WIRKUNGEN VON RETINOIDEN AUF PROLIFERATION UND DIFFERENZIERUNG HUMANER TALGDRUSENZELLEN IN EINEM IN-VITRO MODELL

The effects of different retinoids on the proliferation and differentiation of human sebocytes in vitro were investigated using a model for cultivation of human sebocytes established in our laboratory. The anti-proliferative effects of 13-cis-retinoic acid (cRA), all-trans-retinoic acid (tRA) and acitretin (Ac) on proliferating sebocytes were examined in concentrations of 10^-8-10^-5 M after 7 days of treatment. Cell proliferation was assessed by cell counting and by determination of ³H-thymidine uptake in the DNA. The effects on cell differentiation of confluent sebocyte cultures were evaluated by determining lipid synthesis and antigenic expression after 7 days of treatment. Lipid synthesis was analysed by thin layer chromatography and scintillation counting of ³H-acetate-labeled organic extracts. Antigenic expression was evaluated by cell labeling with monoclonal antibodies using the APAAP technique and by one dimensional gel electrophoresis of cellular proteins. cRA and tRA presented a dose-dependent antiproliferative effect with cRA exerting the strongest effects. The cRA-IC₅₀ was 10^-5 M (p < 0.05 at 10^-8 M). No tRA-IC₅₀ could be achieved at the concentrations tested (p < 0.05 at 10^-6 M). Ac inhibited sebocyte proliferation at 10^-5 M only. All three retinoids tested inhibited lipid synthesis (28%-48%), mainly by decreasing the amount of triglycerides and of wax esters/stearyl esters. cRA presented the strongest inhibitory effects on lipid synthesis of human sebocytes in vitro. Evidence for dedifferentiation of sebocytes occured under retinoid treatment. cRA and tRA decreased sebocyte labeling with the keratin-specific monoclonal antibodies PKK2 and CK8. 12 and all retinoids decreased labeling with OM-I (differentiated sebocytes) and 29F12 (involucrin), whereas cRA alone increased labeling with 24F10 (basic polypeptides). Moreover, quantitative alterations in keratin expression were detected under the retinoids tested. Keratin 5 was down-regulated but keratin I7 was up-regulated by all three retinoids, whereas cRA and tRA down-regulated keratins 6 and 16.