title: In vitro assessment of keratinocyte aging.
abstract: In vitro aging models are based on the observation that normal cells in culture have a finite lifespan and eventually cease to proliferate under conditions that initially support excellent growth. Recent assessment of the aging process in keratinocytes, made possible by improved tissue-culture techniques, have confirmed prior findings with fetal and adult fibroblasts and have permitted investigation into the mechanism of in vitro senescence. Early-passage newborn human keratinocytes maintained in a serum-free system were found to proliferate more rapidly than early-passage adult keratinocytes maintained under identical conditions, and they were also found to have far steeper dose-response curves for a potent hypothalamus-derived mitogen keratinocyte growth factor (KGF), as well as for KGF/EGF in combination, with a more than 200-fold increase in cell number, total protein, and colony size over the tested range of concentrations, as opposed to a less than 75-fold increase for adult keratinocytes in these parameters. These results support the hypothesis that the age-associated decrease for keratinocyte proliferation in vitro may be due to progressive loss of mitogenic responsiveness. Unrecognized changes in proliferative rate and growth-factor requirements related to age of the tissue donor may complicate interpretation of studies addressing other aspects of keratinocyte biology.
mesh_terms: D000328:Adult; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival; D004305:Dose-Response Relationship, Drug; D000078404:Epidermal Cells; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology; D006801:Humans; D007231:Infant, Newborn; D008954:Models, Biological
chemical_list: D004815:Epidermal Growth Factor