Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Department of Orthopaedic Surgery, The Jikei University School of Medicine, 3-25-8 Nishi-Shinbashi, Minato-ku, Tokyo, 105-8461, Japan.
Calcif Tissue Int. 2022 Jun;110(6):736-745. doi: 10.1007/s00223-021-00940-2. Epub 2022 Jan 6.
Bone material quality is important for evaluating the mechanical integrity of diseased and/or medically treated bones. However, compared to the knowledge accumulated regarding changes in bone mass, our understanding of the quality of bone material is lacking. In this study, we clarified the changes in bone material quality mainly characterized by the preferential orientation of the apatite c-axis associated with estrogen deficiency-induced osteoporosis, and their prevention using ibandronate (IBN), a nitrogen-containing bisphosphonate. IBN effectively prevented bone loss and degradation of whole bone strength in a dose-dependent manner. The estrogen-deficient condition abnormally increased the degree of apatite orientation along the craniocaudal axis in which principal stress is applied; IBN at higher doses played a role in maintaining the normal orientation of apatite but not at lower doses. The bone size-independent Young's modulus along the craniocaudal axis of the anterior cortical shell of the vertebra showed a significant and positive correlation with apatite orientation; therefore, the craniocaudal Young's modulus abnormally increased under estrogen-deficient conditions, despite a significant decrease in volumetric bone mineral density. However, the abnormal increase in craniocaudal Young's modulus did not compensate for the degradation of whole bone mechanical properties due to the bone loss. In conclusion, it was clarified that changes in the material quality, which are hidden in bone mass evaluation, occur with estrogen deficiency-induced osteoporosis and IBN treatment. Here, IBN was shown to be a beneficial drug that suppresses abnormal changes in bone mechanical integrity caused by estrogen deficiency at both the whole bone and material levels.
骨材料质量对于评估患病和/或经医学治疗的骨骼的机械完整性很重要。然而，与我们对骨量变化的了解相比，我们对骨材料质量的理解还很缺乏。在这项研究中，我们阐明了主要表现为与雌激素缺乏性骨质疏松症相关的磷灰石 c 轴择优取向的骨材料质量变化，以及伊班膦酸盐（IBN）预防这些变化的机制，IBN 是一种含氮双膦酸盐。IBN 以剂量依赖性方式有效地预防了骨丢失和整体骨强度的降解。雌激素缺乏的状态异常增加了磷灰石在主要受力轴（颅尾轴）上的取向程度；较高剂量的 IBN 起到了维持磷灰石正常取向的作用，但较低剂量则没有。椎体前皮质壳沿颅尾轴的骨大小独立杨氏模量与磷灰石取向呈显著正相关；因此，尽管体积骨密度显著下降，但在雌激素缺乏条件下，颅尾轴的杨氏模量仍异常增加。然而，由于骨丢失，异常增加的颅尾轴杨氏模量并不能补偿整体骨力学性能的降解。总之，本研究阐明了隐藏在骨量评估中的材料质量变化，这些变化发生在雌激素缺乏性骨质疏松症和 IBN 治疗中。这里，IBN 被证明是一种有益的药物，它可以抑制由雌激素缺乏引起的整体骨和材料水平的骨机械完整性的异常变化。
