Adrb2-Mir29b-Wnt5a通路在TMJ-OA髁突软骨下骨丢失中的作用研究

Osteoarthritis is one of the most severe pathological changes of the patients with temporomandibular disorders (TMD) which is a common disease occurring in the orofacial region. Subchondral bone loss is the important pathogenic factor in the progression of osteoarthritis, but its pathomechanism is still unclear. We for the first time demonstrated that activation of norepinephrine(NE)-β2 adrenergic receptor(Adrb2)signal could promote the secretion of wnt5a by mesenchymal stem cells (MSCs), leading to the subchondral bone loss in the osteoarthritis of temporomandibular joint (TMJ), but the mechanism that NE increased expression of Adrb2 and wnt5a is not clarified. By MicroRNA array, we found that Mir29b is the most down-regulated MicroRNA in the MSCs isolated from the condylar sunchondral bone of TMJ osteoarthritic rats. Our preliminary data showed that activation of Adrb2 signal could suppressed the expression of mir29b, and there are mir29b binding sites in the untranslated regions of Adrb2 and wnt5a. These results indicates that Adrb2-mir29b-wnt5a axis plays an important pathogenetic role in the progression of subchondral bone loss in TMJ osteoarthritis. The present project will use Adrb2 conditional knock-out mice, mir29b manipulating mice and TMJ-OA mice, and their corresponding MSCs to study the effect and mechanisim of Adrb2-mir29b-wnt5a axis in the subchondral bone loss during the early stage of TMJ osteoarthritis. Taken together, this project will on one hand demonstrate the new knowledge on the pathomechanism of early TMJ osteoarthritis, and on the other hand provide novel drug targets for the therapy of TMJ osteoarthritis.

骨关节病（OA）是颞颌关节病的重症表现，软骨下骨丢失是其重要致病因素，但骨丢失机制仍不清楚。我们首先提出并证实：去甲肾上腺素（NE）-β2受体 (Adrb2)信号可促进间充质干细胞（MSC）分泌Wnt5a，介导TMJ-OA髁突软骨下骨丢失，但NE上调MSC Adrb2促进Wnt5a表达的机制仍未阐明。Mir29b是我们通过芯片筛选获得的在TMJOA髁突软骨下骨MSC中显著下调的MicroRNA，预实验结果显示：Adrb2信号活化可下调mir29b；Adrb2及wnt5a非编码区均存在mir29b结合位点。提示Adrb2-mir29b-wnt5a通路可能在TMJOA软骨下骨丢失中发挥关键作用。本项目拟以Adrb2敲除鼠、mir29b调控鼠、TMJOA模型鼠及其MSC为模型，探索上述通路在TMJOA软骨下骨丢失中的调控作用及机制，既为TMJOA病变机制提出新认识，又为发现新的药物靶位提供依据。

骨关节病（OA）是颞颌关节病的重症表现，软骨下骨丢失是其重要致病因素，但骨丢失机制仍不清楚。本项目以Adrb2-mir29b-wnt5a 通路的功能研究为突破口，以Adrb2 条件敲除鼠、mir29b 靶向调控鼠及TMJOA 鼠及它们所对应的骨髓间充质干细胞（MSC） 为模型，从分子、细胞、组织和整体等多种水平系统探讨Adrb2-mir29b-wnt5a 通路在TMJOA 早期髁突软骨下骨吸收中的作用机制。本项目结果显示：①TMJOA组野生小鼠髁突软骨退变及软骨下骨丢失明显，但靶向敲除MSC Adrb2表达后，TMJOA小鼠髁突骨、软骨病变均显著逆转。②miR29b是OA软骨下骨MSC与对照MSC间最显著的差异miR，其在OA组下调33倍。靶向过表达MSC miR29b可显著逆转TMJ-OA骨、软骨病变，而靶向降低MSC miR29b则进一步加重上述病变。③Adrb2信号活化后，可通过激活转录因子c-myc抑制miR29b表达，进而通过直接转录调控作用，促进破骨、破软骨因子Wnt5a表达，最终引起TMJ-OA骨、软骨病变。. 综上所述，本项目结果显示：异常机械应力刺激可激活软骨下骨交感神经信号，促进局部交感递质去甲肾上腺素NE的分泌，NE进而激活Nestin+ MSC的Adrb2受体，从而通过转录因子c-myc抑制miR29b表达，miR29b通过直接转录调控作用，促进破骨、破软骨因子Wnt5a表达，Wnt5a与其受体Ror2结合后，一方面促进软骨降解，另一方面促进破骨细胞的活化，进而导致TMJ-OA髁突骨、软骨病变，而靶向敲除Nestin+ MSC Adrb2或上调其miR29b水平，可显著逆转上述TMJ-OA病变，因此可作为临床逆转TMJ-OA患者髁突病变的有效靶点。. 基于上述研究成果，申请人作为第一或通讯作者发表科研论文15篇（均标注本基金号），其中SCI论文9篇，IF>10的5篇，IF>5的4篇，获批国家发明专利4项，实用新型专利4项。荣获陕西省科技进步一等奖、陕西省科技创新团队、陕西省高校青年创新团队、2017及2020年度陕西省自然科学优秀学术论文二等奖等。

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