- Adult stem cell
Adult stem cells are undifferentiated cells found throughout the body after embryonic development 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.
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 creation or 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.
Adult stem cell therapies
Due to the ability of adult stem cells to be cut out from the patient, their therapeutic potential is the focus of much research. [ [Adult stem or progenitor cells in treatment for type 1 diabetes: current progress, Can J Surg, Vol. 50, No. 2, April 2007] ] [ [Stem Cells: A Revolution in Therapeutics—Recent Advances in Stem Cell Biology and Their Therapeutic Applications in Regenerative Medicine and Cancer Therapies, Clinical Pharmacology & Therapeutics (2007) 82, 252–264;] ] [ [Stem Cells and Their Potential in Cell-Based Cardiac Therapies,Progress in Cardiovascular Diseases such as sneezotachiousVolume 49, Issue 6, May-June 2007, Pages 396-413] ] Adult stem cells, similar to embryonic stem cells, have the ability to differentiate into more than one cell type, but unlike embryonic stem cells they are often restricted to certain lineages. The ability of a stem cell of one lineage to become another lineage is called transdifferentiation. Different types of adult stem cells are capable of transdifferentiation more than others, and for many there is no evidence of its occurrence. 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. [ [ADULT STEM CELL PLASTICITY: Fact or Artifact?, Annual Review of Cell and Developmental Biology Vol. 19: 1-22] ] [ [http://www.sciencemag.org/cgi/content/full/316/5830/1422b|Adult Versus Embryonic Stem Cells: Treatments, Science 8 June 2007:Vol. 316. no. 5830, pp. 1422 - 1423] ]
Pluripotent stem cells can be found in a number of tissues including umbilical cord blood. [cite journal |author=Ratajczak MZ, Machalinski B, Wojakowski W, Ratajczak J, Kucia M |title=A hypothesis for an embryonic origin of pluripotent Oct-4(+) stem cells in adult bone marrow and other tissues |journal=Leukemia |volume=21 |issue=5 |pages=860–7 |year=2007 |pmid=17344915 |doi=10.1038/sj.leu.2404630] Using genetic reprogramming, pluripotent stem cells equivalent to
embryonic stem cellshave been derived from human adult skin tissue. [cite web|url=http://www.nytimes.com/2007/11/22/science/22stem.html|title=Man Who Helped Start Stem Cell War May End It|author=Gina Kolata|publisher= New York Times|date=2007-11-22] [cite web|url=http://www.nytimes.com/2007/11/21/science/21stem.html?em&ex=1195880400&en=18114796981c0299&ei=5087%0A|title=Scientists Bypass Need for Embryo to Get Stem Cells|author=Gina Kolata|date=2007-11-21|publisher= New York Times] cite web|title=Me too, too - How to make human embryonic stem cells without destroying human embryos|publisher= The Economist|url=http://www.economist.com/science/displaystory.cfm?story_id=10170972|date=2007-11-22] [cite web|url=http://www.theglobeandmail.com/servlet/story/RTGAM.20071121.wstemcells21/BNStory/Science/home|title=Stem-cell method hailed as 'massive breakthrough'|author=Anne McIlroy|date=2007-11-21|publisher= Globe and Mail] [cite web|title=A Breakthrough on Stem Cells|publisher= Time Magazine|url=http://www.time.com/time/health/article/0,8599,1685965,00.html|author=Alice Park|date=2007-11-20] Other adult stem cells are lineage-restricted ( multipotent) and are generally referred to by their tissue origin ( mesenchymal stem cell, adipose-derived stem cell, endothelial stem cell, etc.). [cite journal |author=Barrilleaux B, Phinney DG, Prockop DJ, O'Connor KC |title=Review: ex vivo engineering of living tissues with adult stem cells |journal=Tissue Eng. |volume=12 |issue=11 |pages=3007–19 |year=2006 |pmid=17518617 |doi=10.1089/ten.2006.12.3007] [cite journal |author=Gimble JM, Katz AJ, Bunnell BA |title=Adipose-derived stem cells for regenerative medicine |journal=Circ. Res. |volume=100 |issue=9 |pages=1249–60 |year=2007 |pmid=17495232 |doi=10.1161/01.RES.0000265074.83288.09]
A great deal of adult stem cell research has focused on clarifying their capacity to divide or self-renew indefinitely and their differentiation potential. [cite journal | author = Gardner RL | title = Stem cells: potency, plasticity and public perception | journal = Journal of Anatomy | volume = 200 | issue = 3 | pages = 277–82 | year = 2002 | pmid = 12033732 | doi=10.1046/j.1469-7580.2002.00029.x] In mice, pluripotent stem cells can be directly generated from adult fibroblast cultures. [cite journal |author=Takahashi K, Yamanaka S |title=Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors |journal=Cell |volume=126 |issue=4 |pages=663–76 |year=2006 |pmid=16904174 |doi=10.1016/j.cell.2006.07.024]
Adult stem cell treatments have been used for many years to treat successfully leukemia and related bone/blood cancers through bone marrow transplants. [ [http://www.ucsfhealth.org/childrens/medical_services/cancer/bmt/treatments/leukemia.html] , Bone Marrow Transplant] 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. Consequently, more US government funding is being provided for adult stem cell research [ [http://www.hhs.gov/news/press/2004pres/20040714b.html] ,USDHHS Stem Cell FAQ 2004] .
