Optimization of physiological lipid mixtures for barrier repair.

Three stratum corneum lipids, ceramides, cholesterol (CHOL), and free fatty acids (FA), are required for permeability barrier homeostasis. Recent studies have shown that application of one or two of these lipids to perturbed skin delays barrier recovery; only equimolar mixtures allow normal recovery. We asked here whether any physiological lipid mixtures improve barrier repair, as assessed by transepidermal water loss. Whereas an equimolar ratio of ceramides, CHOL, and FA (either the essential fatty acid, linoleic acid, or the nonessential FAs, palmitic or stearic acids) allows normal repair, further acceleration of barrier repair occurs as the ratio of any of these ingredients is increased up to 3-fold. Similar preliminary results were obtained in damaged human skin. Likewise, while acylceramides alone delay barrier recovery, acylceramides: CHOL mixtures within a specific range of molar rations dramatically improve barrier repair. Furthermore, glycosyl ceramides, sphingomyelin, and triglycerides substitute effectively for ceramides and FA, respectively, but neither phospholipids nor cholesterol esters substitute for FA and CHOL, respectively. These studies show the specific requirements of selected stratum corneum lipid mixtures for optimized barrier repair in murine skin, with further validation in human skin. Utilization of physiologic lipids according to these parameters could lead to new forms of topical therapy for dermatoses (e.g., psoriasis, atopic dermatitis, and irritant dermatitis) triggered by abnormal barrier function.