Simulation studies of stratum corneum lipid mixtures

TL;DR

This study uses atomistic molecular dynamics to analyze how different lipid components in the stratum corneum influence its structural properties, revealing insights into barrier function and mechanical stability.

Contribution

It provides detailed molecular insights into the effects of ceramide, fatty acids, and cholesterol on stratum corneum lipid bilayer structure and mechanics.

Findings

Ceramide-rich bilayers have higher density and lower passive transport.

Lipid bilayers are in gel phase with ordered tails at physiological temperatures.

Optimal composition ratios reduce pressure fluctuations and enhance barrier properties.

Abstract

We present atomistic molecular dynamics results for fully hydrated bilayers composed of ceramide NS-24:0, free fatty acid 24:0 and cholesterol, to address the effect of the different components in the stratum corneum (the outermost layer of skin) lipid matrix on its structural properties. Bilayers containing ceramide molecules show higher in-plane density and hence lower rate of passive transport compared to phospholipid bilayers. At physiological temperatures, for all composition ratios explored, the lipids are in a gel phase with ordered lipid tails. However, the large asymmetry in the lengths of the two tails of the ceramide molecule leads to a fluid like environment at the bilayer mid-plane. The lateral pressure profiles show large local variations across the bilayer for pure ceramide or any of the two component mixtures. Close to the skin composition ratio, the lateral pressure fluctuations are greatly suppressed, the ceramide tails from the two leaflets interdigitate significantly, the depression in local density at the inter-leaflet region is lowered, and the bilayer have lowered elastic moduli. This indicates that the observed composition ratio in the stratum corneum lipid layer is responsible for both the good barrier properties and the stability of the lipid structure against mechanical stresses.