Influence of epidermal basement membrane integrity on cutaneous permeability barrier function

Maintenance of epithelial homeostasis and barrier function depends upon the balance between proliferation and differentiation of basal keratinocytes. Basement membrane (BM) plays a role in regulating epithelial proliferation and differentiation by modulating dermal-epidermal interactions. Exposure of skin to the ultraviolet B (UVB) component of sunlight induces expression of matrix metalloproteinases (MMPs) and heparanase, which degrade BM structure [1,2] (Fig. S1), and UVB exposure also induces changes of epithelial differentiation markers and formation of an abnormal horny layer, concomitantly with increased transepidermal water loss (TEWL) [3] (Fig.