Research aimed at improving the technique is ongoing.

Related Stem Cell Conferences|Stem Cell Congress|Cell and Stem Cell Conferences|Conference Series LLC

7thAnnual Conference on Stem Cell and Regenerative MedicineAug 4-5, 2016, Manchester, UK;2nd InternationalConference on AntibodiesJuly 14-15, 2016 Philadelphia, USA; 2nd InternationalConference on Innate ImmunityJuly 21-22, 2016 Berlin, Germany; 2ndInternational Congress on Neuroimmunology March 31-April 02, 2016 Atlanta, USA; InternationalConference on Cancer Immunology July 28-30, 2016 Melbourne, Australia; 5th InternationalConference on ImmunologyOctober 24-26, 2016 Chicago, USA;Cancer Vaccines: Targeting Cancer Genes for Immunotherapy, Mar 610 2016, Whistler, Canada;Systems Immunology: From Molecular Networks to Human Biology, Jan 1014 2016, Big Sky, USA;Novel Immunotherapeutics Summit, Jan 2526 2016, San Diego, USA;Stromal Cells in Immunity, Feb 711 2016, Keystone, USA; 26th European Congress ofClinical Microbiology, April 912 2016, Istanbul, Turkey

Track 02: Stem Cell Banking:

Stem Cell Banking is a facility that preserves stem cells derived from amniotic fluid for future use. Stem cell samples in private or family banks are preserved precisely for use by the individual person from whom such cells have been collected and the banking costs are paid by such person. The sample can later be retrieved only by that individual and for the use by such individual or, in many cases, by his or her first-degree blood relatives.

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8thWorld Congress on Stem Cell ResearchMarch 20-22, 2017 Orlando, USAInternationalConference on Cancer ImmunologyJuly 28-30, 2016 Melbourne, Australia; 5th InternationalConference on ImmunologyOctober 24-26, 2016 Chicago, USA;Cancer Vaccines: Targeting Cancer Genes for Immunotherapy, Mar 610 2016, Whistler, Canada;Systems Immunology: From Molecular Networks to Human Biology, Jan 1014 2016, Big Sky, USA;Novel Immunotherapeutics Summit, Jan 2526 2016, San Diego, USA;Stromal Cells in Immunity, Feb 711 2016, Keystone, USA; 26th European Congress ofClinical Microbiology, April 912 2016, Istanbul, Turkey

Track 03: Stem Cell Therapy:

Autologous cells are obtained from one's own body, just as one may bank his or her own blood for elective surgical procedures. Adult stem cells are frequently used in medical therapies, for example in bone marrow transplantation. Human embryonic stem cells may be grown in vivo and stimulated to produce pancreatic -cells and later transplanted to the patient. Its success depends on response of the patients immune system and ability of the transplanted cells to proliferate, differentiate and integrate with the target tissue.

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4th InternationalConference on Plant GenomicsJuly 14-15, 2016 Brisbane, Australia; 8thWorld Congress on Stem Cell ResearchMarch 20-22, 2017 Orlando, USA; 7thAnnual Conference on Stem Cell and Regenerative MedicineAug 4-5, 2016, Manchester, UK; 2nd InternationalConference on Tissue preservation and BiobankingSeptember 12-13, 2016 Philadelphia, USA, USA;World Congress on Human GeneticsOctober 31- November 02, 2016 Valencia, Spain; 12thEuro Biotechnology CongressNovember 7-9, 2016 Alicante, Spain; 2nd InternationalConference on Germplasm of Ornamentals, Aug 8-12, 2016, Atlanta, USA; 7th Internationalconference on Crop Science, Aug 1419 2016, Beijing, China;Plant Epigenetics: From Genotype to Phenotype, Feb 1519 2016, Taos, USA;Germline Stem Cells Conference, June 1921 2016, San Francisco, USA;Conference on Water Stressin Plants, 29 May 3 June 2016, Ormont-Dessus, Switzerland

Track 04: Novel Stem Cell Technologies:

Stem cell technology is a rapidly developing field that combines the efforts of cell biologists, geneticists, and clinicians and offers hope of effective treatment for a variety of malignant and non-malignant diseases. Stem cells are defined as totipotent progenitor cells capable of self-renewal and multilineage differentiation. Stem cells survive well and show stable division in culture, making them ideal targets for in vitro manipulation. Although early research has focused on haematopoietic stem cells, stem cells have also been recognised in other sites. Research into solid tissue stem cells has not made the same progress as that on haematopoietic stem cells.

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InternationalConference on Next Generation SequencingJuly 21-22, 2016 Berlin, Germany; 5th InternationalConference on Computational Systems BiologyAugust 22-23, 2016 Philadelphia, USA; 7th InternationalConference on BioinformaticsOctober 27-28, 2016 Chicago, USA; InternationalConference on Synthetic BiologySeptember 28-30, 2015 Houston, USA; 4th InternationalConference on Integrative BiologyJuly 18-20, 2016 Berlin, Germany; 1st InternationalConference on Pharmaceutical BioinformaticsJan 2426 2016, Pattaya, Thailand; EMBL Conference: TheEpitranscriptome, Apr 2022 2016, Heidelberg, Germany; 2016Whole-Cell ModelingSummer School, Apr 38 2016, Barcelona, Spain; 3rd InternationalMolecular Pathological Epidemiology, May 1213 2016, Boston, USA; 5thDrug FormulationSummit, Jan 2527 2016, Philadelphia, USA

Track 05: Stem Cell Treatment:

Bone marrow transplant is the most extensively used stem-cell treatment, but some treatment derived from umbilical cord blood are also in use. Research is underway to develop various sources for stem cells, and to apply stem-cell treatments for neurodegenerative diseases and conditions, diabetes, heart disease, and other conditions.

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7th InternationalConference on BioinformaticsOctober 27-28, 2016 Chicago, USA; InternationalConference on Synthetic BiologySeptember 28-30, 2015 Houston, USA; 7thAnnual Conference on Stem Cell and Regenerative MedicineAug 4-5, 2016, Manchester, UK; 4th InternationalConference on Integrative BiologyJuly 18-20, 2016 Berlin, Germany; 1st InternationalConference on Pharmaceutical BioinformaticsJan 2426 2016, Pattaya, Thailand; EMBL Conference: TheEpitranscriptome, Apr 2022 2016, Heidelberg, Germany; 2016Whole-Cell ModelingSummer School, Apr 38 2016, Barcelona, Spain; 3rd InternationalMolecular Pathological Epidemiology, May 1213 2016, Boston, USA; 5thDrug FormulationSummit, Jan 2527 2016, Philadelphia, USA

Track 06: Stem cell apoptosis and signal transduction:

Apoptosis is the process of programmed cell death (PCD) that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, chromosomal DNA fragmentation, and global mRNA decay. Most cytotoxic anticancer agents induce apoptosis, raising the intriguing possibility that defects in apoptotic programs contribute to treatment failure. Because the same mutations that suppress apoptosis during tumor development also reduce treatment sensitivity, apoptosis provides a conceptual framework to link cancer genetics with cancer therapy.

