Proliferation and differentiation of cultured epidermal cells from patients with X-linked ichthyosis and ichthyosis vulgaris.

The growth, differentiation, and regeneration of epidermal cultures from patients with X-linked and autosomal dominant ichthyosis and normal individuals were compared. Cell proliferation was studied by combining the technique of fluorescence-activated cell sorting with [3H]thymidine labelling and autoradiography. As in normal epidermal cultures, a marked heterogeneity in the labelling intensity of S-phase cells was observed in the ichthyotic cultures with totally unlabelled as well as very strongly labelled cells. However, in contrast to normal cultures, by far the largest proportion of S-phase cells in the ichthyotic cultures were very strongly labelled with a corresponding, severe reduction in the proportion of un- and weakly labelled cells. The increased labelling intensity of S-phase cells was observed in primary as well as in regenerating cultures, although it was most pronounced in the latter case. There was no difference between cultures from the two types of ichthyotic skin. The morphologic differentiation in the cultures was assessed by measurement of mean diameter of sorted S-phase cells and by quantitation of cornified envelop formation. Both parameters were reduced in the ichthyotic cultures, compared with normal ones. Taken together, these findings are indicative of a hyperproliferative state in the ichthyotic cultures.