To gain insight into the mechanisms of an age related difference in ability of wound healing, the characteristics of stem cell differentiation in skins from fetus, child and adult were investiga ted. Integrin ? 1 and keratin 19 (K19) were used as the biochemical markers for stem cells and transit amplifying cells. Biopsies were taken from fetus (22～24week gestational age), children (4～12year) and adults (35～53year). Immunohistochemistry was used. As for the immunostainings of fetal tissue sections, integrin ? 1 and K19 expressions were observed in all epidermal basal cells. In children skin, the ratio of integrin ? 1 and K19 positive cells in the epidermal basal layer was 60%～80%. In adults, the ratio in the epidermal layer decreased. These results indicate that fetal skin epidermis contains a large number of stem cells and transit amplifying cells, and the proportion of stem cells and transit amplifying cells decreases with age after birth, which maybe a reason of the age associated difference in ability of wound healing.

To investigate the different expression of Fas, Fas L and Caspase 3 in hypertrophic scars and normal skins in order to explore their influences on scar formation, the expression intensity and distribution of Fas, Fas L and Caspase 3 were detected by immunohistochemistry and pathological methods in 8 cases of hypertrophic scars and 8 cases of normal skins. In normal skins, Fas and Fas L were mainly located in the cellular membranes and cytoplasms of epidermal cells and some fibroblasts. Caspase 3 was mostly distributed in epidermal basal cells and some fibroblasts. In hypertrophic scars, Fas and Fas L were principally existed in the membranes and cytoplasms of epidermal keratinocytes. The positive cellular ratio of two proteins was significantly reduced ( P

Localization and expression of two subunits (IGF ⅠR? and IGF ⅠR?) of insulin like growth factor Ⅰ receptor and phosphorylated tyrosine proteins (P Tyr) in skins at different developmental stages were studied in order to explore their potential biological significance. Immunohistochemistry and pathological methods were used to detect the expression intensity and distribution of IGF ⅠR?, IGF ⅠR? and P Tyr in skins of 12 fetuses with different gestational ages and 8 adults. The results showed that positive immunohistochemical signals of IGF ⅠR?, IGF ⅠR? and P Tyr could be found in fetal and adult skins. Along with growth and development of the fetus, the positive cell rates of IGF ⅠR?, IGF ⅠR? and P Tyr in skins elevated progressively. In adult skins, IGF ⅠR was mainly located in the cell membrane of epidermal cells, while P Tyr was chiefly distributed in epidermal cells and some fibroblasts. These results suggested that IGF ⅠR and its mediating signaling pathway might be involved in cutaneous development at embryonic stage, in cutaneous structure and function maintenance, and in wound healing at postnatal stage.