Initial damage produced by a single 15-Gy x-ray irradiation to the rat calvaria skin

Abstract

Background: Calvaria skin has a reduced thickness, and its initial damage produced by irradiation was scarcely reported. We aimed to identify the initial effects of x-ray irradiation in the rat calvaria skin. Methods: After approval by the Animal Ethical Committee, calvaria skin sections of five Wistar rats per time point were evaluated on days 4, 9, 14, and 25 following a single 15-Gy x-ray irradiation of the head. The control group was composed of five rats and evaluated on day 4. Sections were assessed using hematoxylin-eosin and Masson's trichrome staining for morphology, inflammation, and fibrosis. Fibrosis was also evaluated by the collagen maturation index from Picrosirius red staining and by cell proliferation using the immunohistochemistry, after 5bromo-2-deoxyuridine intraperitoneal injection. Results: In irradiated rats, we observed a reduction in epithelial cell proliferation (p = 0.004) and in matrix metalloproteinase-9 expression (p < 0.001), an increase in the maturation index, and with a predominance in the type I collagen fibers, on days 9 and 14 (1.19 and 1.17, respectively). A progressive disorganization in the morphology of the collagen fibers at all time points and changes in morphology of the sebaceous gland cells and hair follicle were present until day 14. Conclusions: The initial damage produced by a single 15-Gy x-ray irradiation to the rat calvaria skin was a change in the normal morphology of collagen fibers to an amorphous aspect, a temporary absence of the sebaceous gland and hair follicles, and without a visible inflammatory process, cell proliferation, or fibrosis process in the dermis.

Immunohistochemical and histochemical analysis of the rat skin after local electron irradiation

“…Temporary damage to the sebaceous glands and hair follicles without signs of inflammation, cell proliferation, or fibrosis was found. It differs from previously described results in the skin from other parts of the body ( Borrelli et al , 2019 ; da Silva Santin et al , 2020 ). Therefore, the problem of radiation-induced fibrosis (RIF) is still relevant.…”

“…However, in response to the ROS release an increase in antioxidant system enzymes has been reported, which aim to capture and destroy ROS, thereby reducing skin damage. The key role belongs to metalloproteinase-9, which is responsible for the remodeling of extracellular matrix components and is regulated by endogenous tissue inhibitors of metalloproteinases and TGF-β1, the relationship of which in the skin after irradiation has not been studied enough ( da Silva Santin et al , 2020 ).…”

Immunohistochemical Analysis of the Skin After Local Electron Irradiation

“…Temporary damage to the sebaceous glands and hair follicles without signs of inflammation, cell proliferation or fibrosis was found. It differs from previously described results in the skin from other parts of the body [14,15]. So, the problem of radiation-induced fibrosis is still relevant.…”

“…However, in response to the ROS release an increase in antioxidant system enzymes has been reported, which aim to capture and destroy ROS, thereby reducing skin damage. The key role belongs to metalloproteinase-9, which is responsible for the remodeling of extracellular matrix components and is regulated by endogenous tissue inhibitors of metalloproteinases and TGF-β1, the relationship of which in the skin after irradiation has not been studied enough [14,37].…”

MT1‐MMP and TIMP‐2 are first expressed in the colon glands after a single dose of azoxymethane (AOM)

“…The majority of MMPs are secreted by cells into the ECM, although some, such as the wellknown membrane-type 1-matrix metalloproteinase (MT1-MMP) also denominated MMP-14, are linked to the cell membrane (Seiki & Yana, 2003). Nevertheless, according to our previous reports (Camargo et al, 2016;da Silva Santin et al, 2020;dos Reis et al, 2019;Fidler & Gomes, 2023;Gomes et al, 2011;Gomes et al, 2017;Hneda & Gomes, 2022) MMPs are expressed both during development and under various treatments.…”