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InternationalConference on Restorative MedicineOctober 24-26, 2016 Chicago, USA;; 3rdWorld Congress onHepatitis and Liver Diseases October 17-19, 2016 Dubai, UAE; InternationalConference on Molecular BiologyOctober 13-15, 2016 Dubai, UAE; 2nd InternationalConference on Tissue preservation and Biobanking September12-13, 2016 Philadelphia USA; 26thEuropean Congress ofClinical Microbiology, April 912 2016, Istanbul, Turkey;Conference onCell Growth and Regeneration, Jan 1014 2016, Breckenridge, USA ;

Track 07: Stem Cell Biomarkers:

Molecular biomarkers serve as valuable tools to classify and isolate embryonic stem cells (ESCs) and to monitor their differentiation state by antibody-based techniques. ESCs can give rise to any adult cell type and thus offer enormous potential for regenerative medicine and drug discovery. A number of biomarkers, such as certain cell surface antigens, are used to assign pluripotent ESCs; however, accumulating evidence suggests that ESCs are heterogeneous in morphology, phenotype and function, thereby classified into subpopulations characterized by multiple sets of molecular biomarkers.

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8thWorld Congress on Stem Cell ResearchMarch 20-22, 2017 Orlando, USA; 5th International Conference onCell and Gene TherapyMay 19-21, 2016 San Antonio, USA; 7thAnnual Conference on Stem Cell and Regenerative MedicineAug 4-5, 2016, Manchester, UK; InternationalConference on Restorative MedicineOctober 24-26, 2016 Chicago, USA; InternationalConference on Molecular BiologyOctober 13-15, 2016 Dubai, UAE; 2nd InternationalConference on Tissue preservation and Biobanking September12-13, 2016 Philadelphia USA;Conference on Cardiac Development, Regeneration and RepairApril 3 7, 2016 Snowbird, Utah, USA; Stem Cell DevelopmentMay 22-26, 2016 Hillerd, Denmark; Conference onHematopoietic Stem Cells, June 3-5, 2016 Heidelberg, Germany; ISSCR Pluripotency - March 22-24, 2016 Kyoto, Japan

Track 08: Cellular therapies:

Cellular therapy also called Cell therapy is therapy in which cellular material is injected into a patient, this generally means intact, living cells. For example, T cells capable of fighting cancer cells via cell-mediated immunity may be injected in the course of immunotherapy.

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InternationalConference on Genetic Counseling and Genomic MedicineAugust 11-12, 2016 Birmingham, UK;World Congress on Human GeneticsOctober 31- November 02, 2016 Valencia, Spain; InternationalConference on Molecular BiologyOctober 13-15, 2016 Dubai, UAE; 3rd InternationalConference on Genomics & PharmacogenomicsSeptember 21-23, 2015 San Antonio, USA; EuropeanConference on Genomics and Personalized MedicineApril 25-27, 2016 Valencia, Spain;Genomics and Personalized Medicine, Feb 711 2016, Banff, Canada; Drug Discovery for Parasitic Diseases, Jan 2428 2016, Tahoe City, USA; Heart Failure: Genetics,Genomics and Epigenetics, April 37 2016, Snowbird, USA; Understanding the Function ofHuman Genome Variation, May 31 June 4 2016, Uppsala, Sweden; 5thDrug Formulation SummitJan2527,2016,Philadelphia, USA

Track 09: Stem cells and cancer:

Cancer can be defined as a disease in which a group of abnormal cells grow uncontrollably by disregarding the normal rules of cell division. Normal cells are constantly subject to signals that dictate whether the cells should divide, differentiate into another cell or die. Cancer cells develop a degree of anatomy from these signals, resulting in uncontrolled growth and proliferation. If this proliferation is allowed to continue and spread, it can be fatal.

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2ndWorld Congress on Applied MicrobiologyOctober 31-November 02, 2016 Istanbul, Turkey; InternationalConference on Infectious Diseases & Diagnostic MicrobiologyOct 3-5, 2016 Vancouver, Canada;18th International conference on Neuroscience, April 26 2016, Sweden, Austria; 6th Annual Traumatic Brain Injury Conference, May 1112 2016, Washington, D.C., USA; Common Mechanisms of Neurodegeneration, June 1216 2016, Keystone, USA; Neurology Caribbean Cruise, Aug 2128 2016, Fort Lauderdale, USA; Annual Meeting of the German Society ofNeurosurgery(DGNC), June 1215 2016, Frankfurt am Main, Germany

Track 10: Embryonic stem cells:

Embryonic stem cells have a major potential for studying early steps of development and for use in cell therapy. In many situations, however, it will be necessary to genetically engineer these cells. A novel generation of lentivectors which permit easy genetic engineering of mouse and human embryonic stem cells.

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4thCongress on Bacteriology and Infectious DiseasesMay 16-18, 2016 San Antonio, USA; 2ndWorld Congress on Applied MicrobiologyOctober 31-November 02, 2016 Istanbul, Turkey; InternationalConference on Infectious Diseases & Diagnostic MicrobiologyOct 3-5, 2016 Vancouver, Canada; InternationalConference on Water MicrobiologyJuly 18-20, 2016 Chicago, USA; 5th InternationalConference on Clinical MicrobiologyOctober 24-26, 2016 Rome, Italy; Axons: FromCell Biologyto Pathology Conference, 2427 January 2016, Santa Fe, USA; 26th EuropeanCongress of Clinical MicrobiologyApril 912 2016, Istanbul, Turkey;Conference on Gut Microbiota, Metabolic Disorders and Beyond, April 1721 2016, Newport, USA; 7th EuropeanSpores Conference, April 1820 2016, Egham, UK; New Approaches to Vaccines forHuman and Veterinary Tropical Diseases, May 2226 2016, Cape Town, South Africa

Track 11: Cell differentiation and disease modeling:

Cellular differentiation is the progression, whereas a cell changes from one cell type to another. Variation occurs numerous times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and create fully differentiated daughter cells during tissue repair and during normal cell turnover. Some differentiation occurs in response to antigen exposure. Differentiation dramatically changes a cell's size, shape, membrane potential, metabolic activity, and responsiveness to signals. These changes are largely due to highly controlled modifications in gene expression and are the study of epigenetics. With a few exceptions, cellular differentiationalmost never involves a change in the DNA sequence itself. Thus, different cells can have very different physical characteristics despite having the same genome.

