Enhancement of Epidermal Basement Membrane Formation by Synthetic Inhibitors of Extracellular Matrix-degrading Enzymes

Human skin equivalents (HSEs), which are three-dimensional (3D) organotypic culture models, are essential tools to examine a wide range of hypotheses on the structure and function of epithelial tissues, structural assembly of extracellular matrix, and dermal-epidermal interactions. Here, we review epidermal basement membrane formation in HSEs focusing on enhancers of basement membrane formation (especially inhibitors of extracellular matrix-degrading enzymes) with potential applications in skin biology research and tissue engineering. Exogenous addition of laminin-332 or type IV collagen in HSEs increases expression and deposition of types IV and VII collagen and enhances epidermal basement membrane assembly in HSEs. These results suggested that epidermal basement membrane structure would also be enhanced by inhibition of enzymes that degrade extracellular matrix components produced by the cells. Indeed, epidermal basement membrane components produced by keratinocytes and fibroblasts in HSEs are concentrated and stabilized at the dermal-epidermal interface in the presence of synthetic inhibitors of matrix metalloproteinases, plasmin, and heparanase. Increased local concentrations of epidermal basement membrane components may provide a favorable microenvironment at the dermalepidermal junction for formation of epidermal basement membrane structures, including lamina lucida, lamina densa, lamina fibroreticularis and anchoring complex. Inhibitors of extracellular matrixdegrading enzymes therefore allow us to generate more stable 3D culture models for laboratory investigations of the regulatory mechanisms of in vivo skin structure and function, and may also prove valuable for improving the clinical outcome after grafting of skin substitutes.