OBJECTIVEThe purpose of this study was to investigate the relationship between apoptosis and proliferation of oral mucosa in lesions of leukoplakia and the role of apoptosis in the pathogenesis of this common oral disease.

METHODSThe mucosa was obtained from the leukoplakia lesions from 6 patients, with average age of 57 years, and all the patients had not received any treatment before this investigation. The lesions were located on the lip (1), gingiva (1), tongue (2) and buccal mucosa (2). All the patients did not have any systemic diseases. Other three normal oral mucosa tissues were collected as the control. In situ terminal deoxynucleotidyl transferase end-labeling (TUNEL) and avidin-biotin peroxidase complex (ABC) immunohistochemical assay were used to detect single-strand DNA breaks and proliferating cell nuclear antigens (PCNA). The negative control slides were treated with the tris saline buffer to substitute the terminal deoxynucleotidyl transferase (TdT) and PCNA-Ab in the assay. Five consecutive high power fields with the magnification of 400 were used to search for positive stained keratinocytes.

RESULTSCompared with the normal mucosa, the keratinocytes in leukoplakia showed positive apoptotic signals in the nucleus of suprabasal epithelial layers, while PCNA-positive stain was present in the basal position. In the connective tissue, positive apoptotic signals were found in lymphocytes and the endothelia of blood vessels.

CONCLUSIONThe results indicate that the death of cells in leukoplakia is partly due to apoptosis which may play an important role in the genesis of oral leukoplakia.