Expression of stratum corneum chymotryptic enzyme in relation to other markers of epidermal differentiation in a skin explant model.

The serine proteinase stratum corneum chymotryptic enzyme (SCCE) has been proposed to be involved in the degradation of intercellular cohesive structures in cornified squamous epithelia in the process of desquamation. Since SCCE is expressed late in epidermal differentiation and is found at all sites where there is a formation of cornified epithelia it also serves as a marker for terminal epidermal differentiation. Earlier studies have shown that the link between expression and the formation of cornified cells may be stronger for SCCE than for other well characterized markers of epidermal differentiation. In an attempt to further elucidate the regulation of SCCE expression we have in this study compared the expression of SCCE with the expression of keratin 10, filaggrin and involucrin in an in vitro model with skin explants cultured for various periods of time on de-epidermized dermis at the liquid-air interface. The markers were analysed by means of immunohistochemistry. We found that the expression of SCCE preceded the expression of keratin 10 and filaggrin. In contrast to involucrin, which was expressed by all suprabasal keratinocytes, SCCE was expressed only by high suprabasal cells. Our results indicate that the expression of SCCE may be regulated in a way that differs from the regulation of the expression of keratin 10, filaggrin and involucrin.