What are Stem Cells ?

Stem Cells are one of the most exciting discoveries in biology. All humans start out as only one cell. This cell is called a zygote, or a fertilized egg. The zygote divides into two cells, then four cells, and so on. Eventually, the cells begin to differentiate, taking on a certain function in a part of the body. This process is called differentiation.

Stem cells are cells that haven’t differentiated yet

They are cells which are distinguished from other cell types by three important characteristics:

First,
“Stem Cells are capable of dividing & renewing themselves for long periods”

  • Stem Cells are capable of dividing symmetrically to expand their number & renewing themselves for long periods without limit to replenish other cells as long as the person or animal is still alive. While, other cells in the body can only replicate a limited number of times before they begin to break down
  • They are able to make an indefinite number of copies of themselves, sometimes after long periods of inactivity.
  • When a stem cell divides, it can either remain a stem cell or turn into a differentiated cell, such as a muscle cell or a red blood cell.

Second,
“Stem Cells are undifferentiated or unspecialized”

  • Most cells in the body are differentiated cells. These cells can only serve a specific purpose in a particular organ. For example, red blood cells are specifically designed to carry oxygen through the blood.
  • One of the fundamental properties of a stem cells is they are undifferentiated or “blank,” cells (non-specialized) that it does not have any tissue-specific structures that allow it to perform specialized function.

Thirdly,
“Can give rise to specialized cells (differentiated cells) when required to do so”

When a stem cell divides, each new cell has the potential either to remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell. This remarkable potential to develop into many different cell types in the body is happening; 

  • During early life and growth.
  • they serve as a sort of internal repair system, dividing essentially without limit to replenish other cells as long as the creature is still alive like renewing our gut lining layer every few days, our skin every few weeks , our liver every 300 days.
  • It is responsible to replace worn out or damaged tissues like the gut, skin & bone marrow. This capability is not the same with all tissue types for e.g,  organs such as the pancreas and the heart, stem cell only divides under special conditions to self-renew

Under these certain physiologic or experimental conditions, they can be induced to become tissue-or organ-specific cells with special functions, those we call them Induced Pluripotent Stem Cells (iPSCSs).

History of Stem Cells

In fact, adult hematopoietic, or blood-forming stem cell, stem cells from bone marrow have been used in transplant for more than 40 years. The history of research of adult stem cells began more than 60 years ago. In the 1950s, researchers discovered that the bone marrow contain at least two kinds of stem cells. One population, called Hematopoietic Stem Cells, forms all the types of blood cells in the body. A second population, called bone marrow stromal stem cells (also called Mesenchymal Stem Cells, or skeletal stem cells by some), were discovered a few years later. In the 1960s, scientists who were studying rats discovered two regions of the brain that containing dividing cells that ultimately become nerve cells. Despite these reports, most scientists believed that the adult brain not generate new nerve cells. It was not until the 1990s, that scientists agreed that the adult brain does contain stem cells that are able to generate the brain’s three major cell types, which are non-neuronal cells, neurons, or nerve cells. 

1961: Till & McCulloch establish the foundation for stem cell science

1963Discovery of renewing cells in bone marrow

1969: First bone marrow transplant between siblings

1970: Bone marrow transplant for Leukemia

1998: Researcher Extract the first stem cells from human embryos

1992: Adult stem cells identified in human brain.

1999: First successful human transplant of insulin-making cells from cadavers

2001: Researchers at the University of California, Los Angeles, described the isolation for a new population of adult stem cells from liposuctioned Adipose tissues

2001: President Bush restricts federal funding for embryonic stem-cell research

2002: Juvenile Diabetes Research Foundation International creates $20 million fund-raising effort to support stem-cell research

2002: California Validate and Legalizes Stem Cell Research

2004: Harvard researchers grow stem cells from embryos using private funding

2006Discovery of induced pluripotent stem cells  (I PSCs) (Nobel Prize)

2009: President Obama Reverses George W. Bush’s 2001 Executive Order and FDA approves Geron Corp. to test stem cells on 8-10 patients with spinal cord injuries

2010: First human injected with stem cells from Geron Corp. clinical trials

2011: Pope hails potential of adult stem cell research

2011: Embryonic stem cells from adult stem cells (Insulin producing B cells generated from skin cells)

18th. Jan.2018: Gladstone Institute, USA, GRISPR Activation of single Genes Turns SKIN CELLS to STEM CELLS.

Read More-References: 

  1. Lajtha L. Stem cells concepts. Differentiation. 1979;14(1-2):23-34. Click here for PDF
  2. Liu G., Chen X. (2018) Isolating and Characterizing Adipose-Derived Stem Cells. In: Singh S., Rameshwar P. (eds) Somatic Stem Cells. Methods in Molecular Biology, vol 1842. Humana Press, New York, NY . Click here for PDF
  3. McCulloch EA, Till JE. Perspectives on the properties of stem cells. Nat Med. 2005; 11(10): 1026-8. Click here for PDF
  4. Sandro Eridani, Stem Cell Applications: An Overview. Eds; Melvin A. Shiffman, Alberto Di Giuseppe, Franco Bassetto.Stem Cells in Aesthetic Procedures: Art, Science, and Clinical Techniques, Springer-Verlag Berlin Heidelberg 2014, p.3-15 
  5. Nowacki M, Kloskowski T, Pietkun K, et al. The use of stem cells in aesthetic dermatology and plastic surgery procedures. A compact review of experimental and clinical applications. Advances in Dermatology and Allergology/Postȩpy Dermatologii i Alergologii. 2017;34(6):526-534. . Click here for PDF
  6. Stoltz J-F, de Isla N, Li YP, et al. Stem Cells and Regenerative Medicine: Myth or Reality of the 21th Century. Stem Cells International. 2015;2015:734731.  Click here for PDF
  7. Zuk PA (2010) The adipose-derived stem cell: looking back and looking ahead. Mol Biol Cell 21(11):1783–1787. Click here for PDF
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