Adult stem cells are undifferentiated cells, found throughout the body after development, that multiply by cell division to replenish dying cells and regenerate damaged tissues. More accurately known as somatic stem cells (from Greek , meaning of the body), because they are usually more plentiful in juvenile (child) than in adult animal and human bodies.
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 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.
A stem cell possesses two properties:
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, whereas asymmetric division produces only one stem cell and a progenitor cell 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 differential segregation of cell membrane proteins (such as receptors) between the daughter cells.
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.
Adult stem cell research has been focused on uncovering the general molecular mechanisms that control their self-renewal and differentiation.
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" (Am Surg. 2007 Nov;73:1106-10) 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.
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.)
Hematopoietic stem cells are found in the bone marrow and umbilical cord blood and give rise to all the blood cell types.
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. 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 types of the gland, and have been shown to have the ability to regenerate the entire organ in mice.
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 (MSCs) are of stromal origin and may differentiate into a variety of tissues. MSCs have been isolated from placenta, adipose tissue, lung, bone marrow and blood, Wharton's jelly from the umbilical cord, 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 have the ability to differentiate into various cell types such as osteoblasts, chondroblasts, adypocytes, neuroectodermal cells, and hepatocytes. 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 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.
The existence of stem cells in the adult brain has been postulated following the discovery that the process of neurogenesis, the birth of new neurons, 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 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, neurogenesis can be induced in other brain regions, including the neocortex.
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.
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.
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.
Hair follicles contain two types of stem cells, one of which appears to represent a remnant of the stem cells of the embryonic neural crest. Similar cells have been found in the gastrointestinal tract, sciatic nerve, cardiac outflow tract and spinal and sympathetic ganglia. These cells can generate neurons, Schwann cells, myofibroblast, chondrocytes and melanocytes.
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 cells found in human testicles.
The therapeutic potential of adult stem cells is the focus of much scientific research, due to their ability to be harvested from the patient. 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.
Pluripotent stem cells, i.e. cells that can give rise to any fetal or adult cell type, can be found in a number of 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, meaning they are restricted in the types of cell they can become, and are generally referred to by their tissue origin (such as mesenchymal stem cell, 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 potential for differentiation. In mice, pluripotent stem cells can be directly generated from adult fibroblast cultures.
Adult stem cell treatments have been used for many years to successfully treat leukemia 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.
Early regenerative applications of adult stem cells has focused on intravenous delivery of blood progenitors known as Hematopetic Stem Cells (HSC's). CD34+ hematopoietic 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+ hematopoietic 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 intravenous 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.
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.)
Adult stem cell - Wikipedia
