Radiation-induced muscle fibrosis rat model: establishment and valuation

Abstract

BackgroundLack of animal model of radiation induced muscle fibrosis, this study aimed to establish such a model by using 90 Gy single dose irradiation to mimic clinical relevance and also to explore the potential post-irradiation regenerative mechanism.MethodsSD rats were randomly divided into dose investigation groups and time gradient groups. Group1–6 were irradiated with a single dose of 65Gy, 70Gy, 75Gy, 80Gy, 85Gy and 90Gy respectively, and the degree of rectus femoris fibrosis in the irradiated area was detected at 4 weeks after irradiation. Group 7–9 were irradiated with a single dose of 90Gy, and the results were detected 1, 2, 4, and 8 weeks after irradiation. Then the general condition of rats was recorded. Masson staining was used to detect muscle fibrosis. The ultrastructure of muscles was observed by electron microscope, and the expression changes of satellite cell proliferation and differentiation related genes were detected by quantitative real-time-PCR.ResultsA single dose of 90Gy irradiation could cause muscle fibrosis in rats. As time goes on, the severity of muscle fibrosis and the expression of TGF- β1 increased. Significant swelling of mitochondria, myofilament disarrangement and dissolution, obvious endothelial cell swelling, increased vascular permeability, decrease of blood cell, deposition of fibrosis tissue around the vessel could be found compared with the control group. At around the 4th week, the expressions of Pax7, Myf5, MyoD, MyoG, Mrf4 increased.ConclusionIrradiation of 90Gy can successfully establish the rat model of radiation-induced muscle fibrosis. This model demonstrated that regenerative process was initiated by the irradiation only at an early stage, which can serve a suitable model for investigating regenerative therapy for post-radiation muscle fibrosis.

Establishment and characterization of a radiation‐induced dermatitis rat model

“…Mitochondrial dysfunction has been observed in a variety of radiation-induced diseases such as injury to the skeletal muscle and lacrimal glands and brain damage. 26,46,47 The damaged indirectly activate autophagy. [52][53][54] In this study, the ultrastructural observations indicated that radiation induced severe mitochondrial damage, apoptosis and autophagy.…”

“…26 In brief, 5% pentobarbital sodium (0.1 mL/100 g) was injected intraperitoneally for anaesthesia, and then the surface of the medial rectus femoris on the left thigh was labelled using a marker. 26 In brief, 5% pentobarbital sodium (0.1 mL/100 g) was injected intraperitoneally for anaesthesia, and then the surface of the medial rectus femoris on the left thigh was labelled using a marker.…”

“…The rats were irradiated following a previously reported procedure. 26 In brief, 5% pentobarbital sodium (0.1 mL/100 g) was injected intraperitoneally for anaesthesia, and then the surface of the medial rectus femoris on the left thigh was labelled using a marker. Radiation was administered by a Nucletron Microselectron-HDR Ir-192 system after loading (Nucletron Company, the Netherlands), with the applicator tube fixed at the mark made on the left thigh.…”

“…We previously demonstrated that 90 Gy irradiation induced skeletal muscle fibrosis in Sprague-Dawley rats. 26 Therefore, we used Figure 1A). The changes in skin injury scores during the 12 weeks following a single dose of 90 Gy irradiation are shown in Figure 1B.…”

“…In contrast to the control group with only a few rare apoptotic cells, significantly more apoptotic cells were found 4 and 12 weeks after irradiation; although the numbers of apoptotic cells slightly decreased at 12 weeks, this difference from the 4-weeks group was not statistically significant ( Figure 5B). Since we previously found that irradiation-induced apoptosis might be associated with mitochondria damage, 26 which has been generally linked to apoptosis induction, 30 we further analysed the expression of apoptosis-related proteins with western blotting. Representative immunoblots are shown in Figure 5C, demonstrating that the expression level of the anti-apoptotic protein Bcl-2 significantly increased, whereas the levels of the pro-apoptotic proteins Bax and p53 markedly decreased at both 4 and 12 weeks after irradiation.…”