Sun Zhongyang, Cao Xinsheng, Hu Zebing, Zhang Lianchang, Wang Han, Zhou Hua, Li Dongtao, Zhang Shu, Xie Manjiang
The Key Laboratory of Aerospace Medicine, Ministry of Education, The Fourth Military Medical University, 710032 Xi'an, Shaanxi, China.
Center of Cardiology, Navy General Hospital, 100048 Beijing, China.
Bone. 2015 Jul;76:121-8. doi: 10.1016/j.bone.2015.04.006. Epub 2015 Apr 11.
Emerging evidence indicates that microRNAs (miRNAs) play important roles in modulating osteoblast function and bone formation. However, the influence of miRNA on osteoblast proliferation and the possible mechanisms underlying remain to be defined. In this study, we aimed to investigate whether miR-103 regulates osteoblast proliferation under simulated microgravity condition through regulating Cav1.2, the primary subunit of L-type voltage sensitive calcium channels (LTCCs). We first investigated the effect of simulated microgravity on osteoblast proliferation and the outcomes clearly demonstrated that the mechanical unloading inhibits MC3T3-E1 osteoblast-like cell proliferation. Using quantitative Real-Time PCR (qRT-PCR), we provided data showing that miR-103 was up-regulated in response to simulated microgravity. In addition, we observed that up-regulation of miR-103 inhibited and down-regulation of miR-103 promoted osteoblast proliferation under simulated microgravity condition. Furthermore, knocking-down or over-expressing miR-103, respectively, up- or down-regulated the level of Cav1.2 expression and LTCC currents, suggesting that miR-103 acts as an endogenous attenuator of Cav1.2 in osteoblasts under simulated microgravity condition. More importantly, we showed that the effect of miR-103 on osteoblast proliferation was diminished in simulated microgravity, when co-transfecting miR-103 mimic or inhibitor with Cav1.2 siRNA. Taken together, our data suggest that miR-103 inhibits osteoblast proliferation mainly through suppression of Cav1.2 expression under simulated microgravity condition. This work may provide a novel mechanism of microgravity-induced detrimental effects on osteoblast proliferation, identifying miR-103 as a novel possible therapeutic target in bone remodeling disorders in this mechanical unloading.
新出现的证据表明，微小RNA（miRNA）在调节成骨细胞功能和骨形成中发挥重要作用。然而，miRNA对成骨细胞增殖的影响及其潜在机制仍有待确定。在本研究中，我们旨在探讨miR-103是否通过调节L型电压敏感性钙通道（LTCCs）的主要亚基Cav1.2在模拟微重力条件下调节成骨细胞增殖。我们首先研究了模拟微重力对成骨细胞增殖的影响，结果清楚地表明机械卸载抑制MC3T3-E1成骨样细胞的增殖。使用定量实时聚合酶链反应（qRT-PCR），我们提供的数据表明，miR-103在模拟微重力作用下上调。此外，我们观察到，在模拟微重力条件下，miR-103的上调抑制而成骨细胞增殖，miR-103的下调促进成骨细胞增殖。此外，分别敲低或过表达miR-103，上调或下调Cav1.2表达水平和LTCC电流，表明在模拟微重力条件下，miR-103在成骨细胞中作为Cav1.2的内源性衰减器发挥作用。更重要的是，当将miR-103模拟物或抑制剂与Cav1.2小干扰RNA（siRNA）共转染时，我们发现miR-103对成骨细胞增殖的影响在模拟微重力条件下减弱。综上所述，我们的数据表明，在模拟微重力条件下，miR-103主要通过抑制Cav1.2表达来抑制成骨细胞增殖。这项工作可能提供了一种微重力对成骨细胞增殖产生有害影响的新机制，确定miR-103是这种机械卸载导致的骨重塑障碍中一个新的潜在治疗靶点。
