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[[Image:Mouse embryonic stem cells.jpg|right|thumb|300px|[[Mus musculus|Mouse]] [[Mammalian embryogenesis|embryo]]nic stem cells with fluorescent marker]]
[[Image:Human embryonic stem cell colony phase.jpg|right|thumb|300px|Human embryonic stem cell colony on mouse embryonic fibroblast feeder layer]]
'''Stem cells''' are [[cell (biology)|biological cells]] found in all multicellular [[organisms]], that can [[cell division|divide]] through [[mitosis]] and [[Cellular differentiation|differentiate]] into diverse specialized cell types and can self renew to produce more stem cells. In mammals, there are two broad types of stem cells: [[embryonic stem cell]]s that are isolated from the [[inner cell mass]] of [[blastocyst]]s, and [[adult stem cell]]s that are found in various tissues. In [[adult]] organisms, stem cells and [[progenitor cell]]s act as a repair system for the body, replenished in adult tissues. In a developing embryo, stem cells can differentiate into all the specialized cells, but also maintain the normal turnover of regenerative organs, such as blood, skin, or intestinal tissues.

Stem cells can now be into specialized cell types with characteristics consistent with cells of various tissues such as muscles or nerves through [[cell culture]]. | author=Tuch BE | title=Stem cells—a clinical update | journal=[[Australian Family Physician]] | volume=35 | issue=9 | pages=719–21 | year=2006 | pmid=16969445}}</ref> Research of stem cells grew out of findings by [[Ernest McCulloch|Ernest A. McCulloch]] and [[James Till|James E. Till]] at the [[University of Toronto]] in the 1960s.<ref>{{cite journal | author = Becker AJ, McCulloch EA, Till JE | title = Cytological demonstration of the clonal nature of spleen colonies derived from transplanted mouse marrow cells | journal = Nature | volume = 197 | issue = 4866 | pages = 452–4 | year = 1963 | pmid = 13970094 | doi=10.1038/197452a0 }}</ref><ref>{{cite journal | author = Siminovitch L, McCulloch EA, Till JE | title = The distribution of colony-forming cells among spleen colonies | journal = Journal of Cellular and Comparative Physiology | volume = 62 | issue = 3| pages = 327–36 | year = 1963 | pmid = 14086156 | doi = 10.1002/jcp.1030620313}}</ref>

==Properties==
The classical definition of a stem cell requires that it possess two properties:
* ''Self-renewal'' - the ability to go through numerous [[cell cycle|cycles]] of [[cell division]] while maintaining the undifferentiated state.
* ''Potency'' Cellular differentiation|differentiate]] into specialized cell types. In the strictest sense, this requires stem cells to be either [[totipotency|totipotent]] or [[pluripotency|pluripotent]] - to be able to give rise to any mature cell type, although [[multipotent]] or [[unipotent cell|unipotent]] [[progenitor cell]]s are sometimes referred to as stem cells.

===Self-renewal===
Two mechanisms exist to ensure that the stem cell population is maintained:
# [[Asymmetric cellcell develops into two differentiated daughter cells, another stem cell undergoes [[mitosis]] and produces two stem cells identical to the original.

===Potency definitions===
[[Image:Stem cells diagram.png|400px|thumb|right|Pluripotent, embryonic stem cells originate as inner mass cells within a blastocyst. The stem cells can become any tissue in the body, excluding a placenta. Only the morula's cells are totipotent, able to become all tissues and a placenta.]]
[[Image:}}
''Potency'' specifies the differentiation potential (the potential to differentiate into different cell types) of the stem cell.<ref name=Schoeler>{{cite book |title=Humanbiotechnology as Social Challenge |editor=Nikolaus Knoepffler, Dagmar Schipanski, and Stefan Lorenz Sorgner |page=28 |chapter=The Potential of Stem Cells: An Inventory |author=Hans R. Sch&ouml;ler |publisher=Ashgate Publishing, Ltd |year=2007 |isbn=0754657558 |isbn13=9780754657552}}</ref>

* [[Totipotency|Totipotent]] (a.k.a omnipotent) stem cells can differentiate into embryonic and extraembryonic cell types. Such cells can construct a complete, viable organism.<ref name=Schoeler/> These cells are produced from the fusion of an egg and sperm cell. Cells |pmc=2752493 |doi=10.1007/10_2008_45 }}</ref>
* [[Pluripotency|Pluripotent]] stem cells are the descendants of totipotent cells and can differentiate into nearly all cells,<ref name=Schoeler/> i.e. cells derived from any of the three [[germ layer]]s.<ref>{{cite journal |author=Ulloa-Montoya F, Verfaillie CM, Hu WS |title=Culture systems for pluripotent stem cells |journal=J Biosci Bioeng. |volume=100 |issue=1 |pages=12–27 |year=2005 |month=Jul |pmid=16233846 |doi=10.1263/jbb.100.12 }}</ref>
* [[Multipotency|Multipotent]] stem cells can differentiate into a number of cells, but only those of a closely related family of cells.<ref name=Schoeler/>
* [[Oligopotency|Oligopotent]] stem cells can differentiate into only a few cells, such as lymphoid or myeloid stem cells.<ref name=Schoeler/>
* [[Unipotency|Unipotent]] cells can produce only one cell type, their own,<ref name=Schoeler/> but have the property of self-renewal which distinguishes them from non-stem cells (e.g. muscle stem cells).

===Identification===
The practical definition of a stem cell is the functional definition - a cell that has the potential to regenerate tissue over a lifetime. For example,individual without HSCs, demonstrating that the stem cell was able to self-renew.

Properties of stem cells can be illustrated ''[[in vitro]]'', using methods such as [[mesenchymal stem cell|clonogenic assay]]s, where single cells are characterized by their ability to differentiate and self-renew.<ref>{{cite journal
| author = Friedenstein AJ, Deriglasova UF, Kulagina NN, Panasuk AF, Rudakowa SF, Luria EA, Ruadkow IA
| title = Precursors for fibroblasts in different populations of hematopoietic cells as detected by the ''in vitro'' colony assay method
| journal = Exp Hematol
| volume = 2
| issue = 2
| pages = 83–92
| year = 1974
| pmid = 4455512
}}</ref><ref>
{{cite journal
| author = Friedenstein AJ, Gorskaja JF, Kulagina NN
| title = Fibroblast precursors in normal and irradiated mouse hematopoietic organs
| journal = Exp Hematol
| volume = 4
| issue = 5
| pages = 267–74
| year = 1976
| pmid = 976387
}}</ref> As well, stem cells can be isolated based on a distinctive set of cell surface markers. However, ''in vitro'' culture conditions can alter the behavior of cells, making it unclear whether the cells will behave in a similar manner ''[[in vivo]]''. Considerable debate exists whether some proposed adult cell populations are truly stem cells.

