Abstract
Introduction: Skeletal muscle is relatively stable tissue. However, growth and repair of skeletal muscle are carried out in response to damage or stretch. Skeletal muscle is relatively resistant to X-ray radiation, but the formation of multinucleated myotubes is delayed or suppressed by X-ray irradiation of myoblasts. In this study, we investigated whether insulin-like growth factor-1 (IGF-1), expression of which increases during generation and regeneration of skeletal muscle, improve the delay or suppression of myotube formation induced by X-ray irradiation.
Materials and Methods: Mouse derived myoblast, C2C12 cells, were seeded at a density of 4104 cells/cm2 on a 24-well celldesk plate (Sumitomo Bakelite). After an overnight culture in DMEM medium supplemented with 10% feral bovine serum (FBS), X-ray irradiation at 2 or 4 Gy using an X-ray generator (MBR-1520R; Hitachi Medical Corporation, at 90 cGy/min) was conducted, and then the medium was replaced with DMEM medium with 2% FBS and the culture was continued for 6 days to induce differentiation. Differentiation of cells into myocytes and myotubes was identified by fluorescence immunostaining with an anti-myosin (skeletal muscle) monoclonal antibody (Histofine).
Results and Discussion: Decreased myotube formation was observed after X-ray radiation of 2 Gy and this change was reversed by adding 5 ng/ml IGF-1. The decrease in the number of differentiated cells and reduction in myotube formation induced by X-ray radiation of 2 Gy were inhibited by IGF-1. The X-ray irradiation at 2 Gy is used in multi-fractionated irradiation in radiotherapy, and therefore IGF-1 may be useful for reduction of radiation damage.
