RESUMO
PURPOSE: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
Assuntos
Diferenciação Celular/efeitos da radiação , Fator de Crescimento Insulin-Like I/farmacologia , Fibras Musculares Esqueléticas/efeitos da radiação , Protetores contra Radiação/farmacologia , Animais , Diferenciação Celular/efeitos dos fármacos , Linhagem Celular , Camundongos , Fibras Musculares Esqueléticas/citologia , Fibras Musculares Esqueléticas/efeitos dos fármacos , Proteína MyoD/genética , RNA Mensageiro/análise , Raios XRESUMO
Therapeutic radiation causes bone damage and may increase fracture risks in treatment for head-and-neck cancer and in pelvic irradiation. These properties can also be used for prevention of heterotopic ossification in hip arthroplasty. To evaluate the effects of ionizing radiation on osteoblast differentiation, C2C12 cells were directed into an osteogenic lineage by treatment with a combination of bone morphogenic protein 2 (BMP-2) (100 ng/ml) and heparin (30 mug/ml) 6 h after irradiation (2 and 4 Gy). Osteoblast differentiation was evaluated based on alkali phosphatase (ALP) activity and expression of mRNA encoding ALP and collagen type I. Ionizing radiation suppressed the growth of C2C12 cells and decreased expression of ALP and collagen type I mRNAs with concomitant reduction of the ALP activity. Although further studies are needed to elucidate the molecular mechanism, our findings suggest that ionizing radiation at therapeutic doses interferes with bone formation by reducing ALP activity and expression of mRNA encoding ALP and collagen type I.
