BACKGROUND. Low vitamin D status in pregnancy was proposed as a risk factor of preeclampsia.

METHODS. We assessed the effect of vitamin D supplementation (4,400 vs. 400 IU/day), initiated early in pregnancy (1018 weeks), on the development of preeclampsia. The effects of serum vitamin D (25-hydroxyvitamin D [25OHD]) levels on preeclampsia incidence at trial entry and in the third trimester (3238 weeks) were studied. We also conducted a nested case-control study of 157 women to investigate peripheral blood vitamin Dassociated gene expression profiles at 10 to 18 weeks in 47 participants who developed preeclampsia.

RESULTS. Of 881 women randomized, outcome data were available for 816, with 67 (8.2%) developing preeclampsia. There was no significant difference between treatment (N = 408) or control (N = 408) groups in the incidence of preeclampsia (8.08% vs. 8.33%, respectively; relative risk: 0.97; 95% CI, 0.611.53). However, in a cohort analysis and after adjustment for confounders, a significant effect of sufficient vitamin D status (25OHD 30 ng/ml) was observed in both early and late pregnancy compared with insufficient levels (25OHD <30 ng/ml) (adjusted odds ratio, 0.28; 95% CI, 0.100.96). Differential expression of 348 vitamin Dassociated genes (158 upregulated) was found in peripheral blood of women who developed preeclampsia (FDR <0.05 in the Vitamin D Antenatal Asthma Reduction Trial [VDAART]; P < 0.05 in a replication cohort). Functional enrichment and network analyses of this vitamin Dassociated gene set suggests several highly functional modules related to systematic inflammatory and immune responses, including some nodes with a high degree of connectivity.

CONCLUSIONS. Vitamin D supplementation initiated in weeks 1018 of pregnancy did not reduce preeclampsia incidence in the intention-to-treat paradigm. However, vitamin D levels of 30 ng/ml or higher at trial entry and in late pregnancy were associated with a lower risk of preeclampsia. Differentially expressed vitamin Dassociated transcriptomes implicated the emergence of an early pregnancy, distinctive immune response in women who went on to develop preeclampsia.

TRIAL REGISTRATION. ClinicalTrials.gov NCT00920621.

FUNDING. Quebec Breast Cancer Foundation and Genome Canada Innovation Network. This trial was funded by the National Heart, Lung, and Blood Institute. For details see Acknowledgments.

Hooman Mirzakhani, Augusto A. Litonjua, Thomas F. McElrath, George OConnor, Aviva Lee-Parritz, Ronald Iverson, George Macones, Robert C. Strunk, Leonard B. Bacharier, Robert Zeiger, Bruce W. Hollis, Diane E. Handy, Amitabh Sharma, Nancy Laranjo, Vincent Carey, Weilliang Qiu, Marc Santolini, Shikang Liu, Divya Chhabra, Daniel A. Enquobahrie, Michelle A. Williams, Joseph Loscalzo, Scott T. Weiss

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Bone Marrow Stem Cells Comments Off on JCI – Welcome | November 17th, 2016

Stem cells are undifferentiated biological cells that can differentiate into specialized cells and can divide (through mitosis) to produce more stem cells. They are found in multicellular organisms. In mammals, there are two broad types of stem cells: embryonic stem cells, which are isolated from the inner cell mass of blastocysts, and adult stem cells, which are found in various tissues. In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing adult tissues. In a developing embryo, stem cells can differentiate into all the specialized cellsectoderm, endoderm and mesoderm (see induced pluripotent stem cells)but also maintain the normal turnover of regenerative organs, such as blood, skin, or intestinal tissues.

There are three known accessible sources of autologous adult stem cells in humans:

Stem cells can also be taken from umbilical cord blood just after birth. Of all stem cell types, autologous harvesting involves the least risk. By definition, autologous cells are obtained from one's own body, just as one may bank his or her own blood for elective surgical procedures.

Adult stem cells are frequently used in various medical therapies (e.g., bone marrow transplantation). Stem cells can now be artificially grown and transformed (differentiated) into specialized cell types with characteristics consistent with cells of various tissues such as muscles or nerves. Embryonic cell lines and autologous embryonic stem cells generated through somatic cell nuclear transfer or dedifferentiation have also been proposed as promising candidates for future therapies.[1] Research into stem cells grew out of findings by Ernest A. McCulloch and James E. Till at the University of Toronto in the 1960s.[2][3]

The classical definition of a stem cell requires that it possess two properties:

Two mechanisms exist to ensure that a stem cell population is maintained:

Potency specifies the differentiation potential (the potential to differentiate into different cell types) of the stem cell.[4]

In practice, stem cells are identified by whether they can regenerate tissue. For example, the defining test for bone marrow or hematopoietic stem cells (HSCs) is the ability to transplant the cells and save an individual without HSCs. This demonstrates that the cells can produce new blood cells over a long term. It should also be possible to isolate stem cells from the transplanted individual, which can themselves be transplanted into another individual without HSCs, demonstrating that the stem cell was able to self-renew.

Properties of stem cells can be illustrated in vitro, using methods such as clonogenic assays, in which single cells are assessed for their ability to differentiate and self-renew.[7][8] Stem cells can also be isolated by their possession of a distinctive set of cell surface markers. However, in vitro culture conditions can alter the behavior of cells, making it unclear whether the cells shall behave in a similar manner in vivo. There is considerable debate as to whether some proposed adult cell populations are truly stem cells.[citation needed]

Embryonic stem (ES) cells are the cells of the inner cell mass of a blastocyst, an early-stage embryo.[9] Human embryos reach the blastocyst stage 45 days post fertilization, at which time they consist of 50150 cells. ES cells are pluripotent and give rise during development to all derivatives of the three primary germ layers: ectoderm, endoderm and mesoderm. In other words, they can develop into each of the more than 200 cell types of the adult body when given sufficient and necessary stimulation for a specific cell type. They do not contribute to the extra-embryonic membranes or the placenta.

During embryonic development these inner cell mass cells continuously divide and become more specialized. For example, a portion of the ectoderm in the dorsal part of the embryo specializes as 'neurectoderm', which will become the future central nervous system.[10] Later in development, neurulation causes the neurectoderm to form the neural tube. At the neural tube stage, the anterior portion undergoes encephalization to generate or 'pattern' the basic form of the brain. At this stage of development, the principal cell type of the CNS is considered a neural stem cell. These neural stem cells are pluripotent, as they can generate a large diversity of many different neuron types, each with unique gene expression, morphological, and functional characteristics. The process of generating neurons from stem cells is called neurogenesis. One prominent example of a neural stem cell is the radial glial cell, so named because it has a distinctive bipolar morphology with highly elongated processes spanning the thickness of the neural tube wall, and because historically it shared some glial characteristics, most notably the expression of glial fibrillary acidic protein (GFAP).[11][12] The radial glial cell is the primary neural stem cell of the developing vertebrate CNS, and its cell body resides in the ventricular zone, adjacent to the developing ventricular system. Neural stem cells are committed to the neuronal lineages (neurons, astrocytes, and oligodendrocytes), and thus their potency is restricted.[10]

Nearly all research to date has made use of mouse embryonic stem cells (mES) or human embryonic stem cells (hES) derived from the early inner cell mass. Both have the essential stem cell characteristics, yet they require very different environments in order to maintain an undifferentiated state. Mouse ES cells are grown on a layer of gelatin as an extracellular matrix (for support) and require the presence of leukemia inhibitory factor (LIF). Human ES cells are grown on a feeder layer of mouse embryonic fibroblasts (MEFs) and require the presence of basic fibroblast growth factor (bFGF or FGF-2).[13] Without optimal culture conditions or genetic manipulation,[14] embryonic stem cells will rapidly differentiate.

A human embryonic stem cell is also defined by the expression of several transcription factors and cell surface proteins. The transcription factors Oct-4, Nanog, and Sox2 form the core regulatory network that ensures the suppression of genes that lead to differentiation and the maintenance of pluripotency.[15] The cell surface antigens most commonly used to identify hES cells are the glycolipids stage specific embryonic antigen 3 and 4 and the keratan sulfate antigens Tra-1-60 and Tra-1-81. By using human embryonic stem cells to produce specialized cells like nerve cells or heart cells in the lab, scientists can gain access to adult human cells without taking tissue from patients. They can then study these specialized adult cells in detail to try and catch complications of diseases, or to study cells reactions to potentially new drugs. The molecular definition of a stem cell includes many more proteins and continues to be a topic of research.[16]

There are currently no approved treatments using embryonic stem cells. The first human trial was approved by the US Food and Drug Administration in January 2009.[17] However, the human trial was not initiated until October 13, 2010 in Atlanta for spinal cord injury research. On November 14, 2011 the company conducting the trial (Geron Corporation) announced that it will discontinue further development of its stem cell programs.[18] ES cells, being pluripotent cells, require specific signals for correct differentiationif injected directly into another body, ES cells will differentiate into many different types of cells, causing a teratoma. Differentiating ES cells into usable cells while avoiding transplant rejection are just a few of the hurdles that embryonic stem cell researchers still face.[19] Due to ethical considerations, many nations currently have moratoria or limitations on either human ES cell research or the production of new human ES cell lines. Because of their combined abilities of unlimited expansion and pluripotency, embryonic stem cells remain a theoretically potential source for regenerative medicine and tissue replacement after injury or disease.

Human embryonic stem cell colony on mouse embryonic fibroblast feeder layer

The primitive stem cells located in the organs of fetuses are referred to as fetal stem cells.[20] There are two types of fetal stem cells:

Adult stem cells, also called somatic (from Greek , "of the body") stem cells, are stem cells which maintain and repair the tissue in which they are found.[22] They can be found in children, as well as adults.[23]

Pluripotent adult stem cells are rare and generally small in number, but they can be found in umbilical cord blood and other tissues.[24] Bone marrow is a rich source of adult stem cells,[25] which have been used in treating several conditions including liver cirrhosis,[26] chronic limb ischemia [27] and endstage heart failure.[28] The quantity of bone marrow stem cells declines with age and is greater in males than females during reproductive years.[29] Much adult stem cell research to date has aimed to characterize their potency and self-renewal capabilities.[30] DNA damage accumulates with age in both stem cells and the cells that comprise the stem cell environment. This accumulation is considered to be responsible, at least in part, for increasing stem cell dysfunction with aging (see DNA damage theory of aging).[31]

Most adult stem cells are lineage-restricted (multipotent) and are generally referred to by their tissue origin (mesenchymal stem cell, adipose-derived stem cell, endothelial stem cell, dental pulp stem cell, etc.).[32][33]

Adult stem cell treatments have been successfully used for many years to treat leukemia and related bone/blood cancers through bone marrow transplants.[34] Adult stem cells are also used in veterinary medicine to treat tendon and ligament injuries in horses.[35]

The use of adult stem cells in research and therapy is not as controversial as the use of embryonic stem cells, because the production of adult stem cells does not require the destruction of an embryo. Additionally, in instances where adult stem cells are obtained from the intended recipient (an autograft), the risk of rejection is essentially non-existent. Consequently, more US government funding is being provided for adult stem cell research.[36]

Multipotent stem cells are also found in amniotic fluid. These stem cells are very active, expand extensively without feeders and are not tumorigenic. Amniotic stem cells are multipotent and can differentiate in cells of adipogenic, osteogenic, myogenic, endothelial, hepatic and also neuronal lines.[37] Amniotic stem cells are a topic of active research.

Use of stem cells from amniotic fluid overcomes the ethical objections to using human embryos as a source of cells. Roman Catholic teaching forbids the use of embryonic stem cells in experimentation; accordingly, the Vatican newspaper "Osservatore Romano" called amniotic stem cells "the future of medicine".[38]

It is possible to collect amniotic stem cells for donors or for autologuous use: the first US amniotic stem cells bank [39][40] was opened in 2009 in Medford, MA, by Biocell Center Corporation[41][42][43] and collaborates with various hospitals and universities all over the world.[44]

These are not adult stem cells, but rather adult cells (e.g. epithelial cells) reprogrammed to give rise to pluripotent capabilities. Using genetic reprogramming with protein transcription factors, pluripotent stem cells equivalent to embryonic stem cells have been derived from human adult skin tissue.[45][46][47]Shinya Yamanaka and his colleagues at Kyoto University used the transcription factors Oct3/4, Sox2, c-Myc, and Klf4[45] in their experiments on human facial skin cells. Junying Yu, James Thomson, and their colleagues at the University of WisconsinMadison used a different set of factors, Oct4, Sox2, Nanog and Lin28,[45] and carried out their experiments using cells from human foreskin.

As a result of the success of these experiments, Ian Wilmut, who helped create the first cloned animal Dolly the Sheep, has announced that he will abandon somatic cell nuclear transfer as an avenue of research.[48]

Frozen blood samples can be used as a source of induced pluripotent stem cells, opening a new avenue for obtaining the valued cells.[49]

To ensure self-renewal, stem cells undergo two types of cell division (see Stem cell division and differentiation diagram). Symmetric division gives rise to two identical daughter cells both endowed with stem cell properties. Asymmetric division, on the other hand, produces only one stem cell and a progenitor cell with limited self-renewal potential. Progenitors can go through several rounds of cell division before terminally differentiating into a mature cell. It is possible that the molecular distinction between symmetric and asymmetric divisions lies in differential segregation of cell membrane proteins (such as receptors) between the daughter cells.[50]

An alternative theory is that stem cells remain undifferentiated due to environmental cues in their particular niche. Stem cells differentiate when they leave that niche or no longer receive those signals. Studies in Drosophila germarium have identified the signals decapentaplegic and adherens junctions that prevent germarium stem cells from differentiating.[51][52]

Stem cell therapy is the use of stem cells to treat or prevent a disease or condition. Bone marrow transplant is a form of stem cell therapy that has been used for many years without controversy. No stem cell therapies other than bone marrow transplant are widely used.[53][54]

Stem cell treatments may require immunosuppression because of a requirement for radiation before the transplant to remove the person's previous cells, or because the patient's immune system may target the stem cells. One approach to avoid the second possibility is to use stem cells from the same patient who is being treated.

Pluripotency in certain stem cells could also make it difficult to obtain a specific cell type. It is also difficult to obtain the exact cell type needed, because not all cells in a population differentiate uniformly. Undifferentiated cells can create tissues other than desired types.[55]

Some stem cells form tumors after transplantation;[56] pluripotency is linked to tumor formation especially in embryonic stem cells, fetal proper stem cells, induced pluripotent stem cells. Fetal proper stem cells form tumors despite multipotency.[citation needed]

Some of the fundamental patents covering human embryonic stem cells are owned by the Wisconsin Alumni Research Foundation (WARF) they are patents 5,843,780, 6,200,806, and 7,029,913 invented by James A. Thomson. WARF does not enforce these patents against academic scientists, but does enforce them against companies.[57]

In 2006, a request for the US Patent and Trademark Office (USPTO) to re-examine the three patents was filed by the Public Patent Foundation on behalf of its client, the non-profit patent-watchdog group Consumer Watchdog (formerly the Foundation for Taxpayer and Consumer Rights).[57] In the re-examination process, which involves several rounds of discussion between the USTPO and the parties, the USPTO initially agreed with Consumer Watchdog and rejected all the claims in all three patents,[58] however in response, WARF amended the claims of all three patents to make them more narrow, and in 2008 the USPTO found the amended claims in all three patents to be patentable. The decision on one of the patents (7,029,913) was appealable, while the decisions on the other two were not.[59][60] Consumer Watchdog appealed the granting of the '913 patent to the USTPO's Board of Patent Appeals and Interferences (BPAI) which granted the appeal, and in 2010 the BPAI decided that the amended claims of the '913 patent were not patentable.[61] However, WARF was able to re-open prosecution of the case and did so, amending the claims of the '913 patent again to make them more narrow, and in January 2013 the amended claims were allowed.[62]

In July 2013, Consumer Watchdog announced that it would appeal the decision to allow the claims of the '913 patent to the US Court of Appeals for the Federal Circuit (CAFC), the federal appeals court that hears patent cases.[63] At a hearing in December 2013, the CAFC raised the question of whether Consumer Watchdog had legal standing to appeal; the case could not proceed until that issue was resolved.[64]

Diseases and conditions where stem cell treatment is being investigated include:

Research is underway to develop various sources for stem cells, and to apply stem cell treatments for neurodegenerative diseases and conditions, diabetes, heart disease, and other conditions.[80]

In more recent years, with the ability of scientists to isolate and culture embryonic stem cells, and with scientists' growing ability to create stem cells using somatic cell nuclear transfer and techniques to create induced pluripotent stem cells, controversy has crept in, both related to abortion politics and to human cloning.

Hepatotoxicity and drug-induced liver injury account for a substantial number of failures of new drugs in development and market withdrawal, highlighting the need for screening assays such as stem cell-derived hepatocyte-like cells, that are capable of detecting toxicity early in the drug development process.[81]

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Bone Marrow Stem Cells Comments Off on Stem cell – Wikipedia | November 16th, 2016

Everyone knows that the heart is a vital organ. We cannot live without our heart. However, when you get right down to it, the heart is just a pump. A complex and important one, yes, but still just a pump. As with all other pumps it can become clogged, break down and need repair. This is why it is critical that we know how the heart works. With a little knowledge about your heart and what is good or bad for it, you can significantly reduce your risk for heart disease.

Heart disease is the leading cause of death in the United States. Almost 2,000 Americans die of heart disease each day. That is one death every 44 seconds. The good news is that the death rate from heart disease has been steadily decreasing. Unfortunately, heart disease still causes sudden death and many people die before even reaching the hospital.

The heart holds a special place in our collective psyche as well. Of course the heart is synonymous with love. It has many other associations, too. Here are just a few examples:

Certainly no other bodily organ elicits this kind of response. When was the last time you had a heavy pancreas?

In this article, we will look at this important organ so that you can understand exactly what makes your heart tick.

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How Your Heart Works | HowStuffWorks

Bone Marrow Stem Cells Comments Off on How Your Heart Works | HowStuffWorks | November 16th, 2016

Bone marrow is the flexible tissue in the interior of bones. In humans, red blood cells are produced by cores of bone marrow in the heads of long bones in a process known as hematopoiesis.[2] On average, bone marrow constitutes 4% of the total body mass of humans; in an adult having 65 kilograms of mass (143 lbs), bone marrow typically accounts for approximately 2.6 kilograms (5.7lb). The hematopoietic component of bone marrow produces approximately 500 billion blood cells per day, which use the bone marrow vasculature as a conduit to the body's systemic circulation.[3] Bone marrow is also a key component of the lymphatic system, producing the lymphocytes that support the body's immune system.[4]

Bone marrow transplants can be conducted to treat severe diseases of the bone marrow, including certain forms of cancer such as leukemia. Additionally, bone marrow stem cells have been successfully transformed into functional neural cells,[5] and can also potentially be used to treat illnesses such as inflammatory bowel disease.[6]

The two types of bone marrow are "red marrow" (Latin: medulla ossium rubra), which consists mainly of hematopoietic tissue, and "yellow marrow" (Latin: medulla ossium flava), which is mainly made up of fat cells. Red blood cells, platelets, and most white blood cells arise in red marrow. Both types of bone marrow contain numerous blood vessels and capillaries. At birth, all bone marrow is red. With age, more and more of it is converted to the yellow type; only around half of adult bone marrow is red. Red marrow is found mainly in the flat bones, such as the pelvis, sternum, cranium, ribs, vertebrae and scapulae, and in the cancellous ("spongy") material at the epiphyseal ends of long bones such as the femur and humerus. Yellow marrow is found in the medullary cavity, the hollow interior of the middle portion of short bones. In cases of severe blood loss, the body can convert yellow marrow back to red marrow to increase blood cell production.

