Establishment of a murine model for radiation-induced bone loss using micro-computed tomography in adult C3H/HeN mice

Bone changes are common sequela of radiation therapy for cancer. The purpose of this study was to establish an experimental model of radiation-induced bone loss in adult mice using micro-computed tomography (µCT). The extent of changes following 2 Gy gamma irradiation (2 Gy/min) was studied at 4, 8, 12 or 16 weeks after exposure. Adult mice that received 1, 2, 4 or 6 Gy of gamma-rays were examined 12 weeks after irradiation. Tibiae were analyzed using µCT. Serum markers and biomechanical properties were measured and the osteoclast surface was examined. A significant loss of trabecular bone in tibiae was evident 12 weeks after exposure. Measurements performed after irradiation showed a dose-related decrease in trabecular bone volume fraction (BV/TV) and bone mineral density (BMD), respectively. The best-fitting dose-response curves were linear-quadratic. Taking the controls into accounts, the lines of best fit were as follows: BV/TV (%)= -0.071D(2)-1.799D+18.835 (r(2)=0.968, D=dose in Gy) and BMD (mg/cm(3)) = -3.547D(2)-14.8D+359.07 (r(2)=0.986, D=dose in Gy). Grip strength and body weight did not differ among the groups. No dose-dependent differences were apparent among the groups with regard to mechanical and anatomical properties of tibia, serum biochemical markers and osteoclast activity. The findings provide the basis required for better understanding of the results that will be obtained in any further studies of radiation-induced bone responses.