LncRNA-p21通过β-catenin促进TMJ-OA软骨下骨丢失的机制研究

Osteoarthritis (OA) is the common manifestation of patients with severe temporomandibular disorders, and its important causative factor is subchondral bone resorption, but the mechanism of bone resorption is unknown. Our previous studies on the rat model of temporomandibular joint (TMJ) OA showed that the bone marrow mesenchymal stem cells (BMSC) from TMJ-OA condylar subchondral bone secreted high level of SDF-1 and RANKL, and could significantly promote the migration and activation of osteoclast precursor cells, indicating that BMSC plays an important role in promoting the subchondral bone resorption in TMJOA. Our microarray result showed that LncRNA-p21 was a significantly down-regulated LncRNA in the TMJOA condylar subchondral bone BMSCs comparing to the controls. In addition, overexpression of LncRNA-p21 significantly reversed the pro-osteoclastic effect of BMSC from the TMJOA condylar condyles, while this reversing effect could be blocked by the knockdown ofβ catenin. These results suggested that LncRNA-p21 plays a key role in the subchondral bone loss of TMJOA via β catenin. Using TMJOA mouse and LncRNA-p21 target regulatory mouse and their BMSC as the models, the present project will adopt the cell co-culture method, gene knockdown and overexpression method to study the pathomechanism of LncRNAp21-βcatenin signaling cascade in the development of the resorption of TMJOA condylar subchondral bone. This project will provide for new treatment strategies for TMJOA patients.

骨关节炎（OA）是重症颞下颌关节病患者的常见表现，其重要致病因素为软骨下骨吸收，但骨吸收机制不明。我们前期对颞下颌关节（TMJ）OA样变大鼠研究发现，髁突软骨下骨BMSC在TMJOA早期软骨下骨吸收中发挥重要促破骨效应。LncRNA-p21是我们筛选获得的在TMJOA髁突软骨下骨BMSC中显著下调的LncRNA，预实验显示：过表达LncRNA-p21可显著逆转TMJOA大鼠髁突软骨下骨BMSC的促破骨效应，这一逆转作用可被敲除β‑catenin阻断。提示LncRNA-p21通过β‑catenin在TMJOA软骨下骨丢失中发挥关键作用。本项目拟以TMJOA鼠及LncRNA-p21靶向调控鼠及其BMSC为模型，采用细胞共培养，基因敲除或过表达等技术系统研究LncRNAp21-βcatenin信号级联在TMJOA髁突软骨下骨病变中的作用机制，为临床治疗TMJOA提供新策略。

颞下颌关节骨性关节炎(TMJ-OA)是一种关节退行性疾病。早期表现为髁突软骨下骨异常重塑。其重要致病因素为软骨下骨吸收，但骨吸收机制不明确。在骨组织中，骨髓间充质干细胞(bone marrow mesenchymal stem cells, BMSCs)在大多数造血细胞的分化和成熟中发挥着重要作用。我们通过建立大鼠UAC模型，发现在TMJ-OA中髁突软骨下骨BMSC中促破骨因子的表达有明显升高，且8周组尤为显著。LncRNA-p21是我们通过芯片筛选获得的在TMJ-OA髁突软骨下骨BMSC中显著下调的LncRNA，lncRNA-p21高表达时对 BMSCs 分泌促破骨因子能力有促进作用。为了研究其中的关键调控机制，我们对TMJ-OA 大鼠及同龄对照鼠髁突软骨下骨BMSC进行LncRNA-p21及β-catenin过表达或敲除处理，结果显示当过表达lncRNA-p21的同时过表达β-catenin后，破骨相关因子表达显著升高。为了确定上述体外实验的结果，我们对UAC大鼠同时给予LncRNA-p21过表达病毒的TMJ关节腔注射，结果提示过表达LncRNA-p21可显著逆转TMJ-OA大鼠髁突软骨下骨BMSC的促破骨效应，这一逆转作用可被敲除β-catenin所阻断。本研究的结果表明，在TMJ-OA进展的背景下，lncRNA-p21可以调节异常咬合引起的软骨下骨丢失，并通过β-catenin影响软骨下BMSCs的促破骨效应。在延伸研究中，我们发现体外上调miRNA-26b会引起β-catenin表达水平降低，增强BMSCs成骨向分化水平。此外，在UAC大鼠的颞下颌关节中，miRNA-26b过表达增加了髁突软骨下骨成骨水平，逆转了UAC大鼠颞下颌关节髁突软骨的降解。通过体内与体外实验的方法，我们验证了miRNA-26b-β-catenin级联在TMJ-OA髁突软骨下骨中促进骨髓间充质干细胞成骨向分化，为后续进一步研究TMJOA的发病机制及临床治疗提供了新的策略。