New study on promising stem cell-based therapy for Crohn's disease  Medical Xpress

Read more here:
New study on promising stem cell-based therapy for Crohn's disease - Medical Xpress

World J Stem Cells. 2022 Jan 26; 14(1): 140.

Medical Physiology Department/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt

Oral Pathology Department, Faculty of Dentistry/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt

Human Anatomy and Embryology Department/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt

Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt

Medical Physiology Department/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt

Histology and Cell Biology Department/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt

Medical Biochemistry Department/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt

Medical Biochemistry Department/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt

Medical Physiology Department/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt

Forensic Medicine and Clinical toxicology Department/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt

Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt

Histology and Cell Biology Department/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt. ge.ude.demxela@annahem.awdar

Radwa A Mehanna, Medical Physiology Department/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Alexandria 21500, Egypt;

Supported by Science and Technology Development Fund, No. 28932; and Cardiovascular Research, Education, Prevention Foundation, CVREP - Dr. Wael Al Mahmeed Grant.

Corresponding author: Radwa A Mehanna, MD, PhD, Academic Research, Professor, Executive President, Medical Physiology Department/Center of Excellence for Research in Regenerative Medicine and Applications, Faculty of Medicine, Alexandria University, Al Khartoum Square, Azareeta, Alexandria 21500, Egypt. ge.ude.demxela@annahem.awdar

Received 2021 Feb 26; Revised 2021 Jul 2; Accepted 2022 Jan 6.

Regenerative medicine is the field concerned with the repair and restoration of the integrity of damaged human tissues as well as whole organs. Since the inception of the field several decades ago, regenerative medicine therapies, namely stem cells, have received significant attention in preclinical studies and clinical trials. Apart from their known potential for differentiation into the various body cells, stem cells enhance the organ's intrinsic regenerative capacity by altering its environment, whether by exogenous injection or introducing their products that modulate endogenous stem cell function and fate for the sake of regeneration. Recently, research in cardiology has highlighted the evidence for the existence of cardiac stem and progenitor cells (CSCs/CPCs). The global burden of cardiovascular diseases morbidity and mortality has demanded an in-depth understanding of the biology of CSCs/CPCs aiming at improving the outcome for an innovative therapeutic strategy. This review will discuss the nature of each of the CSCs/CPCs, their environment, their interplay with other cells, and their metabolism. In addition, important issues are tackled concerning the potency of CSCs/CPCs in relation to their secretome for mediating the ability to influence other cells. Moreover, the review will throw the light on the clinical trials and the preclinical studies using CSCs/CPCs and combined therapy for cardiac regeneration. Finally, the novel role of nanotechnology in cardiac regeneration will be explored.

Keywords: Cardiac stem and progenitor cells, Cardiac stem cells secretome, Cardiac stem cells niche and metabolism, Nanotechnology, Clinical trials, Combined therapy

Core Tip: With the growing evidence for the existence of regenerating cardiac stem and progenitor cells, studies to evaluate their therapeutic potential have received increasing attention. Although pre-clinical research and clinical trials have demonstrated promising results, yet the latter were often inconsistent in many aspects thus imposing the need for deeper exploration of the molecular biology and relevant pathways regulating cardiogenesis and cardiac muscle repair. This review gives an insight into cardiac stem and progenitor cells regarding their embryological origin, populations, niche, secretome, and metabolism. It overviews the current preclinical research, including medical nanotechnology, and the clinical trials generally applied for cardiac regeneration.

Cardiovascular diseases are the leading cause of death globally, as stated by the latest report 2019 for the World Health Organization, with 17.9 million deaths per year, accounting for 31% of all deaths worldwide.

The heart is one of the least proliferative organs in the human body, and its minimal regenerative capacity has been dogma for decades. Such dogma has been led by the belief that the heart cannot regenerate from ischemic damage. The absence of primary tumors in the heart has further supported the notion of low proliferation. In an alleged post-mitotic organ, it has been debatable whether cardiac cells repair through activation of resident cardiac stem cells (CSCs) and cardiac progenitor cells (CPCs) or by the proliferation of pre-existing cardiomyocytes (CMs). In 2009, Bergmann et al[1] were the first to refute that notion and have reported that the heart can in fact self-renew. Based on the results obtained from their carbon-14-labelled DNA study to track CMs, Bergmann et al[1] stated that about 50% of CMs renew over the lifespan of an adult. Hsieh et al[2] provided further evidence for the origin of newly generated CMs from progenitor cells in an alpha myosin heavy chain (MHC) transgenic model. They estimated that approximately 15% of CMs can regenerate in adult hearts following ischemic damage. With progression of research, lineage tracing of regenerated cardiac tissue confirmed that the newly regenerated CMs develop from a non-CM and possibly from stem cells (SCs)[2].

Further studies have revealed various CSC/CPC candidates that are morphologically and functionally distinct from each other yet act in a complementary fashion and contribute to the regeneration process. This complex cell aggregation is known as the CSC niche that has been a challenge to characterize and locate anatomically[3].

SC applications have been under intensive research interest since the early 20th century. Many types have been isolated, starting from the embryonic, amniotic, and cord blood mesenchymal stem cells (MSCs) and passing through the adult SCs till the induced pluripotent SCs (iPSCs). Adult MSCs are undifferentiated cells with the same potentials as progenitor cells regarding the ability to differentiate into all three germ layer cells[4]. Exogenous MSCs from various sources, including bone marrow, adipose tissue, umbilical cord, placenta, and amniotic fluid[5], have shown promising results in the treatment of cardiovascular diseases. However, the outcome of CSC therapy has shown superior results in experimental studies but to a lesser extent in human clinical trials[6]. The applications of SC therapy for cardiovascular regeneration still hold a plethora of queries to be answered as well as commandment of the molecular and signaling features for CSCs in order to standardize this therapy. Among the aspects that need optimization are the types of SCs and supporting cells to be used, the number of cells, the route of injection, the frequency, and best timing for transplantation. Standardization requires an advanced understanding of the full biological features of CSCs.

SC therapy in cardiac regeneration has dual beneficiary actions. Primarily, the transplanted exogenous SCs would directly differentiate into CMs. Concomitantly, SCs activate the endogenous progenitors through their rich secretome of extracellular vesicles, immunomodulatory and growth factors, protein, and nucleic acid families[7]. These paracrine factors act to activate resident SCs and enhance vascularization to potentiate cardiac repair.

This review aims to provide insight into CSCs/CPCs regarding their embryological origin, populations, niche, metabolism, secretome, and therapeutic potentials. Also discussed is the interplay of nanotechnology with SCs in several aspects, including differentiation, tracking, imaging, and assisted therapy, showing the prospects and limitations of nanoparticle (NP)-based cardiac therapy. Finally, preclinical trials and ongoing, completed, and future clinical trials using CSCs and combined therapy are shown to delineate the potential applications in treating cardiac disease.

The heart is formed of a wide range of cell types originating from the mesodermal precursor cells. They include CMs and endocardial cells forming the inner layer, while epicardial-derived cells (EPDCs) and smooth muscle cells (SMCs) are found on the external layer. Differentiation of the mesodermal cells is initiated by the T-box transcriptional factors Brachyury (Bry) and Eomes. Bry+ cells differentiate into insulin gene enhancer protein islet-1 (ISL1) and T-box transcription factor 5 (TBX5) expressing cells, while Eomes induce expression of mesoderm posterior 1 (MESP1). MESP1+ cells are identified before the first heart field (FHF) and the second heart field (SHF) separations, so MESP1 serves as an indicator of early CPCs for both heart fields[8]. Chemokine receptor type 4 (CXCR4), fetal liver kinase 1 (FLK-1), and platelet derived growth factor receptor A are other surface markers that coincide with MESP1 and are used in combination to isolate CPCs[9,10].

In addition, a novel cell surface marker known as G protein-coupled receptor lysophosphatidic acid receptor 4 is specific to CPCs and determines its functional significance. Interestingly, its transient expression peaks in cardiac progenitors after 3 to 7 d of human (h)PSCs differentiation toward cardiac lineage, then it declines. In vivo, lysophosphatidic acid receptor 4 shows high expression in the initial stages of embryonic heart development and decreases throughout development[11].

The FHF cells are the firstly differentiated myocardial cells that are derived from cells in the anterior lateral plate mesoderm; they give rise to the left ventricle, partially some of the right ventricle population, sinoatrial node, atrioventricular node, and both atria[12]. Meanwhile, the SHF cells originate from the pharyngeal mesoderm to the posterior side of the heart and further divide into anterior and posterior SHF. They contribute to the right ventricle, atria, and the cardiac outflow tract (OFT) formation. Addition of the SHF-derived CMs to the ventricles depend on myocyte enhancer factor 2C (MEF2C). It has been found that MEF2C null mice die at 9.5-d post conception with severe heart defects due to failure of heart looping[13]. In OFT formation, two waves of SHF progenitors and their derivatives have been identified, making a differential contribution to the aorta and pulmonary artery. The early wave of cells is favorably directed to the aorta, while the second wave of cells contributes to the pulmonary artery. Phosphoinositide-dependent kinase-1 critically regulates the second wave of cells, and its deletion results in pulmonary stenosis[14]. The epicardium of the heart is formed of a transient proepicardial organ. Proepicardium is formed from homeobox protein NKx2.5 (NKx2.5) and ISL1+ cells. After epicardial formation, subepicardial mesenchymal space is formed by epithelial to mesenchymal cell transformation of the epicardial cells[15] (Figure ).

Embryonic cardiac progenitors, Brachyury-positive mesoderm precursors and Pax3+ neural crest cells. Brachyury (Bry+) mesoderm precursors give rise to the mesoderm posterior 1+ primordial precursors, which are the origin of the first heart field, second heart field, and proepicardial progenitors, each population of which is responsible for the development of different parts in the heart. Pax3+ neural crest cells are responsible for the development of vascular smooth muscle, outflow tract, valves and the conductive system. Progenitors are tagged with their specific markers. Created with BioRender.com. CPC: Cardiac progenitor cell; LT: Left; RT: Right; FHF: First heart field; SHF: Second heart field; OFT: Outflow tract.

The differentiation in the posterior SHF is regulated by Hoxb1 gene. Stimulation of Hoxb1 in embryonic stem cells (ESCs) halts cardiac differentiation, while Hoxb1-deficiency shows premature cardiac differentiation in embryos. Moreover, an atrioventricular septal defect develops as a result of ectopic differentiation in the posterior SHF of embryos deficient in Hoxb1 and its paralog Hoxa1[16].

Multiple signaling pathways have essential roles in cardiogenesis with a sequential arrangement. The transforming growth factor- (TGF-) superfamily, retinoic acid, Hedgehog, Notch, Wnt, and fibroblast growth factors (FGFs) pathways comprise the chief signaling pathways involved in cardiac development. These pathways, along with transcription factors and epigenetic regulators, regulate cardiac progenitors specification, proliferation, and differentiation into the different cardiac cell lineages[17].

The TGF- superfamily members consist of over 30 structurally associated polypeptide growth factors including nodal and bone morphogenetic proteins (BMP)[18].

Nodal signaling is vital for the formation of sinoatrial node. Nodal inhibition during the cardiac mesoderm differentiation stage downregulates PITX2c, a transcription factor recognized to inhibit the formation of the sinoatrial in the left atrium during cardiac development[19]. Moreover, nodal signaling is dispensable for initiation of heart looping; however, it regulates asymmetries that result in a helical shape at the heart tube poles[20].

BMP signaling, as a member of TGF-, has an important role in the different stages of heart development including the OFT formation, endocardium, and lastly the epicardium. The cardiac neural crest cells have a crucial role in normal cardiovascular development. They give rise to the vascular smooth muscle of the pharyngeal arch arteries, OFT septation, valvulogenesis, and development of the cardiac conduction system[21] (Figure ). The role of BMP in OFT septation mainly depends on their gradient signaling, which arranges neural crest cell aggregation along the OFT; this Dullard-mediated tuning of BMP signaling ensures the fine timed zipper-like closure of the OFT by the neural crest cells[22]. Furthermore, the BMP signaling promotes the development of endocardial cells (ECs) from hPSC-derived cardiovascular progenitors[23]. It is also integrated with Notch signaling for influencing the proepicardium formation, where overexpression of Notch intracellular receptor in the endothelium enhances BMP expression and increases the number of phospho-Smad1/5+ cells for enhancing the formation of the proepicardium[24].

Retinoic acid signaling plays a role in heart development. It is a key factor for efficient lateral mesoderm differentiation into atrial-like cells in a confined time frame. The structural, electrophysiological, and metabolic maturation of CMs are significantly influenced by retinoic acid[25]. However, it is reported that retinoic acid receptor agonists transiently enhance the proliferation of human CPCs at the expense of terminal cardiac differentiation[26].

The downregulation of the retinoic acid responsive gene, ripply transcriptional repressor 3 (RIPPLY3), within the SHF progenitors by histone deacetylase 1 is required during OFT formation[27].

Hedgehog signaling has a role in OFT morphogenesis. Lipoprotein-related protein 2 (LRP2) is a member of the LDL receptor gene family, a class of multifunctional endocytic receptors that play crucial roles in embryonic development. LRP2 is expressed in the anterior SHF cardiac progenitor niche, which leads to the elongation of the OFT during separation into aorta and pulmonary trunk. Loss of LRP2 in mutant mice results in depleting a pool of sonic hedgehog-dependent progenitor cells in the anterior SHF as they migrate into the OFT myocardium due to premature differentiation into CMs. This depletion results in aberrant shortening of the OFT[28].

Four Notch receptors (Notch1Notch4) and five structurally similar Notch ligands [Delta-like (DLL) 1, DLL3, DLL4, Jagged1, and Jagged2] have been detected in mammals[29]. Activation of Notch signaling enhances CM differentiation from human PSCs. However, the CMs derived from Notch-induced cardiac mesoderm are developmentally immature[30]. In vivo, the Notch pathway plays a significant role in CPC biology. An arterial-specific Notch ligand known as DLL4 is expressed by SHF progenitors at critical time-points in SHF biology. The DLL4-mediated Notch signaling is a crucial requirement for maintaining an adequate SHF progenitor pool, in a way that DLL4 knockout results in decreased proliferation and increased apoptosis. Reduced SHF progenitor pool leads to an underdeveloped OFT and right ventricle[31].

The Wnt signaling pathway has an essential role in many developmental stages of embryogenesis. The Wnt family consists of 19 distinct Wnt proteins and other 10 types of Frizzled receptors. On the basis of their primary functions, the Wnt and Frizzled receptors are divided into two major classes, which are the canonical and non-canonical Wnt pathways[32]. Accumulating evidence suggests a role for the dynamic balance between canonical and non-canonical Wnt signaling in cardiac formation and differentiation. Wnt/-catenin signaling is required for proper mesoderm formation and proliferation of CMs but needs to be low for terminal differentiation and cardiac specification. In contrast, for cardiac specification in murine and human ESCs, non-canonical -catenin independent Wnt signaling is essential, while the non-canonical Wnt signaling is necessary for terminal differentiation later in development[33].

The activation of non-canonical Wnt is non-catenin-independent, and the downstream proteins involve several kinases, including protein kinase C, calcium/ calmodulin-dependent kinase, and Jun N terminal kinase (JNK). Wnt11 enhances angiogenesis and improves cardiac function through non-canonical Wnt-protein kinase C-Jun N terminal kinase dependent pathways in myocardial infarction (MI)[34]. In hypoxia, Wnt11 expression preserves the integrity of mitochondrial membrane and facilitates the release of insulin growth factor-1 (IGF-1) and vascular endothelial growth factor (VEGF), thus protecting CMs against hypoxia[35]. Canonical dependent Wnt signaling, Wnt 3 Ligand, favors the pacemaker lineage, while its suppression promotes the chamber CM lineage[36].

The regenerative capacity of most organs is contingent on the adult SC populations that exist in their niches and are activated by injury. Adult SC populations vary greatly in their molecular marker expression profile and hence in their possible role in regenerative medicine. The transcriptome is a representation of the gene read-outs, the cellular state, and is imperative for studying all genetic disease and biological processes. The genome-wide profiling using novel sequencing technology has made transcriptome research accessible.

Receptor tyrosine kinase (RTK) c-KIT (also referred to as SC factor receptor or CD117)-expressing CPCs are mainly located in the atria and the ventricular apex, comprising most of the ventricular and atrial myocardium[37]. c-KIT+ cells also express the cardiac transcription factors NKx2.5, GATA binding protein 4 (GATA4), and MEF2C but are negative for the hematopoietic markers CD45, CD3, CD34, CD19, CD16, CD20, CD14, and CD56[38,39]. SC factor ligand attaches to the c-KIT receptor and activates the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) and p38 mitogen-activated protein kinase (MAPK) signaling pathways[40]. Both PI3K/AKT and MAPK pathways control various CPCs functions like self-renewal, proliferation, migration, and survival[41]. During embryonic development and the early post-natal time, c-KIT+ CPCs contribute to the generation of new CMs. Such capacity declines in the adult heart with only a few new CMs originating from CPCs[42]. In a rat MI model, the c-KIT+ CPCs have migrated through the collagen type I and type III matrices into the infarcted area. The transplanted CPCs have shown overexpressed matrix metalloproteinases (MMPs; MMP2, MMP9, and MMP14) that degrade extracellular matrix (ECM), concluding that c-KIT+ CPCs hold an invasive capacity[43]. Transplanted CPCs (c-KIT+ CPCs and cardiospheres) also show an endogenous proliferative potential in vivo and additionally activate endogenous CPCs[44].

Stem cell antigen 1 (SCA-1) expressing CPC population exists predominantly in the atrium, intra-atrial septum, and atrium-ventricular boundary and dispersed inside the epicardial layer of adult hearts[45]. SCA-1 is a cell surface protein of the lymphocyte antigen-6 (Ly6) gene family, which has roles in cell survival, proliferation, and differentiation[46]. A population of SCA-1+ cells from murine adult myocardium hold a telomerase activity comparable to that of a neonatal heart. This SCA-1+ population is different from hematopoietic SCs as they lack CD45, CD34, c-KIT, LIM domain only 2, GATA2, VEGF receptor 1, and T-cell acute lymphoblastic leukemia 1/SC leukemia proteins. SCA-1+ cells are also distinct from endothelial progenitor cells and express cardiac lineage transcriptional factors such as GATA4, MEF2C, and translation elongation factor 1 yet lack transcripts for cardiomyocytic structural genes such as BMP1r1 and -, -MHC[47,48]. Although this population exhibits the endothelial marker CD31, it is suggested to be due to the contaminating endothelial CD31+/SCA-1+ cells. In vitro studies have revealed that 5-azacytidine (5-aza), a demethylating agent, pushed SCA-1+ cells to differentiate into CMs[48,49]. Further studies have isolated SCA-1+ cells that lack CD31 and CD45 markers, referring to them as lineage negative (Lin). The SCA-1+/Lin cells display a mesenchymal cell-surface profile (CD34, CD29+, CD90+, CD105+, and CD44+) and are able to differentiate, to a certain extent, into CMs and endothelial and smooth muscle-like cells[50,51].

Human SCA-1+-like cells also express early cardiac transcription factors (GATA4, MEF2C, insulin gene enhancer protein ISL-1, and Nkx-2.5) and can differentiate into contractile CMs[52]. Although a human ortholog of the SCA-1 protein has not been yet identified, an anti-mouse SCA-1 antibody is used to isolate SCA-1+-like cells from the adult human heart.

MESP1 expressing cells mainly contribute to the mesoderm and to the myocardium of the heart tube during development[53]. Transient expression of MESP1 seems to accelerate and enhance the appearance of cardiac progenitor. However, homologous disruption of the MESP1 gene has resulted in aberrant cardiac morphogenesis. MESP1 interacts with the promoter area of main cardiac transcription factors, including heart and neural crest derivatives expressed 2, Nkx2-5, myocardin, and GATA4[54]. These factors induce fibroblasts to express a full battery of cardiac genes, form sarcomeres, develop CM-like electrical activity, and in a few cases elicit beating activity[55]. Several studies have shown that the addition of MESP1 could enhance the efficacy of direct reprogramming of fibroblasts into CMs[56,57]. The transdifferentiation of fibroblasts to CMs via MESP1 suggests that MESP1 chiefly modulates the gene regulatory network for cardiogenesis[52].

Kinase insert domain receptor (KDR), also known as Flk-1, is one of the earliest discovered cardiogenic progenitor cell markers acting during the early stages of cardiac development in human[58]. Nelson et al[59] have reported that Flk-1 has a distinctive transcriptome that has been evident at day 6, immediately after gastrulation but prior to the expression of the cardiac transcription factors. KDR+ population lack the pluripotent octamer-binding transcription factor 4, sex determining region Y-Box transcription factor (SOX) 2, and endoderm SOX17 markers. On the other hand, KDR+ CPCs have shown a noteworthy upregulation in SOX7, a vasculogenic transcription factor, overlapping with the emergence of primordial cardiac transcription factors GATA4, myocardin, and NKx2.5. Moreover, KDR subpopulations that overexpress SOX7 are associated with a vascular phenotype rather than a cardiogenic phenotype. These outcomes offer insights for refining the therapeutic regenerative interventions.

The FHF cells express hyperpolarization activated cyclic nucleotide gated potassium channel 4 and TBX5, while SHF progenitors express TBX1, FGF 8, FGF10, and sine oculis homeobox2 (Figure ). Cells from the SHF exhibit high proliferative and migratory capacities and are mostly responsible for the elongation and winding of the heart tube. Moreover, SHF cells differentiate to CMs, SMCs, fibroblasts, and endothelial cells (ECs) along their journey in the heart tube to form the right ventricle, right ventricular OFT, and most of the atria[60,61]. However, FHF cells hold less proliferative and migratory potentials and differentiate predominantly to CMs that form the left ventricle and small parts of the atria[62]. The cells of the cardiac crescent, theoretically the progeny of FHF CPCs, are terminally differentiated cells expressing the markers of CMs, such as actin alpha cardiac muscle 1 and myosin light chain 7[63,64], hence they are unlikely to be multipotent progenitors. Therefore, it is difficult to identify FHF before Nkx2.5 and TBX5 expressions. Conversely, multipotent SHF CPCs were validated with a clonal tracing experiment and identified by ISL1 expression[65]. However, ISL1 expression is not specific for SHF and has been proposed to represent only the developmental stages[66]. Tampakakis et al[67] generated ESCs by using hyperpolarization activated cyclic nucleotide gated potassium channel 4-green fluorescent protein and TBX1-Cre; Rosa-red fluorescent protein reporters of the FHF and the SHF respectively, and also by using live immunostaining of the cell membrane CXCR4, a SHF marker and the reporters. The ESC-derived progenitor cells have shown functional properties and transcriptome similar to their in vivo equivalents. Thus, chamber-specific cardiac cells have been generated for modelling of heart diseases in vitro.

The EPDCs are important as a signaling source for heart development, cardiac regeneration, and post-MI heart repair. Throughout the development of the heart in mice, EPDCs aid in the formation of various cardiac cell types and secrete paracrine factors for myocardial maturation[68]. In the adult heart, EPDCs are normally dormant and become stimulated following myocardial injury. Transcriptional analysis of the EPDCs derived from human (h)iPSCs cells have revealed several markers of EPDCs including Wilms tumor protein 1, endoglin, thymus cell antigen 1, and aldehyde dehydrogenase 1 family member A2[69] (Figure ). Following MI in mice, EPDCs undergo an epithelial-to-mesenchymal transition, with overexpression of Wilms tumor protein 1, and differentiate mainly into SMCs/fibroblasts[70,71]. EPDC-secreted paracrine factors include VEGF-A, FGF2, and PDGF-C, which support the growth of blood vessels, protect the myocardium, and recover cardiac functions in an acute MI-mouse model[70].

Side population (SP) cells have been detected in the heart and other various tissues and hold enhanced stem and progenitor cell activity[72]. SP cells, when stained in vitro, hold the ability to flush out the DNA Hoechst dye from their nuclei[73]. Gene expression profiling of SP cells after MI has revealed a downregulation of Wnt-related signals coupled with increased SP cell proliferation. This has been validated in vitro by treatment of isolated SP cells with canonical Wnt agonists or recombinant Wnt, where the proliferation of SP cells has been repressed with partial arresting the G1 cell cycle phase[74]. Consistent with this observation, delivery of secreted Frizzled-related proteins (SFRP; the Wnt antagonizer) improves post-MI remodeling[75,76].

SP cells can be identified by surface marker adenosine triphosphate (ATP) binding cassette subfamily G member 2 (ABCG2), also referred to as the breast cancer resistance protein1[77]. ABCG2+ cells have been also observed in the adult heart and can differentiate in vitro into CMs[78]. When SP cells have been injected into the injured hearts of rats, they have been recruited to the injured regions, where they differentiate into CMs, ECs, and SMCs, suggesting that they may be endogenous SP cells[79]. However, ABCG2CreER based genetic lineage tracing has demonstrated that ABCG2+ cells could only differentiate into the multiple cardiac cell lineages during the embryonic stages but not in adulthood[80,81]. The combination of ABCG2+ cells with pre-existing CMs is more likely to stimulate CM proliferation rather than differentiation into CMs directly[82]. Therefore, genetic fate mapping investigations have disproved the SP cells property of the adult endogenous ABCG2+ SP and their in vivo renewing myogenic ability[83].

Cardiospheres contain a combination of stromal, mesenchymal, and progenitor cells that are isolated from cultures of human heart biopsy[39,84]. They represent a niche-like environment, with cardiac-committed cells in the center and supporting cells in the periphery of the spherical cluster[85]. The cardiosphere-derived cells (CDCs) were originally isolated from mouse heart explants and human ventricular biopsies based on their ability to form three-dimensional (3D) spheroids in suspension cultures[86]. CDCs have grabbed much attention due to their proliferation and differentiation abilities by inherent stimulation of cardio-specific differentiation factors [GATA4, MEF2C, Nkx2.5, heart and neural crest derivatives expressed 2, and cardiac troponin T (TNNT2)] using a clustered regularly interspaced short palindromic repeat/dead Cas9 (CRISPR/dCas9) assisted transcriptional enhancement system[87,88]. Sano et al[89] have postulated that the CRISPR/dCas9 system may provide a proficient method of modifying TNNT2 gene activation in SCs. Consequently, CRISPR/dCas9 can improve the therapeutic outcomes of patients with ischemic heart disease by enhancing the transplanted CDCs differentiation capacity within the ischemic myocardium. Heart tissue is usually obtained by endomyocardial biopsy or during open cardiac surgery and grown in explants to form CDCs. CDCs have shown a superior myogenic differentiation potential, angiogenesis, and paracrine factor secretion as compared to other cell types. In heart failure animal models, the injected CDCs potentially differentiated into CMs and vascular cells. Additionally, CDCs have diminished unfavorable remodeling and infarct size, and hence improve cardiac function[90]. Accordingly, cardiospheres and CDCs may be some of the most promising sources of CPCs for cardiac repair.

The niche in the heart integrates several heterogeneous cell types, including CSCs, progenitors, fibroblasts, SMCs, CMs, capillaries, and supporting telocytes (TCs)[91], together with the junctions and cementing ECM that hold the niche together. Such architectural arrangement is essential for protection against external damaging stimuli and for preserving the stemness of the CSCs (Figure ). Without the niche microenvironment, CSCs lose their stemness and initiate differentiation eventually, leading to the exhaustion of the CSC pool. Similarly, in vitro studies require feeder layers and cytokines supplements in the culture media to ensure that SCs remain in their undifferentiated state[37].

Invivo arrangement of the central cardiac stem cells and the surrounding cells that comprise the niche (right side) and the in vitro derived cardio spheres (left side). The key delineates the types of cells identified in the niche and cardio spheres. Created with BioRender. CSC: Cardiac stem cell.

In vitro studies have recapitulated the niche theory using cardiospheres, which are 20150 m spheres (Figure ) of cells generated from the explant outgrowth of heart tissues[92,93]. Cardiospheres consist of CSCs in the core and cells committed to the cardiac lineage such as myofibroblasts, while vascular SMCs and ECs form the outer layer of the spheres. The 3D structure of cardiospheres protects the interiorly located CSCs from oxidative stress as well as maintain their stemness and function[84].

Accurate anatomical identification of CSCs in vivo remains a challenge due to the lack of basal-apical anatomical orientation as seen in epithelial organs such as the intestines[94]. Moreover, the heart does not comprise a specific compartment, where cells form a well-defined lining as seen in the bone marrow osteoblasts[95]. The adult heart epicardial lining anatomically contains several classes of niches, which are not limited to the sub epicardium[96] but dispersed throughout the myocardium, more in the atria and apex away from hemodynamic stress[97]. Some niches have been described in the atrio-ventricular junction of adult mouse and rat hearts[98] and interestingly in the human hearts[99]. The young mouse heart has been studied morphometrically to identify the location of CSCs niche and has been defined as a randomly positioned ellipsoid structure consisting of cellular and extracellular components. Within the niches, undifferentiated CSCs are usually assembled together with early committed cells that express c-KIT on surface, Nkx2.5 in the nucleus, and the contractile protein -sarcomeric actin in the cytoplasmic[97].

CSCs niche consists of clusters of c-kit+, MDR1+, and Sca-1+ cells[98] but lack the expression of the transcription factors and cytoplasmic or membrane proteins of cardiac cells[99,100]. Cardiac c-kit+/CD45- cells comprise about 1% of the CSC niche[97], are self-renewing clonogenic, and possess a cardiac multilineage differentiation potential comprise[101].

Within the niche, gap junctions (connexins) and (cadherins) connect SCs to their supporting cells, myocytes/fibroblasts. Conversely, ECs and SMCs do not act as supporting cells. Hence, the communication between CSCs with CMs and fibroblasts has been investigated by using in vitro assays[102]. The transmission of dyes via gap junctions between CSCs and CMs or fibroblasts was demonstrated previously and verified the functional coupling of these three cell populations[97]. In addition, micro ribonucleic acid (miRNA-499) translocates from CMs to CSCs comprising to the initiation of lineage specification and formation of myocytes[103].

Identification of SC niches is contingent upon the fulfillment of explicit criteria, including the recognition and determination of the affixing of SCs to their supporting cells as well as assuring the existence of an ancestor-progeny association[104]. Chemical and physical signals modulate the behavior of SCs within the niche. Amongst these signals are cytokines, cell surface adhesion molecules, shear forces, oxygen tension, innervation, and ions that serve as major determinants of SCs function[97]. Cell-to-cell signaling mediates the fate of SCs within the niches to promote self-renewal and favors their migration and differentiation. The fine-tuned crosstalk between SCs and their supporting cells regulates the state of the niche regarding quiescence or activity[105].

CSC niches, similar to the bone marrow, characteristically live in low oxygen tension, which favors a quiescent primitive state for SCs[106]. The longstanding perpetuation of the CSC niche requires a hypoxic environment, while physiological normoxia could be required for active cardiomyogenesis[107]. Hypoxic c-KIT+ CSCs within niches have been found throughout the myocardium, especially at the atria and apex. Throughout all ages, bundles of CSCs with low oxygen content coexist with normoxic CSCs niches. Hypoxic CSCs, especially in the atria, are quiescent cells undergoing cell cycle arrest and cannot divide. Normoxic CSCs are pushed into intense proliferation and differentiation with continuous telomere erosion, resulting finally in dysfunctional aged CMs[108]. Additionally, Nkx2.5 and GATA4 expressions are only restricted to the normoxic CSC niche. A balance between the hypoxic and normoxic niche is essential for the preservation of the CSC compartment and for the maintenance of myocardial homeostasis during the organ lifespan. Some factors such as aging cause an imbalance by expanding the hypoxic quiescent CSCs so that less pools of cycling CSCs maintain cell turnover[100]. Hypoxic cardiac niches are abundant in the epicardium and subepicardium in an adult mouse heart, which also fosters a metabolically distinctive population of glycolytic progenitor cells[109].

The pool of CSCs seems to be heterogeneous, incorporating quiescent and actively proliferating cells, migratory and adherent cells, uncommitted and early committed cells, with young and senescent cells. Additional surface epitopes remain to be disclosed to classify pools of CSCs holding specific properties. Surface Notch1 expression distinguishes multipotent CSCs that are poised for lineage commitment, while c-Met and ephrin type-A receptor 2 receptors reveal cells with particular migratory potential out of the niche area. A specific compartment of CSCs, expressing IGF-1 receptor, can be stimulated to regenerate damaged myocardium, while those expressing IGF-2 receptor hold higher probability for senescence and apoptosis. Although this arrangement of cells seems to equip properly the CSC with homeostasis regulation, it does not effectively protect against aging or ischemic injury of the heart[100].

Circulatory angiogenic cells (CACs) are endothelial progenitor cells involved in vasculogenesis, angiogenesis, and stimulating myocardial repair, mainly through paracrine action. Latham et al[110] demonstrated that conditioned medium from CACCSC co-cultures exhibited greatly mobilized CACs, with induction of tubule formation in human umbilical vein endothelial cells, mainly through the upregulation of the angiogenic factors angiogenin, stromal cell-derived factor 1 (SDF-1), and VEGF. Moreover, administration of CACs and CSCs in infarcted hearts of non-obese/severe combined immunodeficient mice restored substantially the left ventricular ejection fraction (LVEF), with reduction of scar formation as revealed by echocardiography. Successful yet modest SMCs, ECs, and CM differentiation has been also reported.

Pericytes (also called Rouget cells, mural cells, or perivascular mesenchymal precursor cells) are mesodermal cells that border the endothelial lining. They are highly proliferative cells and express neural/glial antigen 2, SOX-2, PDGFR-, CD34, and several mesenchymal markers such as CD105, CD90, and CD44. It was previously reported that the transplantation of saphenous vein-derived pericytes (SVPs) into an ischemic limb of an immunodeficient mice restored the local circulatory network via angiogenesis[111]. Moreover, treatment with SVP reduced fibrotic scar, CM death, and vascular permeability in a mouse model of MI via miRNA-132 facilitated angiogenesis[112]. Avolio et al[113] were the first to describe the relationship between SVP and the endogenous CSCs. Combined CSC and SVP transplantation in the infarcted myocardium of severe combined immunodeficient/Beige-immunodeficient mice showed similar results to treatment with CSCs or SVP cells per se, regarding scar size and ventricular function, indicating that SVPs alone are as potent as CSCs.

TCs represent a recently described cell population in the stromal spaces located in many organs, including the heart. They are broadly dispersed throughout the heart and comprise a network in the three cardiac layers, heart valves, and in CSC niches. TCs have been documented also in primary culture from heart tissues[114,115]. The ratio of cardiac TCs (0.5%-1%) exceeds that of CSCs. Although they still represent a minute portion of human cardiac interstitial cells, their extremely long and extensive telopodes allow them to occupy more surface area, forming a 3D platform probably that extends to support other cells[116]. The telopodes act as tracks for the sliding of precursor cells towards mature CMs and their integration into heart architecture[91]. TCs form a tandem with CSCs/CPCs in niches, where they communicate through direct physical contact by atypical junctions or indirect paracrine signaling[115].

TC-CSC co-culturing have suggested that TCs and CSCs act synergistically to control the level of secreted proteins, as shown by the increased levels of monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein1 and 2 (MIP-1 and MIP-2), and interleukin (IL)-13. Whereas, the level of IL-2 decreased compared to the monoculture of CSCs or TCs. IL-6 found in TC culture is behind the upregulation of these chemokines. Chemokines elucidated the role of TCs in directing the formation of CMs. Within the context, MIP-1 and MCP-1 play roles in the formation of SMCs in the airway. Additionally, MCP-1 is also involved in mouse skeletal muscle regeneration by recruiting macrophages. The enhancement of MCP-1 secretion serves as an activator of another cell population, primarily macrophages, which are generally involved in such processes[117].

IL-6 also activates downstream signaling pathways and contributes to cardioprotection and vessel formation in the heart through activation of gp130/signal transducer and activator of transcription 3. The Gp130/signal transducer and activator of transcription 3 is essential for the commitment of cardiac SCA-1+ cells into endothelial lineage[118].

Furthermore, IL-6 targets VEGF and hepatocyte growth factor (HGF) genes. VEGF has a mitogenic effect on CMs[119]. It is known to mobilize bone marrow-derived mesenchymal stem cells (BM-MSCs) into the peripheral blood in MI patients[120]. HGF and its receptor (c-Met) are also involved in cardiogenesis, as it is expressed early during cardiac development[121]. The level of HGF mRNA is normally low in the heart, but it is upregulated for at least 14 d after ischemic insult in rats, enhancing CMs survival under ischemic conditions[122,123]. Moreover, it has the potential to generate an adhesive micro-environment for SCs, as demonstrated in a study of transplantation of HGF transfected BM-MSCs in the infarcted myocardium[124]. HGF is also a powerful angiogenic agent, conducting its mitogenic and morphogenic effects through the expression of its specific receptor in various types of cells, including myocytes. Moreover, HGF exerts antifibrotic and antiapoptotic effects on the myocardium[125,126].

Transcriptomic analysis also has disclosed that TCs express pro-angiogenic miRNAs including let-7e, miRNA-21, miRNA-27b, miRNA-126, miRNA-130, miRNA-143, miRNA-503, and miRNA-100[127]. The TCs and CSCs interact in vitro forming atypical junctions, such as puncta adherentia and stromal synapses. The puncta adherentia consists of cadherincatenin clusters. It controls the symmetry of division by facilitating the proper positioning of centrosomes. Therefore, an increased number of CSCs has been reported to be encountered in the presence of cardiac TCs[128,129].

The paracrine potential of CSCs/CPCs has been recently under focus. CSC-derived cytokines and growth factors include epidermal growth factor (EGF), HGF, IGF-1, IGF-2, IL-6, IL-1, and TGF-1[130,131]. Exosomes appear to harbor relevant reparative signals, which mechanistically underlie the beneficial effects of CSCs transplantation[132].

