Where are stem cells located in the adult body?
Adult stem cell
Discoveries in recent years have suggested that adult stem cells might have the ability to differentiate into cell types from different germ layers. For instance, neural stem cells from the brain, which are derived from ectoderm, can differentiate into ectoderm, mesoderm, and endoderm. Stem cells from the bone marrow, which is derived from mesoderm, can differentiate into liver, lung, GI tract and skin, which are derived from endoderm and mesoderm. This phenomenon is referred to as stem cell transdifferentiation or plasticity. It can be induced by modifying the growth medium when stem cells are cultured "in vitro" or transplanting them to an organ of the body different from the one they were originally isolated from. There is yet no consensus among biologists on the prevalence and physiological and therapeutic relevance of stem cell plasticity. More recent findings suggest that pluripotent stem cells may reside in blood and adult tissues in a dormant state. These cells are referred to as "Blastomere Like Stem Cells" and "very small embryonic like" – "VSEL" stem cells, and display pluripotency in vitro. As BLSC's and VSEL cells are present in virtually all adult tissues, including lung, brain, kidneys, muscles, and pancreas Co-purification of BLSC's and VSEL cells with other populations of adult stem cells may explain the apparent pluripotency of adult stem cell populations. However, recent studies have shown that both human and murine VSEL cells lack stem cell characteristics and are not pluripotent.
Adult stem cell
Stem cell function becomes impaired with age, and this contributes to progressive deterioration of tissue maintenance and repair. A likely important cause of increasing stem cell dysfunction is age-dependent accumulation of DNA damage in both stem cells and the cells that comprise the stem cell environment. (See also DNA damage theory of aging.)
Stem-cell line
A stem cell line is a group of stem cells that is cultured in vitro and can be propagated indefinitely. Stem cell lines are derived from either animal or human tissues and come from one of three sources: embryonic stem cells, adult stem cells, or induced stem cells. They are commonly used in research and regenerative medicine.
Endogenous regeneration
Santiago Ramon y Cajal, a neuroscience pioneer, concluded that the generation of neurons occurs only in the prenatal phase of human development, not after birth. This theory had long been the fundamental principle of neuroscience. However, in the mid-20th century, evidence of adult mammalian neurogenesis was found in rodent hippocampus and other region of the brain.
In the intact adult mammalian brain, neuroregeneration maintains the function and structure of the central nervous system (CNS). The most adult stem cells in the brain are found in the subventricular zone at the lateral walls of the lateral ventricle. Another region where neurogenesis takes place in the adult brain is the subgranular zone (SGZ) of the dentate gyrus in the hippocampus. While the exact mechanism that maintains functional NSCs in these regions is still unknown, NSCs have shown an ability to restore neurons and glia in response to certain pathological conditions. However, so far, this regeneration by NSCs is insufficient to restore the full function and structure of an injured brain. However, endogenous neuroregeneration, unlike using embryonic stem cell implantation, is anticipated to treat damaged CNS without immunogenesis or tumorigenesis.
Endogenous regeneration
During the early development of a human, neural stem cells lie in the germinal layer of the developing brain, ventricular and subventricular zones. In brain development, multipotent stem cells (those that can generate different types of cells) are present in these regions, and all of these cells differentiate into neural cell forms, such as neurons, oligodendrocytes and astrocytes. A long-held belief states that the multipotency of neural stem cells would be lost in the adult human brain. However, it is only "in vitro", using neurosphere and adherent monolayer cultures, stem cells that can be found in the adult mammalian brain that have shown mutipotent capacity, while the "in vivo" study is not convincing. Therefore, the term "neural progenitor" is used instead of "stem cell" to describe limited regeneration ability in the adult brain stem cell.
Dorairajan Balasubramanian
Balasubramanian is now working on stem cell biology and its use in restoring lost vision. He and his group have been successful in isolating the adult stem cells found in the limbus, around the cornea, and culturing them on human amniotic membrane. These cultured stem cells were, later, used to produce corneal epithelia that can be stitched on to human eye. Clinical tests on 200 patients who lost eyesight due to chemical or fire burns returned significantly good results with vision restoration to 20/20 levels, with or without subsequent corneal grafts or transplantation. These tests are reported to be the "largest successful human trial of adult stem cell therapy" in the world.
Stem cell theory of aging
There are also several challenges when it comes to therapeutic use of stem cells and their ability to replenish organs and tissues. First, different cells may have different lifespans even though they are originated from the same stem cells ("See" T-cells and erythrocytes), meaning that aging can occur differently in cells that have longer lifespans as opposed to the ones with shorter lifespans. Also, continual effort to replace the somatic cells may cause exhaustion of stem cells.
Adult stem cell
Endothelial stem cells are one of the three types of multipotent stem cells found in the bone marrow. They are a rare and controversial group with the ability to differentiate into endothelial cells, the cells that line blood vessels.
StemCells, Inc.
StemCells, Inc. is a public biopharmaceutical company headquartered in Newark, California, that is developing purified human neural stem cells (HuCNS-SCs) in the hopes of treating central nervous system disorders and paralysis. StemCells' HuCNS-SCs have the ability to differentiate into the three main types of cells found in the central nervous system: neurons, astrocytes and oligodendrocytes.
Stem-cell niche
Germline stem cells (GSCs) are found in organisms that continuously produce sperm and eggs until they are sterile. These specialized stem cells reside in the GSC niche, the initial site for gamete production, which is composed of the GSCs, somatic stem cells, and other somatic cells. In particular, the GSC niche is well studied in the genetic model organism "Drosophila melanogaster" and has provided an extensive understanding of the molecular basis of stem cell regulation.
Adult stem cell
Adult stem cells express transporters of the ATP-binding cassette family that actively pump a diversity of organic molecules out of the cell. Many pharmaceuticals are exported by these transporters conferring multidrug resistance onto the cell. This complicates the design of drugs, for instance neural stem cell targeted therapies for the treatment of clinical depression.
Subventricular zone
The subventricular zone (SVZ) is a term used to describe both embryonic and adult neural tissues in the vertebrate central nervous system (CNS). In embryonic life, the SVZ refers to a secondary proliferative zone containing neural progenitor cells, which divide to produce neurons in the process of neurogenesis. The primary neural stem cells of the brain and spinal cord, termed radial glial cells, reside in the ventricular zone (VZ) (so-called because the VZ lines the developing ventricles). In the developing cerebral cortex, which resides in the dorsal telencephalon, the SVZ and VZ are transient tissues that do not exist in the adult. However, the SVZ of the ventral telencephalon persists throughout life.
Adult stem cell
Olfactory adult stem cells have been successfully harvested from the human olfactory mucosa cells, which are found in the lining of the nose and are involved in the sense of smell. If they are given the right chemical environment these cells have the same ability as embryonic stem cells to develop into many different cell types. Olfactory stem cells hold the potential for therapeutic applications and, in contrast to neural stem cells, can be harvested with ease without harm to the patient. This means they can be easily obtained from all individuals, including older patients who might be most in need of stem cell therapies.
Stem cell
Embryonic stem cells (ESCs) are the cells of the inner cell mass of a blastocyst, formed prior to implantation in the uterus. In human embryonic development the blastocyst stage is reached 4–5 days after fertilization, at which time it consists of 50–150 cells. ESCs are pluripotent and give rise during development to all derivatives of the three 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 extraembryonic membranes or to the placenta.
G0 phase
Stem cells are cells with the unique ability to produce differentiated daughter cells and to preserve their stem cell identity through self-renewal.
