Decreased level of ceramides in stratum corneum of atopic dermatitis: an etiologic factor in atopic dry skin?

Stratum corneum lipids are an important determinant for both water-retention function and permeability-barrier function in the stratum corneum. However, their major constituent, ceramides, have not been analyzed in detail in skin diseases such as atopic dermatitis that show defective water-retention and permeability-barrier function. In an attempt to assess the quantity of ceramides per unit mass of the stratum corneum in atopic dermatitis, stratum corneum sheet was removed from the forearm skin by stripping with cyanoacrylate resin and placed in hexane/ethanol extraction to yield stratum corneum lipids. The stratum corneum was dispersed by solubilization of cyanoacrylate resin with dimethylformamide, and after membrane filtration, the weight of the stratum corneum mass was measured. The ceramides were quantified by thin-layer chromatography and evaluated as microgram/mg stratum corneum. In the forearm skin of healthy individuals (n = 65), the total ceramide content significantly declined with increasing age. In atopic dermatitis (n = 32-35), there was a marked reduction in the amount of ceramides in the lesional forearm skin compared with those of healthy individuals of the same age. Interestingly, the non-lesional skin also exhibited a similar and significant decrease of ceramides. Among six ceramide fractions, ceramide 1 was most significantly reduced in both lesional and non-lesional skin. These findings suggest that an insufficiency of ceramides in the stratum corneum is an etiologic factor in atopic dry skin.