Structurally, exosomes are lipid bilayer nano-sized organelles, 20-150 nm in diameter, secreted from all cell types, and function as intercellular communicators. Exosomes are highly heterogenic in content, and this stems from the unique packaging process that occurs inside progenitor and SCs. Exosomes carry lipids, proteins, and nucleic acids, with an abundance of miRNAs that hold profound post-transcriptional gene regulatory effects[133].

Amongst the distinctive protein content of cardiac exosomes are the chaperone proteins heat shock protein (HSP) 70 and HSP60. The HSP70 and HSP60, which under normal conditions assist in protein folding processes and deter misfolding and protein aggregation under pathological states induced by stress, also play major roles in apoptosis[134]. Circulating exosomes from healthy individuals have been found to activate cardioprotective pathways in CMs via HSP70 through extracellular signal-regulated kinase and HSP27 phosphorylation[135].

The exosome protein cargo of CPCs is distinct from BM-MSCs, fibroblasts, and other sources as it contains ample amounts of the pregnancy-associated plasma protein-A (PAPP-A). PAPP-A is present on the surface of human exosomes and interacts with IGF binding proteins (IGFBPs) to release IGF-1[136]. The cardioprotective role of CPCs-exosomes has been proven experimentally in in vitro ischemia/reperfusion and MI models and on CMs apoptosis to surpass that of BM-MSC-exosomes owing to their rich content of PAPP-A[137].

Like all exosomes, mouse CPCs-derived exosomes are positive for the surface markers CD63, CD81, and CD9, TSG-101, and Alix, however, they express a high-level of GATA4-responsive-miRNA-451. MiRNA-451 has been shown to inhibit CM apoptosis in an acute mouse myocardial ischemia-reperfusion model through inhibition of the caspases 3/7. The expression of miRNA-21 in the mouse CPCs-exosomes additionally justifies their CM protection against oxidative stress and antiapoptotic effects via inhibition of programmed cell death protein 4 (PDCD4)[138]. Human CPCs-exosomes are enriched with miRNA-210, miRNA-132, and miRNA-146a-3p, which account for the diminished CM apoptosis, enhanced angiogenesis, and improved LVEF[139]. MiRNA-146a-5p is the most highly upregulated miRNA in human CPCs-exosomes and targets genes involved in inflammatory and cell death pathways[137].

The CDCs contain CD34+ stromal cells of cardiac origin and are multipotent and clonogenic but not self-renewing[140]. CDCs secrete exosomes that induce cardiomyogenesis and angiogenesis, regulate the immune response, downgrade fibrosis, and improve the overall cardiac function[141,142]. Moreover, CDCs homogeneously express CD105 but not CD45 or other hematopoietic markers. They also exhibit a high expression of miRNA-126[143]. Circulating miRNA-126 may participate in cardiac repair during acute MI and has been demonstrated to be downregulated in heart damage[144].

While exosomes are constitutively secreted, changes in the surrounding microenvironment, such as hypoxia, can induce modifications in CPCs- and CM- derived extracellular vesicles. Hypoxic CMs secrete large extracellular vesicles containing long noncoding RNA neat 1 (LNCRNA NEAT1), which is transcriptionally regulated under basal conditions by p53, while during hypoxia it is regulated by the hypoxia inducible factor 2A. An uptake of the hypoxic CM-derived extracellular vesicles by fibroblasts can prompt the expression of profibrotic genes[145]. Oxidative stress may also induce the release of cardiac CPCs exosomes, which in turn inhibit apoptosis when taken up by H9C2 (rat cardiomyoblast cell line)[132]. Furthermore, oxidative stress stimulates secretion of miRNA-21 rich exosomes, which could inhibit H9C2 apoptosis by targeting PDCD4 and hence can be accounted as a new method to treat ischemia-reperfusion[138].

Intercellular communication via exosomes occurs as part of various biological processes, including immune modulation, vasculogenesis, transport of genetic materials, and pathological conditions such as inflammation, apoptosis, and fibrosis, which can lead to cardiovascular disease when altered[146]. Hence, isolation and analysis of cardiac exosomes contents, mainly miRNA and proteins, could offer diagnostic information for several cardiovascular diseases[147] (Figure ).

Schematic diagram elucidating the diverse exosomal contents that serve as biomarkers for several cardiovascular diseases. Created with BioRender.com. HSP: Heat shock protein; lncRNA: Long non-coding RNA; miR: MicroRNA.

Functionally, exosomes mediate several intra-cardiac inter-cellular communications such as:

CPC-CM crosstalk through factors, such as miRNA-146a and PAPP-A, which activate extracellular signal-regulated kinases 1/2 pathway and inhibit apoptosis[139].

CPC-macrophage (M1) crosstalk via miRNA-181b and Y-RNA fragment transforms M1 to M2 macrophages with attenuated proinflammatory cytokines and increased IL-10[148,149] (Figure ).

Possible cardiac reparative effects of cardiac stem cell/cardiosphere-derived cell-derived exosomes in myocardial ischemia and ischemia/reperfusion injury. Created with BioRender.com. CSC: Cardiac stem cell; IL: Interleukin; IR: Ischemia/reperfusion; miRNA: MicroRNA; PI3K: Phosphoinositide 3-kinase; SDF-1: Stromal cell-derived factor 1; VEGF: Vascular endothelial growth factor.

CPC-fibroblast interaction via exosomes primes the fibroblasts and increases expression of VEGF and SDF-1. Experimental injection of fibroblasts primed with CPCs-exosomes into the myocardium of a MI model proved to reduce infarct size and improve cardiac function. In addition, cardiosphere-isolated exosomes have been used to prime inert fibroblasts, leading to an intensification of their angiogenic, cardiomyogenic, antifibrotic, and collective regenerative effects[150] (Figure ).

CPC-self regulatory mechanisms: Exosomes derived from CPCs may play critical roles in maintaining the self-renewal state of CPCs themselves and balance their differentiation, i.e. preserve their stemness[151] (Figure ). The CPC-derived exosomes activate the endogenous CPCs by transferring signal molecules directly within their niche[152].

CPC-derived exosomes release various RNA species in the extracellular space, modulating endogenous SC plasticity and tissue regeneration through their cytoprotective, immunomodulatory, pro-angiogenic, and anti-apoptotic actions[153].

Fibroblasts and pericytes interact after transdifferentiating to myofibroblasts and deposit ECM causing cardiac fibrosis. These fibrotic changes are usually induced by cardiac damage and lead to scar formation. Exosomes serve as messengers for cell-to-cell communication during cardiac fibrosis[154]. Molecular mechanisms of cardiac fibrosis are primarily related to TGF- pathways, IL-11 signaling pathway, nuclear factor- pathway, and Wnt pathways[155]. Accordingly, the bioactive substances targeted at these pathways could hypothetically be applied in the treatment of cardiac fibrosis. Wnt3a, being highly expressed in exosomes, could activate the Wnt/-catenin pathway in cardiac fibroblasts by restricting GSK3 activation[156]. Moreover, tumor necrosis factor contained in exosomes can be transferred between cardiac myocytes. In general activation/inhibition of the exosomes conveying remodeling substance secretion or uptake can control the myocardial remodeling and repair following MI[154,157].

The highlighted complex cell-to-cell communication from endogenous or exogenous CSCs provides an optimal microenvironment for resident CPC proliferation and differentiation (Figure ), rendering the environment receptive to transplanted CPCs. This adaptation is promoted through activation of pro-survival kinases, leading to the induction of a glycolytic switch in recipient CPCs[158].

Data from experimental models suggest that the exosomal component of the CPC secretome can fully recapitulate the effects of cellular therapy on ischemic and non-ischemic heart models[140]. In an ischemia-reperfusion injury rat model, Ciullo and partners[159] have shown that the systemic injection of exosomes (genetically manipulated to overexpress CXCR4ExoCXCR4) improve cardiac function. Additionally, expression of hypoxia-inducible factor 1 (HIF-1) in the infarcted myocardium is upregulated through the stimulation of SDF-1. The latter is one of the CXC chemokine family overexpressed in heart post-MI that readily attaches to the CXCR4 receptor and acts as a potent chemoattractant for CXCR4 expressing circulating progenitor cells. The ExoCXCR4 are more bioactive in the infarcted zone than naturally occurring exosomes injected via tail-vein, confirming their superior homing and cardioprotective properties in the damaged heart.

Gallet et al[160] postulated the safety and efficiency of CDC-derived exosomes in acute and chronic myocardial injury animal models. Within the context of experimental research to validate the paracrine hypothesis for CDCsderived exosomes, it has been proven that human CDC-exosomes can recapitulate CDC therapy and boost cardiac function post-MI in pig models. Intramyocardial injection of human CDC-exosomes has resulted in higher exosome retention and efficacy as compared to intracoronary injection, with great reduction of scar size and increased ejection fraction. This indicates that the route of administration is imperative for full functional capacity of the exosomes. Subsequently, the researchers have devised a randomized preclinical study by means of a NOGA-guided intramyocardial exosome injection. Decreased collagen content in the infarct and border zone and increased neovascularization and Ki67+ CMs are indicative of the reparative functions of CDC-exosomes. Notably, human CDC-exosomes have shown a lack of an immune reaction, as seen by the lack of inflammatory reactions or CM necrosis in pig models. These observations strongly support the view that CDC-exosomes are ready to be tested in clinical trials.

Similar promising outcomes were observed in a Duchenne muscular dystrophy model (mdx), in which intramyocardial injection of CDC-exosomes efficiently recapitulated the effects of CDC injection on cardiac function, leading to recovery of movement. Administration of CPC-derived exosomes has resulted in transient restoration of partial expression of full-length dystrophin in mdx mice[161]. Further studies assessed the therapeutic potential of CPC-exosomes in a doxorubicin cardiotoxicity model and non-ischemic heart disease[162]. In addition, two concluded phase I clinical trials in patients with heart failure and revealed the capacity of CDCs to enhance cardiac function by reducing ventricular remodeling and scar formation. Despite receiving a single injection at the beginning of the study, the improvement in cardiac function was noted after the 1-year follow-up. This finding consequently leads to the proposition that transplanted CDCs mainly have imposed their actions at the site of injury by secreting paracrine factors including exosomes. In other words, CDC-exosomes achieved a biphasic beneficiary regenerative effect involving acute cardio protection coupled with long-term stimulation of endogenous cardiac repair[163].

While the fetal heart obtains most of its ATP supply via glycolysis[164], the adult heart relies mainly on fatty acid oxidation to fulfill the contracting myocardium high energy demand[164,165]. The loss of the regenerative phenotype is related to the oxidative metabolism of glucose and fatty acids[166,167] and is mediated by various physiological changes including increased workload and the demand for growth, which cannot be solely met by glycolysis[168,169], as well as postnatal increase in both circulating levels of free fatty acids and blood oxygen levels[164,165]. Studies have shown the involvement of the HIF-1 signaling pathway[170], peroxisome proliferator-activated receptor (PPAR)[171], and peroxisome proliferator-activated receptor coactivator-1 (PGC-1) in the switch toward oxidative metabolism[172], which is accompanied by dramatic increase in the number of mitochondria in CMs[173].

Notably, similar metabolic reprogramming occurs during differentiation from cardiac SCs to CMs[167]. Studies reported that after differentiation into CMs, there is an increase in the mitochondrial number and activity[174], increased oxidative metabolism[175], and increased respiratory capacity resulting in an increased adenosine diphosphate:ATP ratio[173] after differentiation into CMs.

The fact of the various metabolic changes that accompany the transition from glycolysis to fatty acids oxidation affect cardiac cell maturation[164,167] has mandated the consideration of substrate composition in cardiac differentiation protocols[167].

A study by Malandraki-Miller et al[176] investigated the effect of fatty acid supplementation, which mimics the metabolic switch from glucose to fatty acid oxidation, on adult cardiac progenitors. The study used radiolabeled substrate consumption for metabolic flux to investigate the role of the PPAR/PGC-1 axis during metabolic maturation. Oleic acid stimulated the PPAR pathway, enhanced the maturation of the cardiac progenitor, and increased the expression of MHC and connexin after differentiation. Moreover, total glycolytic metabolism, mitochondrial membrane potential, the expression of glucose, and fatty acid transporter increased. The recorded results contributed greatly in highlighting the role of fatty acids and PPAR in CPC differentiation.

Another study by Correia et al[177] has linked substrate utilization and functional maturation of CMs via studying the effect of the metabolic shift from glucose to galactose and fatty acid-containing medium in the maturation of hPSCs-derived CMs (hPSCs-CMs). The shift accelerated hPSC-CM maturation into adult-like CMs with higher oxidative metabolism, mature transcriptional signatures, higher myofibril density, improved calcium influx, and enhanced contractility. Galactose improved total oxidative capacity with reduction of fatty acid oxidation, thereby protecting the cells from lipotoxicity.

In CDCs, oxidative metabolism and cell differentiation reciprocally affect each other. In vitro cultures for CDCs revealed a PPAR agonist that triggers fatty acid oxidation. Metabolic changes have been characterized as the CDC differentiated towards a cardiac phenotype. Addition of a PPAR agonist at the onset of differentiation has induced a switch towards oxidative metabolism, as shown by changes in gene expression with decreasing glycolytic flux and increasing oxidation of glucose and palmitate. Undifferentiated CDCs have generated high levels of ATP from glycolysis and from oxidation of acetoacetate. Upon differentiation, oxidative metabolism of glucose and fatty acids is upregulated with decreased oxidation of acetoacetate, a metabolic phenotype similar to that of the adult heart[178].

Taken together, the metabolic hallmarks of differentiated CMs vary from their undifferentiated SCs. Energy substrate metabolism during cardiac development and differentiation shows gradual decrease in the contribution of glycolysis to ATP synthesis with simultaneous increase in fatty aciddependent mitochondrial respiration[179].

Common methods for the investigation of substrate metabolism include the measurement of metabolic fluxes using radio-labeled substrates, such as D-U-14C-glucose[180,181] as well as measurement of mitochondrial oxygen consumption rate and extracellular acidification rate using the XF Extracellular Flux Analyzer (Seahorse Bioscience, North Billerica, MA, United States)[182,183].

Recently, a detailed protocol for metabolic characterization of hiPSCs-CMs has been developed. The hiPSCs are obtained from adult somatic cells via novel cell reprogramming approaches, followed by differentiation to CMs. The novel in vitro cardiac cellular model provided new insights into studying cardiac disease mechanisms and therapeutic potentials. The characterization protocol measures small metabolites and combines gas- and liquid-chromatography-mass spectrometry metabolic profiling, lactate/pyruvate, and glucose uptake assays as important tools[184]. Integration between the implemented assays has provided complementary metabolic characteristics besides the already established electrophysiological and imaging techniques, such as monitoring ion channel activities[185], measurement of action potentials, changes in Ca+2 fluxes[186], and mitochondria viability and apoptosis[187].

An alternative pathway for glucose metabolism in CMs involves the entry of glucose-6-phosphate (G6P) in the pentose phosphate pathway, with resultant generation of reduced nicotinamide adenine dinucleotide phosphate (NADPH)[188]. Reduced NADPH helps to regenerate reduced glutathione and thus acts protectively against reactive oxygen species induced cell injury.

The cardioprotective role of the pentose/G6P/NADPH/glutathione pathway has been emphasized by Jain et al[189] who demonstrated that G6P dehydrogenase (G6PD) lacking mice have more severe heart damage induced by the myocardial ischemia reperfusion injury in Langendorff-perfused hearts as compared with wild-type mice.

Read more:
Cardiac stem cells: Current knowledge and future prospects

Cardiovascular diseases represent the world's leading cause of death. In this heterogeneous group of diseases, ischemic cardiomyopathies are the most devastating and prevalent, estimated to cause 17.9 million deaths per year. Despite all biomedical efforts, there are no effective treatments that can replace the myocytes lost during an ischemic event or progression of the disease to heart failure. In this context, cell therapy is an emerging therapeutic alternative to treat cardiovascular diseases by cell administration, aimed at cardiac regeneration and repair. In this review, we will cover more than 30 years of cell therapy in cardiology, presenting the main milestones and drawbacks in the field and signaling future challenges and perspectives. The outcomes of cardiac cell therapies are discussed in three distinct aspects: The search for remuscularization by replacement of lost cells by exogenous adult cells, the endogenous stem cell era, which pursued the isolation of a progenitor with the ability to induce heart repair, and the utilization of pluripotent stem cells as a rich and reliable source of cardiomyocytes. Acellular therapies using cell derivatives, such as microvesicles and exosomes, are presented as a promising cell-free therapeutic alternative.

Keywords: Cardiac stem cell; Cardiovascular diseases; Cell therapy; Pluripotent stem cells; Progenitor cardiac cells; Stem cell.

Read this article:
Stem cell therapies in cardiac diseases: Current status and future ...

What are Brain and Spinal Cord Tumors?Overview of the brain and spinal cordWhat causes CNS tumors?Who is at risk?How are tumors graded?What are the possible symptoms?How are CNS tumors diagnosed?How are brain and spinal cord tumors treated?

NeurosurgeryRadiation TherapyRadiosurgeryChemotherapyTargeted TherapyAlternative and Complementary Therapy

What Research is Being Done?Appendix: Some CNS Tumors and Tumor-Related ConditionsWhere can I get more information?

A tumor is a mass of abnormal cells that either form into a new growth or the growth was there when you were born (congenital). Tumors occur when something goes wrong with genes that regulate cell growth, allowing cells to grow and divide out of control. Tumors can form anywhere in your body. Brain and spinal cord tumors form in the tissue inside your brain or spinal cord, which make up the central nervous system (CNS).

Depending on its type, a growing tumor may not cause any symptoms or can killor displace healthy cells or disrupt their function. A tumor can move or press on sensitive tissue and block the flow of blood and other fluid, causing pain and inflammation. A tumor can also block the normal flow of activity in the brain or signaling to and from the brain. Some tumors dont cause any changes.Tumors can be noncancerous (benign) or cancerous (malignant).

Tumors can be primary or secondary.

There are more than 120 types of brain and spinal cord tumors. Some are named by the type of normal cell they most closely resemble or by location. Brain and spinal cord tumors are not contagious or, at this time, preventable.

See theAppendix at the end of this guide for a listing of some CNS tumors and tumor-related conditions.

top

The brain has three major parts:

The brains two halves, or hemispheres, use nerve cells (neurons) to speak with each other.Each hemisphere has four sections, called lobes, which handle different neurological functions.

For more information, see General Information About Adult Central Nervous System Tumors.

The spinal cordan extension of the brainlies protected inside the bony spinal column. It contains bundles of nerves that carry messages between the brain and other parts of the body, such as instructions to move an arm or information from the skin that signals pain.

A tumor that forms on or near the spinal cord can disrupt communication between the brain and the nerves or restrict the cord's supply of blood. Because the spinal column is narrow, a tumor hereunlike a brain tumorcan cause symptoms on both sides of the body.

Spinal cord tumors, regardless of location, often cause pain, numbness, weakness or lack of coordination in the arms and legs, usually on both sides of the body. They also often cause bladder or bowel problems.

Spinal cord tumors are described based on where on the cord the tumor is located and each vertebra (part of a series of bones that form the backbone) is numbered from top to bottom. The neck region is called cervical (C), the back region is called thoracic (T), and the lower back region is called lumbar (L) or sacral/cauda equina (S). Tumors are further described by whether the tumor begins in the cells inside the spinal cord (intramedullary) or outside the spinal cord (extramedullary). Extramedullary tumors grow in the membrane surrounding the spinal cord (intradural) or outside (extradural).

top

Researchers really don't know why primary brain and spinal cord tumors develop. Possible causes include viruses, defective genes, exposure to certain chemicals and other hazardous materials, and immune system disorders. Sometimes CNS tumors may result from specific genetic diseases, such as neurofibromatosis and tuberous sclerosis, or exposure to radiation.

top

Anyone can develop a primary brain or spinal cord tumor, but the overall risk is very small. Brain tumors occur more often in males than in females and are most common in middle-aged to older persons. Although uncommon in children, brain tumors tend to occur more often in children under age 9, and some tumors tend to run in families. Most brain tumors in children are primary tumors.

Other risk factors for developing a primary brain or spinal cord tumor include race (Caucasians are more likely to develop a CNS tumor) and occupation. Workers in jobs that require repeated contact with ionizing radiation or certain chemicals, including those materials used in building supplies or plastics and textiles, have a greater chance of developing a brain tumor.

top

The grade of a tumor may be used to tell the difference between slow-growing and fast-growing types of the tumor. The World Health Organization (WHO) tumor grades are based on how abnormal the cancer cells look under the microscope and how quickly the tumor is likely to grow and spread. Some tumors change grade as they progress, usually to a higher grade. The tumor is graded by a pathologist following a biopsy or during surgery.

top

Brain and spinal cord tumors cause many different symptoms, which can make detection tricky. Symptoms depend on tumor type, location, size, and rate of growth. Certain symptoms are quite specific because they result from damage to particular areas of the brain and spinal cord. Symptoms generally develop slowly and worsen as the tumor grows.

Brain tumor

In infants, the most obvious sign of a brain tumor is a rapidly widening head or bulging crown. Other more common symptoms of a pediatric brain tumor can include:

In older children and adults, a tumor can cause a variety of symptoms, including headaches, seizures, balance problems, and personality changes.

Other symptoms may include endocrine disorders or abnormal hormonal regulation, difficulty swallowing, facial paralysis and sagging eyelids, fatigue, weakened sense of smell, or disrupted sleep and changes in sleep patterns.

Spinal cord tumors

Common symptoms of a spinal cord tumor include:

top

If you are suspected of having a brain or spinal cord tumor, your doctor (usually a neurologist, oncologist, or neuro-oncologist) will perform a neurologic exam and may order a variety of tests based on your symptoms, personal and family medical history, and results of the physical exam. Once a tumor is found on diagnostic imaging studies, surgery to obtain tissue for a biopsy or removal is often recommended. Diagnosing the type of brain or spinal cord tumor is often difficult. Some tumor types are rare and the molecular and genetic alterations of some tumors are not well understood. You may want to ask your primary care doctor or oncologist for a second opinion from a comprehensive cancer center or neuro-oncologist with experience treating your diagnosis or tumor type. Even a secondopinion that confirms the originaldiagnosis can be reassuring and help you better prepare for your care and treatment.

A neurological exam

A neurological exam can be done in your doctors office. It assesses your movement and sensory skills, hearing and speech, reflexes, vision, coordination and balance, mental status, and changes in mood or behavior.

Some advanced tests are performed and analyzed by a specialist.

Diagnostic imaging

Diagnostic imaging produces extremely detailed views of structures inside the body, including tissues, organs, bones, and nerves. Such imagingcan confirm the diagnosis and helpdoctors determine the tumor's type, treatment options, and later, whether the treatment is working.

See the NINDS publication, Neurological Diagnostic Tests and Procedures, for a more complete description of the following tests:

Usually a contrast agent (such as a dye) is injected into a vein before a CT or MRI. Many tumors become much easier to identify on the scan after the contrast is given.

Laboratory and other tests

top

A specialized team of doctors advises and assists individuals throughout treatment and rehabilitation. These doctors may include:

For more information, see: https://www.cancer.gov/rare-brain-spine-tumor/tumors/about-cns-tumors#who-treats-central-nervous-system-cns-tumors.

Your health care team will recommend a treatment plan based on the tumor's location, type, size and aggressiveness, as well as medical history, age, and general health. Malignant tumors require some form of treatment, while some small benign tumors may need onlymonitoring. Treatment for a brain or spinal tumor can include surgery, radiation therapy, chemotherapy, targeted therapy, or a combination of treatments.Initial treatment for a CNS tumor may involve a variety of drugs to treat or ease symptoms, including:

top

Surgery is usually the first treatment to both obtain tissue for diagnosis and remove as much tumor as can be done safely. Surgery may be the only treatment you need if your tumor is considered benign or low grade. Based on the type and grade (low versus high), doctors often recommend follow-up treatment, including radiation and chemotherapy, or an experimental treatment. You will be referred to the specialists above to provide guidance on this treatment.

Surgery is usually the first step in treating an accessible tumorone that can be removed without risk of neurological damage. Many low-grade tumors and secondary (metastatic) cancerous tumors can be removed entirely. Some tumors have a clearly defined shape and can be removed more easily. Your surgeon will try removing (called resecting or excising) all or as much tumor as possible. For malignant CNS tumors, this is best performed by a neurosurgeon.

An inaccessible or inoperable tumor is one that cannot be removed surgically because of the risk of severe nervous system damage during the operation. These tumors are frequently located deep within the brain or near vital structures such as the brain stem and may not have well-defined edges. In these cases, a biopsy may be performed.

A biopsy is sometimes performed to diagnose and help doctors determine how to treat a tumor. Biopsies can sometimes be performed by inserting a needle through a small hole in the body and taking a small piece of the tumor tissue. A pathologist will examine the tissue for certain changes that signal cancer and determine its stage or grade.

In some cases, a surgeon may need to insert a shunt into the skull to drain any dangerous buildup of CSF caused by the tumor. A shunt is a flexible plastic tube that is used to divert the flow of CSF from the central nervous system to another part of the body, where it can be absorbed as part of the normal circulatory process.

During surgery, some tools used in the operating room include a surgical microscope, the endoscope (a small viewing tube attached to a video camera), and miniature precision instruments that allow surgery to be performed through a small incision in the brain or spine. Other tools include:

For more information, see: Surgery to Treat Cancer.

top

Radiation therapy usually involvesrepeated doses of high-energy beams such as x-rays or protons to kill cancer cells or keep them from multiplying. Radiation therapy can shrink the tumor mass. It can be used to treat surgically inaccessible tumors or tumor cells that may remain following surgery.

Radiation treatment can be delivered externally, using focused beams of energy or charged particles that are directed at the tumor, or from inside the body, using a surgically implanted device. The stronger the radiation, the deeper it can penetrate to the target site. Healthy cells may also be damaged by radiation therapy, but current radiation treatment is designed to minimize injury to normal tissue.

Treatment often begins soon after surgery and may continue for several weeks. Depending on the tumor type and location, a person may be able to receive a modified form of therapy to lessen damage to healthy cells and improve the overall treatment.

Externally delivered radiation therapy poses no risk of radioactivity to the person or family and friends. Types of external radiation therapy include:

top

Radiosurgery is usually a one-time treatment using multiple, sharply focused radiation beams aimed at the brain or spinal cord tumor from multiple angles.It does not cut into the person but, like other forms of radiation therapy, harms a tumor cells ability to grow and divide. It is commonly used to treat surgically inaccessible tumors and maybe used at the end of conventional radiation treatment. Two common radiosurgery procedures are:

Side effects of radiation: Side effects of radiation therapy vary from person to person and are usually temporary. They typically begin about two weeks after treatment starts and may include fatigue, nausea, vomiting, reddened or sore skin in the treated area, headache, hearing loss, problems with sleep, and hair loss (although the hair usually grows back once the treatment has stopped). Radiation therapy in young children, particularly those age three years or younger, can cause problems with learning, processing information, thinking, and growing.

There are late side effects of radiation that may occur months to years after treatment that include shrinkage (atrophy) of the brain or spinal cord region that was treated.

top

Chemotherapy uses powerful drugs to kill cancer cells or stop them from growing or spreading. These drugs are usually given orally, intravenously, or through a catheter or port and travel through the body to the cancerous cells. Your oncologist will recommend a treatment plan based on the type of cancer, drug(s) to be used, the frequency of administration, and the number of cycles needed. Chemotherapy is given in cycles to more effectively damage and kill cancer cells and give normal cells time to recover from any damage.

Individuals might receive chemotherapy to shrink the tumor before surgery called neo-adjuvant therapy (a first step treatment to shrink a tumor before the primary treatment). Radiation therapy can also be given as neo-adjuvant therapy. After surgery, or radiation treatment if radiation is the primary treatment, chemotherapy could be called adjuvant therapy (treatment in addition to the primary treatment). Metronomic therapy involves continuous low-dose chemotherapy to block mechanisms that stimulate the growth of new blood vessels needed to feed the tumor.

Not all tumors are vulnerable to the same anticancer drugs, so a persons treatment may include a combination of drugs. Common CNS chemotherapies include temozolomide, carmustine (also called BCNU), lomustine (also called CCNU), and bevacizumab. Individuals should be sure to discuss all options with their medical team.

Side effects of chemotherapy may include hair loss, nausea, digestive problems, reduced bone marrow production, and fatigue. The treatment can also harm normal cells that are growing or dividing at the same time, but these cells usually recover and side effects often improve or stop once the treatment has ended.

For more information about chemotherapy, see: Chemotherapy to Treat Cancer .

top

Targeted therapy is a cancer treatment that uses drugs to target specific genes and proteins that are involved in tumor cell growth. This helps slow uncontrolled growth and reduce the production of tumor cells. Targeted therapies include oncogenes, growth factors, and molecules aimed at blocking gene activity.

Alternative and complementary approaches may help tumor patients better cope with their diagnosis and treatment. Some of these therapies, however, may be harmful if used during or after cancer treatment and should be discussed in advance with a doctor. Common approaches include nutritional and herbal supplements, vitamins, special diets, and mental or physical techniques to reduce stress.

top

Scientists continue to investigate ways to better understand, diagnose, and treat CNS tumors. Several of todays treatments were experimental therapies only a decade ago.Clinical studies are research studies that test or observe how well medical approaches work in people.Some clinical studies test new treatments such as a new drug or medical therapy. Treatment studies help researchers learn if a new treatment is effective or less harmful than standard treatments. Studies can be considered at any point, from the time of diagnosis through recurrence. For more information about clinical studies, see: National Cancer Institute Clinical Trials.

Current clinical studies of genetic risk factors, environmental causes, and molecular mechanisms of cancers may translate into tomorrows treatment of, or perhaps cure for, these tumors.Much of this work is supported by the National Institutes of Health (NIH), through the collaborative efforts of its National Institute of Neurological Disorders and Stroke (NINDS) and National Cancer Institute (NCI), as well as other federal agencies, nonprofit groups, pharmaceutical companies, and private institutions. Some of this research is conducted through the collaborative neuroscience and cancer research community at the NIH or through research grants to academic centers throughout the United States.

The jointly sponsored NCI-NINDS Neuro-Oncology Branch coordinates research to develop and test the effectiveness and safety of novel therapies for people with CNS tumors. These experimental treatment options may include new drugs, combination therapy, gene therapy, advanced imaging and artificial intelligence, biologic immuno-agents, surgery, and radiation. Information about these trials, and trials for other disorders, can be accessed at the federal governments database of clinical trials, ClinicalTrials.gov.

Scientists at NIH and universities across the United States are exploring a variety of approaches to treat CNS tumors. These experimental approaches include boosting the immune system to better fight tumor cells, developing therapies that target the tumor cell while sparing normal cells,making improvementsin radiation therapy, disabling the tumor using genes attached to viruses, and defining biomarkers that may predict the response of a CNS tumor to a particular treatment.

Biological therapy (also called immunotherapy)involves enhancing the bodys overall immune response to recognize and fight cancer cells. The immune system is designed to attack foreign substances in the body, but because cancer cells arent foreign, they usually do not generate much of an immune response. Researchers are using different methods to provoke a strong immune response to tumor cells, including:

Targeted therapy uses molecularly targeted drugs that seek out the cellular changes that convert normal cells into cancer. Targeted therapies include:

Biomarkersare molecules or other substances in the blood or tissue that can be used to diagnose or monitor a disorder. Some CNS tumor biomarkers have been found, such as the epithelial growth factor receptor (EGRF) gene. Researchers continue to search for additional clinical biomarkers of CNS tumors, to better assess risk from environmental toxins and other possible causes and monitor and predict the outcome of CNS tumor treatment. Identifying biomarkers may also lead to the development of new disease models and novel therapies for tumor treatment.

Radiation therapyresearch includes testing several new anticancer drugs, either independently or in combination with other drugs. Researchers are also investigating combined therapies including drugs, radiation, and radiosurgery to effectively treat CNS tumors. Research areas under investigation include radiosensitizersdrugs that make rapidly dividing tumor tissue more vulnerable to radiation.

Chemotherapeutic drugresearch focuses on ways to better deliver drugsacross the blood-brain barrier and into the site of the tumor. Since chemotherapeutic drugs work in different ways to stop tumor cells from dividing, several trials are testing whether giving more than one drug, and perhaps giving them in different ways (such as staggered delivery and low-dose, long-term treatment), may kill more tumor cells without causing damaging side effects than present therapy. Researchers are examining different levels of chemotherapeutic drugs to determine whether they are less toxic to normal tissue when combined with other cancer treatments, and ways to make cancer cells more sensitive to chemotherapy. Research areas include:

Surgery studies are ongoing to better define the potential benefits of surgery, including better response to biologic therapy and chemotherapy, improved quality of life, and prolonged survival.

Clinical trials can help doctors and scientists discover whether new treatments are effective and safe for many people with spinal and brain tumors. Both healthy people and those with a disease participate in clinical trials, which increases our understanding about diseases including brain and spinal tumors. To learn more about clinical trials for CNS tumors and how to participate in them, visit http://www.clinicaltrials.gov, a database of thousands of studies, some of which include results and papers on findings.

top

There are many types of brain and spinal cord tumors. These tumors are named by their location in the body, cell of origin, rate of growth, and malignancy. Some tumor types are more prevalent in children than in adults. Here is a listing of some common benign and malignant CNS tumors.

Glioma

Glioma tumorsgrow from several types of glial cells, which support the function of neurons. Gliomasusually occur in the brains cerebral hemispheres but may also strike other areas. Gliomas are classified based on the type of normal glial cells they resemble.

Mixed gliomas contain more than one type of glial cell and are usually found in the cerebrum. These tumors can spread to other sites in the brain.Other gliomas are named after the part of the body they affect. Among them are:

ChordomaChordomas are rare congenital tumors which develop from remnants of the flexible spine-like structure that forms and dissolves early in fetal development (and is later replaced by the bones of the spine). Chordomas often occur near the top or the bottom of the spine, outside the dura mater, and can invade the spinal canal and skull cavity.

Choroid plexus papillomaThis rare, usually benign childhood tumor develops slowly and can increase the production and block the flow of CSF, causing symptoms that include headaches and increased intracranial pressure. A rarer cancerous form can spread via the cerebrospinal fluid.

Germ cell tumorsThese very rare childhood tumors may start in cells that fail to leave the CNS during development. Germ cell tumors usually form in the center of the brain and can spread elsewhere in the brain and spinal cord. Different tumors are named after the type of germ cell.

MeningiomaMeningiomas are benign tumors that develop from the thin membranes, or meninges, that cover the brain and spinal cord. Meningiomas usually grow slowly, generally do not invade surrounding normal tissue, and rarely spread to other parts of the CNS or body.

Pineal TumorsThese tumors form in the pineal gland, a small structure located between the cerebellum and the cerebrum. The three most common types of pineal region tumors are gliomas, germ cell tumors, and pineal cell tumors

Pituitary Tumors (also called pituitary adenomas)These small tumors form in the pituitary gland. Most pituitary tumors are benign and their incidence increases with age. Pituitary tumors are classified as either non-secreting or secreting (secreting tumors release unusually high levels of pituitary hormones, which can trigger neurological conditions and symptoms including Cushings syndromea harmful overproduction of the hormone cortisol).

Primitive Neuroectodermal Tumors (PNET)These malignant tumors may spring from primitive or immature cells left over from early development of the nervous system. PNETS can spread throughout the brain and spinal cord in a scattered, patchy pattern and, in rare cases, cause cancer outside the CNS. The two most common PNETs are:

Vascular TumorsThese rare, noncancerous tumors arise from the blood vessels of the brain and spinal cord. The most common vascular tumor is the hemangioblastoma, a cyst-like mass of tangled blood vessels, which does not usually spread.

For information on some rare brain and spinal cord tumors, see: https://www.cancer.gov/rare-brain-spine-tumor/tumors.

Arachnoid cystsare benign, fluid-filled masses that form within a thin membrane lining (tumors are solid tissue masses). Cysts in the CNS can cause tumor-like symptoms including headache and seizures. Some cysts occur more often in the spinal cord than in the brain, and certain cysts are seen most frequently in children.

Hydrocephalusinvolves the build-up of cerebrospinal fluid in the brain. The excessive fluidcan cause harmful pressure, headaches, and nausea.