In mammals, most adult tissues contain tissue-specific stem cells that reside in the tissue and proliferate to maintain homeostasis for the lifespan of the organism. These cells can undergo immense proliferation in response to tissue damage before differentiating and engaging in regeneration. Some tissue stem cells exist in a reversible, quiescent state indefinitely until being activated by external stimuli. Many different types of tissue stem cells exist, including muscle stem cells (MuSCs), neural stem cells (NSCs), intestinal stem cells (ISCs), and many others.
Stem cell
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. 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. ES cells, being pluripotent cells, require specific signals for correct differentiation—if 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. 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.
Stem-cell niche
By continuous intravital imaging in mice, researchers were able to explore the structure of the stem cell niche and to obtain the fate of individual stem cells (SCs) and their progeny over time in vivo. In particular in intestinal crypt, two distinct groups of SCs have been identified: the "border stem cells" located in the upper part of the niche at the interface with transit amplifying cells (TAs), and "central stem cells" located at the crypt base. The proliferative potential of the two groups was unequal and correlated with the cells' location (central or border). It was also shown that the two SC compartments acted in accord to maintain a constant cell population and a steady cellular turnover. A similar dependence of self-renewal potential on proximity to the niche border was reported in the context of hair follicle, in an in vivo live-imaging study.
Endogenous cardiac stem cell
The adult heart was previously thought to be a post mitotic organ without any regenerative capability. The identification of eCSCs has provided an explanation for the hitherto unexplained existence of a subpopulation of immature cycling myocytes in the adult myocardium. Indeed, recent evidence from a genetic fate-mapping study established that stem cells replenish adult mammalian cardiomyocytes lost by cardiac wear and tear and injury throughout the adult life. Moreover, it is now accepted that myocyte death and myocyte renewal are the two sides of the proverbial coin of cardiac homeostasis in which the eCSCs play a central role. These findings produced a paradigm shift in cardiac biology and opened new opportunities and approaches for future treatment of cardiac diseases by placing the heart squarely amongst other organs with regenerative potential such as the liver, skin, muscle, CNS. However, they have not changed the well-established fact that the working myocardium is mainly constituted of terminally differentiated contractile myocytes. This fact does not exclude, but is it fully compatible with the heart being endowed with a robust intrinsic regenerative capacity which resides in the presence of the eCSCs throughout the individual lifespan.
Stem cell controversy
The discovery of adult stem cells led scientists to develop an interest in the role of embryonic stem cells, and in separate studies in 1981 Gail Martin and Martin Evans derived pluripotent stem cells from the embryos of mice for the first time. This paved the way for Mario Capecchi, Martin Evans, and Oliver Smithies to create the first knockout mouse, ushering in a whole new era of research on human disease. In 1995 adult stem cell research with human use, patented (US PTO with effect from 1995). In fact human use published in World J Surg 1991 & 1999 (B G Matapurkar). Salhan, Sudha (August 2011). Textbook of Gynecology. JP Medical Ltd. pp. 625–. .
Bharadwaj, Aditya; Glasner, Peter E. (2009). Local Cells, Global Science: The Rise of Embryonic Stem Cell Research in India. Taylor & Francis. 
^ "Dr.B.G.Matapurkar gets US patent for surgical procedure for organ regeneration - Patents". www.pharmabiz.com.
^ "Method of organogenesis and tissue regeneration/repair using surgical techniques - US Patent 6227202 Claims". patentstorm.us.
Human body
Cells in the body function because of DNA. DNA sits within the nucleus of a cell. Here, parts of DNA are copied and sent to the body of the cell via RNA. The RNA is then used to create proteins which form the basis for cells, their activity, and their products. Proteins dictate cell function and gene expression, a cell is able to self-regulate by the amount of proteins produced. However, not all cells have DNA – some cells such as mature red blood cells lose their nucleus as they mature.
List of intestinal stem cell marker genes
In the adult intestine, the crypts of Lieberkühn are the niche for epithelial stem cells and contain all proliferative stem and progenitor cells. Differentiating cells exit the cell cycle and migrate out of the crypts and onto the surface epithelium of the intestine, where they perform their physiological role (e.g., nutrient absorption by enterocytes; mucous secretion by goblet cells) and are eventually shed into the lumen. Intestinal stem cells were first identified as such in the 1970s. Cheng and Leblond used autoradiography of phagosomes to track the fate of cells at the base of the crypts, and determined that slender cells interspersed among Paneth cells at the crypt base could give rise to all of the other cell types that constituted the intestinal epithelium. Due to their narrow shape and location, these cells were called crypt base columnar cells (CBCs). Potten and colleagues used a combination of DNA labeling and assessment of the response of the epithelium to high-dose radiation to identify label-retaining cells (LRCs) as putative stem cells, which were typically located around four cell positions above the bottom of the crypt, and were therefore also called "+4 cells". Later work suggested that these "+4 cells" may function as reserve or back-up stem cells, and further suggested that they divide slowly relative to the other progenitor cells in the crypt. Thus, these cells are also called quiescent stem cells.
Human brain
Mast cells are white blood cells that interact in the neuroimmune system in the brain. Mast cells in the central nervous system are present in the meninges; they mediate neuroimmune responses in inflammatory conditions and help to maintain the blood–brain barrier, particularly in brain regions where the barrier is absent. Across systems, mast cells serve as the main effector cell through which pathogens can affect the gut–brain axis.
NINDS brain trauma research
The use of stem cells to repair or replace damaged brain tissue is a new and exciting avenue of research. A neural stem cell is a special kind of cell that can multiply and give rise to other more specialized cell types. These cells are found in adult neural tissue and normally develop into several different cell types found within the central nervous system. NINDS researchers are investigating the ability of stem cells to develop into neurotransmitter-producing neurons, specifically dopamine-producing cells. Researchers are also looking at the power of stem cells to develop into oligodendrocytes, a type of brain cell that produces myelin, the fatty sheath that surrounds and insulates axons. One study in mice has shown that bone marrow stem cells can develop into neurons, demonstrating that neural stem cells are not the only type of stem cell that could be beneficial in the treatment of brain and nervous system disorders. At the moment, stem cell research for TBI is in its infancy, but future research may lead to advances for treatment and rehabilitation.
Stem cell controversy
Adult stem cells have provided many different therapies for illnesses such as Parkinson's disease, leukemia, multiple sclerosis, lupus, sickle-cell anemia, and heart damage (to date, embryonic stem cells have also been used in treatment), Moreover, there have been many advances in adult stem cell research, including a recent study where pluripotent adult stem cells were manufactured from differentiated fibroblast by the addition of specific transcription factors. Newly created stem cells were developed into an embryo and were integrated into newborn mouse tissues, analogous to the properties of embryonic stem cells.
Stem-cell therapy
Most stem cells intended for regenerative therapy are generally isolated either from the patient's bone marrow or from adipose tissue. Mesenchymal stem cells can differentiate into the cells that make up bone, cartilage, tendons, and ligaments, as well as muscle, neural and other progenitor tissues, they have been the main type of stem cells studied in the treatment of diseases affecting these tissues. The number of stem cells transplanted into damaged tissue may alter efficacy of treatment. Accordingly, stem cells derived from bone marrow aspirates, for instance, are cultured in specialized laboratories for expansion to millions of cells. Although adipose-derived tissue also requires processing prior to use, the culturing methodology for adipose-derived stem cells is not as extensive as that for bone marrow-derived cells. While it is thought that bone-marrow derived stem cells are preferred for bone, cartilage, ligament, and tendon repair, others believe that the less challenging collection techniques and the multi-cellular microenvironment already present in adipose-derived stem cell fractions make the latter the preferred source for autologous transplantation.