The stroma of the bone marrow is all tissue not directly involved in the marrow's primary function of hematopoiesis.[2] Yellow bone marrow makes up the majority of bone marrow stroma, in addition to smaller concentrations of stromal cells located in the red bone marrow. Though not as active as parenchymal red marrow, stroma is indirectly involved in hematopoiesis, since it provides the hematopoietic microenvironment that facilitates hematopoiesis by the parenchymal cells. For instance, they generate colony stimulating factors, which have a significant effect on hematopoiesis. Cell types that constitute the bone marrow stroma include:

In addition, the bone marrow contains hematopoietic stem cells, which give rise to the three classes of blood cells that are found in the circulation: white blood cells (leukocytes), red blood cells (erythrocytes), and platelets (thrombocytes).[7]

The bone marrow stroma contains mesenchymal stem cells (MSCs),[7] also known as marrow stromal cells. These are multipotent stem cells that can differentiate into a variety of cell types. MSCs have been shown to differentiate, in vitro or in vivo, into osteoblasts, chondrocytes, myocytes, adipocytes and beta-pancreatic islets cells.

The blood vessels of the bone marrow constitute a barrier, inhibiting immature blood cells from leaving the marrow. Only mature blood cells contain the membrane proteins, such as aquaporin and glycophorin, that are required to attach to and pass the blood vessel endothelium.[9]Hematopoietic stem cells may also cross the bone marrow barrier, and may thus be harvested from blood.

The red bone marrow is a key element of the lymphatic system, being one of the primary lymphoid organs that generate lymphocytes from immature hematopoietic progenitor cells.[4] The bone marrow and thymus constitute the primary lymphoid tissues involved in the production and early selection of lymphocytes. Furthermore, bone marrow performs a valve-like function to prevent the backflow of lymphatic fluid in the lymphatic system.

Biological compartmentalization is evident within the bone marrow, in that certain cell types tend to aggregate in specific areas. For instance, erythrocytes, macrophages, and their precursors tend to gather around blood vessels, while granulocytes gather at the borders of the bone marrow.[7]

Animal bone marrow has been used in cuisine worldwide for millennia, such as the famed Milanese Ossobuco.[citation needed]

The normal bone marrow architecture can be damaged or displaced by aplastic anemia, malignancies such as multiple myeloma, or infections such as tuberculosis, leading to a decrease in the production of blood cells and blood platelets. The bone marrow can also be affected by various forms of leukemia, which attacks its hematologic progenitor cells.[10] Furthermore, exposure to radiation or chemotherapy will kill many of the rapidly dividing cells of the bone marrow, and will therefore result in a depressed immune system. Many of the symptoms of radiation poisoning are due to damage sustained by the bone marrow cells.

To diagnose diseases involving the bone marrow, a bone marrow aspiration is sometimes performed. This typically involves using a hollow needle to acquire a sample of red bone marrow from the crest of the ilium under general or local anesthesia.[11]

On CT and plain film, marrow change can be seen indirectly by assessing change to the adjacent ossified bone. Assessment with MRI is usually more sensitive and specific for pathology, particularly for hematologic malignancies like leukemia and lymphoma. These are difficult to distinguish from the red marrow hyperplasia of hematopoiesis, as can occur with tobacco smoking, chronically anemic disease states like sickle cell anemia or beta thalassemia, medications such as granulocyte colony-stimulating factors, or during recovery from chronic nutritional anemias or therapeutic bone marrow suppression.[12] On MRI, the marrow signal is not supposed to be brighter than the adjacent intervertebral disc on T1 weighted images, either in the coronal or sagittal plane, where they can be assessed immediately adjacent to one another.[13] Fatty marrow change, the inverse of red marrow hyperplasia, can occur with normal aging,[14] though it can also be seen with certain treatments such as radiation therapy. Diffuse marrow T1 hypointensity without contrast enhancement or cortical discontinuity suggests red marrow conversion or myelofibrosis. Falsely normal marrow on T1 can be seen with diffuse multiple myeloma or leukemic infiltration when the water to fat ratio is not sufficiently altered, as may be seen with lower grade tumors or earlier in the disease process.[15]

Bone marrow examination is the pathologic analysis of samples of bone marrow obtained via biopsy and bone marrow aspiration. Bone marrow examination is used in the diagnosis of a number of conditions, including leukemia, multiple myeloma, anemia, and pancytopenia. The bone marrow produces the cellular elements of the blood, including platelets, red blood cells and white blood cells. While much information can be gleaned by testing the blood itself (drawn from a vein by phlebotomy), it is sometimes necessary to examine the source of the blood cells in the bone marrow to obtain more information on hematopoiesis; this is the role of bone marrow aspiration and biopsy.

The ratio between myeloid series and erythroid cells is relevant to bone marrow function, and also to diseases of the bone marrow and peripheral blood, such as leukemia and anemia. The normal myeloid-to-erythroid ratio is around 3:1; this ratio may increase in myelogenous leukemias, decrease in polycythemias, and reverse in cases of thalassemia.[16]

In a bone marrow transplant, hematopoietic stem cells are removed from a person and infused into another person (allogenic) or into the same person at a later time (autologous). If the donor and recipient are compatible, these infused cells will then travel to the bone marrow and initiate blood cell production. Transplantation from one person to another is conducted for the treatment of severe bone marrow diseases, such as congenital defects, autoimmune diseases or malignancies. The patient's own marrow is first killed off with drugs or radiation, and then the new stem cells are introduced. Before radiation therapy or chemotherapy in cases of cancer, some of the patient's hematopoietic stem cells are sometimes harvested and later infused back when the therapy is finished to restore the immune system.[17]

Bone marrow stem cells can be induced to become neural cells to treat neurological illnesses,[5] and can also potentially be used for the treatment of other illnesses, such as inflammatory bowel disease.[6] In 2013, following a clinical trial, scientists proposed that bone marrow transplantation could be used to treat HIV in conjunction with antiretroviral drugs;[18][19] however, it was later found that HIV remained in the bodies of the test subjects.[20]

The stem cells are typically harvested directly from the red marrow in the iliac crest, often under general anesthesia. The procedure is minimally invasive and does not require stitches afterwards. Depending on the donor's health and reaction to the procedure, the actual harvesting can be an outpatient procedure, or can require 12 days of recovery in the hospital.[21]

Another option is to administer certain drugs that stimulate the release of stem cells from the bone marrow into circulating blood.[22] An intravenous catheter is inserted into the donor's arm, and the stem cells are then filtered out of the blood. This procedure is similar to that used in blood or platelet donation. In adults, bone marrow may also be taken from the sternum, while the tibia is often used when taking samples from infants.[11] In newborns, stem cells may be retrieved from the umbilical cord.[23]

The earliest fossilised evidence of bone marrow was discovered in 2014 in Eusthenopteron, a lobe-finned fish which lived during the Devonian period approximately 370 million years ago.[24] Scientists from Uppsala University and the European Synchrotron Radiation Facility used X-ray synchrotron microtomography to study the fossilised interior of the skeleton's humerus, finding organised tubular structures akin to modern vertebrate bone marrow.[24]Eusthenopteron is closely related to the early tetrapods, which ultimately evolved into the land-dwelling mammals and lizards of the present day.[24]

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Bone Marrow Stem Cells Comments Off on Bone marrow – Wikipedia | October 25th, 2016

J R Soc Med. 2004 Oct; 97(10): 465471.

Institute of Medical Sciences, University of Lincoln, UK

An area of research that today generates great optimism is the use of stem cells for therapy of human diseases. Much of the excitement centres on embryonic stem cells, but this approach remains controversial for ethical reasons; moreover, routine clinical application of this strategy is many years away. By contrast, haematopoietic stem cells from adult bone marrow are well characterized and have long been used therapeutically.1 An adult weighing 70 kg has a functional haematopoietic marrow volume of about 1.75 L and upon increased demands such as infection or haemorrhage it can increase sixfold.1,2 No moral controversy surrounds the use of these cells since they are either autologous or collected from a consenting donor. The potential applications of adult bone marrow cells have gained momentum with discoveries relating to the mesenchymal stem cell.

Adult bone-marrow-derived mesenchymal stem cells (MSC) are capable of differentiation along several lineages ().315 They are positive for CD29, CD44, CD105 and CD166, have a doubling time of about two days, expand in culture up to sixfold and their biological functions are not altered by ageing.3,15 lists some of the cytokine receptors expressed by these cells and the cytokines produced. Their features and properties are closely similar to those of counterpart cells isolated from fetal blood, liver and bone in the first and second trimesters, from amniotic fluid and umbilical cord blood, and from adult peripheral blood, compact bone and adipose tissue.2127 Moreover, a CD133-positive subpopulation of these cells, which can be expanded under defined conditions for more than one hundred population doublings without telomere shortening or karyotypic abnormality, has proved capable of differentiation not only into mesenchymal cell types (osteoblasts, chondrocytes, adipocytes, myocytes) but also into endothelium and cells with neuroectodermal phenotype and function.2830 Previously, adult marrow-derived stem cells were believed to yield a limited number of cell types whereas embryonic cells were totipotent. The discovery of these multipotent adult stem cells has clearly narrowed the gap: they offer a very promising and much more abundant potential resource for therapy of inherited or degenerative diseases and for repair of tissues such as cartilage, bone and myocardium.

What is the mechanism of stem cell differentiation? When the phenomenon was first explored, the possibility of cell fusion was mootedthat is, hybridization with other cells rather than true plasticity. Indeed, embryonic stem cells were seen to hybridize with brain cells to form tetraploid cells with pluripotent character.31 However, in-vitro and in-vivo studies of adult bone marrow stem cells suggest a rate of cell fusion too low to account for the transdifferentiation.32 Moreover, single euploid bone marrow MSC, never co-cultured with tissue-specific cells or embryonic cells, have been seen to differentiate into cells of the three germ layers;33in vivo, the use of bone marrow cells selectively expressing the enhanced green fluorescent protein ruled out fusion as a mechanism for the generation of functional pancreatic islet beta cells;34 and hepatocytes, cardiomyocytes, and pancreatic and endothelial cells have been described as physiologically either diploid or polyploid.3537 Certain cytokines, including interleukins (IL) 1, 4, and 13, tumour necrosis factor alpha and interferon gamma, are involved in the generation of normal multinucleated cells such as osteoclasts and Langhans giant cells;3840 thus, observations suggesting fusion of bone marrow cells with, for example, Purkinje neurons, cardiomyocytes and hepatocytes41 may instead simply reflect physiological polyploidy.

The direction in which bone marrow MSC differentiate is heavily influenced by cytokines (). For example, bone morphogenetic protein 6 (BMP-6) not only influences differentiation towards chondrogenesis or osteogenesis but may also serve to regulate the bone marrow environment via the effects of IL-6 on haematopoiesis and osteogenesis.50 Two possible mechanisms have been proposed for a regulatory role of BMP-6 in the human bone marrow microenvironment: (i) it might enhance the osteoblastic differentiation of human MSC; or (ii) it might reduce the osteoclastic differentiation of haematopoietic marrow cells by decreasing interleukin-6 production in bone marrow stroma. MSC coexpressing CD133 and fetal liver kinase 1 generated endothelial cells in the presence of vascular endothelial growth factor, and functional hepatocytes in the presence of fibroblast growth factor-4 and hepatocyte growth factor.29,30 Also, MSC coexpressing CD133, CD172 and nestin differentiated along a neural pathway in the presence of fibroblast growth factor or retinoic acid plus nerve growth factor.51,54 An MSC side-population with high efflux of DNA binding dye and expressing CD90 (Thy1) differentiated into mesangial renal cells.55

In-vitro differentiation conditions of human adult bone marrow mesenchymal stem cell

In animal models, transplanted bone marrow cells have been detected in skeletal and cardiac muscle,5658 vascular endothelium,58,59 liver,6062 lung, gut and skin epithelia,62 pancreatic beta cell islets,34,63 renal glomeruli,14,55 and neural tissue.33,6469 When bone-marrow-derived MSC were injected intracerebrally in acid-sphingomyelinase-deficient mice, the onset of neurological abnormalities was delayed and the animals lifespan was extended.70 Local transplantation of such cells is also reported to have regenerated bone7173 and myocardium.74,75 It is noteworthy that no donor-derived tumours have been seen in these animal modelswhereas with transplantation of undifferentiated embryonic stem cells teratoma development has been reported.76 The results also differ from those of undifferentiated embryonic stem cell transplantation in that engraftment and tissue-specific differentiation are achieved without pretransplantation measures to induce differentiation down the lineage desired. The ability of marrow-derived cells to populate numerous body tissuesbone, liver, cardiac muscle, colon, skinis well shown in patients who have received cells from gender-mismatched donors ().7784 A postmortem study revealed donor-derived neurons in the hippocampus and cerebral cortex of brain samples from women who had received bone marrow transplants from men.85 Deductions from such findings must be qualified by the observation that women who have carried male fetuses may show long-term mosaicism with male cells; nevertheless, the weight of the evidence is that donor bone-marrow-derived cells can migrate and give rise to tissues belonging to all three germ-cell layers.7785 It is noteworthy that, in the transdifferentiation of these adult marrow stem cells, there was no evidence of cell fusion.7785 Lately, work in mice indicated that such cells participate in skin regeneration and reconstitution and promote wound healing;8688 and one research group reports a pilot study in three patients indicating that locally applied autologous bone marrow cells enhanced dermal building and closure of long-term non-healing wounds.89

Migration of human adult bone marrow stem cells in gender-mismatched bone marrow transplantation patients

In animal models of myocardial infarction, stem cells were reported to participate in repair whether injected locally or stimulated in bone marrow by use of stem cell factor (SCF) and G-CSF.90 In man, a randomized placebo-controlled study revealed increased coronary collateral flow in patients treated with intracoronary GM-CSF (molgramostim) followed by two weeks of subcutaneous administration.91

In the past decade the use of G-CSF (filgrastim) has transformed the treatment of cancer by facilitating marrow reconstitution after myeloablative therapy. We must hope for a similar breakthrough in the management of coronary heart disease.

In allogeneic transplantation, mesenchymal stem cells in bone marrow play a key part in immunomodulation and the induction of tolerance. MSC suppress the proliferation of T-lymphocytes induced by cellular or non-specific mitogenic stimuli92 and negatively influence B-cell lymphopoiesis.93 Allogeneic/xenogeneic MSC transplants engraft in immunocompetent sheep and non-human primates.9497 When a patient was treated, after myeloablation, with both haematopoietic stem cells and cultured MSC from a mismatched donor, only grade I graft-versus-host disease (GvHD) was observed.98 That MSC can not only reduce GvHD but also facilitate haematopoietic engraftment is evidenced by the rapid haematopoietic recovery of patients with breast cancer who received autologous blood stem cells together with culture-expanded MSC after high-dose chemotherapy.99 In both clinical trials, MSC transplantation was well tolerated.

Osteogenesis imperfecta has been the focus of two studies in children. Allogeneic MSC transplantation, leading to successful osteoblast engraftment in 3 of 5 children with type III osteogenesis imperfecta, was associated with a 4477% increase in bone mineral content, improved linear growth and reduced fracture frequency.77,100 In another cohort of 6 children with type III osteogenesis imperfecta who had received earlier bone marrow transplantation, MSC infusions from the original donor resulted in a 50% improvement in their growth velocity.101 Similar improvements were observed in children with metachromatic leukodystrophy and Hurlers syndrome after repeated allogeneic marrow MSC infusions.102

Ten clinical studies have been reported on the effects of autologous bone marrow stem cell transplantation in patients with myocardial infarction or ischaemic heart failure ().103112 In three pilot studies, two of them randomized controlled trials, bone marrow cells infused via a coronary catheter a few days after acute myocardial infarction led to significant improvement in coronary flow reserve and left ventricular ejection fraction.104,105,111 In the remaining seven, marrow cells injected directly into the myocardium of patients with chronic ischaemic heart disease yielded benefits in ejection fraction and also angina score.103,106110,112

Clinical trials of adult bone marrow autotransplantation in ischaemic heart disease

Despite the impressive safety record of all these pilot clinical trials, the possibility of undesired differentiation into other tissues must be borne in mind in monitoring of future studies.

In the next decade, the approaches discussed above will clearly be developed and refined. Further avenues will open up. For example, bone-marrow-derived cells expressing stem cell factor have been shown to initiate endogenous pancreatic tissue regeneration in mice.113 If such cells could be used as pancreatic beta islet cell progenitors, there would be scope for autologous transplantation in patients with diabetes, avoiding the need for the immunosuppression necessary after allotransplantation and circumventing the scarcity of allogeneic material. Whereas the multipotent adult dermal stem cells from human scalp skin have shown mainly neural differentiation, suggesting a possible therapeutic role in neurodegenerative diseases,114,115 the bone marrow MSC show strong orientation towards bone, cartilage, endothelium and cardiac muscle.

In conclusion, the existing medical uses of bone marrow are likely to expand greatly with exploitation of the therapeutic potential of adult mesenchymal stem cells, with their capacity for many lines of differentiation. The next stage is to isolate the various subsets and investigate their mechanisms of differentiation and homing to tissues. This work has vast implications for human wellbeing, through cell and gene therapies, through tissue engineering and through immunotherapy.

1. Hassan HT, Gutensohn K, Zander AR, Kuhnl P. CD34 positive cell sorting and enrichment: applications in bloodbanking and transplantation. In: Recktenwald D, Radbruch A, eds. Cell Separation: Methods and Applications. New York: Marcel Dekker, 1998: 28392

9. Sanchez-Ramos J, Song S, Cardozo-Pelaez F, et al. Adult bone marrow stromal cells differentiate into neural cells in vitro. Exp Neurol 2002;174: 1120

73. Kadiyala S, Jaiswal N, Bruder SP. Culture-expanded bone marrow-derived mesenchymal stem cells regenerate a critical-sized bone defect. Tissue Eng 9197;3: 17385

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Adult bone-marrow stem cells and their potential in medicine

Bone Marrow Stem Cells Comments Off on Adult bone-marrow stem cells and their potential in medicine | October 24th, 2016

Unlike cell lines, primary cells are non-transformed, non-immortalized cells that are isolated directly from tissue. Closely mimicking a living model and yielding more biologically and physiologically relevant results, human primary cells have become an essential tool in the development of therapeutic treatments. Choose from an extensive range of fresh and cryopreserved peripheral blood products, as well as cryopreserved cord blood products, to incorporate into your research workflow.

