CHARACTERIZATION OF STRATUM-CORNEUM STRUCTURE IN RECONSTRUCTED EPIDERMIS BY X-RAY-DIFFRACTION

The intercellular lipid regions in the stratum corneum (SC), the outer most layer of the skin, form the major barrier for diffusion of substa nces through the skin. The barrier function of in vitro reconstructed epidermis is still impaired. With respect to further optimization of t he model, it is necessary to characterize its stratum corneum lipid st ructure. In this study, small and wide angle X-ray diffraction were us ed to characterize the lipid organization in stratum corneum isolated from 14-day-old reconstructed epidermis. The measurements were carried out al room temperature, and subsequently as a function of temperatur e between 25 degrees C and 109 degrees C, followed by measurements aft er cooling to room temperature. The results of the X-ray diffraction m easurements revealed the following in reconstructed epidermis. 1) The lamellar ordering of stratum corneum lipids was much lower than that o bserved in native stratum corneum. 2) Crystalline anhydrous cholestero l was present. 3) Orthorhombic packing was present, but the correspond ing reflections were very weak. The orthorhombic packing disappeared b etween 30 degrees C and 45 degrees C. 4) A hexagonal packing was prese nt and disappeared between 60 degrees C and 75 degrees C. 5) Soft kera tin is present. 6) A higher extent of lamellar ordering could be achie ved by heating to 109 degrees C and cooling down to room temperature. Analysis of SC lipids revealed the presence of high amounts of triglyc erides, the level of which could be decreased by lowering the glucose content. However, modulation of culture medium composition did not sig nificantly affect lipid lamellae structures or hydrocarbon chain packi ng.