Fractionated irradiation of murine salivary glands resulted in focal acinar cell atrophy, immune cell infiltration, fibrosis, and hyposalivation

Background Radiotherapy of head and neck cancer may cause detrimental late side effects such as fibrosis and hyposalivation. Our aim was to investigate late radiation-induced cellular and molecular changes of the salivary glands after fractionated irradiation to the head and neck in a murine model. Methods 12-week-old female C57BL/6J mice were irradiated with X-rays to a total dose of 66 Gy, given in 10 fractions over 5 days. The radiation field covered the oral cavity and major salivary glands. Salivary gland function was assessed by collecting saliva at baseline and at various time points after irradiation. The submandibular (SMG), sublingual (SLG), and parotid glands (PG) were dissected at day 105. Using different staining techniques, morphological, cellular, and molecular changes were investigated in the salivary glands. Results Saliva production was significantly reduced in irradiated compared to control mice at day 35, 80, and 105. We observed a significant decrease in total gland area and a significant increase in fibrotic area in irradiated compared to control SMG at day 105. Atrophy of acinar cells was observed in all irradiated SMG and SLG. Increased amount of chronic inflammatory cells, increased cell proliferation and altered expression of apoptotic markers were found in atrophic areas of irradiated glands. Conclusion Acinar and duct cells in irradiated salivary glands show increased cell proliferation and altered expression of apoptotic markers, proposing an attempt to overcome or withstand tissue damage caused by irradiation. This suggests a potential for regeneration of salivary glands after radiation therapy.