Types of stem cells


  29 Jun, 2018     evelyn Share on:

Types of Stem Cells

Stem cells are undifferentiated cells with the ability to divide for long periods. They have two main characteristics 1) they can self-renew, producing more stem cells and 2) they can differentiate, that is, they can potentially turn into a variety of cell types, in response to environmental signals.

Stem cells can be classified based on their potency, the ability to differentiate into one or more tissues. Under normal physiological conditions, a totipotent cell can turn into ANY type of cell of the human body; a totipotent cell can be found only in the very earliest stage of life (zygote). A pluripotent cell is the one able to produce all types of cells of the body, but unable to differentiate into extra-embryonic cells (for example, placenta cells). Multipotent cells are limited to generate cells of a certain type of tissue and, unipotent cells are those restricted to turn into a single cell type.

Another classification for stem cells can be done on the basis of their source:

Embryonic Stem Cells (ESCs)

ESCs are pluripotent stem cells derived from a cell mass called the blastocyst, formed 3 to 5 days after an egg is fertilized. As shown in the picture below, ESCs derive from the Inner Cell Mass which can specialize into any non-embryonic tissue of the body.

For research purposes, ESCs are obtained from the inner cell mass of in-vitro fertilized eggs donated for that purpose.

  • Somatic or Adult Stem Cells (ASCs)

ASCs are multipotent cells, originated from different tissues. Their principal function is to replenish damaged or dead tissue. Therefore, ASCs can be found almost in every tissue of the human body, throughout the majority of our lifetime. Common ASCs sources are the umbilical cord, bone marrow, muscle, brain, fat tissue, skin, gut, blood, spinal cord, dental pulp, cornea, etc. A big limitation of this type of cells is that they are scarce and in some cases difficult to obtain.

There are different types of adult stem cells:

  • Hematopoietic Stem Cells (Blood Stem Cells)
  • Mesenchymal Stem Cells
  • Neural Stem Cells
  • Epithelial Stem Cells
  • Skin Stem Cells

ASCs have been used broadly in clinical research to evaluate their effect in the treatment of a broad range of human pathologies.

  • Induced Pluripotent Stem cells (iPSCs)

This classification was added recently since iPSCs were discovered in 2007. iPSCs are pluripotent cells created in the laboratory. To obtain them, differentiated cells (tissue-specific cells, like skin cells) are engineered to behave like an ESC.

References

  • Singh VK, Saini A, Kalsan M, Kumar N, Chandra R. Describing the Stem Cell Potency: The Various Methods of Functional Assessment and In silico Frontiers in Cell and Developmental Biology. 2016;4:134. doi:10.3389/fcell.2016.00134.
  • International Society For Stem Cell Research. InA closer look at Stem Cells [[World Wide Web site] International Society For Stem Cell Research, 2015 [cited June 27, 2018] Available at <http://www.closerlookatstemcells.org/learn-about-stem-cells/types-of-stem-cells>.
  • Nature Reports Stem Cells In What are major types of stem cells? [World Wide Web site]. Macmillan Publishers Limited, part of Springer Nature, 2018 [cited June 27, 2018] Available at <https://www.nature.com/stemcells/2007/0706/070614/full/stemcells.2007.14.html>.
  • NIH Stem Cell Information Home Page. InStem Cell Information [World Wide Web site]. Bethesda, MD: National Institutes of Health, U.S. Department of Health and Human Services, 2016 [cited June 27, 2018] Available at < //stemcells.nih.gov/info/basics/2.htm>.
  • NIH Stem Cell Information Home Page. In Stem Cell Information[World Wide Web site]. Bethesda, MD: National Institutes of Health, U.S. Department of Health and Human Services, 2016 [cited June 27, 2018] Available at < //stemcells.nih.gov/info/2001report/chapter4.htm>.
  • University of Nebraska Medical Center. In Stem Cells [World Wide Web site]. Omaha, NE: University of Nebraska Medical Center, 2018 [cited June 27, 2018] Available at <https://www.unmc.edu/stemcells/educational-resources/types.html>.

 

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