Collagen XVI is expressed by human dermal fibroblasts and keratinocytes and is associated with the microfibrillar apparatus in the upper papillary dermis.

Indirect immunofluorescence staining of normal skin with affinity-purified antibodies revealed a conspicuous presence of collagen XVI at the dermo-epidermal interface where it occurs in close vicinity to collagen VII. In addition, the protein co-localizes with fibrillin 1 at the cutaneous basement membrane zone and the adjacent papillary dermis, but not in deeper layers of the dermis. Both fibronectin and collagen XVI are distributed throughout smooth muscles of hair follicles but do not co-localize. These data suggest, therefore, that collagen XVI contributes to the structural integrity of the dermo-epidermal junction zone by interacting with components of the anchoring complexes and the microfibrillar apparatus. A strong immunofluorescence signal associated with the extracellular matrix of individual cells was observed for keratinocytes or fibroblasts in monolayer cultures. Therefore, both cell types are likely sources of the protein also in situ. The rate of expression of collagen XVI mRNA in keratinocytes is about half of that in normal human skin fibroblasts. In both cell types, TGF-beta2 treatment results in an up-regulation of the collagen XVI-mRNA by approximately 50%. In keratinocytes, synthesis of collagen XVI protein and deposition to the cell layer and the extracellular matrix is stimulated fivefold and twofold, respectively. Since TGF-beta2 also upregulates the biosynthesis of other matrix macromolecules in the subepidermal zone the factor is likely to contribute to the stabilization of matrix zones near basement membranes in healing wounds.