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4thCongress on Bacteriology and Infectious DiseasesMay 16-18, 2016 San Antonio, USA; 2ndWorld Congress on Applied MicrobiologyOctober 31-November 02, 2016 Istanbul, Turkey; InternationalConference on Infectious Diseases & Diagnostic MicrobiologyOct 3-5, 2016 Vancouver, Canada; InternationalConference on Water MicrobiologyJuly 18-20, 2016 Chicago, USA; 5thInternationalConference on Clinical MicrobiologyOctober 24-26, 2016 Rome, Italy; Axons: FromCell Biologyto Pathology Conference, 2427 January 2016, Santa Fe, USA; 26thEuropeanCongress of Clinical MicrobiologyApril 912 2016, Istanbul, Turkey;Conference on Gut Microbiota, Metabolic Disorders and Beyond, April 1721 2016, Newport, USA; 7thEuropeanSpores Conference, April 1820 2016, Egham, UK; New Approaches toVaccines forHuman and Veterinary Tropical Diseases, May 2226 2016, Cape Town, South Africa

Track 12: Tissue engineering:

Tissue Engineering is the study of the growth of new connective tissues, or organs, from cells and a collagenous scaffold to produce a fully functional organ for implantation back into the donor host. Powerful developments in the multidisciplinary field of tissue engineering have produced a novel set of tissue replacement parts and implementation approaches. Scientific advances in biomaterials, stem cells, growth and differentiation factors, and biomimetic environments have created unique opportunities to fabricate tissues in the laboratory from combinations of engineered extracellular matrices cells, and biologically active molecules.

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4thCongress on Bacteriology and Infectious DiseasesMay 16-18, 2016 San Antonio, USA; 2ndWorld Congress on Applied MicrobiologyOctober 31-November 02, 2016 Istanbul, Turkey; InternationalConference on Infectious Diseases & Diagnostic MicrobiologyOct 3-5, 2016 Vancouver, Canada; InternationalConference on Water MicrobiologyJuly 18-20, 2016 Chicago, USA; 5thInternationalConference on Clinical MicrobiologyOctober 24-26, 2016 Rome, Italy; Axons: FromCell Biologyto Pathology Conference, 2427 January 2016, Santa Fe, USA; 26thEuropeanCongress of Clinical MicrobiologyApril 912 2016, Istanbul, Turkey;Conference on Gut Microbiota, Metabolic Disorders and Beyond, April 1721 2016, Newport, USA; 7thEuropeanSpores Conference, April 1820 2016, Egham, UK; New Approaches toVaccines forHuman and Veterinary Tropical Diseases, May 2226 2016, Cape Town, South Africa

Track 13: Stem cell plasticity and reprogramming:

Stem cell plasticity denotes to the potential of stem cells to give rise to cell types, previously considered outside their normal repertoire of differentiation for the location where they are found. Included under this umbrella title is often the process of transdifferentiation the conversion of one differentiated cell type into another, and metaplasia the conversion of one tissue type into another. From the point of view of this entry, some metaplasias have a clinical significance because they predispose individuals to the development of cancer.

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InternationalConference on Case ReportsMarch 31-April 02, 2016 Valencia, Spain; 2nd International Meeting onClinical Case ReportsApril 18-20, 2016 Dubai, UAE; 3rd Experts Meeting onMedical Case ReportsMay 09-11, 2016 New Orleans, Louisiana, USA; 12thEuro BiotechnologyCongress November 7-9, 2016 Alicante, Spain; 2nd International Conference onTissue preservation and BiobankingSeptember 12-13, 2016 Philadelphia, USA; 11thWorld Conference BioethicsOctober 20-22, 2015 Naples, Italy;Annual Conference Health Law and Bioethics, May 6-7 2016 Cambridge, MA, USA; 27th Maclean Conference on Clinical Medical Ethics, Nov 13-14, 2015, Chicago, USA; CFP: Global Forum on Bioethics in Research, Nov 3-4, 2015, Annecy, France

Track 14: Gene therapy and stem cells

Gene therapy is the therapeutic delivery of nucleic acid polymers into a patient's cells as a drug to treat disease. Gene therapy could be a way to fix a genetic problem at its source. The polymers are either expressed as proteins, interfere with protein expression, or possibly correct genetic mutations. In the future, this technique may allow doctors to treat a disorder by inserting a gene into a patient's cells instead of using drugs or surgery.

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Track 15: Tumour cell science:

An abnormal mass of tissue. Tumors are a classic sign of inflammation, and can be benign or malignant. Tomour usually reflect the kind of tissue they arise in. Treatment is also specific to the location and type of the tumor. Benign tumors can sometimes simply be ignored, cancerous tumors; options include chemotherapy, radiation, and surgery.

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Track 16: Reprogramming stem cells: computational biology

Computational Biology, sometimes referred to as bioinformatics, is the science of using biological data to develop algorithms and relations among various biological systems. Bioinformatics groups use computational methods to explore the molecular mechanisms underpinning stem cells. To accomplish this bioinformaticsdevelop and apply advanced analysis techniques that make it possible to dissect complex collections of data from a wide range of technologies and sources.

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The fields of stem cell biology and regenerative medicine research are fundamentally about understanding dynamic cellular processes such as development, reprogramming, repair, differentiation and the loss, acquisition or maintenance of pluripotency. In order to precisely decipher these processes at a molecular level, it is critical to identify and study key regulatory genes and transcriptional circuits. Modern high-throughput molecular profiling technologies provide a powerful approach to addressing these questions as they allow the profiling of tens of thousands of gene products in a single experiment. Whereas bioinformatics is used to interpret the information produced by such technologies.

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8th World Congress on Cell & Stem Cell Research

The success of the 7 Cell Science conferences series has given us the prospect to bring the gathering one more time for our 8thWorld Congress 2017 meet in Orlando, USA. Since its commencement in 2011 cell science series has perceived around 750 researchers of great potentials and outstanding research presentations around the globe. The awareness of stem cells and its application is increasing among the general population that also in parallel offers hope and add woes to the researchers of cell science due to the potential limitations experienced in the real-time.

Stem Cell Research-2017has the goal to fill the prevailing gaps in the transformation of this science of hope to promptly serve solutions to all in the need.World Congress 2017 will have an anticipated participation of 100-120 delegates from around the world to discuss the conference goal.

History of Stem cells Research

Stem cells have an interesting history, in the mid-1800s it was revealed that cells were basically the building blocks of life and that some cells had the ability to produce other cells. Efforts were made to fertilize mammalian eggs outside of the human body and in the early 1900s, it was discovered that some cells had the capacity to generate blood cells. In 1968, the first bone marrow transplant was achieved successfully to treat two siblings with severe combined immunodeficiency. Other significant events in stem cell research include:

1978: Stem cells were discovered in human cord blood 1981: First in vitro stem cell line developed from mice 1988: Embryonic stem cell lines created from a hamster 1995: First embryonic stem cell line derived from a primate 1997: Cloned lamb from stem cells 1997: Leukaemia origin found as haematopoietic stem cell, indicating possible proof of cancer stem cells

Funding in USA:

No federal law forever did embargo stem cell research in the United States, but only placed restrictions on funding and use, under Congress's power to spend. By executive order on March 9, 2009, President Barack Obama removed certain restrictions on federal funding for research involving new lines of humanembryonic stem cells. Prior to President Obama's executive order, federal funding was limited to non-embryonic stem cell research and embryonic stem cell research based uponembryonic stem celllines in existence prior to August 9, 2001. In 2011, a United States District Court "threw out a lawsuit that challenged the use of federal funds for embryonic stem cell research.

