Protective effects of insulin-like growth factor-I on the decrease in myogenic differentiation by ionizing radiation.

The aim of the work is to evaluate the effects of insulin-like growth factor-1 (IGF-1) on the decrease in myotube formation induced by ionizing radiation. We induced C2C12 cells to a myogenic linage following X-ray irradiation at 2 and 4 Gy. Myogenic differentiation was estimated using immnocytochemical staining with anti-myosin antibody, and the anti-myosin antibody positive areas, the total number of nuclei, the number of nuclei included in multinucleated myotubes per field, and the myotube formation ratio were analyzed. In the myogenic differentiation in the presence of IGF-1, the decrease in anti-myosin antibody positive areas, the nuclei included in myotubes, and the myotube formation ratio induced by X-ray irradiation at 2 Gy was restored to control levels. The addition of IGF-1 protected against the decrease myotube formation induced by X-ray irradiation at 2 Gy. Since X-ray irradiation at 2 Gy is usually used for multi-fractionated irradiation in radiotherapy, our findings suggest that IGF-1 could be useful to protect against impairment of muscle repair induced by therapeutic dose radiation.