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Human peripheral blood cells are isolated from adult whole blood or from a leukapheresis preparation produced using state-of-the-art apheresis systems. These apheresis collections, known as "Leuko Paks", contain very high concentrations of mononuclear cells and are available in the following Pak sizes: full, half and quarter Pak. Specific cell subsets are purified using STEMCELL's cell isolation products. Fresh whole blood products are collected directly into blood bags using acid-citrate-dextrose solution A (ACDA) or citrate-phosphate-dextrose (CPD) as the anticoagulant.

Human cord blood is collected using citrate-phosphate-dextrose (CPD) as the anticoagulant. Mononuclear cells are obtained by density gradient centrifugation. Specific cell subsets are obtained using STEMCELLs cell isolation products.

Human adult bone marrow cells are drawn from the posterior iliac crest (25 mL/site) from a maximum of four sites per donor. Heparin is used as the anticoagulant. Mononuclear cells (MNCs) are obtained by density gradient centrifugation, and specific cell types are purified using STEMCELLs cell isolation products.

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Primary Cells Overview - stemcell.com

Bone Marrow Stem Cells Comments Off on Primary Cells Overview – stemcell.com | September 29th, 2016

by Jos Domen*, Amy Wagers** and Irving L. Weissman***

Blood and the system that forms it, known as the hematopoietic system, consist of many cell types with specialized functions (see Figure 2.1). Red blood cells (erythrocytes) carry oxygen to the tissues. Platelets (derived from megakaryocytes) help prevent bleeding. Granulocytes (neutrophils, basophils and eosinophils) and macrophages (collectively known as myeloid cells) fight infections from bacteria, fungi, and other parasites such as nematodes (ubiquitous small worms). Some of these cells are also involved in tissue and bone remodeling and removal of dead cells. B-lymphocytes produce antibodies, while T-lymphocytes can directly kill or isolate by inflammation cells recognized as foreign to the body, including many virus-infected cells and cancer cells. Many blood cells are short-lived and need to be replenished continuously; the average human requires approximately one hundred billion new hematopoietic cells each day. The continued production of these cells depends directly on the presence of Hematopoietic Stem Cells (HSCs), the ultimate, and only, source of all these cells.

Figure 2.1. Hematopoietic and stromal cell differentiation.

2001 Terese Winslow (assisted by Lydia Kibiuk)

The search for stem cells began in the aftermath of the bombings in Hiroshima and Nagasaki in 1945. Those who died over a prolonged period from lower doses of radiation had compromised hematopoietic systems that could not regenerate either sufficient white blood cells to protect against otherwise nonpathogenic infections or enough platelets to clot their blood. Higher doses of radiation also killed the stem cells of the intestinal tract, resulting in more rapid death. Later, it was demonstrated that mice that were given doses of whole body X-irradiation developed the same radiation syndromes; at the minimal lethal dose, the mice died from hematopoietic failure approximately two weeks after radiation exposure.1 Significantly, however, shielding a single bone or the spleen from radiation prevented this irradiation syndrome. Soon thereafter, using inbred strains of mice, scientists showed that whole-body-irradiated mice could be rescued from otherwise fatal hematopoietic failure by injection of suspensions of cells from blood-forming organs such as the bone marrow.2 In 1956, three laboratories demonstrated that the injected bone marrow cells directly regenerated the blood-forming system, rather than releasing factors that caused the recipients' cells to repair irradiation damage.35 To date, the only known treatment for hematopoietic failure following whole body irradiation is transplantation of bone marrow cells or HSCs to regenerate the blood-forming system in the host organisms.6,7

The hematopoietic system is not only destroyed by the lowest doses of lethal X-irradiation (it is the most sensitive of the affected vital organs), but also by chemotherapeutic agents that kill dividing cells. By the 1960s, physicians who sought to treat cancer that had spread (metastasized) beyond the primary cancer site attempted to take advantage of the fact that a large fraction of cancer cells are undergoing cell division at any given point in time. They began using agents (e.g., chemical and X-irradiation) that kill dividing cells to attempt to kill the cancer cells. This required the development of a quantitative assessment of damage to the cancer cells compared that inflicted on normal cells. Till and McCulloch began to assess quantitatively the radiation sensitivity of one normal cell type, the bone marrow cells used in transplantation, as it exists in the body. They found that, at sub-radioprotective doses of bone marrow cells, mice that died 1015 days after irradiation developed colonies of myeloid and erythroid cells (see Figure 2.1 for an example) in their spleens. These colonies correlated directly in number with the number of bone marrow cells originally injected (approximately 1 colony per 7,000 bone marrow cells injected).8 To test whether these colonies of blood cells derived from single precursor cells, they pre-irradiated the bone marrow donors with low doses of irradiation that would induce unique chromosome breaks in most hematopoietic cells but allow some cells to survive. Surviving cells displayed radiation-induced and repaired chromosomal breaks that marked each clonogenic (colony-initiating) hematopoietic cell.9 The researchers discovered that all dividing cells within a single spleen colony, which contained different types of blood cells, contained the same unique chromosomal marker. Each colony displayed its own unique chromosomal marker, seen in its dividing cells.9 Furthermore, when cells from a single spleen colony were re-injected into a second set of lethally-irradiated mice, donor-derived spleen colonies that contained the same unique chromosomal marker were often observed, indicating that these colonies had been regenerated from the same, single cell that had generated the first colony. Rarely, these colonies contained sufficient numbers of regenerative cells both to radioprotect secondary recipients (e.g., to prevent their deaths from radiation-induced blood cell loss) and to give rise to lymphocytes and myeloerythroid cells that bore markers of the donor-injected cells.10,11 These genetic marking experiments established the fact that cells that can both self-renew and generate most (if not all) of the cell populations in the blood must exist in bone marrow. At the time, such cells were called pluripotent HSCs, a term later modified to multipotent HSCs.12,13 However, identifying stem cells in retrospect by analysis of randomly chromosome-marked cells is not the same as being able to isolate pure populations of HSCs for study or clinical use.

Achieving this goal requires markers that uniquely define HSCs. Interestingly, the development of these markers, discussed below, has revealed that most of the early spleen colonies visible 8 to 10 days after injection, as well as many of the later colonies, visible at least 12 days after injection, are actually derived from progenitors rather than from HSCs. Spleen colonies formed by HSCs are relatively rare and tend to be present among the later colonies.14,15 However, these findings do not detract from Till and McCulloch's seminal experiments to identify HSCs and define these unique cells by their capacities for self-renewal and multilineage differentiation.

While much of the original work was, and continues to be, performed in murine model systems, strides have been made to develop assays to study human HSCs. The development of Fluorescence Activated Cell Sorting (FACS) has been crucial for this field (see Figure 2.2). This technique enables the recognition and quantification of small numbers of cells in large mixed populations. More importantly, FACS-based cell sorting allows these rare cells (1 in 2000 to less than 1 in 10,000) to be purified, resulting in preparations of near 100% purity. This capability enables the testing of these cells in various assays.

Figure 2.2. Enrichment and purification methods for hematopoietic stem cells. Upper panels illustrate column-based magnetic enrichment. In this method, the cells of interest are labeled with very small iron particles (A). These particles are bound to antibodies that only recognize specific cells. The cell suspension is then passed over a column through a strong magnetic field which retains the cells with the iron particles (B). Other cells flow through and are collected as the depleted negative fraction. The magnet is removed, and the retained cells are collected in a separate tube as the positive or enriched fraction (C). Magnetic enrichment devices exist both as small research instruments and large closed-system clinical instruments.

Lower panels illustrate Fluorescence Activated Cell Sorting (FACS). In this setting, the cell mixture is labeled with fluorescent markers that emit light of different colors after being activated by light from a laser. Each of these fluorescent markers is attached to a different monoclonal antibody that recognizes specific sets of cells (D). The cells are then passed one by one in a very tight stream through a laser beam (blue in the figure) in front of detectors (E) that determine which colors fluoresce in response to the laser. The results can be displayed in a FACS-plot (F). FACS-plots (see figures 3 and 4 for examples) typically show fluorescence levels per cell as dots or probability fields. In the example, four groups can be distinguished: Unstained, red-only, green-only, and red-green double labeling. Each of these groups, e.g., green fluorescence-only, can be sorted to very high purity. The actual sorting happens by breaking the stream shown in (E) into tiny droplets, each containing 1 cell, that then can be sorted using electric charges to move the drops. Modern FACS machines use three different lasers (that can activate different set of fluorochromes), to distinguish up to 8 to 12 different fluorescence colors and sort 4 separate populations, all simultaneously.

Magnetic enrichment can process very large samples (billions of cells) in one run, but the resulting cell preparation is enriched for only one parameter (e.g., CD34) and is not pure. Significant levels of contaminants (such as T-cells or tumor cells) remain present. FACS results in very pure cell populations that can be selected for several parameters simultaneously (e.g., Linneg, CD34pos, CD90pos), but it is more time consuming (10,000 to 50,000 cells can be sorted per second) and requires expensive instrumentation.

2001 Terese Winslow (assisted by Lydia Kibiuk)

Assays have been developed to characterize hematopoietic stem and progenitor cells in vitro and in vivo (Figure 2.3).16,17In vivo assays that are used to study HSCs include Till and McCulloch's classical spleen colony forming (CFU-S) assay,8 which measures the ability of HSC (as well as blood-forming progenitor cells) to form large colonies in the spleens of lethally irradiated mice. Its main advantage (and limitation) is the short-term nature of the assay (now typically 12 days). However, the assays that truly define HSCs are reconstitution assays.16,18 Mice that have been quot;preconditionedquot; by lethal irradiation to accept new HSCs are injected with purified HSCs or mixed populations containing HSCs, which will repopulate the hematopoietic systems of the host mice for the life of the animal. These assays typically use different types of markers to distinguish host and donor-derived cells.

For example, allelic assays distinguish different versions of a particular gene, either by direct analysis of dna or of the proteins expressed by these alleles. These proteins may be cell-surface proteins that are recognized by specific monoclonal antibodies that can distinguish between the variants (e.g., CD45 in Figure 2.3) or cellular proteins that may be recognized through methods such as gel-based analysis. Other assays take advantage of the fact that male cells can be detected in a female host by detecting the male-cell-specific Y-chromosome by molecular assays (e.g., polymerase chain reaction, or PCR).

Figure 2.3. Assays used to detect hematopoietic stem cells. The tissue culture assays, which are used frequently to test human cells, include the ability of the cells to be tested to grow as quot;cobblestonesquot; (the dark cells in the picture) for 5 to 7 weeks in culture. The Long Term Culture-Initiating Cell assay measures whether hematopoietic progenitor cells (capable of forming colonies in secondary assays, as shown in the picture) are still present after 5 to 7 weeks of culture.

In vivo assays in mice include the CFU-S assay, the original stem cell assay discussed in the introduction. The most stringent hematopoietic stem cell assay involves looking for the long-term presence of donor-derived cells in a reconstituted host. The example shows host-donor recognition by antibodies that recognize two different mouse alleles of CD45, a marker present on nearly all blood cells. CD45 is also a good marker for distinguishing human blood cells from mouse blood cells when testing human cells in immunocompromised mice such as NOD/SCID. Other methods such as pcr-markers, chromosomal markers, and enzyme markers can also be used to distinguish host and donor cells.

Small numbers of HSCs (as few as one cell in mouse experiments) can be assayed using competitive reconstitutions, in which a small amount of host-type bone marrow cells (enough to radioprotect the host and thus ensure survival) is mixed in with the donor-HSC population. To establish long-term reconstitutions in mouse models, the mice are followed for at least 4 months after receiving the HSCs. Serial reconstitution, in which the bone marrow from a previously-irradiated and reconstituted mouse becomes the HSC source for a second irradiated mouse, extends the potential of this assay to test lifespan and expansion limits of HSCs. Unfortunately, the serial transfer assay measures both the lifespan and the transplantability of the stem cells. The transplantability may be altered under various conditions, so this assay is not the sine qua non of HSC function. Testing the in vivo activity of human cells is obviously more problematic.

Several experimental models have been developed that allow the testing of human cells in mice. These assays employ immunologically-incompetent mice (mutant mice that cannot mount an immune response against foreign cells) such as SCID1921 or NOD-SCID mice.22,23 Reconstitution can be performed in either the presence or absence of human fetal bone or thymus implants to provide a more natural environment in which the human cells can grow in the mice. Recently NOD/SCID/c-/- mice have been used as improved recipients for human HSCs, capable of complete reconstitution with human lymphocytes, even in the absence of additional human tissues.24 Even more promising has been the use of newborn mice with an impaired immune system (Rag-2-/-C-/-), which results in reproducible production of human B- and T-lymphoid and myeloerythroid cells.25 These assays are clearly more stringent, and thus more informative, but also more difficult than the in vitro HSC assays discussed below. However, they can only assay a fraction of the lifespan under which the cells would usually have to function. Information on the long-term functioning of cells can only be derived from clinical HSC transplantations.

A number of assays have been developed to recognize HSCs in vitro (e.g., in tissue culture). These are especially important when assaying human cells. Since transplantation assays for human cells are limited, cell culture assays often represent the only viable option. In vitro assays for HSCs include Long-Term Culture-Initializing Cell (LTC-IC) assays2628 and Cobble-stone Area Forming Cell (CAFC) assays.29 LTC-IC assays are based on the ability of HSCs, but not more mature progenitor cells, to maintain progenitor cells with clonogenic potential over at least a five-week culture period. CAFC assays measure the ability of HSCs to maintain a specific and easily recognizable way of growing under stromal cells for five to seven weeks after the initial plating. Progenitor cells can only grow in culture in this manner for shorter periods of time.

While initial experiments studied HSC activity in mixed populations, much progress has been made in specifically describing the cells that have HSC activity. A variety of markers have been discovered to help recognize and isolate HSCs. Initial marker efforts focused on cell size, density, and recognition by lectins (carbohydrate-binding proteins derived largely from plants),30 but more recent efforts have focused mainly on cell surface protein markers, as defined by monoclonal antibodies. For mouse HSCs, these markers include panels of 8 to 14 different monoclonal antibodies that recognize cell surface proteins present on differentiated hematopoietic lineages, such as the red blood cell and macrophage lineages (thus, these markers are collectively referred to as quot;Linquot;),13,31 as well as the proteins Sca-1,13,31 CD27,32 CD34,33 CD38,34 CD43,35 CD90.1(Thy-1.1),13,31 CD117(c-Kit),36 AA4.1,37 and MHC class I,30 and CD150.38 Human HSCs have been defined with respect to staining for Lin,39 CD34,40 CD38,41 CD43,35 CD45RO,42 CD45RA,42 CD59,43 CD90,39 CD109,44 CD117,45 CD133,46,47CD166,48 and HLA DR(human).49,50 In addition, metabolic markers/dyes such as rhodamine123 (which stains mitochondria),51 Hoechst33342 (which identifies MDR-type drug efflux activity),52 Pyronin-Y (which stains RNA),53 and BAAA (indicative of aldehyde dehydrogenase enzyme activity)54 have been described. While none of these markers recognizes functional stem cell activity, combinations (typically with 3 to 5 different markers, see examples below) allow for the purification of near-homogenous populations of HSCs. The ability to obtain pure preparations of HSCs, albeit in limited numbers, has greatly facilitated the functional and biochemical characterization of these important cells. However, to date there has been limited impact of these discoveries on clinical practice, as highly purified HSCs have only rarely been used to treat patients (discussed below). The undeniable advantages of using purified cells (e.g., the absence of contaminating tumor cells in autologous transplantations) have been offset by practical difficulties and increased purification costs.

Figure 2.4. Examples of Hematopoietic Stem Cell staining patterns in mouse bone marrow (top) and human mobilized peripheral blood (bottom). The plots on the right show only the cells present in the left blue box. The cells in the right blue box represent HSCs. Stem cells form a rare fraction of the cells present in both cases.

HSC assays, when combined with the ability to purify HSCs, have provided increasingly detailed insight into the cells and the early steps involved in the differentiation process. Several marker combinations have been developed that describe murine HSCs, including [CD117high, CD90.1low, Linneg/low, Sca-1pos],15 [CD90.1low, Linneg, Sca-1pos Rhodamine123low],55 [CD34neg/low, CD117pos, Sca-1pos, Linneg],33 [CD150 pos, CD48neg, CD244neg],38 and quot;side-populationquot; cells using Hoechst-dye.52 Each of these combinations allows purification of HSCs to near-homogeneity. Figure 2.4 shows an example of an antibody combination that can recognize mouse HSCs. Similar strategies have been developed to purify human HSCs, employing markers such as CD34, CD38, Lin, CD90, CD133 and fluorescent substrates for the enzyme, aldehyde dehydrogenase. The use of highly purified human HSCs has been mainly experimental, and clinical use typically employs enrichment for one marker, usually CD34. CD34 enrichment yields a population of cells enriched for HSC and blood progenitor cells but still contains many other cell types. However, limited trials in which highly FACS-purified CD34pos CD90pos HSCs (see Figure 2.4) were used as a source of reconstituting cells have demonstrated that rapid reconstitution of the blood system can reliably be obtained using only HSCs.5658

The purification strategies described above recognize a rare subset of cells. Exact numbers depend on the assay used as well as on the genetic background studied.16 In mouse bone marrow, 1 in 10,000 cells is a hematopoietic stem cell with the ability to support long-term hematopoiesis following transplantation into a suitable host. When short-term stem cells, which have a limited self-renewal capacity, are included in the estimation, the frequency of stem cells in bone marrow increases to 1 in 1,000 to 1 in 2,000 cells in humans and mice. The numbers present in normal blood are at least ten-fold lower than in marrow.

