MiR-146a通过调控Notch1 信号通路维持关节软骨内稳态的机制研究

Osteoarthritis (OA) afflicts millions of individuals across the world and is the most common cause of chronic disability in older adults. However, the molecular pathogenic mechanisms of OA are still unclear. Recently, microRNA（miRNA ） are believed to be powerful regulators of a range of biological processes including OA. Studies have also suggested possible involvement of miR-146a in physiological and pathological processes of OA in vitro. However, the role of miR-146a in joint cartilage homeostasis in vivo remains largely unclear. Our preliminary data shows that deficiency of miR-146a contributes to early onset of cartilage degradation and synovitis which are characteristic of OA in mice. We hypothesize that miR-146a protects the onset and progression of osteoarthritis through suppressing the expression of Notch1 and IL-6 in vivo. Our proposal will define the role of miR-146a in joint cartilage homeostasis in vivo by studying the loss and gain of function of miR-146a in genetic mouse models. We believe that the completion of this proposal will not only provide us with direct genetic evidence of miR-146a’s role in the pathogenesis of OA, but also point to agents that can be used to possibly diagnose and/or therapeutically inhibit the progression of OA.

骨性关节炎（osteoarthritis, OA）是一种以关节软骨退变为主要病变的慢性疾病，其发病机制尚不清楚，尚无有效的治疗方法。多项体外研究提示miR-146a影响关节软骨细胞内稳态，但正反结论同时存在，体内实验证据尚无报道。前期实验发现，人OA软骨中miR-146a表达水平明显减少，miR-146a敲除鼠的关节过早出现OA样改变。故推测miR-146a抑制关节软骨及关节滑膜的Notch1及其下游的炎性因子IL-6，从而保护减缓OA的发生与发展进程。本课题结合miR-146a表达缺失和表达获得的小鼠模型，采用原发性OA和手术诱导OA的动物模型，从整体到细胞层次阐明本课题组的假说，为阐明miR-146a影响OA发生和发展的机理提供体内实验证据。本项目的完成将为miR-146a对维持关节软骨内稳态提供直接的基因学证据，也有助于我们研发产品用于OA的诊断和治疗。

骨性关节炎是一种以关节软骨退变为主要病变的慢性疾病，其发病机制不清楚，尚无有效的治疗方法。微小核糖核酸是内源性非蛋白编码单链小分子RNA，多项研究报道miR-146a 参与软骨细胞新陈代谢及维持软骨细胞的正常功能。但其在OA发生和发展的作用不详且缺乏体内实验研究。本研究结合miR-146a基因敲除鼠和野生鼠以及软骨过表达miR-146a转基因鼠杂交实现基因缺失和功能获得，采用OA的动物模型及IL-1β处理的细胞模型，从整体到细胞层次验证假说，为阐明miR-146a影响OA发生和发展提供体内实验证据。通过原发性OA模型及内侧半月板切除的手术模型首次发现：MiR-146a基因缺失加剧原发性及手术诱导的关节炎症与关节退变, 而小鼠软骨组织特异性过表达miR-146a（Col2a1-Cre; miR-146a）减低关节炎性反应并延迟OA的发生发展。我们运用基因克隆技术及免疫蛋白印迹确定了Notch1在关节软骨细胞是miR-146a的靶分子，并进而在细胞及整体水平用Notch1抑制剂验证及采用基因工程手段阐明体内调节miR-146a水平足够阻断miR-146a基因缺失引起的OA提前发生。综上所述，我们的研究结果表明软骨细胞的miR-146a在OA 发生发展中是一种重要保护因子，miR-146a抑制关节软骨及关节滑膜的Notch1及其下游的炎性因子IL-6，从而保护减缓软骨退变的进程。本课题组的研究成果不仅有助于明确miR-146a在调控软骨合成和分解代谢方面的功能，并通过提高miR-146a表达或者外源性给予miR-146a来减慢软骨退变与恢复正常的软骨代谢平衡。因此，本项目具有重要的实际应用价值，为OA的防治提供新思路与新靶点。