Adult Stem Cell and Cancer
In recent years, the concept of adult stem cells has grown. There is now a theory that stem cells reside in many adult tissues and that these unique reservoirs 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 in many abnormal conditions including cancer [http://lib.bioinfo.pl/auth:Heidaran,M] [http://www.mayoclinicproceedings.com/pdf/7808/7808sa.pdf] ..
The rigorous definition of a
stem cellrequires that it possesses two properties:
* "Self-renewal" - the ability to go through numerous cycles of
cell divisionwhile 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 unipotentself-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 cultureconditions 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.
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 cellwith 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.
Adult stem cells express
transporters of the ATP-binding cassette family that actively pump a diversity of organic molecules out of the cell. [cite journal | author=Chaudhary PM and Roninson IB | year=1991 | title=Expression and activity of P-glycoprotein, a multidrug efflux pump, in human hematopoietic stem cells | journal=Cell | volume=66 | issue=1 | pages=85–94 | doi=10.1016/0092-8674(91)90141-K Entrez Pubmed|1712673] Many pharmaceuticals are exported by these transporters conferring multidrug resistanceonto 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.
repressor Bmi-1is one of the Polycomb-group proteinsthat was discovered as a common oncogeneactivated in lymphoma [cite journal| author=Haupt Y, Bath ML, Harris AW and Adams JM | year=1993 | title=bmi-1 transgene induces lymphomas and collaborates with myc in tumorigenesis | journal=Oncogene | volume=8 | pages=3161–3164 Entrez Pubmed|8414519] and later shown to specifically regulate HSCs [cite journal | author=Park IK, Qian D, Kiel M, Becker MW, Pihalja M, Weissman IL, Morrison SJ and Clarke MF | year=2003 | title=Bmi-1 is required for maintenance of adult self-renewing haematopoietic stem cells | journal=Nature | volume=423 | pages=302–305 | doi=10.1038/nature01587 Entrez Pubmed|12714971] . The role of Bmi-1 has also been illustrated in neural stem cells. [cite journal | author=Molofsky AV, Pardal R, Iwashita T, Park IK, Clarke MF and Morrison SJ | year=2003 | title=Bmi-1 dependence distinguishes neural stem cell self-renewal from progenitor proliferation | journal=Nature | volume=425 | pages=962–967 | doi=10.1038/nature02060 Entrez Pubmed|14574365]
Notch pathwayhas 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 [cite journal| author=Dontu G, Jackson KW, McNicholas E, Kawamura MJ, Abdallah WM and Wicha MS | year=2004 | title=Role of Notch signaling in cell-fate determination of human mammary stem/progenitor cells | journal=Breast Cancer Res | volume=6 | pages=R605–615 | doi=10.1186/bcr920 PMC|1064073] stem cells.
*Wnt:These developmental pathways are also strongly implicated as stem cell regulators. [cite journal | author=Beachy PA, Karhadkar SS and Berman DM | year=2004 | title=Tissue repair and stem cell renewal in carcinogenesis | journal=Nature | volume=432 | pages=324–331 | doi=10.1038/nature03100 Entrez Pubmed|15549094]
Under special conditions tissue-specific adult stem cells can generate a whole spectrum of
cell types of other tissues, even crossing germ layers. [cite journal | author=Filip S, English D and Mokry J | year=2004 | title=Issues in stem cell plasticity | journal=J Cell Mol Med | volume=8 | issue=4 | pages=572–577 | doi=10.1111/j.1582-4934.2004.tb00483.x Entrez Pubmed|15601587] This phenomenon is referred to as stem cell transdifferentiationor plasticity. It can be induced by modifying the growth mediumwhen 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.
