Comparison of three different sampling methods for canine skin lipids.

BACKGROUND: Epidermal lipids are of major interest in dermatological research, especially in canine atopic dermatitis. Owing to the existence of several sampling methods, the interpretation of study results is often complicated.
OBJECTIVES: This study aimed to compare three different sampling methods and to establish a minimally invasive method for collecting canine epidermal lipids. ANIMALS AND METHODS: Skin samples from five dogs with no obvious skin abnormalities were taken from the caudal back and the inguinal region postmortem. Samples consisted of heat-separated epidermis of three skin biopsies, three scrapes and three skin scrubs. Lipids were analysed by high-performance thin-layer chromatography; the resulting bands were identified by using corresponding standards, retardation factors and mass spectrometry. The influences of the sampling method, the body site and the ceramide standards were investigated.
RESULTS: Between body sites, significant differences were found for cholesterol sulphate, cholesteryl esters and triglycerides. Significant differences between sampling methods were detected for all lipid fractions except for cholesterol sulphate and glucosylceramides within the lipid profile, and for at least four ceramide classes within the ceramide profile. The most obvious discrepancies were found between heat-separated epidermis and skin scrub. The reproducibility was high for scraping and skin scrub, but was lowest for heat-separated epidermis. Furthermore, this study revealed a marked influence of ceramide standards on the results regarding the ceramide profile. CONCLUSIONS AND CLINICAL IMPORTANCE: Scraping and skin scrub are comparably suitable methods for skin lipid sampling, whereas the analysis of heat-separated epidermis may not be the method of first choice.