耐力运动对青年与老年小鼠股骨组织微结构变化的影响

目的　应用原子力显微镜（atomic force microscope，AFM）观察中等强度耐力运动后青年与老年小鼠股骨组织微结构的变化，并探讨耐力运动对预防和改善骨质疏松的适宜年龄阶段。 方法　不同月龄清洁级雄性C57小鼠40只，平均分为3月龄青年组和16月龄老年组，每组再平均分为对照组和运动组。青年及老年运动组使用转棒仪跑步运动12周，运动参数15 r/min，25 min/日。对照组正常饲养。实验结束后处死各组小鼠取股骨，石蜡包埋切片后通过AFM观察小鼠股骨皮质骨组织微结构。 结果　青年对照组可见骨陷窝环绕哈弗系统排列规则，有骨小管与其相沟通，钙磷晶体部分呈小柱状，部分呈团状分布；与青年对照组相比青年运动组可见骨陷窝数量及大小变化，表面粗糙度显著降低（P＜0.05），提示骨组织表面平滑度增加，骨量增加；与青年对照组相比老年对照组可见骨陷窝数量大小变化，钙磷晶体数量减少，表面粗糙度显著增高（P＜0.05），提示存在骨质疏松；与老年对照组相比老年运动组可见骨陷窝及钙磷晶体数量及大小无明显改变，表面粗糙度改变无统计学意义。 结论　中等强度耐力运动可以改善青年小鼠骨组织微结构，提高骨质量，但对已经发生骨质疏松的老年小鼠骨微结构无明显改善。提示老年骨质疏松的运动预防可能需要从成年开始。

Effect of endurance exercise on microstructure changes of femoral tissue in young and old mice

Objective　To observe the changes of femoral microarchitecture in young and old mice after moderate intensity endurance exercise by atomic force microscope (AFM), and explore the appropriate age range of improving osteoporosis and preventing fracture by exercise.　Methods　Twenty clean male C57 mice aged 3 months were used in the youth group, and 20 clean male mice in the old age group were 16 months old. Each group was divided into a control and an exercise group, with 10 mice in each. The mice in the exercise group run on the rotary stick for 12 weeks, and the motion parameters were 15 r/min, and 25 min/day. The control group was raised normally. After the experiment, the femur of each mice was taken for paraffin-embedded sections, and the microarchitecture of femoral cortical bone was observed by AFM.　Results　In the control young group, Haversian systems were regularly surrounded by bone fossae, communicating with each other through canaliculus. Some calcium and phosphorus crystals were distributed in small column, and some in clusters. Compared with the control young group, the number and size of the bone depression in the exercise young group showed a significant decrease in the roughness ( P < 0.05), which suggested that the smoothness of the bone tissue surface increased. Compared with the control young group, there was a change in the number and size of bone depression in the control old group, the number of calcium and phosphorus crystals decreased, and the surface roughness increased significantly (P<0.05), which indicated that there was osteoporosis. Compared with the control old group, there was no significant change of the number and size of bone depression and the number of calcium and phosphor crystals in the exercise old group, and the surface roughness change was not statistically significant, too.　Conclusions　Moderate intensity endurance exercise can optimize the bone microarchitecture and improve bone quality in young mice. But there is no significant improvement in bone microarchitecture in elderly mice with osteoporosis. It suggests that exercise prevention in elderly osteoporosis may need to start from adulthood.