We report that dermatopontin (DP), an abundant dermal extracellular matrix protein, is found in the fibrin clot and in the wound fluid, which comprise the provisional matrix at the initial stage of wound healing. DP was also found in the serum but at a lower concentration than that in wound fluid. DP co-localized with both fibrin and fibronectin on fibrin fibers and interacted with both proteins. Both normal fibroblast and HT1080 cell adhesion to the fibrin-fibronectin matrix were dose-dependently enhanced by DP, and the adhesion was mediated by ␣51 integrin. The cytoskeleton was more organized in the cells that adhered to the fibrin-fibronectin-DP complex. When incubated with DP, fibronectin formed an insoluble complex of fibronectin fibrils as visualized by electron microscopy. The interacting sites of fibronectin with DP were the first, thirteenth, and fourteenth type III repeats (III 1 , III 13 , and III 14 ), with III 13 and III 14 assumed to be the major sites. The interaction between III 2-3 and III 12-14 was inhibited by DP, whereas the interaction between I 1-5 and III 12-14 was specifically and strongly enhanced by DP. Because the interaction between III 2-3 and III 12-14 is involved in forming a globular conformation of fibronectin, and that between I 1-5 and III 12-14 is required for forming fibronectin fibrils, DP promotes fibronectin fibril formation probably by changing the fibronectin conformation. These results suggest that DP has an accelerating role in fibroblast cell adhesion to the provisional matrix in the initial stage of wound healing.
Dermatopontin (DP)3 is a 22-kDa protein located in the extracellular matrix (ECM), comprising about 12 mg/kg wet dermis (1, for a review, see Ref.2). It was initially purified from bovine dermis together with decorin (3). To date, over 10 dermatopontin homologues have been identified in five different mammalian species (2, 4 -7) and in 12 different invertebrates (2). DP has multiple activities. It induces fibroblast cell adhesion probably via integrin-type receptors (8). DP accelerates collagen fibrillogenesis and modifies the newly formed collagen fibrils (9). DP-knock-out mice demonstrate an Ehlers-Danlos phenotype (10), showing an abnormal ECM architecture and tissue flexibility in response to mechanical forces. Previously, we have shown that DP interacts with decorin and with transforming growth factor-1 (11). Thus, it is suggested that DP has an ability to interact with multiple proteins, thereby forming a functional supramolecular complex in the ECM. Recently, we showed that DP promotes strong epidermal cell adhesion via ␣31 integrin and syndecan (12). Considering this together with the fibroblast adhesion findings, we hypothesize that DP plays multiple roles in wound healing.Just after wounding, extravasated blood forms a provisional matrix, which is an ECM composed mainly of fibrin and fibronectin (Fn) and a liquid component known as the wound fluid. The Fn in the provisional matrix serves as an adhesion and migration scaffold for fibroblasts in ...
