Fowler Tristan W, Kamalakar Archana, Akel Nisreen S, Kurten Richard C, Suva Larry J, Gaddy Dana
Departments of Physiology & Biophysics, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, AR 72205 USA
Departments of Physiology & Biophysics, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, AR 72205 USA Orthopaedic Surgery, Center for Orthopaedic Research, University of Arkansas for Medical Sciences, College of Medicine, Little Rock, AR 72205 USA.
J Cell Sci. 2015 Feb 15;128(4):683-94. doi: 10.1242/jcs.157834. Epub 2015 Jan 20.
The process of osteoclastic bone resorption is complex and regulated at multiple levels. The role of osteoclast (OCL) fusion and motility in bone resorption are unclear, with the movement of OCL on bone largely unexplored. RANKL (also known as TNFSF11) is a potent stimulator of murine osteoclastogenesis, and activin A (ActA) enhances that stimulation in whole bone marrow. ActA treatment does not induce osteoclastogenesis in stroma-free murine bone marrow macrophage cultures (BMM), but rather inhibits RANKL-induced osteoclastogenesis. We hypothesized that ActA and RANKL differentially regulate osteoclastogenesis by modulating OCL precursors and mature OCL migration. Time-lapse video microscopy measured ActA and RANKL effects on BMM and OCL motility and function. ActA completely inhibited RANKL-stimulated OCL motility, differentiation and bone resorption, through a mechanism mediated by ActA-dependent changes in SMAD2, AKT1 and inhibitor of nuclear factor κB (IκB) signaling. The potent and dominant inhibitory effect of ActA was associated with decreased OCL lifespan because ActA significantly increased activated caspase-3 in mature OCL and OCL precursors. Collectively, these data demonstrate a dual action for ActA on murine OCLs.
破骨细胞性骨吸收过程复杂,受多个层面的调控。破骨细胞(OCL)融合和运动在骨吸收中的作用尚不清楚,OCL在骨上的移动情况很大程度上未被探索。核因子κB受体活化因子配体(RANKL,也称为TNFSF11)是小鼠破骨细胞生成的强效刺激因子,激活素A(ActA)可增强全骨髓中的这种刺激作用。在无基质的小鼠骨髓巨噬细胞培养物(BMM)中,ActA处理不会诱导破骨细胞生成,反而会抑制RANKL诱导的破骨细胞生成。我们推测,ActA和RANKL通过调节OCL前体细胞和成熟OCL的迁移,对破骨细胞生成进行差异性调控。延时视频显微镜观察法测定了ActA和RANKL对BMM以及OCL运动和功能的影响。ActA通过由SMAD2、AKT1和核因子κB抑制蛋白(IκB)信号通路中依赖ActA的变化所介导的机制,完全抑制了RANKL刺激的OCL运动、分化和骨吸收。ActA强大且占主导地位的抑制作用与OCL寿命缩短有关,因为ActA显著增加了成熟OCL和OCL前体细胞中活化的半胱天冬酶-3的水平。总体而言,这些数据证明了ActA对小鼠OCL具有双重作用。