Xing Yanghui, Song Liang, Zhang Yingying
Department of Biomedical Engineering, Shantou University, Shantou 515063, China.
Beijing Key Laboratory of Rehabilitation Technical Aids for Old-Age Disability, National Research Center for Rehabilitation Technical Aids, Beijing 100176, China.
Curr Issues Mol Biol. 2022 Aug 11;44(8):3611-3620. doi: 10.3390/cimb44080247.
Both mechanical loading and autophagy play important roles in regulating bone growth and remodeling, but the relationship between the two remains unclear. In this study, we examined bone structure with micro-CT imaging and measured bone mechanical properties with three-point bending experiments using bones from wild-type (WT) mice and conditional knockout (cKO) mice with Atg7 deletion in their osteoblasts. We found that the knockout mice had significantly less bone volume, bone thickness, bone ultimate breaking force, and bone stiffness compared to wild-type mice. Additionally, bone marrow cells from knockout mice had reduced differentiation and mineralization capacities in terms of alkaline phosphatase and calcium secretion, as well as Runx2 and osteopontin expression. Knockout mice also had significantly less relative bone formation rate due to mechanical loading. Furthermore, we found that the osteoblasts from wild-type mice had stronger responses to mechanical stimulation compared to autophagy-deficient osteoblasts from knockout mice. When inhibiting autophagy with 3 MA in wild-type osteoblasts, we found similar results as we did in autophagy-deficient osteoblasts. We also found that mechanical loading-induced ATP release is able to regulate ERK1/2, Runx2, alkaline phosphatase, and osteopontin activities. These results suggest that the ATP pathway may play an important role in the possible involvement of autophagy in osteoblast mechanobiology.
机械负荷和自噬在调节骨骼生长和重塑过程中均发挥着重要作用，但二者之间的关系仍不明确。在本研究中，我们利用显微CT成像检查了骨骼结构，并通过三点弯曲实验，使用野生型（WT）小鼠以及成骨细胞中Atg7基因缺失的条件性敲除（cKO）小鼠的骨骼，测量了骨骼的力学性能。我们发现，与野生型小鼠相比，敲除小鼠的骨体积、骨厚度、骨极限断裂力和骨硬度均显著降低。此外，敲除小鼠的骨髓细胞在碱性磷酸酶和钙分泌以及Runx2和骨桥蛋白表达方面的分化和矿化能力降低。敲除小鼠因机械负荷导致的相对骨形成率也显著降低。此外，我们发现，与敲除小鼠的自噬缺陷型成骨细胞相比，野生型小鼠的成骨细胞对机械刺激的反应更强。当用3-MA抑制野生型成骨细胞中的自噬时，我们得到了与自噬缺陷型成骨细胞类似的结果。我们还发现，机械负荷诱导的ATP释放能够调节ERK1/2、Runx2、碱性磷酸酶和骨桥蛋白的活性。这些结果表明，ATP途径可能在自噬参与成骨细胞力学生物学过程中发挥重要作用。