==Embryonic==
{{Main|Embryonic stem cell}}

Embryonic stem cell lines (ES cell lines) are cultures of cells derived from the [[epiblast]] tissue of the [[inner cell mass]] (ICM) of a [[blastocyst]] or earlier [[morula]] stage embryos.<ref>
{{cite news
|url=http://www.foxnews.com/story/0,2933,210078,00.html
|publisher=Fox News
|title=New Stem-Cell Procedure Doesn't Harm Embryos, Company Claims
|accessdate=2010-02-28
| date=2006-08-24
}}</ref> A blastocyst is an early stage [[embryo]]—approximately four to five days old in humans and consisting of 50–150 cells. ES cells are [[pluripotent]] and give rise during development to all derivatives of the three primary [[germ layer]]s: ectoderm, endoderm and mesoderm. In other words, they can develop into each of the more than 200 cell types of the adult [[human body|body]] when given sufficient and necessary stimulation for a specific cell type. They do not contribute to the extra-embryonic membranes or the [[placenta]]. The endoderm is composed of the entire gut tube and the lungs, the ectoderm gives rise to the nervous system and skin, and the mesoderm gives rise to muscle, bone, blood, basically everything else that connects the endoderm to the ectoderm.

Nearly all research to date has taken place using mouse embryonic stem cells (mES) or human embryonic stem cells (hES). Both have the essential stem cell characteristics, yet they require very different environments in order to maintain an undifferentiated state. Mouse ES cells are grown on a layer of gelatin and require the presence of Leukemia Inhibitory Factor (LIF).<ref>
{{cite web
|url=https://catalog.invitrogen.com/index.cfm?fuseaction=iProtocol.unitSectionTree&treeNodeID=9E662600C6C10276D8E040E99EA33BB0
|title=Mouse Embryonic Stem (ES) Cell Culture-Current Protocols in Molecular Biology
}}{{Dead link|date=February 2010}}</ref> Human ES cells are grown on a feeder layer of mouse embryonic [[fibroblasts]] (MEFs) and require the presence of basic Fibroblast Growth Factor (bFGF or FGF-2).<ref>
{{cite web
|url=http://stemcells.nih.gov/research/NIHresearch/scunit/culture.asp
|title=Culture of Human Embryonic Stem Cells (hESC)
|publisher=National Institutes of Health
|accessdate=2010-03-07
}}</ref> Without optimal culture conditions or genetic manipulation,<ref>
{{cite journal
|author=Chambers I, Colby D, Robertson M, ''et al.''
|title=Functional expression cloning of Nanog, a pluripotency sustaining factor in embryonic stem cells
|journal=Cell
|volume=113
|issue=5
|pages=643–55
|year=2003
|pmid=12787505
|doi=10.1016/S0092-8674(03)00392-1
}}</ref> embryonic stem cells will rapidly differentiate.

A human embryonic stem cell is also defined by the presence of several transcription factors and cell surface proteins. The transcription factors [[Oct-4]], [[Nanog]], and [[Sox2]] form the core regulatory network that ensures the suppression of genes that lead to differentiation and the maintenance of pluripotency.<ref>
{{cite journal
|author=Boyer LA, Lee TI, Cole MF, ''et al.''
|title=Core transcriptional regulatory circuitry in human embryonic stem cells
|journal=Cell
|volume=122
|issue=6
|pages=947–56
|year=2005
|pmid=16153702
|pmc=3006442
|doi=10.1016/j.cell.2005.08.020
}}</ref> The cell surface antigens most commonly used to identify hES cells are the glycolipids SSEA3 and SSEA4 and the keratan sulfate antigens Tra-1-60 and Tra-1-81. The molecular definition of a stem cell includes many more proteins and continues to be a topic of research.<ref>
{{cite journal
|author=Adewumi O, Aflatoonian B, Ahrlund-Richter L, ''et al.''
|title=Characterization of human embryonic stem cell lines by the International Stem Cell Initiative
|journal=Nat. Biotechnol
|volume=25
|issue=7
|pages=803–16
|year=2007
|pmid=17572666
|doi=10.1038/nbt1318
}}</ref>

There are currently no approved treatments using embryonic stem cells. The first human trial was approved by the US Food & Drug Administration in January 2009.<ref>
{{cite journal
| author = Ron Winslow
| title = First Embryonic Stem-Cell Trial Gets Approval from the FDA
| series = 23
| journal = The Wall Street Journal
| volume = January 2009
| issue =
| pages =
| year = 2009
| pmid =
| doi =
}}</ref> However, as of August 2010, the first human trial had not yet been initiated. The first human medical trial for embryonic stem cells started in Atlanta on October 13, 2010 for spinal injury victims. ES cells, being pluripotent cells, require specific signals for correct differentiation - if injected directly into another body, ES cells will differentiate into many different types of cells, causing a [[teratoma]]. Differentiating ES cells into usable cells while avoiding transplant rejection are just a few of the hurdles that embryonic stem cell researchers still face.<ref>
{{cite journal
|author=Wu DC, Boyd AS, Wood KJ
|title=Embryonic stem cell transplantation: potential applicability in cell replacement therapy and regenerative medicine
|journal=Front Biosci
|volume=12
|issue=
8-12|pages=4525–35
|year=2007
|pmid=17485394
|doi=10.2741/2407
}}</ref> Many nations currently have [[moratorium (law)|moratoria]] on either ES cell research or the production of new ES cell lines. Because of their combined abilities of unlimited expansion and pluripotency, embryonic stem cells remain a theoretically potential source for [[regenerative medicine]] and tissue replacement after injury or disease.

==Fetal==
The primitive stem cells located in the organs of fetuses are referred to as fetal stem cells.<ref name="isbn981-256-126-9">
{{cite book
|author=Ariff Bongso; Eng Hin Lee
|editor=Ariff Bongso; Eng Hin Lee
|title=Stem Cells: From Benchtop to Bedside
|chapter=Stem cells: their definition, classification and sources
|publisher=World Scientific
|year=2005
|pages=5
|isbn=981-256-126-9
|oclc=443407924
}}</ref>

==Adult==
{{Main|Adult stem cell}}

[[Image:Stem cell division and differentiation.svg|thumb|160px|Stem cell division and differentiation. A - stem cell; B - progenitor cell; C - differentiated cell; 1 - symmetric stem cell division; 2 - asymmetric stem cell division; 3 - progenitor division; 4 - terminal differentiation]]

Also known as [[somatic]] (from Greek Σωματικóς, "of the body") stem cells and germline (giving rise to gametes) stem cells, they can be found in children, as well as adults.<ref>
{{cite journal
|author=Jiang Y, Jahagirdar BN, Reinhardt RL, ''et al.''
|title=Pluripotency of mesenchymal stem cells derived from adult marrow
|journal=Nature
|volume=418
|issue=6893
|pages=41–9
|year=2002
|pmid=12077603
|doi=10.1038/nature00870
}}</ref>

Pluripotent adult stem cells are rare and generally small in number but can be found in a number of tissues including umbilical cord blood.<ref>
{{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
}}</ref> A great deal of adult stem cell research has focused on clarifying their capacity to divide or self-renew indefinitely and their differentiation potential.<ref>
{{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
| pmc = 1570679
}}</ref> In mice, pluripotent stem cells are directly generated from adult fibroblast cultures. Unfortunately, many mice don't live long with stem cell organs.<ref name="Takahashi2006">
{{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}}</ref>

Most 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]], [[dental pulp stem cell]], etc.).<ref>
{{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
}}</ref><ref>
{{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
}}</ref>

