Effect of lipids on the aggregation and permeability of human stratum corneum

The role of stratum corneum (SC) constituents in SC barrier properties was assessed directly in vitro in a reaggregated system. Fragments of SC from the sole of the foot (hyperplastic tissue) and from the calf (normal tissue) were reduced, separately, to individual cells and these cells were depleted of lipids by solvent extraction. Lipids taken from the cells themselves or from SC from other areas of the body were then added to the cells. None of the fractions used allowed for reaggregation of plantar SC cells, or of trypsinized calf SC cells. In contrast, calf SC cells reaggregated equally well with all lipids and formed coherent SC sheets. At equal lipid:cell ratios, however, plantar lipid-calf cell SC sheets were about three time more permeable to water than calf lipid-calf cell SC sheets. The effectiveness of the barrier function of the SC sheets was directly proportional to the amount of added lipid. We conclude that in normal SC the extractable lipids are intimately involved in cellular adhesion/dyshesion and in barrier formation.