View original post here:
Brain and Spinal Cord Tumors: Hope Through Research

Basel, 23 December 2022 - Roche (SIX: RO, ROG; OTCQX: RHHBY) today announced that the U.S. Food and Drug Administration (FDA) has approved Lunsumio® (mosunetuzumab-axgb) for the treatment of adult patients with relapsed or refractory (R/R) follicular lymphoma (FL) after two or more lines of systemic therapy. This indication is approved under accelerated approval based on response rate. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial. Lunsumio, a CD20xCD3 T-cell engaging bispecific antibody, represents a new class of fixed-duration cancer immunotherapy, which is off-the-shelf and readily available, so that patients do not have to wait to start treatment. Lunsumio will be available in the United States in the coming weeks. “This approval is a significant milestone for people with relapsed or refractory follicular lymphoma, who have had limited treatment options until now,” said Elizabeth Budde, M.D., Ph.D., Haematologic Oncologist and Associate Professor, City of Hope Division of Lymphoma, Department of Hematology & Hematopoietic Cell Transplantation, and Lunsumio clinical trial investigator. “As a first-in-class T-cell engaging bispecific antibody that can be initiated in an outpatient setting, Lunsumio’s high response rates and fixed-duration could change the way advanced follicular lymphoma is treated.”“Despite treatment advances, follicular lymphoma remains incurable and relapse is common, with outcomes worsening following each consecutive treatment,” said Levi Garraway, M.D., Ph.D., Roche’s Chief Medical Officer and Head of Global Product Development. “Lunsumio represents our first approved T-cell engaging bispecific antibody and builds on our legacy of more than 20 years of innovation in blood cancer.”The FDA approval is based on positive results from the phase II GO29781 study of Lunsumio in people with heavily pre-treated FL, including those who were at high risk of disease progression or whose disease was refractory to prior therapies. Results from the study showed high and durable response rates. An objective response was seen in 80% (72/90 [95% confidence interval (CI): 70-88]) of patients treated with Lunsumio, with a majority maintaining responses for at least 18 months (57% [95% CI: 44-70]). The objective response rate is the combination of complete response (CR) rate (a disappearance of all signs and symptoms of cancer) and partial response rate (a decrease in the amount of cancer in the body). The median duration of response among those who responded was almost two years (22.8 months [95% CI: 10-not reached]). A CR was achieved in 60% of patients (54/90 [95% CI: 49-70]). Among 218 patients with haematologic malignancies who received Lunsumio at the recommended dose, the most common adverse event (AE) was cytokine release syndrome (CRS; 39%), which can be severe and life-threatening. The median duration of CRS events was three days (range: 1-29). Other common AEs (?20%) included fatigue, rash, pyrexia and headache.Lunsumio is administered as an intravenous infusion for a fixed-duration, which allows for time off therapy, and can be infused in an outpatient setting. Hospitalisation may be needed to manage select AEs, should be considered for subsequent infusions following a Grade 2 CRS event, and is recommended for subsequent infusions following a Grade 3 CRS event.Lunsumio was developed based on the Roche Group's broad expertise in creating bispecific antibodies. Lunsumio is designed to address the diverse needs of people with blood cancer, physicians, and practice settings, and is part of the company’s robust bispecific antibody clinical programme in lymphoma. Lunsumio is being further investigated as a subcutaneous formulation (i.e., administered under the skin) and in phase III studies that will expand the understanding of its impact in earlier lines of treatment in people with non-Hodgkin lymphoma.About the GO29781 studyThe GO29781 study [NCT02500407] is a phase II, multicentre, open-label, dose-escalation and expansion study evaluating the safety, efficacy and pharmacokinetics of Lunsumio® (mosunetuzumab-axgb) in people with relapsed or refractory B-cell non-Hodgkin lymphoma. Outcome measures include complete response rate (best response) by independent review facility (primary endpoint), objective response rate, duration of response, progression-free survival, safety, and tolerability (secondary endpoints).About follicular lymphomaFollicular lymphoma (FL) is the most common slow-growing (indolent) form of non-Hodgkin lymphoma, accounting for about one in five cases.1 It typically responds well to treatment but is often characterised by periods of remission and relapse. The disease typically becomes harder to treat each time a patient relapses, and early progression can be associated with poor long-term prognosis. It is estimated that, in the United States, approximately 13,000 new cases of FL will be diagnosed in 2022 and more than 100,000 people are diagnosed with FL each year worldwide.1,2About Lunsumio® (mosunetuzumab-axgb)Lunsumio is a first-in-class CD20xCD3 T-cell engaging bispecific antibody designed to target CD20 on the surface of B-cells and CD3 on the surface of T-cells. This dual targeting activates and redirects a patient’s existing T-cells to engage and eliminate target B-cells by releasing cytotoxic proteins into the B-cells. A robust clinical development programme for Lunsumio is ongoing, investigating the molecule as a monotherapy and in combination with other medicines, for the treatment of people with B-cell non-Hodgkin lymphomas, including follicular lymphoma and diffuse large B-cell lymphoma, and other blood cancers.About Roche in haematologyRoche has been developing medicines for people with malignant and non-malignant blood diseases for more than 20 years; our experience and knowledge in this therapeutic area runs deep. Today, we are investing more than ever in our effort to bring innovative treatment options to patients across a wide range of haematologic diseases. Our approved medicines include MabThera®/Rituxan® (rituximab), Gazyva®/Gazyvaro® (obinutuzumab), Polivy® (polatuzumab vedotin), Venclexta®/Venclyxto® (venetoclax) in collaboration with AbbVie, Hemlibra® (emicizumab) and Lunsumio® (mosunetuzumab-axgb). Our pipeline of investigational haematology medicines includes T-cell engaging bispecific antibodies, glofitamab, targeting both CD20 and CD3, and cevostamab, targeting both FcRH5 and CD3; Tecentriq® (atezolizumab), a monoclonal antibody designed to bind with PD-L1 and crovalimab, an anti-C5 antibody engineered to optimise complement inhibition. Our scientific expertise, combined with the breadth of our portfolio and pipeline, also provides a unique opportunity to develop combination regimens that aim to improve the lives of patients even further.About Roche Founded in 1896 in Basel, Switzerland, as one of the first industrial manufacturers of branded medicines, Roche has grown into the world’s largest biotechnology company and the global leader in in-vitro diagnostics. The company pursues scientific excellence to discover and develop medicines and diagnostics for improving and saving the lives of people around the world. We are a pioneer in personalised healthcare and want to further transform how healthcare is delivered to have an even greater impact. To provide the best care for each person we partner with many stakeholders and combine our strengths in Diagnostics and Pharma with data insights from the clinical practice.In recognising our endeavour to pursue a long-term perspective in all we do, Roche has been named one of the most sustainable companies in the pharmaceuticals industry by the Dow Jones Sustainability Indices for the thirteenth consecutive year. This distinction also reflects our efforts to improve access to healthcare together with local partners in every country we work. Genentech, in the United States, is a wholly owned member of the Roche Group. Roche is the majority shareholder in Chugai Pharmaceutical, Japan.

Link:
FDA approves Roche’s Lunsumio, a first-in-class bispecific antibody, to treat people with relapsed or refractory follicular lymphoma

Sung H, Ferlay J, Siegel RL, Laversanne M, Soerjomataram I, Jemal A, et al. Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin. 2021;71(3):20949.

Article PubMed Google Scholar

Biller LH, Schrag D. Diagnosis and treatment of metastatic colorectal cancer: a review. JAMA. 2021;325(7):66985.

Article CAS PubMed Google Scholar

Cortes-Hernandez LE, Eslami SZ, Costa-Silva B, Alix-Panabieres C. Current applications and discoveries related to the membrane components of circulating tumor cells and extracellular vesicles. Cells. 2021;10(9):221.

Keller L, Pantel K. Unravelling tumour heterogeneity by single-cell profiling of circulating tumour cells. Nat Rev Cancer. 2019;19(10):55367.

Article CAS PubMed Google Scholar

Alix-Panabires C, Pantel K. Liquid biopsy: from discovery to clinical application. Cancer Discovery. 2021;11(4):85873.

Article PubMed Google Scholar

Baccelli I, Schneeweiss A, Riethdorf S, Stenzinger A, Schillert A, Vogel V, et al. Identification of a population of blood circulating tumor cells from breast cancer patients that initiates metastasis in a xenograft assay. Nat Biotechnol. 2013;31(6):53944.

Article CAS PubMed Google Scholar

Hamilton G, Burghuber O, Zeillinger R. Circulating tumor cells in small cell lung cancer: ex vivo expansion. Lung. 2015;193(3):4512.

Article PubMed Google Scholar

Hodgkinson CL, Morrow CJ, Li Y, Metcalf RL, Rothwell DG, Trapani F, et al. Tumorigenicity and genetic profiling of circulating tumor cells in small-cell lung cancer. Nat Med. 2014;20(8):897903.

Article CAS PubMed Google Scholar

Jordan NV, Bardia A, Wittner BS, Benes C, Ligorio M, Zheng Y, et al. HER2 expression identifies dynamic functional states within circulating breast cancer cells. Nature. 2016;537(7618):1026.

Article CAS PubMed PubMed Central Google Scholar

Lu J, Fan T, Zhao Q, Zeng W, Zaslavsky E, Chen JJ, et al. Isolation of circulating epithelial and tumor progenitor cells with an invasive phenotype from breast cancer patients. Int J Cancer. 2010;126(3):66983.

Article CAS PubMed PubMed Central Google Scholar

Bobek V, Gurlich R, Eliasova P, Kolostova K. Circulating tumor cells in pancreatic cancer patients: enrichment and cultivation. World J Gastroenterol: WJG. 2014;20(45):17163.

Article PubMed PubMed Central Google Scholar

Bobek V, Matkowski R, Grlich R, Grabowski K, Szelachowska J, Lischke R, et al. Cultivation of circulating tumor cells in esophageal cancer. Folia Histochem Cytobiol. 2014;52(3):1717.

Article PubMed Google Scholar

Cayrefourcq L, Mazard T, Joosse S, Solassol J, Ramos J, Assenat E, et al. Establishment and characterization of a cell line from human circulating colon cancer cells. Cancer Res. 2015;75(5):892901.

Article CAS PubMed Google Scholar

Cegan M, Kolostova K, Matkowski R, Broul M, Schraml J, Fiutowski M, et al. In vitro culturing of viable circulating tumor cells of urinary bladder cancer. Int J Clin Exp Pathol. 2014;7(10):7164.

PubMed PubMed Central Google Scholar

Kolostova K, Matkowski R, Grlich R, Grabowski K, Soter K, Lischke R, et al. Detection and cultivation of circulating tumor cells in gastric cancer. Cytotechnology. 2016;68(4):1095102.

Article CAS PubMed Google Scholar

Rossi E, Rugge M, Facchinetti A, Pizzi M, Nardo G, Barbieri V, et al. Retaining the long-survive capacity of circulating tumor cells (CTCs) followed by xeno-transplantation: not only from metastatic cancer of the breast but also of prostate cancer patients. Oncoscience. 2014;1(1):49.

Article PubMed Google Scholar

Bobek V, Kacprzak G, Rzechonek A, Kolostova K. Detection and cultivation of circulating tumor cells in malignant pleural mesothelioma. Anticancer Res. 2014;34(5):25659.

PubMed Google Scholar

Zhang Y, Zhang X, Zhang J, Sun B, Zheng L, Li J, et al. Microfluidic chip for isolation of viable circulating tumor cells of hepatocellular carcinoma for their culture and drug sensitivity assay. Cancer Biol Ther. 2016;17(11):117787.

Article CAS PubMed PubMed Central Google Scholar

Yu M, Bardia A, Aceto N, Bersani F, Madden MW, Donaldson MC, et al. Cancer therapy. Ex vivo culture of circulating breast tumor cells for individualized testing of drug susceptibility. Science. 2014;345(6193):21620.

Article CAS PubMed PubMed Central Google Scholar

Zhang L, Ridgway LD, Wetzel MD, Ngo J, Yin W, Kumar D, et al. The identification and characterization of breast cancer CTCs competent for brain metastasis. Sci Transl Med. 2013;5(180):180ra48.

Article PubMed Google Scholar

Praharaj PP, Bhutia SK, Nagrath S, Bitting RL, Deep G. Circulating tumor cell-derived organoids: current challenges and promises in medical research and precision medicine. Biochim Biophys Acta Rev Cancer. 2018;1869(2):11727.

Article CAS PubMed PubMed Central Google Scholar

Tellez-Gabriel M, Cochonneau D, Cade M, Jubellin C, Heymann MF, Heymann D. Circulating tumor cell-derived pre-clinical models for personalized medicine. Cancers (Basel). 2018;11(1):19.

Yang C, Xia BR, Jin WL, Lou G. Circulating tumor cells in precision oncology: clinical applications in liquid biopsy and 3D organoid model. Cancer Cell Int. 2019;19:341.

Article CAS PubMed PubMed Central Google Scholar

Zhang Z, Shiratsuchi H, Lin J, Chen G, Reddy RM, Azizi E, et al. Expansion of CTCs from early stage lung cancer patients using a microfluidic co-culture model. Oncotarget. 2014;5(23):1238397.

Article PubMed PubMed Central Google Scholar

Khoo BL, Grenci G, Lim YB, Lee SC, Han J, Lim CT. Expansion of patient-derived circulating tumor cells from liquid biopsies using a CTC microfluidic culture device. Nat Protoc. 2018;13(1):3458.

Article CAS PubMed Google Scholar

Liu X, Li J, Cadilha BL, Markota A, Voigt C, Huang Z, et al. Epithelial-type systemic breast carcinoma cells with a restricted mesenchymal transition are a major source of metastasis. Sci Adv. 2019;5(6):eaav4275.

Article PubMed PubMed Central Google Scholar

Vishnoi M, Liu NH, Yin W, Boral D, Scamardo A, Hong D, et al. The identification of a TNBC liver metastasis gene signature by sequential CTC-xenograft modeling. Mol Oncol. 2019;13(9):191326.

Article CAS PubMed PubMed Central Google Scholar

Diamantopoulou Z, Castro-Giner F, Aceto N. Circulating tumor cells: ready for translation? J Exp Med. 2020;217(8):e20200356.

Sato T, Stange DE, Ferrante M, Vries RG, Van Es JH, Van den Brink S, et al. Long-term expansion of epithelial organoids from human colon, adenoma, adenocarcinoma, and Barrett's epithelium. Gastroenterology. 2011;141(5):176272.

Article CAS PubMed Google Scholar

Hu Y, Smyth GK. ELDA: extreme limiting dilution analysis for comparing depleted and enriched populations in stem cell and other assays. J Immunol Methods. 2009;347(1-2):708.

Article CAS PubMed Google Scholar

Baiocchi M, Biffoni M, Ricci-Vitiani L, Pilozzi E, De Maria R. New models for cancer research: human cancer stem cell xenografts. Curr Opin Pharmacol. 2010;10(4):3804.

Article CAS PubMed Google Scholar

De Angelis ML, Francescangeli F, Zeuner A, M. B. In: Elsevier, editor. In press Orthotopic xenografts of colorectal cancer stem cells: Springer; 2021.

Google Scholar

Agnoletto C, Corr F, Minotti L, Baldassari F, Crudele F, Cook WJJ, et al. Heterogeneity in circulating tumor cells: the relevance of the stem-cell subset. Cancers (Basel). 2019;11(4):483.

Article CAS Google Scholar

Scholch S, Garcia SA, Iwata N, Niemietz T, Betzler AM, Nanduri LK, et al. Circulating tumor cells exhibit stem cell characteristics in an orthotopic mouse model of colorectal cancer. Oncotarget. 2016;7(19):2723242.

Article PubMed PubMed Central Google Scholar

OBrien CA, Pollett A, Gallinger S, Dick JE. A human colon cancer cell capable of initiating tumour growth in immunodeficient mice. Nature. 2007;445(7123):10610.

Article PubMed Google Scholar

Ricci-Vitiani L, Lombardi DG, Pilozzi E, Biffoni M, Todaro M, Peschle C, et al. Identification and expansion of human colon-cancer-initiating cells. Nature. 2007;445(7123):1115.

Article CAS PubMed Google Scholar

Kreso A, Van Galen P, Pedley NM, Lima-Fernandes E, Frelin C, Davis T, et al. Self-renewal as a therapeutic target in human colorectal cancer. Nat Med. 2014;20(1):2936.

Article CAS PubMed Google Scholar

Klameth L, Rath B, Hochmaier M, Moser D, Redl M, Mungenast F, et al. Small cell lung cancer: model of circulating tumor cell tumorospheres in chemoresistance. Sci Rep. 2017;7(1):5337.

Article PubMed PubMed Central Google Scholar

Mout L, van Dessel LF, Kraan J, de Jong AC, Neves RPL, Erkens-Schulze S, et al. Generating human prostate cancer organoids from leukapheresis enriched circulating tumour cells. Eur J Cancer. 2021;150:17989.

Article CAS PubMed Google Scholar

Pavese JM, Bergan RC. Circulating tumor cells exhibit a biologically aggressive cancer phenotype accompanied by selective resistance to chemotherapy. Cancer Lett. 2014;352(2):17986.

Article CAS PubMed PubMed Central Google Scholar

Ramesh V, Brabletz T, Ceppi P. Targeting EMT in cancer with repurposed metabolic inhibitors. Trends Cancer. 2020;6(11):94250.

Article CAS PubMed Google Scholar

Kanwar J, Samarasinghe R, Kanwar R. Natural therapeutics targeting Survivin. Biochemistry & Analytical. Biochemistry. 2012;1(6):1000e121.

Google Scholar

Siegelin MD, Reuss DE, Habel A, Rami A, von Deimling A. Quercetin promotes degradation of survivin and thereby enhances death-receptor-mediated apoptosis in glioma cells. Neuro-Oncology. 2009;11(2):12231.

Article CAS PubMed PubMed Central Google Scholar

Voges Y, Michaelis M, Rothweiler F, Schaller T, Schneider C, Politt K, et al. Effects of YM155 on survivin levels and viability in neuroblastoma cells with acquired drug resistance. Cell Death Dis. 2016;7(10):e2410.

Article CAS PubMed PubMed Central Google Scholar

Le Gal K, Ibrahim MX, Wiel C, Sayin VI, Akula MK, Karlsson C, et al. Antioxidants can increase melanoma metastasis in mice. Sci Transl Med. 2015;7(308):308re8.

PubMed Google Scholar

Piskounova E, Agathocleous M, Murphy MM, Hu Z, Huddlestun SE, Zhao Z, et al. Oxidative stress inhibits distant metastasis by human melanoma cells. Nature. 2015;527(7577):18691.

Article CAS PubMed PubMed Central Google Scholar

Gao D, Vela I, Sboner A, Iaquinta PJ, Karthaus WR, Gopalan A, et al. Organoid cultures derived from patients with advanced prostate cancer. 2014;159(1):17687.

Chen H, Gotimer K, De Souza C, Tepper CG, Karnezis AN, Leiserowitz GS, et al. Short-term organoid culture for drug sensitivity testing of high-grade serous carcinoma. 2020;157(3):78392.

Kopper O, De Witte CJ, Lhmussaar K, Valle-Inclan JE, Hami N, Kester L, et al. An organoid platform for ovarian cancer captures intra-and interpatient heterogeneity. 2019;25(5):83849.

Lin K-C, Ting L-L, Chang C-L, Lu L-S, Lee H-L, Hsu F-C, et al. Ex vivo expanded circulating tumor cells for clinical anti-cancer drug prediction in patients with head and neck cancer. 2021;13(23):6076.

Yang L, Yang S, Li X, Li B, Li Y, Zhang X, et al. Tumor organoids: from inception to future in cancer research. Cancer Lett. 2019;454:12033.

Article CAS PubMed Google Scholar

Hartwell KA, Muir B, Reinhardt F, Carpenter AE, Sgroi DC, Weinberg RA. The Spemann organizer gene, Goosecoid, promotes tumor metastasis. Proc Natl Acad Sci U S A. 2006;103(50):1896974.

Article CAS PubMed PubMed Central Google Scholar

Xue TC, Ge NL, Zhang L, Cui JF, Chen RX, You Y, et al. Goosecoid promotes the metastasis of hepatocellular carcinoma by modulating the epithelial-mesenchymal transition. PLoS One. 2014;9(10):e109695.

Article PubMed PubMed Central Google Scholar

Ischenko I, Petrenko O, Hayman MJ. Analysis of the tumor-initiating and metastatic capacity of PDX1-positive cells from the adult pancreas. PNAS. 2014;111(9):346671.

Read more from the original source:
An organoid model of colorectal circulating tumor cells with stem cell ...

Burn wound healing involves a series of complex processes which are subject to intensive investigations to improve the outcomes, in particular, the healing time and the quality of the scar. Burn injuries, especially severe ones, are proving to have devastating effects on the affected patients. Stem cells have been recently applied in the field to promote superior healing of the wounds. Not only have stem cells been shown to promote better and faster healing of the burn wounds, but also they have decreased the inflammation levels with less scar progression and fibrosis. This review aims to highlight the beneficial therapeutic effect of stem cells in burn wound healing and to discuss the involved pathways and signaling molecules. The review covers various types of burn wound healing like skin and corneal burns, along with the alternative recent therapies being studied in the field of burn wound healing. The current reflection of the attitudes of people regarding the use of stem cells in burn wound healing is also stated.

The use of stem cell therapy is the yet to be discovered gold mine of science. A myriad of studies using stem cells are being done with promising results in various fields ranging from oncologic and hematologic diseases to organ transplants and wound healing. In the field of wound healing, the use of different types of stem cells has been reported for different types of wounds [13]. Burn wounds were of special interest due to the large number of cases of burns encountered nowadays, especially in the Middle Eastern Region and specifically in those areas with armed conflicts. Burn wounds have proven to be capable of having a devastating effect both functionally and cosmetically, necessitating the search for a better and more efficient cure. Being a very hot topic in the present field of research with constant studies and updates necessitated an updated review that encompasses the recent advances in stem cell therapy for burn wound healing in addition to relevant experimental studies. The literature was searched using the key words burn, stem cells, and wound healing. CINAHL, PubMed, EMBASE, and Medline were used as search engines to broaden the resources. The studies reported were not limited neither to humans nor by language and were mostly on animals unless otherwise specified. They are mostly reported in a chronological order of their publication dates, except when found relevant to group and mentioning some related studies consecutively.

Stem cells are undifferentiated pluripotential cells that are capable of producing other types of cells, including new stem cells identical to mother cells [4]. Stem cells can be of embryonal origin or adult origin, depending on the type of tissue they are derived from [4]. Embryonal stem cells are derived from either embryonal tissue or from germ cells in adults [4]. On the other hand, adult stem cells are derived from adult tissues of different organs, especially those with a high turnover rate such as intestines and bone marrow [4].

Stem cells have been implicated in the healing of wounds in general. However, the methods of application of the stem cells in burn wound healing are diverse, including topical application, local injection, intravenous or systemic injection, and dermal or carrier application. Several studies have shown the efficacy of stem cells in promoting faster and superior wound healing. Alexaki et al. [5] successfully used adipose derived mesenchymal stem cells in wound healing in mice and compared their effect with dermal fibroblasts. The application of stem cells in wounds promoted more efficient reepithelialization by their proliferative effect on keratinocytes [5]. Moreover, this effect of stem cells was found to be mediated by keratinocyte growth factor-1 (KGF-1) and platelet derived growth factor-BB (PDGF-BB) [5]. Amniotic fluid derived stem cells have also been used in wound healing. Skardal et al. [6] tested the effect of amniotic fluid derived stem cells in wound healing in a mouse model. Wound closure, reepithelialization, and angiogenesis were more rapid in mice treated with the stem cells in comparison to those treated with fibrin collagen gel only [6]. Additionally, stem cells did not integrate permanently in the tissue, thus, suggesting that their effect is due to released factors and not by direct interaction [6]. Additionally, bone marrow derived mesenchymal stem cells have also been used in wound healing. Leonardi et al. [7] utilized bone marrow derived stem cells in artificial dermal substitutes to promote wound healing. These stem cells were shown to increase vascular density in the wounds along with the rate of reepithelialization [7]. A study by Zhang et al. [8] examined the effect of activin signaling on the homing of stem cells to wound sites. It was also found that JNK and ERK signaling pathways were involved in activin signaling and eventually the homing of stem cells [8].

Concerning the physiology by which stem cells enhance the process of burn wound healing, several studies have been reported. Mansilla et al. [9] found evidence of cells in the bloodstream with identical phenotypes to mesenchymal bone marrow stem cells after acute large skin burns. Hence, it was concluded that these stem cells may have a role in promoting wound healing in burns. In a similar study, Fox et al. [10] reported increased levels of bone marrow derived endothelial progenitor cells in burn patients. These levels were proportional to the extent of the burn. The study also showed increased levels of angiogenic cytokines which may be involved in the signaling pathway for promoting the release of bone marrow derived stem cells. Focusing on the role of cytokines in burn wound healing, Payne et al. [11] studied the role of amnion derived cellular cytokine solution. In the study, Payne et al. used amnion derived multipotent progenitor cells to harvest cytokines and apply them in burn wound healing. Amnion derived cellular cytokine solution showed statistically significant improvement in the epithelialization of the burn wounds and the appearance of hair growth compared to controls [11]. In addition, the results demonstrated a faster epithelialization in burn wounds with increased frequency of application of the cytokines, further strengthening the role of stem cell derived cytokines in burn wound healing [11]. Furthermore, Foresta et al. [12] reported a positive linear correlation between endothelial progenitor cell blood levels and the total body surface area burnt. There was an increased level of endothelial progenitor cells in the bloodstream after escharectomy, posing a possible role of escharectomy in burn wound healing [12]. Additionally, stem cells could work by the release of bioactive peptides as proposed by Cabrera et al. [13] in their study where they showed that stem cells have an active role in burn wound healing by producing bioactive peptides, such as thymosin 4 and others.

More recent studies have also highlighted the role of stem cells in the process of wound healing in general and burn wound healing in specific. Koenen et al. [14] isolated acute wound fluids and chronic wound fluids and compared their effects on adipose tissue derived stem cell function in wounds. They came to the conclusion that acute wound fluids had a positive effect on the proliferation of adipose derived stem cells in wounds [14] while chronic wound fluids had a negative effect; the mentioned findings might explain the insufficient and slow healing process in chronic wounds due to a stem cell deficiency [14]. Furthermore, stem cells have been shown to decrease dermal fibrosis development in burn wound healing in mice [15]. Wu et al. performed a series of experiments which showed that bone marrow derived mesenchymal stem cells stimulate the formation of a basket weave organization of collagen in bleomycin treated skin, similar to normal skin [15]. Additionally, stem cell treatment of the skin decreased markers of myofibroblasts and downregulated type I collagen, leading to a decrease in the fibrosis that could have occurred to the skin [15]. Consequently, the role of stem cells in decreasing bleomycin induced fibrosis may be extrapolated to decrease fibrosis in burn wounds and improve their healing with less scar formation. Moreover, Lough et al. [16] performed a study in mice which showed a role for intestine derived human alpha defensin 5 in enhancing wound healing and decreasing its bacterial load. It induces leucine-rich repeat-containing G-protein-coupled receptors which are markers of adult epithelial stem cells both in skin and intestine [16]. Also implicated in the role of stem cells in burn wound healing is the role of SDF-1/CXCR4 signaling; Ding et al. [17] used interferon a2b in patients with burn wounds to suppress SDF-1/CXCR4 signaling. They found out that the decreased levels of signaling lead to better remodeling of hypertrophic scarring in the wounds [17]. Additional studies on the CXCR4 signaling pathway were done by Yang et al. [18] on irradiated mice. The mice having an overexpression of CXCR4, a receptor involved in the homing and migration of several stem cell types, showed an accelerated wound healing time [18]. Furthermore, Hu et al. [19] injected bone marrow derived mesenchymal stem cells into mice and studied the effect of blocking CXCR4 receptors. They found out that blocking the CXCL12/CXCR4 pathway, leading to activation of CXCR4, caused delayed wound closure in inflicted burn wounds. Moreover, CXCL12 levels were elevated in the burn wound one week after injury [19]. Hence, stem cells seem to be attracted to and attach to the burnt injury site by the CXCL12/CXCR4 pathway involving the CXCR4 receptors [18, 19]. The role of the ligand for the CXCR4 receptors, stromal cell derived factor-1 alpha (SDF-1a), has also been studied. L et al. [20] performed a study on the role of SDF-1a and its relation to the expression of miR-27b. It was found that SDF-1a expression was suppressed by direct binding of the miRNA to its 39UTR site [20]. As expected, miRNA expression was suppressed in wounds hence allowing better SDF-1a signaling and more homing of stem cells to the burn wounds [20]. In particular, miR-27b was found to be involved in the burn margins of wounds and in the mobilization of stem cells to the epidermis [20]. Chen et al. [21] performed experiments using porcine acellular dermal matrix on rats with inflicted 2nd degree burns. It stimulated collagen synthesis and stem cell proliferation and differentiation; porcine acellular matrix treated rats had a better and faster healing of the wounds.

Thus, in brief, the process of burn wound healing involves different types of growth factors, receptors, and cytokines. These factors are related to stem cell homing, differentiation, and proliferation. Additionally, when applied to burn wounds, they led to a better and faster healing process.

The use of stem cells for burn wound healing, as reported in the literature, dates back to 2003 with Shumakov et al. [22]. Shumakov et al. were the first to use mesenchymal bone marrow derived stem cells (BMSC) in burn wound healing and compared them to embryonic fibroblasts [22]. The experiments were done on rats where mesenchymal bone marrow derived stem cells were applied to wounds showing decreased cell infiltration of the wound and an accelerated formation of new vessels and granulation tissue in comparison with embryonic fibroblasts and controls (burn wounds with no transplanted cells) [22]. Hence, this study marked a new era in the research of burn wound healing by being the first to test the use of stem cells in this complex process. Following this, a study by Chunmeng et al. [23] found that systemic transplantation of dermis derived multipotent cells promoted the healing of wounds in irradiated rats compared to controls with no transplantation, noting that topical transplantation of the cells had no superior effect. In 2004, Rasulov et al. [24] were the first to report using bone marrow mesenchymal stem cells in humans; a female patient with extensive skin burns (IIIB 30% of body surface area) had the stem cells applied onto the burn surface. The application of stem cells caused faster wound healing and active neoangiogenesis [24]. Another study done by Rasulov et al. on rats also showed the superiority of stem cells in burn wound healing [25]. In the rat study, the application of mesenchymal stem cells on burns reduced cell infiltration, improved neoangeogenesis, and reduced the formation of granulation tissue [25]. The aforementioned conditions created a better medium for wound healing in burns. In a similar effort, Liu et al. [26] performed experiments on pigs where they applied collagen scaffolds with seeded mesenchymal stem cells onto the surface of inflicted burns; the latter were found to induce better burn wound healing with less contraction and better vascularization and keratinization. Moreover, in human cutaneous radiation wounds, Lataillade et al. [27, 28] reported two cases where stem cells where used to aid in burn wound healing. Mesenchymal stem cells were applied, in addition to surgical excision, flaps, and grafts, to burn wounds of cutaneous radiation patients. In these patients, the application of the mesenchymal stem cells decreased the levels of inflammation and promoted a better healing [27, 28]. Further on the role of stem cells in irradiated skin were the studies conducted by Dong et al. [29, 30], where they additionally inserted a vector of human beta defensin 2 into the stem cells. The mentioned studies showed a positive role for stem cells transfected with beta defensin 2 in burn wound healing by exhibiting antibacterial properties in infected burn wounds [29, 30]. In a similar experiment, Ha et al. [31] transfected mesenchymal stem cells with vectors of hepatocyte growth factor. The experiment, done on rats, compared the wound healing of a partial thickness burn treated with stem cells alone or stem cells transfected with hepatocyte growth factor [31]. The group treated with the transfected stem cells showed a significantly larger range of reepidermalization starting the first week, along with a thicker epidermis and lower content of collagen I at 3 weeks after burn [31]. In the same year (2010), Agay et al. [32] performed experimental studies by inflicting pigs with cutaneous radiation and studying the role of stem cells in the healing of the wounds. Intradermal mesenchymal stem cell injections were given locally in the affected area. They led to the accumulation of lymphocytes in the wound with better vascularization compared to controls (pigs with no injections of mesenchymal stem cells) [32]. Later on, Riccobono et al. [33] studied, in another experiment, the role of adipose tissue derived stem cells in the treatment of cutaneous radiation. Autologous, allogeneic, and acellular (empty, control) vehicles of adipose derived stem cells were grafted onto the burn wound areas [33]. Autologous but not allogeneic adipose derived stem cells were found to promote superior burn wound healing with no necrosis and decreased pain [33].

Aside to direct stem cell application to burn wounds, Kinoshita et al. [34] inflicted cutaneous radiation wounds to pigs and used expanders with and without basic fibroblast growth factor to determine their effect on burn wound healing. The group with basic fibroblast growth factor and expander showed greater proliferation of the dermis and epidermis along with increased neoangiogenesis [34]. Thus, basic fibroblast growth factor, which is known to promote the proliferation of mesenchymal stem cells, improved burn wound healing [34, 35].

In 2010, Yan et al. [36] studied the efficacy of porcine bone marrow derived mesenchymal stem cells combined with skin derived keratinocytes, both infected with recombinant retrovirus expressing human (h) platelet derived growth factor-A, in the healing of irradiated skin. The cells were loaded onto a cultured cutaneous substitute and compared their effect on healing with a cell-free cultured cutaneous substitute [36]. The substitute with cells stimulated faster healing, epithelialization, angiogenesis, and better granulation of the burn wound [36]. In another experiment, Collawn et al. [37] inflicted laser burn wounds to organotypic raft cultures. The burn wounds were treated with dermal grafts with and without adipose derived stromal cells [37]. The adipose derived stromal cell-containing grafts showed complete healing of the epidermis after two days, whereas the cell-free grafts still had areas of injury; hence, those stem cells had a role in promoting faster healing of the burnt areas [37]. More on cutaneous radiation treatment came from Xia et al. [38] who transfected human vascular endothelial growth factor 165 and human beta defensin 3 into bone marrow derived mesenchymal stem cells and used the cells to treat irradiated skin. The stem cell treated area, in comparison with cell-free controls, showed shorter healing times with better granulation and collagen deposition [38]. Additionally, Xue et al. [39] examined the effect of human mesenchymal stem cells in mouse models. Mice with inflicted burn wounds were injected locally, in the burn area, with the stem cells (controls injected cell-free injections) [39]. Wound healing was significantly faster when stem cells were included in the injection with an increased and denser neoangiogenesis [39]. Stem cell injections also had a role in resuming activity and regaining body weight more rapidly [39]. Similarly, Mansilla et al. [40] used mesenchymal stem cells in burn wound healing in pigs through an acellular dermal matrix embedded with anti-CD44 antibodies to promote homing and attachment of the stem cells [40]. This study concluded that the use of these dermal matrices with stem cells not only promoted better healing of the burn wound, but also stimulated the formation of hair follicles and regeneration of muscles and ribs [40].

Concerning stem cells from human umbilical cords, Liu et al. [41] studied the effect of human umbilical cord derived mesenchymal stem cells in the healing of severe burns inflicted in rats. The stem cells were intravenously injected into the affected rats [41]. Liu et al. found that the injection of the stem cells into the rats accelerated the wound healing compared to controls, decreased the count of inflammatory cells, downregulated interleukins 1 and 6, and increased the levels of interleukin 10 and TSG-6 [41]. Moreover, stem cell injected rats had increased neovascularization and VEGF levels [41]. Not only do stem cells promote faster wound healing in burns, but also they prevent the progression of burn injuries as showed by Singer et al. [42]. The latter performed an experiment while inflicting thermal burns to rats, with several rectangular burns on each rat separated by unburned interspaces [42]. Some of the rats received tail vein injections of mesenchymal stem cells, while others received saline injections [42]. After 7 days, all of the unburned spaces in the controls were necrotic [42]. However, 20% of the unburned spaces in rats with stem cells injections did not necrose [42]. Consequently, stem cells were also shown to play a possible role in the prevention of progression of burn injuries. Furthermore, in a study by Xu et al. [43], applying autologous bone marrow derived mesenchymal stem cells to grafted burn wounds, they demonstrated decreased contraction of the grafts.

In 2014, Yang et al. [44] attempted to integrate mesenchymal stem cells with fibrin glue into the dressing of burn wounds. They inflicted scald wounds on the back of rats and applied dressing with fibrin glue and stem cells in one group, fibrin glue only in the second, and no intervention in the third [44]. One month later, the treatment group with fibrin glue and stem cells showed significantly faster healing than the other two; moreover, this group had more proliferation of sebaceous glands and the appearance of hair follicle-like structures which were not present in the other groups [44]. In another experiment, Lough et al. [45] isolated leucine-rich repeat-containing G-protein coupled receptor 6 (LGR6+) epithelial stem cells from the adnexal compartment of the skin of mice. They injected the harvested stem cells locally into inflicted burn wounds [45]. The wounds injected with stem cells showed a better healing along with increased vascular endothelial growth factor, platelet derived growth factor, and epidermal growth factor levels [45]. Stem cell injection also promoted the formation of nascent hair follicles and better neoangiogenesis in the wounds of the affected mice [45].

On the other hand, it is very pertinent to report another study in 2014 by Loder et al. [46] where they also tested the effect of adipose derived stem cells in the treatment of burns. The mice with inflicted burns that received stem cells injections showed no significant difference in comparison to controls (received saline injections) with respect to proliferation and vascularization [46]. Nevertheless, the role of stem cells in burn wound healing is a dynamic field and still under extensive research.

Another area of particular interest in the field of burn wound healing is the chemical burns of the cornea. In the year 2000, Dua and Azuara-Blanco [47] used autologous limbal stem cells for ocular surface reconstruction of the contralateral eye. It resulted in the formation of a better corneal surface with significant improvement in the vision and symptoms of the patients [47]. Several other experiments and trials using limbal stem cells showed similar results in inducing improvement of corneal healing and decreased neovascularization in both human (adults and children) and animal subjects [4853]. In 2007, Oh et al. [54] studied the therapeutic effects of mesenchymal stem cells on corneas with chemical burns. They reported that mesenchymal stem cell media and mesenchymal stem cell culture media (without the stem cells) reduced the inflammation and promoted neovascularization of the corneas [54]. They were also found to reduce the infiltration of CD4 cells, as well as IL-6, IL-10, and TGF-B1 levels. It is to be noted that the direct application of the stem cells provided superior results in the healing process in comparison with the stem cell culture media [54]. Another study by Ye et al. [55] utilized cyclophosphamide to suppress inflammatory reactions and the release of bone marrow stem cells into circulation. In this study, rabbits were inflicted with corneal alkali injuries. It was found that rabbits with an unsuppressed bone marrow had significantly greater reepithelialization of the corneas with clearer surfaces [55]. Thus, this study revealed the role of bone marrow cells in enhancing the healing of corneal chemical wounds. Furthermore, Sel et al. [56] inflicted alkali wounds on the corneal surfaces of mice and treated the corneas with bone marrow derived stem cells, CD117+ cells, or medium only as control. Reepithelialization of the wounds in the treatment groups was significantly faster than the control, with no difference in corneal transparency. Stem cells and CD117+ cells were absent from corneas after healing, thus suggesting that soluble factors may be responsible for the effect of the applied cells [56]. In a different study by Rama et al. [57], limbal stem cells were cultured on fibrin and used in corneal burns; not only did stem cells promote a better healing but also they had maintained a superior healing at a follow-up of 10 years later. Several other studies showed comparable results where mesenchymal derived or adipose derived stem cells promoted faster recovery of the corneal epithelium and decreased neovascularization, inflammation, and oxidative injury; moreover, stem cells stimulated the formation of clearer cornea media in some experiments [5861]. Additionally, Basu et al. [6264], in 2011 and 2012, reported a series of studies concerning the use of limbal stem cells in corneal burn wound healing. In the first study, Basu et al. [62] used limbal stem cells in corneal burn wound healing and followed them by penetrating keratoplasty procedures. Good results were observed but they were not compared to controls. However, in the second study, Basu et al. [63] observed that 66% of patients who failed primary procedures of corneal repair and who were subjected to a secondary limbal stem cell transplant on the affected cornea had successful improvement of the corneal surface with no neovascularization at a follow-up of two years. Later on, Sangwan et al. [64] used limbal biopsies from unaffected eyes and cultured them on amniotic membranes as substrates. Similar results to previous experiments were obtained with avascular epithelialization of the new corneal surfaces [64]. Furthermore and as demonstrated by Huang et al. [65], the use of allograft transplants of limbal stem cells in corneal burn wound healing also resulted in improved avascular corneal healing without the need for systemic immunosuppression. Pellegrini et al. [66] studied the biological factors that affected the stem cells role in corneal burn wound healing; the accurate number of stem cells used expressing high levels of the p63 transcription factor was shown to have important influence.