Adult stem cell treatments have been successfully used for many years to treat leukemia and related bone/blood cancers through bone marrow transplants.<ref>
{{cite web
|url=http://www.ucsfchildrenshospital.org/treatments/leukemia_treatment_options/index.html
|title=Bone Marrow Transplant
}}</ref> Adult stem cells are also used in veterinary medicine to treat tendon and ligament injuries in horses.<ref>{{cite news
|first=Ed
|last=Kane
|title=Stem-cell therapy shows promise for horse soft-tissue injury, disease
|url=http://veterinarynews.dvm360.com/dvm/Equine+Medicine/Stem-cell-therapy-shows-promise-for-horse-soft-tis/ArticleStandard/Article/detail/515503
|publisher=DVM Newsmagazine
|date=2008-05-01
|accessdate=2008-06-12
}}</ref>

The use of adult stem cells in research and therapy is not as [[Stem cell controversy|controversial]] as [[embryonic stem cell]]s, because the production of adult stem cells does not require the destruction of an [[embryo]]. Additionally, because in some instances adult stem cells can be obtained from the intended recipient, (an [[autograft]]) the risk of rejection is essentially non-existent in these situations. Consequently, more US government funding is being provided for adult stem cell research.<ref>
{{cite web
|url=http://www.hhs.gov/news/press/2004pres/20040714b.html
|publisher=US Department of Health and Human Services
|title=Stem Cell FAQ
|year=2004
|accessdate=2010-03-07
}} {{Dead link|date=September 2010|bot=H3llBot}}</ref>

An extremely rich source for adult mesenchymal stem cells is the developing tooth bud of the mandibular third molar. While considered multipotent they may prove to be pluripotent. The stem cells eventually form enamel (ectodrm), dentin,periodontal ligament, blood vessels, dental pulp, nervous tissues, including a minimum of 29 different unique end organs. Because of extreme ease in collection at 8–10 years of age before calcification and minimal to no morbidity will probably constitute a major source for personal banking, research and multiple therapies. These stem cells have been shown capable of producing hepatocytes.{{Citation needed|date=June 2010}}

==Amniotic==

Multipotent stem cells are also found in [[amniotic fluid]]. These stem cells are very active, expand extensively without feeders and are not tumorigenic. [[Amniotic stem cells]] are multipotent and can differentiate in cells of adipogenic, osteogenic, myogenic, endothelial, hepatic and also neuronal lines.<ref>
{{cite journal
|author=P. De Coppi, G Barstch, Anthony Atala
|title=Isolation of amniotic stem cell lines with potential for therapy
|journal=Nature Biothecnology
|volume=25
|issue=5
|pages=100–106
|year=2007
|pmid=17206138
|doi=10.1038/nbt1274
}}</ref>
All over the world, universities and research institutes are studying [[amniotic fluid]] to discover all the qualities of amniotic stem cells, and scientists such as [[Anthony Atala]]<ref>{{cite web|author=NewsHour with Jim Lehrer |url=http://www.pbs.org/newshour/bb/health/jan-june07/cell_01-08.html |title=Online NewsHour: Update &#124; Amniotic Fluid Yields Stem Cells &#124; January 8, 2007 |publisher=PBS |date= |accessdate=2010-03-14}}</ref><ref>{{cite web|url=http://www.isscr.org/public/briefings/amniotic.htm |title=Public : Stem Cell Briefings |publisher=ISSCR |date=2008-03-21 |accessdate=2010-03-14}}</ref> and [[Giuseppe Simoni]]
<ref>[http://www.ncbi.nlm.nih.gov/pubmed/6131275 National Institute of Healt]</ref><ref>[http://www.thelancet.com/search/results?searchTerm=simoni&fieldName=Authors&year=1983&volume=&page=&journalFromWhichSearchStarted=&sort=date&order=desc&collectionName=Medline (Lancet, 1983)]</ref><ref>{{cite web|url=http://www.smartbrief.com/news/bio/storyDetails.jsp?issueid=10998D4A-47C0-451B-B35A-754969D7EC5A&copyid=876B286F-19F6-4013-95AC-9744F69B7AD2&brief=bio&sb_code=rss&&campaign=rss |title=Biocell picks Massachusetts to house North American headquarters - Related Stories - BIO SmartBrief |publisher=Smartbrief.com |date= |accessdate=2010-03-14}}</ref> have discovered important results.

From an ethical point of view, stem cells from [[amniotic fluid]] can solve a lot of problems, because it is possible to catch amniotic stem cells without destroying embryos. For example, the Vatican newspaper "[[Osservatore Romano]]" called amniotic stem cell "the future of medicine".<ref>{{cite web|url=http://www.catholicnewsagency.com/news/vatican_newspaper_calls_new_stem_cell_source_future_of_medicine/ |title=Vatican newspaper calls new stem cell source 'future of medicine' :: Catholic News Agency (CNA) |publisher=Catholic News Agency |date=2010-02-03 |accessdate=2010-03-14}}</ref>

It is possible to collect amniotic stem cells for donors or for autologuous use: the first US amniotic stem cells bank <ref>{{cite news|url=http://www.reuters.com/article/pressRelease/idUS166682+22-Oct-2009+PRN20091022 |title=European Biotech Company Biocell Center Opens First U.S. Facility for Preservation of Amniotic Stem Cells in Medford, Massachusetts |publisher=Reuters |date=2009-10-22 |accessdate=2010-03-14}}</ref><ref>{{cite news|url=http://www.boston.com/business/ticker/2009/10/europes_biocell.html |title=Europe's Biocell Center opens Medford office - Daily Business Update - The Boston Globe |publisher=Boston.com |date=2009-10-22 |accessdate=2010-03-14}}</ref> opened in 2009 in Medford, MA, by [[Biocell Center]] Corporation <ref>{{cite web|last=Track |first=Inside |url=http://www.bostonherald.com/business/general/view/20091022the_ticker/ |title=The Ticker |publisher=BostonHerald.com |date=2009-10-22 |accessdate=2010-03-14}}</ref><ref>[http://www.masshightech.com/stories/2009/10/19/daily59-Biocell-Center-opens-amniotic-stem-cell-bank-in-Medford.html Biocell opens amniotic stem cell bank]</ref><ref>{{cite web|url=http://www.wbur.org/2009/10/22/stem-cell-bank |title=News » World’s First Amniotic Stem Cell Bank Opens In Medford |publisher=wbur.org |date= |accessdate=2010-03-14}}</ref> and collaborates with various hospitals and universities all over the world.<ref>{{cite web|url=http://www.prnewswire.com/news-releases/biocell-center-corporation-partners-with-new-englands-largest-community-based-hospital-network-to-offer-a-unique-service-in-amniotic-fluid-stem-cell-preservation-86848157.html |title=Biocell Center Corporation Partners with New England's Largest Community-Based Hospital Network to Offer a Unique... - MEDFORD, Mass., March 8 /PRNewswire/ |location=Massachusetts |publisher=Prnewswire.com |date= |accessdate=2010-03-14}}</ref>