- Global Tooth Regeneration Market : Industry Analysis and Forecast (2020-2027)-by Type, Application, Population Demographics and Region. - Morning Tick - July 6th, 2020
- REGENERATIVE MEDICINE MARKET ALONG WITH COVID-19 IMPACT ANALYSIS AND CLINICAL OUTLOOK 2022 | STRYKER CORPORATION, ZIMMER BIOMET HOLDINGS INC.,... - July 2nd, 2020
- Outlook on the Worldwide Regenerative Medicine Industry to 2024 - Rising Global Healthcare Expenditure Presents Opportunities - GlobeNewswire - June 25th, 2020
- Estrogen induces dynamic ER and RING1B recruitment to control gene and enhancer activities in luminal breast cancer - Science Advances - June 8th, 2020
- Participation of Somatic Stem Cells, Labeled by a Unique ... - June 5th, 2020
- COVID-19 Impact on Global Cell Therapy Industry 2020: Market Trends, Size, Share, Applications, SWOT Analysis by Top Key Players and Forecast Report... - June 5th, 2020
- A caveolin binding motif in Na/K-ATPase is required for stem cell differentiation and organogenesis in mammals and C. elegans - Science Advances - June 1st, 2020
- Global Tooth Regeneration Market : Industry Analysis And Forecast (2020-2027) - Azizsalon News - May 14th, 2020
- Somatic Stem Cells - Methods and Protocols | Shree Ram ... - May 13th, 2020
- What is the Value of iPSC Technology in Cardiac... - The Doctor Weighs In - May 7th, 2020
- Induced Pluripotent Stem Cells Market Latest Trends and Analysis Future Growth Study by 2029 Cole Reports - Cole of Duty - May 4th, 2020
- Global Zinc Finger Nuclease Technology Market to Generate Lucrative Revenue Prospects for Manufacturers After the End of COVID-19 Crisis and Forecast... - May 4th, 2020
- Normal human uterus is colonised by clones with cancer-driving mutations that arise early in life, study finds - Cambridge Network - April 24th, 2020
- Global Tooth Regeneration Market: Industry Analysis and Forecast (2020-2027) - Publicist360 - April 17th, 2020
- Scientists 'Reset' The Age of Stem Cells From a Supercentenarian Who Lived to 114 - ScienceAlert - March 25th, 2020
- Forty Seven and Rocket Pharmaceuticals Announce Research Collaboration for Fanconi Anemia - BioSpace - March 11th, 2020
- Mapping the structure and biological functions within mesenchymal bodies using microfluidics - Science Advances - March 4th, 2020
- Researchers ID Protein-Protein Interaction That Promotes Cancer Development - BioSpace - February 28th, 2020
- Dental Regenerative Market Size, Share 2020 Regional Trend, Future Growth, Leading Players Updates, Industry Demand, Current and Future Plans by... - February 28th, 2020
- Global Gene Therapy Market to Cross Around USD 6892 Million By 2027 - Global Newspaper 24 - February 17th, 2020
- Induced Pluripotent Stem Cells Market Predicted to Witness Surge in the Near Future2018 2028 - TechNews.mobi - February 15th, 2020
- Global Gene Therapy Market Worth Reach USD 6892 Million By 2027 - TheInfobiz - February 12th, 2020
- New research shows what happens to your lung cells once you quit smoking - Daily Gaming Worlld - February 9th, 2020
- Global Gene Therapy Market to Cross USD 6892 Million By 2027 - TheInfobiz - February 6th, 2020
- Scientists finally find link between stress and grey hair - nation.co.ke - January 31st, 2020
- Global Gene Therapy Market is Growing to Reach 6892 Million By 2027 - Market Research News 24 - January 29th, 2020
- Going Gray Too Soon? Scientists Say It Really May Be Due to Stress - Genetic Engineering & Biotechnology News - January 25th, 2020
- Allele and Astellas Enter into an Expanded License for the Development of iPSC Lines - Business Wire - January 20th, 2020
- Duke researchers land $6M in federal grants to advance gene editing - WRAL Tech Wire - January 5th, 2020
- Stem Cells Market- What Are The Main Factors That Contributing Towards Industry Growth? - Industry Mirror - December 31st, 2019
- What a time to be alive: Reproductive breakthroughs of the 2010s that changed life as we know it - FOX 10 News Phoenix - December 29th, 2019
- Gene Therapy Market 2019-2027 / Trends, Growth, Opportunities And Top Key - Market Research Sheets - December 27th, 2019
- Cell Therapy Industry Applications 2019-Size by Type (Allogenic Therapies), by Technique (Stem Cell Therapy), Global Market Growth by Demand Analysis... - December 13th, 2019
- Stem Cell Therapies Market research Likely to Emerge over a Period of 2015-2025 - PharmiWeb.com - December 13th, 2019
