Proliferative Activity of Myoepithelial Cells in Irradiated Rabbit Parotid and Submandibular Salivary Glands

BACKGROUND The behavior of salivary myoepithelial cells (MEC) during chronic irradiation exposure is unknown. This study aimed to investigate the response of MEC to prolonged radiation exposure. MATERIALS AND METHODS 16 rabbits and four controls were irradiated with either 10 Gy, 20 Gy, 30 Gy or 40 Gy (Gray units) of direct axial beam radiation. Parotid and submandibular glands were removed and examined using immunohistochemical double staining. Proliferating MEC were semi-quantified using alpha smooth muscle actin antibodies and proliferating cell nuclear antigen (PCNA) antibodies. RESULTS MEC proliferative activity increased after radiation in both submandibular (P = 0.037) and parotid groups (P = 0.006) compared to controls. Hyper-proliferation was seen only in parotid glands which was almost dose-dependent. Mean percentage MEC proliferation did not correlate with the clinical grading or recovery from oral mucositis (P = 0.47). CONCLUSIONS Parotid glands are more sensitive to radiation compared to submandibular glands. Further research is needed to determine the role of MEC proliferative activity in response to radiation.