Validation of an in vivo extraction method for human stratum corneum ceramides

A topical acetone/diethylether (A/E) lipid extraction method was evaluated for its suitability for use in the study of stratum corneum lipids in various skin disorders. Its efficiency was compared in vitro with topical chloroform/methanol (C/M) extraction and with the classical 'integral' C/M extraction (submerged tissue) of stratum corneum or whole epidermis. To estimate the depth of lipid removal by A/E extraction, light microscopic and freeze-fracture electron microscopic studies were carried out on A/E and C/M topically treated skin samples. The in vivo experiments consisted of topical A/E extraction and of classical C/M extraction of scrapings of the stratum corneum. Transepidermal water loss (TEWL) was measured before and after topical A/E extraction and after every scraping procedure, and correlated with TEWL values found after stripping of the stratum corneum. The total amount of lipid found with both topical extraction procedures was lower than that found with the integral extraction of the stratum corneum. Light microscopy showed that topical C/M extraction induced cell damage in the living epidermal cell layers. Great interindividual variation in overall lipid composition was shown in the in vitro experiments irrespective of the extraction protocol used. However, the ceramide (CER) profiles in a single skin sample from the same subject were similar irrespective of the protocol used, and a uniformity in the CER profiles was found in skin samples from different subjects. Similar results were obtained with in vivo topical A/E extractions: marked interindividual variation was seen in overall lipid composition, but not in the CER profile.(ABSTRACT TRUNCATED AT 250 WORDS)