Adult stem cells are undifferentiated cells, found throughout the body after development, that multiply by

cell division Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukar ...

to replenish dying cells and regenerate damaged tissues. Also known as somatic stem cells (from Greek σωματικóς, meaning ''of the body''), they can be found in juvenile, adult animals, and humans, unlike embryonic stem cells. Scientific interest in adult stem cells is centered around two main characteristics. The first of which is their ability to divide or self-renew indefinitely, and the second their ability to 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 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. The main functions of adult stem cells are to replace cells that are at risk of possibly dying as a result of disease or injury and to maintain a state of

homeostasis In biology, homeostasis (British English, British also homoeostasis; ) is the state of steady internal physics, physical and chemistry, chemical conditions maintained by organism, living systems. This is the condition of optimal functioning fo ...

within the cell. There are three main methods to determine if the adult stem cell is capable of becoming a specialized cell. The adult stem cell can be labeled ''

in vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, an ...

'' and tracked, it can be isolated and then transplanted back into the organism, and it can be isolated ''in vivo'' and manipulated with growth hormones. They have mainly been studied in humans and

model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...

s, such as

mice A mouse (: mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

, rats and planarians.

Structure

Defining properties

stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell ...

possesses two properties: * ''Self-renewal'' is the ability to go through numerous cycles of

while still maintaining its undifferentiated state. Stem cells can replicate several times and can result in the formation of two stem cells, one stem cell more differentiated than the other, or two differentiated cells. * '' Multipotency'' or ''multidifferentiative potential'' is the ability to generate progeny of several distinct cell types, (for example

glial cell Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (the brain and the spinal cord) and in the peripheral nervous system that do not produce electrical impulses. The neuroglia make up ...

s and

neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

s) as opposed to unipotency, which is the term for cells that are restricted to producing a single cell type. However, some researchers do not consider multipotency to be essential and believe that unipotent self-renewing stem cells can exist. These properties can be illustrated with relative ease ''

in vitro ''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...

'', using methods such as clonogenic assays, where the progeny of a single cell is characterized. However, it is known that ''in vitro''

cell culture Cell culture or tissue culture is the process by which cell (biology), cells are grown under controlled conditions, generally outside of their natural environment. After cells of interest have been Cell isolation, isolated from living tissue, ...

conditions can alter the behavior of cells, proving that a particular subpopulation of cells possesses stem cell properties ''in vivo'' is challenging, and so considerable debate exists as to whether some proposed stem cell populations in the adult are indeed stem cells.

Properties

Cell division

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 stem cells, whereas asymmetric division produces one stem cell and one

progenitor cell A progenitor cell is a biological cell that can differentiate into a specific cell type. Stem cells and progenitor cells have this ability in common. However, stem cells are less specified than progenitor cells. Progenitor cells can only diffe ...

with limited self-renewal potential. Progenitors can go through several rounds of cell division before finally differentiating into a mature cell. It is believed that the molecular distinction between symmetric and asymmetric divisions lies in the differential segregation of cell membrane proteins (such as receptors) and their associated proteins between the daughter cells. Under normal conditions, tissue stem cells divide slowly and infrequently. They exhibit signs of quiescence or reversible growth arrest. The niche the stem cell is found in plays a large role in maintaining quiescence. Perturbed niches cause the stem cell to begin actively dividing again to replace lost or damaged cells until the niche is restored. In

hematopoietic stem cell Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within the ...

s, the

MAPK/ERK pathway The MAPK/ERK pathway (also known as the Ras-Raf-MEK-ERK pathway) is a chain of proteins in the cell (biology), cell that communicates a signal from a Receptor (biochemistry), receptor on the surface of the cell to the DNA in the nucleus of the cel ...

and PI3K/AKT/mTOR pathway regulate this transition. The ability to regulate the cell cycle in response to external cues helps prevent stem cell exhaustion or the gradual loss of stem cells following an altered balance between dormant and active states. Infrequent cell divisions also help reduce the risk of acquiring DNA mutations that would be passed on to daughter cells.

Plasticity

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 The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical ...

, and

endoderm Endoderm is the innermost of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). Cells migrating inward along the archenteron form the inner layer of the gastr ...

. 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 by 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" (BLSCs) and "very small embryonic-like" (VSEL) stem cells, and display pluripotency ''in vitro''. As BLSCs and VSEL cells are present in virtually all adult tissues, including the lungs, brain, kidneys, muscles, and pancreas, co-purification of BLSCs 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.

Aging

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 an 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.) 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 prospects to slow down human aging substantially. Such cells are one of the various classes of induced stem cells.

