Immunohistochemical and clinical significance of matrix metalloproteinase-2 and its inhibitor in oral lichen planus

Background: Matrix metalloproteinases (MMP) are being considered important mediators in cancer invasion, and plenty of research is in progress. Our objective was to evaluate the presence of MMP-2 and tissue inhibitor of metalloproteinase (TIMP-2) in oral lichen planus (OLP) and to assess its role in the pathogenesis of OLP and as an indicator of malignant transformation. Materials and Methods: Immunohistochemical analysis for MMP-2 and TIMP-2 was performed in thirty histopathologically confirmed, formalin-fixed, paraffin-embedded specimens of OLP (24 cases of reticular and 6 cases of erosive LP). A semi-quantitative analysis was done to assess the expression and distribution of this marker in these lesions. Results: In all cases of OLP, MMP-2 expression was seen mainly in areas of lymphocytic inflammatory infiltrate (100%) in the lamina propria within the overlying epithelium. TIMP-2 expression was seen more than 50% in the fibroblasts and basal and parabasal cells. Conclusion: The expression of MMP-2 and TIMP-2 was observed in all cases of OLP. However, a clinical 5-year follow-up of the lesion revealed no progression of the disease except for chronic exacerbation and regression of these lesions. Although our study considers MMP-2 and TIMP-2 as mediators in the pathogenesis of OLP, it still remains debatable whether they have a direct role to play in the disease process or whether they are suitable biomarkers to assess the disease progression.