Rat bone responses to hindlimb unloading-reloading: Composition, BMD and mechanical properties
Rat bone responses to hindlimb unloading-reloading: Composition, BMD and mechanical properties
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DOI：
10.1016/j.actaastro.2023.12.050
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发表时间：
2024-02
影响因子：
3.5
通讯作者：
Jingyu Feng;Lijin Liu;Xiao Yang;Feixiang Lu;Mingrou Zhang;Xingtong Wu;Lianwen Sun
中科院分区：
文献类型：
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作者：
Jingyu Feng;Lijin Liu;Xiao Yang;Feixiang Lu;Mingrou Zhang;Xingtong Wu;Lianwen Sun
简介即使宇航员返回地球重力环境后，太空微重力条件下下肢的骨质流失仍可能持续存在。确定太空飞行后骨骼恢复的程度和时间至关重要，特别是对于长期飞行。然而，对于骨质量各方面的恢复情况缺乏全面的描述，特别是在反映骨质量变化的成分特征方面。因此，本研究的目的是探讨大鼠下肢在卸载（悬尾）和随后的恢复加载期间骨密度、成分特征和力学性能的变化。方法对大鼠进行悬尾4周（TS4），然后再加载4周。通过μ-CT测量骨矿物质密度（BMD）并进行分析。通过三点弯曲试验评估胫骨的力学性能，并使用拉曼光谱评估骨组织的成分特征。进行回归分析以确定与力学性能相关的主要成分。结果在干骺端，胫骨的BMD显着下降，尤其是骨小梁。重新加载后，只有皮质骨显示恢复。在骨干中，皮质骨在卸载期间保持不变，但在重新加载期间表现出延迟的骨丢失。同时，卸载4周后，胫骨的力学性能大幅下降，尽管重新加载过程中弹性模量和极限强度得到了恢复，但刚度和最大强度并未完全恢复。拉曼光谱表征发现卸载 4 周后，骨干的碳酸盐取代度和晶体结晶度有所增加。矿化胶原比率发生了有趣的变化，在骨干中观察到增加，而在干骺端中观察到减少。在 4 周的重新加载过程中，骨干的成分特征比干骺端的成分特征恢复得更早，但结晶度除外，尚未恢复。回归分析表明，碳酸盐替代与卸载 4 周和随后 4 周重新加载期间的骨机械性能具有很强的相关性。结论本研究获得的数据强调了尾悬吊大鼠重新加载期间骨矿物质密度、机械性能和成分特征的不完全恢复。这些发现加深了我们对微重力引起的骨质流失的理解，并为制定干预措施提供了宝贵的信息，不仅适用于宇航员，也适用于长期卸载期间和之后地球上的人们。
IntroductionBone loss in lower limbs under space microgravity condition can persist even after the astronauts return to Earth's gravitational environment. It is crucial to determine the extent and timing of bone recovery after spaceflight, especially for long-term flights. However, there is a lack of comprehensive descriptions of the recovery of various aspects of bone quality, particularly in terms of compositional characteristics that reflect changes in bone quality. Therefore, the objective of this study is to investigate the alterations in bone mineral density, composition characteristics, and mechanical properties of rat lower limbs during unloading (tail suspension) and the subsequent recovery loading period.MethodsRats were subjected to tail suspension for four weeks (TS4) followed by reloading for an additional four weeks. Bone mineral density (BMD) was measured by μ-CT and analyzed. The mechanical properties of the tibia were assessed by a three-point bending test, and the composition characteristics of bone tissue were evaluated using Raman spectroscopy. Regression analysis was performed to identify main component related to mechanical property.ResultsIn the metaphysis, BMD of the tibia significant decreased, particularly in trabecular bone. Upon reloading, only the cortical bone showed recovery. In the diaphysis, cortical bone remained unchanged during unloading but demonstrated delayed bone loss during the reloading period. Simultaneously, the mechanical properties of tibia experienced a substantial reduction after four weeks of unloading, The stiffness and maximum strength did not fully recover, though the elastic modulus and the ultimate strength were restored following the reloading process. Raman spectroscopy characterization found an increase in the carbonate substitution and crystal crystallinity of the diaphysis after 4 weeks of unloading. There was an intriguing alteration in the mineralized collagen ratio, that an increase was observed in the diaphysis while a decrease was observed in the metaphysis. During 4 weeks of reloading, the compositional characteristics of the diaphysis recovered earlier than those of the metaphysis, with the exception of crystallinity which remained unrecovered. Regression analysis indicated that carbonate replacement has a strong correlation to bone mechanical properties during the 4 weeks of unloading and subsequent 4 weeks of reloading.ConclusionsThe data obtained in this study highlight the incomplete recovery of bone mineral density, mechanical properties, and compositional characteristics during reloading in tail-suspended rats. These findings deepen our understanding of microgravity-induced bone loss and provide valuable information to develop interventions not only for astronauts but also for persons on earth during and after prolonged periods of unloading.