Resistance to Unloading-Induced Three-Dimensional Bone Loss in Osteopontin-Deficient Mice
作者:Muneaki Ishijima、Kunikazu Tsuji、Susan R. Rittling、Teruhito Yamashita、Hisashi Kurosawa、David T. Denhardt、Akira Nifuji、Masaki Noda
DOI:10.1359/jbmr.2002.17.4.661
日期:——
Recent development in three‐dimensional (3D) imaging of cancellous bone has made possible true 3D quantification of trabecular architecture. This provides a significant improvement in the measures available to study and understand the mechanical functions of cancellous bone. We recently reported that the presence of osteopontin (OPN) was required for the effects of mechanical stress on bone as OPN‐null (OPN−/−) mice showed neither enhancement of bone resorption nor suppression of bone formation when they were subjected to unloading by tail suspension. However, in this previous study, morphological analyses were limited to two‐dimensional (2D) evaluation. Although bone structure is 3D and thus stress effect should be evaluated based on 3D parameters, no such 3D morphological features underlying the phenomenon have been known. To elucidate the role of OPN in mediating mechanical stress effect based on true quantitative examination of bone, we evaluated 3D trabecular structures of hindlimb bones of OPN−/− mice after tail suspension. Tail suspension significantly reduced 3D parameters of bone volume (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and anisotropy and increased 3D parameters on trabecular separation (Tb.Sp) in wild‐type mice. In contrast, these 3D parameters were not altered after tail suspension in OPN−/− mice. These data provided evidence that OPN is required for unloading‐induced 3D bone loss.
最近,松质骨三维成像技术的发展使小梁结构的真正三维量化成为可能。这大大改进了研究和了解松质骨机械功能的方法。我们最近报告说,机械应力对骨的影响需要骨生成素(OPN)的存在,因为当小鼠尾部悬吊卸载时,OPN-null(OPN-/-)小鼠既不表现出骨吸收的增强,也不表现出骨形成的抑制。然而,在之前的研究中,形态学分析仅限于二维(2D)评估。虽然骨结构是三维的,因此应根据三维参数评估应力效应,但目前还不知道这种现象背后的三维形态特征。为了根据骨骼的真实定量检查来阐明 OPN 在介导机械应力效应中的作用,我们评估了 OPN-/- 小鼠尾悬吊后后肢骨骼的三维小梁结构。尾悬吊明显降低了野生型小鼠骨体积(BV/TV)、骨小梁数量(Tb.N)、骨小梁厚度(Tb.Th)和各向异性的三维参数,增加了骨小梁分离(Tb.Sp)的三维参数。相比之下,OPN-/-小鼠尾部悬吊后,这些三维参数没有发生变化。这些数据提供了证据,证明卸载诱导的三维骨丢失需要OPN。