None of the HSC markers currently used is directly linked to an essential HSC function, and consequently, even within a species, markers can differ depending on genetic alleles,59 mouse strains,60 developmental stages,61 and cell activation stages.62,63 Despite this, there is a clear correlation in HSC markers between divergent species such as humans and mice. However, unless the ongoing attempts at defining the complete HSC gene expression patterns will yield usable markers that are linked to essential functions for maintaining the quot;stemnessquot; of the cells,64,65 functional assays will remain necessary to identify HSCs unequivocally.16

More recently, efforts at defining hematopoietic populations by cell surface or other FACS-based markers have been extended to several of the progenitor populations that are derived from HSCs (see Figure 2.5). Progenitors differ from stem cells in that they have a reduced differentiation capacity (they can generate only a subset of the possible lineages) but even more importantly, progenitors lack the ability to self-renew. Thus, they have to be constantly regenerated from the HSC population. However, progenitors do have extensive proliferative potential and can typically generate large numbers of mature cells. Among the progenitors defined in mice and humans are the Common Lymphoid Progenitor (CLP),66,67 which in adults has the potential to generate all of the lymphoid but not myeloerythroid cells, and a Common Myeloid Progenitor (CMP), which has the potential to generate all of the mature myeloerythroid, but not lymphoid, cells.68,69 While beyond the scope of this overview, hematopoietic progenitors have clinical potential and will likely see clinical use.70,71

Figure 2.5. Relationship between several of the characterized hematopoietic stem cells and early progenitor cells. Differentiation is indicated by colors; the more intense the color, the more mature the cells. Surface marker distinctions are subtle between these early cell populations, yet they have clearly distinct potentials. Stem cells can choose between self-renewal and differentiation. Progenitors can expand temporarily but always continue to differentiate (other than in certain leukemias). The mature lymphoid (T-cells, B-cells, and Natural Killer cells) and myeloerythroid cells (granulocytes, macrophages, red blood cells, and platelets) that are produced by these stem and progenitor cells are shown in more detail in Figure 2.1.

HSCs have a number of unique properties, the combination of which defines them as such.16 Among the core properties are the ability to choose between self-renewal (remain a stem cell after cell division) or differentiation (start the path towards becoming a mature hematopoietic cell). In addition, HSCs migrate in regulated fashion and are subject to regulation by apoptosis (programmed cell death). The balance between these activities determines the number of stem cells that are present in the body.

One essential feature of HSCs is the ability to self-renew, that is, to make copies with the same or very similar potential. This is an essential property because more differentiated cells, such as hematopoietic progenitors, cannot do this, even though most progenitors can expand significantly during a limited period of time after being generated. However, for continued production of the many (and often short-lived) mature blood cells, the continued presence of stem cells is essential. While it has not been established that adult HSCs can self-renew indefinitely (this would be difficult to prove experimentally), it is clear from serial transplantation experiments that they can produce enough cells to last several (at least four to five) lifetimes in mice. It is still unclear which key signals allow self-renewal. One link that has been noted is telomerase, the enzyme necessary for maintaining telomeres, the DNA regions at the end of chromosomes that protect them from accumulating damage due to DNA replication. Expression of telomerase is associated with self-renewal activity.72 However, while absence of telomerase reduces the self-renewal capacity of mouse HSCs, forced expression is not sufficient to enable HSCs to be transplanted indefinitely; other barriers must exist.73,74

It has proven surprisingly difficult to grow HSCs in culture despite their ability to self-renew. Expansion in culture is routine with many other cells, including neural stem cells and ES cells. The lack of this capacity for HSCs severely limits their application, because the number of HSCs that can be isolated from mobilized blood, umbilical cord blood, or bone marrow restricts the full application of HSC transplantation in man (whether in the treatment of nuclear radiation exposure or transplantation in the treatment of blood cell cancers or genetic diseases of the blood or blood-forming system). Engraftment periods of 50 days or more were standard when limited numbers of bone marrow or umbilical cord blood cells were used in a transplant setting, reflecting the low level of HSCs found in these native tissues. Attempts to expand HSCs in tissue culture with known stem-cell stimulators, such as the cytokines stem cell factor/steel factor (KitL), thrombopoietin (TPO), interleukins 1, 3, 6, 11, plus or minus the myeloerythroid cytokines GM-CSF, G-CSF, M-CSF, and erythropoietin have never resulted in a significant expansion of HSCs.16,75 Rather, these compounds induce many HSCs into cell divisions that are always accompanied by cellular differentiation.76 Yet many experiments demonstrate that the transplantation of a single or a few HSCs into an animal results in a 100,000-fold or greater expansion in the number of HSCs at the steady state while simultaneously generating daughter cells that permitted the regeneration of the full blood-forming system.7780 Thus, we do not know the factors necessary to regenerate HSCs by self-renewing cell divisions. By investigating genes transcribed in purified mouse LT-HSCs, investigators have found that these cells contain expressed elements of the Wnt/fzd/beta-catenin signaling pathway, which enables mouse HSCs to undergo self-renewing cell divisions.81,82 Overexpression of several other proteins, including HoxB48386 and HoxA987 has also been reported to achieve this. Other signaling pathways that are under investigation include Notch and Sonic hedgehog.75 Among the intracellular proteins thought to be essential for maintaining the quot;stem cellquot; state are Polycomb group genes, including Bmi-1.88 Other genes, such as c-Myc and JunB have also been shown to play a role in this process.89,90Much remains to be discovered, including the identity of the stimuli that govern self-renewal in vivo, as well as the composition of the environment (the stem cell quot;nichequot;) that provides these stimuli.91 The recent identification of osteoblasts, a cell type known to be involved in bone formation, as a critical component of this environment92,93 will help to focus this search. For instance, signaling by Angiopoietin-1 on osteoblasts to Tie-2 receptors on HSCs has recently been suggested to regulate stem cell quiescence (the lack of cell division).94 It is critical to discover which pathways operate in the expansion of human HSCs to take advantage of these pathways to improve hematopoietic transplantation.

Differentiation into progenitors and mature cells that fulfill the functions performed by the hematopoietic system is not a unique HSC property, but, together with the option to self-renew, defines the core function of HSCs. Differentiation is driven and guided by an intricate network of growth factors and cytokines. As discussed earlier, differentiation, rather than self-renewal, seems to be the default outcome for HSCs when stimulated by many of the factors to which they have been shown to respond. It appears that, once they commit to differentiation, HSCs cannot revert to a self-renewing state. Thus, specific signals, provided by specific factors, seem to be needed to maintain HSCs. This strict regulation may reflect the proliferative potential present in HSCs, deregulation of which could easily result in malignant diseases such as leukemia or lymphoma.

Migration of HSCs occurs at specific times during development (i.e., seeding of fetal liver, spleen and eventually, bone marrow) and under certain conditions (e.g., cytokine-induced mobilization) later in life. The latter has proven clinically useful as a strategy to enhance normal HSC proliferation and migration, and the optimal mobilization regimen for HSCs currently used in the clinic is to treat the stem cell donor with a drug such as cytoxan, which kills most of his or her dividing cells. Normally, only about 8% of LT-HSCs enter the cell cycle per day,95,96 so HSCs are not significantly affected by a short treatment with cytoxan. However, most of the downstream blood progenitors are actively dividing,66,68 and their numbers are therefore greatly depleted by this dose, creating a demand for a regenerated blood-forming system. Empirically, cytokines or growth factors such as G-CSF and KitL can increase the number of HSCs in the blood, especially if administered for several days following a cytoxan pulse. The optimized protocol of cytoxan plus G-CSF results in several self-renewing cell divisions for each resident LT-HSC in mouse bone marrow, expanding the number of HSCs 12- to 15-fold within two to three days.97 Then, up to one-half of the daughter cells of self-renewing dividing LT-HSCs (estimated to be up to 105 per mouse per day98) leave the bone marrow, enter the blood, and within minutes engraft other hematopoietic sites, including bone marrow, spleen, and liver.98 These migrating cells can and do enter empty hematopoietic niches elsewhere in the bone marrow and provide sustained hematopoietic stem cell self-renewal and hematopoiesis.98,99 It is assumed that this property of mobilization of HSCs is highly conserved in evolution (it has been shown in mouse, dog and humans) and presumably results from contact with natural cell-killing agents in the environment, after which regeneration of hematopoiesis requires restoring empty HSC niches. This means that functional, transplantable HSCs course through every tissue of the body in large numbers every day in normal individuals.

Apoptosis, or programmed cell death, is a mechanism that results in cells actively self-destructing without causing inflammation. Apoptosis is an essential feature in multicellular organisms, necessary during development and normal maintenance of tissues. Apoptosis can be triggered by specific signals, by cells failing to receive the required signals to avoid apoptosis, and by exposure to infectious agents such as viruses. HSCs are not exempt; apoptosis is one mechanism to regulate their numbers. This was demonstrated in transgenic mouse experiments in which HSC numbers doubled when the apoptosis threshold was increased.76 This study also showed that HSCs are particularly sensitive and require two signals to avoid undergoing apoptosis.

The best-known location for HSCs is bone marrow, and bone marrow transplantation has become synonymous with hematopoietic cell transplantation, even though bone marrow itself is increasingly infrequently used as a source due to an invasive harvesting procedure that requires general anesthesia. In adults, under steady-state conditions, the majority of HSCs reside in bone marrow. However, cytokine mobilization can result in the release of large numbers of HSCs into the blood. As a clinical source of HSCs, mobilized peripheral blood (MPB) is now replacing bone marrow, as harvesting peripheral blood is easier for the donors than harvesting bone marrow. As with bone marrow, mobilized peripheral blood contains a mixture of hematopoietic stem and progenitor cells. MPB is normally passed through a device that enriches cells that express CD34, a marker on both stem and progenitor cells. Consequently, the resulting cell preparation that is infused back into patients is not a pure HSC preparation, but a mixture of HSCs, hematopoietic progenitors (the major component), and various contaminants, including T cells and, in the case of autologous grafts from cancer patients, quite possibly tumor cells. It is important to distinguish these kinds of grafts, which are the grafts routinely given, from highly purified HSC preparations, which essentially lack other cell types.

In the late 1980s, umbilical cord blood (UCB) was recognized as an important clinical source of HSCs.100,101 Blood from the placenta and umbilical cord is a rich source of hematopoietic stem cells, and these cells are typically discarded with the afterbirth. Increasingly, UCB is harvested, frozen, and stored in cord blood banks, as an individual resource (donor-specific source) or as a general resource, directly available when needed. Cord blood has been used successfully to transplant children and (far less frequently) adults. Specific limitations of UCB include the limited number of cells that can be harvested and the delayed immune reconstitution observed following UCB transplant, which leaves patients vulnerable to infections for a longer period of time. Advantages of cord blood include its availability, ease of harvest, and the reduced risk of graft-versus-host-disease (GVHD). In addition, cord blood HSCs have been noted to have a greater proliferative capacity than adult HSCs. Several approaches have been tested to overcome the cell dose issue, including, with some success, pooling of cord blood samples.101,102 Ex vivo expansion in tissue culture, to which cord blood cells are more amenable than adult cells, is another approach under active investigation.103

The use of cord blood has opened a controversial treatment strategyembryo selection to create a related UCB donor.104 In this procedure, embryos are conceived by in vitro fertilization. The embryos are tested by pre-implantation genetic diagnosis, and embryos with transplantation antigens matching those of the affected sibling are implanted. Cord blood from the resulting newborn is then used to treat this sibling. This approach, successfully pioneered at the University of Minnesota, can in principle be applied to a wide variety of hematopoietic disorders. However, the ethical questions involved argue for clear regulatory guidelines.105

Embryonic stem (ES) cells form a potential future source of HSCs. Both mouse and human ES cells have yielded hematopoietic cells in tissue culture, and they do so relatively readily.106 However, recognizing the actual HSCs in these cultures has proven problematic, which may reflect the variability in HSC markers or the altered reconstitution behavior of these HSCs, which are expected to mimic fetal HSC. This, combined with the potential risks of including undifferentiated cells in an ES-cell-derived graft means that, based on the current science, clinical use of ES cell-derived HSCs remains only a theoretical possibility for now.

An ongoing set of investigations has led to claims that HSCs, as well as other stem cells, have the capacity to differentiate into a much wider range of tissues than previously thought possible. It has been claimed that, following reconstitution, bone marrow cells can differentiate not only into blood cells but also muscle cells (both skeletal myocytes and cardiomyocytes),107111 brain cells,112,113 liver cells,114,115 skin cells, lung cells, kidney cells, intestinal cells,116 and pancreatic cells.117 Bone marrow is a complex mixture that contains numerous cell types. In addition to HSCs, at least one other type of stem cell, the mesenchymal stem cell (MSC), is present in bone marrow. MSCs, which have become the subject of increasingly intense investigation, seem to retain a wide range of differentiation capabilities in vitro that is not restricted to mesodermal tissues, but includes tissues normally derived from other embryonic germ layers (e.g., neurons).118120MSCs are discussed in detail in Dr. Catherine Verfaillie's testimony to the President's Council on Bioethics at this website: refer to Appendix J (page 295) and will not be discussed further here. However, similar claims of differentiation into multiple diverse cell types, including muscle,111 liver,114 and different types of epithelium116 have been made in experiments that assayed partially- or fully-purified HSCs. These experiments have spawned the idea that HSCs may not be entirely or irreversibly committed to forming the blood, but under the proper circumstances, HSCs may also function in the regeneration or repair of non-blood tissues. This concept has in turn given rise to the hypothesis that the fate of stem cells is quot;plastic,quot; or changeable, allowing these cells to adopt alternate fates if needed in response to tissue-derived regenerative signals (a phenomenon sometimes referred to as quot;transdifferentiationquot;). This in turn seems to bolster the argument that the full clinical potential of stem cells can be realized by studying only adult stem cells, foregoing research into defining the conditions necessary for the clinical use of the extensive differentiation potential of embryonic stem cells. However, as discussed below, such quot;transdifferentiationquot; claims for specialized adult stem cells are controversial, and alternative explanations for these observations remain possible, and, in several cases, have been documented directly.

While a full discussion of this issue is beyond the scope of this overview, several investigators have formulated criteria that must be fulfilled to demonstrate stem cell plasticity.121,122 These include (i) clonal analysis, which requires the transfer and analysis of single, highly-purified cells or individually marked cells and the subsequent demonstration of both quot;normalquot; and quot;plasticquot; differentiation outcomes, (ii) robust levels of quot;plasticquot; differentiation outcome, as extremely rare events are difficult to analyze and may be induced by artefact, and (iii) demonstration of tissue-specific function of the quot;transdifferentiatedquot; cell type. Few of the current reports fulfill these criteria, and careful analysis of individually transplanted KTLS HSCs has failed to show significant levels of non-hematopoietic engraftment.123,124In addition, several reported trans-differentiation events that employed highly purified HSCs, and in some cases a very strong selection pressure for trans-differentiation, now have been shown to result from fusion of a blood cell with a non-blood cell, rather than from a change in fate of blood stem cells.125127 Finally, in the vast majority of cases, reported contributions of adult stem cells to cell types outside their tissue of origin are exceedingly rare, far too rare to be considered therapeutically useful. These findings have raised significant doubts about the biological importance and immediate clinical utility of adult hematopoietic stem cell plasticity. Instead, these results suggest that normal tissue regeneration relies predominantly on the function of cell type-specific stem or progenitor cells, and that the identification, isolation, and characterization of these cells may be more useful in designing novel approaches to regenerative medicine. Nonetheless, it is possible that a rigorous and concerted effort to identify, purify, and potentially expand the appropriate cell populations responsible for apparent quot;plasticityquot; events, characterize the tissue-specific and injury-related signals that recruit, stimulate, or regulate plasticity, and determine the mechanism(s) underlying cell fusion or transdifferentiation, may eventually enhance tissue regeneration via this mechanism to clinically useful levels.

Recent progress in genomic sequencing and genome-wide expression analysis at the RNA and protein levels has greatly increased our ability to study cells such as HSCs as quot;systems,quot; that is, as combinations of defined components with defined interactions. This goal has yet to be realized fully, as computational biology and system-wide protein biochemistry and proteomics still must catch up with the wealth of data currently generated at the genomic and transcriptional levels. Recent landmark events have included the sequencing of the human and mouse genomes and the development of techniques such as array-based analysis. Several research groups have combined cDNA cloning and sequencing with array-based analysis to begin to define the full transcriptional profile of HSCs from different species and developmental stages and compare these to other stem cells.64,65,128131 Many of the data are available in online databases, such as the NIH/NIDDK Stem Cell Genome Anatomy Projects. While transcriptional profiling is clearly a work in progress, comparisons among various types of stem cells may eventually identify sets of genes that are involved in defining the general quot;stemnessquot; of a cell, as well as sets of genes that define their exit from the stem cell pool (e.g., the beginning of their path toward becoming mature differentiated cells, also referred to as commitment). In addition, these datasets will reveal sets of genes that are associated with specific stem cell populations, such as HSCs and MSCs, and thus define their unique properties. Assembly of these datasets into pathways will greatly help to understand and to predict the responses of HSCs (and other stem cells) to various stimuli.

The clinical use of stem cells holds great promise, although the application of most classes of adult stem cells is either currently untested or is in the earliest phases of clinical testing.132,133 The only exception is HSCs, which have been used clinically since 1959 and are used increasingly routinely for transplantations, albeit almost exclusively in a non-pure form. By 1995, more than 40,000 transplants were performed annually world-wide.134,135 Currently the main indications for bone marrow transplantation are either hematopoietic cancers (leukemias and lymphomas), or the use of high-dose chemotherapy for non-hematopoietic malignancies (cancers in other organs). Other indications include diseases that involve genetic or acquired bone marrow failure, such as aplastic anemia, thalassemia sickle cell anemia, and increasingly, autoimmune diseases.

Transplantation of bone marrow and HSCs are carried out in two rather different settings, autologous and allogeneic. Autologous transplantations employ a patient's own bone marrow tissue and thus present no tissue incompatibility between the donor and the host. Allogeneic transplantations occur between two individuals who are not genetically identical (with the rare exceptions of transplantations between identical twins, often referred to as syngeneic transplantations). Non-identical individuals differ in their human leukocyte antigens (HLAs), proteins that are expressed by their white blood cells. The immune system uses these HLAs to distinguish between quot;selfquot; and quot;nonself.quot; For successful transplantation, allogeneic grafts must match most, if not all, of the six to ten major HLA antigens between host and donor. Even if they do, however, enough differences remain in mostly uncharacterized minor antigens to enable immune cells from the donor and the host to recognize the other as quot;nonself.quot; This is an important issue, as virtually all HSC transplants are carried out with either non-purified, mixed cell populations (mobilized peripheral blood, cord blood, or bone marrow) or cell populations that have been enriched for HSCs (e.g., by column selection for CD34+ cells) but have not been fully purified. These mixed population grafts contain sufficient lymphoid cells to mount an immune response against host cells if they are recognized as quot;non-self.quot; The clinical syndrome that results from this quot;non-selfquot; response is known as graft-versus-host disease (GVHD).136

In contrast, autologous grafts use cells harvested from the patient and offer the advantage of not causing GVHD. The main disadvantage of an autologous graft in the treatment of cancer is the absence of a graft-versusleukemia (GVL) or graft-versus-tumor (GVT) response, the specific immunological recognition of host tumor cells by donor-immune effector cells present in the transplant. Moreover, the possibility exists for contamination with cancerous or pre-cancerous cells.