Members Associated with Stem Cell Research:

Discussion on Development, Regeneration, and Stem Cell Biology takes an interdisciplinary approach to understanding the fundamental question of how a single cell, the fertilized egg, ultimately produces a complex fully patterned adult organism, as well as the intimately related question of how adult structures regenerate. Stem cells play critical roles both during embryonic development and in later renewal and repair. More than 65 faculties in Philadelphia from both basic science and clinical departments in the Division of Biological Sciences belong to Development, Regeneration, and Stem Cell Biology. Their research uses traditional model species including nematode worms, fruit-flies, Arabidopsis, zebrafish, amphibians, chick and mouse as well as non-traditional model systems such as lampreys and cephalopods. Areas of research focus include stem cell biology, regeneration, developmental genetics, and cellular basis of development, developmental neurobiology, and evo-devo (Evolutionary developmental biology).

Stem Cell Market Value:

Worldwide many companies are developing and marketing specialized cell culture media, cell separation products, instruments and other reagents for life sciences research. We are providing a unique platform for the discussions between academia and business.

Global Tissue Engineering & Cell Therapy Market, By Region, 2009 2018

$Million

Why to attend???

Stem Cell Research-2017 could be an outstanding event that brings along a novel and International mixture of researchers, doctors, leading universities and stem cell analysis establishments creating the conference an ideal platform to share knowledge, adoptive collaborations across trade and world, and assess rising technologies across the world. World-renowned speakers, the most recent techniques, tactics, and the newest updates in cell science fields are assurances of this conference.

A Unique Opportunity for Advertisers and Sponsors at this International event:

http://stemcell.omicsgroup.com/sponsors.php

UAS Major Universities which deals with Stem Cell Research

University of Washington/Hutchinson Cancer Center

Oregon Stem Cell Center

University of California Davis

University of California San Francisco

University of California Berkeley

Stanford University

Mayo Clinic

Major Stem Cell Organization Worldwide:

Norwegian Center for Stem Cell Research

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Stem Cell Conferences | Cell and Stem Cell Congress | Stem ...

Frontiers in Biotechnology

Biotechnology is an innovative science in which living systems and organisms are used to develop new and useful products, ranging from healthcare products to seeds. The field of Biotechnology is growing rapidly making tremendous impacts in Medical/Health Care, Food & Agriculture. The Global Biotechnology industry is in the growth phase of its economic life cycle. Over the five years to 2014, revenue and industry value added (IVA) growth have outpaced world GDP growth. The Frontiers in Biotechnology track will cover current technological aspects that aim at obtaining products with scientific, industrial, health and agricultural applications, from organisms with increasing levels of complexity from bacteria, yeast, plants, animal cells and virus. With the lectures and demonstrations on stem cell therapy, Embryo transfer technology, next generation sequencing, Drug discovery, biotechnology in food and dairy, etc The participants are expected to acquire knowledge in techniques and methodologies used in Biotechnology.

Pharmaceutical Biotechnology

Pharmaceutical Biotechnology is the science that covers all technologies required for producing, manufacturing and registration of biological drugs.Pharmaceutical Biotechnologyis an increasingly important area of science and technology. It contributes in design and delivery of new therapeutic drugs,diagnosticagents for medical tests, and in gene therapy for correcting the medical symptoms of hereditary diseases. The Pharmaceutical Biotechnology is widely spread, ranging from many ethical issues to changes inhealthcarepracticesand a significant contribution to the development of national economy.Biopharmaceuticalsconsists of large biological molecules which areproteins. They target the underlying mechanisms and pathways of a disease or ailment; it is a relatively young industry. They can deal with targets in humans that are not accessible withtraditional medicines.

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11th World Congress onBiotechnology and Biotech Industries Meet, July 28-29, 2016, Berlin, Germany; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 11thEuro Biotechnology Congress, November 07-09,2016, Alicante Spain; 13thBiotechnology Congress, Nov 28-30, 2016, San Francisco, USA;Global Biotechnology Congress2016, May 11th 14th 2016, Boston, MA, USA;Biomarker Summit2016, March 21-23, 2016 San Diego, CA, USA; 14thVaccines Research & Development, July 7-8, Boston, USA;Pharmaceutical & BiotechPatent Litigation Forum, Mar 14 15, 2016, Amsterdam, Netherlands; 4thBiomarkers in Diagnostics, Oct 07-08, 2015 Berlin, Germany, DEU.

Medical Biotechnology

Medicine is by means of biotechnology techniques so much in diagnosing and treating dissimilar diseases. It also gives opportunity for the population to defend themselves from hazardous diseases. The pasture of biotechnology, genetic engineering, has introduced techniques like gene therapy, recombinant DNA technologyand polymerase chain retort which employ genes and DNA molecules to make adiagnosis diseasesand put in new and strong genes in the body which put back the injured cells. There are some applications of biotechnology which are live their part in the turf of medicine and giving good results.

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11th World Congress onBiotechnology and Biotech Industries Meet, July 28-29, 2016, Berlin, Germany; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 11thEuro Biotechnology Congress, November 07-09,2016, Alicante Spain; 13thBiotechnology Congress, Nov 28-30, 2016, San Francisco, USA;Global Biotechnology Congress2016, May 11th 14th 2016, Boston, MA, USA;Biomarker Summit2016, March 21-23, 2016 San Diego, CA, USA; 14thVaccines Research & Development, July 7-8, Boston, USA;Pharmaceutical & Biotech Patent Litigation Forum, Mar 14 15, 2016, Amsterdam, Netherlands; 4thBiomarkers in Diagnostics, Oct 07-08, 2015 Berlin, Germany, DEU.

Molecular Biotechnology

Molecular biotechnology is the use of laboratory techniques to study and modify nucleic acids and proteins for applications in areas such as human and animal health, agriculture, and the environment.Molecular biotechnologyresults from the convergence of many areas of research, such as molecular biology, microbiology, biochemistry, immunology, genetics, and cell biology. It is an exciting field fueled by the ability to transfer genetic information between organisms with the goal of understanding important biological processes or creating a useful product.

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11th World Congress onBiotechnology and Biotech IndustriesMeet, July 28-29, 2016, Berlin, Germany; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 13thBiotechnology Congress, Nov 28-30, 2016, San Francisco, USA; GlobalBiotechnology Congress2016, May 11th-14th 2016, Boston, MA, USA;BIO Investor Forum, October 20-21, 2015, San Francisco, USA;BIO Latin America Conference, October 14-16, 2015, Rio de Janeiro, Brazil;Bio Pharm America 20158th Annual International Partnering Conference, September 15-17, 2015, Boston, MA, USA.

Environmental Biotechnology

The biotechnology is applied and used to study the natural environment. Environmental biotechnology could also imply that one try to harness biological process for commercial uses and exploitation. It is the development, use and regulation of biological systems for remediation of contaminated environment and forenvironment-friendly processes(green manufacturing technologies and sustainable development). Environmental biotechnology can simply be described as the optimal use of nature, in the form of plants, animals, bacteria, fungi and algae, to producerenewable energy, food and nutrients in a synergistic integrated cycle of profit making processes where the waste of each process becomes the feedstock for another process.