Stem cells do seem to have a very promising role in the treatment of burn wounds; however, other therapies are being developed to improve the treatment. For example, Klinger et al. [67] used fat injections in severe burn wounds as a trial to improve burn wound healing in humans. They did get results showing scar improvement and enhancement of tissue regeneration, but their study was limited to a small population [67]. In other studies, Auxenfans et al. [68] investigated the role of keratinocytes in improving wound healing in burns. They reported that keratinocytes induced a more rapid burn wound healing [68]. On the other hand, stromal vascular fraction has been also shown to play a possible role in enhancing burn wound healing [69]. Atalay et al. used isolated stromal vascular fraction in burn wound healing. It stimulated an increase in vascular endothelial growth factor and reduced the inflammation with an improved fibroblastic activity [69]. Additionally, Hussein et al. [70] studied the effect of Botox injections on burn wounds healing and found that Botox increased fibroblasts, TGF-B, and TNF-alpha levels and decreased inflammation, thus improving burn wound healing. Another recent study by Zhang et al. [71] showed a beneficial effect of heat shock protein 90 alpha on burn wound healing. It promoted faster healing and less inflammation. In addition, several other studies have examined the effects of different factors and substances such as curcumin, mast cell chymase, and phenytoin with hypericin on burn wound healing with promising results and better wound healing [7274].

Stem cells are commonly derived either from bone marrow, umbilical cord, adipose tissue, or skin. Natesan et al. [75] have even used debrided skin from severe burns as a source of stem cells for wound healing and regeneration. Hence, the adipose tissue that is discarded from burn wound debridement may now be of use for better wound healing. In addition, Natesan et al. [76], in another study, used isolated stem cells from debrided skin with fibrin and collagen based scaffolds. The dermal equivalents, created in the study, decreased wound contraction leading to a better matrix deposition and epithelialization [76]. Along the same line, van der Veen et al. [77] isolated mesenchymal stem cells from excised burn wound eschar. These stem cells showed similar abilities to adipose derived stem cells in differentiating into osteocytes, chondroblasts, and adipocytes [77].

A relatively recent approach by Li et al. [78] studied the role of electric fields in the migration of stem cells. They proved that epithelial stem cells migrate to the cathode in an induced electric field, knowing that endogenous electric fields exist naturally in wounds [78]. The migration of the stem cells was found to be proportional to the strength of the electric field and its duration, with the involvement of epidermal growth factor receptor and mitogen activated protein kinase-PI3K [78]. Hence, in addition to the use of stem cells in burn wounds, electric fields can be applied to the wounds to better direct their migration [78].

The role of stem cells in wound healing has been shown to be performed through several pathways, such as JNK and ERK59, and with the involvement of different factors and mediators, such as KGF-1 and PDGF-BB [5, 8]. Additionally, this role could also be carried out by the released factors and not only by direct integration of the stem cells into the wound scaffold or matrix [6].

Stem cells in burn wound healing have been found to follow the same mechanisms. The increased levels of stem cells in burn wounds suggested a possible enhancing role in aiding in the healing process [9, 10, 12, 13]. However, a lack of consistency of the outcome was documented. Different experiments may have used different amounts of purified stem cells, or stem cells at different stages of replication or differentiation in vitro, leading to what may seem different results. In brief, this review depicted the improved healing with stem cells qualitatively rather than quantitatively. To really demonstrate the value of different stem cells in the process of burn wound healing, more studies need to be done under optimal and well controlled conditions, aiming to measure a quantifiable improvement. Additionally, the excess use of stem cells may lead to unwanted results, such as increased fibrosis and thicker healed epithelium. Whether the effect is observed as a result of direct stem cell proliferation, or other induced substances and cells, needs to be studied in the future. Moreover, the role of cytokines released by stem cells along with bioactive peptides such as thymosin 4 has been documented to mediate the beneficial effect of the stem cell application in burn wound healing. Further data refer the superior healing probably not to the direct integration of the stem cells into the wound [11, 13]. Acute wound fluids were also shown to have a role in promoting faster healing of burn wounds, similarly reinforcing the role of mediators released by stem cells. Additionally, human alpha defensin 5 and the CXCL12/CXCR4 pathway with its signal SDF-1a were found to be inducers of stem cells in burn wounds [16, 18, 20].

In addition, stem cells have been shown to decrease cell infiltration, wound contraction, fibrosis, scar progression, and inflammation of burn wounds. Moreover, they have been found to promote faster burn wound healing and angiogenesis along with better granulation and the formation of hair follicles and sebaceous glands [15, 2245]. The studies reviewed showed positive results in both animal experiments and human trials, both in partial and full thickness injury burns. In addition, different ways of stem cell application have been used ranging from using stem cell scaffolds to systemic and intradermal injection [23, 25, 32]. Furthermore, the sources of stem cells used are multiple. They are derived from bone marrow, dermis, adipose tissue, and umbilical cords, among others [22, 23, 33, 41]. Stem cells have proved to be efficient not only in skin burns but also in corneal chemical burns, thus increasing the multiplicity of their use [5461].

Patients with burn wounds, especially those severely injured, tend to have lower quality of life [79]. The injury they suffer is not only physical but also psychological, affecting their jobs and relations with other people, especially their families [80, 81]. With the advance of burn wound treatment with time, patients self-esteem and quality of life have been improving [82, 83]. The hope is that the use of stem cells will open up a new arena of possibilities to improve the wound healing in burn patients, allowing patients to have faster healing, better scars, and a higher quality of life.

Stem cells have attracted many controversial public opinions over time. Many people argue that embryonic stem cell harvesting would be done by killing embryos which would be unethical [84]. Others would argue that even if embryos are used for stem cell research, it is not wrong. However, the path that this may lead to would be wrong such as embryo production for research purposes [84]. The public view towards the therapeutic use of stem cells has become more tolerant over time [85]. The role of educating people about the colossal potential for the use of stem cell has thus proven beneficial. People are now more educated about the different sources of stem cells and have become supportive of their use [85]. Regarding the acceptance of stem cells as an efficient therapy for burn wound healing in specific, a study done by Clover et al. [86] showed a very positive opinion. The biggest majority of people were willing to accept autologous stem cells, though a big percentage was also welcoming the idea of using allogeneic stem cells. These percentages did not differ between the use of stem cells for burn wounds or for the treatment of other diseases such as diabetes or Parkinsons [86].

In brief, the use of stem cells in burn wound healing appears to be very promising. While most studies were performed on animals, the application to humans is yet at its start. Hence, what is needed is more studies. Additionally, the signaling pathways followed by stem cells involved in the burn wound healing along with their factors and signals constitute a very dynamic and promising research field.

The authors declare that there is no conflict of interests regarding the publication of this paper.

More:
The Use of Stem Cells in Burn Wound Healing: A Review - Hindawi

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have the potential to differentiate into various types of cells including skeletal muscle cells. The approach of converting ESCs/iPSCs into skeletal muscle cells offers hope for patients afflicted with the skeletal muscle diseases such as the Duchenne muscular dystrophy (DMD). Patient-derived iPSCs are an especially ideal cell source to obtain an unlimited number of myogenic cells that escape immune rejection after engraftment. Currently, there are several approaches to induce differentiation of ESCs and iPSCs to skeletal muscle. A key to the generation of skeletal muscle cells from ESCs/iPSCs is the mimicking of embryonic mesodermal induction followed by myogenic induction. Thus, current approaches of skeletal muscle cell induction of ESCs/iPSCs utilize techniques including overexpression of myogenic transcription factors such as MyoD or Pax3, using small molecules to induce mesodermal cells followed by myogenic progenitor cells, and utilizing epigenetic myogenic memory existing in muscle cell-derived iPSCs. This review summarizes the current methods used in myogenic differentiation and highlights areas of recent improvement.

Duchenne muscular dystrophy (DMD) is a genetic disease affecting approximately 1 in 3500 male live births [1]. It results in progressive degeneration of skeletal muscle causing complete paralysis, respiratory and cardiac complications, and ultimately death. Normal symptoms include the delay of motor milestones including the ability to sit and stand independently. DMD is caused by an absence of functional dystrophin protein and skeletal muscle stem cells, as well as the exhaustion of satellite cells following many rounds of muscle degeneration and regeneration [2]. The dystrophin gene is primarily responsible for connecting and maintaining the stability of the cytoskeleton of muscle fibers during contraction and relaxation. Despite the low frequency of occurrence, this disease is incurable and will cause debilitation of the muscle and eventual death in 20 to 30 year olds with recessive X-linked form of muscular dystrophy. Although there are no current treatments developed for DMD, there are several experimental therapies such as stem cell therapies.

Skeletal muscle is known to be a regenerative tissue in the body. This muscle regeneration is mediated by muscle satellite cells, a stem cell population for skeletal muscle [3, 4]. Although satellite cells exhibit some multipotential differentiation capabilities [5], their primary differentiation fate is skeletal muscle cells in normal muscle regeneration. Ex vivo expanded satellite cell-derived myoblasts can be integrated into muscle fibers following injection into damaged muscle, acting as a proof-of-concept of myoblast-mediated cell therapy for muscular dystrophies [69]. However, severe limitations exist in relation to human therapy. The number of available satellite cells or myoblasts from human biopsies is limited. In addition, the poor cell survival and low contribution of transplanted cells have hindered practical application in patients [6, 8, 9]. Human-induced pluripotent stem cells (hiPSCs) are adult cells that have been genetically reprogrammed to an embryonic stem cell- (ESC-) like state by being forced to express genes and factors important for maintaining the defining properties of ESCs. hiPSCs can be generated from a wide variety of somatic cells [10, 11]. They have the ability to self-renew and successfully turn into any type of cells. With their ability to capture genetic diversity of DMD in an accessible culture system, hiPSCs represent an attractive source for generating myogenic cells for drug screening.

The ESC/iPSC differentiation follows the steps of embryonic development. The origin of skeletal muscle precursor cells comes from the mesodermal lineage, which give rise to skeletal muscle, cardiac muscle, bone, and blood cells. Mesoderm subsequently undergoes unsegmented presomitic mesoderm followed by segmented compartments termed somites from anterior to caudal direction. Dermomyotome is an epithelial cell layer making up the dorsal part of the somite underneath the ectoderm. Dermomyotome expresses Pax3 and Pax7 and gives rise to dermis, skeletal muscle cells, endothelial cells, and vascular smooth muscle [12]. Dermomyotome also serves as a tissue for secreted signaling molecules to the neural tube, notochord, and sclerotome [13, 14]. Upon signals from the neural tube and notochord, the dorsomedial lip of dermomyotome initiates and expresses skeletal muscle-specific transcription factors such as MyoD and Myf5 to differentiate into myogenic cells termed myoblasts. Myoblasts then migrate beneath the dermomyotome to form myotome. Eventually, these myoblasts fuse with each other to form embryonic muscle fibers. ESCs/iPSCs mimic these steps toward differentiation of skeletal muscle cells. Many studies utilize methods of overexpression of muscle-related transcription factors such as MyoD or Pax3 [15], or the addition of small molecules which activate or inhibit myogenic signaling during development. Several studies show that iPSCs retain a bias to form their cell type of origin due to an epigenetic memory [1619], although other papers indicate that such epigenetic memory is erased during the reprogramming processes [2022]. Therefore, this phenomenon is not completely understood at the moment. In light of these developments, we have recently established mouse myoblast-derived iPSCs capable of unlimited expansion [23]. Our data demonstrates that these iPSCs show higher myogenic differentiation potential compared to fibroblast-derived iPSCs. Thus, myogenic precursor cells generated from human myoblast-derived iPSCs expanded ex vivo should provide an attractive cell source for DMD therapy. However, since DMD is a systemic muscle disease, systemic delivery of myoblasts needs to be established for efficient cell-based therapy.

During developmental myogenesis, presomitic mesoderm is first formed by Mesogenin1 upregulation, which is a master regulator of presomitic mesoderm [24]. Then, the paired box transcription factor Pax3 gene begins to be expressed from presomitic mesoderm to dermomyotome [25]. Following Pax3 expression, Pax7 is also expressed in the dermomyotome [26], and then Myf5 and MyoD, skeletal muscle-specific transcription factor genes, begin to be expressed in the dorsomedial lip of the dermomyotome in order to give rise to myoblasts which migrate beneath the dermomyotome to form the myotome. Subsequently, Mrf4 and Myogenin, other skeletal muscle-specific transcription factor genes, followed by skeletal muscle structural genes such as myosin heavy chain (MyHC), are expressed in the myotome for myogenic terminal differentiation (Figure 1) [27, 28]. Pax3 directly and indirectly regulates Myf5 expression in order to induce myotomal cells. Dorsal neural tube-derived Wnt proteins and floor plate cells in neural tube and notochord-derived sonic hedgehog (Shh) positively regulate myotome formation [13, 29]. Neural crest cells migrating from dorsal neural tubes are also involved in myotome formation: Migrating neural crest cells come across the dorsomedial lip of the dermomyotome, and neural crest cell-expressing Delta1 is transiently able to activate Notch1 in the dermomyotome, resulting in conversion of Pax3/7(+) myogenic progenitor cells into MyoD/Myf5(+) myotomal myoblasts [30, 31]. By contrast, bone morphogenetic proteins (BMPs) secreted from lateral plate mesoderm are a negative regulator for the myotome formation by maintaining Pax3/Pax7(+) myogenic progenitor cells [29, 32]. Pax3 also regulates cell migration of myogenic progenitor cells from ventrolateral lip of dermomyotome to the limb bud [33]. Pax3 mutant mice lack limb muscle but trunk muscle development is relatively normal [34]. Pax3/Pax7 double knockout mice display failed generation of myogenic cells, suggesting that Pax3 and Pax7 are critical for proper embryonic myogenesis [35]. Therefore, both Pax3 and Pax7 are also considered master transcription factors for the specification of myogenic progenitor cells. Importantly, MyoD was identified as the first master transcription factor for myogenic specification since MyoD is directly able to reprogram nonmuscle cell type to myogenic lineage when overexpressed [3638]. In addition, genetic ablation of MyoD family gene(s) via a homologous gene recombination technique causes severe myogenic developmental or regeneration defects [3945]. Finally, genetic ablation of combinatory MyoD family genes demonstrates that MyoD/:Myf5/:MRF4/ mice do not form any skeletal muscle during embryogenesis, indicating the essential roles in skeletal muscle development of MyoD family genes [28, 46]. It was proven that Pax3 also possesses myogenic specification capability since ectopic expression of Pax3 is sufficient to induce myogenic programs in both paraxial and lateral plate mesoderm as well as in the neural tube during chicken embryogenesis [47]. In addition, genetic ablation of Pax3 and Myf5 display complete defects of body skeletal muscle formation during mouse embryogenesis [48]. Finally, overexpression of Pax7 can convert CD45(+)Sca-1(+) hematopoietic cells into skeletal muscle cells [49]. From these notions, overexpression of myogenic master transcription factors such as MyoD or Pax3 has become the major strategy for myogenic induction in nonmuscle cells, including ES/iPSCs.

The overexpression of MyoD approach to induce myogenic cells from mESCs was first described by Dekel et al. in 1992. This has been a standard approach for the myogenic induction from pluripotent stem cells (Table 1). Ozasa et al. first utilized Tet-Off systems for MyoD overexpression in mESCs and showed desmin(+) and MyHC(+) myotubes in vitro [50]. Warren et al. transfected synthetic MyoD mRNA in to hiPSCs for 3 days, which resulted in myogenic differentiation (around 40%) with expression of myogenin and MyHC [51]. Tanaka et al. utilized a PiggyBac transposon system to overexpress MyoD in hiPSCs. The PiggyBac transposon system allows cDNAs to stably integrate into the genome for efficient gene expression. After integration, around 70 to 90% of myogenic cells were induced in hiPSC cultures within 5 days [52]. This study also utilized Miyoshi myopathy patient-derived hiPSCs for the MyoD-mediated myogenic differentiation. Miyoshi myopathy is a congenital distal myopathy caused by defective muscle membrane repair due to mutations in dysferlin gene. The patient-derived hiPSC-myogenic cells will be able to provide the opportunity for therapeutic drug screening. Abujarour et al. also established a model of patient-derived skeletal muscle cells which express NCAM, myogenin, and MyHC by doxycycline-inducible overexpression of MyoD in DMD patient-derived hiPSCs [53]. Interestingly, MyoD-induced iPSCs also showed suppression of pluripotent genes such as Nanog and a transient increase in the gene expression levels of T (Brachyury T), Pax3, and Pax7, which belong to paraxial mesodermal/myogenic progenitor genes, upstream genes of myogenesis. It is possible that low levels of MyoD activity in hiPSCs may initially suppress their pluripotent state while failing to induce myogenic programs, which may result in transient paraxial mesodermal induction. Supporting this idea, BAF60C, a SWI/SNF component that is involved in chromatin remodeling and binds to MyoD, is required to induce full myogenic program in MyoD-overexpressing hESCs [54]. Overexpression of MyoD alone in hESC can only induce some paraxial mesodermal genes such as Brachyury T, mesogenin, and Mesp1 but not myogenic genes. Co-overexpression of MyoD and BAF60C was now able to induce myogenic program but not paraxial mesodermal gene expression, indicating that there are different epigenetic landscapes between pluripotent ESCs/iPSCs and differentiating ESC/iPSCs in which MyoD is more accessible to DNA targets than those in pluripotent cells. The authors then argued that without specific chromatin modifiers, only committed cells give rise to myogenic cells by MyoD. These results strongly indicate that nuclear landscapes are important for cell homogeneity for the specific cell differentiation in ESC/iPSC cultures. Similar observations were seen in overexpression of MyoD in P19 embryonal carcinoma stem cells, which can induce paraxial mesodermal genes including Meox1, Pax3, Pax7, Six1, and Eya2 followed by muscle-specific genes. However, these MyoD-induced paraxial mesodermal genes were mediated by direct MyoD binding to their regulatory regions, which was proven by chromatin immunoprecipitation (ChIP) assays, indicating the novel role for MyoD in paraxial mesodermal cell induction [55].

hESCs/iPSCs have been differentiated into myofibers by overexpression of MyoD, and this method is considered an excellent in vitro model for human skeletal muscle diseases for muscle functional tests, therapeutic drug screening, and genetic corrections such as exon skipping and DNA editing. Shoji et al. have shown that DMD patient-derived iPSCs were used for myogenic differentiation via PiggyBac-mediated MyoD overexpression. These myogenic cells were treated with morpholinos for exon-skipping strategies for dystrophin gene correction and showed muscle functional improvement [56]. Li et al. have shown that patient-derived hiPSC gene correction by TALEN and CRISPR-Cas9 systems, and these genetically corrected hiPSCs were used for myogenic differentiation via overexpression of MyoD [57]. This work also revealed that the TALEN and CRISPR-Cas9-mediated exon 44 knock-in approach in the dystrophin gene has high efficiency in gene-editing methods for DMD patient-derived cells in which the exon 44 is missing in the genome.

Along this line of the strategy, Darabi et al. first performed overexpression of Pax3 gene, which can be activated by treatment with doxycycline in mESCs, and showed efficient induction of MyoD/Myf5(+) skeletal myoblasts in EB cultures [15]. Upon removing doxycycline, these myogenic cells underwent MyHC(+) myotubes. However, teratoma formation was observed after EB cell transplantation into cardiotoxin-injured regenerating skeletal muscle in Rag2/:C/ immunodeficient mice [15]. This indicates that myogenic cell cultures induced by Pax3 in mESCs still contain some undifferentiated cells which gave rise to teratomas. To overcome this problem, the same authors separated paraxial mesodermal cells from Pax3-induced EB cells by FACS using antibodies against cell surface markers as PDGFR(+)Flk-1() cell populations. After cell sorting, isolated Pax3-induced paraxial mesodermal cells were successfully engrafted and contributed to regenerating muscle in mdx:Rag2/:C/ DMD model immunodeficient mice without any teratoma formations. Darabi et al. also showed successful myogenic induction in mESCs and hES/iPSCs by overexpression of Pax7 [58, 59]. Pax3 and Pax7 are not only expressed in myogenic progenitor cells. They are also expressed in neural tube and neural crest cell-derived cells including a part of cardiac cell types in developmental stage, suggesting that further purification to skeletal muscle cell lineage is crucial for therapeutic applications for muscle diseases including DMD.

Taken together, overexpression of myogenic master transcription factors such as MyoD or Pax3/Pax7 is an excellent strategy for myogenic induction in hESCs and hiPSCs, which can be utilized for in vitro muscle disease models for their functional test and drug screening. However, for the safe stem cell therapy, it is essential to maintain the good cellular and genetic qualities of hESC/hiPSC-derived myogenic cells before transplantation. Therefore, random integration sites of overexpression vectors for myogenic master transcription factors and inappropriate expression control of these transgenes may diminish the safety of using these induced myogenic cells for therapeutic stem cell transplantation.

Stepwise induction protocols utilizing small molecules and growth factors have been established as alternative myogenic induction approaches and a more applicable method for therapeutic situations. As described above, during embryonic myogenesis, somites and dermomyotomes receive secreted signals such as Wnts, Notch ligands, Shh, FGF, BMP, and retinoic acid (RA) with morphogen gradients from surrounding tissues in order to induce the formation of myogenic cells (Figure 2). The canonical Wnt signaling pathway has been shown to play essential roles in the development of myogenesis. In mouse embryogenesis, Wnt1 and Wnt3a secreted from the dorsal neural tube can promote myogenic differentiation of dorsomedial dermomyotome via activation of Myf5 [31, 32, 60]. Wnt3a is able to stabilize -catenin which associates with TCF/LEF transcription factors that bind to the enhancer region of Myf5 during myogenesis [61]. Other Wnt proteins, Wnt6 and Wnt7a, which emerge from the surface ectoderm, induce MyoD [62]. BMP functions as an inhibitor of myogenesis by suppression of some myogenic gene expressions. In the lateral mesoderm, BMP4 is able to increase Pax3 expression which delays Myf5 expression in order to maintain an undifferentiated myogenic progenitor state [63]. Therefore, Wnts and BMPs regulate myogenic development by antagonizing each other for myogenic transcription factor gene expression [64, 65]. Wnt also induces Noggin expression to antagonize BMP signals in the dorsomedial lip of the dermomyotome [66]. In this region, MyoD expression level is increased, which causes myotome formation. Notch signaling plays essential roles for cell-cell communication to specify the different cells in developmental stages. During myotome formation, Notch is expressed in dermomyotome, and Notch1 and Notch2 are expressed in dorsomedial lip of dermomyotome. Delta1, a Notch ligand, is expressed in neural crest cells which transiently interact with myogenic progenitor cells in dorsomedial lip of dermomyotome via Notch1 and 2. This contact induces expression of the Myf5 or MyoD gene in the myogenic progenitor cells followed by myotome formation. The loss of function of Delta1 in the neural crest displays delaying skeletal muscle formation [67]. Knockdown of Notch genes or use of a dominant-negative form of mastermind, a Notch transcriptional coactivator, clearly shows dramatically decrease of Myf5 and MyHC(+) myogenic cells. Interestingly, induction of Notch intracellular domain (NICD), a constitutive active form of Notch, can promote myogenesis, while continuous expression of NICD prevents terminal differentiation. Taken together, transient and timely activation of Notch is crucial for myotome formation from dermomyotome [30].

Current studies for myogenic differentiation of ESCs/iPSCs have utilized supplementation with some growth factors and small molecules, which would mimic the myogenic development described above in combination with embryoid body (EB) aggregation and FACS separation of mesodermal cells (Table 2). To induce paraxial mesoderm cells from mESCs, Sakurai et al. utilized BMP4 in serum-free cultures [68]. Three days after treatment with BMP4, mESCs could be differentiated into primitive streak mesodermal-like cells, but the continuous treatment with BMP4 turned the ESCs into osteogenic cells. Therefore, they used LiCl after treatment with BMP4 to enhance Wnt signaling, which is able to induce myogenic differentiation. After treatment with LiCl, PDGFR(+) E-cadherin() paraxial mesodermal cells were sorted by FACS. These sorted cells were cultured with IGF, HGF, and FGF for two weeks in order to induce myogenic differentiation. Hwang et al. have shown that treatment with Wnt3a efficiently promotes skeletal muscle differentiation of hESCs [69]. hESCs were cultured to form EB for 9 days followed by differentiation of EBs for additional 7 days, and then PDGFR(+) cells were sorted by FACS. These PDGFR(+) cells were cultured with Wnt3a for additional 14 days. Consequently, these Wnt3a-treated cells display significantly increased myogenic transcription factors and structural proteins at both mRNA and protein levels. An interesting approach to identify key molecules that induce myogenic cells was reported by Xu et al. [70]. They utilized reporter systems in zebrafish embryos to display myogenic progenitor cell induction and myogenic differentiation in order to identify small compounds for myogenic induction. Myf5-GFP marks myogenic progenitor cells, while myosin light polypeptide 2 (mylz2)-mCherry marks terminally differentiated muscle cells. They found that a mixed cocktail containing GSK3 inhibitor, bFGF, and forskolin has the potential to induce robust myogenic induction in hiPSCs. GSK3 inhibitors act as a canonical Wnt signaling activator via stabilizing -catenin protein, which is crucial for inducing mesodermal cells. Forskolin activates adenylyl cyclase, which then stimulates cAMP signaling. cAMP response element-binding protein (CREB) is able to stimulate cell proliferation of primary myoblasts in vitro, suggesting that the forskolin-cAMP-CREB pathway may help myogenic cell expansion [71], However the precise mechanisms for CREB-mediated myogenic cell expansion remain unclear. The adenylyl cyclase signaling cascade leads to CREB activation [71]. During embryogenesis, phosphorylated CREB has been found at dorsal somite and dermomyotome. CREB gene knockout mice display significantly decreased Myf5 and MyoD expressions in myotomes. While activation of Wnt1 or Wnt7a promotes Pax3, Myf5, and MyoD expressions, inhibition of CREB eliminates these Wnt-mediated myogenic gene expressions without altering the Wnt canonical pathway, suggesting that CREB-induced myogenic activation may be mediated through noncanonical Wnt pathways. Several groups also utilized GSK3 inhibitors for inducing mesodermal cells from ESCs and iPSCs [72, 73]. These mesodermal cell-like cells were expanded by treatment with bFGF, and then ITS (insulin/transferrin/selenite) or N2 medium were used to induce myogenic differentiation. Finally, bFGF is a stimulator for myogenic cell proliferation. Caron et al. demonstrated that hESCs treated with GSK3 inhibitor, ascorbic acid, Alk5 inhibitor, dexamethasone, EGF, and insulin generated around 80% of Pax3(+) myogenic precursor cells in 10 days [74]. Treatment with SB431542, an inhibitor of Alk4, 5, and 7, PDGF, bFGF, oncostatin, and IGF was able to induce these Pax3(+) myogenic precursor cells into around 5060% of MyoD(+) myoblasts in an additional 8 days. For the final step, treatment with insulin, necrosulfonamide, an inhibitor of necrosis, oncostatin, and ascorbic acid was able to induce these myoblasts into myotubes in an additional 8 days. Importantly, the same authors utilized ESCs from human facioscapulohumeral muscular dystrophy (FSHD) to demonstrate the myogenic characterization after myogenic induction by using the protocol described above. Hosoyama et al. have shown that hESCs/iPSCs with high concentrations of bFGF and EGF in combination with cell aggregation, termed EZ spheres, efficiently give rise to myogenic cells [75]. After 6-week culture, around 4050% of cells expressed Pax7, MyoD, or myogenin. However, the authors also showed that EZ spheres included around 30% of Tuj1(+) neural cells. Therefore, the authors discussed the utilization of molecules for activation of mesodermal and myogenic signaling pathways such as BMPs and Wnts.

Taken together, it is likely that the induced cell populations from ESCs/iPSCs may contain other cell types such as neural cells or cardiac cells because neural cells share similar transcription factor gene expression with myogenic cells such as Pax3, and cardiac cells also develop from mesodermal cells. To overcome this limitation, Chal et al. treated ESCs/iPSCs with BMP4 inhibitor, which prevents ESCs/iPSCs from differentiating into lateral mesodermal cells [76, 77]. To identify what genes are involved in myogenic differentiation in vivo, they performed a microarray analysis which compared samples of dissected fragments in mouse embryos, which are able to separate tail bud, presomitic mesoderm, and somite regions. From microarray data, the authors focused on Mesogenin1 (Msgn1) and Pax3 genes. Importantly, they utilized three lineage tracing reporters, Msgn1-repV (Mesogenin1-Venus) marking posterior somitic mesoderm, Pax3-GFP marking anterior somitic mesoderm and myogenic cells, and Myog-repV (Myogenin-Venus) marking differentiated myocytes, allowing the authors to readily detect different differentiation stages during ESC/iPSC cultures. Treatment with GSK3 inhibitors and then BMP inhibitors in ESC cultures induced Msgn1(+) somitic mesoderm with 45 to 65% efficiencies, Pax3(+) anterior somitic mesoderm with 30 to 50% efficiencies, and myogenin(+) myogenic cells with 25 to 30% efficiencies. Furthermore, the authors examined differentiation of mdx ESCs into skeletal muscle cells and revealed abnormal branching myofibers. Current protocols were also published and described more details for hiPSC differentiation [77].

Some nonmuscle cell populations such as mesoangioblasts have the potential to differentiate into skeletal muscle [6]. Mesoangioblasts were originally isolated from embryonic mouse dorsal aorta as vessel-associated pericyte-like cells, which have the ability to differentiate into a myogenic lineage in vitro and in vivo [6, 78]. Mesoangioblasts possess an advantage for the clinical cell-based treatment because they can be injected through an intra-arterial route to systemically deliver cells, which is crucial for therapeutic cell transplantation for muscular dystrophies [79]. Tedesco et al. successfully generated human iPSC-derived mesoangioblast-like stem/progenitor cells called HIDEMs by stepwise protocols without FACS sorting [80, 81]. They displayed similar gene expression profiles as embryonic mesoangioblasts. However, HIDEMs do not spontaneously differentiate into skeletal muscle cells, and thus, the authors utilized overexpression of MyoD to differentiate into skeletal muscle cells. Similar to mesoangioblasts, HIDEM-derived myogenic cells could be delivered to injured muscle via intramuscular and intra-arterial routes. Furthermore, HIDEMs have been generated from hiPSCs derived from limb-girdle muscular dystrophy (LGMD) type 2D patients and used for gene correction and cell transplantation experiments for the potential therapeutic application.

Myogenic precursor cells derived from ESCs/iPSCs by various methods may contain nonmuscle cells. Therefore, further purification is mandatory for therapeutic applications. Barberi et al. isolated CD73(+) multipotent mesenchymal precursor cells from hESCs by FACS, and these cells underwent differentiation into fat, cartilage, bone, and skeletal muscle cells [82]. Barberi et al. also demonstrated that hESCs cultured on OP9 stroma cells generated around 5% of CD73(+) adult mesenchymal stem cell-like cells [83]. After FACS, these CD73(+) mesenchymal stem cell-like cells were cultured with ITS medium for 4 weeks and then gave rise to NCAM(+) myogenic cells. After FACS sorting, these NCAM(+) myogenic cells were purified by FACS and transplanted into immunodeficient mice to show their myogenic contribution to regenerating muscle.

It has been shown that many genes are associated with myogenesis. In addition, exhaustive analysis, such as microarray, RNA-seq, and single cell RNA-seq supplies much gene information in many different stages. Chal et al. showed key signaling factors by microarray from presomitic somite, somite, and tail bud cells [76]. They found that initial Wnt signaling has important roles for somite differentiation. Furthermore, mapping differentiated hESCs by single cell RNA-seq analysis is useful to characterize each differentiated stage [84].

As shown above, cell sorting of mesodermal progenitor cells, mesenchymal precursor cells, or myogenic cells is a powerful tool to obtain pure myogenic populations from differentiated pluripotent cells. Sakurai et al. have been able to induce PDGFR(+)Flk-1() mesodermal progenitor cells by FACS followed by myogenic differentiation [85]. Chang et al. and Mizuno et al. have been able to sort SMC-2.6(+) myogenic cells from mouse ESCs/iPSCs [86, 87]. These SMC-2.6(+) myogenic cells were successfully engrafted into mouse regenerating skeletal muscle. However, this SMC-2.6 antibody only recognizes mouse myogenic cells but not human myogenic cells [86, 88]. Therefore, Borchin et al. have shown that hiPSC-derived myogenic cells differentiated into c-met(+)CXCR4(+)ACHR(+) cells, displaying that over 95% of sorted cells are Pax7(+) myogenic cells [72]. Taken together, current myogenic induction protocols utilizing small molecules and growth factors, with or without myogenic transcription factors, have been largely improved in the last 5 years. It is crucial to standardize the induction protocols in the near future to obtain sufficient myogenic cell conversion from pluripotent stem cells.

Recent work demonstrated that cells inherit a stable genetic program partly through various epigenetic marks, such as DNA methylation and histone modifications. This cellular memory needs to be erased during genetic reprogramming, and the cellular program reverted to that of an earlier developmental stage [16, 22, 89]. However, iPSCs retaining an epigenetic memory of their origin can readily differentiate into their original tissues [1619, 90100]. This phenomenon becomes a double-edged sword for the reprogramming process since the retention of epigenetic memory may reduce the quality of pluripotency while increasing the differentiation efficiency into their original tissues. DNA methylation levels are relatively low in the pluripotent stem cells compared to the high levels of DNA methylation seen in somatic cells [101]. Global DNA demethylation is required for the reprogramming process [102]. In the context of these observations, recent work demonstrates that activation-induced cytidine deaminase AID/AICDA contributing to the DNA demethylation can stabilize stem-cell phenotypes by removing epigenetic memory of pluripotent genes. This directly deaminates 5-methylcytosine in concert with base-excision repair to exchange cytosine in genomic DNA [103]. MicroRNA-155 has been identified as a key player for the retention of epigenetic memory during in vitro differentiation of hematopoietic progenitor cell-derived iPSCs toward hematopoietic progenitors [104]. iPSCs that maintained high levels of miR-155 expression tend to differentiate into the original somatic population more efficiently.

Recently, we generated murine skeletal muscle cell-derived iPSCs (myoblast-derived iPSCs) [23] and compared the efficiency of differentiation of myogenic progenitor cells between myoblast-derived iPSCs and fibroblast-derived iPSCs. After EB cultures, more satellite cell/myogenic progenitor cell differentiation occurred in myoblast-derived iPSCs than that in fibroblast-derived-iPSCs (unpublished observation and Figure 3), suggesting that myoblast-derived iPSCs are potential myogenic and satellite cell sources for DMD and other muscular dystrophy therapies (Figure 4). We also noticed that MyoD gene suppression by Oct4 is required for reprogramming in myoblasts to produce iPSCs (Figure 3) [23]. During overexpression of Oct4, Oct4 first binds to the Oct4 consensus sequence located in two MyoD enhancers (a core enhancer and distal regulatory region) [105107] preceding occupancy at the promoter in myoblasts in order to suppress MyoD gene expression. Interestingly, Oct4 binding to the MyoD core enhancer allows for establishment of a bivalent state in MyoD promoter as a poised state, marked by active (H3K4me3) and repressive (H3K27me3) modifications in fibroblasts, one of the characteristics of stem cells (Figure 3) [23, 108]. It should be investigated whether the similar bivalent state is also established in Oct4-expressing myoblasts during reprogramming process from myoblasts to pluripotent stem cells. It remains to be elucidated whether Oct4-mediated myogenic repression only relies on repression of MyoD expression or is just a general phenomenon of functional antagonism between Oct4 and MyoD on activation of muscle genes. Nevertheless, myoblast-derived iPSCs will enable us to produce an unlimited number of myogenic cells, including satellite cells that could form the basis of novel treatments for DMD and other muscular dystrophies (Figure 4).

There are pros and cons of transgene-free small molecule-mediated myogenic induction protocols. In the transgene-mediated induction protocols, integration of the transgene in the host genome may lead to risk for insertional mutagenesis. To circumvent this issue, there is an obvious advantage for transgene-free induction protocols. Some key molecules such as Wnt, FGF, and BMP have used signaling pathways to induce myogenic differentiation of ES/iPSCs. However, these molecules are also involved in induction of other types of cell lineages, which makes it difficult for ES/iPSCs to induce pure myogenic cell populations in vitro. By contrast, transgene-mediated myogenic induction is able to dictate desired specific cell lineages. In any case, it is necessary to intensively investigate these myogenic induction protocols for the efficient and safe stem cell therapy for patients.