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, and muscle, while ASCs from rats have been converted to neurons [cite web|url=http://news.bbc.co.uk/2/hi/health/7049601.stm|title=New nerves grown from fat cells|publisher= BBC|date=2007-10-19] , which makes ASCs a possible source for future applications in the clinic. [cite journal| author=Zuk PA, Zhu M, Mizuno H, Huang JI, Chaudhari S, Lorenz HP, Benhaim P and Hedrick MH | title=Mutilineage cells derived from human adipose tissue: a putative source of stem cells for tissue engineering | journal=Tissue Engineering | volume=7 | issue=2 | pages=211–216 | year=2001| doi=10.1089/107632701300062859] [cite journal| author=Zuk PA, Zhu M, Ashjian P, De Ugarte DA, Huang JI, Mizuno H, Alfonso ZC, Fraser JK, Benhaim P and Hedrick MH | title=Human adipose tissue is a source of multipotent stem cells | journal=Mol Biol Cell | volume=13 | pages=4279–4295 | year=2002 | doi=10.1091/mbc.E02-02-0105 | pmid=12475952] 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. [cite web|url=http://www.msnbc.msn.com/id/6727466/|title=Stem cells from fat used to repair girl's skull|author= Associated Press|publisher= MSNBC|date=2004-12-20] ASCs are currently in use in veterinary medicine in horses and dogs, typically to aid in the repair of damaged tendons or ligaments, but also in joints. [cite web|url=http://www.newsweek.com/id/40411|title=Help for Hounds|first=Jamie |last=Reno|publisher= Newsweek|date=2008-04-30|accessdate=2008-04-30]
Induced pluripotent stem cells derived from epithelial cells
These are not adult stem cells, but rather reprogrammed epithelial cells with pluripotent capabilities. Using genetic reprogramming with protein
transcription factors, pluripotent stem cells equivalent to embryonic stem cellshave been derived from human adult skin tissue. [cite web|url=http://www.npr.org/templates/story/story.php?storyId=16466265|publisher= National Public Radio|title=Skin Cells Can Become Embryonic Stem Cells|author=Madeleine Brand, Joe Palca and Alex Cohen|date=2007-11-20] [cite web|url=http://www.pbs.org/newshour/bb/science/july-dec07/stemcells_11-20.html|title=Breakthrough Set to Radically Change Stem Cell Debate|publisher= News Hour with Jim Lehrer|date=2007-11-20] Shinya Yamanaka and his colleagues at Kyoto Universityused the transcription factors Oct3/4, Sox2, c-Myc, and Klf4 in their experiments on cells from human faces. Junying Yu, James Thomson, and their colleagues at the University of Wisconsin-Madisonused a different set of factors, Oct4, Sox2, Nanog and Lin28 , and carried out their experiments using cells from human foreskin.
As a result of the success of these experiments,
Ian Wilmut, who helped create the first cloned animal Dolly the Sheep, has announced that he will abandon theraputic cloning as an avenue of research. ["His inspiration comes from the research by Prof Shinya Yamanaka at Kyoto University, which suggests a way to create human embryo stem cells without the need for human eggs, which are in extremely short supply, and without the need to create and destroy human cloned embryos, which is bitterly opposed by the pro life movement."cite web|url=http://www.telegraph.co.uk/earth/main.jhtml?view=DETAILS&grid=A1YourView&xml=/earth/2007/11/16/scidolly116.xml|title=Dolly creator Prof Ian Wilmut shuns cloning|author=Roger Highfield|date=2007-11-16|publisher=The Telegraph]
Haematopoietic stem cells
Haematopoietic stem cells give rise to all the blood cell types and are found in the
Mammary stem cells
Mammary stem cells provide the source of cells for growth of the
mammary glandduring puberty and gestationand play an important role in carcinogenesisof the breast. [cite journal | author=Liu S, Dontu G and Wicha MS | title=Mammary stem cells, self-renewal pathways, and carcinogenesis | year=2005 | journal=Breast Cancer Res | volume=7 | issue=3 | pages=86–95 | doi=10.1186/bcr1021 Entrez Pubmed|15987436] 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 celltypes of the gland and has been shown to regenerate the entire organ in mice. [cite journal | author=Shackleton M, Vaillant F, Simpson KJ, Stingl J, Smyth GK, Asselin-Labat ML, Wu L, Lindeman GJ and Visvader JE | title=Mammary stem cells, self-renewal pathways, and carcinogenesis | year=2005 | journal=Breast Cancer Res | volume=7 | issue=3 | pages=86–95 | doi=10.1186/bcr1021 Entrez Pubmed|15987436]
Mesenchymal stem cells
Mesenchymal stem cells differentiate into connective tissue, and are found in the bone marrow.
