CYCLOSPORINE-A AFFECTS THE ORGANIZATION OF CYTOSKELETON OF NORMAL HUMAN KERATINOCYTES IN CULTURE

Cyclosporin-A (CsA) is a potent immunoregulatory molecule which has be en widely used in many immunomediated and inflammatory skin diseases. It inhibits the proliferation of keratinocytes, but its possible effec ts(s) on cell differentiation are poorly known. To address this issue, we have studied the influence of CsA on the assembly of intermediate filaments by normal human keratinocytes in culture. Control keratinocy tes were flat; the cells which had not reached confluence stained inte nsely for vimentin and weakly for cytokeratins; confluent cells staine d with intermediate intensity for both types of proteins and the cells adhering on the top of others, interpreted as the best differentiated ones, stained for cytokeratins but not for vimentin. CsA (1.6 mu ug/m l for 10 days) inhibited the growth of keratinocytes, which never reac hed confluence; most cells appeared small and roundish, only some stai ned for cytokeratins and few for vimentin. By electron microscopy, a w ell organized meshwork of tonofibrils was recognized in many control k eratinocytes, but never in CsA-treated keratinocytes. We propose that the cytoskeleton could be a target of CsA and that its alteration medi ates other effects of CsA on keratinocytes, including those on cell gr owth.