Importance of Apoptotic Mechanisms in Inflammatory Infiltrate of Oral Lichen Planus Lesions

Background: Oral lichen planus (OLP) is an autoimmune disease produced by T lymphocyte attack on basal epithelial cells. OLP can undergo malignant transformation that may be linked to an increased proliferative activity and decreased apoptosis rate of the epithelial cells, phenomena that may be influenced by the inflammatory infiltrate. The objectives of this study were to assess the quantitative importance of apoptosis in the inflammatory infiltrate of OLP and to discuss its influence on the persistence of this infiltrate and on the malignant transformation of this disease. Materials and Methods: In 32 patients with OLP and 20 controls, apoptosis was studied by TUNEL assay and caspase-3 determination, while cell cycle arrest and senescence were studied by measurement of p21 expression. Results: There was a low frequency of lymphocytic apoptosis according to both TUNEL (34.5% of cases negative, 65.5% with mild expression) and caspase-3 expression (42.9% of cases negative, 50% with mild expression) findings. P21 expression was also negative (9.7% of cases) or mild (80.6% of cases) in most cases. Conclusion: The absence or low rate of apoptosis observed in inflammatory cells in OLP appears to contribute to the persistence of the inflammatory infiltrate, potentiating the onset of molecular disorders in epithelial cells and favouring cancer development.