The development and inflammatory features of radiotherapy-induced glossitis in rats

Objectives: To improve the existing animal models (mice, rats, and hamsters) for radiotherapy-induced oral mucositis (RTOM), thereby establishing a radiotherapy-induced glossitis (RTG) Sprague-Dawley (SD) rat model. Study Design: A lead device was designed to limit radiation exposure to a 1x1 cm2 area of a rat's dorsal anterior tongue with a single 30Gy of X-ray radiation. The general conditions of the irradiated rats, such as body-weight and behavior, were observed. The oral mucositis index (OMI) of the RTG rats were measured daily. Histological changes of the irradiated tongue tissues were assayed by H&E staining. Results and Conclusion: No significant changes were clinically observed 3 to 4 days after irradiation. At 5 to 6 day, punctuation and confluenced redness of the mucosa were observed. The small blood vessels became more extensive, engorged, thin vessel walls. More infiltrating cells were observable, necrosis and exfoliation of the squamous cells appeared, and the formation of an ulcerative lesion could be observed. Seven to 15 days, the exfoliated epithelial layer was observed to have formed an ulcerative lesion, then aggravated ulcerative lesions consisting of pseudomembranous filament exudates could be observed. The structure of the epithelium had become completely disintegrated, forming deep, microscopic ulcerative lesions. Twenty-one days, the periphery of the ulcer was observed to have begun to heal, and granulation tissue could be observed at the bottom of the ulceration. At 35 days after irradiation, the epithelial structure presented again, but the epithelium was very thin. An RTG animal model was successfully established in SD rats, which provides a new research platform for the study of RTOM pathogenesis.