For skeletal muscle diseases, patient-derived hiPSCs, which possess the ability to differentiate into myogenic progenitor cells followed by myotubes, can be a useful tool for drug screening and personalized medicine in clinical practice. However, there are still limitations for utilizing hiPSC-derived myogenic cells for regenerative medicine. For cell-based transplantation therapies such as a clinical situation, animal-free defined medium is essential for stem cell culture and skeletal muscle cell differentiation. Therefore, such animal-free defined medium needs to be established for optimal myogenic differentiation from hiPSCs. Gene correction in DMD patient iPSCs by TALENs and CRISPR-Cas9 systems are promising therapeutic approaches for stem cell transplantation. However, there are still problems for DNA-editing-mediated stem cell therapy such as safety and efficacy. Since iPSC-derived differentiated myotubes do not proliferate, they are not suited for cell transplantation. Therefore, a proper culture method needs to be established for hiPSCs in order to maintain cells in proliferating the myogenic precursor cell stage in vitro in order to expand cells to large quantities of transplantable cells for DMD and other muscular dystrophies. For other issues, it is essential to establish methods to separate ES/iPSC-derived pure skeletal muscle precursor cells from other cell types for safe stem cell therapy that excludes tumorigenic risks of contamination with undifferentiated cells. In the near future, these obstacles will be taken away for more efficient and safe stem cell therapy for DMD and other muscular dystrophies.

The authors declare that they have no conflicts of interest.

This work was supported by the NIH R01 (1R01AR062142) and NIH R21 (1R21AR070319). The authors thank Conor Burke-Smith and Neeladri Chowdhury for critical reading.

The rest is here:
Skeletal Muscle Cell Induction from Pluripotent Stem Cells

Specific location in the body containing stem cells

Stem-cell niche refers to a microenvironment, within the specific anatomic location where stem cells are found, which interacts with stem cells to regulate cell fate.[1] The word 'niche' can be in reference to the in vivo or in vitro stem-cell microenvironment. During embryonic development, various niche factors act on embryonic stem cells to alter gene expression, and induce their proliferation or differentiation for the development of the fetus. Within the human body, stem-cell niches maintain adult stem cells in a quiescent state, but after tissue injury, the surrounding micro-environment actively signals to stem cells to promote either self-renewal or differentiation to form new tissues. Several factors are important to regulate stem-cell characteristics within the niche: cellcell interactions between stem cells, as well as interactions between stem cells and neighbouring differentiated cells, interactions between stem cells and adhesion molecules, extracellular matrix components, the oxygen tension, growth factors, cytokines, and the physicochemical nature of the environment including the pH, ionic strength (e.g. Ca2+ concentration) and metabolites, like ATP, are also important.[2] The stem cells and niche may induce each other during development and reciprocally signal to maintain each other during adulthood.

Scientists are studying the various components of the niche and trying to replicate the in vivo niche conditions in vitro.[2] This is because for regenerative therapies, cell proliferation and differentiation must be controlled in flasks or plates, so that sufficient quantity of the proper cell type are produced prior to being introduced back into the patient for therapy.

Human embryonic stem cells are often grown in fibroblastic growth factor-2 containing, fetal bovine serum supplemented media. They are grown on a feeder layer of cells, which is believed to be supportive in maintaining the pluripotent characteristics of embryonic stem cells. However, even these conditions may not truly mimic in vivo niche conditions.

Adult stem cells remain in an undifferentiated state throughout adult life. However, when they are cultured in vitro, they often undergo an 'aging' process in which their morphology is changed and their proliferative capacity is decreased. It is believed that correct culturing conditions of adult stem cells needs to be improved so that adult stem cells can maintain their stemness over time.[citation needed]

A Nature Insight review defines niche as follows:

"Stem-cell populations are established in 'niches' specific anatomic locations that regulate how they participate in tissue generation, maintenance and repair. The niche saves stem cells from depletion, while protecting the host from over-exuberant stem-cell proliferation. It constitutes a basic unit of tissue physiology, integrating signals that mediate the balanced response of stem cells to the needs of organisms. Yet the niche may also induce pathologies by imposing aberrant function on stem cells or other targets. The interplay between stem cells and their niche creates the dynamic system necessary for sustaining tissues, and for the ultimate design of stem-cell therapeutics ... The simple location of stem cells is not sufficient to define a niche. The niche must have both anatomic and functional dimensions."[3]

Though the concept of stem cell niche was prevailing in vertebrates, the first characterization of stem cell niche in vivo was worked out in Drosophila germinal development.

By continuous intravital imaging in mice, researchers were able to explore the structure of the stem cell niche and to obtain the fate of individual stem cells (SCs) and their progeny over time in vivo. In particular in intestinal crypt,[4] two distinct groups of SCs have been identified: the "border stem cells" located in the upper part of the niche at the interface with transit amplifying cells (TAs), and "central stem cells" located at the crypt base. The proliferative potential of the two groups was unequal and correlated with the cells' location (central or border). It was also shown that the two SC compartments acted in accord to maintain a constant cell population and a steady cellular turnover. A similar dependence of self-renewal potential on proximity to the niche border was reported in the context of hair follicle, in an in vivo live-imaging study.[5]

This bi-compartmental structure of stem cell niche has been mathematically modeled to obtain the optimal architecture that leads to the maximum delay in double-hit mutant production.[6] They found that the bi-compartmental SC architecture minimizes the rate of two-hit mutant production compared to the single SC compartment model. Moreover, the minimum probability of double-hit mutant generation corresponds to purely symmetric division of SCs with a large proliferation rate of border stem cells along with a small, but non-zero, proliferation rate of central stem cells.[citation needed]

Stem cell niches harboring continuously dividing cells, such as those located at the base of the intestinal gland, are maintained at small population size. This presents a challenge to the maintenance of multicellular tissues, as small populations of asexually dividing individuals will accumulate deleterious mutations through genetic drift and succumb to mutational meltdown.[7] Mathematical modeling of the intestinal gland reveals that the small population size within the stem cell niche minimizes the probability of carcinogenesis occurring anywhere, at the expense of gradually accumulated deleterious mutations throughout organismal lifetimea process that contributes to tissue degradation and aging.[8] Therefore, the population size of the stem cell niche represents an evolutionary trade-off between the probability of cancer formation and the rate of aging.

Germline stem cells (GSCs) are found in organisms that continuously produce sperm and eggs until they are sterile. These specialized stem cells reside in the GSC niche, the initial site for gamete production, which is composed of the GSCs, somatic stem cells, and other somatic cells. In particular, the GSC niche is well studied in the genetic model organism Drosophila melanogaster and has provided an extensive understanding of the molecular basis of stem cell regulation.[citation needed]

In Drosophila melanogaster, the GSC niche resides in the anterior-most region of each ovariole, known as the germarium. The GSC niche consists of necessary somatic cells-terminal filament cells, cap cells, escort cells, and other stem cells which function to maintain the GSCs.[9] The GSC niche holds on average 23 GSCs, which are directly attached to somatic cap cells and Escort stem cells, which send maintenance signals directly to the GSCs.[10] GSCs are easily identified through histological staining against vasa protein (to identify germ cells) and 1B1 protein (to outline cell structures and a germline specific fusome structure). Their physical attachment to the cap cells is necessary for their maintenance and activity.[10] A GSC will divide asymmetrically to produce one daughter cystoblast, which then undergoes 4 rounds of incomplete mitosis as it progresses down the ovariole (through the process of oogenesis) eventually emerging as a mature egg chamber; the fusome found in the GSCs functions in cyst formation and may regulate asymmetrical cell divisions of the GSCs.[11] Because of the abundant genetic tools available for use in Drosophila melanogaster and the ease of detecting GSCs through histological stainings, researchers have uncovered several molecular pathways controlling GSC maintenance and activity.[12] [13]

The Bone Morphogenetic Protein (BMP) ligands Decapentaplegic (Dpp) and Glass-bottom-boat (Gbb) ligand are directly signalled to the GSCs, and are essential for GSC maintenance and self-renewal.[14] BMP signalling in the niche functions to directly repress expression of Bag-of-marbles (Bam) in GSCs, which is up-regulated in developing cystoblast cells.[15] Loss of function of dpp in the niche results in de-repression of Bam in GSCs, resulting in rapid differentiation of the GSCs.[10] Along with BMP signalling, cap cells also signal other molecules to GSCs: Yb and Piwi. Both of these molecules are required non-autonomously to the GSCs for proliferation-piwi is also required autonomously in the GSCs for proliferation.[16] In the germarium, BMP signaling has a short-range effect, therefore the physical attachment of GSCs to cap cells is important for maintenance and activity.[citation needed]

The GSCs are physically attached to the cap cells by Drosophila E-cadherin (DE-cadherin) adherens junctions and if this physical attachment is lost GSCs will differentiate and lose their identity as a stem cell.[10] The gene encoding DE-cadherin, shotgun (shg), and a gene encoding Beta-catenin ortholog, armadillo, control this physical attachment.[17] A GTPase molecule, rab11, is involved in cell trafficking of DE-cadherins. Knocking out rab11 in GSCs results in detachment of GSCs from the cap cells and premature differentiation of GSCs.[18] Additionally, zero population growth (zpg), encoding a germline-specific gap junction is required for germ cell differentiation.[19]

Both diet and insulin-like signaling directly control GSC proliferation in Drosophila melanogaster. Increasing levels of Drosophila insulin-like peptide (DILP) through diet results in increased GSC proliferation.[20] Up-regulation of DILPs in aged GSCs and their niche results in increased maintenance and proliferation.[21] It has also been shown that DILPs regulate cap cell quantities and regulate the physical attachment of GSCs to cap cells.[21]

There are two possible mechanisms for stem cell renewal, symmetrical GSC division or de-differentiation of cystoblasts. Normally, GSCs will divide asymmetrically to produce one daughter cystoblast, but it has been proposed that symmetrical division could result in the two daughter cells remaining GSCs.[22][23] If GSCs are ablated to create an empty niche and the cap cells are still present and sending maintenance signals, differentiated cystoblasts can be recruited to the niche and de-differentiate into functional GSCs.[24]

As the Drosophila female ages, the stem cell niche undergoes age-dependent loss of GSC presence and activity. These losses are thought to be caused in part by degradation of the important signaling factors from the niche that maintains GSCs and their activity. Progressive decline in GSC activity contributes to the observed reduction in fecundity of Drosophila melanogaster at old age; this decline in GSC activity can be partially attributed to a reduction of signaling pathway activity in the GSC niche.[25][26] It has been found that there is a reduction in Dpp and Gbb signaling through aging. In addition to a reduction in niche signaling pathway activity, GSCs age cell-autonomously. In addition to studying the decline of signals coming from the niche, GSCs age intrinsically; there is age-dependent reduction of adhesion of GSCs to the cap cells and there is accumulation of Reactive Oxygen species (ROS) resulting in cellular damage which contributes to GSC aging. There is an observed reduction in the number of cap cells and the physical attachment of GSCs to cap cells through aging. Shg is expressed at significantly lower levels in an old GSC niche in comparison to a young one.[26]

Males of Drosophila melanogaster each have two testes long, tubular, coiled structures and at the anterior most tip of each lies the GSC niche. The testis GSC niche is built around a population of non-mitotic hub cells (a.k.a. niche cells), to which two populations of stem cells adhere: the GSCs and the somatic stem cells (SSCs, a.k.a. somatic cyst stem cells/cyst stem cells). Each GSC is enclosed by a pair of SSCs, though each stem cell type is still in contact with the hub cells. In this way, the stem cell niche consists of these three cell types, as not only do the hub cells regulate GSC and SSC behaviour, but the stem cells also regulate the activity of each other. The Drosophila testis GSC niche has proven a valuable model system for examining a wide range of cellular processes and signalling pathways.[27]

The process of spermatogenesis begins when the GSCs divide asymmetrically, producing a GSC that maintains hub contact, and a gonialblast that exits the niche. The SSCs divide with their GSC partner, and their non-mitotic progeny, the somatic cyst cells (SCCs, a.k.a. cyst cells) will enclose the gonialblast. The gonialblast then undergoes four rounds of synchronous, transit-amplifying divisions with incomplete cytokinesis to produce a sixteen-cell spermatogonial cyst. This spermatogonial cyst then differentiates and grows into a spermatocyte, which will eventually undergo meiosis and produce sperm.[27]

The two main molecular signalling pathways regulating stem cell behaviour in the testis GSC niche are the Jak-STAT and BMP signalling pathways. Jak-STAT signalling originates in the hub cells, where the ligand Upd is secreted to the GSCs and SSCs.[28][29] This leads to activation of the Drosophila STAT, Stat92E, a transcription factor which effects GSC adhesion to the hub cells,[30] and SSC self-renewal via Zfh-1.[31] Jak-STAT signalling also influences the activation of BMP signalling, via the ligands Dpp and Gbb. These ligands are secreted into the GSCs from the SSCs and hub cells, activate BMP signalling, and suppress the expression of Bam, a differentiation factor.[32] Outside of the niche, gonialblasts no longer receive BMP ligands, and are free to begin their differentiation program. Other important signalling pathways include the MAPK and Hedgehog, which regulate germline enclosure [33] and somatic cell self-renewal,[34] respectively.

The murine GSC niche in males, also called spermatogonial stem cell (SSC) niche, is located in the basal region of seminiferous tubules in the testes. The seminiferous epithelium is composed of sertoli cells that are in contact with the basement membrane of the tubules, which separates the sertoli cells from the interstitial tissue below. This interstitial tissue comprises Leydig cells, macrophages, mesenchymal cells, capillary networks, and nerves.[35]

During development, primordial germ cells migrate into the seminiferous tubules and downward towards the basement membrane whilst remaining attached to the sertoli cells where they will subsequently differentiate into SSCs, also referred to as Asingle spermatogonia.[35][36] These SSCs can either self-renew or commit to differentiating into spermatozoa upon the proliferation of Asingle into Apaired spermatogonia. The 2 cells of Apaired spermatogonia remain attached by intercellular bridges and subsequently divide into Aaligned spermatogonia, which is made up of 416 connected cells. Aaligned spermatogonia then undergo meiosis I to form spermatocytes and meiosis II to form spermatids which will mature into spermatozoa.[37][38] This differentiation occurs along the longitudinal axis of sertoli cells, from the basement membrane to the apical lumen of the seminiferous tubules. However, sertoli cells form tight junctions that separate SSCs and spermatogonia in contact with the basement membrane from the spermatocytes and spermatids to create a basal and an adluminal compartment, whereby differentiating spermatocytes must traverse the tight junctions.[35][39] These tight junctions form the blood testis barrier (BTB) and have been suggested to play a role in isolating differentiated cells in the adluminal compartment from secreted factors by the interstitial tissue and vasculature neighboring the basal compartment.[35]

The basement membrane of the seminiferous tubule is a modified form of extracellular matrix composed of fibronectin, collagens, and laminin.[35] 1- integrin is expressed on the surface of SSCs and is involved in their adhesion to the laminin component of the basement membrane although other adhesion molecules are likely also implicated in the attachment of SSCs to the basement membrane.[40] E cadherin expression on SSCs in mice, unlike in Drosophila, have been shown to be dispensable as the transplantation of cultured SSCs lacking E-cadherin are able to colonize host seminiferous tubules and undergo spermatogenesis.[41] In addition the blood testis barrier provides architectural support and is composed of tight junction components such as occludins, claudins and zonula occludens (ZOs) which show dynamic expression during spermatogenesis.[42] For example, claudin 11 has been shown to be a necessary component of these tight junctions as mice lacking this gene have a defective blood testis barrier and do not produce mature spermatozoa.[40]

GDNF (Glial cell-derived neurotrophic factor) is known to stimulate self-renewal of SSCs and is secreted by the sertoli cells under the influence of gonadotropin FSH. GDNF is a related member of the TGF superfamily of growth factors and when overexpressed in mice, an increase in undifferentiated spermatogonia was observed which led to the formation of germ tumours.[35][40] In corroboration for its role as a renewal factor, heterozygous knockout male mice for GDNF show decreased spermatogenesis that eventually leads to infertility.[40] In addition the supplementation of GDNF has been shown to extend the expansion of mouse SSCs in culture. However, the GDNF receptor c-RET and co-receptor GFRa1 are not solely expressed on the SSCs but also on Apaired and Aaligned, therefore showing that GDNF is a renewal factor for Asingle to Aaligned in general rather than being specific to the Asingle SSC population. FGF2 (Fibroblast growth factor 2), secreted by sertoli cells, has also been shown to influence the renewal of SSCs and undifferentiated spermatogonia in a similar manner to GDNF.[35]

Although sertoli cells appear to play a major role in renewal, it expresses receptors for testosterone that is secreted by Leydig cells whereas germ cells do not contain this receptor- thus alluding to an important role of Leydig cells upstream in mediating renewal. Leydig cells also produce CSF 1 (Colony stimulating factor 1) for which SSCs strongly express the receptor CSF1R.[37] When CSF 1 was added in culture with GDNF and FGF2 no further increase in proliferation was observed, however, the longer the germ cells remained in culture with CSF-1 the greater the SSC density observed when these germ cells were transplanted into host seminiferous tubules. This showed CSF 1 to be a specific renewal factor that tilts the SSCs towards renewal over differentiation, rather than affecting proliferation of SSCs and spermatogonia. GDNF, FGF 2 and CSF 1 have also been shown to influence self-renewal of stem cells in other mammalian tissues.[35]

Plzf (Promyelocytic leukaemia zinc finger) has also been implicated in regulating SSC self-renewal and is expressed by Asingle, Apaired and Aaligned spermatogonia. Plzf directly inhibits the transcription of a receptor, c-kit, in these early spermatogonia. However, its absence in late spermatogonia permits c-kit expression, which is subsequently activated by its ligand SCF (stem cell factor) secreted by sertoli cells, resulting in further differentiation. Also, the addition of BMP4 and Activin-A have shown to reduce self-renewal of SSCs in culture and increase stem cell differentiation, with BMP4 shown to increase the expression of c-kit.[37]

Prolonged spermatogenesis relies on the maintenance of SSCs, however, this maintenance declines with age and leads to infertility. Mice between 12 and 14 months of age show decreased testis weight, reduced spermatogenesis and SSC content. Although stem cells are regarded as having the potential to infinitely replicate in vitro, factors provided by the niche are crucial in vivo. Indeed, serial transplantation of SSCs from male mice of different ages into young mice 3 months of age, whose endogenous spermatogenesis had been ablated, was used to estimate stem cell content given that each stem cell would generate a colony of spermatogenesis.[35][43] The results of this experiment showed that transplanted SSCs could be maintained far longer than their replicative lifespan for their age. In addition, a study also showed that SSCs from young fertile mice could not be maintained nor undergo spermatogenesis when transplanted into testes of old, infertile mice. Together, these results points towards a deterioration of the SSC niche itself with aging rather than the loss of intrinsic factors in the SSC.[43]

Vertebrate hematopoietic stem cells niche in the bone marrow is formed by cells subendosteal osteoblasts, sinusoidal endothelial cells and bone marrow stromal (also sometimes called reticular) cells which includes a mix of fibroblastoid, monocytic and adipocytic cells (which comprise marrow adipose tissue).[1]

The hair follicle stem cell niche is one of the more closely studied niches thanks to its relative accessibility and role in important diseases such as melanoma. The bulge area at the junction of arrector pili muscle to the hair follicle sheath has been shown to host the skin stem cells which can contribute to all epithelial skin layers. There cells are maintained by signaling in concert with niche cells signals include paracrine (e.g. sonic hedgehog), autocrine and juxtacrine signals.[44] The bulge region of the hair follicle relies on these signals to maintain the stemness of the cells. Fate mapping or cell lineage tracing has shown that Keratin 15 positive stem cells' progeny participate in all epithelial lineages.[45] The follicle undergoes cyclic regeneration in which these stem cells migrate to various regions and differentiate into the appropriate epithelial cell type. Some important signals in the hair follicle stem cell niche produced by the mesenchymal dermal papilla or the bulge include BMP, TGF- and Fibroblast growth factor (FGF) ligands and Wnt inhibitors.[46] While, Wnt signaling pathways and -catenin are important for stem cell maintenance,[47] over-expression of -catenin in hair follicles induces improper hair growth. Therefore, these signals such as Wnt inhibitors produced by surrounding cells are important to maintain and facilitate the stem cell niche.[48]

Intestinal organoids have been used to study intestinal stem cell niches. An intestinal organoid culture can be used to indirectly assess the effect of the manipulation on the stem cells through assessing the organoid's survival and growth. Research using intestinal organoids have demonstrated that the survival of intestinal stem cells is improved by the presence of neurons and fibroblasts,[49] and through the administration of IL-22.[50]

Cardiovascular stem cell niches can be found within the right ventricular free wall, atria and outflow tracks of the heart. They are composed of Isl1+/Flk1+ cardiac progenitor cells (CPCs) that are localized into discrete clusters within a ColIV and laminin extracellular matrix (ECM). ColI and fibronectin are predominantly found outside the CPC clusters within the myocardium. Immunohistochemical staining has been used to demonstrate that differentiating CPCs, which migrate away from the progenitor clusters and into the ColI and fibronectin ECM surrounding the niche, down-regulate Isl1 while up-regulating mature cardiac markers such as troponin C.[51] There is a current controversy over the role of Isl1+ cells in the cardiovascular system. While major publications have identified these cells as CPC's and have found a very large number in the murine and human heart, recent publications have found very few Isl1+ cells in the murine fetal heart and attribute their localization to the sinoatrial node,[52] which is known as an area that contributes to heart pacemaking. The role of these cells and their niche are under intense research and debate.[citation needed]

Neural stem cell niches are divided in two: the Subependymal zone (SEZ) and the Subgranular zone (SGZ).

The SEZ is a thin area beneath the ependymal cell layer that contains three types of neural stem cells: infrequently dividing neural stem cells (NSCs), rapidly dividing transit amplifying precursors (TaPs) and neuroblasts (NBs). The SEZ extracellular matrix (ECM) has significant differences in composition compared to surrounding tissues. Recently, it was described that progenitor cells, NSCs, TaPs and NBs were attached to ECM structures called Fractones.[53] These structures are rich in laminin, collagen and heparan sulfate proteoglycans.[54] Other ECM molecules, such as tenascin-C, MMPs and different proteoglycans are also implicated in the neural stem cell niche.[55]

Cancer tissue is morphologically heterogenous, not only due to the variety of cell types present, endothelial, fibroblast and various immune cells, but cancer cells themselves are not a homogenous population either.[citation needed]

In accordance with the hierarchy model of tumours, the cancer stem cells (CSC) are maintained by biochemical and physical contextual signals emanating from the microenvironment, called the cancer stem cell niche.[56] The CSC niche is very similar to normal stem cells niche (embryonic stem cell (ESC), Adult Stem Cell ASC) in function (maintaining of self-renewal, undifferentiated state and ability to differentiate) and in signalling pathways (Activin/Noda, Akt/PTEN, JAK/STAT, PI3-K, TGF-, Wnt and BMP).[57] It is hypothesized that CSCs arise form aberrant signalling of the microenvironment and participates not only in providing survival signals to CSCs but also in metastasis by induction of epithelial-mesenchymal transition (EMT).[citation needed]

Hypoxic condition in stem cell niches (ESC, ASC or CSC) is necessary for maintaining stem cells in an undifferentiated state and also for minimizing DNA damage via oxidation. The maintaining of the hypoxic state is under control of Hypoxia-Inducible transcription Factors (HIFs).[58] HIFs contribute to tumour progression, cell survival and metastasis by regulation of target genes as VEGF, GLUT-1, ADAM-1, Oct4 and Notch.[57]

Hypoxia plays an important role in the regulation of cancer stem cell niches and EMT through the promotion of HIFs.[59] These HIFs help maintain cancer stem cell niches by regulating important stemness genes such as Oct4, Nanog, SOX2, Klf4, and cMyc.[60][61] HIFs also regulate important tumor suppressor genes such as p53 and genes that promote metastasis.[62][63] Although HIFs increase the survival of cells by decreasing the effects of oxidative stress, they have also been shown to decrease factors such as RAD51 and H2AX that maintain genomic stability.[64] In the hypoxic condition there is an increase of intracellular Reactive Oxygen Species (ROS) which also promote CSCs survival via stress response.[65][66] ROS stabilizes HIF-1 which promotes the Met proto-oncogene, which drives metastasis or motogenic escape in melanoma cells.[67] All of these factors contribute to a cancer stem cell phenotype which is why it is often referred to as a hypoxic stem cell niche. Hypoxic environments are often found in tumors where the cells are dividing faster that angiogenesis can occur. It is important to study hypoxia as an aspect of cancer because hypoxic environments have been shown to be resistant to radiation therapy.[68] Radiation has been shown to increase the amounts of HIF-1.[69] EMT induction by hypoxia though interactions between HIF-1 and ROS is crucial for metastasis in cancers such as melanoma. It has been found that many genes associated with melanoma are regulated by hypoxia such as MXI1, FN1, and NME1.[70]

Epithelialmesenchymal transition is a morphogenetic process, normally occurs in embryogenesis that is "hijacked" by cancer stem cells by detaching from their primary place and migrating to another one. The dissemination is followed by reverse transition so-called Epithelial-Mesenchymal Transition (EMT). This process is regulated by CSCs microenvironment via the same signalling pathways as in embryogenesis using the growth factors (TGF-, PDGF, EGF), cytokine IL-8 and extracellular matrix components. These growth factors' interactions through intracellular signal transducers like -catenin has been shown to induce metastatic potential.[71][72] A characteristic of EMT is loss of the epithelial markers (E-cadherin, cytokeratins, claudin, occluding, desmoglein, desmocolin) and gain of mesenchymal markers (N-cadherin, vimentin, fibronectin).[73]

There is also certain degree of similarity in homing-mobilization of normal stem cells and metastasis-invasion of cancer stem cells. There is an important role of Matrix MetalloProteinases (MMP), the principal extracellular matrix degrading enzymes, thus for example matrix metalloproteinase-2 and 9 are induced to expression and secretion by stromal cells during metastasis of colon cancer via direct contact or paracrine regulation. The next sharing molecule is Stromal cell-Derived Factor-1 (SDF-1).[73][74]

The EMT and cancer progression can be triggered also by chronic inflammation. The main roles have molecules (IL-6, IL-8, TNF-, NFB, TGF-, HIF-1) which can regulate both processes through regulation of downstream signalling that overlapping between EMT and inflammation.[57] The downstream pathways involving in regulation of CSCs are Wnt, SHH, Notch, TGF-, RTKs-EGF, FGF, IGF, HGF.

NFB regulates the EMT, migration and invasion of CSCs through Slug, Snail and Twist. The activation of NFB leads to increase not only in production of IL-6, TNF- and SDF-1 but also in delivery of growth factors.

The source of the cytokine production are lymphocytes (TNF-), Mesenchymal Stem Cells (SDF-1, IL-6, IL8).

Interleukin 6 mediates activation of STAT3. The high level of STAT3 was described in isolated CSCs from liver, bone, cervical and brain cancer. The inhibition of STAT3 results in dramatic reduction in their formation. Generally IL-6 contributes a survival advantage to local stem cells and thus facilitates tumorigenesis.[57]

SDF-1 secreted from Mesenchymal Stem Cells (MSCs) has important role in homing and maintenance of Hematopoietic Stem Cell (HSC) in bone marrow niche but also in homing and dissemination of CSC.[74]

Hypoxia is a main stimulant for angiogenesis, with HIF-1 being the primary mediator. Angiogenesis induced by hypoxic conditions is called an "Angiogenic switch". HIF-1 promotes expression of several angiogenic factors: Vascular Endothelial Growth Factor (VEGF), basic Fibroblast Growth Factor (bFGF), Placenta-Like Growth Factor (PLGF), Platelet-Derived Growth Factor (PDGF) and Epidermal Growth Factor. But there is evidence that the expression of angiogenic agens by cancer cells can also be HIF-1 independent. It seems that there is an important role of Ras protein, and that intracellular levels of calcium regulate the expression of angiogenic genes in response to hypoxia.[73]

The angiogenic switch downregulates angiogenesis suppressor proteins, such as thrombospondin, angiostatin, endostatin and tumstatin. Angiogenesis is necessary for the primary tumour growth.[citation needed]

During injury, support cells are able to activate a program for repair, recapitulating aspects of development in the area of damage. These areas become permissive for stem cell renewal, migration and differentiation. For instance in the CNS, injury is able to activate a developmental program in astrocytes that allow them to express molecules that support stem cells such as chemokines i.e. SDF-1[75] and morphogens such as sonic hedgehog.[76]

It is evident that biophysio-chemical characteristics of ECM such as composition, shape, topography, stiffness, and mechanical strength can control the stem cell behavior. These ECM factors are equally important when stem cells are grown in vitro. Given a choice between niche cell-stem cell interaction and ECM-stem cell interaction, mimicking ECM is preferred as that can be precisely controlled by scaffold fabrication techniques, processing parameters or post-fabrication modifications. In order to mimic, it is essential to understand natural properties of ECM and their role in stem cell fate processes. Various studies involving different types of scaffolds that regulate stem cells fate by mimicking these ECM properties have been done.[2])

[77]

Read more from the original source:
Stem-cell niche - Wikipedia

BORDEAUX, France, Oct. 11, 2022 /PRNewswire/ --TreeFrog Therapeutics,a biotechnology company developing stem cell-derived therapies in regenerative medicine and immuno-oncology based on the biomimetic C-Stemtechnology platform, and Invetech, a global leader in the development and production ofautomated manufacturing solutionsfor cell and advanced therapies, today announced the delivery of a GMP-grade cell encapsulation device using the C-Stemtechnology. The machine will be transferred in 2023 to a contract development and manufacturing organization (CDMO) to produce TreeFrog's cell therapy candidate for Parkinson's disease, with the aim of a first-in-human trial in 2024.Over 2023, Invetech will deliver three additional GMP encapsulation devices to support TreeFrog's in-house and partnered cell therapy programs in regenerative medicine and immuno-oncology.

TreeFrogs C-Stem technology generates alginate capsules seeded with induced pluripotent stem cells (iPSCs) at very high speed. Engineered to mimic the in vivo stem cell niche, the capsules allow iPSCs to grow exponentially in 3D, and to differentiate into ready-to-transplant functional microtissues.

Blending microfluidics and stem cell biology, TreeFrog's C-Stemtechnology generates alginate capsules seeded with induced pluripotent stem cells (iPSCs) at very high speed. Engineered to mimic the in vivo stem cell niche, the capsules allow iPSCs to grow exponentially in 3D, and to differentiate into ready-to-transplant functional microtissues. And because alginate is both porous and highly resistant, encapsulated iPSCs can be expanded and differentiated in large-scale bioreactors without suffering from impeller-induced shear stress.

"TreeFrog Therapeutics introduces a breakthrough technology for cell therapy, which impacts scale, quality, as well as the efficacy and safety potential of cellular products. Automating this disruptive technology and turning it into a robust GMP-grade instrument is a tremendous achievement for our team. This deliverable is the result of a very fruitful and demanding collaboration with TreeFrog's engineers in biophysics and bioproduction over the past four years. We're now eager to learn how the neural microtissues produced with C-Stemwill perform in the clinic." Anthony Annibale, Global VP Commercial at Invetech.

Started in 2019, the collaboration between TreeFrog and Invetech led to the delivery of a prototype in October 2020. With this research-grade machine, TreeFrog demonstrated the scalability of C-Stem, moving within six months from milliliter-scale to 10-liter bioreactors. In June 2021, the company announced the production of two single-batches of 15 billion iPSCs in 10L bioreactors with an unprecedented 275-fold amplification per week, striking reproducibility and best-in-class cell quality. The new GMP-grade device delivered by Invetech features the same technical specifications. The machine generates over 1,000 capsules per second, allowing to seed bioreactors from 200mL to 10L. However, the device was entirely redesigned to fit bioproduction standards.

"With the GMP device, our main challenge was to minimize the learning curve for operators, so as to facilitate tech transfer. Invetech and our team did an outstanding job in terms of automation and industrial design to make the device both robust and easy to use. As an inventor, I am so proud of the journey of the C-Stemtechnology. Many elements have been changed and improved on the way, and now comes the time to put the platform in the hands of real-world users to make real products." Kevin Alessandri, Ph.D., co-founder and chief technology officer, TreeFrog Therapeutics

"In October 2020, we announced that we were planning for the delivery of a GMP encapsulation device by the end of 2022. Exactly two years after, we're right on time. I guess this machine testifies to the outstanding execution capacity of TreeFrog and Invetech. But more importantly, this machine constitutes a key milestone. Our platform can now be used to manufacture clinical-grade cell therapy products. Our plan is to accelerate the translation of our in-house and partnered programs to the clinic, with a focus on immuno-oncology and regenerative medicine applications." Frederic Desdouits, Ph.D., chief executive officer, TreeFrog Therapeutics

About Invetech

Invetech helps cell and gene therapy developers to visualize, strategize and manage the future. With proven processes, expert insights and full-spectrum services, we swiftly accelerate life-changing therapies from the clinic to commercial-scale manufacturing. Through our ready-to-run, preconfigured systems, our custom and configurable technology platforms and automated production systems, we assure predictable, reproducible products of the highest quality and efficacy. Our integrated approach brings together biological scientists, engineers, designers and program managers to deliver successful, cost-effective market offerings to more people, more quickly. Working in close collaboration with early-stage and mature life sciences companies, we are committed to advancing the next generation of vital, emerging therapies to revolutionize healthcare and precision medicine.invetechgroup.com

About TreeFrog Therapeutics

TreeFrog Therapeutics is a French-based biotech company aiming to unlock access to cell therapies for millions of patients. Bringing together over 100 biophysicists, cell biologists and bioproduction engineers, TreeFrog Therapeutics raised $82M over the past 3 years to advance a pipeline of stem cell-based therapies in immuno-oncology and regenerative medicine. In 2022, the company opened technological hubs in Boston, USA, and Kobe, Japan, with the aim of driving the adoption of the C-Stemplatform and establish strategic alliances with leading academic, biotech and industry players in the field of cell therapy.www.treefrog.fr

Media ContactsPierre-Emmanuel GaultierTreeFrog Therapeutics+ 33 6 45 77 42 58pierre@treefrog.fr

Marisa ReinosoInvetech+1 858 437 1061marisa.reinoso@invetechgroup.com

TreeFrog Therapeutics is a French-based biotech company aiming to unlock access to cell therapies for millions of patients. Bringing together over 100 biophysicists, cell biologists and bioproduction engineers, TreeFrog Therapeutics raised $82M over the past 3 years to advance a pipeline of stem cell-based therapies in immuno-oncology and regenerative medicine.

Invetech logo (PRNewsFoto/Invetech)

Cision

View original content to download multimedia:https://www.prnewswire.com/news-releases/breakthrough-technology-for-ips-derived-cell-therapies-turned-into-gmp-platform-by-treefrog-therapeutics--invetech-301645370.html

SOURCE Invetech; Treefrog Therapeutics

View original post here:
BREAKTHROUGH TECHNOLOGY FOR IPS-DERIVED CELL THERAPIES TURNED INTO GMP PLATFORM BY TREEFROG THERAPEUTICS & INVETECH - Yahoo Finance

Dublin, Oct. 11, 2022 (GLOBE NEWSWIRE) -- The "Stem Cell Manufacturing Market: Global Industry Trends, Share, Size, Growth, Opportunity and Forecast 2022-2027" report has been added to ResearchAndMarkets.com's offering.

The global stem cell manufacturing market size reached US$ 11.2 Billion in 2021. Looking forward, the publisher expects the market to reach US$ 18.59 Billion by 2027, exhibiting a CAGR of 8.81% during 2021-2027.

Stem cells are undifferentiated or partially differentiated cells that make up the tissues and organs of animals and plants. They are commonly sourced from blood, bone marrow, umbilical cord, embryo, and placenta. Under the right body and laboratory conditions, stem cells can divide to form more cells, such as red blood cells (RBCs), platelets, and white blood cells, which generate specialized functions.

They are widely used for human disease modeling, drug discovery, development of cell therapies for untreatable diseases, gene therapy, and tissue engineering. Stem cells are cryopreserved to maintain their viability and minimize genetic change and are consequently used later to replace damaged organs and tissues and treat various diseases.

Stem Cell Manufacturing Market Trends:

The global market is primarily driven by the increasing venture capital (VC) investments in stem cell research due to the rising awareness about the therapeutic potency of stem cells. Apart from this, the widespread product utilization in effective disease management, personalized medicine, and genome testing applications are favoring the market growth. Additionally, the incorporation of three-dimensional (3D) printing and microfluidic technologies to reduce production time and lower cost by integrating multiple production steps into one device is providing an impetus to the market growth.

Furthermore, the increasing product utilization in the pharmaceutical industry for manufacturing hematopoietic stem cells (HSC)- and mesenchymal stem cells (MSC)-based drugs for treating tumors, leukemia, and lymphoma is acting as another growth-inducing factor.

Moreover, the increasing product application in research applications to produce new drugs that assist in improving functions and altering the progress of diseases is providing a considerable boost to the market. Other factors, including the increasing usage of the technique in tissue and organ replacement therapies, significant improvements in medical infrastructure, and the implementation of various government initiatives promoting public health, are anticipated to drive the market.

Key Players

Key Questions Answered in This Report:

Key Market Segmentation

Breakup by Product:

Breakup by Application:

Breakup by End User:

Breakup by Region:

Key Topics Covered:

1 Preface

2 Scope and Methodology

3 Executive Summary

4 Introduction

5 Global Stem Cell Manufacturing Market

6 Market Breakup by Product

7 Market Breakup by Application

8 Market Breakup by End User

9 Market Breakup by Region

10 SWOT Analysis

11 Value Chain Analysis

12 Porters Five Forces Analysis

13 Price Analysis

14 Competitive Landscape

For more information about this report visit https://www.researchandmarkets.com/r/5iujo7

Original post:
Stem Cell Manufacturing Global Market Report 2022: Widespread Product Utilization in Effective Disease Ma - Benzinga

Company Logo

Global Stem Cell Manufacturing Market

Global Stem Cell Manufacturing Market

Dublin, Oct. 11, 2022 (GLOBE NEWSWIRE) -- The "Stem Cell Manufacturing Market: Global Industry Trends, Share, Size, Growth, Opportunity and Forecast 2022-2027" report has been added to ResearchAndMarkets.com's offering.

