EVIDENCE OF INCREASED KERATINOCYTE PROLIFERATION IN AIR-LIQUID INTERFACE CULTURES OF NONBULLOUS CONGENITAL ICHTHYOSIFORM ERYTHRODERMA

Modern pharmacological and dermatological research requires the use of appropriate in vitro models which permit a faithful reproduction of v arious aspects of the in situ situation. The air-exposed culture of ke ratinocytes on dead de-epidermized dermis is one of the best models of in vitro epidermal differentiation known at the moment. In this study , we verified the model's validity for the reproduction of a hyperprol iferative genodermatosis: non-bullous congenital ichthyosiform erythro derma. We used subcultured epidermal keratinocytes originating from no rmal and ichthyotic patients. Light and electron microscopy of patholo gical cultures disclosed, on day 14, a terminally differentiated epide rmis with a marked granular layer and hyperkeratosis which, however, w as not dramatically different from the normal controls. On day 25, the normal cultures displayed an even more pronounced hyperkeratosis and hypergranulosis, whereas the reconstructed epidermis of pathological o rigin presented a considerable reduction of the viable non-keratinized compartment and a focal parakeratosis. Indirect immunofluorescence re vealed the expression of several differentiation markers which were no t observed in the immersed culture models (e.g. the desmosome- and dif ferentiation-related antigens KM48 and G36-19). Abundant keratohyalin granules were stained with AKH1 antibody and observed even in the deep epidermal layers, but no profilaggrin-filaggrin conversion could be d etected biochemically. The cultures displayed some hyperproliferative features, as judged by KL1 and anti-involucrin antibody stainings. The keratinocyte proliferation was estimated by three different methods: 1) the rate of bromodeoxyuridine incorporation, 2) the expression of p roliferating cell nuclear antigen and 3) the argyrophilic nucleolar or ganizer region counts. It proved to be more elevated in additional str iking and statistically significant difference was observed all cultur es when compared to the normal skin biopsies. An additional striking a nd statistically significant difference was observed between the norma l and ichthyotic cultures on day 14 but was no longer detected after 2 5 days of culture. Our findings demonstrate that keratinocyte hyperpro liferation, a major marker of the ichthyotic epidermis, is maintained in vitro in the emerged culture conditions, even though this model sho ws a baseline tendency for hyperproliferation.