BASEMENT-MEMBRANE PROTEOGLYCANS ARE OF EPITHELIAL ORIGIN IN RODENT SKIN

Basement membrane proteoglycans in mammalian skin comprise at least on e chondroitin sulfate proteoglycan and heparan sulfate proteoglycans, including perlecan. In this study, the origins of basement membrane ch ondroitin sulfate proteoglycan and perlecan were investigated both in vivo and in vitro. For in vivo experiments, pieces of newborn rat epid ermis obtained by dispase treatment were grafted onto athymic nude mic e. Three and six weeks after grafting, immunofluorescence analysis of the grafted skin was carried out, using monoclonal antibodies specific for rat basement membrane chondroitin sulfate proteoglycan and rat an d mouse perlecan, While the isolated rat epidermis was shown to comple tely lack rat basement membrane chondroitin sulfate proteoglycan and r at basement membrane heparan sulfate proteoglycans, including perlecan , immunofluorescence staining of tissue sections from the grafted site s on mice demonstrated the presence of rat basement membrane chondroit in sulfate proteoglycan and rat perlecan on interfollicular and follic ular basement membranes including that separating dermal papillae from adjacent hair follicle epithelium. In contrast, the basement membrane s of all dermal capillaries were positive for mouse perlecan, but nega tive for rat basement membrane chondroitin sulfate proteoglycan and ra t perlecan, including the basement membranes of papillary dermal capil laries beneath the rat epidermis, These data suggest that basement mem brane proteoglycans of the dermal-epidermal junction and hair follicle epithelium are of epidermal (epithelial) origin in vivo. Stratified r at keratinocytes cultured on a collagen matrix at the air-liquid inter face showed the synthesis of perlecan, laminin 1, and type IV collagen in basement membranes, but not clearly detectable basement membrane c hondroitin sulfate proteoglycan.