==Induced pluripotent==

{{Main|Induced pluripotent stem cell}}

These are not adult stem cells, but rather reprogrammed cells (e.g. epithelial cells) given pluripotent capabilities. Using genetic reprogramming with protein [[transcription factors]], pluripotent stem cells equivalent to [[embryonic stem cells]] have been derived from human adult skin tissue.<ref name="Economist2007_11_22">{{cite news|title=Making human embryonic stem cells|publisher=The Economist|url=http://www.economist.com/science/displaystory.cfm?story_id=10170972|date=2007-11-22}}</ref><ref>{{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}}</ref><ref>{{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}}</ref> [[Shinya Yamanaka]] and his colleagues at [[Kyoto University]] used the transcription factors Oct3/4, Sox2, c-Myc, and Klf4<ref name="Economist2007_11_22"/> in their experiments on cells from human faces. [[Junying Yu]], [[James Thomson (cell biologist)|James Thomson]], and their colleagues at the [[University of Wisconsin–Madison]] used a different set of factors, Oct4, Sox2, Nanog and Lin28,<ref name="Economist2007_11_22"/> 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 [[nuclear transfer]] as an avenue of research.<ref>"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 news|url=http://www.telegraph.co.uk/science/science-news/3314696/Dolly-creator-Prof-Ian-Wilmut-shuns-cloning.html|title=Dolly creator Prof Ian Wilmut shuns cloning|author=Roger Highfield|date=2007-11-16|publisher=[[The Daily Telegraph|The Telegraph]] | location=London}}</ref>

Frozen blood samples can be used as a source of induced pluripotent stem cells, opening a new avenue for obtaining the valued cells.<ref>http://www.newsdaily.com/stories/tre6604si-us-stemcells-frozen/</ref>

==Lineage==
{{Main|Stem cell line}}
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. Progenitors can go through several rounds of cell division before terminally [[cell differentiation|differentiating]] into a mature cell. It is possible that the molecular distinction between symmetric and asymmetric divisions lies in differential segregation of cell membrane proteins (such as [[receptor (biochemistry)|receptors]]) between the daughter cells.<ref>
{{cite journal
|author=Beckmann J, Scheitza S, Wernet P, Fischer JC, Giebel B
|title=Asymmetric cell division within the human hematopoietic stem and progenitor cell compartment: identification of asymmetrically segregating proteins
|journal=Blood
|volume=109
|issue=12
|pages=5494–501
|year=2007
|pmid=17332245
|doi=10.1182/blood-2006-11-055921
}}</ref>

An alternative theory is that stem cells remain undifferentiated due to environmental cues in their particular niche. Stem cells differentiate when they leave that niche or no longer receive those signals. Studies in ''Drosophila'' germarium have identified the signals dpp and adherens junctions that prevent germarium stem cells from differentiating.<ref>
{{cite journal
| author = Xie T, Spradling A
| title = decapentaplegic is essential for the maintenance and division of germline stem cells in the Drosophila ovary
| journal = Cell
| volume = 94
| issue = 2
| pages = 251–60
| year = 1998
| pmid = 9695953
| doi = 10.1016/S0092-8674(00)81424-5
}}</ref><ref>
{{cite journal
| author = Song X, Zhu C, Doan C, Xie T
| title = Germline stem cells anchored by adherens junctions in the Drosophila ovary niches
| journal = Science
| volume = 296
| issue = 5574
| pages = 1855–7
| year = 2002
| pmid = 12052957
| doi=10.1126/science.1069871
}}</ref>

{{Main|Induced Pluripotent Stem Cell}}
The signals that lead to reprogramming of cells to an embryonic-like state are also being investigated. These signal pathways include several [[transcription factor]]s including the [[oncogene]] [[Myc|c-Myc]]. Initial studies indicate that transformation of mice cells with a combination of these anti-differentiation signals can reverse differentiation and may allow adult cells to become pluripotent.<ref name="Takahashi2006" /> However, the need to transform these cells with an oncogene may prevent the use of this approach in therapy.

Challenging the terminal nature of cellular differentiation and the integrity of lineage commitment, it was recently determined that the somatic expression of combined [[transcription factor]]s can directly induce other defined somatic cell fates; researchers identified three neural-lineage-specific transcription factors that could directly convert mouse [[fibroblasts]] (skin cells) into fully functional [[neuron]]s. This "induced neurons" (iN) cell research inspires the researchers to induce other cell types implies that ''all'' cells are [[totipotent]]: with the proper tools, all cells may form all kinds of tissue.<ref>{{cite journal
|title=Direct conversion of fibroblasts to functional neurons by defined factors
|author=Vierbuchen T, Ostermeier A, Pang ZP, Kokubu Y, Südhof TC, Wernig M
|date=2010-02-25
|volume=463
|issue=7284
|pages=1035–41
|journal=Nature
|pmid=20107439
|laysummary=http://www.dailymail.co.uk/health/article-1246591/Scientists-transform-skin-cells-brain-cells-pioneering-study-benefit-sufferers-Alzheimers-Parkinsons.html
|doi=10.1038/nature08797
|pmc=2829121}}</ref>

==Treatments==
{{Main|Stem cell treatments}}

[[File:Stem cell treatments.svg|thumb|330px|Diseases and conditions where stem cell treatment is promising or emerging.<ref>
Diabetes, rheumatoid arthritis, Parkinson's, Alzheimer's disease, osteoarthritis:
*[http://stemcells.nih.gov/info/basics/basics6Stem Cell Basics: What are the potential uses of human stem cells and the obstacles that must be overcome before these potential uses will be realized?]. In Stem Cell Information World Wide Web site. Bethesda, MD: National Institutes of Health, U.S. Department of Health and Human Services, 2009. cited Sunday, April 26, 2009

Stroke and traumatic brain injury repair:
*[http://www.mult-sclerosis.org/news/Dec2000/StemCellDebatePartII.html Stem Cells Tapped to Replenish Organs] thescientist.com, Nov 2000. By Douglas Steinberg

Learning defects:
*[http://www.israel21c.org/health/israeli-scientists-reverse-brain-birth-defects-using-stem-cells ISRAEL21c: Israeli scientists reverse brain birth defects using stem cells] December 25, 2008. (Researchers from the Hebrew University of Jerusalem-Hadassah Medical led by Prof. Joseph Yanai)

Spinal cord injury repair:
*{{cite journal |author=Kang KS, Kim SW, Oh YH, ''et al.'' |title=A 37-year-old spinal cord-injured female patient, transplanted of multipotent stem cells from human UC blood, with improved sensory perception and mobility, both functionally and morphologically: a case study |journal=Cytotherapy |volume=7 |issue=4 |pages=368–73 |year=2005 |pmid=16162459 |doi=10.1080/14653240500238160 |url=}}

Heart infarction:
*{{cite journal |author=Strauer BE, Schannwell CM, Brehm M |title=Therapeutic potentials of stem cells in cardiac diseases |journal=Minerva Cardioangiol |volume=57 |issue=2 |pages=249–67 |year=2009 |month=April |pmid=19274033 |doi= |url=}}

Anti-cancer:
*[http://www.mult-sclerosis.org/news/Dec2000/StemCellDebatePartII.html Stem Cells Tapped to Replenish Organs] thescientist.com, Nov 2000. By Douglas Steinberg

Baldness:
*[http://web.archive.org/web/20080530042215rn_3/www.webmd.com/skin-problems-and-treatments/hair-loss/news/20041104/hair-cloning-nears-reality-as-baldness-cure ''Hair Cloning Nears Reality as Baldness Cure''] [[WebMD]] November 2004