Function

Signaling pathways

Adult stem cell research has been focused on uncovering the general molecular mechanisms that control their self-renewal and differentiation. * Notch :The Notch pathway has been known to developmental biologists for decades. Its role in the control of stem cell proliferation has now been demonstrated for several cell types including

hematopoietic Haematopoiesis (; ; also hematopoiesis in American English, sometimes h(a)emopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. In a healthy adult human, roughly ten ...

, neural, and mammary stem cells. * Wnt :These developmental pathways are also strongly implicated as stem cell regulators. * TGFβ :The TGFβ family of

cytokine Cytokines () are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are produced by a broad range of cells, including immune cells like macrophages, B cell, B lymphocytes, T cell, T lymphocytes ...

s regulate the stemness of both normal and cancer stem cells.

Types

Hematopoietic stem cells

Hematopoietic stem cells (HSCs) are stem cells that can differentiate into all blood cells. This process is called hematopoiesis. Hematopoietic stem cells are found in the

bone marrow Bone marrow is a semi-solid biological tissue, tissue found within the Spongy bone, spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It i ...

and umbilical cord blood. The HSCs are generally dormant when found in adults due to their nature.

Mammary stem cells

Mammary stem cells provide the source of cells for the growth of the

mammary gland A mammary gland is an exocrine gland that produces milk in humans and other mammals. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organs such as the breasts in primates (for example, human ...

during puberty and

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregn ...

and play an important role in the

carcinogenesis Carcinogenesis, also called oncogenesis or tumorigenesis, is the formation of a cancer, whereby normal cell (biology), cells are malignant transformation, transformed into cancer cells. The process is characterized by changes at the cellular, G ...

of the breast. Mammary stem cells have been isolated from human and mouse tissue as well as from cell lines derived from the mammary gland. Single such cells can give rise to both the luminal and

myoepithelial cell Myoepithelial cells (sometimes referred to as myoepithelium) are cells usually found in glandular epithelium as a thin layer above the basement membrane but generally beneath the lumen (anatomy), luminal cells. These may be positive for ACTA2, alph ...

types of the gland and have been shown to have the ability to regenerate the entire organ in mice.

Intestinal stem cells

Intestinal stem cells divide continuously throughout life and use a complex genetic program to produce the cells lining the surface of the small and large intestines. Intestinal stem cells reside near the base of the stem cell niche, called the crypts of Lieberkuhn. Intestinal stem cells are probably the source of most cancers of the small intestine and colon.

Mesenchymal stem cells

Mesenchymal stem cells (MSCs) are of stromal origin and may differentiate into a variety of tissues. MSCs have been isolated from the

placenta The placenta (: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas, and waste exchange between ...

adipose tissue Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, Blood vessel, vascular endothel ...

lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...

and blood, Wharton's jelly from the

umbilical cord In Placentalia, placental mammals, the umbilical cord (also called the navel string, birth cord or ''funiculus umbilicalis'') is a conduit between the developing embryo or fetus and the placenta. During prenatal development, the umbilical cord i ...

, and teeth (perivascular niche of dental pulp and periodontal ligament). MSCs are attractive for clinical therapy due to their ability to differentiate, provide trophic support, and modulate innate immune response. These cells differentiate into various cell types such as

osteoblast Osteoblasts (from the Greek combining forms for " bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cells with a single nucleus that synthesize bone. However, in the process of bone formation, osteoblasts fu ...

s, chondroblasts,

adipocyte Adipocytes, also known as lipocytes and fat cells, are the cell (biology), cells that primarily compose adipose tissue, specialized in storing energy as fat. Adipocytes are derived from mesenchymal stem cells which give rise to adipocytes through ...

neuroectoderm Neuroectoderm (or neural ectoderm or neural tube epithelium) consists of cells derived from the ectoderm. Formation of the neuroectoderm is the first step in the development of the nervous system. The neuroectoderm receives bone morphogenetic pro ...

al cells, and

hepatocyte A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass. These cells are involved in: * Protein synthesis * Protein storage * Transformation of carbohydrates * Synthesis of cholesterol, bi ...

s. Bioactive mediators that favor local cell growth are also secreted by MSCs. Anti-inflammatory effects on the local microenvironment, which promote tissue healing, are also observed. The inflammatory response can be modulated by adipose-derived regenerative cells (ADRC) including mesenchymal stem cells and regulatory T-lymphocytes. The mesenchymal stem cells thus alter the outcome of the immune response by changing the cytokine secretion of dendritic and T-cell subsets. This results in a shift from a pro-inflammatory environment to an anti-inflammatory or tolerant cell environment.

Endothelial stem cells

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 vessel Blood vessels are the tubular structures of a circulatory system that transport blood throughout many Animal, animals’ bodies. Blood vessels transport blood cells, nutrients, and oxygen to most of the Tissue (biology), tissues of a Body (bi ...

s as well as

lymphatic vessel The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessel ...

s. Endothelial stem cells are an important aspect of the vascular network, even influencing the motion relating to white blood cells.