Allogeneic grafts also have disadvantages. They are limited by the availability of immunologically-matched donors and the possibility of developing potentially lethal GVHD. The main advantage of allogeneic grafts is the potential for a GVL response, which can be an important contribution to achieving and maintaining complete remission.137,138

Today, most grafts used in the treatment of patients consist of either whole or CD34+-enriched bone marrow or, more likely, mobilized peripheral blood. The use of highly purified hematopoietic stem cells as grafts is rare.5658 However, the latter have the advantage of containing no detectable contaminating tumor cells in the case of autologous grafts, therefore not inducing GVHD, or presumably GVL,139141in allogeneic grafts. While they do so less efficiently than lymphocyte-containing cell mixtures, HSCs alone can engraft across full allogeneic barriers (i.e., when transplanted from a donor who is a complete mismatch for both major and minor transplantation antigens).139141The use of donor lymphocyte infusions (DLI) in the context of HSC transplantation allows for the controlled addition of lymphocytes, if necessary, to obtain or maintain high levels of donor cells and/or to induce a potentially curative GVL-response.142,143 The main problems associated with clinical use of highly purified HSCs are the additional labor and costs144 involved in obtaining highly purified cells in sufficient quantities.

While the possibilities of GVL and other immune responses to malignancies remain the focus of intense interest, it is also clear that in many cases, less-directed approaches such as chemotherapy or irradiation offer promise. However, while high-dose chemotherapy combined with autologous bone marrow transplantation has been reported to improve outcome (usually measured as the increase in time to progression, or increase in survival time),145154 this has not been observed by other researchers and remains controversial.155161 The tumor cells present in autologous grafts may be an important limitation in achieving long-term disease-free survival. Only further purification/ purging of the grafts, with rigorous separation of HSCs from cancer cells, can overcome this limitation. Initial small scale trials with HSCs purified by flow cytometry suggest that this is both possible and beneficial to the clinical outcome.56 In summary, purification of HSCs from cancer/lymphoma/leukemia patients offers the only possibility of using these cells post-chemotherapy to regenerate the host with cancer-free grafts. Purification of HSCs in allotransplantation allows transplantation with cells that regenerate the blood-forming system but cannot induce GVHD.

An important recent advance in the clinical use of HSCs is the development of non-myeloablative preconditioning regimens, sometimes referred to as quot;mini transplants.quot;162164 Traditionally, bone marrow or stem cell transplantation has been preceded by a preconditioning regimen consisting of chemotherapeutic agents, often combined with irradiation, that completely destroys host blood and bone marrow tissues (a process called myeloablation). This creates quot;spacequot; for the incoming cells by freeing stem cell niches and prevents an undesired immune response of the host cells against the graft cells, which could result in graft failure. However, myeloablation immunocompromises the patient severely and necessitates a prolonged hospital stay under sterile conditions. Many protocols have been developed that use a more limited and targeted approach to preconditioning. These nonmyeloablative preconditioning protocols, which combine excellent engraftment results with the ability to perform hematopoietic cell transplantation on an outpatient basis, have greatly changed the clinical practice of bone marrow transplantation.

FACS purification of HSCs in mouse and man completely eliminates contaminating T cells, and thus GVHD (which is caused by T-lymphocytes) in allogeneic transplants. Many HSC transplants have been carried out in different combinations of mouse strains. Some of these were matched at the major transplantation antigens but otherwise different (Matched Unrelated Donors or MUD); in others, no match at the major or minor transplantation antigens was expected. To achieve rapid and sustained engraftment, higher doses of HSCs were required in these mismatched allogeneic transplants than in syngeneic transplants.139141,165167 In these experiments, hosts whose immune and blood-forming systems were generated from genetically distinct donors were permanently capable of accepting organ transplants (such as the heart) from either donor or host, but not from mice unrelated to the donor or host. This phenomenon is known as transplant-induced tolerance and was observed whether the organ transplants were given the same day as the HSCs or up to one year later.139,166Hematopoietic cell transplant-related complications have limited the clinical application of such tolerance induction for solid organ grafts, but the use of non-myeloablative regimens to prepare the host, as discussed above, should significantly reduce the risk associated with combined HSC and organ transplants. Translation of these findings to human patients should enable a switch from chronic immunosuppression to prevent rejection to protocols wherein a single conditioning dose allows permanent engraftment of both the transplanted blood system and solid organ(s) or other tissue stem cells from the same donor. This should eliminate both GVHD and chronic host transplant immunosuppression, which lead to many complications, including life-threatening opportunistic infections and the development of malignant neoplasms.

We now know that several autoimmune diseasesdiseases in which immune cells attack normal body tissuesinvolve the inheritance of high risk-factor genes.168 Many of these genes are expressed only in blood cells. Researchers have recently tested whether HSCs could be used in mice with autoimmune disease (e.g., type 1 diabetes) to replace an autoimmune blood system with one that lacks the autoimmune risk genes. The HSC transplants cured mice that were in the process of disease development when nonmyeloablative conditioning was used for transplant.169 It has been observed that transplant-induced tolerance allows co-transplantation of pancreatic islet cells to replace destroyed islets.170 If these results using nonmyeloablative conditioning can be translated to humans, type 1 diabetes and several other autoimmune diseases may be treatable with pure HSC grafts. However, the reader should be cautioned that the translation of treatments from mice to humans is often complicated and time-consuming.

Banking is currently a routine procedure for UCB samples. If expansion of fully functional HSCs in tissue culture becomes a reality, HSC transplants may be possible by starting with small collections of HSCs rather than massive numbers acquired through mobilization and apheresis. With such a capability, collections of HSCs from volunteer donors or umbilical cords could be theoretically converted into storable, expandable stem cell banks useful on demand for clinical transplantation and/or for protection against radiation accidents. In mice, successful HSC transplants that regenerate fully normal immune and blood-forming systems can be accomplished when there is only a partial transplantation antigen match. Thus, the establishment of useful human HSC banks may require a match between as few as three out of six transplantation antigens (HLA). This might be accomplished with stem cell banks of as few as 4,00010,000 independent samples.

Leukemias are proliferative diseases of the hematopoietic system that fail to obey normal regulatory signals. They derive from stem cells or progenitors of the hematopoietic system and almost certainly include several stages of progression. During this progression, genetic and/or epigenetic changes occur, either in the DNA sequence itself (genetic) or other heritable modifications that affect the genome (epigenetic). These (epi)genetic changes alter cells from the normal hematopoietic system into cells capable of robust leukemic growth. There are a variety of leukemias, usually classified by the predominant pathologic cell types and/or the clinical course of the disease. It has been proposed that these are diseases in which self-renewing but poorly regulated cells, so-called "leukemia stem cells" (LSCs), are the populations that harbor all the genetic and epigenetic changes that allow leukemic progression.171176 While their progeny may be the characteristic cells observed with the leukemia, these progeny cells are not the self-renewing "malignant" cells of the disease. In this view, the events contributing to tumorigenic transformation, such as interrupted or decreased expression of "tumor suppressor" genes, loss of programmed death pathways, evasion of immune cells and macrophage surveillance mechanisms, retention of telomeres, and activation or amplification of self-renewal pathways, occur as single, rare events in the clonal progression to blast-crisis leukemia. As LT HSCs are the only selfrenewing cells in the myeloid pathway, it has been proposed that most, if not all, progression events occur at this level of differentiation, creating clonal cohorts of HSCs with increasing malignancy (see Figure 2.6). In this disease model, the final event, explosive selfrenewal, could occur at the level of HSC or at any of the known progenitors (see Figures 2.5 and 2.6). Activation of the -catenin/lef-tcf signal transduction and transcription pathway has been implicated in leukemic stem cell self-renewal in mouse AML and human CML.177 In both cases, the granulocyte-macrophage progenitors, not the HSCs or progeny blast cells, are the malignant self-renewing entities. In other models, such as the JunB-deficient tumors in mice and in chronic-phase CML in humans, the leukemic stem cell is the HSC itself.90,177 However, these HSCs still respond to regulatory signals, thus representing steps in the clonal progression toward blast crisis (see Figure 2.6).

Figure 2.6. Leukemic progression at the hematopoietic stem cell level. Self-renewing HSCs are the cells present long enough to accumulate the many activating events necessary for full transformation into tumorigenic cells. Under normal conditions, half of the offspring of HSC cell divisions would be expected to undergo differentiation, leaving the HSC pool stable in size. (A) (Pre) leukemic progression results in cohorts of HSCs with increasing malignant potential. The cells with the additional event (two events are illustrated, although more would be expected to occur) can outcompete less-transformed cells in the HSC pool if they divide faster (as suggested in the figure) or are more resistant to differentiation or apoptosis (cell death), two major exit routes from the HSC pool. (B) Normal HSCs differentiate into progenitors and mature cells; this is linked with limited proliferation (left). Partially transformed HSCs can still differentiate into progenitors and mature cells, but more cells are produced. Also, the types of mature cells that are produced may be skewed from the normal ratio. Fully transformed cells may be completely blocked in terminal differentiation, and large numbers of primitive blast cells, representing either HSCs or self-renewing, transformed progenitor cells, can be produced. While this sequence of events is true for some leukemias (e.g., AML), not all of the events occur in every leukemia. As with non-transformed cells, most leukemia cells (other than the leukemia stem cells) can retain the potential for (limited) differentiation.

Many methods have revealed contributing protooncogenes and lost tumor suppressors in myeloid leukemias. Now that LSCs can be isolated, researchers should eventually be able to assess the full sequence of events in HSC clones undergoing leukemic transformation. For example, early events, such as the AML/ETO translocation in AML or the BCR/ABL translocation in CML can remain present in normal HSCs in patients who are in remission (e.g., without detectable cancer).177,178 The isolation of LSCs should enable a much more focused attack on these cells, drawing on their known gene expression patterns, the mutant genes they possess, and the proteomic analysis of the pathways altered by the proto-oncogenic events.173,176,179 Thus, immune therapies for leukemia would become more realistic, and approaches to classify and isolate LSCs in blood could be applied to search for cancer stem cells in other tissues.180

After more than 50 years of research and clinical use, hematopoietic stem cells have become the best-studied stem cells and, more importantly, hematopoietic stem cells have seen widespread clinical use. Yet the study of HSCs remains active and continues to advance very rapidly. Fueled by new basic research and clinical discoveries, HSCs hold promise for such indications as treating autoimmunity, generating tolerance for solid organ transplants, and directing cancer therapy. However, many challenges remain. The availability of (matched) HSCs for all of the potential applications continues to be a major hurdle. Efficient expansion of HSCs in culture remains one of the major research goals. Future developments in genomics and proteomics, as well as in gene therapy, have the potential to widen the horizon for clinical application of hematopoietic stem cells even further.

Notes:

* Cellerant Therapeutics, 1531 Industrial Road, San Carlos, CA 94070. Current address: Department of Surgery, Arizona Health Sciences Center, 1501 N. Campbell Avenue, P.O. Box 245071, Tucson, AZ 857245071,e-mail: jdomen@surgery.arizona.edu.

** Section on Developmental and Stem Cell Biology, Joslin Diabetes Center, One Joslin Place, Boston, MA 02215, E-mail: Amy_Wagers@harvard.edu

*** Director, Institute for Cancer/Stem Cell Biology and Medicine, Professor of Pathology and Developmental Biology, Stanford University School of Medicine, Stanford, CA 94305, Irv@stanford.edu.

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In June 2016 researchers in Canada published results of a long-term HSCT trial involving 24 people with aggressive relapsing-remitting MS whose disease was not controlled with available therapies. Three years after the procedure, 70% remained free of disease activity, with no relapses, no new MRI-detected inflammatory brain lesions, and no signs of progression. None of the surviving participants experienced clinical relapses or required MS disease-modifying therapies to control their disease, and 40% experienced reductions in disability. One participant died and another required intensive hospital care for liver complications. All participants developed fevers, which were frequently associated with infections, and other toxicities.Read more about this study

A multi-center, 5-year trial called theHALT MS Study tested HSCT in 25 people with MS and active disease that was not controlled by disease-modifying medications. The trial was funded by the National Institutes of Health and the Immune Tolerance Network. Results presented at the June 2016 Annual Meeting of the Consortium of MS Centers suggest that after five years, 69% of participants experienced no new disease activity after the procedure and did not need disease-modifying therapies to control their disease. Most side effects related to blood cell reductions and infections. When the complete data are published, this trial will be an important addition to research needed to determine whether this approach to stem cell transplantation is safe and effective in people with MS.

In October 2015, researchers at the University of Genoa and other institutions in Italy reported on a small trial of HSCT in seven people with very active relapsing-remitting MS that was not controlled with MS disease-modifying therapy. They underwent a low-intensity lympho-ablative regimen in which the immune system was suppressed but not completely depleted before the stem cell transplant as an approach to reducing toxicity. The investigators did MRI scans (for 3 years) and clinical evaluations (for 5 years). They found dramatic reductions of MRI-detected inflammation after the procedure, but did not achieve complete absence of inflammation. After 5 years, two participants remained stable, one significantly improved, and four had mild disease progression. One experienced a relapse after treatment. No severe side effects occurred. The authors conclude that the low-intensity regimen they used was not sufficient to treat aggressive MS.Read an abstract from the paper(Multiple Sclerosis 2015 Oct;21(11):1423-30) In January 2015, doctors at Northwestern University published their10-year experience of treating people with HSCT. The report included 123 people with relapsing-remitting MS and 28 with secondary-progressive MS. Their method is nonmyeloblative HSCT, in which the immune system is suppressed but not completely depleted before the stem cell transplant. Individuals were followed from 6 months to 5 years, or an average of 2.5 years. The EDSS disability scores improved, compared to pretreatment, by one point or more in 64% of those followed out to year 4. Relapses and MRI-detected disease activity were also reduced. In evaluating which type of individuals benefited from the therapy, the doctors suggested that people with relapsing-remitting MS who had had MS for ten years or less showed improvements in their disability scores, whereas those with secondary-progressive MS or disease duration greater than ten years did not show improvements on their disability scores. They reported no treatment-related deaths or serious infections. ITP (immune-mediated thrombocytopenia), a potentially serious bleeding disorder, developed in 7 people, and thyroid disorders developed in 7 people.Read a summary of their resultsor thepaper in JAMA (Published onlineJanuary 20, 2015).

Ongoing Research in HSCT Additional research is focusing on figuring out who might benefit from this procedure and how to reduce its risks. HSCTis being investigated in Canada, the United States, Europe and elsewhere. For example:

An internationalclinical trialof this procedure, being led by Dr. Richard Burt of Northwestern University in Chicago, is now recruiting individuals who have not responded to other disease-modifying therapies. THIS TRIAL IS CURRENTLY RECRUITING PARTICIPANTS at its sites at Northwestern University, Rush University Medical Center, University of Sao Paulo, Uppsala University and Sheffield Teaching Hospitals NHS Foundation Trust.Read moreabout who may be eligible to participate.Dr. Burt and colleaguesrecently publisheda case series exploring outcomes for individuals who underwent the procedure.

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Bone Marrow Stem Cell Transplant HSCT - National ...

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Introduction

A bone marrow transplant, alsoknown as a haemopoietic stem cell transplant, replaces damaged bone marrow with healthy bone marrow stem cells.

Bone marrow is aspongytissue found in the hollow centres of some bones. It contains specialist stem cells, which produce the body's blood cells.

Stem cells in bone marrow produce three important types of blood cells:

Bone marrow transplants are often needed to treat conditions thatdamage bone marrow. If bone marrow is damaged, it is no longer able to produce normal blood cells. The new stem cells take over blood cellproduction.

Conditions that bone marrow transplants are used to treat include:

Read more about why a bone marrow transplantis needed.

A bone marrow transplant involves taking healthy stem cells from the bone marrow of one person and transferring them to the bone marrow of another person.

In some cases, it may be possible to take the bone marrow from your own body. This is known as an autologous transplantation. Before it is returned, the bone marrow is cleared of any damaged or diseased cells.

A bone marrowtransplant has five stages. These are:

Having a bone marrow transplant can be an intensive and challenging experience. Many people take up to a year to fully recover from the procedure.

Read more about what happens during a bone marrow transplant.

Bone marrow transplants are usually only recommended if:

Read more about who can have a bone marrow transplant.

Bone marrow transplants arecomplicated procedures with significant risks.

In some cases, the transplanted cells (graft cells) recognise the recipient's cells as "foreign"and try to attack them. This is known as graft versus host disease (GvHD).

The risk of infectionis alsoincreased because your immune system is weakened when you're conditioned (prepared) for the transplant.

Read more about the risks of having a bone marrow transplant.

It's nowpossible to harvest stem cells from sources other than bone marrow.

Peripheral blood stem cell donation involves injectinga medicine into the donor's blood thatcauses the stem cells to moveout of the bone marrow and into the bloodstream where theycan be harvested (collected).

The advantage of this type of stem cell donation is that the donor doesn't needa general anaesthetic.

Stem cells can also be collectedfrom the placenta and umbilical cord of a newborn baby and stored in a laboratory until they're needed.

Cord blood stem cells are very usefulbecause they don't need to be as closely matched as bone marrow or peripheral blood stem cells for a successful outcome.

Find out more about theNHS Cord Blood Bank(external link).

Page last reviewed: 18/02/2014

Next review due: 18/02/2016

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Bone marrow transplant - NHS Choices

Bone Marrow Stem Cells Comments Off on Bone marrow transplant – NHS Choices | October 28th, 2015

Hematopoietic stem cell transplantation (HSCT) is the transplantation of multipotent hematopoietic stem cells, usually derived from bone marrow, peripheral blood, or umbilical cord blood. It may be autologous (the patient's own stem cells are used) or allogeneic (the stem cells come from a donor). It is a medical procedure in the field of hematology, most often performed for patients with certain cancers of the blood or bone marrow, such as multiple myeloma or leukemia. In these cases, the recipient's immune system is usually destroyed with radiation or chemotherapy before the transplantation. Infection and graft-versus-host disease are major complications of allogeneic HSCT.

Hematopoietic stem cell transplantation remains a dangerous procedure with many possible complications; it is reserved for patients with life-threatening diseases. As survival following the procedure has increased, its use has expanded beyond cancer, such as autoimmune diseases.[1][2]

Indications for stem cell transplantation are as follows:

Many recipients of HSCTs are multiple myeloma[3] or leukemia patients[4] who would not benefit from prolonged treatment with, or are already resistant to, chemotherapy. Candidates for HSCTs include pediatric cases where the patient has an inborn defect such as severe combined immunodeficiency or congenital neutropenia with defective stem cells, and also children or adults with aplastic anemia[5] who have lost their stem cells after birth. Other conditions[6] treated with stem cell transplants include sickle-cell disease, myelodysplastic syndrome, neuroblastoma, lymphoma, Ewing's sarcoma, desmoplastic small round cell tumor, chronic granulomatous disease and Hodgkin's disease. More recently non-myeloablative, "mini transplant(microtransplantation)," procedures have been developed that require smaller doses of preparative chemo and radiation. This has allowed HSCT to be conducted in the elderly and other patients who would otherwise be considered too weak to withstand a conventional treatment regimen.

