Stem cell

This article is about the cell type. For the medical therapy, see stem-cell therapy.
"Stem cells" and "Stem cell research" redirect here. For the journals, see Stem Cells (journal) and Stem Cell Research (journal).
Stem cell
Transmission electron micrograph of a mesenchymal stem cell displaying typical ultrastructural characteristics
Details
Identifiers
Latincellula praecursoria
MeSHD013234
THH1.00.01.0.00028, H2.00.01.0.00001
FMA63368
Anatomical terminology

In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell in a cell lineage.[1] They are found in both embryonic and adult organisms, but they have slightly different properties in each. They are usually distinguished from progenitor cells, which cannot divide indefinitely, and 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 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 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, 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.[1]

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.[2][3] As of 2016, the only established medical therapy using stem cells is hematopoietic stem cell transplantation,[4] 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 controversial, because it typically results in the destruction of the embryo. Sources for isolating ESCs have been restricted in some European countries and Canada, but others such as the UK and China have promoted the research.[5] 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.[6] 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).[7]

  1. ^ a b Atala A, Lanza R (2012). Handbook of Stem Cells. Academic Press. p. 452. ISBN 978-0-12-385943-3.
  2. ^ Becker AJ, McCulloch EA, Till JE (February 1963). "Cytological demonstration of the clonal nature of spleen colonies derived from transplanted mouse marrow cells". Nature. 197 (4866): 452–454. Bibcode:1963Natur.197..452B. doi:10.1038/197452a0. hdl:1807/2779. ISSN 0028-0836. PMID 13970094. S2CID 11106827.
  3. ^ Siminovitch L, McCulloch EA, Till JE (December 1963). "The distribution of colony-forming cells among spleen colonies". Journal of Cellular and Comparative Physiology. 62 (3): 327–336. doi:10.1002/jcp.1030620313. hdl:1807/2778. PMID 14086156. S2CID 43875977.
  4. ^ Müller AM, Huppertz S, Henschler R (July 2016). "Hematopoietic Stem Cells in Regenerative Medicine: Astray or on the Path?". Transfusion Medicine and Hemotherapy. 43 (4): 247–254. doi:10.1159/000447748. PMC 5040947. PMID 27721700.
  5. ^ Ralston, Michelle (17 July 2008). "Stem Cell Research Around the World". Pew Research Center's Religion & Public Life Project.
  6. ^ Tuch, B. E. (September 2006). "Stem cells: a clinical update". Australian Family Physician. 35 (9): 719–721. PMID 16969445. ProQuest 216301343.
  7. ^ Cite error: The named reference :6 was invoked but never defined (see the help page).