Stem cell division and differentiation. A - stem cells are red; B - progenitor cell; C - differentiated cell; 1 - symmetric stem cell division; 2 - asymmetric stem cell division; 3 - progenitor division; 4 - terminal differentiation

Adult stem cells are undifferentiated cells found throughout the body that divide to replenish dying cells and regenerate damaged tissues. Also known as somatic (from Greek Σωματικóς, of the body) stem cells, they can be found in children, as well as adults. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Cellular differentiation is a concept from developmental biology describing the process by which cells acquire a type. The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptions. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... Biological tissue is a collection of interconnected cells that perform a similar function within an organism. ... The term somatic refers to the body, as distinct from some other entity, such as the mind. ... Mouse embryonic stem cells. ...

Research into adult stem cells has been fueled by their abilities 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 embryonic stem cells, the use of adult stem cells in research and therapy is not controversial because the production of adult stem cells does not require the destruction of an embryo. Adult stem cells can be isolated from a tissue sample obtained from an adult. They have mainly been studied in humans and model organisms such as mice and rats. A cell type is a distinct morphological or functional form of cell. ... Åž:For other uses, see Organ (disambiguation) In biology, an organ (Latin: organum, instrument, tool) is a group of tissues that perform a specific function or group of functions. ... Mouse embryonic stem cells. ... There is widespread controversy over stem cell research fue to techniques used in the creation and usage of embryonic stem cells. ... For other uses, see Embryo (disambiguation). ... This article is about modern humans. ... A model organism is a species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. ... This article is about the animal. ... Species 50 species; see text *Several subfamilies of Muroids include animals called rats. ...

Adult stem cell treatments

Main article: Stem cell treatments

Adult stem cells are being developed for use in treatments for a variety of human conditions, ranging from blindness to spinal cord injury (Check The Score). Since adult stem cells can be harvested from the patient, potential ethical issues and immunogenic rejection are averted. Medical researchers believe that stem cell treatments have the potential to change the face of human disease and alleviate suffering. ... This article is about the visual condition. ... Spinal cord injury, or myelopathy, is a disturbance of the spinal cord that results in loss of sensation and/or mobility. ... Transplant rejection occurs when the immune system of the recipient of a transplant attacks the transplanted organ or tissue. ...

Adult stem cells, like embryonic stem cells, have pluripotent potential and can differentiate into cells derived from all three germ layers. Research has demonstrated that pluripotent stem cells can be directly generated from adult fibroblast cultures.^[1]

Adult stem cells are available in high quantities in cord blood, which can be collected at birth and are not difficult to isolate and purify. Other adult stem cell types can be multiplied in-vitro to therapeutic numbers, if needed. Umbilical cord blood is human blood from the placenta and umbilical cord that is rich in hematopoietic stem cells. ...

While embryonic stem cell potential remains theoretical, adult stem cell treatments are already being used to successfully treat many diseases. The use of adult stem cells in research and therapy is not as controversial as embryonic stem cells, because the production of adult stem cells does not require the destruction of an embryo. Adult stem cells also pose no medical dangers to the patient. Among the most stunning advancements in adult stem cell therapy are treatments for Parkinson's disease, juvenile diabetes, and spinal cord injuries. A list of current treatments can be found at Stem Cell Research There is widespread controversy over stem cell research fue to techniques used in the creation and usage of embryonic stem cells. ... Mouse embryonic stem cells. ... For other uses, see Embryo (disambiguation). ...

Adult Stem Cell and Cancer

In recent years the concept of adult stem cell has transformed to include the theory that stem cells reside in many adult tissues and that these unique reservoir of adult stem cells are not only responsible for the normal reparative and regenerative processes but are also considered to be a prime target for genetic and epigenetic changes culminating to many abnormal conditions including cancer [1][2]. .

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Properties

Defining properties

The rigorous definition of a stem cell requires that it possesses two properties: Mouse embryonic stem cells with fluorescent marker. ...

• Self-renewal - the ability to go through numerous cycles of cell division while maintaining the undifferentiated state.
• Multipotency or multidifferentiative potential - the ability to generate progeny of several distinct cell types, for example both glial cells and neurons, opposed to unipotency - restriction to a single-cell type. Some researchers do not consider this property essential and believe that unipotent self-renewing stem cells can exist.

