Increased expression of tenascin C by keloids in vivo and in vitro

Tenascin C, undulin, collagen XIV and fibronectin are extracellular matrix glycoproteins with a partial DNA sequence homology. During embryogenesis, t enascin C is abundant in mesenchymal tissues but its distribution in human adult tissue is severely restricted. The levels of tenascin C expression ar e enhanced with skin inflammation, wound healing and hyperproliferative ski n diseases and return to normal in normal scar tissue after wound contracti on is completed. Undulin/collagen XIV is associated with collagen fibrils a nd fibronectin is present throughout the dermis in adult skin but it is pro duced by keloidal fibroblasts in an increased amount. In this study we inve stigated by immunohistochemistry the expression of the three extracellular matrix proteins in keloids and normal skin as well as in keloidal and norma l fibroblasts in vitro, In keloids, increased tenascin C expression was obs erved especially in the reticular dermis associated with collagen fibrils s harply demarcating the limit of the lesion. In normal tissue, tenascin C wa s only expressed beneath the basal lamina and dermal-epidermal junction. Co rresponding to the in vivo findings, tenascin C expression was increased in keloidal fibroblasts compared with normal fibroblasts in vitro (P < 0.003) , whereas undulin/collagen XIV and fibronectin expression in keloids and ke loidal fibroblasts was similar to that in normal tissue and normal fibrobla sts, respectively. Therefore, tenascin C is a marker associated with keloid s and we suggest that keloidal fibroblasts, once stimulated, continue to pr oduce tenascin C independently from circulating factors.