070 Depth -related distribution of cell surface glycans in normal and pathological human stratum corneum

During the stratum corneum (SC) barrier formation, extracellular spaces of viable epidermis, rich in glycans, are filled with an organized lipid matrix whereas plasma membranes of keratinocytes are replaced with cornified lipid envelopes. These latter structures comprise cross-linked trans-membrane glycoproteins and proteoglycans. However, little is known about the presence and distribution of glycans within SC. In this work, by using lectin binding, we visualized and quantified, at the ultrastructural level, the distribution of glycans at the surface of corneocytes harvested at different SC depths, allowing us to define the relationship between the distribution of various glycans, proteoglycans and glycoproteins, and other changes occurring during SC maturation. In SC of normal human skin, we found a correlation between the depth –related alterations of corneodesmosome glycoproteins at the cell periphery and α-D-mannosyl and N-acetyl-D-glucosamine labelling patterns. Whereas, the initial peripheral distribution extent of α-linked fucose and α- (2-3) linked sialic acid was overall lower than that of concanavalin A and WGA lectin –detected glycans. Diffuse labelling of heparan sulphate glycosaminoglycans disappeared completely from the outermost corneocytes, whereas that of several simple carbohydrates could be detected at all SC levels. This pattern of glycan distribution was also found at the surface of some corneocytes harvested from the SC of patients suffering from atopic dermatitis, despite an additional abnormal presence of corneocytes entirely covered with glycans detected by Con A, WGA, MAA and UEA lectins in the deep SC. Our results suggest that specific glycan distribution may participate in the progressive changes of SC, as it evolves from the SC compactum to the SC disjunctum layers, towards desquamation.