Molecular reorganization during formation of the human skin barrier studied in situ

Abstract

In vertebrates, skin upholds homeostasis by preventing body water loss. The skin’s permeability barrier is located intercellularly in stratum corneum and consists of stacked lipid lamellae composed of ceramides, cholesterol and free fatty acids. We have combined cryo-EM with molecular dynamics modelling and EM-simulation in our analysis of the lamellae’s formation, a maturation process beginning in stratum granulosum and ending in stratum corneum. Previously, we have revealed the lipid lamellae’s initial- and end-stage molecular organizations. Here, we reveal two cryo-EM patterns representing intermediate stages in the lamellae’s maturation process: a single-band pattern with 2.0-2.5 nm periodicity and a two-band pattern with 5.5-6.0 nm periodicity, that may be derived from lamellar lipid structures with 4.0-5.0 nm and 5.5-6.0 nm periodicity, respectively. Based on the analysis of the data now available on the four maturation stages identified, we can present a tentative molecular model for the complete skin barrier formation process.