Replace missing teeth:
*{{cite journal |author=Yen AH, Sharpe PT |title=Stem cells and tooth tissue engineering |journal=Cell Tissue Res. |volume=331 |issue=1 |pages=359–72 |year=2008 |month=January |pmid=17938970 |doi=10.1007/s00441-007-0467-6 |url=}}

Repair hearing:
*[http://www.newscientist.com/article/dn7003 Gene therapy is first deafness 'cure' - health - 14 February 2005 - New Scientist]

Restore vision:
*[http://news.bbc.co.uk/1/hi/england/southern_counties/4495419.stm BBC NEWS | England | Southern Counties | Stem cells used to restore vision]

Amyotrophic lateral sclerosis:
*Drs. Gearhart and Kerr of Johns Hopkins University. April 4, 2001 edition of JAMA (Vol. 285, 1691-1693)

Crohn's disease:
*{{cite news | author=Querida Anderson | title= Osiris Trumpets Its Adult Stem Cell Product | url=http://www.genengnews.com/articles/chitem.aspx?aid=2508 | work=[[Genetic Engineering & Biotechnology News]] | publisher=[[Mary Ann Liebert, Inc.]] | page=13 | date=2008-06-15 | accessdate=2008-07-06 | quote=(subtitle) Procymal is being developed in many indications, GvHD being the most advanced }}

Wound healing:
*{{cite journal | doi = 10.1146/annurev.med.58.082405.095329 | last1 = Gurtner | first1 = GC | last2 = Callaghan | first2 = MJ | last3 = Longaker | first3 = MT. | author-separator =, | author-name-separator= | year = 2007 | title = Progress and potential for regenerative medicine | url = | journal = Annu. Rev. Med | volume = 58 | issue = 1| pages = 299–312 | pmid = 17076602 }}
</ref> Bone marrow transplantation is, as of 2009, the only established use of stem cells.]]

Medical researchers believe that stem cell therapy has the potential to dramatically change the treatment of human disease. A number of adult stem cell therapies already exist, particularly [[bone marrow transplant]]s that are used to treat [[leukemia]].<ref>
{{cite journal
|author=Gahrton G, Björkstrand B
|title=Progress in haematopoietic stem cell transplantation for multiple myeloma
|journal=J Intern Med
|volume=248
|issue=3
|pages=185–201
|year=2000
|pmid= 10971785
|doi=10.1046/j.1365-2796.2000.00706.x
}}</ref> In the future, medical researchers anticipate being able to use technologies derived from stem cell research to treat a wider variety of diseases including [[cancer]], [[Parkinson's disease]], [[spinal cord injuries]], [[Amyotrophic lateral sclerosis]], [[multiple sclerosis]], and [[muscle]] damage, amongst a number of other impairments and conditions.<ref>
{{cite journal
|author=Lindvall O
|title=Stem cells for cell therapy in Parkinson's disease
|journal=Pharmacol Res
|volume=47
|issue=4
|pages=279–87
|year=2003
|pmid = 12644384
|doi=10.1016/S1043-6618(03)00037-9
}}</ref><ref>
{{cite journal
|author=Goldman S, Windrem M
|title=Cell replacement therapy in neurological disease
|journal=Philos Trans R Soc Lond B Biol Sci
|volume=361
|issue=1473
|pages=1463–75
|year=2006
|pmid = 16939969
|doi=10.1098/rstb.2006.1886
|pmc=1664668
}}</ref>
However, there still exists a great deal of social and scientific uncertainty surrounding stem cell research, which could possibly be overcome through public debate and future research, and further education of the public.

One concern of treatment is the possible risk that transplanted stem cells could form tumors and have the possibility of becoming cancerous if cell division continues uncontrollably.<ref>
"Stem-cell therapy: Promise and reality." Consumer Reports on Health 17.6 (2005): 8-9. Academic Search Premier. EBSCO. Web. 5 Apr. 2010.</ref>

Stem cells, however, are already studied extensively. While some scientists are hesitant to associate the therapeutic potential of stem cells as the first goal of the research, they find the investigation of stem cells as a goal worthy in itself.<ref>
{{cite news
|author=Wade N
|title=Some Scientists See Shift in Stem Cell Hopes
|publisher=New York Times
|url=http://www.nytimes.com/2006/08/14/washington/14stem.html?_r=1
|date=2006-08-14
|accessdate=2006-12-28
}}</ref>

Contrarily, supporters of embryonic stem cell research argue that such research should be pursued because the resultant treatments could have significant medical potential. It is also noted that excess embryos created for [[in vitro fertilization]] could be donated with consent and used for the research.

The recent development of [[iPS cells]] has been called a bypass of the legal controversy. Laws limiting the destruction of human embryos have been credited for being the reason for development of iPS cells, but it is still not completely clear whether hiPS cells are equivalent to hES cells. Recent work demonstrates hotspots of aberrant epigenomic reprogramming in hiPS cells (Lister, R., et al., 2011).

==Research patents==
The [[patent]]s covering a lot of work on human embryonic stem cells are owned by the [[Wisconsin Alumni Research Foundation]] (WARF). WARF does not charge academics to study human stem cells but does charge commercial users. WARF sold [[Geron Corp.]] exclusive rights to work on human stem cells but later sued Geron Corp. to recover some of the previously sold rights. The two sides agreed that Geron Corp. would keep the rights to only three cell types. In 2001, WARF came under public pressure to widen access to human stem-cell technology.<ref name = "stemcellPatent">Regalado, Antonio, David P. Hamilton (July 2006). [http://www.geneticsandsociety.org/article.php?id=1896 "How a University's Patents May Limit Stem-Cell Researcher."] ''Wall Street Journal''. Retrieved on July 24, 2006.</ref>

A request for reviewing the WARF patents 5,843,780; 6,200,806; 7,029,913 [[US Patent and Trademark Office]] were filed by non-profit patent-watchdogs [http://www.consumerwatchdog.org/ The Foundation for Taxpayer & Consumer Rights], and the [[Public Patent Foundation]] as well as molecular biologist Jeanne Loring of the Burnham Institute. According to them, two of the patents granted to WARF are invalid because they cover a technique published in 1993 for which a patent had already been granted to an Australian researcher. Another part of the challenge states that these techniques, developed by [[James Thomson (cell biologist)|James A. Thomson]], are rendered obvious by a 1990 paper and two textbooks. Based on this challenge, patent 7,029,913 has been rejected in 2010. The two remaining hES WARF patents are due to expire in 2015.

