Editing Stem cell (section)

{{short description|Undifferentiated biological cells that can differentiate into specialized cells}}
{{About|the cell type|the medical therapy|stem-cell therapy}}
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{{Infobox embryology
| Name        = Stem cell
| Latin       = cellula praecursoria
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In [[multicellular organisms]], '''stem cells''' are [[Cellular differentiation|undifferentiated]] or partially differentiated [[Cell (biology)|cells]] that can change into various [[types of cells]] and [[Cell proliferation|proliferate]] indefinitely to produce more of the same stem cell. They are the earliest type of cell in a [[cell lineage]].<ref name=":7">{{cite book |last1=Atala |first1=Anthony |last2=Lanza |first2=Robert | name-list-style = vanc |url={{google books|plainurl=y|id=wm-K_dKpjBAC&pg=RA1-PA451}}|title=Handbook of Stem Cells|date=2012|publisher=Academic Press|isbn=978-0-12-385943-3|language=en}}</ref>{{rp||452}} They are found in both [[embryo]]nic and adult organisms, but they have slightly different properties in each. They are usually distinguished from [[progenitor cells]], which cannot divide indefinitely, and [[Precursor cell|precursor]] or blast cells, which are usually committed to differentiating into one cell type.

In [[mammals]], roughly 50 to 150 cells make up the [[inner cell mass]] during the [[blastocyst]] stage of [[embryonic development]], around days 5–14. These have stem-cell capability. ''[[In vivo]]'', they eventually differentiate into all of the body's cell types (making them [[pluripotent]]). This process starts with the differentiation into the three [[germ layers]] – the [[ectoderm]], [[mesoderm]] and [[endoderm]] – at the [[gastrulation]] stage. However, when they are isolated and [[Cell culture|cultured]] ''[[in vitro]]'', they can be kept in the stem-cell stage and are known as [[embryonic stem cells]] (ESCs).

[[Adult stem cells]] are found in a few select locations in the body, known as [[Stem-cell niche|niches]], such as those in the [[bone marrow]] or [[gonads]]. They exist to replenish rapidly lost cell types and are [[multipotent]] or unipotent, meaning they only differentiate into a few cell types or one type of cell. In mammals, they include, among others, [[hematopoietic stem cells]], which replenish blood and immune cells, [[Stratum basale|basal cells]], which maintain the skin [[epithelium]], and [[mesenchymal stem cells]], which maintain bone, [[cartilage]], muscle and fat cells. Adult stem cells are a small minority of cells; they are vastly outnumbered by the progenitor cells and terminally differentiated cells that they differentiate into.<ref name=":7" />{{rp||452}}

Research into stem cells grew out of findings by Canadian biologists [[Ernest McCulloch]], [[James Till]] and Andrew J. Becker at the [[University of Toronto]] and the Ontario Cancer Institute in the 1960s.<ref>{{cite journal |vauthors = 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 = 452–454 |date = February 1963 |pmid = 13970094 |doi = 10.1038/197452a0 |bibcode = 1963Natur.197..452B |hdl-access = free |hdl = 1807/2779 |s2cid = 11106827  |issn = 0028-0836 }}</ref><ref>{{cite journal |vauthors = 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 = 327–336 |date = December 1963 |pmid = 14086156 |doi = 10.1002/jcp.1030620313 |hdl-access = free |hdl = 1807/2778 |s2cid = 43875977 }}</ref> {{As of|2016|}}, the only established [[Stem-cell therapy|medical therapy using stem cells]] is [[hematopoietic stem cell transplantation]],<ref>{{cite journal |vauthors = Müller AM, Huppertz S, Henschler R |title = Hematopoietic Stem Cells in Regenerative Medicine: Astray or on the Path? |journal = Transfusion Medicine and Hemotherapy |volume = 43 |issue = 4 |pages = 247–254 |date = July 2016 |pmid = 27721700 |pmc = 5040947 |doi = 10.1159/000447748 }}</ref> first performed in 1958 by French oncologist [[Georges Mathé]]. Since 1998 however, it has been possible to culture and differentiate human embryonic stem cells (in [[stem-cell lines]]). The process of isolating these cells has been [[Stem cell controversy|controversial]], because it typically results in the destruction of the embryo. Sources for isolating ESCs have been [[Stem cell laws|restricted]] in some European countries and Canada, but others such as the UK and China have promoted the research.<ref name="Pew Intl">{{cite news |last1=Ralston |first1=Michelle |title=Stem Cell Research Around the World |url=https://www.pewforum.org/2008/07/17/stem-cell-research-around-the-world/ |work=Pew Research Center's Religion & Public Life Project |date=17 July 2008 }}</ref> [[Somatic cell nuclear transfer]] is a [[cloning]] method that can be used to create a cloned embryo for the use of its embryonic stem cells in stem cell therapy.<ref>{{cite journal |last1=Tuch |first1=B. E. |title=Stem cells: a clinical update |journal=Australian Family Physician |date=September 2006 |volume=35 |issue=9 |pages=719–721 |url=https://www.racgp.org.au/afp/200609/11021 |id={{ProQuest|216301343}} |pmid=16969445 }}</ref> In 2006, a Japanese team led by [[Shinya Yamanaka]] discovered a method to convert mature body cells back into stem cells. These were termed [[induced pluripotent stem cells]] (iPSCs).<ref name=":6" />