Annexin A5 Involvement in Bone Overgrowth at the Enthesis
Annexin A5 Involvement in Bone Overgrowth at the Enthesis
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DOI：
10.1002/jbmr.3453
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发表时间：
2018-08
影响因子：
6.2
通讯作者：
A. Shimada;H. Ideno;Y. Arai;K. Komatsu;S. Wada;T. Yamashita;N. Amizuka;E. Pöschl;B. Brachvogel;Yoshiki Nakamura;K. Nakashima;H. Mizukami;Y. Ezura;A. Nifuji
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文献类型：
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作者：
A. Shimada;H. Ideno;Y. Arai;K. Komatsu;S. Wada;T. Yamashita;N. Amizuka;E. Pöschl;B. Brachvogel;Yoshiki Nakamura;K. Nakashima;H. Mizukami;Y. Ezura;A. Nifuji
关于成熟动物附着点形成的分子机制知之甚少。在此，我们报告膜联蛋白 A5 (Anxa5) 在调节附着点骨嵴生长中发挥着关键作用。我们发现 Anxa5 在出生后和成年小鼠的附着点中高表达。在 Anxa5 缺陷 (Anxa5–/–) 小鼠中，7 周后，胫骨和股骨附着点处的骨嵴生长尺寸增大。在不存在纤维软骨层的纤维附着点处没有观察到骨过度生长。在 Anxa5–/– 小鼠的纤维软骨层中观察到比野生型 (WT) 小鼠更多的 ALP 表达细胞。钙黄绿素和茜素红双标记显示 Anxa5–/– 小鼠比 WT 小鼠有更多的矿化区域。为了检查机械力的影响，我们进行了跟腱切断术，其中胫骨肌的收缩力传递因手术肌肉释放而受损。在腱切断小鼠中，Anxa5-/- 小鼠的附着点骨过度生长在术后 8 周时降低至与 WT 小鼠相当的水平。后肢卸载后 8 周，悬尾小鼠的骨过度生长也减少到与 Anxa5-/- 和 WT 小鼠相似的水平。这些结果表明附着点处的骨过度生长需要机械力。我们进一步研究了 Anxa5 基因敲低 (KD) 对成骨细胞、软骨细胞和肌腱细胞原代培养物的体外影响。 Anxa5 KD 增加了肌腱细胞和软骨细胞中的 ALP 表达，但没有增加成骨细胞中的 ALP 表达，这表明 Anxa5–/– 小鼠纤维软骨组织中 ALP 活性的增加是由肌腱细胞或纤维软骨细胞中 Anxa5 缺失直接引起的。这些数据表明 Anxa5 可以防止附着点处的骨过度生长，附着点的形成是通过机械力和调节矿化调节剂的表达来介导的。 © 2018 美国骨与矿物质研究学会。
Little is known about the molecular mechanisms of enthesis formation in mature animals. Here, we report that annexin A5 (Anxa5) plays a critical role in the regulation of bone ridge outgrowth at the entheses. We found that Anxa5 is highly expressed in the entheses of postnatal and adult mice. In Anxa5‐deficient (Anxa5–/–) mice, the sizes of bone ridge outgrowths at the entheses of the tibias and femur were increased after age 7 weeks. Bone overgrowth was not observed at the fibrous enthesis where the fibrocartilage layer does not exist. More ALP‐expressing cells were observed in the fibrocartilage layer in Anxa5–/– mice than in wild‐type (WT) mice. Calcein and Alizarin Red double labeling revealed more mineralized areas in Anxa5–/– mice than WT mice. To examine the effects of mechanical forces, we performed tenotomy in which transmission of contractile forces by the tibial muscle was impaired by surgical muscle release. In tenotomized mice, bone overgrowth at the enthesis in Anxa5–/– mice was decreased to a level comparable to that in WT mice at 8 weeks after the operation. The tail‐suspended mice also showed a decrease in bone overgrowth to similar levels in Anxa5–/– and WT mice at 8 weeks after hindlimb unloading. These results suggest that bone overgrowth at the enthesis requires mechanical forces. We further examined effects of Anxa5 gene knockdown (KD) in primary cultures of osteoblasts, chondrocytes, and tenocytes in vitro. Anxa5 KD increased ALP expression in tenocytes and chondrocytes but not in osteoblasts, suggesting that increased ALP activity in the fibrocartilaginous tissue in Anxa5–/– mice is directly caused by Anxa5 deletion in tenocytes or fibrocartilage cells. These data indicate that Anxa5 prevents bone overgrowth at the enthesis, whose formation is mediated through mechanical forces and modulating expression of mineralization regulators. © 2018 American Society for Bone and Mineral Research.