A total of 50,417 first hematopoietic stem cell transplants were reported as taking place worldwide in 2006, according to a global survey of 1327 centers in 71 countries conducted by the Worldwide Network for Blood and Marrow Transplantation. Of these, 28,901 (57 percent) were autologous and 21,516 (43 percent) were allogeneic (11,928 from family donors and 9,588 from unrelated donors). The main indications for transplant were lymphoproliferative disorders (54.5 percent) and leukemias (33.8 percent), and the majority took place in either Europe (48 percent) or the Americas (36 percent).[7] In 2009, according to the World Marrow Donor Association, stem cell products provided for unrelated transplantation worldwide had increased to 15,399 (3,445 bone marrow donations, 8,162 peripheral blood stem cell donations, and 3,792 cord blood units).[8]

Autologous HSCT requires the extraction (apheresis) of haematopoietic stem cells (HSC) from the patient and storage of the harvested cells in a freezer. The patient is then treated with high-dose chemotherapy with or without radiotherapy with the intention of eradicating the patient's malignant cell population at the cost of partial or complete bone marrow ablation (destruction of patient's bone marrow function to grow new blood cells). The patient's own stored stem cells are then transfused into his/her bloodstream, where they replace destroyed tissue and resume the patient's normal blood cell production. Autologous transplants have the advantage of lower risk of infection during the immune-compromised portion of the treatment since the recovery of immune function is rapid. Also, the incidence of patients experiencing rejection (graft-versus-host disease) is very rare due to the donor and recipient being the same individual. These advantages have established autologous HSCT as one of the standard second-line treatments for such diseases as lymphoma.[9]

However, for others cancers such as acute myeloid leukemia, the reduced mortality of the autogenous relative to allogeneic HSCT may be outweighed by an increased likelihood of cancer relapse and related mortality, and therefore the allogeneic treatment may be preferred for those conditions.[10] Researchers have conducted small studies using non-myeloablative hematopoietic stem cell transplantation as a possible treatment for type I (insulin dependent) diabetes in children and adults. Results have been promising; however, as of 2009[update] it was premature to speculate whether these experiments will lead to effective treatments for diabetes.[11]

Allogeneics HSCT involves two people: the (healthy) donor and the (patient) recipient. Allogeneic HSC donors must have a tissue (HLA) type that matches the recipient. Matching is performed on the basis of variability at three or more loci of the HLA gene, and a perfect match at these loci is preferred. Even if there is a good match at these critical alleles, the recipient will require immunosuppressive medications to mitigate graft-versus-host disease. Allogeneic transplant donors may be related (usually a closely HLA matched sibling), syngeneic (a monozygotic or 'identical' twin of the patient - necessarily extremely rare since few patients have an identical twin, but offering a source of perfectly HLA matched stem cells) or unrelated (donor who is not related and found to have very close degree of HLA matching). Unrelated donors may be found through a registry of bone marrow donors such as the National Marrow Donor Program. People who would like to be tested for a specific family member or friend without joining any of the bone marrow registry data banks may contact a private HLA testing laboratory and be tested with a mouth swab to see if they are a potential match.[12] A "savior sibling" may be intentionally selected by preimplantation genetic diagnosis in order to match a child both regarding HLA type and being free of any obvious inheritable disorder. Allogeneic transplants are also performed using umbilical cord blood as the source of stem cells. In general, by transfusing healthy stem cells to the recipient's bloodstream to reform a healthy immune system, allogeneic HSCTs appear to improve chances for cure or long-term remission once the immediate transplant-related complications are resolved.[13][14][15]

A compatible donor is found by doing additional HLA-testing from the blood of potential donors. The HLA genes fall in two categories (Type I and Type II). In general, mismatches of the Type-I genes (i.e. HLA-A, HLA-B, or HLA-C) increase the risk of graft rejection. A mismatch of an HLA Type II gene (i.e. HLA-DR, or HLA-DQB1) increases the risk of graft-versus-host disease. In addition a genetic mismatch as small as a single DNA base pair is significant so perfect matches require knowledge of the exact DNA sequence of these genes for both donor and recipient. Leading transplant centers currently perform testing for all five of these HLA genes before declaring that a donor and recipient are HLA-identical.

Race and ethnicity are known to play a major role in donor recruitment drives, as members of the same ethnic group are more likely to have matching genes, including the genes for HLA.[16]

As of 2013[update], there were at least two commercialized allogeneic cell therapies, Prochymal and Cartistem.[17]

To limit the risks of transplanted stem cell rejection or of severe graft-versus-host disease in allogeneic HSCT, the donor should preferably have the same human leukocyte antigens (HLA) as the recipient. About 25 to 30 percent of allogeneic HSCT recipients have an HLA-identical sibling. Even so-called "perfect matches" may have mismatched minor alleles that contribute to graft-versus-host disease.

In the case of a bone marrow transplant, the HSC are removed from a large bone of the donor, typically the pelvis, through a large needle that reaches the center of the bone. The technique is referred to as a bone marrow harvest and is performed under general anesthesia.

Peripheral blood stem cells[18] are now the most common source of stem cells for allogeneic HSCT. They are collected from the blood through a process known as apheresis. The donor's blood is withdrawn through a sterile needle in one arm and passed through a machine that removes white blood cells. The red blood cells are returned to the donor. The peripheral stem cell yield is boosted with daily subcutaneous injections of Granulocyte-colony stimulating factor, serving to mobilize stem cells from the donor's bone marrow into the peripheral circulation.

It is also possible to extract stem cells from amniotic fluid for both autologous or heterologous use at the time of childbirth.

Umbilical cord blood is obtained when a mother donates her infant's umbilical cord and placenta after birth. Cord blood has a higher concentration of HSC than is normally found in adult blood. However, the small quantity of blood obtained from an Umbilical Cord (typically about 50 mL) makes it more suitable for transplantation into small children than into adults. Newer techniques using ex-vivo expansion of cord blood units or the use of two cord blood units from different donors allow cord blood transplants to be used in adults.

Cord blood can be harvested from the Umbilical Cord of a child being born after preimplantation genetic diagnosis (PGD) for human leucocyte antigen (HLA) matching (see PGD for HLA matching) in order to donate to an ill sibling requiring HSCT.

Unlike other organs, bone marrow cells can be frozen (cryopreserved) for prolonged periods without damaging too many cells. This is a necessity with autologous HSC because the cells must be harvested from the recipient months in advance of the transplant treatment. In the case of allogeneic transplants, fresh HSC are preferred in order to avoid cell loss that might occur during the freezing and thawing process. Allogeneic cord blood is stored frozen at a cord blood bank because it is only obtainable at the time of childbirth. To cryopreserve HSC, a preservative, DMSO, must be added, and the cells must be cooled very slowly in a controlled-rate freezer to prevent osmotic cellular injury during ice crystal formation. HSC may be stored for years in a cryofreezer, which typically uses liquid nitrogen.

The chemotherapy or irradiation given immediately prior to a transplant is called the conditioning regimen, the purpose of which is to help eradicate the patient's disease prior to the infusion of HSC and to suppress immune reactions. The bone marrow can be ablated (destroyed) with dose-levels that cause minimal injury to other tissues. In allogeneic transplants a combination of cyclophosphamide with total body irradiation is conventionally employed. This treatment also has an immunosuppressive effect that prevents rejection of the HSC by the recipient's immune system. The post-transplant prognosis often includes acute and chronic graft-versus-host disease that may be life-threatening. However, in certain leukemias this can coincide with protection against cancer relapse owing to the graft versus tumor effect.[19]Autologous transplants may also use similar conditioning regimens, but many other chemotherapy combinations can be used depending on the type of disease.

A newer treatment approach, non-myeloablative allogeneic transplantation, also termed reduced-intensity conditioning (RIC), uses doses of chemotherapy and radiation too low to eradicate all the bone marrow cells of the recipient.[20]:320321 Instead, non-myeloablative transplants run lower risks of serious infections and transplant-related mortality while relying upon the graft versus tumor effect to resist the inherent increased risk of cancer relapse.[21][22] Also significantly, while requiring high doses of immunosuppressive agents in the early stages of treatment, these doses are less than for conventional transplants.[23] This leads to a state of mixed chimerism early after transplant where both recipient and donor HSC coexist in the bone marrow space.

Decreasing doses of immunosuppressive therapy then allows donor T-cells to eradicate the remaining recipient HSC and to induce the graft versus tumor effect. This effect is often accompanied by mild graft-versus-host disease, the appearance of which is often a surrogate marker for the emergence of the desirable graft versus tumor effect, and also serves as a signal to establish an appropriate dosage level for sustained treatment with low levels of immunosuppressive agents.

Because of their gentler conditioning regimens, these transplants are associated with a lower risk of transplant-related mortality and therefore allow patients who are considered too high-risk for conventional allogeneic HSCT to undergo potentially curative therapy for their disease. The optimal conditioning strategy for each disease and recipient has not been fully established, but RIC can be used in elderly patients unfit for myeloablative regimens, for whom a higher risk of cancer relapse may be acceptable.[20][22]

After several weeks of growth in the bone marrow, expansion of HSC and their progeny is sufficient to normalize the blood cell counts and re-initiate the immune system. The offspring of donor-derived hematopoietic stem cells have been documented to populate many different organs of the recipient, including the heart, liver, and muscle, and these cells had been suggested to have the abilities of regenerating injured tissue in these organs. However, recent research has shown that such lineage infidelity does not occur as a normal phenomenon[citation needed].

HSCT is associated with a high treatment-related mortality in the recipient (1 percent or higher)[citation needed], which limits its use to conditions that are themselves life-threatening. Major complications are veno-occlusive disease, mucositis, infections (sepsis), graft-versus-host disease and the development of new malignancies.

Bone marrow transplantation usually requires that the recipient's own bone marrow be destroyed ("myeloablation"). Prior to "engraftment" patients may go for several weeks without appreciable numbers of white blood cells to help fight infection. This puts a patient at high risk of infections, sepsis and septic shock, despite prophylactic antibiotics. However, antiviral medications, such as acyclovir and valacyclovir, are quite effective in prevention of HSCT-related outbreak of herpetic infection in seropositive patients.[24] The immunosuppressive agents employed in allogeneic transplants for the prevention or treatment of graft-versus-host disease further increase the risk of opportunistic infection. Immunosuppressive drugs are given for a minimum of 6-months after a transplantation, or much longer if required for the treatment of graft-versus-host disease. Transplant patients lose their acquired immunity, for example immunity to childhood diseases such as measles or polio. For this reason transplant patients must be re-vaccinated with childhood vaccines once they are off immunosuppressive medications.

Severe liver injury can result from hepatic veno-occlusive disease (VOD). Elevated levels of bilirubin, hepatomegaly and fluid retention are clinical hallmarks of this condition. There is now a greater appreciation of the generalized cellular injury and obstruction in hepatic vein sinuses, and hepatic VOD has lately been referred to as sinusoidal obstruction syndrome (SOS). Severe cases of SOS are associated with a high mortality rate. Anticoagulants or defibrotide may be effective in reducing the severity of VOD but may also increase bleeding complications. Ursodiol has been shown to help prevent VOD, presumably by facilitating the flow of bile.

The injury of the mucosal lining of the mouth and throat is a common regimen-related toxicity following ablative HSCT regimens. It is usually not life-threatening but is very painful, and prevents eating and drinking. Mucositis is treated with pain medications plus intravenous infusions to prevent dehydration and malnutrition.

Graft-versus-host disease (GVHD) is an inflammatory disease that is unique to allogeneic transplantation. It is an attack of the "new" bone marrow's immune cells against the recipient's tissues. This can occur even if the donor and recipient are HLA-identical because the immune system can still recognize other differences between their tissues. It is aptly named graft-versus-host disease because bone marrow transplantation is the only transplant procedure in which the transplanted cells must accept the body rather than the body accepting the new cells. Acute graft-versus-host disease typically occurs in the first 3 months after transplantation and may involve the skin, intestine, or the liver. High-dose corticosteroids such as prednisone are a standard treatment; however this immuno-suppressive treatment often leads to deadly infections. Chronic graft-versus-host disease may also develop after allogeneic transplant. It is the major source of late treatment-related complications, although it less often results in death. In addition to inflammation, chronic graft-versus-host disease may lead to the development of fibrosis, or scar tissue, similar to scleroderma; it may cause functional disability and require prolonged immunosuppressive therapy. Graft-versus-host disease is usually mediated by T cells, which react to foreign peptides presented on the MHC of the host[citation needed].

Graft versus tumor effect (GVT) or "graft versus leukemia" effect is the beneficial aspect of the Graft-versus-Host phenomenon. For example, HSCT patients with either acute, or in particular chronic, graft-versus-host disease after an allogeneic transplant tend to have a lower risk of cancer relapse.[25][26] This is due to a therapeutic immune reaction of the grafted donor T lymphocytes against the diseased bone marrow of the recipient. This lower rate of relapse accounts for the increased success rate of allogeneic transplants, compared to transplants from identical twins, and indicates that allogeneic HSCT is a form of immunotherapy. GVT is the major benefit of transplants that do not employ the highest immuno-suppressive regimens.

Graft versus tumor is mainly beneficial in diseases with slow progress, e.g. chronic leukemia, low-grade lymphoma, and some cases multiple myeloma. However, it is less effective in rapidly growing acute leukemias.[27]

If cancer relapses after HSCT, another transplant can be performed, infusing the patient with a greater quantity of donor white blood cells (Donor lymphocyte infusion).[27]

Patients after HSCT are at a higher risk for oral carcinoma. Post-HSCT oral cancer may have more aggressive behavior with poorer prognosis, when compared to oral cancer in non-HSCT patients.[28]

Prognosis in HSCT varies widely dependent upon disease type, stage, stem cell source, HLA-matched status (for allogeneic HCST) and conditioning regimen. A transplant offers a chance for cure or long-term remission if the inherent complications of graft versus host disease, immuno-suppressive treatments and the spectrum of opportunistic infections can be survived.[13][14] In recent years, survival rates have been gradually improving across almost all populations and sub-populations receiving transplants.[29]

Mortality for allogeneic stem cell transplantation can be estimated using the prediction model created by Sorror et al.,[30] using the Hematopoietic Cell Transplantation-Specific Comorbidity Index (HCT-CI). The HCT-CI was derived and validated by investigators at the Fred Hutchinson Cancer Research Center (Seattle, WA). The HCT-CI modifies and adds to a well-validated comorbidity index, the Charlson Comorbidity Index (CCI) (Charlson et al.[31]) The CCI was previously applied to patients undergoing allogeneic HCT but appears to provide less survival prediction and discrimination than the HCT-CI scoring system.

The risks of a complication depend on patient characteristics, health care providers and the apheresis procedure, and the colony-stimulating factor used (G-CSF). G-CSF drugs include filgrastim (Neupogen, Neulasta), and lenograstim (Graslopin).

Filgrastim is typically dosed in the 10 microgram/kg level for 45 days during the harvesting of stem cells. The documented adverse effects of filgrastim include splenic rupture (indicated by left upper abdominal or shoulder pain, risk 1 in 40000), Adult respiratory distress syndrome (ARDS), alveolar hemorrage, and allergic reactions (usually expressed in first 30 minutes, risk 1 in 300).[32][33][34] In addition, platelet and hemoglobin levels dip post-procedure, not returning to normal until one month.[34]

The question of whether geriatrics (patients over 65) react the same as patients under 65 has not been sufficiently examined. Coagulation issues and inflammation of atherosclerotic plaques are known to occur as a result of G-CSF injection.[33] G-CSF has also been described to induce genetic changes in mononuclear cells of normal donors.[33] There is evidence that myelodysplasia (MDS) or acute myeloid leukaemia (AML) can be induced by GCSF in susceptible individuals.[35]

Blood was drawn peripherally in a majority of patients, but a central line to jugular/subclavian/femoral veins may be used in 16 percent of women and 4 percent of men. Adverse reactions during apheresis were experienced in 20 percent of women and 8 percent of men, these adverse events primarily consisted of numbness/tingling, multiple line attempts, and nausea.[34]

A study involving 2408 donors (1860 years) indicated that bone pain (primarily back and hips) as a result of filgrastim treatment is observed in 80 percent of donors by day 4 post-injection.[34] This pain responded to acetaminophen or ibuprofen in 65 percent of donors and was characterized as mild to moderate in 80 percent of donors and severe in 10 percent.[34] Bone pain receded post-donation to 26 percent of patients 2 days post-donation, 6 percent of patients one week post-donation, and <2 percent 1 year post-donation. Donation is not recommended for those with a history of back pain.[34] Other symptoms observed in more than 40 percent of donors include myalgia, headache, fatigue, and insomnia.[34] These symptoms all returned to baseline 1 month post-donation, except for some cases of persistent fatigue in 3 percent of donors.[34]

In one metastudy that incorporated data from 377 donors, 44 percent of patients reported having adverse side effects after peripheral blood HSCT.[35] Side effects included pain prior to the collection procedure as a result of GCSF injections, post-procedural generalized skeletal pain, fatigue and reduced energy.[35]

A study that surveyed 2408 donors found that serious adverse events (requiring prolonged hospitalization) occurred in 15 donors (at a rate of 0.6 percent), although none of these events were fatal.[34] Donors were not observed to have higher than normal rates of cancer with up to 48 years of follow up.[34] One study based on a survey of medical teams covered approximately 24,000 peripheral blood HSCT cases between 1993 and 2005, and found a serious cardiovascular adverse reaction rate of about 1 in 1500.[33] This study reported a cardiovascular-related fatality risk within the first 30 days HSCT of about 2 in 10000. For this same group, severe cardiovascular events were observed with a rate of about 1 in 1500. The most common severe adverse reactions were pulmonary edema/deep vein thrombosis, splenic rupture, and myocardial infarction. Haematological malignancy induction was comparable to that observed in the general population, with only 15 reported cases within 4 years.[33]

Georges Math, a French oncologist, performed the first European bone marrow transplant in November 1958 on five Yugoslavian nuclear workers whose own marrow had been damaged by irradiation caused by a criticality accident at the Vina Nuclear Institute, but all of these transplants were rejected.[36][37][38][39][40] Math later pioneered the use of bone marrow transplants in the treatment of leukemia.[40]

Stem cell transplantation was pioneered using bone-marrow-derived stem cells by a team at the Fred Hutchinson Cancer Research Center from the 1950s through the 1970s led by E. Donnall Thomas, whose work was later recognized with a Nobel Prize in Physiology or Medicine. Thomas' work showed that bone marrow cells infused intravenously could repopulate the bone marrow and produce new blood cells. His work also reduced the likelihood of developing a life-threatening complication called graft-versus-host disease.[41]

The first physician to perform a successful human bone marrow transplant on a disease other than cancer was Robert A. Good at the University of Minnesota in 1968.[42] In 1975, John Kersey, M.D., also of the University of Minnesota, performed the first successful bone marrow transplant to cure lymphoma. His patient, a 16-year-old-boy, is today the longest-living lymphoma transplant survivor.[43]

At the end of 2012, 20.2 million people had registered their willingness to be a bone marrow donor with one of the 67 registries from 49 countries participating in Bone Marrow Donors Worldwide. 17.9 million of these registered donors had been ABDR typed, allowing easy matching. A further 561,000 cord blood units had been received by one of 46 cord blood banks from 30 countries participating. The highest total number of bone marrow donors registered were those from the USA (8.0 million), and the highest number per capita were those from Cyprus (15.4 percent of the population).[44]

Within the United States, racial minority groups are the least likely to be registered and therefore the least likely to find a potentially life-saving match. In 1990, only six African-Americans were able to find a bone marrow match, and all six had common European genetic signatures.[45]

Africans are more genetically diverse than people of European descent, which means that more registrations are needed to find a match. Bone marrow and cord blood banks exist in South Africa, and a new program is beginning in Nigeria.[45] Many people belonging to different races are requested to donate as there is a shortage of donors in African, Mixed race, Latino, Aboriginal, and many other communities.