The outcome of this legal challenge is particularly relevant to the Geron Corp. as it can only license patents that are upheld.<ref name="Kintisch">Kintisch, Eli (July 18, 2006) [http://news.sciencemag.org/sciencenow/2006/07/18-02.html "Groups Target Stem Cell Patents."] ''ScienceNOW Daily News''. Retrieved August 15, 2006.</ref>

==Key research events==
*1908 - The term "stem cell" was proposed for scientific use by the [[Russia]]n histologist [[Alexander Maksimov]] (1874–1928) at congress of hematologic society in [[Berlin]]. It postulated existence of haematopoietic stem cells.
* 1960s - [[Joseph Altman]] and Gopal Das present scientific evidence of adult [[neurogenesis]], ongoing stem cell activity in the brain; like [[André Gernez]], their reports contradict [[Santiago Ramón y Cajal|Cajal]]'s "no new neurons" dogma and are largely ignored.
* 1963 - [[Ernest McCulloch|McCulloch]] and [[James Till|Till]] illustrate the presence of self-renewing cells in mouse bone marrow.
* 1968 - [[Bone marrow]] [[Organ transplant|transplant]] between two siblings successfully treats [[Severe combined immunodeficiency|SCID]].
* 1978 - [[Haematopoietic stem cell]]s are discovered in human [[cord blood]].
* 1981 - Mouse [[embryonic stem cell]]s are derived from the [[inner cell mass]] by scientists [[Martin Evans]], [[Matthew Kaufman]], and [[Gail R. Martin]]. Gail Martin is attributed for coining the term "Embryonic Stem Cell".
* 1992 - Neural stem cells are cultured ''[[in vitro]]'' as neurospheres.
* 1997 - Leukemia is shown to originate from a haematopoietic stem cell, the first direct evidence for [[cancer stem cell]]s.
* 1998 - [[James Thomson (cell biologist)|James Thomson]] and coworkers derive the first human embryonic [[stem cell line]] at the [[University of Wisconsin–Madison]].<ref name=pmid9804556>
{{cite journal
| author = Thomson JA, Itskovitz-Eldor J, Shapiro SS, Waknitz MA, Swiergiel JJ, Marshall VS, Jones JM
| title = Embryonic stem cell lines derived from human blastocysts
| journal = Science
| location=New York
| volume = 282
| issue = 5391
| pages = 1145–7
| year = 1998
| month = November
| pmid = 9804556
| doi = 10.1126/science.282.5391.1145
}}</ref>
* 1998 - John Gearhart (Johns Hopkins University) extracted germ cells from fetal gonadal tissue (primordial germ cells) before developing pluripotent stem cell lines from the original extract.
* 2000s - Several reports of [[adult stem cell]] plasticity are published.
* 2001 - Scientists at [[Advanced Cell Technology]] clone first early (four- to six-cell stage) human embryos for the purpose of generating embryonic stem cells.<ref>
{{cite journal
|author=Cibelli JB, Lanza RP, West MD, Ezzell C
|title=The first human cloned embryo
|journal=Scientific American
|month=November
|year=2001
|url=http://www.scientificamerican.com/article.cfm?id=the-first-human-cloned-em
}}</ref>
* 2003 - Dr. Songtao Shi of NIH discovers new source of adult stem cells in children's primary teeth.<ref>{{cite journal
| author=Shostak S
| title=(Re)defining stem cells
| journal=Bioessays
| year=2006
| pages=301–8
| volume=28
| issue=3
| pmid = 16479584
| doi=10.1002/bies.20376
}}</ref>
* 2004–2005 - Korean researcher [[Hwang Woo-Suk]] claims to have created several human [[embryonic stem cell]] lines from unfertilised human [[oocyte]]s. The lines were later shown to be fabricated.
* 2005 - Researchers at [[Kingston University]] in [[England]] claim to have discovered a third category of stem cell, dubbed cord-blood-derived embryonic-like stem cells (CBEs), derived from umbilical cord blood. The group claims these cells are able to differentiate into more types of tissue than adult stem cells.
* 2005 - Researchers at [[UC Irvine]]'s Reeve-Irvine Research Center are able to partially restore the ability of mice with paralyzed spines to walk through the injection of human neural stem cells.
*August 2006 - Mouse [[Induced pluripotent stem cell]]s: the journal [[Cell (journal)|''Cell'']] publishes Kazutoshi Takahashi and [[Shinya Yamanaka]].<ref>
{{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
|month=Aug
|pmid=16904174
|doi=10.1016/j.cell.2006.07.024
}}</ref>
*October 2006 - Scientists at [[Newcastle University]] in England create the first ever artificial liver cells using umbilical cord blood stem cells.<ref>
{{cite web
|url=http://discovermagazine.com/2007/mar/good-news-for-alcoholics
|title=Good news for alcoholics
|publisher=Discover Magazine
|year=2007
|month=March
|accessdate=2010-02-28
}}</ref><ref>
{{cite news
|url=http://news.scotsman.com/health.cfm?id=1608072006
|archiveurl=http://web.archive.org/web/20070203010452/http://news.scotsman.com/health.cfm?id=1608072006
|archivedate=2007-02-03
|publisher=The Scotsman
|location=Edinburgh
|first=Shã‚N
|last=Ross
|title=First liver grown from stem cells offers hope for transplant patients
|date=2006-10-31
}}</ref>
* January 2007 - Scientists at [[Wake Forest University]] led by Dr. [[Anthony Atala]] and [[Harvard University]] report discovery of a new type of stem cell in [[amniotic fluid]].<ref>
{{cite journal
|author=De Coppi P, Bartsch G, Siddiqui MM, ''et al.''
|title=Isolation of amniotic stem cell lines with potential for therapy
|journal=Nat Biotechnol
|volume=25
|issue=1
|pages=100–6
|year=2007
|month=January
|pmid=17206138
|doi=10.1038/nbt1274
|url=http://www.nature.com/nbt/journal/v25/n1/abs/nbt1274.html
}}</ref> This may potentially provide an alternative to embryonic stem cells for use in research and therapy.<ref>{{cite news
|url=http://www.boston.com/news/nation/articles/2007/01/08/easy_stem_cell_source_sparks_interest/
|title=Easy stem-cell source sparks interest: Researchers find amniotic fluid offers advantages
|publisher=Boston Globe
|author=Karen Kaplan
|date=8 January 2007
}}</ref>
*June 2007 - Research reported by three different groups shows that normal skin cells can be reprogrammed to an embryonic state in mice.<ref>
{{cite journal
| author=Cyranoski D
| title=Simple switch turns cells embryonic
| journal=Nature
| year=2007
| pages=618–9
| volume=447
| issue=7145
| pmid = 17554270
| doi = 10.1038/447618a
}}</ref> In the same month, scientist [[Shoukhrat Mitalipov]] reports the first successful creation of a primate stem cell line through [[somatic cell nuclear transfer]]<ref>
{{cite journal
| author=Mitalipov SM, Zhou Q, Byrne JA, Ji WZ, Norgren RB, Wolf DP
| title=Reprogramming following somatic cell nuclear transfer in primates is dependent upon nuclear remodeling
| journal=Hum Reprod
| year=2007
| pages=2232–42
| volume=22
| issue=8
| pmid = 17562675
| doi = 10.1093/humrep/dem136
}}</ref>
*October 2007 - [[Mario Capecchi]], [[Martin Evans]], and [[Oliver Smithies]] win the 2007 [[Nobel Prize for Physiology or Medicine]] for their work on embryonic stem cells from mice using gene targeting strategies producing genetically engineered mice (known as [[knockout mice]]) for gene research.<ref name = "Nobel 2007">
{{cite web
|url = http://nobelprize.org/nobel_prizes/medicine/laureates/2007/index.html
|title = The Nobel prize in physiology or medicine 2007
|accessdate = 8 October 2007
|publisher = Nobelprize.org
}}</ref>
*November 2007 - Human [[induced pluripotent stem cell]]s: Two similar papers released by their respective journals prior to formal publication: in [[Cell (journal)|''Cell'']] by [[Kazutoshi Takahashi]] and [[Shinya Yamanaka]], "Induction of pluripotent stem cells from adult human fibroblasts by defined factors",<ref>{{cite journal
|author=Takahashi K, Tanabe K, Ohnuki M, Narita M, Ichisaka T, Tomoda K, Yamanaka S
|title=Induction of pluripotent stem cells from adult human fibroblasts by defined factors
|journal=Cell
|volume=131
|issue=5
|pages=861–72
|year=2007
|month=November
|pmid=18035408
|doi=10.1016/j.cell.2007.11.019
|url=http://images.cell.com/images/Edimages/Cell/IEPs/3661.pdf
|format=PDF
}}</ref> and in ''Science'' by [[Junying Yu]], et al., from the research group of [[James Thomson (cell biologist)|James Thomson]], "Induced pluripotent stem cell lines derived from human somatic cells":<ref>
{{cite journal
|author=Yu J, Vodyanik MA, Smuga-Otto K, Antosiewicz-Bourget J, Frane JL, Tian S, Nie J, Jonsdottir GA, Ruotti V, Stewart R, Slukvin II, Thomson JA
|title=Induced pluripotent stem cell lines derived from human somatic cells
