Regenerative Medicine (2003) / Chapter Skim
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4 Stem cells of the skin epitheliulm
4 Stem cells of the skin epitheliulm
Pages 14-19
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From page 14... ...
In mouse skin, as measured by autoradiography, the entire differentiation process from basal layer to squame takes 10-14 days (4~. Human epidermis turns over more slowly; however, the proliferative reserve of human skin epithelial stem cells, which supply sufficient progeny to maintain 1-2 m2 of skin for decades, must be enormous.
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From page 15... ...
Hair cycling, the repeated regeneration of hair follicles to produce new hair shafts over the lifetime of the organism, is a useful model by which to study stem cell properties. According to the "bulge activation hypothesis," bulge stem cells are stimulated to divide and produce a new germinative hair matrix only after receiving signals from specialized hair follicle mesenchymal cells (12~.
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From page 16... ...
1 - 1\ Label retaining keratinocytes in the bulge l Hair follicle matrix Functional Characteristics of Skin Epithelial Stem Cells Locating the putative epidermal stem cells represents a major advance in the field, allowing scientists to move forward with respect to the biochemical and functional characteristics of this important population of cells. Other stem cell fields, such as the hematopoietic system, are replete with cell surface markers that identify nearly every cell type, starting with stem cells and extending through the most differentiated forms of the progeny types.
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From page 17... ...
Interestingly, overexpression of c-myc in transgenic mouse skin results in what appears to be depletion of the multipotent skin stem cells of the bulge, as judged by a reduction in LRCs and impaired wound healing (34, 35~. Surprisingly, increasing c-myc expression also seems to cause a cell fate change from hair follicle progenitor cells to sebum-producing cells, suggesting that c-myc levels may influence not only the decision of stem cell daughters to become transit-amplifying cells, but also the decision of which lineage to adopt.
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From page 18... ...
Although neither study included grafting back onto the original human being suffering from skin disease, these efforts represent a major advance toward the possibility of manipulating stem cells to treat human disease. Conclusions The search for the biochemical regulators of skin epithelial stem cell self-renewal and production of daughter cells that will populate one or several lineages of the epidermis is ongoing.
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From page 19... ...
25. Raghavan, S., Bauer, C., Mundschau, G., Li, Q
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