The global stem cell manufacturing market size reached US$ 11.2 Billion in 2021. Looking forward, the publisher expects the market to reach US$ 18.59 Billion by 2027, exhibiting a CAGR of 8.81% during 2021-2027.

Stem cells are undifferentiated or partially differentiated cells that make up the tissues and organs of animals and plants. They are commonly sourced from blood, bone marrow, umbilical cord, embryo, and placenta. Under the right body and laboratory conditions, stem cells can divide to form more cells, such as red blood cells (RBCs), platelets, and white blood cells, which generate specialized functions.

They are widely used for human disease modeling, drug discovery, development of cell therapies for untreatable diseases, gene therapy, and tissue engineering. Stem cells are cryopreserved to maintain their viability and minimize genetic change and are consequently used later to replace damaged organs and tissues and treat various diseases.

Stem Cell Manufacturing Market Trends:

The global market is primarily driven by the increasing venture capital (VC) investments in stem cell research due to the rising awareness about the therapeutic potency of stem cells. Apart from this, the widespread product utilization in effective disease management, personalized medicine, and genome testing applications are favoring the market growth. Additionally, the incorporation of three-dimensional (3D) printing and microfluidic technologies to reduce production time and lower cost by integrating multiple production steps into one device is providing an impetus to the market growth.

Furthermore, the increasing product utilization in the pharmaceutical industry for manufacturing hematopoietic stem cells (HSC)- and mesenchymal stem cells (MSC)-based drugs for treating tumors, leukemia, and lymphoma is acting as another growth-inducing factor.

Story continues

Moreover, the increasing product application in research applications to produce new drugs that assist in improving functions and altering the progress of diseases is providing a considerable boost to the market. Other factors, including the increasing usage of the technique in tissue and organ replacement therapies, significant improvements in medical infrastructure, and the implementation of various government initiatives promoting public health, are anticipated to drive the market.

Key Players

Anterogen Co. Ltd.

Becton Dickinson and Company

Bio-Rad Laboratories Inc.

Bio-Techne Corporation

Corning Incorporated

FUJIFILM Holdings Corporation

Lonza Group AG

Merck KGaA

Sartorius AG

Takara Bio Inc.

Thermo Fisher Scientific Inc.

Key Questions Answered in This Report:

How has the global stem cell manufacturing market performed so far and how will it perform in the coming years?

What has been the impact of COVID-19 on the global stem cell manufacturing market?

What are the key regional markets?

What is the breakup of the market based on the product?

What is the breakup of the market based on the application?

What is the breakup of the market based on the end user?

What are the various stages in the value chain of the industry?

What are the key driving factors and challenges in the industry?

What is the structure of the global stem cell manufacturing market and who are the key players?

What is the degree of competition in the industry?

Key Market Segmentation

Breakup by Product:

Consumables

Culture Media

Others

Instruments

Bioreactors and Incubators

Cell Sorters

Others

Stem Cell Lines

Hematopoietic Stem Cells (HSC)

Mesenchymal Stem Cells (MSC)

Induced Pluripotent Stem Cells (iPSC)

Embryonic Stem Cells (ESC)

Neural Stem Cells (NSC)

Multipotent Adult Progenitor Stem Cells

Breakup by Application:

Research Applications

Life Science Research

Drug Discovery and Development

Clinical Application

Allogenic Stem Cell Therapy

Autologous Stem Cell Therapy

Cell and Tissue Banking Applications

Breakup by End User:

Pharmaceutical & Biotechnology Companies

Academic Institutes, Research Laboratories and Contract Research Organizations

Hospitals and Surgical Centers

Cell and Tissue banks

Others

Breakup by Region:

North America

United States

Canada

Asia-Pacific

China

Japan

India

South Korea

Australia

Indonesia

Others

Europe

Germany

France

United Kingdom

Italy

Spain

Russia

Others

Latin America

Brazil

Mexico

Others

Middle East and Africa

Key Topics Covered:

1 Preface

2 Scope and Methodology

3 Executive Summary

4 Introduction

5 Global Stem Cell Manufacturing Market

6 Market Breakup by Product

7 Market Breakup by Application

8 Market Breakup by End User

9 Market Breakup by Region

Here is the original post:
Stem Cell Manufacturing Global Market Report 2022: Widespread Product Utilization in Effective Disease Management, Personalized Medicine, and Genome...

CRANBURY, N.J.--(BUSINESS WIRE)--Rocket Pharmaceuticals, Inc. (NASDAQ: RCKT), a leading late-stage biotechnology company advancing an integrated and sustainable pipeline of genetic therapies for rare childhood disorders with high unmet need, today announces data presentations at the 29th Annual Congress of the European Society of Gene & Cell Therapy (ESGCT) in Edinburgh, United Kingdom, taking place October 11-14, 2022. Presentations will include clinical data from Rockets lentiviral vector (LV)-based gene therapy programs for Leukocyte Adhesion Deficiency-I (LAD-I), Fanconi Anemia (FA) and Pyruvate Kinase Deficiency (PKD). Donald B. Kohn, MD, Distinguished Professor of Microbiology, Immunology & Molecular Genetics, Pediatrics, and Molecular & Medical Pharmacology at University of California, Los Angeles (UCLA) and Director of the UCLA Human Gene and Cell Therapy Program, will also give an Invited Talk incorporating previously disclosed data from the RP-L201 trial for LAD-I.

Positive Updated Safety and Efficacy Data from Phase 2 Pivotal Trial for Fanconi Anemia (FA)

The poster and presentation include updated safety and efficacy data from the Phase 2 pivotal trial of RP-L102, Rockets ex-vivo lentiviral gene therapy candidate for the treatment of FA.

Positive Top-line Clinical Data from Phase 2 Pivotal Trial for Severe Leukocyte Adhesion Deficiency-I (LAD-I)

The oral presentation includes previously disclosed efficacy and safety data at three to 24 months of follow-up after RP-L201 infusion for all patients and overall survival data for seven patients at 12 months or longer after infusion. RP-L201 is Rockets ex-vivo lentiviral gene therapy candidate for the treatment of severe LAD-I.

Interim Data from Ongoing Phase 1 Trial for Pyruvate Kinase Deficiency (PKD)

The poster and presentation include previously disclosed safety and efficacy data from the Phase 1 trial of RP-L301, Rockets ex-vivo lentiviral gene therapy candidate for the treatment of PKD.

Details for Rockets Invited Talk and poster presentations are as follows:

Title: Interim Results from an ongoing Phase 1/2 Study of Lentiviral-Mediated Ex-Vivo Gene Therapy for Pediatric Patients with Severe Leukocyte Adhesion Deficiency-I (LAD-I)Session: Clinical Trials (Plenary 2)Presenter: Donald B. Kohn, MD - University of California, Los Angeles, Distinguished Professor of Microbiology, Immunology & Molecular Genetics (MIMG), Pediatrics, and Molecular & Medical Pharmacology; Director of the UCLA Human Gene and Cell Therapy ProgramSession date and time: Wednesday, 12 October at 11:10-13:15 BSTLocation: Edinburgh International Conference Centre (EICC)Presentation Number: INV20

Title: Lentiviral-Mediated Gene Therapy for Patients with Fanconi Anemia [Group A]: Results from Global RP-L102 Clinical TrialsSession: Poster Session 1Presenter: Julin Sevilla MD, PhD - Fundacin para la Investigacin Biomdica, Hospital Infantil Universitario Nio JessSession date and time: Wednesday, 12 October at 19:30-21:00 BSTLocation: Edinburgh International Conference Centre (EICC)Poster Number: P139

Title: Preliminary Conclusions of the Phase I/II Gene therapy Trial in Patients with Fanconi Anemia-ASession: Blood Diseases: Haematopoietic Cell DisordersPresenter: Juan Bueren, PhD - Unidad de Innovacin Biomdica, Centro de Investigaciones Energticas, Medioambientales y Tecnolgicas (CIEMAT)Session date and time: Thursday, 13 October at 15:30-17:30 BSTLocation: Edinburgh International Conference Centre (EICC)Presentation Number: INV41

Title: Interim Results from an Ongoing Global Phase 1 Study of Lentiviral-Mediated Gene Therapy for Pyruvate Kinase DeficiencySession: Poster Session 2Presenter: Jos Luis Lpez Lorenzo, MD, Hospital Universitario Fundacin Jimnez DazSession date and time: Thursday, 13 October at 17:30-19:15 BSTLocation: Edinburgh International Conference Centre (EICC)Poster Number: P128

Abstracts for the presentations can be found online at: https://www.esgct.eu/.

About Fanconi Anemia

Fanconi Anemia (FA) is a rare pediatric disease characterized by bone marrow failure, malformations and cancer predisposition. The primary cause of death among patients with FA is bone marrow failure, which typically occurs during the first decade of life. Allogeneic hematopoietic stem cell transplantation (HSCT), when available, corrects the hematologic component of FA, but requires myeloablative conditioning. Graft-versus-host disease, a known complication of allogeneic HSCT, is associated with an increased risk of solid tumors, mainly squamous cell carcinomas of the head and neck region. Approximately 60-70% of patients with FA have a Fanconi Anemia complementation group A (FANCA) gene mutation, which encodes for a protein essential for DNA repair. Mutations in the FANCA gene leads to chromosomal breakage and increased sensitivity to oxidative and environmental stress. Increased sensitivity to DNA-alkylating agents such as mitomycin-C (MMC) or diepoxybutane (DEB) is a gold standard test for FA diagnosis. Somatic mosaicism occurs when there is a spontaneous correction of the mutated gene that can lead to stabilization or correction of a FA patients blood counts in the absence of any administered therapy. Somatic mosaicism, often referred to as natural gene therapy provides a strong rationale for the development of FA gene therapy because of the selective growth advantage of gene-corrected hematopoietic stem cells over FA cells.

About Leukocyte Adhesion Deficiency-I

Severe Leukocyte Adhesion Deficiency-I (LAD-I) is a rare, autosomal recessive pediatric disease caused by mutations in the ITGB2 gene encoding for the beta-2 integrin component CD18. CD18 is a key protein that facilitates leukocyte adhesion and extravasation from blood vessels to combat infections. As a result, children with severe LAD-I are often affected immediately after birth. During infancy, they suffer from recurrent life-threatening bacterial and fungal infections that respond poorly to antibiotics and require frequent hospitalizations. Children who survive infancy experience recurrent severe infections including pneumonia, gingival ulcers, necrotic skin ulcers, and septicemia. Without a successful bone marrow transplant, mortality in patients with severe LAD-I is 60-75% prior to the age of 2 and survival beyond the age of 5 is uncommon. There is a high unmet medical need for patients with severe LAD-I.

Rockets LAD-I research is made possible by a grant from the California Institute for Regenerative Medicine (Grant Number CLIN2-11480). The contents of this press release are solely the responsibility of Rocket and do not necessarily represent the official views of CIRM or any other agency of the State of California.

About Pyruvate Kinase Deficiency

Pyruvate kinase deficiency (PKD) is a rare, monogenic red blood cell disorder resulting from a mutation in the PKLR gene encoding for the pyruvate kinase enzyme, a key component of the red blood cell glycolytic pathway. Mutations in the PKLR gene result in increased red cell destruction and the disorder ranges from mild to life-threatening anemia. PKD has an estimated prevalence of 4,000 to 8,000 patients in the United States and the European Union. Children are the most commonly and severely affected subgroup of patients. Currently available treatments include splenectomy and red blood cell transfusions, which are associated with immune defects and chronic iron overload.

RP-L301 was in-licensed from the Centro de Investigaciones Energticas, Medioambientales y Tecnolgicas (CIEMAT), Centro de Investigacin Biomdica en Red de Enfermedades Raras (CIBERER) and Instituto de Investigacin Sanitaria de la Fundacin Jimnez Daz (IIS-FJD).

About Rocket Pharmaceuticals, Inc.

Rocket Pharmaceuticals, Inc. (NASDAQ: RCKT) is advancing an integrated and sustainable pipeline of investigational genetic therapies designed to correct the root cause of complex and rare childhood disorders. The Companys platform-agnostic approach enables it to design the best therapy for each indication, creating potentially transformative options for patients afflicted with rare genetic diseases. Rocket's clinical programs using lentiviral vector (LVV)-based gene therapy are for the treatment of Fanconi Anemia (FA), a difficult to treat genetic disease that leads to bone marrow failure and potentially cancer, Leukocyte Adhesion Deficiency-I (LAD-I), a severe pediatric genetic disorder that causes recurrent and life-threatening infections which are frequently fatal, and Pyruvate Kinase Deficiency (PKD), a rare, monogenic red blood cell disorder resulting in increased red cell destruction and mild to life-threatening anemia. Rockets first clinical program using adeno-associated virus (AAV)-based gene therapy is for Danon Disease, a devastating, pediatric heart failure condition. For more information about Rocket, please visit http://www.rocketpharma.com

Rocket Cautionary Statement Regarding Forward-Looking Statements

Various statements in this release concerning Rockets future expectations, plans and prospects, including without limitation, Rockets expectations regarding its guidance for 2022 in light of COVID-19, the safety and effectiveness of product candidates that Rocket is developing to treat Fanconi Anemia (FA), Leukocyte Adhesion Deficiency-I (LAD-I), Pyruvate Kinase Deficiency (PKD), and Danon Disease, the expected timing and data readouts of Rockets ongoing and planned clinical trials, the expected timing and outcome of Rockets regulatory interactions and planned submissions, Rockets plans for the advancement of its Danon Disease program and the safety, effectiveness and timing of related pre-clinical studies and clinical trials, may constitute forward-looking statements for the purposes of the safe harbor provisions under the Private Securities Litigation Reform Act of 1995 and other federal securities laws and are subject to substantial risks, uncertainties and assumptions. You should not place reliance on these forward-looking statements, which often include words such as "believe," "expect," "anticipate," "intend," "plan," "will give," "estimate," "seek," "will," "may," "suggest" or similar terms, variations of such terms or the negative of those terms. Although Rocket believes that the expectations reflected in the forward-looking statements are reasonable, Rocket cannot guarantee such outcomes. Actual results may differ materially from those indicated by these forward-looking statements as a result of various important factors, including, without limitation, Rockets ability to monitor the impact of COVID-19 on its business operations and take steps to ensure the safety of patients, families and employees, the interest from patients and families for participation in each of Rockets ongoing trials, our expectations regarding the delays and impact of COVID-19 on clinical sites, patient enrollment, trial timelines and data readouts, our expectations regarding our drug supply for our ongoing and anticipated trials, actions of regulatory agencies, which may affect the initiation, timing and progress of pre-clinical studies and clinical trials of its product candidates, Rockets dependence on third parties for development, manufacture, marketing, sales and distribution of product candidates, the outcome of litigation, and unexpected expenditures, as well as those risks more fully discussed in the section entitled "Risk Factors" in Rockets Annual Report on Form 10-K for the year ended December 31, 2021, filed February 28, 2022 with the SEC and subsequent filings with the SEC including our Quarterly Reports on Form 10-Q. Accordingly, you should not place undue reliance on these forward-looking statements. All such statements speak only as of the date made, and Rocket undertakes no obligation to update or revise publicly any forward-looking statements, whether as a result of new information, future events or otherwise.

View original post here:
Rocket Pharmaceuticals Announces Presentations Highlighting Lentiviral Gene Therapies at the 29th Annual Congress of the European Society of Gene...

Factors affecting skin color in humans

Human skin color ranges from the darkest brown to the lightest hues. Differences in skin color among individuals is caused by variation in pigmentation, which is the result of genetics (inherited from one's biological parents and or individual gene alleles), exposure to the sun, natural and sexual selection, or all of these. Differences across populations evolved through natural or sexual selection, because of social norms and differences in environment, as well as regulations of the biochemical effects of ultraviolet radiation penetrating the skin.[1]

The actual skin color of different humans is affected by many substances, although the single most important substance is the pigment melanin. Melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin color of darker-skin humans. The skin color of people with light skin is determined mainly by the bluish-white connective tissue under the dermis and by the hemoglobin circulating in the veins of the dermis. The red color underlying the skin becomes more visible, especially in the face, when, as consequence of physical exercise or sexual arousal, or the stimulation of the nervous system (anger, embarrassment), arterioles dilate.[2] Color is not entirely uniform across an individual's skin; for example, the skin of the palm and the sole is lighter than most other skin, and this is especially noticeable in darker-skinned people.[3]

There is a direct correlation between the geographic distribution of ultraviolet radiation (UVR) and the distribution of indigenous skin pigmentation around the world. Areas that receive higher amounts of UVR, generally located closer to the equator, tend to have darker-skinned populations. Areas that are far from the tropics and closer to the poles have lower intensity of UVR, which is reflected in lighter-skinned populations.[4] Some researchers suggest that human populations over the past 50,000 years have changed from dark-skinned to light-skinned and vice versa as they migrated to different UV zones,[5] and that such major changes in pigmentation may have happened in as little as 100 generations (2,500 years) through selective sweeps.[5][6][7] Natural skin color can also darken as a result of tanning due to exposure to sunlight. The leading theory is that skin color adapts to intense sunlight irradiation to provide partial protection against the ultraviolet fraction that produces damage and thus mutations in the DNA of the skin cells.[8][9] In addition, it has been observed that females on average are significantly lighter in skin pigmentation than males. Females need more calcium during pregnancy and lactation. The body synthesizes vitamin D from sunlight, which helps it absorb calcium. Females evolved to have lighter skin so their bodies absorb more calcium.[10]

The social significance of differences in skin color has varied across cultures and over time, as demonstrated with regard to social status and discrimination.

Melanin is produced by cells called melanocytes in a process called melanogenesis. Melanin is made within small membranebound packages called melanosomes. As they become full of melanin, they move into the slender arms of melanocytes, from where they are transferred to the keratinocytes. Under normal conditions, melanosomes cover the upper part of the keratinocytes and protect them from genetic damage. One melanocyte supplies melanin to thirty-six keratinocytes according to signals from the keratinocytes. They also regulate melanin production and replication of melanocytes.[7] People have different skin colors mainly because their melanocytes produce different amount and kinds of melanin.

The genetic mechanism behind human skin color is mainly regulated by the enzyme tyrosinase, which creates the color of the skin, eyes, and hair shades.[11][12] Differences in skin color are also attributed to differences in size and distribution of melanosomes in the skin.[7] Melanocytes produce two types of melanin. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms. Most are derived from the amino acid tyrosine. Eumelanin is found in hair, areola, and skin, and the hair colors gray, black, blond, and brown. In humans, it is more abundant in people with dark skin. Pheomelanin, a pink to red hue is found in particularly large quantities in red hair,[13] the lips, nipples, glans of the penis, and vagina.[14]

Both the amount and type of melanin produced is controlled by a number of genes that operate under incomplete dominance.[15] One copy of each of the various genes is inherited from each parent. Each gene can come in several alleles, resulting in the great variety of human skin tones. Melanin controls the amount of ultraviolet (UV) radiation from the sun that penetrates the skin by absorption. While UV radiation can assist in the production of vitamin D, excessive exposure to UV can damage health.

Loss of body hair in Hominini species is assumed to be related to the emergence of bipedalism some 5 to 7 million years ago.[16] Bipedal hominin body hair may have disappeared gradually to allow better heat dissipation through sweating.[10][17]The emergence of skin pigmentation dates to about 1.2 million years ago,[18] under conditions of a megadrought that drove early humans into arid, open landscapes. Such conditions likely caused excess UV-B radiation. This favored the emergence of skin pigmentation in order to protect from folate depletion due to the increased exposure to sunlight.[8][9] A theory that the pigmentation helped counter xeric stress by increasing the epidermal permeability barrier[19] has been disproved.[8]

With the evolution of hairless skin, abundant sweat glands, and skin rich in melanin, early humans could walk, run, and forage for food for long periods of time under the hot sun without brain damage due to overheating, giving them an evolutionary advantage over other species.[7] By 1.2 million years ago, around the time of Homo ergaster, archaic humans (including the ancestors of Homo sapiens) had exactly the same receptor protein as modern sub-Saharan Africans.[17]

This was the genotype inherited by anatomically modern humans, but retained only by part of the extant populations, thus forming an aspect of human genetic variation. About 100,00070,000 years ago, some anatomically modern humans (Homo sapiens) began to migrate away from the tropics to the north where they were exposed to less intense sunlight. This was possibly in part due to the need for greater use of clothing to protect against the colder climate. Under these conditions there was less photodestruction of folate and so the evolutionary pressure working against the survival of lighter-skinned gene variants was reduced. In addition, lighter skin is able to generate more vitamin D (cholecalciferol) than darker skin, so it would have represented a health benefit in reduced sunlight if there were limited sources of vitamin D.[10] Hence the leading hypothesis for the evolution of human skin color proposes that:

The genetic mutations leading to light skin, though partially different among East Asians and Western Europeans,[20] suggest the two groups experienced a similar selective pressure after settlement in northern latitudes.[21]

The theory is partially supported by a study into the SLC24A5 gene which found that the allele associated with light skin in Europe "determined [] that 18,000 years had passed since the light-skin allele was fixed in Europeans" but may have originated as recently as 12,0006,000 years ago "given the imprecision of method" ,[22] which is in line with the earliest evidence of farming.[23]

Research by Nina Jablonski suggests that an estimated time of about 10,000 to 20,000 years is enough for human populations to achieve optimal skin pigmentation in a particular geographic area but that development of ideal skin coloration may happen faster if the evolutionary pressure is stronger, even in as little as 100 generations.[5] The length of time is also affected by cultural practices such as food intake, clothing, body coverings, and shelter usage which can alter the ways in which the environment affects populations.[7]

One of the most recently proposed drivers of the evolution of skin pigmentation in humans is based on research that shows a superior barrier function in darkly pigmented skin. Most protective functions of the skin, including the permeability barrier and the antimicrobial barrier, reside in the stratum corneum (SC) and the researchers surmise that the SC has undergone the most genetic change since the loss of human body hair. Natural selection would have favored mutations that protect this essential barrier; one such protective adaptation is the pigmentation of interfollicular epidermis, because it improves barrier function as compared to non-pigmented skin. In lush rainforests, however, where UV-B radiation and xeric stress were not in excess, light pigmentation would not have been nearly as detrimental. This explains the side-by-side residence of lightly pigmented and darkly pigmented peoples.[19]

Population and admixture studies suggest a three-way model for the evolution of human skin color, with dark skin evolving in early hominids in Africa and light skin evolving partly separately at least two times after modern humans had expanded out of Africa.[20][24][25][26][27][28]

For the most part, the evolution of light skin has followed different genetic paths in Western and Eastern Eurasian populations. Two genes however, KITLG and ASIP, have mutations associated with lighter skin that have high frequencies in Eurasian populations and have estimated origin dates after humans spread out of Africa but before the divergence of the two lineages.[26]

The understanding of the genetic mechanisms underlying human skin color variation is still incomplete; however, genetic studies have discovered a number of genes that affect human skin color in specific populations, and have shown that this happens independently of other physical features such as eye and hair color. Different populations have different allele frequencies of these genes, and it is the combination of these allele variations that bring about the complex, continuous variation in skin coloration we can observe today in modern humans. Population and admixture studies suggest a 3-way model for the evolution of human skin color, with dark skin evolving in early hominids in sub-Saharan Africa and light skin evolving independently in Europe and East Asia after modern humans had expanded out of Africa.[20][24][25][26][27][28]

For skin color, the broad sense heritability (defined as the overall effect of genetic vs. nongenetic factors) is very high, provided one is able to control for the most important nongenetic factor, exposure to sunlight. Many aspects of the evolution of human skin and skin color can be reconstructed using comparative anatomy, physiology, and genomics. Enhancement of thermal sweating was a key innovation in human evolution that allowed maintenance of homeostasis (including constant brain temperature) during sustained physical activity in hot environments. Dark skin evolved pari passu with the loss of body hair and was the original state for the genus Homo. Melanin pigmentation is adaptive and has been maintained by natural selection. In recent prehistory, humans became adept at protecting themselves from the environment through clothing and shelter, thus reducing the scope for the action of natural selection on human skin.[31] Credit for describing the relationship between latitude and skin color in modern humans is usually ascribed to an Italian geographer, Renato Basutti, whose widely reproduced "skin color maps" illustrate the correlation of darker skin with equatorial proximity. More recent studies by physical anthropologists have substantiated and extended these observations; a recent review and analysis of data from more than 100 populations (Relethford 1997) found that skin reflectance is lowest at the equator, then gradually increases, about 8% per 10 of latitude in the Northern Hemisphere and about 4% per 10 of latitude in the Southern Hemisphere. This pattern is inversely correlated with levels of UV irradiation, which are greater in the Southern than in the Northern Hemisphere. An important caveat is that we do not know how patterns of UV irradiation have changed over time; more importantly, we do not know when skin color is likely to have evolved, with multiple migrations out of Africa and extensive genetic interchange over the last 500,000 years (Templeton 2002).Regardless, most anthropologists accept the notion that differences in UV irradiation have driven selection for dark human skin at the equator and for light human skin at greater latitudes. What remains controversial are the exact mechanisms of selection. The most popular theory posits that protection offered by dark skin from UV irradiation becomes a liability in more polar latitudes due to vitamin D deficiency (Murray 1934). UVB (short-wavelength UV) converts 7-dehydrocholesterol into an essential precursor of cholecaliferol (vitamin D3); when not otherwise provided by dietary supplements, deficiency for vitamin D causes rickets, a characteristic pattern of growth abnormalities and bony deformities. An oft-cited anecdote in support of the vitamin D hypothesis is that Arctic populations whose skin is relatively dark given their latitude, such as the Inuit and the Lapp, have had a diet that is historically rich in vitamin D. Sensitivity of modern humans to vitamin D deficiency is evident from the widespread occurrence of rickets in 19th-century industrial Europe, but whether dark-skinned humans migrating to polar latitudes tens or hundreds of thousands of years ago experienced similar problems is open to question. In any case, a risk for vitamin D deficiency can only explain selection for light skin. Among several mechanisms suggested to provide a selective advantage for dark skin in conditions of high UV irradiation (Loomis 1967; Robins 1991; Jablonski and Chaplin 2000), the most tenable are protection from sunburn and skin cancer due to the physical barrier imposed by epidermal melanin.[32]

All modern humans share a common ancestor who lived around 200,000 years ago in Africa.[33] Comparisons between known skin pigmentation genes in chimpanzees and modern Africans show that dark skin evolved along with the loss of body hair about 1.2 million years ago and that this common ancestor had dark skin.[34] Investigations into dark-skinned populations in South Asia and Melanesia indicate that skin pigmentation in these populations is due to the preservation of this ancestral state and not due to new variations on a previously lightened population.[10][35]

For the most part, the evolution of light skin has followed different genetic paths in European and East Asian populations. Two genes, however, KITLG and ASIP, have mutations associated with lighter skin that have high frequencies in both European and East Asian populations. They are thought to have originated after humans spread out of Africa but before the divergence of the European and Asian lineages around 30,000 years ago.[26] Two subsequent genome-wide association studies found no significant correlation between these genes and skin color, and suggest that the earlier findings may have been the result of incorrect correction methods and small panel sizes, or that the genes have an effect too small to be detected by the larger studies.[37][38]

A number of genes have been positively associated with the skin pigmentation difference between European and non-European populations. Mutations in SLC24A5 and SLC45A2 are believed to account for the bulk of this variation and show very strong signs of selection. A variation in TYR has also been identified as a contributor.

Research indicates the selection for the light-skin alleles of these genes in Europeans is comparatively recent, having occurred later than 20,000 years ago and perhaps as recently as 12,000 to 6,000 years ago.[26] In the 1970s, Luca Cavalli-Sforza suggested that the selective sweep that rendered light skin ubiquitous in Europe might be correlated with the advent of farming and thus have taken place only around 6,000 years ago;[22] This scenario found support in a 2014 analysis of mesolithic (7,000 years old) hunter-gatherer DNA from La Braa, Spain, which showed a version of these genes not corresponding with light skin color.[49] In 2015 researchers analysed for light skin genes in the DNA of 94 ancient skeletons ranging from 8,000 to 3,000 years old from Europe and Russia. They found c. 8,000-year-old hunter-gatherers in Spain, Luxembourg, and Hungary were dark skinned while similarly aged hunter gatherers in Sweden were light skinned (having predominately derived alleles of SLC24A5, SLC45A2 and also HERC2/OCA2). Neolithic farmers entering Europe at around the same time were intermediate, being nearly fixed for the derived SLC24A5 variant but only having the derived SLC45A2 allele in low frequencies. The SLC24A5 variant spread very rapidly throughout central and southern Europe from about 8,000 years ago, whereas the light skin variant of SLC45A2 spread throughout Europe after 5,800 years ago.[50][51]

A number of genes known to affect skin color have alleles that show signs of positive selection in East Asian populations. Of these, only OCA2 has been directly related to skin color measurements, while DCT, MC1R and ATRN are marked as candidate genes for future study.

Tanning response in humans is controlled by a variety of genes. MC1R variants Arg151Sys (rs1805007[71]), Arg160Trp (rs1805008[72]), Asp294Sys (rs1805009[73]), Val60Leu (rs1805005[74]) and Val92Met (rs2228479[75]) have been associated with reduced tanning response in European and/or East Asian populations. These alleles show no signs of positive selection and only occur in relatively small numbers, reaching a peak in Europe with around 28% of the population having at least one allele of one of the variations.[35][76] A study of self-reported tanning ability and skin type in American non-Hispanic Caucasians found that SLC24A5 Phe374Leu is significantly associated with reduced tanning ability and also associated TYR Arg402Gln (rs1126809[77]), OCA2 Arg305Trp (rs1800401[78]) and a 2-SNP haplotype in ASIP (rs4911414[79] and rs1015362[80]) to skin type variation within a "fair/medium/olive" context.[81]

Oculocutaneous albinism (OCA) is a lack of pigment in the eyes, skin and sometimes hair that occurs in a very small fraction of the population. The four known types of OCA are caused by mutations in the TYR, OCA2, TYRP1, and SLC45A2 genes.[82]

In hominids, the parts of the body not covered with hair, like the face and the back of the hands, start out pale in infants and turn darker as the skin is exposed to more sun. All human babies are born pale, regardless of what their adult color will be. In humans, melanin production does not peak until after puberty.[7]

The skin of children becomes darker as they go through puberty and experience the effects of sex hormones.[83] This darkening is especially noticeable in the skin of the nipples, the areola of the nipples, the labia majora in females, and the scrotum in males. In some people, the armpits become slightly darker during puberty. The interaction of genetic, hormonal, and environmental factors on skin coloration with age is still not adequately understood, but it is known that men are at their darkest baseline skin color around the age of 30, without considering the effects of tanning. Around the same age, women experience darkening of some areas of their skin.[7]

Human skin color fades with age. Humans over the age of thirty experience a decrease in melanin-producing cells by about 10% to 20% per decade as melanocyte stem cells gradually die.[84] The skin of face and hands has about twice the amount of pigment cells as unexposed areas of the body, as chronic exposure to the sun continues to stimulate melanocytes. The blotchy appearance of skin color in the face and hands of older people is due to the uneven distribution of pigment cells and to changes in the interaction between melanocytes and keratinocytes.[7]

It has been observed that females are found to have lighter skin pigmentation than males in some studied populations.[10] This may be a form of sexual dimorphism due to the requirement in women for high amounts of calcium during pregnancy and lactation. Breastfeeding newborns, whose skeletons are growing, require high amounts of calcium intake from the mother's milk (about 4 times more than during prenatal development),[85] part of which comes from reserves in the mother's skeleton. Adequate vitamin D resources are needed to absorb calcium from the diet, and it has been shown that deficiencies of vitamin D and calcium increase the likelihood of various birth defects such as spina bifida and rickets. Natural selection may have led to females with lighter skin than males in some indigenous populations because women must get enough vitamin D and calcium to support the development of fetus and nursing infants and to maintain their own health.[7] However, in some populations such as in Italy, Poland, Ireland, Spain and Portugal men are found to have fairer complexions, and this has been ascribed as a cause to increased melanoma risk in men.[86][87] Similarly, studies done in the late 19th Century/early 20th Century in Europe also conflicted with the notion at least in regards to Northern Europeans. The studies found that in England women tend to have darker hair, eyes, and skin complexation than men, and in particular women darken in relation to men during puberty.[88] A study in Germany during this period showed that German men were more likely to have lighter skin, blond hair, and lighter eyes, while German women had darker hair, eyes and skin tone on average.[89]

The sexes also differ in how they change their skin color with age. Men and women are not born with different skin color, they begin to diverge during puberty with the influence of sex hormones. Women can also change pigmentation in certain parts of their body, such as the areola, during the menstrual cycle and pregnancy and between 50 and 70% of pregnant women will develop the "mask of pregnancy" (melasma or chloasma) in the cheeks, upper lips, forehead, and chin.[7] This is caused by increases in the female hormones estrogen and progesterone and it can develop in women who take birth control pills or participate in hormone replacement therapy.[90]

Uneven pigmentation of some sort affects most people, regardless of bioethnic background or skin color. Skin may either appear lighter, or darker than normal, or lack pigmentation at all; there may be blotchy, uneven areas, patches of brown to gray discoloration or freckling. Apart from blood-related conditions such as jaundice, carotenosis, or argyria, skin pigmentation disorders generally occur because the body produces either too much or too little melanin.

Some types of albinism affect only the skin and hair, while other types affect the skin, hair and eyes, and in rare cases only the eyes. All of them are caused by different genetic mutations. Albinism is a recessively inherited trait in humans where both pigmented parents may be carriers of the gene and pass it down to their children. Each child has a 25% chance of being albino and a 75% chance of having normally pigmented skin.[91] One common type of albinism is oculocutaneous albinism or OCA, which has many subtypes caused by different genetic mutations.Albinism is a serious problem in areas of high sunlight intensity, leading to extreme sun sensitivity, skin cancer, and eye damage.[7]

Albinism is more common in some parts of the world than in others, but it is estimated that 1 in 70 humans carry the gene for OCA.The most severe type of albinism is OCA1A, which is characterized by complete, lifelong loss of melanin production, other forms of OCA1B, OCA2, OCA3, OCA4, show some form of melanin accumulation and are less severe.[7] The four known types of OCA are caused by mutations in the TYR, OCA2, TYRP1, and SLC45A2 genes.[82]

Albinos often face social and cultural challenges (even threats), as the condition is often a source of ridicule, racism, fear, and violence. Many cultures around the world have developed beliefs regarding people with albinism. Albinos are persecuted in Tanzania by witchdoctors, who use the body parts of albinos as ingredients in rituals and potions, as they are thought to possess magical power.[92]

Vitiligo is a condition that causes depigmentation of sections of skin. It occurs when melanocytes die or are unable to function. The cause of vitiligo is unknown, but research suggests that it may arise from autoimmune, genetic, oxidative stress, neural, or viral causes.[93] The incidence worldwide is less than 1%.[94] Individuals affected by vitiligo sometimes suffer psychological discomfort because of their appearance.[7]

Increased melanin production, also known as hyperpigmentation, can be a few different phenomena:

Aside from sun exposure and hormones, hyperpigmentation can be caused by skin damage, such as remnants of blemishes, wounds or rashes.[95] This is especially true for those with darker skin tones.

The most typical cause of darkened areas of skin, brown spots or areas of discoloration is unprotected sun exposure. Once incorrectly referred to as liver spots, these pigment problems are not connected with the liver.

On lighter to medium skin tones, solar lentigenes emerge as small- to medium-sized brown patches of freckling that can grow and accumulate over time on areas of the body that receive the most unprotected sun exposure, such as the back of the hands, forearms, chest, and face. For those with darker skin colors, these discolorations can appear as patches or areas of ashen-gray skin.

Melanin in the skin protects the body by absorbing solar radiation. In general, the more melanin there is in the skin the more solar radiation can be absorbed. Excessive solar radiation causes direct and indirect DNA damage to the skin and the body naturally combats and seeks to repair the damage and protect the skin by creating and releasing further melanin into the skin's cells. With the production of the melanin, the skin color darkens, but can also cause sunburn. The tanning process can also be created by artificial UV radiation.

There are two different mechanisms involved. Firstly, the UVA-radiation creates oxidative stress, which in turn oxidizes existing melanin and leads to rapid darkening of the melanin, also known as IPD (immediate pigment darkening). Secondly, there is an increase in production of melanin known as melanogenesis.[96] Melanogenesis leads to delayed tanning and first becomes visible about 72 hours after exposure. The tan that is created by an increased melanogenesis lasts much longer than the one that is caused by oxidation of existing melanin. Tanning involves not just the increased melanin production in response to UV radiation but the thickening of the top layer of the epidermis, the stratum corneum.[7]

A person's natural skin color affects their reaction to exposure to the sun. Generally, those who start out with darker skin color and more melanin have better abilities to tan. Individuals with very light skin and albinos have no ability to tan.[97] The biggest differences resulting from sun exposure are visible in individuals who start out with moderately pigmented brown skin: the change is dramatically visible as tan lines, where parts of the skin which tanned are delineated from unexposed skin.[7]

Modern lifestyles and mobility have created mismatch between skin color and environment for many individuals. Vitamin D deficiencies and UVR overexposure are concerns for many. It is important for these people individually to adjust their diet and lifestyle according to their skin color, the environment they live in, and the time of year.[7] For practical purposes, such as exposure time for sun tanning, six skin types are distinguished following Fitzpatrick (1975), listed in order of decreasing lightness:

The following list shows the six categories of the Fitzpatrick scale in relation to the 36 categories of the older von Luschan scale:[98][99]

Dark skin with large concentrations of melanin protects against ultraviolet light and skin cancers; light-skinned people have about a tenfold greater risk of dying from skin cancer, compared with dark-skinned persons, under equal sunlight exposure. Furthermore, UV-A rays from sunlight are believed to interact with folic acid in ways that may damage health.[100] In a number of traditional societies the sun was avoided as much as possible, especially around noon when the ultraviolet radiation in sunlight is at its most intense. Midday was a time when people stayed in the shade and had the main meal followed by a nap, a practice similar to the modern siesta.

