Apoptosis occurs early in the basal layer of the oral mucosa following cancer chemotherapy

Background: Oral mucositis, a debilitating side-effect of chemotherapy, is difficult to prevent or treat. The aim of this study was to characterize the histological and ultrastructural change in the human oral mucosa following cytotoxic chemotherapy. Methods: Oral buccal mucosa biopsies were taken from four volunteers and 20 cancer patients. Each patient had one biopsy prior to chemotherapy and a second biopsy at varying intervals after chemotherapy. Biopsies were assessed histologically and ultrastructurally. Results: Apoptosis increased in the basal layer in the first 3 days after chemotherapy, began to decline at 6 days, but never returned to levels of volunteers by 11 days after treatment. Ultrastructural changes included increased intercellular fibres in basal layer cells, cytoplasmic vacuolation, loss of membrane contact with neighboring cells, multinucleation of suprabasal cells and loss of cellular cytoplasm. These changes persisted in prechemotherapy biopsies in patients who had prior chemotherapy. Conclusions: Apoptosis occurs early, and persists in the basal layer of the buccal mucosa after chemotherapy. Ultrastructural changes were present and remained up to 11 days after chemotherapy.