VALIDATION OF AN IN-VIVO EXTRACTION METHOD FOR HUMAN STRATUM-CORNEUM CERAMIDES

A topical acetone/diethylether (A/E) lipid extraction method was evalu ated for its suitability for use in the study of stratum corneum lipid s in various skin disorders. Its efficiency was compared in vitro with topical chloroform/methanol (C/M) extraction and ,vith the classical 'integral' C/M extraction (submerged tissue) of stratum corneum or who le epidermis. To estimate the depth of lipid removal by A/E extraction , light microscopic and freeze-fracture electron microscopic studies w ere 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 wat er loss (TEWL) was measured before and after topical A/E extraction an d after every scraping procedure, and correlated with TEWL values foun d after stripping of the stratum corneum. The total amount of lipid fo und with both topical extraction procedures was lower than that found with the integral extraction of the stratum corneum. Light microscopy showed that topical CM extraction induced cell damage in the living ep idermal 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 si ngle skin sample from the same subject were similar irrespective of th e protocol used, and a uniformity in the CER profiles was found in ski n 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. Further more, the CER profiles found using the A/E extraction procedure both i n vivo and in vitro were similar. The CER profiles were also found to be identical throughout the stratum corneum, as revealed by scraping e xperiments. Since the CER profiles are though to play a major role in the stratum corneum barrier function, the non-invasive A/E extraction of epidermal lipids seems to be suitable for clinical application.