KERATINOCYTES EXPRESS FIBRILLIN AND ASSEMBLE MICROFIBRILS - IMPLICATIONS FOR DERMAL MATRIX ORGANIZATION

Fibrillin-containing microfibrils are key architectural structures of the upper dermis and integral components of the dermal elastic fibre n etwork, Microfibril bundles intercalate into the dermal-epithelial jun ction and provide an elastic connection between the dermal elastic fib re network and the epidermis. Immunohistochemical studies have suggest ed that they are laid down both at the dermal-epithelial junction and in the deep dermis, While dermal fibroblasts are responsible for depos ition of the elastin and microfibrillar components that comprise the e lastic fibres of tile deep dermis, the cellular origin of the microfib ril bundles that extrude from the dermal-epithelial junction is not we ll defined, We have used fresh tissues, freshly isolated epidermis and primary human and porcine keratinocyte cultures to investigate the po ssibility that keratinocytes are responsible for deposition of these m icrofibrils, We have shown that keratinocytes in vivo and in vitro syn thesize both fibrillin-1 and fibrillin-2, and assemble beaded microfib rils concurrently with expression of basement membrane collagen. These observations suggest that keratinocytes co-ordinate the secretion, de position and assembly of these distinct structural elements of the der mal matrix, and have important implications for skin remodelling.