Human body
The body contains trillions of cells, the fundamental unit of life. At maturity, there are roughly 30–37 trillion cells in the body, an estimate arrived at by totaling the cell numbers of all the organs of the body and cell types. The body is also host to about the same number of non-human cells as well as multicellular organisms which reside in the gastrointestinal tract and on the skin. Not all parts of the body are made from cells. Cells sit in an extracellular matrix that consists of proteins such as collagen, surrounded by extracellular fluids. Of the 70 kg weight of an average human body, nearly 25 kg is non-human cells or non-cellular material such as bone and connective tissue.
Mast cell
Unlike other hematopoietic cells of the immune system, mast cells naturally occur in the human brain where they interact with the neuroimmune system. In the brain, mast cells are located in a number of structures that mediate visceral sensory (e.g., pain) or neuroendocrine functions or that are located along the blood–cerebrospinal fluid barrier, including the pituitary stalk, pineal gland, thalamus, and hypothalamus, area postrema, choroid plexus, and in the dural layer of the meninges near meningeal nociceptors. Mast cells serve the same general functions in the body and central nervous system, such as effecting or regulating allergic responses, innate and adaptive immunity, autoimmunity, and inflammation. Across systems, mast cells serve as the main effector cell through which pathogens can affect the gut–brain axis.
Embryonic stem cell
Embryonic stem cells (ES cells or ESCs) are pluripotent stem cells derived from the inner cell mass of a blastocyst, an early-stage pre-implantation embryo. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consist of 50–150 cells. Isolating the embryoblast, or inner cell mass (ICM) results in destruction of the blastocyst, a process which raises ethical issues, including whether or not embryos at the pre-implantation stage should have the same moral considerations as embryos in the post-implantation stage of development. Researchers are currently focusing heavily on the therapeutic potential of embryonic stem cells, with clinical use being the goal for many labs. Potential uses include the treatment of diabetes and heart disease. The cells are being studied to be used as clinical therapies, models of genetic disorders, and cellular/DNA repair. However, adverse effects in the research and clinical processes such as tumours and unwanted immune responses have also been reported.
Thymic epithelial cell
Thymic epithelial cells (TECs) are specialized cells with high degree of anatomic, phenotypic and functional heterogeneity that are located in the thymic epithelium within the thymic stroma. Thymus, as a primary lymphoid organ, mediates T cell development and maturation. Thymic microenvironment is established by TEC network filled with thymocytes in different developing stages. TECs and thymocytes are the most important components in the thymus, that are necessary for production functionally competent T lymphocytes and self tolerance. Dysfunction of TECs causes several immunodeficiencies and autoimmune diseases.
Stem-cell niche
Stem-cell niche refers to a microenvironment, within the specific anatomic location where stem cells are found, which interacts with stem cells to regulate cell fate. The word 'niche' can be in reference to the "in vivo" or "in vitro" stem-cell microenvironment. During embryonic development, various niche factors act on embryonic stem cells to alter gene expression, and induce their proliferation or differentiation for the development of the fetus. Within the human body, stem-cell niches maintain adult stem cells in a quiescent state, but after tissue injury, the surrounding micro-environment actively signals to stem cells to promote either self-renewal or differentiation to form new tissues. Several factors are important to regulate stem-cell characteristics within the niche: cell–cell interactions between stem cells, as well as interactions between stem cells and neighbouring differentiated cells, interactions between stem cells and adhesion molecules, extracellular matrix components, the oxygen tension, growth factors, cytokines, and the physicochemical nature of the environment including the pH, ionic strength (e.g. Ca concentration) and metabolites, like ATP, are also important. The stem cells and niche may induce each other during development and reciprocally signal to maintain each other during adulthood.
Hematopoietic stem cell
Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. This process occurs in the red bone marrow, in the core of most bones. In embryonic development, the red bone marrow is derived from the layer of the embryo called the mesoderm.
Adult stem cell
Neural stem cells share many properties with haematopoietic stem cells (HSCs). Remarkably, when injected into the blood, neurosphere-derived cells differentiate into various cell types of the immune system.
Adult neurogenesis
Neural stem cells (NSCs) are the self-renewing, multipotent cells that generate the main phenotypes of the nervous system.
Adult neurogenesis
Early neuroanatomists, including Santiago Ramón y Cajal, considered the nervous system fixed and incapable of regeneration. The first evidence of adult mammalian neurogenesis in the cerebral cortex was presented by Joseph Altman in 1962, followed by a demonstration of adult neurogenesis in the dentate gyrus of the hippocampus in 1963. In 1969, Joseph Altman discovered and named the rostral migratory stream as the source of adult generated granule cell neurons in the olfactory bulb. Up until the 1980s, the scientific community ignored these findings despite use of the most direct method of demonstrating cell proliferation in the early studies, i.e. 3H-thymidine autoradiography. By that time, Shirley Bayer (and Michael Kaplan) again showed that adult neurogenesis exists in mammals (rats), and Nottebohm showed the same phenomenon in birds sparking renewed interest in the topic. Studies in the 1990s finally put research on adult neurogenesis into a mainstream pursuit. Also in the early 1990s hippocampal neurogenesis was demonstrated in non-human primates and humans. More recently, neurogenesis in the cerebellum of adult rabbits has also been characterized. Further, some authors (particularly Elizabeth Gould) have suggested that adult neurogenesis may also occur in regions within the brain not generally associated with neurogenesis including the neocortex. However, others have questioned the scientific evidence of these findings, arguing that the new cells may be of glial origin. Recent research has elucidated the regulatory effect of GABA on neural stem cells. GABA's well-known inhibitory effects across the brain also affect the local circuitry that triggers a stem cell to become dormant. They found that diazepam (Valium) has a similar effect.
Stellate cell
Stellate cells are any neuron in the central nervous system that have a star-like shape formed by dendritic processes radiating from the cell body. Many Stellate cells are GABAergic and are located in the molecular layer of the cerebellum. Stellate cells are derived from dividing progenitors in the white matter of postnatal cerebellum. Dendritic trees can vary between neurons. There are two types of dendritic trees in the cerebral cortex, which include pyramidal cells, which are pyramid shaped and stellate cells which are star shaped. Dendrites can also aid neuron classification. Dendrites with spines are classified as spiny, those without spines are classified as aspinous. Stellate cells can be spiny or aspinous, while pyramidal cells are always spiny. Most common stellate cells are the inhibitory interneurons found within the upper half of the molecular layer in the cerebellum. Cerebellar stellate cells synapse onto the dendritic arbors of Purkinje cells and send inhibitory signals. Stellate neurons are sometimes found in other locations in the central nervous system; cortical spiny stellate cells are found in layer IVC of the V1 region in the visual cortex. In the somatosensory barrel cortex of mice and rats, glutamatergic (excitatory) spiny stellate cells are organized in the barrels of layer 4. They receive excitatory synaptic fibres from the thalamus and process feed forward excitation to 2/3 layer of V1 visual cortex to pyramidal cells. Cortical spiny stellate cells have a 'regular' firing pattern. Stellate cells are chromophobes, that is cells that does not stain readily, and thus appears relatively pale under the microscope.
