Expression of epidermal integrins in human organotypic keratinocyte cultures

Abstract In organotypic coculture of human epidermal keralinocyles (HEK) or follicular outer root sheath (ORS) cells with human dermal fibroblasts, a stratified epithelium develops which in many regards re-sembles inleifollicular epidermis. The epithelium growing on type I collagen gels in the absence of a preformed basement membrane itself produces only low or moderate amounts of laminin and collagen type IV, so that a well-structured basement membrane cannot be formed. This results in loose and insufficient anchoring of basal cells in the collagen gel, frequently leading to cleft formation at the junction. Because integrins are important receptors for cell-cell and cell-matrix adhesion of keratino-cytes which under certain circumstances may also influence epidermal differentiation, we studied their expression under this culture condition which provides adhesional stress but leaves epidermal differentiation largely unaltered. The localization of integrins differed markedly from that in normal epidermis or normal outer root sheath since all integrin chains were polarized to the epithelium-collagen I interface. Thus, not only the 7.6 and β4-chains showed preferential expression at the basal attachment site of keratinocytes as in normal epidermis, but also the α2-, α3-, βM-chains which in normal epidermis under “steady stale” conditions appeal-primarily involved in cell-cell interaction of keralinocytes and are preferen-tially expressed at the lateral sides of their plasma membranes. Interest-ingly, the altered expression of integrins in organotypic cultures is not accompanied by significant disturbances in terminal differentiation.