In 2007, a team of doctors in Berlin, Germany, including Gero Htter, performed a stem cell transplant for leukemia patient Timothy Ray Brown, who was also HIV-positive.[46] From 60 matching donors, they selected a [CCR5]-32 homozygous individual with two genetic copies of a rare variant of a cell surface receptor. This genetic trait confers resistance to HIV infection by blocking attachment of HIV to the cell. Roughly one in 1000 people of European ancestry have this inherited mutation, but it is rarer in other populations.[47][48] The transplant was repeated a year later after a leukemia relapse. Over three years after the initial transplant, and despite discontinuing antiretroviral therapy, researchers cannot detect HIV in the transplant recipient's blood or in various biopsies of his tissues.[49] Levels of HIV-specific antibodies have also declined, leading to speculation that the patient may have been functionally cured of HIV. However, scientists emphasise that this is an unusual case.[50] Potentially fatal transplant complications (the "Berlin patient" suffered from graft-versus-host disease and leukoencephalopathy) mean that the procedure could not be performed in others with HIV, even if sufficient numbers of suitable donors were found.[51][52]

In 2012, Daniel Kuritzkes reported results of two stem cell transplants in patients with HIV. They did not, however, use donors with the 32 deletion. After their transplant procedures, both were put on antiretroviral therapies, during which neither showed traces of HIV in their blood plasma and purified CD4 T cells using a sensitive culture method (less than 3 copies/mL). However, the virus was once again detected in both patients some time after the discontinuation of therapy.[53]

Since McAllister's 1997 report on a patient with multiple sclerosis (MS) who received a bone marrow transplant for CML,[54] there have been over 600 reports of HSCTs performed primarily for MS.[55] These have been shown to "reduce or eliminate ongoing clinical relapses, halt further progression, and reduce the burden of disability in some patients" that have aggressive highly active MS, "in the absence of chronic treatment with disease-modifying agents".[55]

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Hematopoietic stem cell transplantation - Wikipedia, the ...

Bone Marrow Stem Cells Comments Off on Hematopoietic stem cell transplantation – Wikipedia, the … | October 23rd, 2015

Corresponding Author: Joshua M. Hare, MD, The Interdisciplinary Stem Cell Institute, University of Miami Miller School of Medicine, Biomedical Research Bldg/Room 908, PO Box 016960 (R-125), Miami, FL 33101 (jhare@med.miami.edu).

Published Online: November 6, 2012. doi:10.1001/jama.2012.25321

Author Contributions:Dr Hare had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Hare, Gerstenblith, DiFede Velazquez, George, Mendizabal, McNiece, Heldman.

Acquisition of data: Hare, Fishman, Gerstenblith, DiFede Velazquez, Zambrano, Suncion, Tracy, Johnston, Brinker, Breton, Davis-Sproul, Byrnes, George, Lardo, Mendizabal, Lowery, Wong Po Foo, Ruiz, Amador, Da Silva, McNiece, Heldman.

Analysis and interpretation of data: Hare, Fishman, Zambrano, Suncion, Tracy, Ghersin, Lardo, Schulman, Mendizabal, Altman, Ruiz, Amador, Da Silva, McNiece, Heldman.

Drafting of the manuscript: Hare, Fishman, Ghersin, Mendizabal, Ruiz, Amador, Heldman.

Critical revision of the manuscript for important intellectual content: Hare, Fishman, Gerstenblith, DiFede Velazquez, Suncion, Tracy, Johnston, Brinker, Breton, Davis-Sproul, Schulman, Byrnes, Geroge, Lardo, Mendizabal, Lowery, Rouy, Altman, Wong Po Foo, Ruiz, Da Silva, McNiece, Heldman.

Statistical analysis: Hare, Mendizabal, McNiece, Heldman.

Obtained funding: Hare, Lardo.

Administrative, technical, or material support: Hare, DiFede Velazquez, Zambrano, Suncion, Ghersin, Johnston, Breton, Davis-Sproul, Schulman, Byrnes, Lowery, Rouy, Altman, Wong Po Foo, Da Silva, McNiece, Heldman.

Study supervision: Hare, Fishman, Gerstenblith, Tracy, George, Schulman, Altman, Da Silva, McNiece, Heldman.

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Hare reported having a patent for cardiac cell-based therapy, receiving research support from and being a board member of Biocardia, having equity interest in Vestion Inc, and being a consultant for Kardia. Dr George reported serving on the board of GE Healthcare, consulting for ICON Medical Imaging, and receiving trademark royalties for fluoroperfusion imaging. Mr Mendizabal is an employee of EMMES Corporation. Drs Rouy, Altman, and Wong Po Foo are employees of Biocardia Inc. Dr McNiece reported being a consultant and board member of Proteonomix Inc. Dr Heldman reported having a patent for cardiac cell-based therapy, receiving research support from and being a board member of Biocardia, and having equity interest in Vestion Inc. No other authors reported any financial disclosures.

Funding/Support: This study was funded by the US National Heart, Lung, and Blood Institute (NHLBI) as part of the Specialized Centers for Cell-Based Therapy U54 grant (U54HL081028-01). Dr Hare is also supported by National Institutes of Health (NIH) grants RO1 HL094849, P20 HL101443, RO1 HL084275, RO1 HL107110, RO1 HL110737, and UM1HL113460. The NHLBI provided oversight of the clinical trial through the independent Gene and Cell Therapy Data and Safety Monitoring Board (DSMB). Biocardia Inc provided the Helical Infusion Catheters for the conduct of POSEIDON.

Role of the Sponsors: The NHLBI, NIH, and Biocardia Inc had no role in the design and conduct of the study; in the collection, management, analysis, and interpretation of the data; or in the preparation, review, or approval of the manuscript.

Additional Contributions: We thank the NHLBI Gene and Cell Therapy DSMB, the patients who participated in this trial, the bone marrow donors, the staff of the cardiac catheterization laboratories at the University of Miami Hospital and The Johns Hopkins Hospital. Erica Anderson, MA (EMMES Corporation), provided data management and Hongwei Tang, MD (TeraRecon Inc), provided consultation regarding CT imaging analysis. Ms Anderson received compensation for her contribution via the Specialized Centers for Cell-Based Therapy grant. Dr Tang did not receive any compensation for his contribution.

This article was corrected for errors on July 19, 2013.

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Bone Marrow Stem Cells Comments Off on JAMA | Comparison of Allogeneic vs Autologous Bone Marrow … | October 9th, 2015

A transplant of the stem cells that form in bone marrow can help people recover from certain types of cancers and blood and bone marrow disorders, but having a bone marrow or stem cell transplant can require a donation from someone.

The bones of the body are hollow and in the centre especially in the flat bones such as the breastbone and pelvis can be found a soft tissue known as bone marrow. This sponge-like substance produces stem cells. These are immature cells that constantly divide to produce new cells, some of which grow into mature blood cells used by the body. These include:

Stem cells need to divide rapidly to make millions of blood cells every day. Without these stem cells it would be impossible to survive.

People who have a condition that damages bone marrow may not have enough stem cells to produce normal blood cells. This can occur if there is a type of bone marrow failure or a genetic blood or immune system disorder.

In other cases, treating people with certain types of cancer sometimes requires giving very high doses of chemotherapy to kill the cancer cells in the body. Whole body radiotherapy may also be used to kill off the cancer cells. However, these treatments can also kill healthy cells in the body, including the stem cells in bone marrow.

People who may need a bone marrow transplant include those with:

The collected stem cells are added to a solution that is put into the body by using a drip, similar to receiving a blood transfusion. These cells enter the bloodstream and then travel to the bones, where they can start producing blood cells again. In people who have cancer, this is performed the day after treatment with chemotherapy or radiotherapy ends.

Because having a transplant involves being given different medicines and blood transfusions as well as the transplant itself, the patient may be given a central line, or central venous catheter. An operation will be performed to insert a thin tube through the skin near the collarbone and into a large vein near the heart.

The transplant itself isn't painful, but the person will need to remain in hospital for between 5 to 6 weeks while their bone marrow recovers, allowing time for the donated stem cells to settle in and start producing new cells. Antibiotics are often given to limit the risk of infection, which is particularly high during this period and the reason why the person may be placed in isolation. Blood transfusions may also be necessary until the bone marrow is making enough new blood cells. The person will also be monitored to ensure the stem cells have been accepted.

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Bone marrow (stem cell) transplant and donation

Bone Marrow Stem Cells Comments Off on Bone marrow (stem cell) transplant and donation | August 30th, 2015

People usually volunteer to donate stem cells for an allogeneic transplant either because they have a loved one or friend who needs a match or because they want to help people. Some people give their stem cells so they can get them back later for an autologous transplant.

People who want to donate stem cells or join a volunteer registry can speak with their doctors or contact the National Marrow Donor Program to find the nearest donor center. Potential donors are asked questions to make sure they are healthy enough to donate and dont pose a risk of infection to the recipient. For more information about donor eligibility guidelines, contact the National Marrow Donor Program or the donor center in your area (see the To learn more section for contact information).

A simple blood test is done to learn the potential donors HLA type. There may be a one-time, tax-deductible fee of about $75 to $100 for this test. People who join a volunteer donor registry will most likely have their tissue type kept on file until they reach age 60.

Pregnant women who want to donate their babys cord blood should make arrangements for it early in the pregnancy, at least before the third trimester. Donation is safe, free, and does not affect the birth process. For more, see the section called How umbilical cord blood is collected.

If a possible stem cell donor is a good match for a recipient, steps are taken to teach the donor about the transplant process and make sure he or she is making an informed decision. If a person decides to donate, a consent form must be signed after the risks of donating are fully discussed. The donor is not pressured take part. Its always a choice.

If a person decides to donate, a medical exam and blood tests will be done to make sure the donor is in good health.

This process is often called bone marrow harvest, and its done in an operating room. The donor is put under general anesthesia (given medicine to put them into a deep sleep so they dont feel pain) while bone marrow is taken. The marrow cells are taken from the back of the pelvic (hip) bone. A large needle is put through the skin and into the back of the hip bone. Its pushed through the bone to the center and the thick, liquid marrow is pulled out through the needle. This is repeated several times until enough marrow has been taken out (harvested). The amount taken depends on the donors weight. Often, about 10% of the donors marrow, or about 2 pints, are collected. This takes about 1 to 2 hours. The body will replace these cells within 4 to 6 weeks. If blood was taken from the donor before the marrow donation, its often given back to the donor at this time.

After the bone marrow is harvested, the donor is taken to the recovery room while the anesthesia wears off. The donor may then be taken to a hospital room and watched until fully alert and able to eat and drink. In most cases, the donor is free to leave the hospital within a few hours or by the next morning.

The donor may have soreness, bruising, and aching at the back of the hips and lower back for a few days. Over-the-counter acetaminophen (Tylenol) or non-steroidal anti-inflammatory drugs (such as aspirin, ibuprofen, or naproxen) are helpful. Some people may feel tired or weak, and have trouble walking for a few days. The donor might be told to take iron supplements until the number of red blood cells returns to normal. Most donors are back to their usual schedule in 2 to 3 days. But it could take 2 or 3 weeks before they feel completely back to normal.

There are few risks for donors and serious complications are rare. But bone marrow donation is a surgical procedure. Rare complications could include anesthesia reactions, infection, transfusion reactions (if a blood transfusion of someone elses blood is needed this doesnt happen if you get your own blood), or injury at the needle insertion sites. Problems such as sore throat or nausea may be caused by anesthesia.

Allogeneic stem cell donors do not have to pay for the harvesting because the recipients insurance company usually covers the cost.

Once the cells are collected, they are filtered through fine mesh screens. This prevents bone or fat particles from being given to the recipient. For an allogeneic or syngeneic transplant, the cells may be given to the recipient through a vein soon after they are harvested. Sometimes they are frozen, such as when the donor lives far away from the recipient.

For several days before starting the donation process, the donor is given a daily injection (shot) of filgrastim (Neupogen). This is a growth-factor drug that causes the bone marrow to make and release stem cells into the blood. Filgrastim can cause some side effects, the most common being bone pain and headaches. These may be helped by over-the-counter acetaminophen (Tylenol) or nonsteroidal anti-inflammatory drugs (like aspirin or ibuprofen). Nausea, sleeping problems, low-grade (mild) fevers, and tiredness are other possible effects. These go away once the injections are finished and collection is completed.

Blood is removed through a catheter (a thin, flexible plastic tube) that is put in a large vein in the arm or chest. Its then cycled through a machine that separates the stem cells from the other blood cells. The stem cells are kept while the rest of the blood is returned to the donor through the same catheter. This process is called apheresis (a-fur-REE-sis). It takes about 2 to 4 hours and is done as an outpatient procedure. Often the process needs to be repeated daily for a few days, until enough stem cells have been collected.

Possible side effects of the catheter can include trouble placing the catheter in the vein, a collapsed lung from catheter placement, blockage of the catheter, or infection of the catheter or at the area where it enters the vein. Blood clots are another possible side effect. During the apheresis procedure donors may have problems caused by low calcium levels from the anti-coagulant drug used to keep the blood from clotting in the machine. These can include feeling lightheaded or tingly, and having chills or muscle cramps. These go away after donation is complete, but may be treated by giving the donor calcium supplements.

The process of donating cells for yourself (autologous stem cell donation) is pretty much the same as when someone donates them for someone else (allogeneic donation). Its just that in autologous stem cell donation the donor is also the recipient, giving stem cells for his or her own use later on. For some people, there are a few differences. For instance, sometimes chemotherapy (chemo) is given before the filgrastim is used to tell the body to make stem cells. Also, sometimes it can be hard to get enough stem cells from a person with cancer. Even after several days of apheresis, there may not be enough for the transplant. This is more likely to be a problem if the patient has had certain kinds of chemo in the past, or if they have an illness that affects their bone marrow.

Sometimes a second drug called plerixafor (Mozobil) is used along with filgrastim in people with non-Hodgkin lymphoma or multiple myeloma. This boosts the stem cell numbers in the blood, and helps reduce the number of apheresis sessions needed to get enough stem cells. It may cause nausea, diarrhea, and sometimes, vomiting. There are medicines to help if these symptoms become a problem. Rarely the spleen can enlarge and even rupture. This can cause severe internal bleeding and requires emergency medical care. The patient should tell the doctor right away if they have any pain in their left shoulder or under their left rib cage which can be symptoms of this emergency.

Parents can donate their newborns cord blood to volunteer or public cord blood banks at no cost. This process does not pose any health risk to the infant. Cord blood transplants use blood that would otherwise be thrown away.

After the umbilical cord is clamped and cut, the placenta and umbilical cord are cleaned. The cord blood is put into a sterile container, mixed with a preservative, and frozen until needed.

Remember that if you want to donate or bank (save) your childs cord blood, you will need to arrange it before the baby is born. Some banks require you to set it up before the 28th week of pregnancy, although others accept later setups. Among other things, you will be asked to answer health questions and sign a consent form.

Many hospitals collect cord blood for donation, which makes it easier for parents to donate. For more about donating your newborns cord blood, call 1-800-MARROW2 (1-800-627-7692) or visit Be the Match.

Privately storing a babys cord blood for future use is not the same as donating cord blood. Its covered in the section called Other transplant issues.

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Whats it like to donate stem cells?

Bone Marrow Stem Cells Comments Off on Whats it like to donate stem cells? | August 29th, 2015

Date: 01 Aug 2015

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Tanshinone IIA (TSA) is a lipophilic diterpene purified from the Chinese herb Danshen, which exhibits potent antioxidant and anti-inflammatory properties. Effect of TSA remains largely uninvestigated on the osteogenic differentiation of bone marrow mesenchymal stem cells (BM-MSCs), which are widely used in cell-based therapy of bone diseases. In the present study, both ALP activity at day 7 and calcium content at day 24 were upregulated during the osteogenesis of mouse BM-MSCs treated with TSA (1 and 5M), demonstrating that it promoted the osteogenesis at both early and late stages. We found that TSA promoted osteogenesis and inhibited osteoclastogenesis, evident by RT-PCR analysis of osteogenic marker gene expressions. However, osteogenesis was inhibited by TSA at 20M. We further revealed that TSA (1 and 5M) upregulated BMP and Wnt signaling. Co-treatment with Wnt inhibitor DKK-1 or BMP inhibitor noggin significantly decreased the TSA-promoted osteogenesis, indicating that upregulation of BMP and Wnt signaling plays a significant role and contributes to the TSA-promoted osteogenesis. Of clinical interest, our study suggests TSA as a promising therapeutic strategy during implantation of BM-MSCs for a more effective treatment of bone diseases.

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Effects of Tanshinone IIA on osteogenic differentiation of ...

Bone Marrow Stem Cells Comments Off on Effects of Tanshinone IIA on osteogenic differentiation of … | August 1st, 2015

You will have a low white blood cell count after your treatment. This means you are more at risk of getting an infection. You are likely to get an infection from the normally harmless bacteria we all have in our digestive systems and on our skin.

To stop this from happening your nurse may give you tablets called gut sterilisers (antibiotics) and mouthwashes. And they will encourage you to have a shower each day.

You are also at risk of infection from food. The nurses on the ward will tell you and your relatives about the food you can and can't eat. The rules vary from hospital to hospital but you may be told that

Your room will be thoroughly cleaned every day. Your visitors will be asked to wash their hands before they come into your room. They may also have to wear disposable gloves and aprons. Visitors with coughs and colds are not allowed. Some hospitals don't allow you to have plants or flowers in your room because bacteria and fungi can grow in the soil or water, and may cause infection.

