Transforming growth factor β2 (TGF-β2) in pathogenesis of oral submucous fibrosis: An immunohistochemical study

Background and Objectives: Oral Submucous Fibrosis (OSF) is a potentially malignant oral disorder causing fibrosis of the oral mucosa. Commonly associated with the habit of chewing areca nut in its raw or refined forms, the progressive fibrosis causes intense debility and probable malignant transformation. Arecoline, flavinoids and tannins in the areca nut may activate pro-fibrotic cytokines like transforming growth factor beta (TGF-β) leading to fibrosis. TGF-β and its isoforms probably represent the major pathway in the deposition of collagen fibers in this condition. Very little is known of the role of TGF-β2, as compared withTGF-β1, in OSF. The present study aims to evaluate TGF-β2 immunohistochemically in OSF with a view to understanding its role in the pathogenesis. Materials and Methods: TGF-β2 antibody was detected immunohistochemically on archival paraffin sections of 70 cases of various grades of OSF, 10 cases of normal oral mucosa and five cases of scar tissue. The presence and distribution of the antibody was noted and a quantification of the positive areas was also done using image analyses software and correlated in proportion to the rest of the tissue. Results: Expression of TGF-β2 was more in all grades of OSF when compared with that of normal oral mucosa but less than that expressed in scar tissue. The antibody was detected in epithelium, around the blood vessels, in areas of inflammatory infiltrate, fibroblasts and in muscles. The intensity and proportion of expression paralleled increasing grades of OSF. There was increased expression of the antibody in the epithelium, which is probably the source, but no correlation to epithelial changes (hyperplasia, atrophy or dysplasia) was noted. Conclusion: TGF-β2 is a prominent cytokine in the TGF-β induced pathway of fibrosis but probably plays a contributory role to the main isoform TGF-β1. Its role as a marker of malignant transformation, as seen in other systemic malignant lesions, remains inconclusive in OSF