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11th World Congress onBiotechnology and Biotech IndustriesMeet, July 28-29, 2016, Berlin, Germany; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 11thEuro Biotechnology Congress, November 07-09,2016, Alicante Spain; 13thBiotechnology Congress, Nov 28-30, 2016, San Francisco, USA; GlobalBiotechnology Congress2016, May 11th 14th 2016, Boston, MA, USA;Biomarker Summit2016, March 21-23, 2016 San Diego, CA, USA; 14thVaccines Research & Development, July 7-8, Boston, USA;Pharmaceutical & BiotechPatent Litigation Forum, Mar 14 15, 2016, Amsterdam, Netherlands

Animal Biotechnology

It improves the food we eat meat, milk and eggs. Biotechnology can improve an animals impact on the environment. Animalbiotechnologyis the use of science and engineering to modify living organisms. The goal is to make products, to improve animals and to developmicroorganismsfor specific agricultural uses. It enhances the ability to detect, treat and prevent diseases, include creating transgenic animals (animals with one or more genes introduced by human intervention), using gene knock out technology to make animals with a specific inactivated gene and producing nearly identical animals by somatic cell nuclear transfer (or cloning).

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11th World Congress onBiotechnology and Biotech Industries Meet, July 28-29, 2016, Berlin, Germany; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 11thEuro Biotechnology Congress, November 07-09,2016, Alicante Spain; 13thBiotechnology Congress, Nov 28-30, 2016, San Francisco, USA;Global Biotechnology Congress2016, May 11th 14th 2016, Boston, MA, USA;Biomarker Summit2016, March 21-23, 2016 San Diego, CA, USA; 14thVaccines Research & Development, July 7-8, Boston, USA;Pharmaceutical & BiotechPatent Litigation Forum, Mar 14 15, 2016, Amsterdam, Netherlands; 4thBiomarkers in Diagnostics, Oct 07-08, 2015 Berlin, Germany, DEU.

Agricultural Biotechnology

Biotechnology is being used to address problems in all areas of agricultural production and processing. This includesplant breedingto raise and stabilize yields; to improve resistance to pests, diseases and abiotic stresses such as drought and cold; and to enhance the nutritional content of foods. Modern agricultural biotechnology improves crops in more targeted ways. The best known technique is genetic modification, but the term agricultural biotechnology (or green biotechnology) also covers such techniques asMarker Assisted Breeding, which increases the effectiveness of conventional breeding.

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3rd GlobalFood Safety Conference, September 01-03, 2016, Atlanta USA; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 11thEuro Biotechnology Congress, November 07-09,2016, Alicante Spain; 12thBiotechnology Congress, Nov 14-15, 2016, San Francisco, USA;Biologically Active Compoundsin Food, October 15-16 2015 Lodz, Poland; World Conference onInnovative Animal Nutrition and Feeding, October 15-17, 2015 Budapest, Hungary; 18th International Conference onFood Science and Biotechnology, November 28 29, 2016, Istanbul, Turkey; 18th International Conference on Agricultural Science, Biotechnology,Food and Animal Science, January 7 8, 2016, Singapore; International IndonesiaSeafood and Meat, 1517 October 2016, Jakarta, Indonesia.

Industrial Biotechnology

Industrial biotechnology is the application of biotechnology for industrial purposes, includingindustrial fermentation. The practice of using cells such as micro-organisms, or components of cells like enzymes, to generate industrially useful products in sectors such as chemicals, food and feed, detergents, paper and pulp, textiles andbiofuels. Industrial Biotechnology offers a premier forum bridging basic research and R&D with later-stage commercialization for sustainable bio based industrial and environmental applications.

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11th World Congress onBiotechnology and Biotech Industries Meet, July 28-29, 2016, Berlin, Germany; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 11thEuro Biotechnology Congress, November 07-09,2016, Alicante Spain; 13thBiotechnology Congress, Nov 28-30, 2016, San Francisco, USA; GlobalBiotechnology Congress2016, May 11th 14th 2016, Boston, MA, USA;Biomarker Summit2016, March 21-23, 2016 San Diego, CA, USA; 14thVaccines Research & Development, July 7-8, Boston, USA;Pharmaceutical & BiotechPatent Litigation Forum, Mar 14 15, 2016, Amsterdam, Netherlands; 4thBiomarkers in Diagnostics, Oct 07-08, 2015 Berlin, Germany, DEU.

Microbial Biotechnology

Microorganisms have been exploited for their specific biochemical and physiological properties from the earliest times for baking, brewing, and food preservation and more recently for producingantibiotics, solvents, amino acids, feed supplements, and chemical feedstuffs. Over time, there has been continuous selection by scientists of special strains ofmicroorganisms, based on their efficiency to perform a desired function. Progress, however, has been slow, often difficult to explain, and hard to repeat. Recent developments inmolecular biologyand genetic engineering could provide novel solutions to long-standing problems. Over the past decade, scientists have developed the techniques to move a gene from one organism to another, based on discoveries of how cells store, duplicate, and transfer genetic information.

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3rdGlobal Food Safety Conference, September 01-03, 2016, Atlanta USA; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 11thEuro Biotechnology Congress, November 07-09,2016, Alicante Spain; 12thBiotechnology Congress, Nov 14-15, 2016, San Francisco, USA;Biologically Active Compoundsin Food, October 15-16 2015 Lodz, Poland; World Conference onInnovative Animal Nutrition and Feeding, October 15-17, 2015 Budapest, Hungary; 18th International Conference onFood Science and Biotechnology, November 28 29, 2016, Istanbul, Turkey; 18th International Conference on Agricultural Science, Biotechnology,Food and Animal Science, January 7 8, 2016, Singapore; International IndonesiaSeafood and Meat, 1517 October 2016, Jakarta, Indonesia.

Food Biotechnology

Food processing is a process by which non-palatable and easily perishable raw materials are converted to edible and potable foods and beverages, which have a longer shelf life. Biotechnology helps in improving the edibility, texture, and storage of the food; in preventing the attack of the food, mainly dairy, by the virus like bacteriophage producing antimicrobial effect to destroy the unwanted microorganisms in food that cause toxicity to prevent the formation and degradation of other toxins andanti-nutritionalelements present naturally in food.

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11th World Congress onBiotechnology and Biotech Industries Meet, July 28-29, 2016, Berlin, Germany; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 13thBiotechnology Congress, Nov 28-30, 2016, San Francisco, USA;Global Biotechnology Congress 2016, May 11th-14th 2016, Boston, MA, USA;BIO Investor Forum, October 20-21, 2015, San Francisco, USA;BIO Latin America Conference, October 14-16, 2015, Rio de Janeiro, Brazil;Bio Pharm America 20158th Annual International Partnering Conference, September 15-17, 2015, Boston, MA, USA.