Cerebellar Stellate Cells are inhibitory and GABAergic. Stellate and basket cells originate from the cerebellar ventricular zone (CVZ) along with Purkinje cells and Bergmann glia Due to their similarity, basket and stellate cells are grouped together when examined during migration, especially given they follow the same pathway. After mitosis, these cells start in the deep layer of the white matter and migrate up through the internal granular layer (IGL) and purkinje cell layer (PCL) until they reach the molecular layer. During their time in the molecular layer, they change orientation and positioning until they eventually end up in the middle portion of this layer, facing the rostrocaudal direction. Once in this layer, the stellate cells are guided to their correct placement by Bergman glial cells.
Neuroblast
Neuroblasts are mainly present as precursors of neurons during embryonic development; however, they also constitute one of the cell types involved in adult neurogenesis. Adult neurogenesis is characterized by neural stem cell differentiation and integration in the mature adult mammalian brain. This process occurs in the dentate gyrus of the hippocampus and in the subventricular zones of the adult mammalian brain. Neuroblasts are formed when a neural stem cell, which can differentiate into any type of mature neural cell (i.e. neurons, oligodendrocytes, astrocytes, etc.), divides and becomes a transit amplifying cell. Transit amplifying cells are slightly more differentiated than neural stem cells and can divide asymmetrically to produce postmitotic neuroblasts and glioblasts, as well as other transit amplifying cells. A neuroblast, a daughter cell of a transit amplifying cell, is initially a neural stem cell that has reached the "point of no return." A neuroblast has differentiated such that it will mature into a neuron and not any other neural cell type. Neuroblasts are being studied extensively as they have the potential to be used therapeutically to combat cell loss due to injury or disease in the brain, although their potential effectiveness is debated.
Cells4Life
A child's umbilical cord blood and tissue is usually stored by parents when they believe their children might inherit a genetic disorder. It is estimated that up to 100,000 parents have chosen to do so in the UK. Since stem cells can repair or replace almost any cell in the body, their storage may eliminate the need to search for a matching donor if the owner of the cells became ill. Stem cells could be used to treat over 80 illnesses and are currently being used on clinical trials for cerebral palsy, hearing loss, Alzheimer’s disease, and more. There have been more than a million hematopoietic stem cell transplantations in the world as of December 2012.
Blood
In vertebrates, the various cells of blood are made in the bone marrow in a process called hematopoiesis, which includes erythropoiesis, the production of red blood cells; and myelopoiesis, the production of white blood cells and platelets. During childhood, almost every human bone produces red blood cells; as adults, red blood cell production is limited to the larger bones: the bodies of the vertebrae, the breastbone (sternum), the ribcage, the pelvic bones, and the bones of the upper arms and legs. In addition, during childhood, the thymus gland, found in the mediastinum, is an important source of T lymphocytes.
The proteinaceous component of blood (including clotting proteins) is produced predominantly by the liver, while hormones are produced by the endocrine glands and the watery fraction is regulated by the hypothalamus and maintained by the kidney.
Mastocytosis
Mast cells are located in connective tissue, including the skin, the linings of the stomach and intestine, and other sites. They play an important role in the immune defence against bacteria and parasites. By releasing chemical "alarms" such as histamine, mast cells attract other key players of the immune defense system to areas of the body where they are needed.
Charles Philippe Leblond
From the studies of Leblond and his colleagues, it was concluded that the body has three types of cell populations:To mark his 65th birthday in 1975, Leblond was honored at an international symposium on the existence of stem cells in adult tissues; the resulting book, Stem Cells of Renewing Cell Populations, was the first formal, comprehensive account on the subject.
Stem cell
There are three known accessible sources of autologous adult stem cells in humans:
bone marrow, adipose tissue, and blood. 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 cell
Adult stem cells can, however, be artificially reverted to a state where they behave like embryonic stem cells (including the associated DNA repair mechanisms). This was done with mice as early as 2006 with future prospects to slow down human aging substantially. Such cells are one of the various classes of induced stem cells.
Plant stem cell
Callus, or dedifferentiated cells, are somatic cells that undergo dedifferentiation to give rise to totipotent embryogenic cells, which temporarily gains the ability to proliferate and/or regenerate an embryo. Since embryogenic cells were considered totipotent cells based on their ability to regenerate or develop into an embryo under given conditions, dedifferentiated cells were generally regarded as stem cells of plant: "…we propose to extend the concept of stem cells to include embryogenic stem cells that arise from plant somatic cells. We examine the cellular, physiological and molecular similarities and differences between plant meristematic stem cells and embryogenic stem cells originating directly from single somatic cells."
Plant stem
Stems are often specialized for storage, asexual reproduction, protection or photosynthesis, including the following:Stem usually consist of three tissues, dermal tissue, ground tissue and vascular tissue. The dermal tissue covers the outer surface of the stem and usually functions to waterproof, protect and control gas exchange. The ground tissue usually consists mainly of parenchyma cells and fills in around the vascular tissue. It sometimes functions in photosynthesis. Vascular tissue provides long distance transport and structural support. Most or all ground tissue may be lost in woody stems. The dermal tissue of aquatic plants stems may lack the waterproofing found in aerial stems. The arrangement of the vascular tissues varies widely among plant species.
Dendritic cell
Dendritic cells are present in those tissues that are in contact with the external environment, such as the skin (where there is a specialized dendritic cell type called the Langerhans cell) and the inner lining of the nose, lungs, stomach and intestines. They can also be found in an immature state in the blood. Once activated, they migrate to the lymph nodes where they interact with T cells and B cells to initiate and shape the adaptive immune response. At certain development stages they grow branched projections, the "dendrites" that give the cell its name (δένδρον or déndron being Greek for 'tree'). While similar in appearance, these are structures distinct from the dendrites of neurons. Immature dendritic cells are also called veiled cells, as they possess large cytoplasmic 'veils' rather than dendrites.
Stem cell
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. Research into stem cells grew out of findings by Ernest A. McCulloch and James E. Till at the University of Toronto in the 1960s.
Cellular differentiation
Pluripotent stem cells undergo further specialization into multipotent progenitor cells that then give rise to functional cells. Examples of stem and progenitor cells include: 
A pathway that is guided by the cell adhesion molecules consisting of four amino acids, arginine, glycine, asparagine, and serine, is created as the cellular blastomere differentiates from the single-layered blastula to the three primary layers of germ cells in mammals, namely the ectoderm, mesoderm and endoderm (listed from most distal (exterior) to proximal (interior)). The ectoderm ends up forming the skin and the nervous system, the mesoderm forms the bones and muscular tissue, and the endoderm forms the internal organ tissues.
Stem cell
The primitive stem cells located in the organs of fetuses are referred to as fetal stem cells.
There are two types of fetal stem cells:Adult stem cells, also called somatic (from Greek σωματικóς, "of the body") stem cells, are stem cells which maintain and repair the tissue in which they are found. They can be found in children, as well as adults.
Lymph node stromal cell
The interior of the lymph node has two regions: the cortex and the medulla. In the cortex, lymphoid tissue is organized into nodules. In the nodules, T lymphocytes (cells which help to fight viruses) are located in the "T cell zone". B lymphocytes (cells which help to fight certain bacteria) are located in the "B cell follicle". The primary B cell follicle matures in germinal centers. In the medulla are hematopoietic cells (which contribute to the formation of the blood) and stromal cells.
Adult stem cell
Hematopoietic stem cells are found in the bone marrow and umbilical cord blood and give rise to all the blood cell types.
Intestinal gland
Intestinal glands contain adult stem cells referred to as intestinal stem cells. These cells have been used in the field of stem biology to further understand stem cell niches, and to generate intestinal organoids.
