Proliferation and apoptosis in the colonic epithelium of rats after electron irradiation

BACKGROUND: Electron irradiation is one of the most promising modalities for the treatment of malignant colonic neoplasms. AIM: To evaluate the morphology of apoptosis and proliferation in the colonic epithelium of animals after local fractional electron irradiation at a focal dose of 25 Gy. MATERIALS AND METHODS: Two groups of Wistar rats were used: group 1, control (n = 10); and group 2, experimental (n = 20). The experimental group was exposed to local electron irradiation at a focal dose of 25 Gy in fractions of 5 Gy on days 1, 3, 5, 7, and 9. Colonic fragments were examined using light microscopy, and immunohistochemical reactions were performed using antibodies to the Ki-67 and caspase-3 antigens. The wall thickness and diameter of the serous mucosal membrane were measured in micrometers. Morphological changes were evaluated using a scoring system. Results were analyzed using the Kolmogorov–Smirnov test, Student’s t-test, Mann–Whitney U-test, and Fisher’s test. RESULTS: Macroscopic examination of the colon of rats in the experimental group revealed mucosal hyperemia without significant destructive changes. Furthermore, microscopic examination showed insignificant lesions of the colonic mucosa and decreased goblet cells compared with the control group (63.17% ± 1.87% vs. 21.64% ± 1.37%, respectively; p = 0.009). The number of caspase-3-positive epithelial cells increased (28.7% ± 8.2% vs. 14.5% ± 3.9%, p = 0.027). The proliferative index (Ki-67) in colonic crypts decreased after local fractional electron irradiation at a total focal dose of 25 Gy compared with the control group (11.14% ± 6.23% vs. 19.45% ± 5.12%, p = 0.013). СONCLUSION: Local fractional electron irradiation of rats at a total focal dose of 25 Gy was found to induce weak degenerative and dystrophic changes in the epithelium and a decrease in goblet cells while preserving regenerative potential in the colon.