Genetic Engineering and Biotechnology

One kind of biotechnology is gene technology, sometimes called genetic engineering orgenetic modification, where the genetic material of living things is deliberately altered to enhance or remove a particular trait and allow the organism to perform new functions. Genes within a species can be modified, or genes can be moved from one species to another. Genetic engineering has applications inmedicine, research, agriculture and can be used on a wide range of plants, animals and microorganisms. It resulted in a series of medical products. The first two commercially prepared products from recombinant DNA technology were insulin andhuman growth hormone, both of which were cultured in the E. coli bacteria.

The field of molecular biology overlaps with biology and chemistry and in particular, genetics and biochemistry. A key area of molecular biology concerns understanding how various cellular systems interact in terms of the way DNA, RNA and protein synthesis function.

Related Conferences

11th World Congress onBiotechnology and Biotech Industries Meet, July 28-29, 2016, Berlin, Germany; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 11thEuro Biotechnology Congress, November 07-09,2016, Alicante Spain; 13thBiotechnology Congress, Nov 28-30, 2016, San Francisco, USA;Global Biotechnology Congress2016, May 11th 14th 2016, Boston, MA, USA;Biomarker Summit2016, March 21-23, 2016 San Diego, CA, USA; 14thVaccines Research & Development, July 7-8, Boston, USA;Pharmaceutical & BiotechPatent Litigation Forum, Mar 14 15, 2016, Amsterdam, Netherlands; 4thBiomarkers in Diagnostics, Oct 07-08, 2015 Berlin, Germany, DEU.

Biotechnology Investor & partnering Forum

The Biotech Investor & Partnering Forum is one of the unique conclave focused on the management and economics of biotechnology which became so important as the field is growing on a fast paced. From agriculture and environment sectors to pharmaceutical and healthcare products and services, the industries and institutions emerging from the biotech revolution Bio-Based Economy represent one of the largest and most steadily growing building blocks of the Global economy. The social impact is overwhelming, generating tremendous progress in quality of life but also difficult issues that needs responsible management based on consumer & bio-industry perspective, solid ethical principles, growing intellectual property rights complexity, long drug development times, Bio security, unusual market structures and highly unpredictable outcomes are just some of the challenges facing biotechnology management today.

Related Conferences

11th World Congress onBiotechnology and Biotech Industries Meet, July 28-29, 2016, Berlin, Germany; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 11thEuro Biotechnology Congress, November 07-09,2016, Alicante Spain; 13thBiotechnology Congress, Nov 28-30, 2016, San Francisco, USA;Global Biotechnology Congress2016, May 11th 14th 2016, Boston, MA, USA;Biomarker Summit2016, March 21-23, 2016 San Diego, CA, USA; 14thVaccines Research & Development, July 7-8, Boston, USA;Pharmaceutical & BiotechPatent Litigation Forum, Mar 14 15, 2016, Amsterdam, Netherlands; 4thBiomarkers in Diagnostics, Oct 07-08, 2015 Berlin, Germany, DEU.

Nano Biotechnology

Nano biotechnology, bio nanotechnology, and Nano biology are terms that refer to the intersection of nanotechnology and biology. Bio nanotechnology and Nano biotechnology serve as blanket terms for various related technologies. The most important objectives that are frequently found inNano biologyinvolve applying Nano tools to relevantmedical/biologicalproblems and refining these applications. Developing new tools, such as peptide Nano sheets, for medical and biological purposes is another primary objective in nanotechnology.

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8thWorldMedicalNanotechnologyCongress& Expo during June 9-11, Dallas, USA; 6thGlobal Experts Meeting and Expo onNanomaterialsand Nanotechnology, April 21-23, 2016 ,Dubai, UAE; 12thNanotechnologyProductsExpo, Nov 10-12, 2016 at Melbourne, Australia; 5thInternationalConference onNanotekand Expo, November 16-18, 2015 at San Antonio, USA; 11thInternational Conference and Expo onNano scienceandMolecular Nanotechnology, September 26-28 2016, London, UK; 18thInternational Conference onNanotechnologyand Biotechnology, February 4 5, 2016 in Melbourne, Australia; 16thInternational Conference onNanotechnology, August 22-25, 2016 in Sendai, Japan; International Conference onNano scienceand Nanotechnology, 7-11 Feb 2016 in Canberra, Australia; 18thInternational Conference onNano scienceand Nanotechnology, February 15 16, 2016 in Istanbul, Turkey; InternationalNanotechnologyConference& Expo, April 4-6, 2016 in Baltimore, USA.

Animal biotechnology

Animal biotechnology is a branch of biotechnology in which molecular biology techniques are used to genetically engineer animals in order to improve their suitability for pharmaceutical, agricultural or industrial applications. Many animals also help by serving as models of disease. If an animal gets a disease thats similar to humans, we can use that animal to test treatments. Animals are often used to help us understand how new drugs will work and whether or not theyll be safe for humans and effective in treating disease.

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11th World Congress onBiotechnology and Biotech IndustriesMeet, July 28-29, 2016, Berlin, Germany; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 11thEuro Biotechnology Congress, November 07-09,2016, Alicante Spain; 12thBiotechnology Congress, Nov 14-15, 2016, San Francisco, USA;BIO IPCC Conference, Cary, North Carolina, USA; World Congress onIndustrial Biotechnology, April 17-20, 2016, San Diego, CA; 6thBio based Chemicals: Commercialization & Partnering, November 16-17, 2015, San Francisco, CA, USA; The European Forum forIndustrial Biotechnology and Bio economy, 27-29 October 2015, Brussels, Belgium; 4thBiotechnology World Congress, February 15th-18th, 2016, Dubai, United Arab Emirates; International Conference on Advances inBioprocess Engineering and Technology, 20th to 22nd January 2016,Kolkata, India; GlobalBiotechnology Congress2016, May 11th 14th 2016, Boston, MA, USA

Biotechnology Applications

Biotechnology has application in four major industrial areas, including health care (medical), crop production and agriculture, nonfood (industrial) uses of crops and other products (e.g. biodegradable plastics, vegetable oil, biofuels), and environmental uses. AppliedMicrobiologyand Biotechnology focusses on prokaryotic or eukaryotic cells, relevant enzymes and proteins, applied genetics and molecular biotechnology,genomicsand proteomics, applied microbial and cell physiology, environmental biotechnology, process and products and more.

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3rd GlobalFood Safety Conference, September 01-03, 2016, Atlanta USA; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, Thailand; 11thEuro Biotechnology Congress, November 07-09,2016, Alicante Spain; 12thBiotechnology Congress, Nov 14-15, 2016, San Francisco, USA;Biologically Active Compoundsin Food, October 15-16 2015 Lodz, Poland; World Conference onInnovative Animal Nutrition and Feeding, October 15-17, 2015 Budapest, Hungary; 18th International Conference onFood Science and Biotechnology, November 28 29, 2016, Istanbul, Turkey; 18th International Conference on Agricultural Science, Biotechnology,Food and Animal Science, January 7 8, 2016, Singapore; International IndonesiaSeafood and Meat, 1517 October 2016, Jakarta, Indonesia.