Institute for Stem Cell Biology and Regenerative Medicine
Institute for Stem Cell Biology and Regenerative Medicine (inStem) is an autonomous research institute in Bangalore, dedicated to the study of stem cell biology and regenerative medicine research. inStem is funded by Department of Biotechnology and well-supported, with access to facilities at both National Centre for Biological Sciences (NCBS) and Centre for Cellular and Molecular Platforms (C-CAMP). Together these three institutions serve as part of the Bangalore Bio-Cluster. The institute is also the umbrella organization for three initiatives: inStem itself, the Center for Stem Cell Research (CSCR) located at CMC Vellore, and an Extramural Program in Stem Cell Research (EPiSTEM), a funding initiative for support of stem cell research nationwide.
CLE peptide
Meristematic cells give rise to various organs of the plant and keep the plant growing.There are two types of meristematic tissues 1) Apical Meristem 2) Lateral Meristem. The Apical Meristem is of two types; the shoot apical meristem (SAM) gives rise to organs like the leaves and flowers, while the root apical meristem (RAM) provides the meristematic cells for the future root growth. SAM and RAM cells divide rapidly and are considered indeterminate, in that they do not possess any defined end status. In that sense, the meristematic cells are frequently compared to the stem cells in animals, which have an analogous behavior and function. Within plants SAM cells play a major role in the overall growth and development, this is due to the fact that all cells making up the major parts of the plant come from the shoot apical meristem (SAM). There are three different important area found within the SAM and they include the central zone (CZ), the peripheral zone (PZ), and the rib meristem (RM). Each of these areas play an important in the production of new stem cells within the SAM. All SAMs are usually dome shaped and have structures that are layered and are described as the tunica and corpus. CLV3 plays an important role in regulating the production of stem cells within the Central Zone (CZ) region of the (SAM), this is also true for the cell promoting WUSCHEL (WUS) gene. The combination of these two genes regulates stem cell production by WUS negatively or positively regulating the production of stem cells by controlling the CLV3 gene.;
Plant stem cell
Plant stem cells are also characterized by their location in specialized structures called meristematic tissues, which are located in root apical meristem (RAM), shoot apical meristem (SAM), and vascular system ((pro)cambium or vascular meristem.)
Stem-cell therapy
Healthy adult brains contain neural stem cells which divide to maintain general stem-cell numbers, or become progenitor cells. In healthy adult laboratory animals, progenitor cells migrate within the brain and function primarily to maintain neuron populations for olfaction (the sense of smell). Pharmacological activation of endogenous neural stem cells has been reported to induce neuroprotection and behavioral recovery in adult rat models of neurological disorder.
Stem cell
Pluripotent adult stem cells are rare and generally small in number, but they can be found in umbilical cord blood and other tissues. Bone marrow is a rich source of adult stem cells, which have been used in treating several conditions including liver cirrhosis, chronic limb ischemia and endstage heart failure. The quantity of bone marrow stem cells declines with age and is greater in males than females during reproductive years. Much adult stem cell research to date has aimed to characterize their potency and self-renewal capabilities. 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).
Natural scientific research in Canada
The International Regulome Consortium is a Canadian-led international initiative, begun in 2004, the aim of which is to map the functional transcriptome or the genetic circuitry of stem cells. Planned as a follow-up to the Human Genome Project, the consortium is headquartered at the University of Ottawa and led by Dr. Michel Rudniki. In 2009, Dr. Andras Nagy, a biologist at Mount Sinai Hospital in Toronto, developed a practical way to transform mature human cells into the equivalent of embryonic stem cells, moving medicine one step closer to the use of these cells for the treatment of disease. Also in 2009, a team led by Dr. John Davies of the Institute of Biomaterials and Biomedical Engineering at the University of Toronto was the first in the world to isolate special stem cells, known as mesenchymal stem cells, and perform experiments showing that they could be used to regenerate specific types of human tissue. The cells themselves came from the umbilical cord tissue of newborn babies.
Sperm
Sperm is the male reproductive cell and is derived from the Greek word (σπέρμα) "sperma" (meaning "seed"). In the types of sexual reproduction known as anisogamy and its subtype oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell. A uniflagellar sperm cell that is motile is referred to as a spermatozoon, whereas a non-motile sperm cell is referred to as a spermatium. Sperm cells cannot divide and have a limited life span, but after fusion with egg cells during fertilization, a new organism begins developing, starting as a totipotent zygote. The human sperm cell is haploid, so that its 23 chromosomes can join the 23 chromosomes of the female egg to form a diploid cell. In mammals, sperm develops in the testicles, is stored in the epididymis, and released from the penis.
Keratinocyte
Epidermal stem cells reside in the lower part of the epidermis (stratum basale) and are attached to the basement membrane through hemidesmosomes. Epidermal stem cells divide in a random manner yielding either more stem cells or transit amplifying cells. Some of the transit amplifying cells continue to proliferate then commit to differentiate and migrate towards the surface of the epidermis. Those stem cells and their differentiated progeny are organized into columns named epidermal proliferation units.
Muse cell
A muse cell (multi-lineage differentiating stress enduring cell) is an endogenous non-cancerous pluripotent stem cell. They reside in the connective tissue of nearly every organ, bone marrow and peripheral blood. They are collectable from commercially obtainable mesenchymal cells such as human fibroblasts, bone marrow-mesenchymal stem cells and adipose-derived stem cells. Muse cells are able to generate cells representative of all three germ layers from a single cell both spontaneously and under cytokine induction. Expression of pluripotency genes and triploblastic differentiation are self-renewable over generations. Muse cells do not undergo teratoma formation when transplanted into a host environment in vivo. This can be explained in part by their intrinsically low telomerase activity, eradicating the risk of tumorigenesis through unbridled cell proliferation. They were discovered in 2010 by Mari Dezawa and her research group. An exploratory clinical trial has been started in January 2018, by a Mitsubishi Chemical Holdings company.Muse cells are identified as cells positive for SSEA-3+, a well-known marker for undifferentiated human ES cells. They are also positive for general mesenchymal stem cell markers such as CD105, CD90 and CD29. Therefore, Muse cells are double positive for pluripotent and mesenchymal stem cell markers. Cell isolation by SSEA-3 cell sorting can be done using SSEA-3 antibody. Their size is 13~15 μm in diameter. Muse cells do not express CD34 (markers for hematopoietic stem cells, adipose stem cells, VSELs) and CD117 (hematopoietic stem cells markers), Snai1 and Slug (skin-derived precursors markers), CD271 and Sox10 (neural crest-derived stem cells markers), NG2 and CD146 (perivascular cells) or CD31 and von Willebrand factor (endothelial progenitor markers). This indicates that Muse cells do not belong to previously investigated stem cell types.
Stem cell
During embryonic development the cells of the inner cell mass 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. 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.
Stem cell controversy
For many decades, stem cells have played an important role in medical research, beginning in 1868 when Ernst Haeckel first used the phrase to describe the fertilized egg which eventually gestates into an organism. The term was later used in 1886 by William Sedgwick to describe the parts of a plant that grow and regenerate. Further work by Alexander Maximow and Leroy Stevens introduced the concept that stem cells are pluripotent. This significant discovery led to the first human bone marrow transplant by E. Donnal Thomas in 1956, which although successful in saving lives, has generated much controversy since. This has included the many complications inherent in stem cell transplantation (almost 200 allogeneic marrow transplants were performed in humans, with no long-term successes before the first successful treatment was made), through to more modern problems, such as how many cells are sufficient for engraftment of various types of hematopoietic stem cell transplants, whether older patients should undergo transplant therapy, and the role of irradiation-based therapies in preparation for transplantation.
