Assessment of the early impact of different doses of radiotherapy on bone structure in mice using Micro-CT Scanning and biomechanical testing

Objective: To establish a mice model of systemic bone injury induced by different doses of radiation, and evaluate the effects of different radiation doses on bone microstructure and biomechanical properties. Methods: and materials: Forty female healthy C57BL/6J mice were randomly divided into 5 groups (N = 8 in each group): the control group (0 Gy) received no irradiation, the other four groups received single dose whole body irradiation of 1 Gy, 3 Gy, 6 Gy, 9 Gy, respectively. One week after irradiation, bilateral femurs and L5 lumbar vertebrae were dissected completely for micro-Computed Tomography (micro-CT) scanning, biological modulus detection and histomorphological observation. One-way design analysis of variance was used for comparison of measurement data among groups, and two-by-two comparisons between groups were performed using the Dunnet Test. Results: : Compared with the control group ,the differences of the bone microstructure indexes in low-dose group (1 Gy), including BV/TV, Tb.N, Tb.Th, Tb.Sp, Tb.Pf , Conn.D and Ct.Th, were not statistically significant (P>0.05), but the elastic modulus decreased significantly (P<0.05). In high-dose groups (3 Gy, 6 Gy, 9 Gy) , BV/TV, Tb. N, Conn.D decreased significantly (P<0.05) , Tb. Sp and Tb.Pf increased significantly (P<0.05) and elastic modulus decreased significantly (P<0.05). Conclusion: Low-dose (1 Gy) radiotherapy had little effect on bone microstructure, but significant effect on bone biomechanical properties; while higher dose radiotherapy had both significant effect on bone microstructure and biomechanical properties, which leaded to the destruction of bone microstructure and the decrease of bone strength.