McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States.
McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States; Department of Radiology, Cumming School of Medicine, McCaig Institute for Bone and Joint Health, University of Calgary, Calgary, Canada.
Bone. 2021 Oct;151:116031. doi: 10.1016/j.bone.2021.116031. Epub 2021 Jun 5.
The maternal skeleton undergoes dramatic bone loss during pregnancy and lactation, and substantial bone recovery post-weaning. The structural adaptations of maternal bone during reproduction and lactation exert a better protection of the mechanical integrity at the critical load-bearing sites, suggesting the importance of physiological load-bearing in regulating reproduction-induced skeletal alterations. Although it is suggested that physical exercise during pregnancy and breastfeeding improves women's physical and psychological well-being, its effects on maternal bone health remain unclear. Therefore, the objective of this study was to investigate the maternal bone adaptations to external mechanical loading during pregnancy, lactation, and post-weaning recovery. By utilizing an in vivo dynamic tibial loading protocol in a rat model, we demonstrated improved maternal cortical bone structure in response to dynamic loading at tibial midshaft, regardless of reproductive status. Notably, despite the minimal loading responses detected in the trabecular bone in virgins, rat bone during lactation experienced enhanced mechano-responsiveness in both trabecular and cortical bone compartments when compared to rats at other reproductive stages or age-matched virgins. Furthermore, our study showed that the lactation-induced elevation in osteocyte peri-lacunar/canalicular remodeling (PLR) activities led to enlarged osteocyte lacunae. This may result in alterations in interstitial fluid flow-mediated mechanical stimulation on osteocytes and an elevation in solute transport through the lacunar-canalicular system (LCS) during high-frequency dynamic loading, thus enhancing mechano-responsiveness of maternal bone during lactation. Taken together, findings from this study provide important insights into the relationship between reproduction- and lactation-induced skeletal changes and external mechanical loading, emphasizing the importance of weight-bearing exercise on maternal bone health during reproduction and postpartum.
母体骨骼在怀孕和哺乳期会经历显著的骨质流失，而在断奶后会有大量的骨质恢复。母体骨骼在生殖和哺乳期间的结构适应性对关键承重部位的机械完整性提供了更好的保护，这表明生理承重在调节生殖引起的骨骼变化方面的重要性。虽然有研究表明，怀孕期间和哺乳期进行体育锻炼可以改善女性的身心健康，但它对母体骨骼健康的影响仍不清楚。因此，本研究的目的是探讨母体骨骼对外在机械负荷在怀孕、哺乳期和断奶后恢复期间的适应能力。通过在大鼠模型中使用体内动态胫骨加载方案，我们证明了在胫骨中段对动态加载的母体皮质骨结构的改善，而与生殖状态无关。值得注意的是，尽管处女大鼠的小梁骨中检测到的加载反应最小，但哺乳期大鼠的小梁和皮质骨在机械反应性方面都得到了增强，与其他生殖阶段或同龄处女大鼠相比。此外，我们的研究表明，哺乳期诱导的破骨细胞周围/管腔重塑（PLR）活性升高导致了骨细胞陷窝的增大。这可能导致间质液流介导的机械刺激对破骨细胞的改变，以及在高频动态加载过程中通过骨陷窝-管腔系统（LCS）的溶质转运增加，从而增强哺乳期母体骨骼的机械反应性。总之，本研究的结果提供了重要的见解，了解生殖和哺乳期引起的骨骼变化与外在机械负荷之间的关系，强调了在生殖和产后进行负重锻炼对母体骨骼健康的重要性。