Neural stem cell
There are two basic types of stem cell: adult stem cells, which are limited in their ability to differentiate, and embryonic stem cells (ESCs), which are pluripotent and have the capability of differentiating into any cell type.
Gametogonium
Gametogonium (plural gametogonia) are stem cells for gametes located within the gonads. They originate from primordial germ cells, which have migrated to the gonads. Male gametogonia which are located within the testes during development and adulthood are called spermatogonium (plural spermatogonia). Female gametogonia, known as oogonium (plural oogonia), are found within the ovaries of the developing foetus and were thought to be depleted at or after birth. Spermatogonia and oogonia are classified as sexually differentiated germ cells.
Canadian Stem Cell Foundation
The Canadian Stem Cell Foundation is an independent, non-profit organization established in 2008 and situated in Ottawa, Ontario. Stem Cell science is a Canadian innovation through the discovery of stem cells by Drs. James Till and Ernest McCulloch. It is globally known as the leading organization for stem cell research and support in the study of treatments and cures for diseases such as cancer, diabetes, blindness and stroke.
Franz Ernst Christian Neumann
Legend of the stem cell-picture: Draft by Ernst Neumann himself, showing the "great-lymphozyt-stem-cell" (1912) or "great-lymphocyt" as stem cell for the postembryonic and embryonic development of erythropoiesis and leukopoiesis in the bone marrow and, as shown here, in the embryonic liver; GrLK: nucleus of great-lymphocyt-stem-cell; Erblk: Erythroblast; (Neumann 1914).
Beside, you find the first announcement of the bone marrow as blood forming organ. 
Translation: "In the so-called red bone marrow of man as well as the rabbit, one can regularly find, in addition to the well known marrow cell, certain other elements which have not been mentioned until now; namely nucleated red blood cells, in every respect corresponding to embryonic stages of the red blood cells. Also is the marrow rich in fat, the same cells are present but in lower quantity and their number decreases parallel to the decrease in the number of marrow cells and the increase in the number of fat cells (see above "Neumann-Law"). It is possible, to trace the origin of these elements in the blood of the marrow cells The high content of colorless elements in the blood of the marrow makes it likely that these is a migration of contractile marrow cells into the vessels. A thorough description of my observations will be published."
Stem cell transplantation for articular cartilage repair
Research into MSC’s has exploded in recent years. As an example, a PubMed search for the year 1999 reveals about 90 papers published under the MESH heading of “Mesenchymal Stem Cells”, the same search ran for the year 2007 reveals more than 4,000 entries.
The most commonly used source of MSC’s is bone marrow aspirate. Most of the adult bone marrow consists of blood cells in various stages of differentiation. These marrow components can be divided into plasma, red blood cells, platelets, and nucleated cells. The adult stem cell fraction is present in the nucleated cells of the marrow. Most of these cells are CD34+ heme progenitors (destined to differentiate into blood components), while very few are actually MSC’s capable of differentiating into bone, cartilage, or muscle. As a result, that leaves the very small number of MSC’s in the marrow as cells capable of differentiating into tissues of interest to joint preservation. Of note, this may be one of the reasons that commercially available centrifuge systems that concentrate marrow nucleated cells have not shown as much promise in animal research for cartilage repair as have approaches where MSC’s are expanded in culture to greater numbers.
Melanocyte
The precursor of the melanocyte is the melanoblast. In adults, stem cells are contained in the bulge area of the outer root sheath of hair follicles. When a hair is lost and the hair follicle regenerates, the stem cells are activated. These stem cells develop into both keratinocyte precursors and melanoblasts - and these melanoblasts supply both hair and skin (moving into the basal layer of the epidermis). There is additionally evidence that melanocyte stem cells are present in cutaneous nerves, with nerve signals causing these cells to differentiate into melanocytes for the skin.
Nova Southeastern University College of Dental Medicine
Stem cells have the ability to continuously divide and differentiate (develop) into various other kinds of cells/tissues. All tissues originate from fetal stem cells. Recently adult stem cells have been identified with the ability to create new tissues. We investigate stem cells that are taken from donor adult tissues, we do not conduct any research using fetal stem cells. Tissue engineering is the creation of new replacement tissues Potential patients that could benefit from stem cell therapies (millions):
Cardiovascular disease 58
Autoimmune diseases 30
Diabetes 16
Osteoporosis 10
Cancer 8.2
Alzheimer's disease 4.5
Parkinson's disease 1.5
Severe burns 0.3
Spinal cord injuries 0.25
Birth defects 0.15
Plant stem cell
Unlike animals, plants are immobile. As plants cannot escape from danger by taking motion, they need a special mechanism to withstand various and sometimes unforeseen environmental stress. Here, what empowers them to withstand harsh external influence and preserve life is stem cells. In fact, plants comprise the oldest and the largest living organisms on earth, including Bristlecone Pines in California, U.S. (4,842 years old), and the Giant Sequoia in mountainous regions of California, U.S. (87 meters in height and 2,000 tons in weight). This is possible because they have a modular body plan that enables them to survive substantial damage by initiating continuous and repetitive formation of new structures and organs such as leaves and flowers.
Floor plate
The spinal cord ependymal cells also reside in the FP region of the spinal cord. These cells are a neural stem cell population responsible for repopulating lost cells during injury. These cells have the capacity to differentiate into progenitor glial populations. During injury, a factor entitled Akhirin is secreted in the FP region. During spinal cord development, Akhirin is expressed solely on ependymal stem cells with latent stem cell properties and plays a key role in the development of the spinal cord. In the absence of Akhirin, stemness of these ependymal cells is not regulated. Injury compromises Akhirin expression and regulation and the cells of the FP region cannot properly be restored by the ependymal stem cell populations.
Stem cell controversy
The stem cell controversy is the consideration of the ethics of research involving the development, use, and destruction of human embryos. Most commonly, this controversy focuses on embryonic stem cells. Not all stem cell research involves human embryos. For example, adult stem cells, amniotic stem cells, and induced pluripotent stem cells do not involve creating, using, or destroying human embryos, and thus are minimally, if at all, controversial. Many less controversial sources of acquiring stem cells include using cells from the umbilical cord, breast milk, and bone marrow, which are not pluripotent.
Adult stem cell
Multipotent stem cells with a claimed equivalency to embryonic stem cells have been derived from spermatogonial progenitor cells found in the testicles of laboratory mice by scientists in Germany and the United States, and, a year later, researchers from Germany and the United Kingdom confirmed the same capability using cells from the testicles of humans. The extracted stem cells are known as human adult germline stem cells (GSCs)
Plant stem cell
Plant stem cells are innately undifferentiated cells located in the meristems of plants. Plant stem cells serve as the origin of plant vitality, as they maintain themselves while providing a steady supply of precursor cells to form differentiated tissues and organs in plants. Two distinct areas of stem cells are recognised: the apical meristem and the lateral meristem.
Plant stem cells are characterized by two distinctive properties, which are: the ability to create all differentiated cell types and the ability to self-renew such that the number of stem cells is maintained. Plant stem cells never undergo aging process but immortally give rise to new specialized and unspecialized cells, and they have the potential to grow into any organ, tissue, or cell in the body. Thus they are totipotent cells equipped with regenerative powers that facilitate plant growth and production of new organs throughout lifetime.
