Effects of X-ray doses on mouse osteoblasts in vitro

Objective To investigate the effects of different X-ray doses on the proliferation and differentiation of mouse osteoblasts in vitro.Methods The mouse osteoblastic-like cell line (MC3T3-E1)was cultured in vitro and divided into 4 groups (n =3).On the second day after seeding,the cells in the 4 groups (control group,0.1 Gy group,0.5 Gy group and 1.0 Gy group) were exposed to X-ray irradiation respectively at 4 different doses of 0,0.1,0.5,1.0 Gy.Cell proliferation,cell cycle and apoptosis were measured on day 1 to day 3 after irradiation; alkaline phosphatase (ALP) activity on days 7,10 and 14 and mineralization on day 14 were evaluated respectively.The mRNA expression of osteocalcin (OCN),core-binding factor α1 (Cbfα1),osteoprotegerin (OPG) and receptor activator of nuclear factor kappa B lig-and (RANKL) were measured by real time-PCR on day 14.Results Increasing doses of X-ray irradiation had no significant effects on cell proliferation,cell cycle or apoptosis compared with the control group(P ＞0.05).Importantly,X-ray irradiation of 0.5 Gy and 1.0 Gy increased ALP activities and mineralized nodules of osteoblasts,and markedly increased mRNA expressions of OPG/RANKL (P ＜ 0.05).Specially,mRNA expressions of OCN and Cbfα1 were also markedly increased after X-ray irradiation of 1.0 Gy (P ＜ 0.05).Conclusion X-ray irradiation at a certain rage of doses (from 0.5 to 1.0 Gy) can promote differentiation and mineralization of mouse osteoblasts but does not affect their proliferation and apoptosis. Key words: X-rays;  Osteoblasts;  Cell proliferation;  Cell differentiation