EXPRESSION OF STRATUM-CORNEUM CHYMOTRYPTIC ENZYME IN RECONSTRUCTED HUMAN EPIDERMIS AND ITS SUPPRESSION BY RETINOIC ACID

The aim of the present study was to investigate the presence of stratu m corneum chymotryptic enzyme (SCCE) in human epidermis reconstructed in vitro on dead de-epidermized dermis and the effect of retinoic acid (RA) on its expression. SCCE is a recently discovered serine proteina se which has been purified from human stratum corneum, and evidence ha s been presented that it may play a role in stratum corneum turnover, especially in desquamation. The SCCE-specific monoclonal antibody TE-9 B showed positive immunofluorescence staining of high suprabasal kerat inocytes, mainly in the stratum granulosum, in normal non-palmo-planta r human epidermis as well as in reconstructed epidermis in the absence of RA. This staining was also seen in reconstructed epidermis culture d in the presence of 10(-8) M RA, a concentration at which the reconst ructed epidermis still formed an orthokeratotic stratum corneum. At 10 (-7) M RA, however, not only the formation of the stratum corneum but also SCCE expression was suppressed. These results support the hypothe sis that SCCE expression is related to and may be part of the epidermi s-specific differentiation program, where the enzyme may be involved i n the homeostasis of the stratum corneum, possibly by degrading the in tercorneocyte cohesive structures.