Hematopoietic stem cell
Stem and progenitor cells can be taken from the pelvis, at the iliac crest, using a needle and syringe. The cells can be removed as liquid (to perform a smear to look at the cell morphology) or they can be removed via a core biopsy (to maintain the architecture or relationship of the cells to each other and to the bone).
Stem-cell niche
In "Drosophila melanogaster", the GSC niche resides in the anterior-most region of each ovariole, known as the germarium. The GSC niche consists of necessary somatic cells-terminal filament cells, cap cells, escort cells, and other stem cells which function to maintain the GSCs. The GSC niche holds on average 2–3 GSCs, which are directly attached to somatic cap cells and Escort stem cells, which send maintenance signals directly to the GSCs. GSCs are easily identified through histological staining against vasa protein (to identify germ cells) and 1B1 protein (to outline cell structures and a germline specific fusome structure). Their physical attachment to the cap cells is necessary for their maintenance and activity. A GSC will divide asymmetrically to produce one daughter cystoblast, which then undergoes 4 rounds of incomplete mitosis as it progresses down the ovariole (through the process of oogenesis) eventually emerging as a mature egg chamber; the fusome found in the GSCs functions in cyst formation and may regulate asymmetrical cell divisions of the GSCs. Because of the abundant genetic tools available for use in "Drosophila melanogaster" and the ease of detecting GSCs through histological stainings, researchers have uncovered several molecular pathways controlling GSC maintenance and activity.
Stem-cell therapy
Fully mature human red blood cells may be generated "ex vivo" by hematopoietic stem cells (HSCs), which are precursors of red blood cells. In this process, HSCs are grown together with stromal cells, creating an environment that mimics the conditions of bone marrow, the natural site of red-blood-cell growth. Erythropoietin, a growth factor, is added, coaxing the stem cells to complete terminal differentiation into red blood cells. Further research into this technique should have potential benefits to gene therapy, blood transfusion, and topical medicine.
Endogenous regeneration
Neural stem cells (NSC) reside in the subventricular zone (SVZ) of the adult human brain and the dentate gyrus of the adult mammalian hippocampus. Newly formed neurons from these regions participate in learning, memory, olfaction and mood modulation. It has not been definitively determined whether or not these stem cells are multipotents. NSC from the hippocampus of rodents, which can differentiate into dentate granule cells, have developed into many cell types when studied in culture. However, another "in vivo" study, using NSCs in the postnatal SVZ, showed that the stem cell is restricted to developing into different neuronal sub-type cells in the olfactory bulb. It is believed that the various spatial location niches regulate the differentiation of the neural stem cell.
Testicle
The testes are covered by a tough membranous shell called the tunica albuginea. Within the testes are very fine coiled tubes called seminiferous tubules. The tubules are lined with a layer of cells (germ cells) that develop from puberty through old age into sperm cells (also known as spermatozoa or male gametes). The developing sperm travel through the seminiferous tubules to the rete testis located in the mediastinum testis, to the efferent ducts, and then to the epididymis where newly created sperm cells mature (see spermatogenesis). The sperm move into the vas deferens, and are eventually expelled through the urethra and out of the urethral orifice through muscular contractions.
Blood supply and lymphatic drainage of the testes and scrotum are distinct:
Adult stem cell
The therapeutic potential of adult stem cells is the focus of much scientific research, due to their ability to be harvested from the parent body that is females during the delivery. In common with embryonic stem cells, adult stem cells have the ability to differentiate into more than one cell type, but unlike the former they are often restricted to certain types or "lineages". The ability of a differentiated stem cell of one lineage to produce cells of a different lineage is called transdifferentiation. Some types of adult stem cells are more capable of transdifferentiation than others, but for many there is no evidence that such a transformation is possible. Consequently, adult stem therapies require a stem cell source of the specific lineage needed, and harvesting and/or culturing them up to the numbers required is a challenge. Additionally, cues from the immediate environment (including how stiff or porous the surrounding structure/extracellular matrix is) can alter or enhance the fate and differentiation of the stem cells.
Subventricular zone
The SVZ is a known site of neurogenesis and self-renewing neurons in the adult brain, serving as such due to the interacting cell types, extracellular molecules, and localized epigenetic regulation promoting such cellular proliferation. Along with the subgranular zone of the dentate gyrus, the subventricular zone serves as a source of neural stem cells (NSCs) in the process of adult neurogenesis. It harbors the largest population of proliferating cells in the adult brain of rodents, monkeys and humans. In 2010, it was shown that the balance between neural stem cells and neural progenitor cells (NPCs) is maintained by an interaction between the epidermal growth factor receptor signaling pathway and the Notch signaling pathway.
Stem-cell therapy
Stem cells can also be used to stimulate the growth of human tissues. In an adult, wounded tissue is most often replaced by scar tissue, which is characterized in the skin by disorganized collagen structure, loss of hair follicles and irregular vascular structure. In the case of wounded fetal tissue, however, wounded tissue is replaced with normal tissue through the activity of stem cells. A possible method for tissue regeneration in adults is to place adult stem cell "seeds" inside a tissue bed "soil" in a wound bed and allow the stem cells to stimulate differentiation in the tissue bed cells. This method elicits a regenerative response more similar to fetal wound-healing than adult scar tissue formation. Researchers are still investigating different aspects of the "soil" tissue that are conducive to regeneration.
Stem cell
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.
Neural stem cell
Epidermal growth factor (EGF) and fibroblast growth factor (FGF) are mitogens that promote neural progenitor and stem cell growth "in vitro", though other factors synthesized by the neural progenitor and stem cell populations are also required for optimal growth. It is hypothesized that neurogenesis in the adult brain originates from NSCs. The origin and identity of NSCs in the adult brain remain to be defined.
FAM71E1
The gene seems to be ubiquitously expressed at low levels throughout the body but has prominent expression in the adult human testis, followed by lower expression levels in the sperm, oocyte, and brain. Age does not have an effect on its expression in the skeletal muscle of males or females. Its expression is elevated prior to the differentiation of embryonic stem cells into pancreatic islet-like cells.
Fiona Watt
In Watt's lab, the researchers study the adult mammalian epidermis, the outermost layer of skin, which is maintained throughout life by the differentiation of stem cells into hair follicles, sebaceous glands, and interfollicular epidermis. Generally, these stem cells remain dormant and do not divide, but proliferation is initiated by damage. Professor Watt's lab and others have discovered many stem cells markers including high expression of 1 integrins, but their goal is to determine whether or not stem cell markers are hard-wired or expressed due to certain environmental cues depending on where the stem cells are located.
Nerve guidance conduit
Adult stem cells are not able to proliferate and differentiate as effectively "in vitro" as they are able to "in vivo". Adult stem cells can come from many different tissue locations, but it is difficult to isolate them because they are defined by behavior and not surface markers. A method has yet to be developed for clearly distinguishing between stem cells and the differentiated cells surrounding them. However, surface markers can still be used to a certain extent to remove most of the unwanted differentiated cells. Stem cell plasticity is the ability to differentiate across embryonic germ line boundaries. Though, the presence of plasticity has been hotly contested. Some claim that plasticity is caused by heterogeneity among the cells or cell fusion events. Currently, cells can be differentiated across cell lines with yields ranging from 10% to 90% depending on techniques used. More studies need to be done in order to standardize the yield with transdifferentiation. Transdifferentiation of multipotent stem cells is a potential means for obtaining stem cells that are not available or not easily obtained in the adult.
