ABNORMALITIES IN STRATUM-CORNEUM STRUCTURE, LIPID-COMPOSITION, AND DESMOSOME DEGRADATION IN SOAP-INDUCED WINTER XEROSIS

In an attempt to understand the underlying biochemical and morphologic al abnormalities that lead to the physical appearance of xerosis, we h ave examined lipids and desmosomes in stratum corneum of normal and so ap-induced winter xerotic skin. In normal skin, electron microscopy re vealed lipid bilayers in the lower layers of the stratum corneum that were absent in the upper layers. In addition, desmosomes were present in che lower stratum corneum bur underwent degradation cowards the upp er surface of the stratum corneum. These observations contrasted with xerotic skin, which had disorganized lipid bilayers in the upper strat um corneum, although apparently normal lipid bilayers in the deeper ti ssue regions. Also, desmosomes remained undegraded in the upper layers of the xerotic stratum corneum, a finding corroborated by western blo tting showing increased levels of desmoglein 1. Chromatographic analys is of stratum corneum lipids showed decreased ceramide and increased f atty acid levels in subjects with xerosis compared with normal individ uals, particularly in the outer stratum corneum layers. Although ceram ides were lost from the stratum corneum, the increased levels of fatty acids may be due in part to the deposition of soap fatty acids. Our r esults support previous studies demonstrating the importance of desmos omal degradation in desquamation. Furthermore, we have been able to sh ow changes in the normal membrane structure of intracellular lipids in the desquamating layers of the stratum corneum. These studies also pr ovide new insights into soap-induced winter xerosis, revealing abnorma lities in stratum corneum lipid composition and organization together with reduced desmosomal degradation.