Endothelial stem 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. [cite journal | author=Altman J and Das GD | title=Autoradiographic and histological evidence of postnatal hippocampal neurogenesis in rats | journal=J Comp Neurol | year=1965 | volume=124 | issue=3 | pages=319–335 | doi=10.1002/cne.901240303 Entrez Pubmed|5861717] 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 ventriclesof the brain, and the dentate gyrusof the hippocampal formation. [cite journal | author=Alvarez-Buylla A, Seri B, Doetsch F | title=Identification of neural stem cells in the adult vertebrate brain | journal=Brain Res Bull | year=2002 | volume=57 | issue=6 | pages=751–758 | doi=10.1016/S0361-9230(01)00770-5 Entrez Pubmed|12031271] Although the generation of new neurons in the hippocampusis well established, the presence of true self-renewing stem cells there has been debated. [cite journal | author=Bull ND and Bartlett PF | title=The adult mouse hippocampal progenitor is neurogenic but not a stem cell | journal=J Neurosci | year=2005 | volume=25 | issue=47 | pages=10815–10821 | doi=10.1523/JNEUROSCI.3249-05.2005 | pmid=16306394 Entrez Pubmed|16306394] 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 heterogeneousaggregates of cells, containing a large proportion of stem cells. [cite journal | author=Reynolds BA and Weiss S | title=Generation of neurons and astrocytes from isolated cells of the adult mammalian central nervous system | journal=Science | year=1992 | volume=255 | pages=1707–1710 | doi=10.1126/science.1553558 | pmid=1553558 Entrez Pubmed|1553558] 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". [cite journal | author=Doetsch F, Petreanu L, Caille I, Garcia-Verdugo JM and Alvarez-Buylla A | title=EGF converts transit-amplifying neurogenic precursors in the adult brain into multipotent stem cells | journal=Neuron | year=2002 | volume=36 | issue=6 | pages=1021–1034 | doi=10.1016/S0896-6273(02)01133-9 Entrez Pubmed|12495619] Furthermore, neurosphere-derived cells do not behave as stem cells when transplanted back into the brain. [cite journal | author=Marshall GP 2nd, Laywell ED, Zheng T, Steindler DA and Scott EW | title=In vitro-derived "neural stem cells" function as neural progenitors without the capacity for self-renewal | journal=Stem Cells | year=2006 | volume=24 | issue=3 | pages=731–738 | doi=10.1634/stemcells.2005-0245 | pmid=16339644 Entrez Pubmed|16339644]
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. [cite journal | author=Bjornson CR, Rietze RL, Reynolds BA, Magli MC and Vescovi AL | title=Turning brain into blood: a hematopoietic fate adopted by adult neural stem cells in vivo | journal=Science | year=1999 | volume=283 | pages=534–537 | doi=10.1126/science.283.5401.534 | pmid=9915700 Entrez Pubmed|9915700] Cells that resemble neural stem cells have been found in the bone marrow, the home of HSCs. [cite journal | author=Kucia M, Zhang YP, Reca R, Wysoczynski M, Machalinski B, Majka M, Ildstad ST, Ratajczak J, Shields CB and Ratajczak MZ | title=Cells enriched in markers of neural tissue-committed stem cells reside in the bone marrow and are mobilized into the peripheral blood following stroke | journal=Leukemia | year=2006 | volume=20 | issue=1 | pages=18–28 | doi=10.1038/sj.leu.2404011 Entrez Pubmed|16270036] 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.
Olfactory adult stem cells
Olfactory adult stem cells have been successfully harvested from the human olfactory mucosa cells, the lining of the
noseinvolved in the sense of smell. [cite journal | author=Murrell W, Feron F, Wetzig A, Cameron N, Splatt K, Bellette B, Bianco J, Perry C, Lee G and Mackay-Sim A | title=Multipotent stem cells from adult olfactory mucosa | journal=Dev Dyn | year=2005 | volume=233 | issue=2 | pages=496–515 | doi=10.1002/dvdy.20360 Entrez Pubmed|15782416]
: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.