Neural stem cells

The existence of stem cells in the adult brain has been postulated following the discovery that the process of

neurogenesis Neurogenesis is the process by which nervous system cells, the neurons, are produced by neural stem cells (NSCs). This occurs in all species of animals except the porifera (sponges) and placozoans. Types of NSCs include neuroepithelial cells ( ...

, the birth of new

s, continues into adulthood in rats. The presence of stem cells in the mature primate brain was first reported in 1967. It has since been shown that new neurons are generated in adult mice, songbirds, and primates, including humans. Normally, adult neurogenesis is restricted to two areas of the brain – the subventricular zone, which lines the lateral ventricles, and the dentate gyrus of the hippocampal formation. Although the generation of new neurons in the

hippocampus The hippocampus (: hippocampi; via Latin from Ancient Greek, Greek , 'seahorse'), also hippocampus proper, is a major component of the brain of humans and many other vertebrates. In the human brain the hippocampus, the dentate gyrus, and the ...

is well established, the presence of true self-renewing stem cells there has been debated. Under certain circumstances, such as following tissue damage in

ischemia Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems ...

, neurogenesis can be induced in other brain regions, including the

neocortex The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, ...

. 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 and differentiated into both

al and

glial Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cell (biology), cells in the central nervous system (the brain and the spinal cord) and in the peripheral nervous system that do not produce Action potential, electrical ...

cells, and therefore behave as stem cells. However, some recent studies suggest that this behavior is induced by the culture conditions in

s, 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. Neural stem cells share many properties with

s (HSCs). Remarkably, when injected into the blood, neurosphere-derived cells differentiate into various cell types of the

immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...

Olfactory adult stem cells

Olfactory adult stem cells have been successfully harvested from the human

olfactory mucosa The olfactory mucosa is the Neuroepithelial cell, neuroepithelial mucosa lining the roof and upper parts of the Nasal septum, septum and lateral wall of the nasal cavity which contains Bipolar neuron, bipolar neurons of the primary receptor neur ...

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.

Neural crest stem cells

Hair follicle The hair follicle is an organ found in mammalian skin. It resides in the dermal layer of the skin and is made up of 20 different cell types, each with distinct functions. The hair follicle regulates hair growth via a complex interaction betwee ...

s contain two types of stem cells, one of which appears to represent a remnant of the stem cells of the embryonic

neural crest The neural crest is a ridge-like structure that is formed transiently between the epidermal ectoderm and neural plate during vertebrate development. Neural crest cells originate from this structure through the epithelial-mesenchymal transition, ...

. Similar cells have been found in the

gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the Digestion, digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascula ...

sciatic nerve The sciatic nerve, also called the ischiadic nerve, is a large nerve in humans and other vertebrate animals. It is the largest branch of the sacral plexus and runs alongside the hip joint and down the right lower limb. It is the longest and widest ...

, cardiac outflow tract and spinal and sympathetic ganglia. These cells can generate

Schwann cell Schwann cells or neurolemmocytes (named after German physiologist Theodor Schwann) are the principal glia of the peripheral nervous system (PNS). Glial cells function to support neurons and in the PNS, also include Satellite glial cell, satellite ...

s, myofibroblasts, chondrocytes, and

melanocyte Melanocytes are melanin-producing neural-crest, neural crest-derived cell (biology), cells located in the bottom layer (the stratum basale) of the skin's epidermis (skin), epidermis, the middle layer of the eye (the uvea), the inner ear, vagina ...

Testicular cells

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) Multipotent stem cells have also been derived from

germ cell A germ cell is any 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 unde ...

s found in human testicles.

Clinical significance

Adult stem cell treatments have been used for many years to successfully treat

leukemia Leukemia ( also spelled leukaemia; pronounced ) is a group of blood cancers that usually begin in the bone marrow and produce high numbers of abnormal blood cells. These blood cells are not fully developed and are called ''blasts'' or '' ...

and related bone/blood cancers utilizing bone marrow transplants. The use of adult stem cells in research and therapy is not considered as controversial as the use of embryonic stem cells, because the production of adult stem cells does not require the destruction of an

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

. Early regenerative applications of adult stem cells have focused on intravenous delivery of blood progenitors known as Hematopoietic Stem Cells (HSCs). CD34+

Stem Cells have been clinically applied to treat various diseases including spinal cord injury, liver cirrhosis and Peripheral Vascular disease. Research has shown that CD34+