Stem cell
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) in serum media. A drug cocktail containing inhibitors to GSK3B and the MAPK/ERK pathway, called 2i, has also been shown to maintain pluripotency in stem cell culture. Human ESCs are grown on a feeder layer of mouse embryonic fibroblasts and require the presence of basic fibroblast growth factor (bFGF or FGF-2). Without optimal culture conditions or genetic manipulation, embryonic stem cells will rapidly differentiate.
Derek van der Kooy
His lab in the Terrence Donnelly Centre for Cellular and Biomolecular Research, carries out various neuroscience and developmental biology research projects. In 1994 his paper on neural stem cells in the adult mammalian forebrain was published in the journal "Neuron". This work first established that adult mammalian neural stem cells were located in the subependyma of the forebrain lateral ventricle, where two types of lineage related precursor cells, progenitor cells and stem cells, were shown to be present. Proliferation of these cell types were characterized in further experiments that were reported in articles in "Development" and the "Journal of Neuroscience". Of note, Derek's lab produced the first report of stem cells in the adult mammalian eye, published in 2000 in "Science". Further work, which was published in the journal, "Neuron", 2001, documented how embryonic stem cells were shown to differentiate directly to neural stem cells through a default mechanism. Derek's lab continues to investigate the nature of stem cells, embryonic and adult, the concept of immortal cells, and the differentiation of embryonic stem cells, capable of forming any tissue in the body, to neural stem cells.
Neuronal lineage marker
Neural stem cells are an example of somatic stem cell found in various tissues, both during development and in the adult. They have two fundamental characteristics: they are self-renewing and upon terminal division and differentiation, they can give rise to the full range of cells classes within the relevant tissue. Hence, a neural stem cell can give rise to another neural stem cell, or to any of the differentiated cell types found in the central and peripheral nervous systems (inhibitory and excitatory neurons, astrocytes and oligodendrocytes).
Somitomere
In the developing vertebrate embryo, the somitomeres (or somatomeres) are cells that are derived from the loose masses of paraxial mesoderm that are found alongside the developing neural tube. In human embryogenesis they appear towards the end of the third gestational week. The approximately 50 pairs of somitomeres in the human embryo, begin developing in the cranial (head) region, continuing in a caudal (tail) direction until the end of week four.
Embryonic stem cell
Embryonic stem cells of the inner cell mass are pluripotent, meaning they are able to differentiate to generate primitive ectoderm, which ultimately differentiates during gastrulation into all derivatives of the three primary germ layers: ectoderm, endoderm, and mesoderm. These include each of the more than 220 cell types in the adult human body. Pluripotency distinguishes embryonic stem cells from adult stem cells, which are multipotent and can only produce a limited number of cell types.
Adult stem cell
Neural stem cells are commonly cultured "in vitro" as so called neurospheres – floating heterogeneous aggregates of cells, containing a large proportion of stem cells. They can be propagated for extended periods of time and differentiated into both neuronal and glia cells, and therefore behave as stem cells. However, some recent studies suggest that this behaviour is induced by the culture conditions in progenitor cells, the progeny of stem cell division that normally undergo a strictly limited number of replication cycles "in vivo". Furthermore, neurosphere-derived cells do not behave as stem cells when transplanted back into the brain.
Hematopoietic stem cell niche
Many human blood cells, such as red blood cells (RBCs), immune cells, and even platelets all originate from the same progenitor cell, the hematopoietic stem cell (HSC). As these cells are short-lived, there needs to be a steady turnover of new blood cells and the maintenance of an HSC pool. This is broadly termed hematopoiesis. This event requires a special environment, termed the hematopoietic stem cell niche, which provides the protection and signals necessary to carry out the differentiation of cells from HSC progenitors. This niche relocates from the yolk sac to eventually rest in the bone marrow of mammals. Many pathological states can arise from disturbances in this niche environment, highlighting its importance in maintaining hematopoiesis.
Spermatogonial stem cell
Spermatogonia stem cells in mammals are found between the basal membrane of the seminiferous tubules and the Sertoli cells. They remain here until the meiotic prophase stage of meiosis. Here the spermatocytes pass through the basal membrane via the sertoli cell barrier.
Clinical uses of mesenchymal stem cells
Adult mesenchymal stem cells (MSCs) are being used by researchers in the fields of regenerative medicine and tissue engineering, to artificially reconstruct human tissue which has been previously damaged. Mesenchymal stem cells have the capacity to become any type of fully developed cell, which can contribute to replacing muscle tissues or internal organs.
To help discover the therapeutic uses of these stem cells they are grown in laboratories or by using medication to stimulate new cell growth within the human body. In MSC therapy the cells are extracted from the adult patient’s bone marrow via a procedure called bone marrow aspiration. This usually involves inserting a needle into the back of the patients hip bone and removing the sample from there. These cells are then grown under controlled "in vitro" conditions in a lab, so that they can multiply and same time mature( also referred to as differentiated. This process may take two to three weeks. The kind of mature, fully differentiated cell phenotype and the number of those cells created though this can be influenced in three ways. Firstly by varying the initial seed density in the culture medium, secondly through changing the conditions of the medium during expansion, and lastly through the addition of additives such as proteins or growth hormones to the culture medium. They are then harvested and put back into the patient through local delivery or systemic infusion.
Myosatellite cell
Myosatellite cells are located between the basement membrane and the sarcolemma of muscle fibers, and can lie in grooves either parallel or transversely to the longitudinal axis of the fibre. Their distribution across the fibre can vary significantly. Non-proliferative, quiescent myosatellite cells, which adjoin resting skeletal muscles, can be identified by their distinct location between sarcolemma and basal lamina, a high nuclear-to-cytoplasmic volume ratio, few organelles (e.g. ribosomes, endoplasmic reticulum, mitochondria, golgi complexes), small nuclear size, and a large quantity of nuclear heterochromatin relative to myonuclei. On the other hand, activated satellite cells have an increased number of caveolae, cytoplasmic organelles, and decreased levels of heterochromatin. Satellite cells are able to differentiate and fuse to augment existing muscle fibers and to form new fibers. These cells represent the oldest known adult stem cell niche, and are involved in the normal growth of muscle, as well as regeneration following injury or disease.
Gametogonium
Spermatogonium are the stem cell population that reside in the testes and undergo spermatogenesis to form sperm. They remain within the testes throughout adulthood.
Stem-cell niche
Adult stem cells remain in an undifferentiated state throughout adult life. However, when they are cultured "in vitro", they often undergo an 'aging' process in which their morphology is changed and their proliferative capacity is decreased. It is believed that correct culturing conditions of adult stem cells needs to be improved so that adult stem cells can maintain their stemness over time.
Adult stem cell
Scientific interest in adult stem cells is centered on their ability to divide or "self-renew" indefinitely, and generate all the cell types of the organ from which they originate, potentially regenerating the entire organ from a few cells. Unlike for embryonic stem cells, the use of human adult stem cells in research and therapy is not considered to be controversial, as they are derived from adult tissue samples rather than human embryos designated for scientific research. They have mainly been studied in humans and model organisms such as mice and rats.
Germ cell
A germ cell is any biological cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate in the primitive streak and migrate via the gut of an embryo to the developing gonads. There, they undergo meiosis, followed by cellular differentiation into mature gametes, either eggs or sperm. Unlike animals, plants do not have germ cells designated in early development. Instead, germ cells can arise from somatic cells in the adult (such as the floral meristem of flowering plants).