Mechanical unloading causes bone loss, but it remains unclear whether disuse-induced changes to bone microstructure are permanent or can be recovered upon reloading. We examined bone loss and recovery in 17 astronauts using time-lapsed high-resolution peripheral quantitative computed tomography and biochemical markers to determine whether disuse-induced changes are permanent. During 6 months in microgravity, resorption was threefold higher than formation. Upon return to Earth, targeted bone formation occurred in high mechanical strain areas, with 31.8% of bone formed in the first 6 months after flight at sites resorbed during spaceflight, significantly higher than the 2.7% observed 6 to 12 months after return. Limited bone recovery at resorption sites after 6 months on Earth indicates a restricted window for reactivating bone remodeling factors in humans. Incomplete skeletal recovery may arise from these arrested remodeling sites, representing potential targets for new interventions, thus providing means to counteract this long-term health risk for astronauts.

中文翻译：

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对太空飞行诱导的骨重塑的跟踪揭示了人类吸收位点恢复的时间有限


机械卸载会导致骨质流失，但目前尚不清楚废用引起的骨骼微观结构变化是永久性的还是可以在重新加载时恢复。我们使用延时高分辨率外周定量计算机断层扫描和生化标志物检查了 17 名宇航员的骨质流失和恢复情况，以确定废用引起的变化是否是永久性的。在微重力下的 6 个月中，吸收率比形成高 3 倍。返回地球后，在高机械应力区域发生有针对性的骨形成，31.8% 的骨是在飞行后的前 6 个月内在太空飞行过程中被吸收的部位形成的，明显高于返回后 2.7 至 6 个月观察到的 12%。在地球上 6 个月后，吸收部位的骨恢复有限表明人类重新激活骨重塑因子的窗口受到限制。这些停滞的重塑部位可能会导致骨骼恢复不完全，这代表了新干预措施的潜在目标，从而为抵消宇航员的这种长期健康风险提供了手段。