[Improvement of the Skin Barrier Function with Physiologically Active Substances].

Intercellular lipids in the stratum corneum (SC), including ceramides (CERs), cholesterol, and fatty acids, are important for maintaining the skin barrier function. CERs in the SC have vital roles in water retention and the barrier function. A decrease in intercellular lipids, however, reduces the skin barrier function. In this study, the ability of CER precursors to increase the level of CERs in the SC and improve the skin barrier function was examined. Glucosylceramide and sphingomyelin liposomes were used as CER precursors and prepared with a thin-film method. The particle diameter and surface potential of glucosylceramide liposomes were 120.0 nm and -20 mV, while those of sphingomyelin liposomes were 153.3 nm and -11.4 mV, respectively. Transmission electron microscopy images showed that both liposomes were closed vesicles having a lamellar structure. These liposomes were applied from the SC side of a three-dimensional cultured human epidermis model, and the level of CERs in the epidermis was measured by high-performance thin-layer chromatography. In this study, the application of glucosylceramide or sphingomyelin liposomes increased the amount of CERs. In addition, the precursors of CERs were effective in improving the skin barrier function.