Stem cells are a very vast topic that is the centre of the development of the whole organism. As cells are the basic functional and structural unit of life so the stem cells have the power of regeneration and can give rise to an organ or organism.
These are the differentiated cells that can give rise to any mature cell type.
Stem cells generally possess following characteristics:
Auto-renewal – They can divide themselves and go through various cell divisions and make a copy of these cells.
Potency – the capacity to differentiate into specialized stem cells. Cell potency is of various types:
Totipotent: These are also called omnipotent stem cells. These cells can develop a new organism and can give rise to both the placenta and embryo. These are found in early cells of the embryonic stage.
Pluripotent: These cells are formed from any of the three germ layers i.e., Ectoderm, Endoderm, and Mesoderm. These can give rise to all cells of the body except the placenta. These are found in the inner cell mass of the blastocyst.
Multipotent: These cells can differentiate into a few types of cells and can be seen in several tissues.
Unipotent: These cells can give rise to only one kind of cell.
These cells can be used in various aspects and in treating major dreadful diseases through which all over the world is a big issue. As the research is going on by the scientist for Parkinson’s disease so they could use stem cells to replenish the brain tissue. They are also used for many other diseases like Alzheimer’s, leukaemia, sickle cell anaemia, and many other immunodeficiency problems.
1> 1860-1960: First inferred from analysis of embryo development and microscopy of bone marrow.
2> 1948-58: Stem cell mechanism deduced for sperm development and intestinal epithelium replacement.
3> 1956: First bone marrow transplants performed in human patients.
4> 1958: Nuclei from adult frog cells reprogrammed to full embryonic after transform into frog eggs
5> 1959: Experiments in mice prove the existence of resident blood stem cells in the marrow.
6> 1968: First allogenic human marrow transplant achieved avoiding lethal rejection reactions.
7> 1978: Transplantable stem cells are discovered in human cord blood.
8> 1981: Embryonic stem cells are first derived from the inner cell mass of mouse blastocyst.
9> 1984: Blood stem cells measured by colony formation in vivo are first extensively purified.
10> 1982-1986: First methodology developed for targeted genetic modification in embryonic stem cells.
11> 1992: Neural stem cells identified in the adult brain.
12> 1997: First artificial animal clone (DOLLY sheep).
13> 1998: First human embryonic stem cell is derived.
14> 2000: Formation of beating heart from stem cells outside the human body.
15> 2005: Artificial cloning of human embryonic stem cells.
16> 2006: Reprogramming of adult stem cells by Shinya Yamanaka leading to the formation of induced pluripotent stem cells.
17> 2010: An individual with spinal injury was the first to get treated from human embryonic stem cells as a part of a research trial.
18> 2012: John Gurdon and Yamanaka win the Nobel prize for the discovery of reprogrammed induced pluripotent stem cells.
TYPES OF STEM CELLS
Embryonic stem cells – These stem cells are found in the early stage of the embryo in the inner cell mass of the blastocyst and these are pluripotent cells and can help in the formation of any cell type in the body. For example – zygote
Adult stem cells – These are called tissue-specific stem cells as these are multipotent, they can only differentiate into some cell types in which they are found like if they are found in blood cells, they will produce more no of blood cells. These are most helpful in the repairment and regeneration of body tissues that get damaged. For example, blood-forming or hematopoietic stem cells in the bone marrow.
Induced Pluripotent stem cells (iPSCs) – These are reprogrammed stem cells prepared by scientists in the laboratory and behave like embryonic stem cells. They are also pluripotent and can differentiate into any cell of the body. These are very useful in the treatment of many disorders. For example, skin cells.