These properties can be illustrated with relative ease in vitro, using methods such as clonogenic assays, where the progeny of single cell is characterized. However, in vitro cell culture conditions can alter the behavior of cells. Proving that a particular subpopulation of cells possesses stem cell properties in vivo is challenging. Considerable debate exists whether some proposed cell populations in the adult are indeed stem cells. The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication. ... This does not adequately cite its references or sources. ... A cell type is a distinct morphological or functional form of cell. ... Neuroglia of the brain shown by Golgis method. ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Unipotent cell, in cell biology, is used to describe a cell (e. ... In mathematics, a unipotent element r of a ring R is one such that r âˆ’ 1 is a nilpotent element, in other words such that some power (r âˆ’ 1)n is zero. ... Wiktionary has a definition of: In vitro In vitro (Latin: within glass) means within a test tube, or, more generally, outside a living organism or cell. ... Clonogenic assay is a microbiology technique for studying the effectiveness of specific agents on the proliferation of cells. ... Epithelial cells in culture, stained for keratin (red) and DNA (green) Cell culture is the process by which either prokaryotic or eukaryotic cells are grown under controlled conditions. ... In vivo (Latin for (with)in the living). ...

Lineage

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. Progentiors can go through several rounds of cell division before terminally differentiating into a mature cell. It is believed that the molecular distinction between symmetric and asymmetric divisions lies in differential segregation of cell membrane proteins (such as receptors) between the daughter cells. The term progenitor cell is used in cell biology and developmental biology to refer to immature or undifferentiated cells, typically found in post-natal animals. ... Cellular differentiation is a concept from developmental biology describing the process by which cells acquire a type. The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptions. ... In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to a specific molecule (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates the cellular response to the ligand. ...

Multidrug resistance

Adult stem cells express transporters of the ATP-binding cassette family that actively pump a diversity of organic molecules out of the cell.^[2] 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. ABC-Transporter Genes (or ABC Transporters) encode membrane proteins that function in the transport of a wide variety of substrates across extra- and intracellular membranes, including metabolic products, lipids and sterols, and drugs. ... Sodium-Potassium pump, an example of Primary active transport secondary active transport Active transport (sometimes called active uptake) is the mediated transport of biochemicals, and other atomic/molecular substances, across membranes. ... Multidrug resistance is the ability of pathologic cells to withstand chemicals that are designed to aid in the eradication of such cells. ... Stem cell division and differentiation. ... Clinical depression (also called major depressive disorder, or unipolar depression when compared to bipolar disorder) is a state of intense sadness, melancholia or despair that has advanced to the point of being disruptive to an individuals social functioning and/or activities of daily living. ...

Signaling pathways

Adult stem cell research has been focused on uncovering the general molecular mechanisms that control their self-renewal and differentiation.

• Bmi-1

The transcriptional repressor Bmi-1 is one of the Polycomb-group proteins that was discovered as a common oncogene activated in lymphoma^[3] and later shown to specifically regulate HSCs^[4]. The role of Bmi-1 has also been illustrated in neural stem cells.^[5]

• Notch

The Notch pathway has been known to developmental biologists for decades. Its role in control of stem cell proliferation has now been demonstrated for several cell types including haematopoietic, neural and mammary^[6] stem cells.

• Sonic hedgehog and Wnt

These developmental pathways are also strongly implicated as stem cell regulators.^[7]

A micrograph of ongoing gene transcription of ribosomal RNA illustrating the growing primary transcripts. ... A repressor is a DNA-binding protein that regulates the expression of one or more genes by decreasing the rate of transcription. ... Polycomb-group proteins are a family of proteins first discovered in fruit flies that can remodel chromatin such that transcription factors cannot bind to promoter sequences in DNA. // In Drosophila, the Trithorax-group (trxG) and Polycomb-group (PcG) proteins act antagonistically and interact with chromosomal elements, termed Cellular Memory Modules... An oncogene is a modified gene that increases the malignancy of a tumor cell. ... Lymphoma is a general term for cancers that develop in the lymphatic system. ... The Notch pathway is a gene regulatory pathway involved in multiple differentiation processes. ... The Notch pathway is a gene regulatory pathway involved in multiple differentiation processes. ... Sonic hedgehog homolog (SHH) is one of three proteins in the mammalian hedgehog family, the others being desert hedgehog (DHH) and Indian hedgehog (IHH). ... The wnt signalling pathway is a network of proteins that has been implicated in embryogenesis and cancer. ...