|journal=[[Science (journal)|Science]]
|volume=318
|issue=5858
|pages=1917–20
|year=2007
|month=December
|pmid=18029452
|doi=10.1126/science.1151526
|url=http://www.sciencemag.org/cgi/content/abstract/1151526
}}</ref> pluripotent stem cells generated from mature human fibroblasts. It is possible now to produce a stem cell from almost any other human cell instead of using embryos as needed previously, albeit the risk of [[tumorigenesis]] due to [[c-myc]] and [[Gene therapy#Retroviruses|retroviral gene transfer]] remains to be determined.
*January 2008 - Robert Lanza and colleagues at Advanced Cell Technology and UCSF create the first human embryonic stem cells without destruction of the embryo<ref>
{{cite journal
|url=http://www.cell.com/cell-stem-cell/abstract/S1934-5909(07)00330-X
|journal=Cell Stem Cell
|author=Chung ''et al.''
|doi=10.1016/j.stem.2007.12.013
|title=Human embryonic stem cell lines generated without embryo destruction
|year=2008
|volume=2
|page=113
|pmid=18371431
|last2=Klimanskaya
|first2=I
|last3=Becker
|first3=S
|last4=Li
|first4=T
|last5=Maserati
|first5=M
|last6=Lu
|first6=SJ
|last7=Zdravkovic
|first7=T
|last8=Ilic
|first8=D
|last9=Genbacev
|first9=O
|issue=2
}}</ref>
*January 2008 - Development of human cloned blastocysts following [[somatic cell nuclear transfer]] with adult fibroblasts<ref>
{{cite journal
|url=http://stemcells.alphamedpress.org/cgi/reprint/2007-0252v1.pdf
|archiveurl=http://web.archive.org/web/20080625032536/http://stemcells.alphamedpress.org/cgi/reprint/2007-0252v1.pdf
|archivedate=2008-06-25
|title=Development of human cloned blastocysts following somatic cell nuclear transfer (SCNT) with adult fibroblasts
|author=French AJ, Adams CA, Anderson LS, Kitchen JR, Hughes MR, Wood SH
|journal=Stem Cells Express
|date=2008-01-17
|doi=10.1634/stemcells.2007-0252
|volume=26
|page=485
|pmid=18202077
|issue=2
}} {{Dead link|date=December 2009}}</ref>
*February 2008 - Generation of pluripotent stem cells from adult mouse liver and stomach: these iPS cells seem to be more similar to embryonic stem cells than the previously developed iPS cells and not tumorigenic, moreover genes that are required for iPS cells do not need to be inserted into specific sites, which encourages the development of non-viral reprogramming techniques.<ref>
{{cite journal
|author=Aoi T, Yae K, Nakagawa M, ''et al.''
|title=Generation of pluripotent stem cells from adult mouse liver and stomach cells
|journal=Science
|volume=321
|issue=5889
|pages=699–702
|year=2008
|month=August
|pmid=18276851
|doi=10.1126/science.1154884
}}</ref>
*March 2008-The first published study of successful cartilage regeneration in the human knee using autologous adult mesenchymal stem cells is published by clinicians from Regenerative Sciences<ref>
{{cite journal
|author=Centeno CJ, Busse D, Kisiday J, Keohan C, Freeman M, Karli D
|title=Increased knee cartilage volume in degenerative joint disease using percutaneously implanted, autologous mesenchymal stem cells
|journal=Pain Physician
|volume=11
|issue=3
|pages=343–53
|year=2008
|pmid=18523506
|url=http://www.painphysicianjournal.com/linkout_vw.php?issn=1533-3159&vol=11&page=343
|issn=1533-3159
}}</ref>
*October 2008 - Sabine Conrad and colleagues at Tübingen, Germany generate [[pluripotent stem cells]] from spermatogonial cells of adult human testis by culturing the cells in vitro under [[leukemia inhibitory factor]] (LIF) supplementation.<ref>
{{cite journal
|author=Conrad S, Renninger M, Hennenlotter J, ''et al.''
|title=Generation of pluripotent stem cells from adult human testis
|journal=Nature
|volume=456
|issue=7220
|pages=344–9
|year=2008
|month=November
|pmid=18849962
|doi=10.1038/nature07404
}}</ref>
*30 October 2008 - Embryonic-like stem cells from a single human hair.<ref>
{{cite journal
|author=Baker M
|title=Embryonic-like stem cells from a single human hair
|journal=Nature Reports Stem Cells
|month=October
|year=2008
|doi=10.1038/stemcells.2008.142
|url=http://www.nature.com/stemcells/2008/0810/081030/full/stemcells.2008.142.html
}}</ref>
*1 March 2009 - Andras Nagy, Keisuke Kaji, ''et al.'' discover a way to produce embryonic-like stem cells from normal adult cells by using a novel "wrapping" procedure to deliver specific genes to adult cells to reprogram them into stem cells without the risks of using a virus to make the change.<ref>
{{cite journal
|journal=Nature
|title=piggyBac transposition reprograms fibroblasts to induced pluripotent stem cells
|author=Woltjen K, Michael IP, Mohseni P, Desai R, Mileikovsky M, Hämäläinen R, Cowling R, Wang W, Liu P, Gertsenstein M, Kaji K, Sung HK, Nagy A
|doi=10.1038/nature07863
|date=2009-03-01
|volume=458
|page=766
|pmid=19252478
|issue=7239
}}</ref><ref>
{{cite web
|url=http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/20090227/stem_cells_090228/20090301?hub=TopStories
|title=Canadians make stem cell breakthrough
|accessdate=March 1, 2009
|date=March 1, 2009
}}</ref><ref>
{{cite news
|agency=Canadian Press
|publisher=Amherst Daily News
|url=http://www.amherstdaily.com/index.cfm?sid=227086&sc=510
|title=Researchers find new method for turning adult cells into stem cells
|date=2009-01-03
|accessdate=2010-02-28
}}</ref> The use of [[electroporation]] is said to allow for the temporary insertion of genes into the cell.<ref>
{{cite news
|author=Ian Sample
|url=http://www.guardian.co.uk/science/2009/mar/01/stem-cells-breakthrough
|title=Scientists' stem cell breakthrough ends ethical dilemma
|publisher=The Guardian
|date=2009-03-01
|accessdate=2009-03-03
| location=London
}}</ref><ref>
{{cite journal
|journal=Nature
|date=2009-03-01
|title=Virus-free induction of pluripotency and subsequent excision of reprogramming factors
|author=Kaji K, Norrby K, Paca A, Mileikovsky M, Mohseni P, Woltjen K
|doi=10.1038/nature07864
|volume=458
|page=771
|pmid=19252477
|issue=7239
|pmc=2667910
}}</ref><ref>{{cite journal|url=http://www3.interscience.wiley.com/journal/121683666/abstract |journal=Stem Cells |year=2009 |volume=27 |issue=5 |pages=1098–1108 |title=Methylguanine DNA methyltransferase-mediated drug resistance-based selective enrichment and engraftment of transplanted stem cells in skeletal muscle |author=Lee ASJ, Kahatapitiya P, Kramer B, Joya JE, Hook J, Liu R, Schevzov G, Alexander IE, McCowage G, Montarras D, Gunning PW, Hardeman EC|doi=10.1002/stem.28|pmid=19415780}}</ref><ref>{{cite news |author=Sample I |title=Scientists' stem cell breakthrough ends ethical dilemma |url=http://www.guardian.co.uk/science/2009/mar/01/stem-cells-breakthrough |date=1 March 2009 |publisher=The Guardian | location=London}}</ref>
*28 May 2009 Kim ''et al.'' announced that they had devised a way to manipulate skin cells to create patient specific "induced pluripotent stem cells" (iPS), claiming it to be the 'ultimate stem cell solution'.<ref>
{{cite journal
|title=Generation of human induced pluripotent stem cells by direct delivery of reprogramming proteins
|author=Kim D, Kim CH, Moon JI, Chung YG, Chang MY, Han BS, Ko S, Yang E, Cha KY, Lanza R, Kim KS
|pmid=19481515
|journal=Cell Stem Cell
|laysummary= http://www.reuters.com/article/idUSN28256624
|date=27 May 2009
|volume=4
|issue=6
|pages=472–6
|doi=10.1016/j.stem.2009.05.005
|pmc=2705327
}} (cited in lay summary, not read)</ref>
*11 October 2010 First trial of embryonic stem cells in humans.<ref>{{cite news| url=http://www.bbc.co.uk/news/health-11517680 | work=BBC News | title=First trial of embryonic stem cells in humans | date=2010-10-11}}</ref>
*25 October 2010 - Ishikawa et ''al.'' write in the Journal of Experimental Medicine that research shows that transplanted cells which contain their new host's nuclear DNA could still be rejected by the invidual's immune system due to foreign [[mitochondrial DNA]]. Tissues made from a person's stem cells could therefore be rejected, because mitochondrial genomes tend to accumulate mutations.<ref>
{{cite journal
|title=The innate immune system in host mice targets cells with allogenic mitochondrial DNA
|author=Ishikawa K, Toyama-Sorimachi N, Nakada K, Morimoto M, Imanishi H, Yoshizaki M, Sasawatari S, Niikura M, Takenaga K, Yonekawa H, Hayashi J
|pmid=20937705
|journal=J Exp Med.
|date=25 October 2010
|volume=207
|issue=11
|pages=2297–305
|doi=10.1084/jem.20092296
|pmc=2964578
}}</ref>

