[Establishment mice model of radiation-injured lacrimal gland and pathophysiological exploration]

To establish a radiation-injured model of lacrimal gland in mice and explore its pathophysiology.

Experimental research. According to the random number table, 50 healthy mice were divided into five groups:one control group (n = 10) and four experimental groups (n = 40). The experimental mice (n = 40) were exposed to different dosages of irradiation 12, 15, 18 and 21 Gy, respectively. The sham-irradiated controls (n = 10) were anesthetized in parallel with the irradiated rats but not irradiated. The mice were placed laterally and covered with a bolus material, then the X-ray irradiation was performed under general anaesthesia from above towards the mice' orbital region. The schirmer tests, Single- photon emission computed tomography/Computed tomography (SPECT/CT), HE, immunohistological, and ultrastructural examinations were conducted prior and 3 days, 7 days as well as 30 days after irradiation.Using t test to compare the differentiation of each group at the same time point.

In 12 Gy group, there is no statistically significant decline in tear secretion (3 days after radiation, t = 2.137, P = 0.061;7 days after radiation, t = 1.137, P = 0.243).In 15 Gy group, Schirmer I test showed significantly reduced lachrymal secretion and the difference was statistically significant(3 days after radiation:t = 3.228, P = 0.011;7 days after radiation:t = 4.781, P = 0.001;30 days after radiation:t = 3.162, P = 0.011). Immunohistochemical findings include a significant loss in the expression of α-SMA (3 days after radiation, t = 4.395, P = 0.013; 30 days after radiation, t = 3.049, P = 0.035) , aquaporin (AQP-5) (3 days after radiation, t = 3.587, P = 0.028;30 days after radiation, t = 5.598, P = 0.005) , and an excessive expression of Tenascin-C (3 days after radiation, t = 2.964, P = 0.046;30 days after radiation, t = 4.028, P = 0.017) and CK8 (3 days after radiation, t = 5.103, P = 0.008;30 days after radiation, t = 6.178, P = 0.004) , which were statistically significant. Ultrastructural changes include a retention of secretory granules and an increase of apoptotic acinar nuclei as well as macrophage phagocytosis. Disturbance in the tracer uptake as well as reduction of the lacrimal ejection fraction was assessed under SPET/CT test and the difference was statistically significant (3 days after radiation:t = 2.796, P = 0.029;30 days after radiation:t = 2.641, P = 0.038). This radiation dosage didn't cause obvious eye complications (cataract, radiation retinopathy, etc.). At the dosages of 18 and 21 Gy, the lacrimal gland inflammation and tissue apoptosis expand obviously.

The model of radiation-injured lacrimal gland was successfully constructed. Pathophysiological manifestation include the impaired structures of lacrimal gland cells and infiltration of inflammatory cells, as well as damaged function of tear secretion. These changes may prerequisites for further study on radiological protection of lacrimal glands during radiotherapy of the periorbital region for orbital tumors.