Stem Cells are relatively more numerous in men than in women of reproductive age group among spinal cord Injury victims. Other early commercial applications have focused on Mesenchymal Stem Cells (MSCs). For both cell lines, direct injection or placement of cells into a site in need of repair may be the preferred method of treatment, as vascular delivery suffers from a "pulmonary first pass effect" where intravenously injected cells are sequestered in the lungs. Clinical case reports in orthopedic applications have been published. Wakitani has published a small case series of nine defects in five knees involving surgical transplantation of mesenchymal stem cells with coverage of the treated chondral defects. Centeno et al. have reported high-field MRI evidence of increased cartilage and meniscus volume in individual human clinical subjects as well as a large n=227 safety study. Many other stem cell-based treatments are operating outside the US, with much controversy being reported regarding these treatments as some feel more regulation is needed as clinics tend to exaggerate claims of success and minimize or omit risks.

Therapies

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 can 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 In biology, the extracellular matrix (ECM), also called intercellular matrix (ICM), is a network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide structural and bio ...

is) can alter or enhance the fate and differentiation of the stem cells.

Sources

Pluripotent stem cells, i.e. cells that can give rise to any fetal or adult cell type, can be found in several tissues, including umbilical cord blood. Using genetic reprogramming, pluripotent stem cells equivalent to embryonic stem cells have been derived from human adult skin tissue. Other adult stem cells are

multipotent Cell potency is a cell's ability to differentiate into other cell types. The more cell types a cell can differentiate into, the greater its potency. Potency is also described as the gene activation potential within a cell, which like a continuum ...

, meaning there are several limited types of cell they can become, and are generally referred to by their tissue origin (such as

mesenchymal stem cell Mesenchymal stem cells (MSCs), also known as mesenchymal stromal cells or medicinal signaling cells, are multipotent stromal cells that can Cellular differentiation, differentiate into a variety of cell types, including osteoblasts (bone cells), ...

, adipose-derived stem cell, endothelial stem cell, etc.). A great deal of adult stem cell research has focused on investigating their capacity to divide or self-renew indefinitely, and their differentiation potential. In mice, pluripotent stem cells can be directly generated from adult

fibroblast A fibroblast is a type of cell (biology), biological cell typically with a spindle shape that synthesizes the extracellular matrix and collagen, produces the structural framework (Stroma (tissue), stroma) for animal Tissue (biology), tissues, and ...

cultures.

Research

Cancer

In recent years, acceptance of the concept of adult stem cells has increased. There is now a hypothesis that stem cells reside in many adult tissues and that these unique reservoirs of cells not only are responsible for the normal reparative and regenerative processes but are also considered to be a prime target for genetic and epigenetic changes, culminating in many abnormal conditions including cancer. (See cancer stem cell for more details.)

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. Many pharmaceuticals are exported by these transporters conferring

multidrug resistance Multiple drug resistance (MDR), multidrug resistance or multiresistance is antimicrobial resistance shown by a species of microorganism to at least one antimicrobial drug in three or more antimicrobial categories. Antimicrobial categories are ...

onto the cell. This complicates the design of drugs, for instance, neural stem cell-targeted therapies for the treatment of clinical depression.

Lung Organoid Model: Lung Disease in COVID-19

The virus that causes COVID-19,

SARS-CoV-2 Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) is a strain of coronavirus that causes COVID-19, the respiratory illness responsible for the COVID-19 pandemic. The virus previously had the Novel coronavirus, provisional nam ...

, damages the lungs extensively in the presence of an overreactive immune response. Adult stem cells were extracted from deep lung biopsies and used to construct a complete lung model with both proximal and distal airway epithelia. After being developed in 3D cultures, the organoids were separated into individual cells to form 2D monolayers. These lung models were used to study the damage SARS-CoV-2 causes when applied to the apical side of the transwell.

Stroke Treatment

Due to their multipotency, capacity to release growth factors, and immunomodulatory abilities, stem cell-based therapies have become a viable tool for the treatment of both acute and delayed phases of stroke. By inducing

angiogenesis Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature mainly by processes of sprouting and ...

, and synaptogenesis as well as activating

endogenous Endogeny, in biology, refers to the property of originating or developing from within an organism, tissue, or cell. For example, ''endogenous substances'', and ''endogenous processes'' are those that originate within a living system (e.g. an ...

restorative processes through the generation of

s and trophic factors, this transdifferentiation can form cells with a neural lineage.

References

External links

NIH Stem Cell Information Resource
a resource for stem cell research
Nature Reports Stem Cells
Background information, research advances, and debates about stem cell science
UMDNJ Stem Cell and Regenerative Medicine
provides educational materials and research resources
Stem Cell Research at Johns Hopkins University
{{DEFAULTSORT:Adult Stem Cell Stem cells Biotechnology