==See also==
*[[Cancer stem cell]]
*[[Stem cell controversy]]
*[[Dental pulp stem cells]]
*[[Human genome]]
*[[Induced Pluripotent Stem Cell]] (iPS Cell)
*[[Meristem]]
*[[Partial cloning]]
*[[Plant stem cells]]
*[[Stem cell marker]]
*[[Stem Cell Network]]

==References==
{{Reflist|colwidth=30em}}

==External links==
{{Commons category|Stem cells}}
<!-- Please use the talk page to propose any additions to this section. If you do not do this, the link will almost certainly be deleted.-->
;General
* [http://stemcells.nih.gov/info/basics/ Stem Cell Basics]
* [http://www.nature.com/stemcells Nature Reports Stem Cells: Introductory material, research advances and debates concerning stem cell research.]
* [http://dels.nas.edu/bls/stemcells/booklet.shtml Understanding Stem Cells: A View of the Science and Issues from the National Academies]
* [http://www.scientificamerican.com/article.cfm?id=the-stem-cell-challenge Scientific American Magazine (June 2004 Issue) The Stem Cell Challenge]
* [http://www.scientificamerican.com/article.cfm?id=stem-cells-the-real-culpr-2006-07 Scientific American Magazine (July 2006 Issue) Stem Cells: The Real Culprits in Cancer?]
* {{sep entry|stem-cells|Ethics of Stem Cell Research|Andrew Siegel}}
* [http://www.nature.com/nbt/journal/v25/n1/abs/nbt1274.html Isolation of amniotic stem cell lines with potential for therapy]
* [http://stemcell.childrenshospital.org Children's Hospital Stem Cell Research]
* [http://stemcelllist.com Stem Cell Research and Industry Directory]
* {{LibGuides|stemcellcloning|Stem Cell Research and Cloning}}
;Peer-reviewed journals
* [http://www.tandf.co.uk/journals/titles/14653249.asp Cytotherapy]
* [http://www.liebertpub.com/products/product.aspx?pid=9 Cloning and Stem Cells]
* [http://www.pubstemcell.com Journal of Stem Cells and Regenerative Medicine]
* [http://www.liebertpub.com/products/product.aspx?pid=125 Stem Cells and Development]
* [http://www.futuremedicine.com/loi/rme Regenerative Medicine]
* [http://www.elsevier.com/wps/find/journaldescription.cws_home/711630/description#description Stem Cell Research]
{{Wound healing}}
{{Stem cells}}
{{embryology}}

{{DEFAULTSORT:Stem Cell}}
[[Category:Stem cells| ]]
[[Category:Biotechnology]]
[[Category:Cell biology]]
[[Category:Developmental biology]]
[[Category:Cloning]]

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[[bs:Matična ćelija]]
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[[da:Stamcelle]]
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[[es:Célula madre]]
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[[he:תא גזע]]
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[[pl:Komórki macierzyste]]
[[pt:Célula-tronco]]
[[ro:Celulă stem]]
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[[simple:Stem cell]]
[[sk:Kmeňová bunka]]
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[[sr:Изворна ћелија]]
[[sh:Matična ćelija]]
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[[ta:குருத்தணு]]
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[[th:สเต็มเซลล์]]
[[tr:Kök hücre]]
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[[ur:خلیہ جذعیہ]]
[[vi:Tế bào gốc]]
[[yi:סטעם צעל]]
[[zh-yue:幹細胞]]
[[bat-smg:Kamėinėnes lāsteles]]
[[zh:幹細胞]]

Revision as of 16:21, 6 May 2011

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