Stratum corneum lipids: specificity, role, deficiencies and modulation

Lipids are important constituents of the human epidermis. Either free and organized into broad lipid bilayers in the intercorneocytes spaces, or covalently bound to the corneocyte envelope, they play a crucial role in permeability barrier function. This article presents the structures of various human skin ceramides, their role in the maintenance of skin barrier function and homeostasis, and their qualitative and quantitative changes in some cases of dry skin or atopic xerosis. Moreover, we show that reconstructed human skin models could provide valuable tools to assess in vitro the biological interest of active compounds on epidermal lipogenesis. Based on such in vitro studies, we assume that the association of vitamin C and some exogenous sphingolipid could enhance the endogenous ceramide content deficient in some cases of atopic dry skin.