Existence of a lipid gradient in the upper stratum corneum and its possible biological significance

Abstract

The internal stratum corneum lipid composition was investigated in relation to depth in vivo in healthy human volunteers by extraction following one, three or five strippings. Automated multiple development high-performance thin-layer chromatography (AMD-HPTLC) and gas chromatography (GC) followed by normalized principal component analysis showed a decrease in the amount of lipids extracted after one, three and five strippings. Between levels 0, 1, 3 and 5 the stratum corneum lipid composition showed an increase in phospholipids and cholesterol-3-sulphate at level 3, a decrease in ceramide, cholesterol and free fatty acids after level 1, and a slight decrease in sterol esters at level 3. Lipids extracted after three strippings displayed a characteristic composition with an increase in the proportion of phospholipids and cholesterol-3-sulphate. Free fatty acid analysis in relation to depth revealed a decrease in the amounts of C14:0, C16:0, C16:1, C18:0 and C18:1 between levels 1 and 5 and an increase in the C24:0. A decrease in the unsaturated/saturated chain ratio with depth was also observed, reflecting a greater decrease in unsaturated than saturated free fatty acids. A decrease in the ratios of free fatty acids to cholesterol and free fatty acids to ceramides after three and five strippings, respectively, and previously reported results, confirm the importance of this level of stratum corneum lipids in skin barrier properties.

Liposomal Ursolic Acid (Merotaine) Increases Ceramides and Collagen in Human Skin

“…Following treatments, cells were harvested and counted, and the lipids extracted [9]. The human subjects (3 Caucasian males, 45–55) applied lotions twice per day for 11 days to their forearms before lipids were extracted [10]. Both the cell culture lipids and human skin lipids were separated by silica gel HPTLC, developed by heat and the ceramides quantified by computerized image analysis.…”

Skin Diseases Associated with the Depletion of Stratum Corneum Lipids and Stratum Corneum Lipid Substitution Therapy

“…Their main components are CERs, CHOL and FFAs (predominantly long-chain and saturated), which exist nearly in equimolar amounts on a weight basis and contribute about 40-50, 20-33 and 7-13%, respectively [2,7,23]. The other lipids in the lamellar sheets include cholesterol-3-sulfate (0-7 wt%) and cholesteryl esters (0-20 wt%) [5,23,24]. Nevertheless, these lipids vary with the location and depth of the skin, age, sex and the pathological state of the individual, as well as between individuals, races and seasons of the year [5,6,25,26].…”

Lipid Composition of Outer Stratum corneum in Hereditary Palmoplantar Keratodermas

“…They have also been found in the corneocyte lipid envelope and may play a role in cell adhesion [17]. A decrease in ceramides and free fatty acids from the skin surface to lower levels of the stratum corneum has been shown [18]. A higher amount of free fatty acids is said to be consistent with a decreased cell cohesion [19].…”