Plasticity

Under special conditions tissue-specific adult stem cells can generate a whole spectrum of cell types of other tissues, even crossing germ layers.^[8] 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. A cell type is a distinct morphological or functional form of cell. ... Organs derived from each germ layer. ... Transdifferentation in biology takes place when a non-stem cell transforms into a different type of cell, or when an already differentiated stem cell creates cells outside its already established differentiation. ... An Agar Plate -- an example of a bacterial growth medium. ... Epithelial cells in culture, stained for keratin (red) and DNA (green) Cell culture is the process by which either prokaryotic or eukaryotic cells are grown under controlled conditions. ...

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Types

Adipose derived adult stem cells

Adipose-derived stem cells (ASCs) have also been isolated from human fat, usually by method of liposuction. This cell population seems to be similar in many ways to mesenchymal stem cells (MSCs) derived from bone marrow. However, it is possible to isolate many more cells from adipose tissue and the harvest procedure itself is less painful than the harvest of bone marrow. Human ASCs have been shown to differentiate in the lab into bone, cartilage, fat, muscle, and might be able to differentiate into neurons, making them a possible source for future applications in the clinic.^[9][10] In support of this, current studies in animals suggest that ASCs might be able to repair significant bony defects and ASCs have been recently used to successfully repair a large cranial defect in a human patient [3]. It has been suggested that Subcutaneous fat be merged into this article or section. ... Liposuction, also known as lipoplasty (fat modeling), liposculpture or suction lipectomy (suction-assisted fat removal) is a cosmetic surgery operation that removes fat from many different sites on the human body. ... Mesenchymal cells also known as mesenchymal stem cells or marrow stromal cells (MSC) are stem cells that can differentiate into osteoblasts, chondrocytes, myocytes, adipocytes neuronal cells and - as decribed lately, into beta-pancreatic islets cells. ... This article is about the skeletal organs. ... Cartilage is a type of dense connective tissue. ... A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ... For other uses, see Brain (disambiguation). ...

Haematopoietic stem cells

Main article: Pluripotential hemopoietic stem cell

Note that some complexity is omitted from the diagram. ...

Mammary stem cells

Mammary stem cells provide the source of cells for growth of the mammary gland during puberty and gestation and play an important role in carcinogenesis of the breast.^[11] Mammary stem cells have been isolated from human and mouse tissue as well as from cell lines derived from the mammary gland. A single such cell can give rise to both luminal and myoepithelial cell types of the gland and has been shown to regenerate the entire organ in mice.^[12] Mammary glands are the organs that, in the female mammal, produce milk for the sustenance of the young. ... Gestation is the carrying of an embryo or fetus inside a female viviparous animal. ... Cancers are caused by a series of mutations. ... Epithelial cells in culture, stained for keratin (red) and DNA (green) Cell culture is the process by which either prokaryotic or eukaryotic cells are grown under controlled conditions. ... A myoepithelial cell (myoepithelium) is a type of epithelium which has some characteristics of muscle tissue. ...

Mesenchymal stem cells

Main article: Mesenchymal stem cell

Mesenchymal stem cells or marrow stromal cells (MSC), are stem cells that can differentiate into osteoblasts, chondrocytes, myocytes, adipocytes, neuronal cells, and, as described lately, into beta-pancreatic islets cells. ...

Neural stem cells

The existence of stem cells in the adult brain has been postulated following the discovery that the process of neurogenesis, birth of new neurons, continues into adulthood in rats.^[13] It has since been shown that new neurons are generated in adult mice, songbirds and primates, including humans. Normally adult neurogenesis is restricted to the subventricular zone, which lines the lateral ventricles of the brain, and the dentate gyrus of the hippocampal formation.^[14] Although the generation of new neurons in the hippocampus is well established, the presence of true self-renewing stem cells there has been debated.^[15] Under certain circumstances, such as following tissue damage in ischemia, neurogenesis can be induced in other brain regions, including the neocortex. Neurogenesis (birth of neurons) is the process by which neurons are created. ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Subventricular zone (abbreviated form: SVZ) is a paired brain structure situated throughout the lateral walls of the lateral ventricles. ... The ventricular system is a fluid conducting system within the brain. ... The dentate gyrus is part of the hippocampal formation. ... The location of the hippocampus in the human brain. ... The hippocampus is structurally located inside the medial temporal lobe of the brain. ... In medicine, ischemia (Greek ισχαιμία, isch- is restriction, hema or haema is blood) is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. ... The neocortex (Latin for new bark or new rind) is a part of the brain of mammals. ...

