The Effects of Pentoxifylline Administration on TGF-β1 Expression in Rats with Radiation-Induced Muscle Fibrosis

The aim of this study was to investigate the potential influence of pentoxifylline (PTX) administration on transforming growth factor beta 1 (TGF-β1) expression and the development of radiation-induced fibrosis (RIF) in Sprague-Dawley rats. Seventeen rats (n= 17) were randomly divided into four groups: The first one received a single dose equivalent to 90 Gy of radiotherapy (RT) to the rectus femoris muscle, the second received PTX administration (25 mg/kg/day) via gavage in addition to irradiation (RT+PTX), the third group received only PTX, and the fourth group served as the controls. At the end of 24 days, fibrosis formation was assessed by light microscopy. The TGF-β1serum and tissue levels were assessed with enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction methods. Immunohistochemical staining revealed focal punctate cytoplasmic TGF-β1 staining in the irradiated group compared with the control group. Morphological changes, including increased oedema and mild collagen thickening, were observed in both the RT and RT+PTX groups. Reverse transcription polymerase chain reaction results revealed no significant differences between the RT, PT+PTX, PTX, and Control group. ELISA results showed substantial differences between the RT, RT+PTX, PTX, and Control group (p= 0.125). The Control group without therapy exhibited higher ELISA results. PTX administration did not demonstrate a positive effect on the serum and muscle expression of TGF-β1 in rats with fibrosis induced by a single dose of radiation. Additionally, TGF-β1 may not be a reliable marker of fibrosis that can be routinely used in the early stages of similar radiotherapy-related tissue damage. Keywords: Pentoxifylline, Fibrosis, Radiation therapy, TGF-β1 expression