Biotechnology Companies & Market Analysis

From agriculture to environmental science, biotechnology plays an important role in improving industry standards, services, and developing new products. Biotechnology involves the spectrum of life science-based research companies working ontransformative technologiesfor a wide range of industries. While agriculture, material science and environmental science are major areas of research, the largest impact is made in the field medicine. As a large player in the research and development of pharmaceuticals, the role ofbiotechnologyin the healthcare field is undeniable. From genetically analysis and manipulation to the formation of new drugs, many biotech firms are transforming into pharmaceutical and biopharmaceutical leaders.

Related conferences

10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok; 11thEuroBiotechnologyCongress, November 7-9, 2016 Alicante, Spain; 11th World Congress onBiotechnology and Biotech IndustriesMeet, July 28-29, 2016, Berlin, Germany; 13thBiotechnologyCongress, November 28-30, 2016 San Francisco, USA; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, UAE;BioInternational Convention, June 6-9, 2016 | San Francisco, CA;BiotechJapan, May 11-13, 2016, Tokyo, Japan;NANO BIOEXPO 2016, Jan. 27 29, 2016, Tokyo, Japan;ArabLabExpo2016, March 20-23, Dubai; 14thInternational exhibition for laboratory technology,chemical analysis, biotechnology and diagnostics, 12-14 Apr 2016, Moscow, Russia

Biotechnology Capital & Grants

Every new business needs some startup capital, for research, product development and production, permits and licensing and other overhead costs, in addition to what is needed to pay your staff, if you have any. Biotechnology products arise from successfulbiotechcompanies. These companies are built by talented individuals in possession of a scientific breakthrough that is translated into a product or service idea, which is ultimately brought into commercialization. At the heart of this effort is the biotech entrepreneur, who forms the company with a vision they believe will benefit the lives and health of countless individuals. Entrepreneurs start biotechnology companies for various reasons, but creatingrevolutionary productsand tools that impact the lives of potentially millions of people is one of the fundamental reasons why all entrepreneurs start biotechnology companies.

10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok; 11thEuroBiotechnologyCongress, November 7-9, 2016 Alicante, Spain; 11th World Congress onBiotechnology and Biotech IndustriesMeet, July 28-29, 2016, Berlin, Germany; 13thBiotechnologyCongress, November 28-30, 2016 San Francisco, USA; 10thAsia Pacific Biotech CongressJuly 25-27, 2016, Bangkok, UAE;BioInternational Convention, June 6-9, 2016 | San Francisco, CA;BiotechJapan, May 11-13, 2016, Tokyo, Japan;NANO BIOEXPO 2016, Jan. 27 29, 2016, Tokyo, Japan;ArabLabExpo2016, March 20-23, Dubai; 14thInternational exhibition for laboratory technology,chemical analysis, biotechnology and diagnostics, 12-14 Apr 2016, Moscow, Russia

Scope and Importance

From the simple facts of brewing beer and baking bread has emerged a field now known asBiotechnology. Over the ages the meaning of the word biotechnology has evolved along with our growing technical knowledge. Biotechnology began by using cultured microorganisms to create a variety of food and drinks, despite in early practitioners not even knowing the existence of microbial world. Today, biotechnology is still defined as many application of living organisms or bioprocesses to create new products. Although the underlying idea is unchanged, the use of genetic engineering and other modern scientific techniques has revolutionized the area.

The field of genetics, molecular biology, microbiology, and biochemistry are merging their respective discoveries into the expanding applied field of biotechnology, and advances are occurring at a record pace. Traditional biotechnology goes back thousands of years.

Modern biotechnology applies not only modern genetics but also advances in other sciences. However, there is a third revolution that is just emergingnanotechnology. The development of techniques to visualize and manipulate atoms individually or in small clusters is opening the way to an ever-finer analysis of living systems. Nanoscale techniques are now beginning to play significant roles in many area of biotechnology.

This raises the question of what exactly defines biotechnology. To this there is no real answer. Today, the application of modern genetics or other equivalent modern technology is usually seen as application of modern genetics or equivalent modern technology is usually seen as necessary for a process to count as biotechnology. Thus, the definition of biotechnology has become partly a matter of fashion. Therefore, to classical terms, (modern) biotechnology as resulting in a broaden manner from the merger of classical biotechnology with modern genetics, molecular biology, computer technology, and nanotechnology.

Biotech Congress 2017covers mostly all the allied areas of biotechnology which embraces both the basic sciences, technology and as well as its applications in research, industry and academia. This conference will promote global networking between researchers, institutions, investors, industries, policy makers and students. The conference varied topics in biotechnology like healthcare, environmental, animal, plant, marine, genetic engineering, industrial aspects, food science and bio process.

Through this conference we can get all the relevant information regarding how we can use the advances in the biotechnology for building a better tomorrow by reducing the environmental impacts.

Why Italy?

Rome is the capital of Italy; it is also the countrys largest and most populated comune and fourth-most populous city in the European Union. The Metropolitan City of Rome has a population of 4.3 million residents. The city is located in the central-western portion of the Italian Peninsula, within Lazio (Latium), along the shores of Tiber River. Vatican City is an independent country within the city boundaries of Rome, the only existing example of a country within a city: for this reason Rome has been often defined as capital of two states. Roman mythology dates the founding of Rome at only around 753 BC; the site has been inhabited for much longer, making it one of the oldest continuously occupied cities in Europe. It is referred to as Roma Aeterna (The Eternal City) and Caput Mundi (Capital of the World), two central notions in ancient Roman culture. One of the most important city, Rome, was founded in 753 B.C. by Romulus.

The Apennine Mountains form its backbone and stretch from north to south, with the Tiber River cutting through them in central Italy. Along the northern border, the Alps serve as a natural boundary. The three major bodies of water surrounding Italy are the Adriatic Sea, the Ionian Sea, and the Mediterranean Sea. Ancient Rome is characterized by the seven hills and the Tiber River. The Tiber River flows from the Apennine Mountain, to the Tyrrhenian Sea.

Rome is a sprawling, cosmopolitan city with nearly 3,000 years of globally influential art, architecture and culture on display. In 2005, the city received 19.5 million global visitors, up of 22.1% from 2001. Rome ranked in 2014 as the 14thmos-visited city in the world, 3rd most visited in the European Union, and the most popular tourist attraction in Italy. Its historic center is listed by UNESCO as a World Heritage Site. Monuments and museums such as the Vatican Museums and the Colosseum are among the worlds most visited tourist destinations with both locations receiving millions of tourists a year. Rome hosted the 1960 Summer Olympics and is the seat of United Nations Food and Agriculture Organization (FAO).Rome is the city with the most monuments in the world.

The weather is fantastic in Rome in June, when the average temperature starts off at around 20C and gradually climbs up to 23C-24C as the month progresses.

