ANTI-FAS INDUCES APOPTOSIS AND PROLIFERATION IN HUMAN DERMAL FIBROBLASTS - DIFFERENCES BETWEEN FORESKIN AND ADULT FIBROBLASTS

Apoptosis, or programmed cell death, is a naturally occurring process mediated by extracellular signals. We studied anti-fas (CD95/Apo-1) an tibody-induced apoptosis in cultured human foreskin and adult dermal f ibroblasts. induction of apoptosis was identified by fluorescence in s itu DNA end-labeling. Anti-Fas antibody induced apoptosis in fibroblas ts in a dose-and time-dependent manner. Adult dermal skin fibroblasts were more susceptible to anti-fas antibody-induced apoptosis than fore skin fibroblasts, with 21-52% dead cells in different strains. in fore skin fibroblasts, anti-fas antibody (1.0 mu g/ml) predominantly induce d proliferation ([H-3]thymidine incorporation increased tcr 115-165% o f control level) and only low levels of apoptotic cell death after 48 hours of treatment. No induction of proliferation by anti-fas was foun d in the adult fibroblasts. Addition of tumor necrosis factor-alpha (T NF-alpha) slightly augmented the anti-fas antibody-induced apoptosis i n both cell types. When we examined the levels of Fas expression using flow cytometry, we found two-to threefold higher Fas expression in ad ult fibroblasts. C6-ceramide treatment, which induces Fas-independent apoptosis, gave similar levels of cell death in both foreskin and adul t fibroblasts. No proliferation was observed in C6-ceramide-treated fi broblasts. Thus, this difference in apoptosis between adult dermal and foreskin fibroblasts appears to be related to the level of Fas expres sion. When clones of foreskin fibroblasts were examined, there was het erogeneity of anti-fas antibody-induced apoptosis and proliferation in the cloned fibroblast subpopulations, brit this was not correlated wi th differences in Fas expression. Alterations in fibroblast population s during the process of differentiation and aging may result from sele ctive loss of apoptosis-susceptible populations. (C) 1998 Wiley-Liss, Inc.