Abstract
Background:
Skin cancer is the most frequently diagnosed type of cancer among all malignant neoplasms. The decrease in mitotic activity and the death of intact keratinocytes arise due to the constantly renewing epithelium is highly sensitive to ionising radiation.
Aim:
The aim of the study is immunohistochemical evaluation of the proliferative-apoptotic balance of keratinocytes, the fibrous component of the skin and the expression of pro-inflammatory and anti-inflammatory cytokines after single or fractional local electron irradiation.
Methods:
Wistar rats (n=80) were taken from the ITM&B Vivarium (Sechenov University) and divided into groups: I – control, which were injected with saline; and experimental groups, local electron irradiation at doses: II – 8 Gy (single), III – 40 Gy (single), IV – summary dose 78 Gy (fractional; 13 Gy per day for 6 days). We performed histological analysis, histochemical analysis using Masson, safranine and picrosirius red staining, immunohistochemical (Ki-67, caspase-3, p53, types I and III collagens, IL-1, IL-6, IL-4 and IL-10) and morphometric analysis of skin fragments of the outer surface of the thigh, irradiated in accordance with the design of the experiment. The early and delayed effects of local electron irradiation at different doses were studied.
Results:
After local electron irradiation, dose-dependent morphological changes in the skin of the experimental groups were observed: violation of the histoarchitectonics of the skin confirmed by morphological and morphometric analysis, proliferation of connective tissue according to the results of histochemical and immunohistochemical studies with signs of the radiation-induced skin fibrosis development, an increase in the levels of pro- and anti-inflammatory cytokines. We observed the most pronounced signs of the radiation-induced skin damage in the group of fractional irradiation after three months.
Conclusion:
8 Gy and 40 Gy single local electron irradiation leads to a shift in the proliferative-apoptotic balance of keratinocytes towards their apoptosis, which activity is directly correlate with the dose of ionizing radiation, and 78 Gy in fractions leads to partial desquamation of the epithelium and inflammatory infiltration. In addition, after three months a significant increase in the expression of type I and type III collagen fibers and the development of radiation-induced skin fibrosis takes place against the background of 78 Gy fractional local electron irradiation.

Key words: Electron irradiation, Immunohistochemistry, Keratinocytes, Radiation-induced skin fibrosis