Effect of selective lipid extraction from different body regions on epidermal barrier function

Purpose. To assess the effects of selective lipid extraction and tape strip ping on transepidermal water loss (TEWL) at three body regions in the pig. Methods. Lipids were extracted from the abdominal, inguinal, and back regio ns using three different solvent extraction procedures or cellophane tape s tripping (15x) on Yorkshire: pigs. Three solvent extraction stages were I, cyclohexane (5 mi for three, 1-min extractions); II, cyclohexane/ethanol (4 :1) (5 mi for three, 1-min extractions); and III, cyclohexane/ethanol (1:4) (5 mi for three, 3-min extractions) extracted as follows: Site A, Stage I; Site B, Stage I and II: Site C, Stage I, II and III. Erythema, edema, and TEWL were assessed in control, tape-stripped, and extracted sites at 0, 6. and 24 h. The extracted lipids were analyzed by thin layer chromatography a nd quantified by densitometry for ceramide, cholesterol, cholesterol esters , fatty acids, and triglycerides. Results, The change in TEWL (Delta TEWL) in 14 of the 15 sites was the high est at 24 h and generally increased with each additional extraction. The gr eatest changes were present in the back. Each extraction stage removed spec ific lipids in reproducible quantities that caused the Delta TEWL to increa se from 0 to 24 h. Lipid removal was verified by transmission electron micr oscopy. The mean total lipid concentration depended on extraction solvents and body region, and was reproducible across sites and regions at equivalen t stages of lipid extraction. Relative proportions of individual lipids ext racted were similar across all body regions. Higher concentrations of total lipids were extracted from the back. Conclusions. These studies demonstrate that extraction of lipids increased the Delta TEWL to a level similar to repeated tape stripping at all body si tes in the pig. This study suggested that strategies that could biochemical ly alter epidermal lipid composition may increase absorption of simultaneou sly administered topical compounds and may be useful to enhance drug delive ry.