不同强度周期性动态力学载荷对微重力下骨质疏松的影响

目的 探讨生理性周期动态力学载荷与过载对微重力致骨质疏松的作用及影响，为宇航员长时间外太空活动发生的相关骨科疾病寻找一种简便的预防或治疗方案。方法 利用尾吊的方法模拟太空微重力环境，建立小鼠骨质疏松模型。32只C57BL/6J正常小鼠随机分为正常组、尾吊组、生理性载荷组和过载组；尾吊的同时对两施加力学载荷组小鼠左侧胫骨进行周期性动态力学加载。实验4周后对比分析各组小鼠后肢胫骨力学性能、骨小梁微观参数、生化指标以及成骨相关基因表达结果。结果 与正常组相比，尾吊组小鼠胫骨松质骨大量流失，胫骨生物力学性能明显降低，骨微观结构严重破坏、成骨活性显著减弱。生理性载荷可使骨力学性能及骨小梁微观结构有明显的改善，成骨活性增强、相关基因表达显著上调（P＜0.05）。过载也能改善微重力下骨质疏松的状况，但改善效果不明显（P＞0.05）。结论 尾吊可成功模拟微重力环境，复制骨质疏松模型；生理性载荷可有效对抗微重力致骨质疏松的发生与发展；过载也能使得微重力所致骨质疏松有所改善，但是结果与尾吊组相比没有显著性差异。
Objective To investigate the role and influence of physiological loading and overloading on microgravity-induced osteoporosis, so as to find a reliable way to prevent or treat related-orthopedic disorders in astronauts induced by long-time space activity. Methods The microgravity environment in space was simulated by tail-suspension experiment, then the osteoporosis models of mice were built. A total of 32 C57BL/6J mice were randomly and evenly separated into four groups: normal group (normal), tail-suspension group (TS), physiological loading group (loading) and overloading group (overloading). Periodic dynamic mechanical load was applied on the left tibia in loading group and overloading group during tail-suspension test. After four weeks, tibial mechanical properties, micro-parameters of bone trabecular, biochemical indices and osteogenesis-related gene expression in each group were compared and analyzed. Results A great loss of tibial cancellous bone, significantly lower tibial biomechanical expression, serious damage of microstructure and weaker osteogenic activity were found in tail-suspended mice as compared with those of normal group. Physiological loading could clearly improve mechanical properties of bones, microstructure of bone trabecular, osteogenic activity and relative gene expression (P＜0.05). Overloading could also improve the condition of microgravity-induced osteoporosis, but the effect was not obvious (P＞0.05). Conclusions Tail-suspension can successfully simulate microgravity environment and duplicate osteoporosis model. Physiological loading can effectively prevent the emergence and development of microgravity-induced osteoporosis, while overloading can also counter microgravity-induced osteoporosis, but the results have no significant differences.