Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan.
Teijin Nakashima Medical Co., Ltd., 688-1 Joto-Kitagata, Higashi-ku, Okayama 709-0625, Japan.
Int J Mol Sci. 2022 Jul 4;23(13):7423. doi: 10.3390/ijms23137423.
The anisotropic microstructure of bone, composed of collagen fibers and biological apatite crystallites, is an important determinant of its mechanical properties. Recent studies have revealed that the preferential orientation of collagen/apatite composites is closely related to the direction and magnitude of in vivo principal stress. However, the mechanism of alteration in the collagen/apatite microstructure to adapt to the mechanical environment remains unclear. In this study, we established a novel ex vivo bone culture system using embryonic mouse femurs, which enabled artificial control of the mechanical environment. The mineralized femur length significantly increased following cultivation; uniaxial mechanical loading promoted chondrocyte hypertrophy in the growth plates of embryonic mouse femurs. Compressive mechanical loading using the ex vivo bone culture system induced a higher anisotropic microstructure than that observed in the unloaded femur. Osteocytes in the anisotropic bone microstructure were elongated and aligned along the long axis of the femur, which corresponded to the principal loading direction. The ex vivo uniaxial mechanical loading successfully induced the formation of an oriented collagen/apatite microstructure via osteocyte mechano-sensation in a manner quite similar to the in vivo environment.
骨骼的各向异性微观结构由胶原纤维和生物磷灰石晶体组成，是其机械性能的重要决定因素。最近的研究表明，胶原/磷灰石复合材料的择优取向与体内主应力的方向和大小密切相关。然而，胶原/磷灰石微观结构改变以适应机械环境的机制尚不清楚。在这项研究中，我们使用胚胎小鼠股骨建立了一种新颖的体外骨培养系统，能够人为控制机械环境。矿化股骨长度在培养后显著增加；单轴机械加载促进了胚胎小鼠股骨生长板中的软骨细胞肥大。使用体外骨培养系统进行压缩机械加载会诱导出比未加载股骨观察到的更各向异性的微观结构。各向异性骨微观结构中的成骨细胞被拉长并沿着股骨的长轴排列，这与主加载方向相对应。体外单轴机械加载通过成骨细胞的机械感觉成功诱导了定向胶原/磷灰石微观结构的形成，其方式与体内环境非常相似。
