Tissue-specific progenitor cells

Conversely, dedifferentiation of tissue-specific progenitor cells could provide another source of multipotent stem cells, which could then be retasked to other lineages. This would be analogous to the process of tissue regeneration observed in some amphibians. Along these lines, reversine has been identified as a compound that induces dedifferentiation of myoblasts to multipotent... 

Stems cells are also the natural units of embryonic generation and tissue regeneration in adults. The list of tissues that use the model of differentiation from hematopoietic stem cells to progenitor cells to mature cells, now includes both the central and peripheral nervous system and skeletal muscle. Evidence is mounting that many, if not all, organs and tissues contain tissue-specific stem cells. 

Main Characteristics ofSP Cells from Diverse Compartments. A variable number of SP cells have been distributed in the different tissues of the body. The SP cells are a heterogeneous population that possesses the ability to give rise to their lineage-specific progenitor cells [138]. Some of these cells have been analyzed and found to be multipotent [139]. In vitro cultures of SP cells have shown differences in their propagation capacities and quiescent state [140,145,161]. 

Bone consists of three kinds of cells osteoblasts, osteoclasts, and osteocytes. Osteoblasts are derived from mesoderm-specific progenitor cells and synthesize ECM associated with bone. Osteocytes are osteoblasts that become embedded within the bone matrix. Osteoclasts (from hematopoietic lineage) degrade bone matrix using a combination of proteases and are instrumental in resorption of bone and regulation of Ca + balance in serum. The antagonistic activity of osteoblasts and osteoclasts is critical in the remodeling of bone tissue. 

Stem cells are progenitor cells which are not yet specifically formed. They can multiply almost infinitely and form nearly all 210 tissue types in the human being. Depending on their derivation, they are defined as follows .) embryonal (= taken from the inner cell mass of the blastocysts), (2.) foetal (= isolated from 5-9 week-old abortive foetuses, and (5.) adult (= taken from the tissue of adults or children by means of biopsy or from the umbilical cord of newborns. Adult stem cells are limited in number and life span they do, however, have a broader development potential than so far assumed. They have also been found in the liver. The transformation of stem cells from the bone marrow into hepatocytes has been carried out successfully. Liver stem cells (7-15 gm) can develop both primary cell types of the liver, (7.) mature hepatocytes and (2.) biliary epithelial cells. These stem cells are deemed to be genuine liver stem cells, and not merely derived from the activation of immature oval cells in the liver. (54,59, 60, 81) (s. fig. 2.20)... 

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