Multipotent stem cells with a claimed equivalency to embryonic stem cells have been derived from spermatogonial progenitor cells found in the
testiclesof laboratory mice by scientists in Germany[cite web|url=http://news.bbc.co.uk/1/hi/health/4841786.stm|publisher= BBC|title=Testicle cells may aid research|date=2006-03-25] [cite web|url=http://www.cbsnews.com/stories/2006/03/24/tech/main1439514.shtml|title=Study: Mice Testes Act Like Stem Cells|date=2006-03-24|publisher= CBS|author= CBS/ Associated Press] [cite web|url=http://www.washingtonpost.com/wp-dyn/content/article/2006/03/24/AR2006032401721.html|publisher= Washington Post|date=2006-03-25|title=Embryonic Stem Cell Success|author=Rick Weiss] and the United States, [cite web|url=http://www.sciencedaily.com/releases/2007/09/070919131804.htm|publisher= Science Daily|title=Promising New Source Of Stem Cells: Mouse Testes Produce Wide Range Of Tissue Types|date=2007-09-24|author=] [cite web|title=Testicles yield stem cells in science breakthrough|url=http://abc.net.au/news/stories/2007/09/20/2039030.htm?section=world|author=Babara Miller|date=2007-09-20|publisher= Australian Broadcasting Corporation] [cite web|url=http://www.sciam.com/article.cfm?articleID=1F52615A-E7F2-99DF-3EB290B3C5A45982|publisher= Scientific American|title=Testes May Prove Fertile Source of Stem Cells|author=J.R. Minkel|date=2007-09-19] [cite web|url=http://news.med.cornell.edu/wcmc/wcmc_2007/09_20_07-2.shtml|title=Stem Cells in Adult Testes Provide Alternative to Embryonic Stem Cells for Organ Regeneration|publisher= Cornell University|date=2007-09-20] and, a year later, researchers from Germany and the United Kingdom confirmed the same capability using cells from the testicles of humans [cite web|url=http://www.bloomberg.com/apps/news?pid=20601124&sid=aNmiXs8SPp4w&refer=home|date=2008-10-08|title=Testicle Stem Cells Become Bone, Muscle in German Experiments |author=Rob Waters|publisher= Bloomberg] . The extracted stem cells are known as human adult germline stem cells (GSCs) [cite web|url=http://www.technologyreview.com/biomedicine/21487/|title=A Source of Men's Stem Cells - Stem cells from human testes could be used for personalized medicine. |author=Nora Schultz|date=2008-10-09|publisher= Technology Review]
Multipotent stem cells have also been derived from
germ cells found in human testicles. [cite web|url=http://www.washingtonpost.com/wp-dyn/content/article/2006/04/01/AR2006040101145.html|title=U.S. Firm Says It Made Stem Cells From Human Testes|author=Maggie Fox ( Reuters)|publisher= Washington Post|date=2006-04-02]
Dental pulp derived Stem Cells
Multipotent stem cells have been successfully recovered from dental pulp in the perivascular niche. Known as SHED cells (Stem cells Harvested from Exfoliated Deciduous teeth), they have been shown to have the same cellular markers and differential abilities of Mesenchymal Stem cells.
As deciduous baby teeth are shed naturally, this is a non invasive, painless way to harvest stem cells either for storage or future medical use.
Open questions in adult stem cell research
* How do adult stem cells arise? Are they residual embryonic stem cells? If so, what has stopped them differentiating: why are they still stem cells when most cells have differentiated?
* 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
* 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 cellproperties in adult stem cells or even differentiated cells?
News and External links
* [http://stemcells.nih.gov/ NIH Stem Cell Information Resource] , resource for stem cell research
* [http://stemcells.alphamedpress.org/ Stem Cells] , the international journal for cell differentiation and proliferation
* [http://www.nature.com/stemcells Nature Reports Stem Cells] Background information, research advances and debates about stem cell science
* [http://www.stemcellcordblood.net Stem Cell and Cord Blood information database]
* [http://stemcell.insysbio.ru Encyclopaedia of Stem Cells] , database which represents signaling and differentiation pathways of stem cells in compact graphic view
* [http://www.stemcellresearch.org/facts/treatments.htm Check The Score] , Successes of Adult Stem Cells vs. Embryonic Stem Cells
* [http://whaaz.wikidot.com whaaz] a science wiki site for updates on stem cells and other related topics
* [http://www.regenecell.com Regenecell] Adult stem cell treatments worldwide
* [http://www.brainstorm-cell.com/ BrainStorm Cell Therapeutics Inc.] Adult Stem Cell research center on potential cure for
* [http://www.som.tulane.edu/gene_therapy/distribute.shtml Tulane University Centre for Gene Therapy] , prepares and distributes marrow stromal cells for academic research
* [http://www.umdnj.edu/gsbsnweb/stemcell/ UMDNJ Stem Cell and Regenerative Medicine] , provides educational materials and research resources
* [http://adult-stem-cells.info/research.html Triple-Blind Randomized Placebo Controlled Study on Bone Marrow (Adult) Stem Cell Mobilization]
* REGENERATE@bartsandthelondon.nhs.uk Randomised Controlled trial recruiting patients to investigate if the use of a persons own bone marrow can regenerate cardiac muscle cells in people with heart failure caused by Coronary Heart Disease
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