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. We had reported that the decrease in the number of differentiated cells and reduction in myotube formation induced by X-ray radiation of 2 Gy were inhibited by insulin-like growth factor-1 (IGF-1). In this study, we investigated the effects of fibroblast growth factor-2 (FGF-2) and hepatocyte growth factor (HGF) on 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 4×104 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 1 Gy/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. During the differentiation culture, FGF-2 (1, 10, 100 ng/ml) ot HGF (1, 10, 100 ng/ml) was added to the culture medium. Differentiation of cells into myocytes and myotubes was identified by fluorescence immunostaining with an anti-myosin (skeletal muscle) monoclonal antibody (Histofine).
Results
One ng/ml FGF-2 and 1, or 10 ng/ml HGF protected the decreased myotube formation. The inhibition of myotube formation by X-ray radiation at 4 Gy did not reverse by addition of FGF-2 or HGF.
Conclusion
The decrease in the number of differentiated cells and reduction in myotube formation induced by X-ray radiation of 2 Gy were inhibited by FGF-2 or HGF.
