Early and Late Effects of X-Irradiation on Submandibular Gland: A Morphological Study in Mice

Background: Radiotherapy for head and neck cancers causes permanent salivary gland dysfunction and xerostomia. The aim of this study was to determine changes in mice submandibular glands after X-irradiation. Methods: The submandibular glands of male C57BL/6 mice were locally X-irradiated in the head and neck region with a single dose of 7.5 or 15 Gy and analyzed morphologically and morphometrically at 1, 3, 6, 10, 40, and 90 days after irradiation. Results: Two phases of gland reaction to irradiation have been noted. The first, early phase is observed up to 10 days after irradiation. The second, late phase was observed 90 days after irradiation. Also, a dose-related effect was noticed. The most prominent morphological changes were pyknotic nuclei, vacuolization of acinar cells and lysis of acini and granular convoluted tubules. Changes were detected at 3 and 6 days after irradiation followed by tissue regeneration. Ninety days after irradiation, prominent pathological changes (vacuolization and pyknotic nuclei of acinar cells, lysis of acini and granular convoluted tubules and edema) were detected, but the most remarkable change was disseminated mononuclear infiltration. Also, a statistically significant reduction in number of acinar cells was detected in both irradiated glands. Conclusions: Occurrence of disseminated mononuclear infiltration in gland during late post-irradiation phase makes the mouse model potentially better than the rat model for investigation of irradiation-induced salivary gland damage