Distribution of procollagen type III, collagen type VI and tenascin in oral submucous fibrosis (OSF).

The distribution of procollagen type III, collagen type VI and tenascin was studied in biopsy specimens from the buccal mucosa of 19 Indian women with confirmed oral submucous fibrosis (OSF) using the immunogold-silver staining technique. Immunohistochemistry revealed a loss of stainable procollagen type III and collagen type VI in the fibrotic zones of oral submucous fibrosis compared to normal oral mucosa. Tenascin was noted only very faintly at the subepithelial basement membrane. The present study showed that procollagen type III and collagen type VI in OSF were expressed in a specific pattern which allows a clear differentiation between fibrotic areas and adjacent apparently normal connective tissue stroma. Loss of procollagen type III, and therefore a probable predominance of collagen type I in collagen fiber bundles, and an almost complete loss of collagen type VI might explain the stiffness of the oral mucosa in patients with OSF. The immunohistochemical findings provided evidence that the process of fibrosis starts in the deeper subepithelial connective tissue stroma and not close to the subepithelial basement membrane. Further studies are required to determine whether OSF is due to increased or altered synthesis and deposition of extracellular matrix proteins, altered fibrolysis or both.