Comparative Characterisation of Proliferation and Apoptosis of Colonic Epithelium after Electron Irradiation with 2 GY and 25 GY

Development of new techniques for multimodal treatment and diagnostics of various neoplasms and the improvement of current techniques can significantly increase the life expectancy of patients with carcinomas of the colon and abdominal-cavity organs, since prevention of various side effects of radiation therapy is one of the main problems of oncological care. Electron irradiation is one of the most promising types of radiation therapy. There are no data on proliferation and apoptosis of the colon epithelium after irradiation with electrons, especially in different modes (single and summary). Morphological evaluation of apoptosis and proliferation of colonic epithelium after local irradiation with electrons were conducted at doses of 2 Gy (Gray) and 25 Gy. Colon fragments from sexually mature Wistar rats (n = 50, body weight 200 +/- 10 g) were divided into three groups: I-control (n = 10); II-experimental group (n = 20; local single electron irradiation at a dose of 2 Gy); III-experimental group (n = 30) with local fractional irradiation with electrons at a total dose of 25 Gy. They were studied using light microscopy using hematoxylin and eosin staining and immunohistochemical reactions with antibodies to Ki-67 and caspase-3 (Cas3). Morphological disorders were accompanied by increased expression of pro-apoptotic molecules (caspase-3), and the period of regeneration by proliferative marker (Ki-67). Colon electron irradiation led to disturbances in the histoarchitecture of varying severity, and an increase in cell apoptosis was observed (increased expression of caspase-3 and decrease in Ki-67). In addition, modulation of the PI3K/AKT and MAPK/ERK signalling pathways was detected. The most pronounced destructive changes were observed in the group of 25 Gy fractionated electron irradiation.