Neural stem cells are commonly cultured in vitro as so called neurospheres - floating heterogeneous aggregates of cells, containing a large proportion of stem cells.^[16] 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.^[17] Furthermore, neurosphere-derived cells do not behave as stem cells when transplanted back into the brain.^[18] There are very few or no other articles that link to this one. ... Look up Heterogeneous in Wiktionary, the free dictionary. ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Neuroglia cells of the brain shown by Golgis method. ... The term progenitor cell is used in cell biology and developmental biology to refer to immature or undifferentiated cells, typically found in post-natal animals. ...

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.^[19] Cells that resemble neural stem cells have been found in the bone marrow, the home of HSCs.^[20] It has been suggested that new neurons in the dentate gyrus arise from circulating HCSs. Indeed, newborn cells first appear in the dentate in the heavily vascularised subgranular zone immediately adjacent to blood vessels. Mouse embryonic stem cells. ... A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ... Subgranular zone (SGZ) is a brain region in the dentate gyrus where adult neurogenesis occurs. ...

Olfactory adult stem cells

Olfactory adult stem cells have been successfully harvested from the human olfactory mucosa cells, the lining of the nose involved in the sense of smell.^[21] For other uses, see Nose (disambiguation). ...

Adult stem cells isolated from the olfactory mucosa (cells lining the inside of the nose involved in the sense of smell) have the ability to develop into many different cell types if they are given the right chemical environment.

These adult olfactory stem cells appear to have the same ability as embryonic stem cells in giving rise to many different cell types but have the advantage that they can be obtained from all individuals, even older people who might be most in need of stem cell therapies.

Olfactory stem cells hold potential for therapeutic applications. Thanks to their location they can be harvested with ease without harm to the patient in contrast to neural stem cells.

Open questions in adult stem cell research

• What is the origin of adult stem cells? They are derived with no medical risk to the donor from blood, umbillical cord blood, bone marrow, placentas, liver, epidermis, retina, skeletal muscle, intestine, brain, dental pulp, and fat obtained from liposuction. They can also be derived from amnionic fluid, non-living fetal tissue and can be extracted from brains of cadavers.
• Are stem cells found in different tissues fundamentally distinct, or is there a universal adult stem cell? Stem cells derived from different adult tissue can have remarkably similar properties. Research on adult stem cells has revealed that they can be induced to produce cell types of a variety of tissues. Do some or all adult stem cells belong to a single lineage but behave differently depending on extracellular cues?
• Which adult tissues harbor stem cells? Do tissues that apparently contain no stem cells rely on other sources of new cells, or is it a matter of time until stem cells are identified there?
• What molecular factors enable stem cell plasticity? While a lot is known about the cellular qualities that accompany multi- and pluripotency, the molecular/genetic factors that determine these qualities remain unclear. Could knowledge of these mechanisms allow us to reverse the process of differentiation and restore embryonic stem cell properties in adult stem cells or even differentiated cells?

In cell biology, molecular biology and related fields, the word extracellular means outside the cell. It is used in contrast to intracellular (inside the cell). ... Multipotent progenitor cells can give rise to several other cell types, but those types are limited in number. ... Pluripotency in the broad sense refers to having more than one potential outcome. In biological systems, this can refer either to cells or to biological compounds. ... Cellular differentiation is a concept from developmental biology describing the process by which cells acquire a type. The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptions. ... Human embryonic stem cell colony. ...

News and External links

• NIH Stem Cell Information Resource, resource for stem cell research
• Stem Cells, the international journal for cell differentiation and proliferation
• Stem Cell and Cord Blood information database
• Check The Score, Successes of Adult Stem Cells vs. Embryonic Stem Cells
• whaaz a science wiki site for updates on stem cells and other related topics
• Cells Limited providing Adult Stem Cells Storage
• Regenecell Adult stem cell treatments worldwide

Academic

• Tulane University Centre for Gene Therapy, prepares and distributes marrow stromal cells for academic research
• UMDNJ Stem Cell and Regnerative Medicine, provides educational materials and research resources

References