Berteau J P
Department of Physical Therapy, City University of New York - College of Staten Island, New-York, USA.
New York Center for Biomedical Engineering, City University of New York - City College of New York, New-York, USA.
Lab Anim Res. 2024 May 14;40(1):20. doi: 10.1186/s42826-024-00207-5.
Microgravity, a condition experienced in a spatial environment, poses unique challenges to the skeletal system, particularly in juvenile organisms. This study aimed to investigate alterations in bone biomechanics of juvenile mice due to unloading - that simulates microgravity in the laboratory-and the effects of a bone-loading intervention. We compared bone compositional and mechanical properties between 21-six-week-old C57Bl/6 from a control group (wild type) and a group that underwent a tail-suspension unloading protocol to mimic microgravity (MG). The second group (MG) experienced additional in vivo loading protocol (MG + LDG) on the right hind leg, where dynamic compressive loading was applied to the right knee using a custom-built loading device.
Our results show that after two weeks, we successfully induced bone alterations by (i) decreasing the energy dissipated before fracture and (ii) decreasing the yield and maximum stress. In addition, we showed that Mineral to matrix component [ν1PO4/Amide I], Carbonate to Amide [CO3/Amide I], and Crystallinity [1/FWHM(ν1PO4)] are strongly linked in physiological bone but not in microgravity even after loading intervention. While Crystallinity is very sensitive to bone deformation (strain) alterations coming from simulated microgravity, we show that Carbonate to Amide [CO3/Amide I] - a common marker of turnover rate/remodeling activity-is a specific predictor of bone deformation for bone after simulated microgravity. Our results also invalidate the current parameters of the loading intervention to prevent bone alterations entirely in juvenile mice.
Our study successfully induced bone alterations in juvenile mice by using an unloading protocol to simulate microgravity, and we provided a new Raman Spectroscopy (RS) dataset of juvenile mice that contributes to the prediction of cortical bone mechanical properties, where the degree of interrelationship for RS data for physiological bone is improved compared to the most recent evidence.
微重力是空间环境中所经历的一种状态，对骨骼系统构成独特挑战，尤其是在幼年生物体中。本研究旨在调查因卸载（在实验室模拟微重力）导致的幼年小鼠骨生物力学改变以及骨加载干预的效果。我们比较了来自对照组（野生型）的21只六周龄C57Bl/6小鼠和经历尾部悬吊卸载方案以模拟微重力（MG）的一组小鼠之间的骨成分和力学性能。第二组（MG）右侧后腿还经历了额外的体内加载方案（MG + LDG），使用定制加载装置对右膝施加动态压缩载荷。
我们的结果表明，两周后，我们通过以下方式成功诱导了骨骼改变：（i）降低骨折前耗散的能量；（ii）降低屈服应力和最大应力。此外，我们表明，矿物质与基质成分[ν1PO4/酰胺I]、碳酸盐与酰胺[CO3/酰胺I]以及结晶度[1/FWHM(ν1PO4)]在生理状态的骨骼中紧密相关，但即使在加载干预后，在微重力状态下并非如此。虽然结晶度对模拟微重力引起的骨变形（应变）变化非常敏感，但我们表明，碳酸盐与酰胺[CO3/酰胺I]（周转率/重塑活动的常用标志物）是模拟微重力后骨骼骨变形的特定预测指标。我们的结果还证明，目前的加载干预参数无法完全防止幼年小鼠的骨骼改变。
我们的研究通过使用卸载方案模拟微重力成功诱导了幼年小鼠的骨骼改变，并且我们提供了一个新的幼年小鼠拉曼光谱（RS）数据集，有助于预测皮质骨力学性能，与最新证据相比，生理状态骨骼的RS数据之间的相互关系程度得到了改善。