Congress Highlights:

Biotech Congress 2017 emphasizes on:

Target Audience

CEO, Directors, Vice Presidents, Co-directors, Biotechnologists, Academicians, Biostatistician, Biotechnologists, Clinical Laboratory Scientist, Clinical Metabolomics Data Analyst, Clinicians, Commissioner of Health, Community health workers, CROs, Directors, Environmental Scientists, Food Scientists, Genetic Engineers, Health Economist, Health officials, Healthcare Analyst, Manager of Quality Assurance and Evaluation, Market Access Manager, Marketing Intelligence Associate, Master/PhD students, Medical professionals, Microbiologists, Pharmaceutical Scientists, Physicians, Plant Scientists, Postdoctoral Fellows, Public Health Officer, Public Health Policy Analyst, Research Associates, Research Coordinator, Research Data Analyst, Research Intern, Researchers and faculty, Scientific and Medical Information Assistant, Scientists, Food, Environmental & Plant Scientists, Clinicians, Professors, Health care industrialists, Post Doctorate Fellows, Brand Manufacturers of Consumer Products/ Managers, Pharmaceutical Scientists, Students.

Focusing areas to get more participations & Exhibitions

Why to attend?

Biotech Congress is a remarkable event which brings together a unique and international mix of Biotechnology Researchers, Industrial Biotechnologists, leading Universities and Research Institutions making the congress a perfect platform to share experience, foster collaboration across Industry and Academia, and evaluate emerging technologies across the globe.

Biotechnology in Europe

Only in March a market analysis by British researchers at the University of Cambridge had calculated a market potential of three billion euros for Europe.At present, such Crowd Investing platforms only have a market share of 6.5%, however, the growth forecasts are good. The biotech industry in Europe spends nearly $7.32 billion in R&D and $23.2 billion in revenue. Around 20% of the total marketed medicines, and as much as 50% of all drugs that are in the pipeline, are all healthcare biotech products. The European biotech industry provides employment to approximately 95,000 people. Biotechnology sector makes a substantial contribution to the fundamental EU policy objectives, such as job creation, economic growth, ageing society, public health, environmental protection and sustainable development.

Biotechnology in Italy

The Italian Biotechnology Report by Ernst&Young and Assobiotec, in cooperation with Farmindustria and Italian Trade Promotion Agency, shows that the Italian biotech companies are able to compete outstandingly on the international market, managing to grow despite continuing difficulties in the economic situation. With 394 companies, of which 248 pure biotech, Italy is third in Europe after Germany and the United Kingdom, for the number of pure biotech companies, with a growth trend (+2,5%) in clear contrast with that of the countries that occupy the top ranking positions. With 206 companies operating in the health-care field, the red biotech is the prevalent sector. Looking at the other sectors, 43 green biotech, 34 white biotech, 61 GPET (Genomics, Proteomics and Enabling Technologies) and 50 multi core companies are operating in Italy. 77% of the companies are small (less than 50 employees) and micro (less than 10 employees) enterprises, mainly located in Science and Technology Parks or Incubators. Total revenues in the biotech field amount to 7 billion Euros (+4%). Investments in R&D amount to 1,8 billion Euros (+8%), equal to 25% of total revenues. Italian biotech revenues contributes to 0,7% of GDP and the sector is being considered more and more often as a meta-sector, able to create value and employment and with significant effects on various fields, ranging from textiles to detergents, cosmetics, polymers, paper and animal feed, from paints to food, from treatment of waste to leather treatment, and many others. The future trends of Italian red biotech are connected to a further specialization in oncology, neurology and infectious diseases and to new achievements in the fields of Advanced Therapies and personalized medicine. The analysis of the Italian biotech pipeline shows 319 products for therapeutic use, of which 80 in the preclinical phase, 43 in Phase I, 98 in Phase II and 98 in Phase III. Plant genomics and traceability, preservation and safety of foods, as well as bioremediation and biomasses, are the most promising applications in the green & white fields.

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research IPS Cell Therapy IPS Cell Therapy

Stem cells offer great potential in biomedical engineering due to their pluripotency, which is the ability to multiply indefinitely and also to differentiate and develop into any kind of the hundreds of different cells and bodily tissues. But the precise complexity of how stem cell development is regulated throughout states of cellular change has been difficult to pinpoint until now.

By using powerful new single-cell genetic profiling techniques, scientists at the Wyss Institute for Biologically Inspired Engineering and Boston Children's Hospital have uncovered far more variation in pluripotent stem cells than was previously appreciated. The findings, reported today in Nature, bring researchers closer to a day when many different kinds of stem cells could be leveraged for disease therapy and regenerative treatments.

"Stem cell colonies contain much variability between individual cells. This has been considered somewhat problematic for developing predictive approaches in stem cell engineering," said the study's co-senior author James Collins, Ph.D., who is a Wyss Institute Core Faculty member, the Henri Termeer Professor of Medical Engineering & Science at MIT, and a Professor of Biological Engineering at MIT. "Now, we have discovered that what was previously considered problematic variability could actually be beneficial to our ability to precisely control stem cells."

The research team has learned that there are many small fluctuations in the state of a stem cell's pluripotency that can influence which developmental path it will follow.

It's a very fundamental study but it highlights the wide range of states of pluripotency," said George Daley, study co-senior author, Director of Stem Cell Transplantation at Boston Children's Hospital and a Professor of Biological Chemistry and Molecular Pharmacology at Harvard Medical School. "We've captured a detailed molecular profile of the different states of stem cells."

Taking this into account, researchers are now better equipped to manipulate and precisely control which cell and tissue types will develop from an individual pluripotent stem cell or stem cell colony.

"The study was made possible through the use of novel technologies for studying individual cells, which were developed in part by collaborating groups at the Broad Institute, giving our team an unprecedented view of stem cell heterogeneity at the individual cell level," said Patrick Cahan, co-lead author on the study and Postdoctoral Fellow at Boston Children's Hospital and Harvard Medical School.

Researchers explored the developmental landscape of pluripotent stem cells by perturbing them with variants such as different chemicals, culture environments, and genetic knockouts. Then, they analyzed the individual genetic makeup of each cell to observe micro-fluctuations in each stem cell's state of pluripotency. They discovered many small nuances in the way stem cells are influenced by internal, chemical and environmental cues, revealing a complex "decision making" circuit of developmental regulators.

"These emerging single-cell analytics allow us to classify cells very precisely and identify regulatory circuits that control cell states," said the study's co-lead author Roshan Kumar, a former Wyss Institute Postdoctoral Fellow who is now a Senior Scientist at HiFiBiO Inc. and a Visiting Scholar at the Wyss Institute. "The real motivating force behind this study was to understand the causes and consequences of differences between individual stem cells and how the balance of key regulators within a cell can affect that cell's developmental outcome."

Looking at the findings, the researchers now believe there is a "code" that relates patterns of dynamic behavior in stem cell regulatory circuits to the developmental path a cell ends up taking. By leveraging that code, they hope to dial in precisely to specific individual cell states and to use them for a variety of purposes, such as creating certain cell types that a patient's body may be unable to produce on its own.

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New single-cell analysis reveals complex variations in stem cells