Radiation retards muscle differentiation but does not affect osteoblastic differentiation induced by bone morphogenetic protein-2 in C2C12 myoblasts.

Purpose: Effects of radiation on the differentiation of C2C12 myoblasts were studied using cell cultures in which the cells differentiated into either muscle cells or osteoblasts.

Materials And Methods: A mouse skeletal myoblast cell line, C2C12, was cultured and irradiated at confluence. Muscle differentiation was estimated by counting the number of myosin heavy chain (MHC)-positive multinucleated myotubes. Osteoblast differentiation was analysed by measuring alkaline phosphatase (ALP) activity and osteocalcin production in C2C12 cells treated with recombinant human bone morphogenetic protein-2 (rhBMP-2).

Results: Myotube formation in C2C12 cells was inhibited by 2 and 4 Gy irradiation, but recovered to non-irradiated control levels following further culture. In irradiated cultures, the number of MHC-positive mononucleated cells increased significantly. Irradiation did not, however, alter the induction of osteoblastic phenotypes induced by rhBMP-2 in C2C12. Irradiation also did not affect the expression of MyoD mRNA and myogenin mRNA in myogenic differentiation and induction of osteocalcin mRNA in osteoblastic differentiation.

Conclusions: During differentiation of C2C12 cells, myotube formation was delayed after irradiation, while induction of osteoblasts with BMP-2 was unaffected.