Even with all these precautions, most people do get an infection at some point and need to have antibiotics. You can help yourself by trying to do your mouth care properly and getting up to shower and have your bed changed even on the days you don't feel too good.

After a transplant you will have lost immunity to diseases you were vaccinated against as a child. The team caring for you will advise you about the immunisations you need and when. You should only have inactivated immunisations and not live ones. To lower the risk of you getting any of these infections it is important that all your family have the flu vaccine and any children have all their immunisations.

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Side effects of bone marrow and stem cell transplants ...

Bone Marrow Stem Cells Comments Off on Side effects of bone marrow and stem cell transplants … | July 23rd, 2015

High levels of active TGF- in the bone marrow and abnormalities in bone remodeling are associated with multiple skeletal disorders. Genetic mutations in the TGF- signaling pathway cause premature activation of matrix latent TGF- and may manifest with various skeletal defects. There are additional diseases that result in high levels of active TGF-, which may contribute to the pathology. Here, we discuss how abnormal TGF- signaling results in uncoupled bone remodeling, mainly by loss of site-directed recruitment of MSCs that causes aberrant bone formation. Direct or indirect inhibition of TGF- signaling may provide potential therapeutic options for these disorders.

Genetic disorders. The critical role of TGF-1 in the reversal phase of bone remodeling is demonstrated by the range of skeletal disorders resulting from mutations in genes involved in TGF-1 signaling. Camurati-Engelmann disease (CED), characterized by a fusiform thickening of the diaphysis of the long bones and skull, is caused by mutations in TGFB1 that result in premature activation of TGF-1 (7174). Approximately 11 different TGFB1 mutations have been identified from families affected by CED (75, 76). All of the mutations are located in the region encoding LAP, either destabilizing LAP disulfide bridging or affecting secretion of the protein, both of which increase TGF-1 signaling, as confirmed by in vitro cell cultures and mouse models. Bone histology sections from patients with CED show decreased trabecular connectivity despite normal bone histomorphometric parameters with respect to osteoblast and osteoclast numbers (76, 77), suggestive of uncoupled bone remodeling. In vitro, the ratio of active to total TGF-1 in conditioned medium from cells expressing the CED mutant TGF-1 is significantly higher and enhances MSC migration (18). Targeted recruitment of MSCs to the bone-remodeling site is likely disrupted, secondary to loss of a TGF- gradient.

Elevations in TGF- signaling have also been observed in many genetic connective tissue disorders with craniofacial, skeletal, skin, and cardiovascular manifestations, including Marfan syndrome (MFS), Loeys-Dietz syndrome (LDS), and Shprintzen-Goldberg syndrome (SGS). MFS is caused by mutations in fibrillin and often results in aortic dilation, myopia, bone overgrowth, and joint laxity. Fibrillin is deposited in the ECM and normally binds TGF-, rendering it inactive. In MFS, the decreased level of fibrillin enhances TGF- activity (78). LDS is caused by inactivating mutations in genes encoding TRI and TRII (79). Physical manifestations include arterial aneurysms, hypertelorism, bifid uvula/cleft palate, and bone overgrowth resulting in arachnodactyly, joint laxity, and scoliosis. Pathologic analyses of affected tissue suggest chronically elevated TGF- signaling, despite the inactivating mutation (79). The mechanism of enhanced TGF- signaling remains under investigation. SGS is caused by mutations in the v-ski avian sarcoma viral oncogene homolog (SKI; refs. 80, 81) and causes physical features similar to those of MFS plus craniosynostosis. SKI negatively regulates SMAD-dependent TGF- signaling by impeding SMAD2 and SMAD3 activation, preventing nuclear translocation of the SMAD4 complex, and inhibiting TGF- target gene output by competing with p300/CBP for SMAD binding and recruiting transcriptional repressor proteins, such as mSin3A and HDACs (8284).

The neurocutaneous syndrome neurofibromatosis type 1 (NF1) has been noted to have skeletal features similar to those of CED, MFS, and LDS, including kyphoscoliosis, osteoporosis, and tibial pseudoarthrosis. Hyperactive TGF-1 signaling has been implicated as the primary factor underlying the pathophysiology of the osseous defects in Nf1fl/Col2.3Cre mice, a model of NF1 that closely recapitulates the skeletal abnormalities found in human disease (85). The exact mechanisms mediating mutant neurofibrominassociated enhancement of TGF- production and signaling remain unknown.

Osteoarthritis. While genetic disorders are rare, they have provided critical insight into the pathophysiology of more common disorders. Uncoupled bone remodeling accompanies the onset of osteoarthritis. TGF-1 is activated in subchondral bone in response to altered mechanical loading in an anterior cruciate ligament transection (ACLT) mouse model of osteoarthritis (86). High levels of active TGF-1 induced formation of nestin+ MSC clusters via activation of ALK5-SMAD2/3. MSCs underwent osteoblast differentiation in these clusters, leading to formation of marrow osteoid islets. Transgenic expression of active TGF-1 in osteoblastic cells alone was sufficient to induce osteoarthritis, whereas direct inhibition of TGF- activity in subchondral bone attenuated the degeneration of articular cartilage. Knockout of Tgfbr2 in nestin+ MSCs reduced osteoarthritis development after ACLT compared with wild-type mice, which confirmed that MSCs are the target cell population of TGF- signaling. High levels of active TGF-1 in subchondral bone likely disrupt the TGF- gradient and interfere with targeted migration of MSCs. Furthermore, mutations of ECM proteins that bind to latent TGF-s, such as small leucine-rich proteoglycans (87) and fibrillin (88), or mutations in genes involved in activation of TGF-, such as in CED (76) and LDS (89), are associated with high osteoarthritis incidence. Osteoblast differentiation of MSCs in aberrant locations appears histologically as subchondral bone osteoid islets and alters the thickness of the subchondral plate and calcified cartilage zone, changes known to be associated with osteoarthritis (90, 91). A computer-simulated model found that a minor increase in the size of the subchondral bone (1%2%) causes significant changes in the mechanical load properties on articular cartilage, which likely leads to degeneration (86). Importantly, inhibition of the TGF- signaling pathway delayed the development of osteoarthritis in both mouse and rat models (86).

MSCs in bone loss. Aging leads to deterioration of tissue and organ function. Skeletal aging is especially dramatic: bone loss in both women and men begins as early as the third decade, immediately after peak bone mass. Aging bone loss occurs when bone formation does not adequately compensate for osteoclast bone resorption during remodeling. Age-associated osteoporosis was previously believed to be due to a decline in survival and function of osteoblasts and osteoprogenitors; however, recent work by Park and colleagues found that mature osteoblasts and osteoprogenitors are actually nonreplicative cells and require constant replenishment from bone marrow MSCs (92). When MSCs fail to migrate to bone-resorptive sites or are unable to commit and differentiate into osteoblasts, new bone formation is impaired. Therefore, insufficient recruitment of MSCs, or their differentiation to osteoblasts, at the bone remodeling surface may contribute to the decline in bone formation in the elderly.

There are multiple hypotheses regarding the decreased osteogenic potential of MSCs during aging. For example, during aging, the bone marrow environment has an increased concentration of ROS and lipid oxidation that may decrease osteoblast differentiation, yet increase osteoclast activity (93, 94). MSCs also undergo senescence, which decreases proliferative capacity and contributes to decreased bone formation (95, 96). Cellular senescence involves the secretion of a plethora of factors, including TGF-, which induces expression of cyclin-dependent kinase inhibitors 2A and 2B (p16INK4A and p15INK4B, respectively; refs. 97).

Microgravity experienced by astronauts during spaceflight causes severe physiological alterations in the human body, including a 1%2% loss of bone mass every month during spaceflight (98). Several studies have shown decreases in osteoblastic markers of bone formation and increases in bone resorption (99101). The underlying molecular mechanisms responsible for the apparent concurrent decrease in bone formation and increase in bone resorption remain under investigation. Work by the McDonald group suggests that bone remodeling may become uncoupled under zero-gravity conditions secondary to decreased RhoA activity and resultant changes in actin stress fiber formation (102). In modeled microgravity, cultured human MSCs exhibit disruption of F-actin stress fibers within three hours of initiation of microgravity; the fibers are completely absent after seven days. RhoA activity is significantly reduced, and introduction of an adenoviral construct expressing constitutively active RhoA can reverse the elimination of stress fibers, significantly increasing markers of osteoblast differentiation (102). Under zero-gravity conditions, RhoA is unable to bind to its receptor, and a sufficient number of MSCs may not be able to migrate correctly to the bone-resorptive site for osteoblast differentiation, ultimately leading to bone loss with every cycle of remodeling.

Bone metastases are a frequent complication of cancer and often have both osteolytic and osteoblastic features, indicative of dysregulated bone remodeling. The importance of the bone marrow microenvironment contributing to the spread of cancer was first described in 1889 (103), postulating that tumor cells can grow only if they are in a conducive environment. Activation of matrix TGF- during bone remodeling plays a central role in the initiation of bone metastases and tumor expansion by regulating osteolytic and prometastatic factors (reviewed in refs. 104110). For example, TGF- can induce osteoclastic bone destruction by upregulating tumor cell expression of PTHrP and IL-11. Additionally, upregulation of CXCR4 by TGF- may home cancer cells to bones.

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JCI - Bone marrow mesenchymal stem cells and TGF- ...

Bone Marrow Stem Cells Comments Off on JCI – Bone marrow mesenchymal stem cells and TGF- … | July 16th, 2015

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Haematopoietic stem cells and early lymphoid progenitors ...

Bone Marrow Stem Cells Comments Off on Haematopoietic stem cells and early lymphoid progenitors … | July 12th, 2015

See comment in PubMed Commons below N Engl J Med. 2012 Oct 18;367(16):1487-96. doi: 10.1056/NEJMoa1203517. Anasetti C, Logan BR, Lee SJ, Waller EK, Weisdorf DJ, Wingard JR, Cutler CS, Westervelt P, Woolfrey A, Couban S, Ehninger G, Johnston L, Maziarz RT, Pulsipher MA, Porter DL, Mineishi S, McCarty JM, Khan SP, Anderlini P, Bensinger WI, Leitman SF, Rowley SD, Bredeson C, Carter SL, Horowitz MM, Confer DL; Blood and Marrow Transplant Clinical Trials Network. Collaborators (182)

Horowitz MM, Carter SL, Confer DL, DiFronzo N, Wagner E, Merritt W, Wu R, Anasetti C, Logan BR, Lee SJ, Waller EK, Weisdorf DJ, Wingard JR, Couban S, Anderlini P, Bensinger WI, Leitman SF, Rowley SD, Carter SL, Karanes C, Horowitz MM, Confer DL, Allen C, Colby C, Gurgol C, Knust K, Foley A, King R, Mitchell P, Couban S, Pulsipher MA, Ehninger G, Johnston L, Khan SP, Maziarz RT, McCarty JM, Mineishi S, Porter DL, Bredeson C, Anasetti C, Lee S, Waller EK, Wingard JR, Cutler CS, Westervelt P, Woolfrey A, Logan BR, Carter SL, Lee SJ, Waller EK, Anasetti C, Logan BR, Lee SJ, Stadtmauer E, Wingard J, Vose J, Lazarus H, Cowan M, Wingard J, Westervelt P, Litzow M, Wu R, Geller N, Carter S, Confer D, Horowitz M, Poland N, Krance R, Carrum G, Agura E, Nademanee A, Sahdev I, Cutler C, Horwitz ME, Kurtzberg J, Waller EK, Woolfrey A, Rowley S, Brochstein J, Leber B, Wasi P, Roy J, Jansen J, Stiff PJ, Khan S, Devine S, Maziarz R, Nemecek E, Huebsch L, Couban S, McCarthy P, Johnston L, Shaughnessy P, Savoie L, Ball E, Vaughan W, Cowan M, Horn B, Wingard J, Silverman M, Abhyankar S, McGuirk J, Yanovich S, Ferrara J, Weisdorf D, Faber E Jr, Selby G, Rooms LM, Porter D, Agha M, Anderlini P, Lipton J, Pulsipher MA, Pulsipher MA, Shepherd J, Toze C, Kassim A, Frangoul H, McCarty J, Hurd D, DiPersio J, Westervelt P, Shenoy S, Agura E, Culler E, Axelrod F, Chambers L, Senaldi E, Nguyen KA, Engelman E, Hartzman R, Sutor L, Dickson L, Nademanee A, Khalife G, Lenes BA, Eames G, Sibley D, Gale P, Antin J, Ehninger G, Newberg NR, Gammon R, Montgomery M, Mair B, Rossmann S, Wada R, Waxman D, Ranlett R, Silverman M, Herzig G, Fried M, Atkinson E, Weitekamp L, Bigelow C, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Miller JP, Price T, Young C, Hilbert R, Oh D, Cable C, Smith JW, Kalmin ND, Schultheiss K, Beck T, Lankiewicz MW, Sharp D.

Randomized trials have shown that the transplantation of filgrastim-mobilized peripheral-blood stem cells from HLA-identical siblings accelerates engraftment but increases the risks of acute and chronic graft-versus-host disease (GVHD), as compared with the transplantation of bone marrow. Some studies have also shown that peripheral-blood stem cells are associated with a decreased rate of relapse and improved survival among recipients with high-risk leukemia.

We conducted a phase 3, multicenter, randomized trial of transplantation of peripheral-blood stem cells versus bone marrow from unrelated donors to compare 2-year survival probabilities with the use of an intention-to-treat analysis. Between March 2004 and September 2009, we enrolled 551 patients at 48 centers. Patients were randomly assigned in a 1:1 ratio to peripheral-blood stem-cell or bone marrow transplantation, stratified according to transplantation center and disease risk. The median follow-up of surviving patients was 36 months (interquartile range, 30 to 37).

The overall survival rate at 2 years in the peripheral-blood group was 51% (95% confidence interval [CI], 45 to 57), as compared with 46% (95% CI, 40 to 52) in the bone marrow group (P=0.29), with an absolute difference of 5 percentage points (95% CI, -3 to 14). The overall incidence of graft failure in the peripheral-blood group was 3% (95% CI, 1 to 5), versus 9% (95% CI, 6 to 13) in the bone marrow group (P=0.002). The incidence of chronic GVHD at 2 years in the peripheral-blood group was 53% (95% CI, 45 to 61), as compared with 41% (95% CI, 34 to 48) in the bone marrow group (P=0.01). There were no significant between-group differences in the incidence of acute GVHD or relapse.

We did not detect significant survival differences between peripheral-blood stem-cell and bone marrow transplantation from unrelated donors. Exploratory analyses of secondary end points indicated that peripheral-blood stem cells may reduce the risk of graft failure, whereas bone marrow may reduce the risk of chronic GVHD. (Funded by the National Heart, Lung, and Blood Institute-National Cancer Institute and others; ClinicalTrials.gov number, NCT00075816.).

Survival after Randomization in the Intention-to-Treat Analysis

The P value is from a stratified binomial comparison at the 2-year point. The P value from a stratified log-rank test was also not significant. A total of 75 patients in each group were still alive at 36 months.

N Engl J Med. 2012 October 18;367(16):10.1056/NEJMoa1203517.

Outcomes after Transplantation, According to Study Group

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Peripheral-blood stem cells versus bone marrow from ...

Bone Marrow Stem Cells Comments Off on Peripheral-blood stem cells versus bone marrow from … | July 8th, 2015

With Brigham and Womens Hospital and Boston Childrens Hospital, Dana-Farber has performed thousands of stem cell/bone marrow transplants for adult and pediatric patients with blood cancers and other serious illnesses.

Whats the difference between these two terms? As it turns out, the only real distinction is in the method of collecting the stem cells.

Lets start with the basics.

Stem cells are versatile cells with the ability to divide and develop into many other kinds of cells.

Hematopoietic stem cells produce red blood cells, which deliver oxygen throughout the body; white blood cells, which help ward off infections; and platelets, which allow blood to clot and wounds to heal.

While chemotherapy and/or radiation therapy are essential treatments for the majority of cancer patients, high doses can severely weakenand even wipe outhealthy stem cells. Thats where stem cell transplantation comes in.

Stem cell transplantation is a general term that describes the procedures performed by the Adult Stem Cell Transplantation Program at Dana-Farber/Brigham and Womens Cancer Center and the Pediatric Stem Cell Transplantation Program at Dana-Farber/Boston Childrens Cancer and Blood Disorders Center.

Stem cells for transplant can come from bone marrow or blood.

When stem cells are collected from bone marrow and transplanted into a patient, the procedure is known as a bone marrow transplant. If the transplanted stem cells came from the bloodstream, the procedure is called a peripheral blood stem cell transplantsometimes shortened to stem cell transplant.

Whether you hear someone talking about a stem cell transplant or a bone marrow transplant, they are still referring to stem cell transplantation. The only difference is where in the body the transplanted stem cells came from. The transplants themselves are the same.

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Stem Cell vs. Bone Marrow Transplant: Whats the ...

Bone Marrow Stem Cells Comments Off on Stem Cell vs. Bone Marrow Transplant: Whats the … | July 3rd, 2015

Having someone elses marrow or stem cells is called a donor transplant, or an allogeneic transplant. This is pronounced al-lo-jen-ay-ik.

The donors bone marrow cells must match your own as closely as possible. The most suitable donor is usually a close relative, such as a brother or sister. It is sometimes possible to find a match in an unrelated donor. Doctors call this a matched unrelated donor (MUD). To find out if there is a suitable donor for you, your doctor will contact The Anthony Nolan Bone Marrow Register and other UK based and international bone marrow registers.

To make sure that your donors cells match, you and the donor will have blood tests. These are to see how many of the proteins on the surface of their blood cells match yours. This is called tissue typing or HLA matching. HLA stands for human leucocyte antigen.

Once you have a donor and are in remission, you have high dose chemotherapy either on its own or with radiotherapy. A week later the donor goes into hospital and their stem cells or marrow are collected. You then have the stem cells or bone marrow as a drip through your central line.

If you've had a transplant from a donor, there is a risk of graft versus host disease (GVHD). This happens because the transplanted stem cells or bone marrow contain cells from your donor's immune system. These cells can sometimes recognise your own tissues as being foreign and attack them. This can be an advantage because the immune cells may also attack any leukaemia cells left after your treatment.

Acute GVHD starts within 100 days of the transplant and can cause

If you develop GVHD after your transplant, your doctor will prescribe medicines to damp down this immune reaction. These are called immunosuppressants.

Chronic GVHD starts more than 100 days after the transplant and you may have

Your doctor is likely to suggest that you stay out of the sun because GVHD skin rashes can often get worse in the sun.

There is detailed information about graft versus host disease in the section about coping physically with cancer.

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Bone marrow or stem cell transplants for AML | Cancer ...

Bone Marrow Stem Cells Comments Off on Bone marrow or stem cell transplants for AML | Cancer … | June 26th, 2015