22-05-2017, 12:16 PM
27-05-2017, 02:15 PM
Stem cells are undifferentiated biological cells that can differentiate into specialized cells and can be divided (through mitosis) to produce more stem cells. They are found in multicellular organisms. In mammals, there are two broad types of stem cells: embryonic stem cells, which are isolated from the internal cell mass of blastocysts, and adult stem cells, found in various tissues. In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing adult tissues. In a developing embryo, stem cells can be differentiated into all specialized cells: ectoderm, endoderm and mesoderm (see induced pluripotent stem cells), but also maintain the normal volume of regenerative organs such as blood, skin or tissues Intestinal diseases.
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There are three known sources of adult autologous stem cells in humans:
1. Bone marrow, which requires harvesting, ie, perforation in the bone (typically the femur or iliac crest).
2. Adipose tissue (lipid cells), which requires extraction by liposuction.
3. Blood, which requires extraction through apheresis, in which blood is drawn from the donor (similar to a donation of blood) and passed through a machine that extracts the stem cells and returns other portions of the blood to the donor .
Stem cells can also be taken from umbilical cord blood just after birth. Of all stem cell types, autologous collection involves the lowest risk. By definition, autologous cells are obtained from the body itself, just as one can deposit his own blood for elective surgical procedures.
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Adult stem cells are often used in various medical therapies (eg, bone marrow transplantation). Stem cells can now be artificially cultured and transformed (differentiated) into specialized cell types with characteristics compatible with cells from various tissues, such as muscles or nerves. Embryonic cell lines and autologous embryonic stem cells generated by somatic cell transfer or dedifferentiation have also been proposed as promising candidates for future therapies. Stem cell research emerged from the findings of Ernest A. McCulloch and James E. Till at the University of Toronto in the 1960s.