Approximately 10% of the variance in skin color occurs within regions, and approximately 90% occurs between regions.[101] Because skin color has been under strong selective pressure, similar skin colors can result from convergent adaptation rather than from genetic relatedness; populations with similar pigmentation may be genetically no more similar than other widely separated groups. Furthermore, in some parts of the world where people from different regions have mixed extensively, the connection between skin color and ancestry has substantially weakened.[102] In Brazil, for example, skin color is not closely associated with the percentage of recent African ancestors a person has, as estimated from an analysis of genetic variants differing in frequency among continent groups.[103]

In general, people living close to the equator are highly darkly pigmented, and those living near the poles are generally very lightly pigmented. The rest of humanity shows a high degree of skin color variation between these two extremes, generally correlating with UV exposure. The main exception to this rule is in the New World, where people have only lived for about 10,000 to 15,000 years and show a less pronounced degree of skin pigmentation.[7]

In recent times, humans have become increasingly mobile as a consequence of improved technology, domestication, environmental change, strong curiosity, and risk-taking. Migrations over the last 4000 years, and especially the last 400 years, have been the fastest in human history and have led to many people settling in places far away from their ancestral homelands. This means that skin colors today are not as confined to geographical location as they were previously.[7]

According to classical scholar Frank Snowden, skin color did not determine social status in ancient Egypt, Greece or Rome. These ancient civilizations viewed relations between the major power and the subordinate state as more significant in a person's status than their skin colors.[104][pageneeded]

Nevertheless, some social groups favor specific skin coloring. The preferred skin tone varies by culture and has varied over time. A number of indigenous African groups, such as the Maasai, associated pale skin with being cursed or caused by evil spirits associated with witchcraft. They would abandon their children born with conditions such as albinism and showed a sexual preference for darker skin.[105]

Many cultures have historically favored lighter skin for women. Before the Industrial Revolution, inhabitants of the continent of Europe preferred pale skin, which they interpreted as a sign of high social status. The poorer classes worked outdoors and got darker skin from exposure to the sun, while the upper class stayed indoors and had light skin. Hence light skin became associated with wealth and high position.[106] Women would put lead-based cosmetics on their skin to whiten their skin tone artificially.[107] However, when not strictly monitored, these cosmetics caused lead poisoning. Other methods also aimed at achieving a light-skinned appearance, including the use of arsenic to whiten skin, and powders. Women would wear full-length clothes when outdoors, and would use gloves and parasols to provide shade from the sun.

Colonization and enslavement as carried out by European countries became involved with colorism and racism, associated with the belief that people with dark skin were uncivilized, inferior, and should be subordinate to lighter-skinned invaders. This belief exists to an extent in modern times as well.[108] Institutionalized slavery in North America led people to perceive lighter-skinned African-Americans as more intelligent, cooperative, and beautiful.[109] Such lighter-skinned individuals had a greater likelihood of working as house slaves and of receiving preferential treatment from plantation owners and from overseers. For example, they had a chance to get an education.[110] The preference for fair skin remained prominent until the end of the Gilded Age, but racial stereotypes about worth and beauty persisted in the last half of the 20th century and continue in the present day. African-American journalist Jill Nelson wrote that, "To be both prettiest and black was impossible,"[111] and elaborated:

We learn as girls that in ways both subtle and obvious, personal and political, our value as females is largely determined by how we look. ... For black women, the domination of physical aspects of beauty in women's definition and value render us invisible, partially erased, or obsessed, sometimes for a lifetime, since most of us lack the major talismans of Western beauty. Black women find themselves involved in a lifelong effort to self-define in a culture that provides them no positive reflection.[111]

A preference for fair or lighter skin continues in some countries, including Latin American countries where whites form a minority.[112] In Brazil, a dark-skinned person is more likely to experience discrimination.[113] Many actors and actresses in Latin America have European featuresblond hair, blue eyes, and pale skin.[114][115] A light-skinned person is more privileged and has a higher social status;[115] a person with light skin is considered more beautiful[115] and lighter skin suggests that the person has more wealth.[115] Skin color is such an obsession in some countries that specific words describe distinct skin tones - from (for example) "jincha", Puerto Rican slang for "glass of milk" to "morena", literally "brown".[115]

In South Asia, society regards pale skin as more attractive and associates dark skin with lower class status; this results in a massive market for skin-whitening creams.[116] Fairer skin-tones also correlate to higher caste-status in the Hindu social orderalthough the system is not based on skin tone.[117] Actors and actresses in Indian cinema tend to have light skin tones, and Indian cinematographers have used graphics and intense lighting to achieve more "desirable" skin tones.[118] Fair skin tones are advertised as an asset in Indian marketing.[119]

Skin-whitening products have remained popular over time, often due to historical beliefs and perceptions about fair skin. Sales of skin-whitening products across the world grew from $40 billion to $43 billion in 2008.[120] In South and East Asian countries, people have traditionally seen light skin as more attractive, and a preference for lighter skin remains prevalent. In ancient China and Japan, for example, pale skin can be traced back to ancient drawings depicting women and goddesses with fair skin tones.[citation needed] In ancient China, Japan, and Southeast Asia, pale skin was seen as a sign of wealth. Thus skin-whitening cosmetic products are popular in East Asia.[121] Four out of ten women surveyed in Hong Kong, Malaysia, the Philippines and South Korea used a skin-whitening cream, and more than 60 companies globally compete for Asia's estimated $18 billion market.[122] Changes in regulations in the cosmetic industry led to skin-care companies introducing harm-free skin lighteners. In Japan, the geisha have a reputation for their white-painted faces, and the appeal of the bihaku (), or "beautiful white", ideal leads many Japanese women to avoid any form of tanning.[123] There are exceptions to this, with Japanese fashion trends such as ganguro emphasizing tanned skin. Skin whitening is also not uncommon in Africa,[124][125] and several research projects have suggested a general preference for lighter skin in the African-American community.[126] In contrast, one study on men of the Bikosso tribe in Cameroon found no preference for attractiveness of females based on lighter skin color, bringing into question the universality of earlier studies that had exclusively focused on skin-color preferences among non-African populations.[127]

Significant exceptions to a preference for lighter skin started to appear in Western culture in the mid-20th century.[128] However a 2010 study found a preference for lighter-skinned women in New Zealand and California.[129] Though sun-tanned skin was once associated with the sun-exposed manual labor of the lower class, the associations became dramatically reversed during this timea change usually credited to the trendsetting Frenchwoman Coco Chanel (18831971) presenting tanned skin as fashionable, healthy, and luxurious.[130] As of 2017[update], though an overall preference for lighter skin remains prevalent in the United States, many within the country regard tanned skin as both more attractive and healthier than pale or very dark skin.[131][132][133] Western mass media and popular culture continued[when?] to reinforce negative stereotypes about dark skin,[134] but in some circles pale skin has become associated with indoor office-work while tanned skin has become associated with increased leisure time, sportiness and good health that comes with wealth and higher social status.[106] Studies have also emerged indicating that the degree of tanning is directly related to how attractive a young woman is.[135][136]

Continue reading here:
Human skin color - Wikipedia

The skin is a crucial part of the body and serves as a defense against external environmental elements such as exposure to sunlight, extreme heator cold, dust, and bacterial infection. Oxidative activity occurs during the metabolism of human tissues and is a natural and inevitable part of the aging process of the skin. Free radicals with one or more unpaired electrons and a reactive state are produced as a result of the oxidative process. The skin has its antioxidant defense against this oxidation process in the extracellular space, organelles, and subcellular compartments [1]. The use of donated skin from healthy homozygotic twins may help avoid these problems. Bauer published the first successful case of skin transplantation between homozygotic twins in 1927 [2]. One of the primary health problems that significantly affect many different groups of people and varies in age and intensity is burns. Despite improvements in nonsurgical and surgical burn treatments, the patient's look continues to be a public health concern. Skin transplantation is still regarded as the gold standard for surgical burn therapy. The availability of skin for grafting is one of the main challenges in burn surgery. Regarding nonsurgical treatment, a variety of skin dressings or alternatives are still an option [3].

Additionally, biologics have been used to treat kids with allergic skin conditions. Benralizumab and dupilumab are authorized for patients older than 12 years, whereas omalizumab and mepolizumab are authorized for youngsters as old as six years. Reslizumab is only permitted for patients older than 18 years. In eligible people, these identicalantibodies may be introduced if asthma or reactive skin conditions are not effectively controlled [4]. The expression of genes capable of immunoregulatory function may lessen allograft rejection. Recent research suggests that viral interleukin (IL)-10 is one of the most effective ways to prevent rejection since it can lower the immune response during allotransplantation[5].

Tissue donation is protected by the Medical (Therapy, Educational, and Research) Act in Singapore. Reviewing the demographic and psychosocial characteristics that may generate hesitancy or unwillingness among healthcare providers is the goal of this study. A questionnaire-based survey with 18 items was carried out at the National Heart Centre of Singapore and the Singapore General Hospital. A total of 521 people took part in the survey. There were descriptive statistics run for the participant's demographics, the motivating elements behind tissue donation, motivating factors for discussing tissue donation, and causes for doubt or reluctance to donate tissue to a close relative. Fisher's exact testand Pearson's chi-square testwere used to analyze any connections that may exist among various factors and the support for tissue donation [6].

The disease known as bacteremia, or the infection of bacteria in the blood, has a high mortality rate. High rates of morbidity are linked to it. The patient's age, underlying health, and aggressiveness of the infective organism all influence the prognosis. Transfusion-transmitted infections are a rare cause of bacteremia, notwithstanding how challenging it can be to pinpoint the origin of the condition. Between one per 100,000 and one per 1,000,000 pack red blood cells or between one per 900,000 and one per 100,000platelets are the expected incidences of bacterial spreading through donated blood. One in eight million red blood cells and one in 50,000 to 500,000 white blood cells result in fatalities. Because frozen platelets are thawed and kept at room temperature before being infused, there is a chance for any pathogens that may be present to grow before the substance is transfused, which is assumed to be the source of the greater rates of platelet transfusion. Making sure that blood used for transfusions is free of toxins is essential for further lowering infection rates. One method for accomplishing this is by meticulously preparing and washing a donor's skin at the location of the collection [7].

Across the world, skin allografts are used to temporarily replace missing or damaged skin. Skin contamination that occurs naturally might also be introduced during recovery or processing. The recipients of allografts may be at risk due to this contamination. Allografts must be cultured for bacteria and disinfected, although the specific procedures and methods are not required by standards. Twelve research publications that examined the bioburden reduction techniques of skin grafts were found in a comprehensive evaluation of the literature from three databases. The most commonly mentioned disinfection technique that demonstrated lower contamination rates was the utilization of broad-range antibiotics and antifungal medicines. It was found that using 0.1% peracetic acidor 25 kGy of mid-infraredirradiation at cooler temperatures resulted in the largest decrease in skin transplant contamination rates [8].

Skin, the uppermost organ that protects the human body, is the surface upon which different environmental signals have the most immediate impact [9]. The number, quality, and distribution of melanin pigments produced by melanocytes determine the color of human skin, eyes, and hair, as well as how well they shield the skin from harmful ultraviolet (UV) rays and oxidative stress caused by numerous environmental pollutants. Melanocyte stem cells in the region of the follicular bulge replace melanocytes, which are located in the skin's layer of the interfollicular epidermis. Skin inflammation is brought on by a variety of stressors, including eczema, microbial infection, UV light exposure, mechanical injury, and aging [10]. Skin surface lipid(SSL) composition primarily reflects sebaceous secretion in the skin regions with the highest intensity of sebum (forehead, chest, and dorsum), which also flows from those sites to regions with lower concentrations, where the participation of cellular molecules rich in linoleic and oleic acid becomes more important [11]. Surgically removed skin from individuals who underwent a body contouring procedure was combined with discarded skin from excess belt lipectomies, breast reductions, and body lifts. After applying traction to both ends of the excised section, meshing by 3:1 plates, and covering with Vaseline gauze coated in an antiseptic solution prepared for burn covering, it can be removed by a dermatome. All patients in group III received a skin allograft from a living first-degree family (father, mother, brother, or sister), as they share about 50% of their DNA [12].

The principal goal is to evaluate the results of skin care therapies, like emollients, for the primary prevention of food allergy and eczema in babies. A secondary goal is to determine whether characteristics of study populations, such as age, inherited risks, and adherence to interventions, are connected to the most beneficial or harmful treatment outcomes for both eczema and food allergies [13].

Vitamin C supports the skin's ability to scavenge free radicals and act as an infection barrier, possibly protecting against environmental oxidative stress. In phagocytic cells, such as neutrophils, an accumulation of vitamin C can encourage chemotaxis, phagocytosis, the generation of reactive oxygen species, and ultimately the death of microbes. Neutrophils eventually undergo apoptosis and are cleared by macrophages, resulting in the resolution of the inflammatory response. However, in chronic, non-healing wounds, such as those observed in diabetics, the neutrophils persist and instead undergo necrotic cell death, which can perpetuate the inflammatory response and hinder wound healing. Vitamin C's function in lymphocytes is less apparent; however, studies have indicated that it promotes B- and T-cell differentiation and proliferation, perhaps as a result of its gene-regulating properties. A lack of vitamin C lowers immunity and increases illness susceptibility [14]. The skin's distinctive form reflects the fact that its main purpose is to protect the body from the environment's irritants. The inner dermal layer, which ensures strength and suppleness, feeds the epidermis the nutrients, and also the outer epidermal layer, which is incredibly cellular and acts as a barrier, are the two layers that make up the skin. Normal skin contains high levels of vitamin C, which supports a variety of well-known and important activities, such as boosting collagen synthesis and helping the body's defense mechanisms against UV-induced photodamage. This information is occasionally used as support for introducing vitamin C to therapies; however, there is no evidence that doing so is more beneficial than just increasing dietary vitamin C intake [15].

Allograft donor selection has been affected by the worry that HIV could be transmitted through the skin of an allograft. To establish the potential presence of HIV at the period of donation, there is, however, no conclusive diagnostic test available. We examine the prevalence of HIV in human tissue, consider the potential for HIV transmission through the transplant of humanallograft skin, and talk about the validity of current HIV testing to uncover solutions to enhance skin banks' HIV donor screening procedures. The risk of HIV transmission to severely burned patients could be reduced by using the polymerase chain reactionsas a fast detection methodfor HIV, with skin biopsies in conjunction with standard regular HIV blood screening tests [16].

A total of 262 dead donor skin allograft contributions were made during the past 10 years. The response revealed a considerable improvement after the community received counseling. Most of the donors were over 70 years, and most of the recruitment was done at home. In 10 years, 165 patients received tissue allografts from 249 donors. With seven deaths out of 151 recipients who had burn injuries, the outcome was good [17]. An injury to the tissue caused by electrical, thermal,chemical, cold, or radiation stress is referred to as a "burn." The skin's ability to repair and regenerate itself is hampered by deep wounds that produce dermal damage. Skin autografting is currently the gold standard of care for burn excision, but if the patient lacks donor skin or the wound is not suitable for autografting, the use of temporary bandages or skin substitutes may be absolutely necessary to hasten wound healing, lessen discomfort, avoid infection, and minimize aberrant scarring. Among the options are xenografts, cultured epithelial cells, allografts from deceased donors, and bioartificial skin replacements [18].

In the "developed" world's burn units, "early closure" in burn wounds means removing the burned tissues and replacing them within the first "five" post-burn days with graft or their substitutes. Acceptability of this method, however, may be hampered by a general lack of education and a lack of health education among the citizens in "developing" countries. A lack of dedicated and well-trained burns surgeons might make things worse. One of the growing Gulf nations in the Middle East is the Sultanate of Oman, where in November 1997, the National Burns Center at Khoula Hospital debuted "early" surgery, which quickly became a standard technique for managing burn wounds [19]. Major burn wounds that are promptly excised heal faster, are less infectious, and have a higher chance of survival. The best way to permanently heal these wounds is with the immediate application of autograft skin. However, temporary closure using a number of treatments can assist lower evaporative loss, ward off infection, alleviate discomfort, and minimize metabolic stress when donor skin harvesting is not possible or wounds are not yet suitable for autografting. The gold for such closure is fresh cadaver allograft, although alternative materials are now available, including frozen cadaver tissue, xenografts, and a number of synthetic goods. This study examines the physiology, product categories, and applications [20].

Large burn wounds are challenging to treat and heal. To help with this procedure, several engineered skin replacements have been created. These alternatives were created with specific goals in mind, which define the situations in which they may and should be used to enhance healing or get the burn site ready for autograft closure in the end. This article analyses some of the current skin replacements in use and explores some of the justifications for their usage. According to current viewpoints, the usage of skin substitutes is still in the early stages, and it will take some time before it is evident how they should be used in therapeutic settings [21].

Each skin layer has a different width based on where in the body it is located due to differences within the thicknesses of the dermal and epidermal layers. The stratum lucidum, a second layer, is what gives the palms of the hand and the soles of the feet their thickest epidermis. Although it is thought that the upper back has the thickest dermis, histologically speaking, the upper back is regarded to just have "thin skin" since that lacks thestratum lucidum layer and has a thinner epidermis as hairless skin [22].

We provide a rare instance of an individual who underwent satisfactory allogeneic split-thickness skin graft (STSG) transplanting and had previously undergone a bone marrow stem cell transplant. Hodgkin's bone marrow transplant (BMT) had already been done on the patient because of the myelodysplasia and non-lymphoma. Human leukocyte antigen(HLA) typing performed prior to BMT allowed for the identification of the donor and recipient, who were siblings (not twins). We achieved complete donor chimerism. Scleroderma, ichthyosis-like dryness, and severe chronic graft-versus-host disease (cGvHD) were all present in the recipient. Scalp ulceration with full thickness resulted from folliculitis. An STSG was removed under local anesthesia from the donor sister's femoral area and then transplanted into the recipient's prepared scalp ulcer without any additional anesthesia [23]. We conducted an allogeneic donor skin transplant in seven adult patients following allogeneic hematopoietic stem transplant surgery for cGvHD-associated refractory skin ulcers. Serious cGvHD-related refractory skin ulcers continue to be linked with significant morbidity and mortality. While split skin grafts (SSG) were performed on four patients, a full-thickness skin transplant was performed on one patient for two tiny, refractory ankle ulcers, and one patient got in vitro extended donor keratinocyte grafts made from the original unrelated donor's hair roots. An extensive deep fascial defect of the lower leg was first filled with an autologous larger omentum-free graft in one more patient before being filled with an allogeneic SSG (Figure 1) [24].

Three skin grafting innovations led to significant improvements in the care for burn injuries. Firstly, it was discovered that the dermal layeris the most crucial component of graft in creating a new, durable, resilient surface. Secondly, it was shown that deep islands of hair follicles and sebaceous gland epithelium regrow at the donor site following the excision of a partial-thickness graft, allowing grafts to be cut thicker rather than as thin as feasible. The dermis might be transplanted without having to be as thin as feasible disrupting the areas of healing. When the grafts were thicker, it was possible to build tools for cutting bigger grafts. The split-thickness graftwas the name given to these bigger grafts, and for the first in terms of square feet, it took a long time to effectively resurface big regions instead of millimeters square [25]. Skin banking was introduced in 1994 by the Melbourne-based Donor Tissue Bank of Victoria (DTBV). It is still the only skin bank in operation in Australia, processing cadaveric skin that has been cryopreserved for use in treating burns. Since the program's creation, there has been a steady rise in the demand for transplanted skin in Australia. Several major incidents or calamities, in both Australia and overseas, required the bank to provide aid. Demand is always greater than supply, thus the DTBV had to come up with measures to enhance the availability of allograft skin on a national level since there were no other local skin banks [26]. The treatment of individuals with severe burns may benefit greatly from cadaveric allograft skin. Estimating the present popularity and levels of usage of transplant skin in the US, however, is challenging. In the American Burn Association's Directory of Burn Care Resources for North America 1991-1992, which lists 140 medical directors of US burn centers and 40 skin banks, a poll of these individuals was conducted. For skin bank and burn directors, respectively, the number of responses was 45% and 38%. At the participating burn centers, 12% of patients who were hospitalized received treatment with allograft skin. Although just 47% of skin banks could provide fresh cadaver skin, 69%of burn center directors opted to utilize fresh skin. This study, which was presented to a Tissue Bank Special Interest group at the American Burns Association annual meeting in 1993, tabulated survey results as well as a review and discussion of potential future directions of replacement andskin banking research [27].

A possible substitute for human cadaveric allografts (HCA)in the treatment of severely burned patients is pig xenografts that have undergone genetic engineering. However, if preservation and lengthy storage, without cellular viability loss, were possible, their therapeutic utility would be greatly increased. This study's goal was to determine the direct effects of cryopreservation and storage time on vital in vivo and in vitro characteristics that are required for an effective, perhaps equal replacement for HCA. In this study, viable porcine skin grafts that had been constantly frozen for more than seven years were contrasted with similarly prepared skin grafts that had been kept frozen for only 15 minutes [28]. When freshly collected allogeneic skin grafts are not available, it is thought that frozen humanallogeneic skin grafts are a viable substitute. However, there is little functional and histological knowledge on how cryopreservation affects allogeneic skin transplants, particularly those that overcome mismatched histocompatibility barriers. To compare fresh and frozen skin grafts across major and minor histocompatibility barriers, we used a small-scale pig model. Our findings are relevant to the existing clinical procedures requiring allogeneic grafting and they may enable future, transient wound treatments using frozen xenografts made of genetically engineered pig skin since porcine skin and human skin share several physical and immunological characteristics [29].

Peeling Skin Syndrome

The two types of peeling skin syndrome (PSS), i.e., acral PSS and generalized PSS, are uncommon autosomal recessive cutaneous genodermatoses. The general form now includes type A non-inflammatory, type B inflammatory, and type C. A single missense mutation in CHST8, the gene that codes for Golgi transmembrane N-acetylgalactosamine 4-O-sulphotransferase, results in PSS type A. As seen in our example, this mutation leads to the intracellular breakage of corneocytes, which results in asymptomatic skin peeling. Congenital ichthyosis or erythematous patches that migrate and have a peeling border are to blame for the clinical similarity between PSS type B and Netherton syndrome[30].

Chromhidrosis

Yonge described chromhidrosis for the first time in 1709. It is an uncommon disorder characterized by the discharge of colored sweat. There are three subtypes of chromhidrosis: apocrine, eccrine, and pseudochromhidrosis [31].

Necrobiosis Lipoidica

Necrobiosis lipoidica is a granulomaillness that frequently affects the lower limbs and manifests as indolent atrophic plaques. Several case studies detail various therapy options with varying degrees of effectiveness and propose potential correlations. Squamous cell carcinoma growth and ulceration are significant side effects. Despite therapy, the disease's course is frequently indolent and recurring [32].

Morgellons Disease

It is a stressful and debilitating illness to have Morgellons disease. Multiple cutaneous wounds that are not healing are a frequent presentation for patients. Patients frequently give samples to the doctor and blame the problem on protruding fibers or other things. The initial theories for the origin of this disorder ranged widely and were hotly contested, from infectious to mental [33].

Erythropoietic Protoporphyria

The final enzyme in the heme biosynthetic pathways and the cause of erythropoietic protoporphyria is ferrochelatase partial deficiency. After the first exposure to sunlight in early infancy or youth, photosensitivity develops inerythropoietic protoporphyria. There have been reports of erythropoietic protoporphyria all around the world; however, its epidemiology varies by locale. After age 10, it was discovered that 20% of the Japanese patients had erythropoietic protoporphyria symptoms [34].

Eruptive Xanthomas

Localized lipid deposits known as xanthomas are linked to lipid abnormalities and can be seen in the skin, tendons, and subcutaneous tissue. This disorder's hyperlipidemia may be brought on by a basic genetic flaw, a secondary condition, or perhaps both. Such a skin exanthem may be the initial indication of cardiovascular risk [35].

Go here to see the original:
Skin Grafting, Cryopreservation, and Diseases: A Review Article - Cureus

As the 3rd presenter during the morning session of the American Society for Dermatologic Surgery Meeting, Emerging Concepts, Saranya Wyles, MD, PhD, assistant professor of dermatology, pharmacology, and regenerative medicine in the department of dermatology at the Mayo Clinic in Rochester, Minnesota, explored the hallmarks of skin aging, the root cause of aging and why it occurs, and regenerative medicine. Wyles first began with an explanation of how health care is evolving. In 21st-century health care, there has been a shift in how medical professionals think about medicine. Traditionally,the first approach was to fight diseases, such as cancer, inflammatory conditions, or autoimmune disorders. Now, the thought process is changing to a root cause approach with a curative option and how to rebuild health. Considering how to overcome the sequence of the different medications and treatments given to patients is rooted in regenerative medicine principles.

For skin aging, there is a molecular clock that bodies follow. Within the clock are periods of genomic instability, telomere attrition, and epigenetic alterations, and Wyles lab focuses on cellular senescence.

We've heard a lot atthis conference about bio stimulators, aesthetics, and how we can stimulate our internal mechanisms of regeneration. Now, the opposite force of regeneration isthe inhibitory aging hallmarks which include cellular senescence. So, what is cell senescence? This isa state that the cell goes into, similar to apoptosis or proliferation, where the cell goesinto a cell cycle arrest so instead of dividing apoptosis, leading to cell death,the cell stays in this zombie state, said Wyles.

Senescence occurs when bodies require a mutation for cancers. When the body recognizes there is something wrong, it launches itself into the senescent state, which can be beneficial. Alternatively, chronic senescence seen with inflammageing, like different intrinsic markers, extrinsic markers, and UV damage, is a sign of late senescence. Senescence cells can be melanocytes, fibroblasts, and cells that contribute to the regeneration of the skin.

I think were in a very exciting time ofinnovation and advancements in medicine, which is the meeting of longevity science of aging and regenerative medicine, said Wyles.

Regenerative medicine is a new field of medicine that uses native and bioengineered cells, devices, and engineering platforms with the goal of healing tissues and organs byrestoring form and function through innate mechanisms of healing.Stem cell therapy and stem cell application are commonly referenced with regenerative medicine. Typically, first-in-class treatments include cells, autologous or allogeneic, different types of cells that areassociated with high-cost due to the manufacturing.

With regenerative medicine, there's a new class of manufacturing. Regenerative medicine is not like traditional drugs where every product is consistent. These are cells, so the idea of manufacturing, and minimally manipulating, all comes into play. Now, there's a new shift towards next-generation care. This is cell-free technology. So, this is the idea of exosomes, because these are now products from cells that can be directly applied, they can be shelf-stable, accessible, and more cost-effective, said Wyles.

Exosomes are the ways that the cells communicate with each other. Cells have intercellularcommunications and depending on the source of the exosomes, there can be different signals. Wyles focused specifically on a platelet product, which is a pooled platelet product that can be purified and used for different mechanisms including wound healing, fat grafting, degenerative joint disease, and more.In a cosmetic studyconducted by Mayo Clinic, a topical platelet exosome product was applied to the face in the morning and the evening. Application included a 3-step regimen, a gentle cleanser, a platelet exosomeproduct, and then a sunscreen.

After 6 weeks, there was a significant improvement in redness and a 92% improvement in the hemoglobin process. Vasculature also improved across age groups. The study enrolled 56patients, and the average age was 54. Patients in their 40s, 50s, and 60s saw consistent improvement in redness and skin aging.

Lastly, Wyles stressed that as dermatologists think through the science-driven practices of these innovative strategies for skin aging, wound healing, and other regenerative approaches, they must think about responsible conducts of research. Currently, there are no FDA indications for exosomes being injected.

Reference:

See the rest here:
The Switch to Regenerative Medicine - Dermatology Times

(SACRAMENTO)

Three babies have been born after receiving the worlds first spina bifida treatment combining surgery with stem cells. This was made possible by a landmark clinical trial at UC Davis Health.

The one-of-a-kind treatment, delivered while a fetus is still developing in the mothers womb, could improve outcomes for children with this birth defect.

Launched in the spring of 2021, the clinical trial is known formally as the CuRe Trial: Cellular Therapy for In Utero Repair of Myelomeningocele. Thirty-five patients will be treated in total.

The three babies from the trial that have been born so far will be monitored by the research team until 30 months of age to fully assess the procedures safety and effectiveness.

The first phase of the trial is funded by a $9 million state grant from the states stem cell agency, the California Institute for Regenerative Medicine (CIRM).

This clinical trial could enhance the quality of life for so many patients to come, said Emily, the first clinical trial participant who traveled from Austin, Tex. to participate. Her daughter Robbie was born last October. We didnt know about spina bifida until the diagnosis. We are so thankful that we got to be a part of this. We are giving our daughter the very best chance at a bright future.

Spina bifida, also known as myelomeningocele, occurs when spinal tissue fails to fuse properly during the early stages of pregnancy. The birth defect can lead to a range of lifelong cognitive, mobility, urinary and bowel disabilities. It affects 1,500 to 2,000 children in the U.S. every year. It is often diagnosed through ultrasound.

While surgery performed after birth can help reduce some of the effects, surgery before birth can prevent or lessen the severity of the fetuss spinal damage, which worsens over the course of pregnancy.

Ive been working toward this day for almost 25 years now, said Diana Farmer, the worlds first woman fetal surgeon, professor and chair of surgery at UC Davis Health and principal investigator on the study.

As a leader of the Management of Myelomeningocele Study (MOMS) clinical trial in the early 2000s, Farmer had previously helped to prove that fetal surgery reduced neurological deficits from spina bifida. Many children in that study showed improvement but still required wheelchairs or leg braces.

Farmer recruited bioengineer Aijun Wang specifically to help take that work to the next level. Together, they launched theUC Davis Health Surgical Bioengineering Laboratoryto find ways to use stem cells and bioengineering to advance surgical effectiveness and improve outcomes. Farmer also launched the UC Davis Fetal Care and Treatment Centerwith fetal surgeon Shinjiro Hirose and the UC DavisChildrens Surgery Center several years ago.

Farmer, Wang and their research team have been working on their novel approach using stem cells in fetal surgery for more than 10 years. Over that time, animal modeling has shown it is capable of preventing the paralysis associated with spina bifida.

Its believed that the stem cells work to repair and restore damaged spinal tissue, beyond what surgery can accomplish alone.

Preliminary work by Farmer and Wang proved that prenatal surgery combined with human placenta-derived mesenchymal stromal cells, held in place with a biomaterial scaffold to form a patch, helped lambs with spina bifida walk without noticeable disability.

When the baby sheep who received stem cells were born, they were able to stand at birth and they were able to run around almost normally. It was amazing, Wang said.

When the team refined their surgery and stem cells technique for canines, the treatment also improved the mobility of dogs with naturally occurring spina bifida.

A pair of English bulldogs named Darla and Spanky were the worlds first dogs to be successfully treated with surgery and stem cells. Spina bifida, a common birth defect in this breed, frequently leaves them with little function in their hindquarters.

By their post-surgery re-check at 4 months old, Darla and Spanky were able to walk, run and play.

When Emily and her husband Harry learned that they would be first-time parents, they never expected any pregnancy complications. But the day that Emily learned that her developing child had spina bifida was also the day she first heard about the CuRe trial.

For Emily, it was a lifeline that they couldnt refuse.

Participating in the trial would mean that she would need to temporarily move to Sacramento for the fetal surgery and then for weekly follow-up visits during her pregnancy.

After screenings, MRI scans and interviews, Emily received the life-changing news that she was accepted into the trial. Her fetal surgery was scheduled for July 12, 2021, at 25 weeks and five days gestation.

Farmer and Wangs team manufactures clinical grade stem cells mesenchymal stem cells from placental tissue in the UC Davis Healths CIRM-funded Institute for Regenerative Cures. The cells are known to be among the most promising type of cells in regenerative medicine.

The lab is aGood Manufacturing Practice(GMP) Laboratory for safe use in humans. It is here that they made the stem cell patch for Emilys fetal surgery.

Its a four-day process to make the stem cell patch, said Priya Kumar, the scientist at the Center for Surgical Bioengineering in the Department of Surgery, who leads the team that creates the stem cell patches and delivers them to the operating room. The time we pull out the cells, the time we seed on the scaffold, and the time we deliver, is all critical.

During Emilys historic procedure, a 40-person operating and cell preparation team did the careful dance that they had been long preparing for.

After Emily was placed under general anesthetic, a small opening was made in her uterus and they floated the fetus up to that incision point so they could expose its spine and the spina bifida defect. The surgeons used a microscope to carefully begin the repair.

Then the moment of truth: The stem cell patch was placed directly over the exposed spinal cord of the fetus. The fetal surgeons then closed the incision to allow the tissue to regenerate.

The placement of the stem cell patch went off without a hitch. Mother and fetus did great! Farmer said.

The team declared the first-of-its-kind surgery a success.

On Sept. 20, 2021, at 35 weeks and five days gestation, Robbie was born at 5 pounds, 10 ounces, 19 inches long via C-section.

One of my first fears was that I wouldnt be able to see her, but they brought her over to me. I got to see her toes wiggle for the first time. It was so reassuring and a little bit out of this world, Emily said.

For Farmer, this day is what she had long hoped for, and it came with surprises. If Robbie had remained untreated, she was expected to be born with leg paralysis.

It was very clear the minute she was born that she was kicking her legs and I remember very clearly saying, Oh my God, I think shes wiggling her toes! said Farmer, who noted that the observation was not an official confirmation, but it was promising. It was amazing. We kept saying, Am I seeing that? Is that real?

Both mom and baby are at home and in good health. Robbie just celebrated her first birthday.

The CuRe team is cautious about drawing conclusions and says a lot is still to be learned during this safety phase of the trial. The team will continue to monitor Robbie and the other babies in the trial until they are 6 years old, with a key checkup happening at 30 months to see if they are walking and potty training.

This experience has been larger than life and has exceeded every expectation. I hope this trial will enhance the quality of life for so many patients to come, Emily said. We are honored to be part of history in the making.

Related links

Go here to see the original:
World's first stem cell treatment for spina bifida delivered during fetal surgery - UC Davis Health

Both companies will collaborate to improve NurExone's drug development stages, from R&D to Quality Assurance

Company to host an investor webinar on Thursday, October 20th, 2022 at 11:00 AM EST

Calgary, Alberta and Oxford, United Kingdom--(Newsfile Corp. - October 12, 2022) - NurExone Biologic Inc. (TSXV: NRX) (FSE: J90) (the "Company" or "NurExone"), a biopharmaceutical company developing biologically-guided exosome therapy for patients with traumatic spinal cord injuries, is pleased to announce that the Company's wholly-owned subsidiary, NurExone Biologic Ltd., signed a non-binding Letter of Intent for a collaboration (the "Collaboration") with Nanometrix Ltd. ("Nanometrix"), a U.K.-based nanoparticle analysis company providing services to profile molecules of exosomes and their cargo.

Under the Collaboration, NurExone's exosomes and cargo samples will be processed and analyzed by Nanometrix, which will use its proprietary Artificial Intelligence (AI) software to extract and analyze morphological and population data to achieve detailed molecular profiling of the exosomes and quantify the siRNA cargo copy number per extracellular vesicle (EV), information which was far out of reach.

"Detailed molecular profiling of our exosomes and their siRNA cargo will facilitate a quality assurance program for repeatable, mass-production of ExoTherapies towards commercialization," said Dr. Lior Shaltiel, CEO of NurExone. "Nanometrix has the expertise and resources to perform this analysis in a highly professional manner and we look forward to working with them."

"The signing of this letter of intent is a first step towards a great milestone for Nanometrix," said Alexandre Kitching, CEO and Cofounder of Nanometrix. "We are thrilled to start this collaboration with NurExone as we believe in the future of exosomes as an advanced platform for drug delivery. We look forward to deploying our technology and assisting NurExone in gaining in-depth information about their siRNA-loaded exosomes and subsequently, improving the different stages of their drug development process."

Story continues

Exosomes are best defined as EVs that have emerged as promising guided nanocarriers for drug delivery and targeted therapy, and as alternatives to stem cell therapy. EVs are endosome-derived small membrane vesicles, approximately 30 to 150 nanometres in diameter, and are released into extracellular fluids by cells in all living systems. They are well-suited for small functional molecule delivery, and increasing evidence indicates that they have a pivotal role in cell-to-cell communication.

NurExone's ExoTherapy uses proprietary exosomes as biologically-guided nanocarriers to deliver specialized therapeutic compounds to targeted areas. The delivered molecules promote an environment that induces a healing process at the target location. For its first clinical indication of providing recovery of function to traumatic spinal cord injury (SCI) patients, NurExone used modified siRNA sequences as the delivered therapeutic molecules.

ExoTherapy is being developed as a revolutionary "off-the-shelf" intranasal product to treat traumatic spinal cord and brain injuries as well as other Central Nervous System indications. In preclinical studies of rats with a fully transected spinal cords, intranasal administration of ExoPTEN led to significant motor improvement, sensory recovery, and faster urinary reflex restoration.

Investor Webinar

The Company will be hosting a webinar to discuss its recent business highlights and growth outlook on Thursday, October 20th, 2022 at 11:00 AM EST.

Please click the link below to register for the webinar.https://us02web.zoom.us/webinar/register/WN_hqlWt1EUTrCy_ol_iJ2DmA

About Nanometrix

Nanometrix is a nanoparticle analysis start-up based in Oxford, UK that has developed unique end-to-end services to routinely create molecular profiles of nanoparticles from samples. Each profile delivers information currently out of reach such as the morphology, population dynamics and cargo copy number per nanoparticle. Nanometrix's software and services are currently deployed across labs and teams globally working on the development of novel therapeutics and diagnostics.

For additional information, please visit http://www.nanometrix.bio or contact us at info@nanometrix.bio

About NurExone Biologic Inc.