- Orgenesis and Theracell to launch point-of-care cell and gene therapy centers in HYGEIA Group"s hospitals - Proactive Investors USA & Canada - December 6th, 2019
- Rocket Pharmaceuticals Announces First Patient Treated in Global Registrational Phase 2 Study of RP-L102 Process B for Fanconi Anemia - BioSpace - December 6th, 2019
- Stem Cell Therapy Industry 2019 Global Market Size, Trends, Revenue, Growth Prospects, Key Companies and Forecast by 2023 - Techi Labs - December 6th, 2019
- Brave new world? Why the public might be ready for gene-edited babies - Genetic Literacy Project - December 6th, 2019
- Stem Cell Therapies Market research to Witness a Healthy Growth during 2015 2025 - Lake Shore Gazette - November 25th, 2019
- Osteonecrosis Treatment Market Benefit and Volume with Status and Prospect to 2026 - Crypto Journal - November 21st, 2019
- US Nobel laureates tell us what they think about cancer research, moonshots, the dark side, funding, meritocracy, herd mentality, Trump, and joy - The... - November 21st, 2019
- Youngstown State, IBM to offer high-tech training in the Mahoning Valley - Crain's Cleveland Business - November 15th, 2019
- A short guide to regulation for disruptive technologies - Lexology - November 14th, 2019
- Cereal rust could lead to new wheat threat - Farm Weekly - November 14th, 2019
- Tooth Regeneration Industry 2019 Research on Market Sales, Revenue, Top Companies and Future Development - TheFinanceTime - November 11th, 2019
- Stem Cell Therapy Market : Opportunities and Challenges - MENAFN.COM - November 3rd, 2019
- Cell Therapy Market Forecast to 2025 | Analysis by Regions, Type, Application, and Top Key Players like Dendreon, Mesoblast, Vericel, Antibe... - November 3rd, 2019
- Detection of Latent HSCs Fated to Progress to Blast Phase in Myelofibrosis Patients Several Years Before Blast Transformation - DocWire News - October 25th, 2019
- Stem cell therapy is for animals too - SciTech Europa - October 21st, 2019
- Stem Cell Therapy Industry 2019 Global Market Size, Trends, Revenue, Growth Prospects, Key Companies and Forecast by 2023 - Markets Gazette - October 17th, 2019
- Significant Growth Foreseen by Stem Cell Therapies Market During 2015 2025 - Rapid News Network - September 22nd, 2019
- Blast Off With Rocket Pharmaceuticals - Seeking Alpha - September 22nd, 2019
- Zinc Finger Nuclease Technology Market Estimated to Discern 2X Expansion by 2025 - Commerce Gazette - September 22nd, 2019
- Tooth Regeneration Market : Huge Growth Opportunity by Trend, Key Players and Forecast 2026 - TodayTimes - September 22nd, 2019
- Direct generation of human naive induced pluripotent stem ... - June 5th, 2019
- Somatic Stem Cells and Cancer - Stem Cell Centers ... - May 4th, 2019
- Difference Between Embryonic and Somatic Stem Cells ... - May 3rd, 2019
- Mosaic (genetics) - Wikipedia - March 8th, 2019
- What is the Difference Between Embryonic and Somatic Stem Cells - February 27th, 2019
- Somatic Cells - Definition and Examples | Biology Dictionary - November 14th, 2018
- Stem Cell Quick Reference - Learn.Genetics - September 9th, 2018
- Where Do Stem Cells Come From? - verywellhealth.com - July 2nd, 2018
- What Is Another Name for Somatic Stem Cells and What Do ... - June 22nd, 2018
- Difference Between Somatic Cells and Gametes ... - June 19th, 2018
- Skin graft gene therapy could treat obesity and diabetes - ResearchGate (blog) - August 3rd, 2017
- Cloning - Wikipedia - December 7th, 2016
- Characterization of Regenerative Phenotype of Unrestricted ... - December 1st, 2016
- Somatic cell nuclear transfer - Wikipedia - November 25th, 2016
- Somatic cell - Wikipedia - November 2nd, 2016
- Embryonic and Somatic Stem Cells, Whats the Difference? - November 2nd, 2016
- Somatic stem cells in the human endometrium. - October 7th, 2016
- Glossary | stemcells.nih.gov - September 17th, 2016
- Stem Cell Basics IV. | stemcells.nih.gov - September 17th, 2016
- Human embryonic stem cells derived by somatic cell nuclear ... - August 3rd, 2015
- Comparative proteomic analysis of human somatic cells ... - July 20th, 2015
- Somatic cell - Wikipedia, the free encyclopedia - July 15th, 2015
- somatic stem cell - Learn Genetics - July 2nd, 2015
- What is the difference between embryonic and somatic stem ... - June 11th, 2015
- Redox Signaling and Stem Cell Function - Dirk Bohmann - June 2nd, 2015
- Adult stem cell - Wikipedia, the free encyclopedia - June 1st, 2015