NurExone Biologic Inc. is a TSXV listed pharmaceutical company that is developing a platform for biologically-guided ExoTherapy to be delivered, non-invasively, to patients who suffered traumatic spinal cord injuries. ExoTherapy was conceptually demonstrated in animal studies at the Technion, Israel Institute of Technology. NurExone is translating the treatment to humans, and the company holds an exclusive worldwide license from the Technion for the development and commercialization of the technology.

For additional information, please visit http://www.nurexone.com or follow NurExone on LinkedIn, Twitter, Facebook, or YouTube.

For more information, please contact:

Inbar Paz-BenayounHead of CommunicationsPhone: +972-52-3966695Email: info@nurexone.com

For investors:Investor RelationsIR@nurexone.com+1 905-347-5569

FORWARD-LOOKING STATEMENTS

This press release contains certain forward-looking statements, including statements about the Company's future plans, the Letter of Intent, the development activities to be carried out pursuant to the Collaboration, the potential entering into of a commercial agreement between the parties and future potential manufacturing and marketing activities. Wherever possible, words such as "may", "will", "should", "could", "expect", "plan", "intend", "anticipate", "believe", "estimate", "predict" or "potential" or the negative or other variations of these words, or similar words or phrases, have been used to identify these forward-looking statements. These statements reflect management's current beliefs and are based on information currently available to management as at the date hereof. Forward-looking statements involve significant risk, uncertainties and assumptions. Many factors could cause actual results, performance or achievements to differ materially from the results discussed or implied in the forward-looking statements. These risks and uncertainties include, but are not limited to, risks related to the Company's early stage of development, lack of revenues to date, government regulation, market acceptance for its products, rapid technological change, dependence on key personnel, protection of the Company's intellectual property and dependence on the Company's strategic partners. These factors should be considered carefully and readers should not place undue reliance on the forward-looking statements. Although the forward-looking statements contained in this press release are based upon what management believes to be reasonable assumptions, the Company cannot assure readers that actual results will be consistent with these forward-looking statements. These forward-looking statements are made as of the date of this press release, and the Company assumes no obligation to update or revise them to reflect new events or circumstances, except as required by law.

Neither TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this release.

NurExone is providing an updated release to the previously disseminated release from earlier today to remove a paragraph that was included in error.

To view the source version of this press release, please visit https://www.newsfilecorp.com/release/140289

Read the original post:
UPDATE: NurExone Signs Letter of Intent with Nanometrix for Its Exosome and Cargo Molecular Profiling AI-Driven Technology - Yahoo Finance

October 12, 2022 7:15 am ET

Companies on track to report data from the ongoing Phase 2 trial of mRNA-4157/V940 in combination with KEYTRUDA as adjuvant therapy in high-risk melanoma in 4Q 2022

CAMBRIDGE, M.A. and RAHWAY, N.J., October 12, 2022 Moderna, Inc. (Nasdaq: MRNA), a biotechnology company pioneering messenger RNA (mRNA) therapeutics and vaccines, and Merck (NYSE:MRK), known as MSD outside of the United States and Canada, today announced that Merck has exercised its option to jointly develop and commercialize personalized cancer vaccine (PCV) mRNA-4157/V940 pursuant to the terms of its existing Collaboration and License Agreement. mRNA-4157/V940 is currently being evaluated in combination with KEYTRUDA, Mercks anti-PD-1 therapy, as adjuvant treatment for patients with high-risk melanoma in a Phase 2 clinical trial being conducted by Moderna.

We have been collaborating with Merck on PCVs since 2016, and together we have made significant progress in advancing mRNA-4157 as an investigational personalized cancer treatment used in combination with KEYTRUDA, said Stephen Hoge, M.D., President of Moderna. With data expected this quarter on PCV, we continue to be excited about the future and the impact mRNA can have as a new treatment paradigm in the management of cancer. Continuing our strategic alliance with Merck is an important milestone as we continue to grow our mRNA platform with promising clinical programs in multiple therapeutic areas.

Under the agreement, originally established in 2016 and amended in 2018, Merck will pay Moderna $250 million to exercise its option for personalized cancer vaccines including mRNA-4157/V940 and will collaborate on development and commercialization. The payment will be expensed by Merck in the third quarter of 2022 and included in its non-GAAP results. Merck and Moderna will share costs and any profits equally under this worldwide collaboration.

This long-term collaboration combining Mercks expertise in immuno-oncology with Modernas pioneering mRNA technology has yielded a novel tailored vaccine approach, said Dr. Eliav Barr, senior vice president and head of global clinical development, chief medical officer, Merck Research Laboratories. We look forward to working with our colleagues at Moderna to advance mRNA-4157/V940 in combination with KEYTRUDA as it aligns with our strategy to impact early-stage disease.

About mRNA-4157/V940

Personalized cancer vaccines are designed to prime the immune system so that a patient can generate a tailored antitumor response to their tumor mutation signature to treat their cancer. mRNA-4157/V940 is designed to stimulate an immune response by generating T cell responses based on the mutational signature of a patients tumor.

About KEYNOTE-942 (NCT03897881)

KEYNOTE-942 is an ongoing randomized, open-label Phase 2 trial that enrolled 157 patients with high-risk melanoma. Following complete surgical resection, patients were randomized to mRNA-4157/V940 (9 doses every three weeks) and KEYTRUDA (200 mg every three weeks) versus KEYTRUDA alone for approximately one year until disease recurrence or unacceptable toxicity. KEYTRUDA was selected as the comparator in the trial because it is considered a standard of care for high-risk melanoma patients. The primary endpoint is recurrence-free survival, and secondary endpoints include distant metastasis-free survival and overall survival. The Phase 2 trial is fully enrolled and primary data are expected in the fourth quarter of 2022.

About KEYTRUDA (pembrolizumab) Injection 100 mg

KEYTRUDA is an anti-programmed death receptor-1 (PD-1) therapy that works by increasing the ability of the bodys immune system to help detect and fight tumor cells. KEYTRUDA is a humanized monoclonal antibody that blocks the interaction between PD-1 and its ligands, PD-L1 and PD-L2, thereby activating T lymphocytes which may affect both tumor cells and healthy cells.

Merck has the industrys largest immuno-oncology clinical research program. There are currently more than 1,600 trials studying KEYTRUDA across a wide variety of cancers and treatment settings. The KEYTRUDA clinical program seeks to understand the role of KEYTRUDA across cancers and the factors that may predict a patients likelihood of benefitting from treatment with KEYTRUDA, including exploring several different biomarkers.

Selected KEYTRUDA (pembrolizumab) Indications in the U.S.

Melanoma

KEYTRUDA is indicated for the treatment of patients with unresectable or metastatic melanoma.

KEYTRUDA is indicated for the adjuvant treatment of adult and pediatric (12 years and older) patients with stage IIB, IIC, or III melanoma following complete resection.

Non-Small Cell Lung Cancer

KEYTRUDA, in combination with pemetrexed and platinum chemotherapy, is indicated for the first-line treatment of patients with metastatic nonsquamous non-small cell lung cancer (NSCLC), with no EGFR or ALK genomic tumor aberrations.

KEYTRUDA, in combination with carboplatin and either paclitaxel or paclitaxel protein-bound, is indicated for the first-line treatment of patients with metastatic squamous NSCLC.

KEYTRUDA, as a single agent, is indicated for the first-line treatment of patients with NSCLC expressing PD-L1 [tumor proportion score (TPS) 1%] as determined by an FDA-approved test, with no EGFR or ALK genomic tumor aberrations, and is:

KEYTRUDA, as a single agent, is indicated for the treatment of patients with metastatic NSCLC whose tumors express PD-L1 (TPS 1%) as determined by an FDA-approved test, with disease progression on or after platinum-containing chemotherapy. Patients with EGFR or ALK genomic tumor aberrations should have disease progression on FDA-approved therapy for these aberrations prior to receiving KEYTRUDA.

Head and Neck Squamous Cell Cancer

KEYTRUDA, in combination with platinum and fluorouracil (FU), is indicated for the first-line treatment of patients with metastatic or with unresectable, recurrent head and neck squamous cell carcinoma (HNSCC).

KEYTRUDA, as a single agent, is indicated for the first-line treatment of patients with metastatic or with unresectable, recurrent HNSCC whose tumors express PD-L1 [Combined Positive Score (CPS) 1] as determined by an FDA-approved test.

KEYTRUDA, as a single agent, is indicated for the treatment of patients with recurrent or metastatic HNSCC with disease progression on or after platinum-containing chemotherapy.

Classical Hodgkin Lymphoma

KEYTRUDA is indicated for the treatment of adult patients with relapsed or refractory classical Hodgkin lymphoma (cHL).

KEYTRUDA is indicated for the treatment of pediatric patients with refractory cHL, or cHL that has relapsed after 2 or more lines of therapy.

Primary Mediastinal Large B-Cell Lymphoma

KEYTRUDA is indicated for the treatment of adult and pediatric patients with refractory primary mediastinal large B-cell lymphoma (PMBCL), or who have relapsed after 2 or more prior lines of therapy. KEYTRUDA is not recommended for treatment of patients with PMBCL who require urgent cytoreductive therapy.

Urothelial Carcinoma

KEYTRUDA is indicated for the treatment of patients with locally advanced or metastatic urothelial carcinoma (mUC):

Non-muscle Invasive Bladder Cancer

KEYTRUDA is indicated for the treatment of patients with Bacillus Calmette-Guerin-unresponsive, high-risk, non-muscle invasive bladder cancer (NMIBC) with carcinoma in situ with or without papillary tumors who are ineligible for or have elected not to undergo cystectomy.

Microsatellite Instability-High or Mismatch Repair Deficient Cancer

KEYTRUDA is indicated for the treatment of adult and pediatric patients with unresectable or metastatic microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) solid tumors, as determined by an FDA-approved test, that have progressed following prior treatment and who have no satisfactory alternative treatment options.

This indication is approved under accelerated approval based on tumor response rate and durability of response. Continued approval for this indication may be contingent upon verification and description of clinical benefit in the confirmatory trials. The safety and effectiveness of KEYTRUDA in pediatric patients with MSI-H central nervous system cancers have not been established.

Microsatellite Instability-High or Mismatch Repair Deficient Colorectal Cancer

KEYTRUDA is indicated for the treatment of patients with unresectable or metastatic MSI-H or dMMR colorectal cancer (CRC) as determined by an FDA-approved test.

Gastric Cancer

KEYTRUDA, in combination with trastuzumab, fluoropyrimidine- and platinum-containing chemotherapy, is indicated for the first-line treatment of patients with locally advanced unresectable or metastatic HER2-positive gastric or gastroesophageal junction (GEJ) adenocarcinoma.

This indication is approved under accelerated approval based on tumor response rate and durability of response. Continued approval of this indication may be contingent upon verification and description of clinical benefit in the confirmatory trials.

Esophageal Cancer

KEYTRUDA is indicated for the treatment of patients with locally advanced or metastatic esophageal or gastroesophageal junction (GEJ) (tumors with epicenter 1 to 5 centimeters above the GEJ) carcinoma that is not amenable to surgical resection or definitive chemoradiation either:

Cervical Cancer

KEYTRUDA, in combination with chemotherapy, with or without bevacizumab, is indicated for the treatment of patients with persistent, recurrent, or metastatic cervical cancer whose tumors express PD-L1 (CPS 1) as determined by an FDA-approved test.

KEYTRUDA, as a single agent, is indicated for the treatment of patients with recurrent or metastatic cervical cancer with disease progression on or after chemotherapy whose tumors express PD-L1 (CPS 1) as determined by an FDA-approved test.

Hepatocellular Carcinoma

KEYTRUDA is indicated for the treatment of patients with hepatocellular carcinoma (HCC) who have been previously treated with sorafenib. This indication is approved under accelerated approval based on tumor response rate and durability of response. Continued approval for this indication may be contingent upon verification and description of clinical benefit in the confirmatory trials.

Merkel Cell Carcinoma

KEYTRUDA is indicated for the treatment of adult and pediatric patients with recurrent locally advanced or metastatic Merkel cell carcinoma (MCC). This indication is approved under accelerated approval based on tumor response rate and durability of response. Continued approval for this indication may be contingent upon verification and description of clinical benefit in the confirmatory trials.

Renal Cell Carcinoma

KEYTRUDA, in combination with axitinib, is indicated for the first-line treatment of adult patients with advanced renal cell carcinoma (RCC).

KEYTRUDA, in combination with lenvatinib, is indicated for the first-line treatment of adult patients with advanced RCC.

KEYTRUDA is indicated for the adjuvant treatment of patients with RCC at intermediate-high or high risk of recurrence following nephrectomy, or following nephrectomy and resection of metastatic lesions.

Endometrial Carcinoma

KEYTRUDA, in combination with lenvatinib, is indicated for the treatment of patients with advanced endometrial carcinoma that is not MSI-H or dMMR, who have disease progression following prior systemic therapy in any setting and are not candidates for curative surgery or radiation.

KEYTRUDA, as a single agent, is indicated for the treatment of patients with advanced endometrial carcinoma that is MSI-H or dMMR, as determined by an FDA-approved test, who have disease progression following prior systemic therapy in any setting and are not candidates for curative surgery or radiation.

Tumor Mutational Burden-High Cancer

KEYTRUDA is indicated for the treatment of adult and pediatric patients with unresectable or metastatic tumor mutational burden-high (TMB-H) [10 mutations/megabase] solid tumors, as determined by an FDA-approved test, that have progressed following prior treatment and who have no satisfactory alternative treatment options. This indication is approved under accelerated approval based on tumor response rate and durability of response. Continued approval for this indication may be contingent upon verification and description of clinical benefit in the confirmatory trials. The safety and effectiveness of KEYTRUDA in pediatric patients with TMB-H central nervous system cancers have not been established.

Cutaneous Squamous Cell Carcinoma

KEYTRUDA is indicated for the treatment of patients with recurrent or metastatic cutaneous squamous cell carcinoma (cSCC) or locally advanced cSCC that is not curable by surgery or radiation.

Triple-Negative Breast Cancer

KEYTRUDA is indicated for the treatment of patients with high-risk early-stage triple-negative breast cancer (TNBC) in combination with chemotherapy as neoadjuvant treatment, and then continued as a single agent as adjuvant treatment after surgery.

KEYTRUDA, in combination with chemotherapy, is indicated for the treatment of patients with locally recurrent unresectable or metastatic TNBC whose tumors express PD-L1 (CPS 10) as determined by an FDA-approved test.

Selected Important Safety Information for KEYTRUDA

Severe and Fatal Immune-Mediated Adverse Reactions

KEYTRUDA is a monoclonal antibody that belongs to a class of drugs that bind to either the PD-1 or the PD-L1, blocking the PD-1/PD-L1 pathway, thereby removing inhibition of the immune response, potentially breaking peripheral tolerance and inducing immune-mediated adverse reactions. Immune-mediated adverse reactions, which may be severe or fatal, can occur in any organ system or tissue, can affect more than one body system simultaneously, and can occur at any time after starting treatment or after discontinuation of treatment. Important immune-mediated adverse reactions listed here may not include all possible severe and fatal immune-mediated adverse reactions.

Monitor patients closely for symptoms and signs that may be clinical manifestations of underlying immune-mediated adverse reactions. Early identification and management are essential to ensure safe use of antiPD-1/PD-L1 treatments. Evaluate liver enzymes, creatinine, and thyroid function at baseline and periodically during treatment. For patients with TNBC treated with KEYTRUDA in the neoadjuvant setting, monitor blood cortisol at baseline, prior to surgery, and as clinically indicated. In cases of suspected immune-mediated adverse reactions, initiate appropriate workup to exclude alternative etiologies, including infection. Institute medical management promptly, including specialty consultation as appropriate.

Withhold or permanently discontinue KEYTRUDA depending on severity of the immune-mediated adverse reaction. In general, if KEYTRUDA requires interruption or discontinuation, administer systemic corticosteroid therapy (1 to 2 mg/kg/day prednisone or equivalent) until improvement to Grade 1 or less. Upon improvement to Grade 1 or less, initiate corticosteroid taper and continue to taper over at least 1 month. Consider administration of other systemic immunosuppressants in patients whose adverse reactions are not controlled with corticosteroid therapy.

Immune-Mediated Pneumonitis

KEYTRUDA can cause immune-mediated pneumonitis. The incidence is higher in patients who have received prior thoracic radiation. Immune-mediated pneumonitis occurred in 3.4% (94/2799) of patients receiving KEYTRUDA, including fatal (0.1%), Grade 4 (0.3%), Grade 3 (0.9%), and Grade 2 (1.3%) reactions. Systemic corticosteroids were required in 67% (63/94) of patients. Pneumonitis led to permanent discontinuation of KEYTRUDA in 1.3% (36) and withholding in 0.9% (26) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement; of these, 23% had recurrence. Pneumonitis resolved in 59% of the 94 patients.

Pneumonitis occurred in 8% (31/389) of adult patients with cHL receiving KEYTRUDA as a single agent, including Grades 3-4 in 2.3% of patients. Patients received high-dose corticosteroids for a median duration of 10 days (range: 2 days to 53 months). Pneumonitis rates were similar in patients with and without prior thoracic radiation. Pneumonitis led to discontinuation of KEYTRUDA in 5.4% (21) of patients. Of the patients who developed pneumonitis, 42% interrupted KEYTRUDA, 68% discontinued KEYTRUDA, and 77% had resolution.

Immune-Mediated Colitis

KEYTRUDA can cause immune-mediated colitis, which may present with diarrhea. Cytomegalovirus infection/reactivation has been reported in patients with corticosteroid-refractory immune-mediated colitis. In cases of corticosteroid-refractory colitis, consider repeating infectious workup to exclude alternative etiologies. Immune-mediated colitis occurred in 1.7% (48/2799) of patients receiving KEYTRUDA, including Grade 4 (<0.1%), Grade 3 (1.1%), and Grade 2 (0.4%) reactions. Systemic corticosteroids were required in 69% (33/48); additional immunosuppressant therapy was required in 4.2% of patients. Colitis led to permanent discontinuation of KEYTRUDA in 0.5% (15) and withholding in 0.5% (13) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement; of these, 23% had recurrence. Colitis resolved in 85% of the 48 patients.

Hepatotoxicity and Immune-Mediated Hepatitis

KEYTRUDA as a Single Agent

KEYTRUDA can cause immune-mediated hepatitis. Immune-mediated hepatitis occurred in 0.7% (19/2799) of patients receiving KEYTRUDA, including Grade 4 (<0.1%), Grade 3 (0.4%), and Grade 2 (0.1%) reactions. Systemic corticosteroids were required in 68% (13/19) of patients; additional immunosuppressant therapy was required in 11% of patients. Hepatitis led to permanent discontinuation of KEYTRUDA in 0.2% (6) and withholding in 0.3% (9) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement; of these, none had recurrence. Hepatitis resolved in 79% of the 19 patients.

KEYTRUDA With Axitinib

KEYTRUDA in combination with axitinib can cause hepatic toxicity. Monitor liver enzymes before initiation of and periodically throughout treatment. Consider monitoring more frequently as compared to when the drugs are administered as single agents. For elevated liver enzymes, interrupt KEYTRUDA and axitinib, and consider administering corticosteroids as needed. With the combination of KEYTRUDA and axitinib, Grades 3 and 4 increased alanine aminotransferase (ALT) (20%) and increased aspartate aminotransferase (AST) (13%) were seen at a higher frequency compared to KEYTRUDA alone. Fifty-nine percent of the patients with increased ALT received systemic corticosteroids. In patients with ALT 3 times upper limit of normal (ULN) (Grades 2-4, n=116), ALT resolved to Grades 0-1 in 94%. Among the 92 patients who were rechallenged with either KEYTRUDA (n=3) or axitinib (n=34) administered as a single agent or with both (n=55), recurrence of ALT 3 times ULN was observed in 1 patient receiving KEYTRUDA, 16 patients receiving axitinib, and 24 patients receiving both. All patients with a recurrence of ALT 3 ULN subsequently recovered from the event.

Immune-Mediated Endocrinopathies

Adrenal Insufficiency

KEYTRUDA can cause primary or secondary adrenal insufficiency. For Grade 2 or higher, initiate symptomatic treatment, including hormone replacement as clinically indicated. Withhold KEYTRUDA depending on severity. Adrenal insufficiency occurred in 0.8% (22/2799) of patients receiving KEYTRUDA, including Grade 4 (<0.1%), Grade 3 (0.3%), and Grade 2 (0.3%) reactions. Systemic corticosteroids were required in 77% (17/22) of patients; of these, the majority remained on systemic corticosteroids. Adrenal insufficiency led to permanent discontinuation of KEYTRUDA in <0.1% (1) and withholding in 0.3% (8) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement.

Hypophysitis

KEYTRUDA can cause immune-mediated hypophysitis. Hypophysitis can present with acute symptoms associated with mass effect such as headache, photophobia, or visual field defects. Hypophysitis can cause hypopituitarism. Initiate hormone replacement as indicated. Withhold or permanently discontinue KEYTRUDA depending on severity. Hypophysitis occurred in 0.6% (17/2799) of patients receiving KEYTRUDA, including Grade 4 (<0.1%), Grade 3 (0.3%), and Grade 2 (0.2%) reactions. Systemic corticosteroids were required in 94% (16/17) of patients; of these, the majority remained on systemic corticosteroids. Hypophysitis led to permanent discontinuation of KEYTRUDA in 0.1% (4) and withholding in 0.3% (7) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement.

Thyroid Disorders

KEYTRUDA can cause immune-mediated thyroid disorders. Thyroiditis can present with or without endocrinopathy. Hypothyroidism can follow hyperthyroidism. Initiate hormone replacement for hypothyroidism or institute medical management of hyperthyroidism as clinically indicated. Withhold or permanently discontinue KEYTRUDA depending on severity. Thyroiditis occurred in 0.6% (16/2799) of patients receiving KEYTRUDA, including Grade 2 (0.3%). None discontinued, but KEYTRUDA was withheld in <0.1% (1) of patients.

Hyperthyroidism occurred in 3.4% (96/2799) of patients receiving KEYTRUDA, including Grade 3 (0.1%) and Grade 2 (0.8%). It led to permanent discontinuation of KEYTRUDA in <0.1% (2) and withholding in 0.3% (7) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement. Hypothyroidism occurred in 8% (237/2799) of patients receiving KEYTRUDA, including Grade 3 (0.1%) and Grade 2 (6.2%). It led to permanent discontinuation of KEYTRUDA in <0.1% (1) and withholding in 0.5% (14) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement. The majority of patients with hypothyroidism required long-term thyroid hormone replacement. The incidence of new or worsening hypothyroidism was higher in 1185 patients with HNSCC, occurring in 16% of patients receiving KEYTRUDA as a single agent or in combination with platinum and FU, including Grade 3 (0.3%) hypothyroidism. The incidence of new or worsening hypothyroidism was higher in 389 adult patients with cHL (17%) receiving KEYTRUDA as a single agent, including Grade 1 (6.2%) and Grade 2 (10.8%) hypothyroidism.

Type 1 Diabetes Mellitus (DM), Which Can Present With Diabetic Ketoacidosis

Monitor patients for hyperglycemia or other signs and symptoms of diabetes. Initiate treatment with insulin as clinically indicated. Withhold KEYTRUDA depending on severity. Type 1 DM occurred in 0.2% (6/2799) of patients receiving KEYTRUDA. It led to permanent discontinuation in <0.1% (1) and withholding of KEYTRUDA in <0.1% (1) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement.

Immune-Mediated Nephritis With Renal Dysfunction

KEYTRUDA can cause immune-mediated nephritis. Immune-mediated nephritis occurred in 0.3% (9/2799) of patients receiving KEYTRUDA, including Grade 4 (<0.1%), Grade 3 (0.1%), and Grade 2 (0.1%) reactions. Systemic corticosteroids were required in 89% (8/9) of patients. Nephritis led to permanent discontinuation of KEYTRUDA in 0.1% (3) and withholding in 0.1% (3) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement; of these, none had recurrence. Nephritis resolved in 56% of the 9 patients.

Immune-Mediated Dermatologic Adverse Reactions

KEYTRUDA can cause immune-mediated rash or dermatitis. Exfoliative dermatitis, including Stevens-Johnson syndrome, drug rash with eosinophilia and systemic symptoms, and toxic epidermal necrolysis, has occurred with antiPD-1/PD-L1 treatments. Topical emollients and/or topical corticosteroids may be adequate to treat mild to moderate nonexfoliative rashes. Withhold or permanently discontinue KEYTRUDA depending on severity. Immune-mediated dermatologic adverse reactions occurred in 1.4% (38/2799) of patients receiving KEYTRUDA, including Grade 3 (1%) and Grade 2 (0.1%) reactions. Systemic corticosteroids were required in 40% (15/38) of patients. These reactions led to permanent discontinuation in 0.1% (2) and withholding of KEYTRUDA in 0.6% (16) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement; of these, 6% had recurrence. The reactions resolved in 79% of the 38 patients.

Other Immune-Mediated Adverse Reactions

The following clinically significant immune-mediated adverse reactions occurred at an incidence of <1% (unless otherwise noted) in patients who received KEYTRUDA or were reported with the use of other antiPD-1/PD-L1 treatments. Severe or fatal cases have been reported for some of these adverse reactions. Cardiac/Vascular: Myocarditis, pericarditis, vasculitis;Nervous System: Meningitis, encephalitis, myelitis and demyelination, myasthenic syndrome/myasthenia gravis (including exacerbation), Guillain-Barr syndrome, nerve paresis, autoimmune neuropathy;Ocular: Uveitis, iritis and other ocular inflammatory toxicities can occur. Some cases can be associated with retinal detachment. Various grades of visual impairment, including blindness, can occur. If uveitis occurs in combination with other immune-mediated adverse reactions, consider a Vogt-Koyanagi-Harada-like syndrome, as this may require treatment with systemic steroids to reduce the risk of permanent vision loss;Gastrointestinal: Pancreatitis, to include increases in serum amylase and lipase levels, gastritis, duodenitis;Musculoskeletal and Connective Tissue: Myositis/polymyositis, rhabdomyolysis (and associated sequelae, including renal failure), arthritis (1.5%), polymyalgia rheumatica;Endocrine: Hypoparathyroidism;Hematologic/Immune: Hemolytic anemia, aplastic anemia, hemophagocytic lymphohistiocytosis, systemic inflammatory response syndrome, histiocytic necrotizing lymphadenitis (Kikuchi lymphadenitis), sarcoidosis, immune thrombocytopenic purpura, solid organ transplant rejection.

Infusion-Related Reactions

KEYTRUDA can cause severe or life-threatening infusion-related reactions, including hypersensitivity and anaphylaxis, which have been reported in 0.2% of 2799 patients receiving KEYTRUDA. Monitor for signs and symptoms of infusion-related reactions. Interrupt or slow the rate of infusion for Grade 1 or Grade 2 reactions. For Grade 3 or Grade 4 reactions, stop infusion and permanently discontinue KEYTRUDA.

Complications of Allogeneic Hematopoietic Stem Cell Transplantation (HSCT)

The rest is here:
Merck and Moderna Announce Exercise of Option by Merck for Joint Development and Commercialization of Investigational Personalized Cancer Vaccine -...

Chronic pain, a disease process that is so complex that we are only just beginning to understand its triggers, has recently been gaining recognition as a medical condition on its own. But how does living with chronic pain feel? And how do the body and brain deal with it?

Aching, dull, gnawing, burning, sharp, shooting, piercing

These are just some of the words people tend to use to describe their pain.

Now imagine you had to endure a bit of this every waking day until you dont know what its like to go about your day without this baseline of pain slowly depleting your mental and physical energy in the background.

That is the reality for many people who deal with chronic pain.

Some days may be great, some days bad; the signs may not always be visible and it may be an inward battle hidden behind gritted teeth and forced smiles.

But how does chronic pain become, well, chronic?

In the latest installment of our In Conversation podcast dedicated to Pain Awareness Month, Medical News Today dives into the science behind chronic pain with Dr. Hilary Guite and Dr. Tony L. Yaksh, professor of anesthesiology and pharmacology at the University of California, San Diego, as Joel Nelson, longtime psoriatic disease and arthritis patient and advocate, shares his personal journey with pain.

Chronic pain may often be dismissed as purely a symptom of a larger problem or not taken as seriously because it is not life threatening. However, the burden of chronic pain is not only personal but also societal.

Studies show that people with chronic pain may have difficulty in going about their daily lives and doing activities, as well as have poorer overall health. People with chronic pain may also have to deal with job insecurity or unemployment.

It wasnt until 2018 that the International Classification of Diseases (ICD) gave chronic pain its own code, in the preliminary version of the new ICD-11 coding system, paving way for its recognition and diagnosis.

According to the World Health Organization (WHO), chronic pain is now classified into two categories: chronic primary pain and chronic secondary pain.

Primary pain, according to this classification, refers to pain that is not caused by or cannot be explained by another medical condition. Some examples may be fibromyalgia or chronic primary low back pain.

Fibromyalgia [is] a condition that varies from person to person, but is a widespread pain condition affecting at least 4 to 5 regions of the body and lasts at least 3 months but usually longer. No other cause is found for the pain and it is, therefore, a type of primary chronic pain, Dr. Guite explained.

Secondary pain, on the other hand, is secondary to or caused by an underlying medical condition. Arthritis, cancer, or ulcerative colitis-related pain would fall within this umbrella.

[M]y chronic pain started around 10 years old. And [since] then, chronic pain has kind of been an intermittent part of my life right through to the present day, Joel Nelson told MNTs In Conversation.

Joel is now 38 years old, which means hes been living with chronic pain for a good few decades.

[M]y first experience with pain was [when] I got a pain in my hip; it was like a gravelly sort of burning feeling. And it just progressed; the more I used the joint, the [more it got] worse, it got to the point where I [was] sort of losing mobility, he said.

That was the point he decided to reach out for helpas most people do.

Joel said one word to describe his chronic pain is noise.

I always have described it as noise because on the days when that pain is intense, my ability to absorb other information, deal with multiple things at a time, its just gone, he said.

Living with my condition today, I think the most important takeaway about the experience is the fluidity of it. [U]ltimately, [my limits and mobility] can range from anything to where I can do more than walking, and I might be able to do a bit of running and cycling like I am currently, to next week I might be back on crutches. [A] lot of that is dictated by pain. So with arthritis, I get a lot of morning stiffness, but its the pain that limits my ability to do things. Joel Nelson

Likening it to a series of chapters, Joel said its not easy to anticipate what will happen next with his chronic pain.

Behind acute pain becoming chronic, scientists have found that a gateway receptor called Toll-like receptor 4 (TLR4) may be a controlling factor.

We know that under a tissue [or nerve] injury of various sorts that we can activate signaling that normally is associated with what we call innate immunity. And one of the mediators of that is something called the toll-like receptor and it turns out that while those are normally there to recognize the presence of foreign bugs, for example, E. coli, those bugs have in their cell membrane, something called lipopolysaccharide, or LPS. We dont have that normally in our system, but it comes from bacteria, said Dr. Yaksh.

Youre born with it, you dont have to develop it. Its there all the time. What weve come to find out over the last years [t]hat there are many products that your body releases that will [a]ctivate those very same toll-like receptors, he added.

Toll-like receptors may prime the central immune system for heightened states of pain. In response to harmful stimuli, stressors, or tissue injury, especially in the microbiome or the gastrointestinal tract, the body starts to release products from inflammatory cells.

When this happens, these products that are released from our own body can [a]ctivate these toll-like receptors, and theres [one] we call TLR4 [which] is present on inflammatory cells, and its also present on sensory neurons, he explained.

Dr. Yaksh said that activating TLR4 itself doesnt cause as much pain, but that it sets the nervous system up to become more reactive.

Coupled with this priming, if there are other stressors present at the timesuch as a bad diet or psychological distress, pointed out Dr. Guite this can set off a whole cascade that can fuel this transition to chronic pain.

[The activation of TLR4] sets up a whole series, a cascade in which there will be an increased expression of a large number of receptors and channels that are able to drive an enhanced response of the system. When this happens, you get this enhanced response downstream to the initial tissue injury. Its not so much that [it] causes the pain condition, it just sets the system up to be more reactive. Dr. Tony Yaksh

He said Joels situation fits within the notion that a person can transition from one type of pain to another.

[T]hat can be exacerbated by the stresses that are psychological which can exacerbate a pain state to one that may, in fact, have an underlying physiological component that we may not really understand, he added.

In Joels case, for example, Dr. Yaksh suggested it was likely that the stress (and joy) of becoming a father and all the other aspects played a role in what exacerbated Joels condition, and made it harder to keep the pain under control. He stressed that this did not make the pain any less real.

I think that probably there was this very strong, emotive component thats associated what Joels situation was, [] that the pain condition and the events that were associated with the psoriatic diagnosis and other aspects, perhaps, in fact, did establish the transition from one state to another [what] we call a transition or an acute to chronic, or the chronification of the pain state, he elaborated.

Theories so far suggest pain happens at the intersection of where the body meets the brain.

[Y]our comment about pain [being] in the brain is absolutely the correct way to think about it; the output function of anything comes from the higher centers, said Dr. Yaksh.

It all boils down to how the brain registers pain when there is tissue damage.

Pain is a crucial function for our survival; it is essentially a warning system that alerts our bodies that there is damage or illness to deal with. After an illness or injury, the nerves surrounding the area start sending signals up to the brain through the spinal cord, which encourages us to get help and stop further damage.

After the body sustains an injury, the damage to the bodys organs and tissues triggers an acute inflammatory response that involves immune cells, blood vessels, and other mediators. However, sometimes, even after this initial injury phase passes and the body heals, the nervous system may stay in this state of distress or reactivity.

When this happens, the body may become hypersensitive to pain. If this increased sensitivity is to heat or touch around the injured area, this is called peripheral sensitization.

[I]f I were to jam my finger, or if I were to develop, in Joels case, an event that leads to a local autoinflammation of the joint, then, in fact, that inflammation leads to the release of factors, which now sensitize the innervation of that joint, Dr. Yaksh elaborated.

Dr. Yaksh said this is something all people experience, regardless of whether it is chronic pain. He explained that after an injury, however, an innocuous activity such as wiggling ones finger can [become] extraordinarily noxious.

He described this as a sensitization generated by peripheral injury and inflammation, where this information is then relayed to the brain through the spinal cord.

The brain is now seeing what is otherwise an innocuous event, generating a signal that looks as if, as we would say, hell has frozen over, bad news is coming up the pipe. Dr. Tony Yaksh

However, sometimes this prolonged response to the initial injury may cause the lingering pain to be widespread, rather than localized to the injured area. This is called central sensitization.

[I]ts interesting in [Joels case], that you clearly have a peripheral issue, whether its the inflammation of a joint, inflammation of the skin, or changes in peripheral nerve function. And so not only do you get changes in joint morphology and things of that sort, but you actually get changes that lead to changes in the way that the information that goes into the spinal cord, and then to higher centers, Dr. Yaksh explained, and youve activated specific populations of sensory fibers that are normally activated only by severe injury.

[I]ts possible for that spinal cord, which is now, in a sense, organizing the input-output function from the periphery to the brain can become reorganized very much like if I were to take a radio and turn the volume upthe signal to the radio hasnt changed, but the volume gets louder. So, think of the spinal cord as a volume regulator. Dr. Tony Yaksh

And it says, bad news has happened. But we now know actually, that some of that input that comes up the same pathway [g]oes to areas of the brain that has nothing to do with where that pain [comes] fromonly that it is intense, he said.

These outputs that travel up the spinal cord inform the brain of where and how intense the pain is. One area these are processed in is the limbic system, or the old smell brain, said Dr. Yaksh.

These are areas of the brain that are, in fact, associated in humans with the input associated with emotionality, he added.

This stress can also modulate how pain is perceived by the body; it can cause muscles to tense or spasm, as well as lead to a rise in the levels of the hormone cortisol. This may cause inflammation and pain over time.

This can, in turn, can lead to sleeping problems, irritability, fatigue, and depression over time, creating a vicious cycle that adds to an already stressed nervous system, worsening the pain.

Although treatments for acute pain often involve taking various medications such as acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs), or opioids, treatment and management strategies for chronic pain are quite limited.

[W]e started out this conversation by saying pain is in the brain. And your perceptions of what the world is about impact you very directly, and in a way that is actually experimentally definable, changes the way your brain reacts. So when I say pain is in the brain, I am not saying its, its any less real in any way, shape, or form. Its a real thing, said Dr. Yaksh.

We now teach medical students that, you know, just because you dont see the primary diagnosis as being a swollen joint doesnt mean the patient doesnt have something, he pointed out.

Dr. Yaksh said mindfulness is often used in therapy to treat or manage fibromyalgia. He said that this doesnt mean there is no physiological component of fibromyalgia and indeed, recent research has shown that it is very likely to be an autoimmune condition just as real as the presence of antibodies that define the presence of an arthritic joint, he said.

Mindfulness, in a way, can help the individual respond to the nature of the afferent traffic thats coming up the spinal cord; its not something you could become mindful enough to say have surgery done. But it might [t]ake the edge off of some of the things that are, in fact, driving this exaggerated response. Fibromyalgia is a perfect example. Dr. Tony Yaksh

[Mindfulness] doesnt make the pain state any less real [but it] demonstrates that changing the way you think about your pain condition [can] help you deal with that pain condition, he said.

Joel added that, from the perspective of someone with chronic pain, it is a journey to see how the brain and the body work together to maintain pain:

.[I]t is a really delicate conversation when you talk about pain and it residing in the brain and, as somebody whos gone full circle through that journey of being horrified when that was first suggested to going through pain management, and then understanding it so that I could process it better. It changed everything for me.

What the future holds for treating chronic pain currently remains unclear. However, hope is that drugs might be developed to impact receptors such as TLR4 in a way that might not result in the pain going from acute to chronic, and that our understanding of how psychological processes interact with the neuro-immune interface increases over time.

Read more here:
In Conversation: How to understand chronic pain - Medical News Today