骨关节炎状态下PTH/PTH1R-SOX9信号轴对下颌髁突软骨干细胞的调控机制研究

In temporal mandibular joint osteoarthritis (TMJOA), to find the target cells for cartilage regeneration and to activate their function is of great importance. The condylar fibrocartilage stem cells (FCSCs) is a potential seed cell type for cartilage repair in TMJOA, while the mechanism of their function during OA has not been systemically clarified yet. Previous studies suggested PTH/PTH1R as a crucial mediator during OA cartilage repairing, which regulates the chondrogenic transcription factor SOX9, as well as to direct stem cell differentiation. Our preliminary data showed PTH up-regulated SOX9 expression, as well as the chondrogenic markers (aggrecan, col2) in FCSCs. According to these data, our first goal of this project is to describe the mechanistic role of PTH/PTH1R in SOX9 transcriptional function in FCSCs by using ChIP-Seq analysis. Then we will further study SOX9 functional inhibitory effect to FCSCs under OA circumstances. Finally, we will perform lineage tracing study of FCSCs in TMJOA transgenic mouse model and investigate the function of PTH/PTH1R-SOX9 signaling in FCSCs and its mechanism in TMJOA cartilage repairing. These scientific questions might bring new insight for future clinical treatment of TMJOA.

在颞下颌关节骨关节炎（TMJOA）中，寻找参与软骨退行性变延缓与修复的靶细胞并启动其修复机制是突破该疾病治疗瓶颈的关键。髁突软骨干细胞（FCSCs）是损伤软骨修复的种子细胞之一，但其功能受何种机制调控尚未阐明。以往研究提示PTH/PTH1R能够影响成软骨分化关键转录因子SOX9表达，同时具有调控干细胞命运促使其定向分化的作用，是调节FCSCs参与损伤软骨修复的潜在通路。申请人前期实验发现PTH可上调FCSCs中SOX9表达，同时激活FCSCs成软骨活性。本项目拟通过免疫共沉淀结合高通量测序研究PTH/PTH1R对FCSCs中SOX9成软骨转录功能的调节机制；明确炎症状态下SOX9功能抑制对FCSCs特性改变的影响；通过转基因小鼠FCSCs谱系追踪深入探索PTH经SOX9介导调控FCSCs参与TMJOA软骨修复的分子机制，最终为寻求临床上TMJOA治疗的新靶点和新策略提供理论与数据支持。

本课题主要对PTH/PTH1R-SOX9信号轴在髁突软骨干细胞（Fibrocartilage stem cells,FCSCs）参与颞下颌关节（Temporomandibular joint,TMJ）软骨发育与骨关节炎（Osteoarthritis,OA）损伤修复进程中的细胞分子机制进行研究。发现PTH激活改变髁突FCSCs增殖、凋亡、成软骨向分化等细胞特性。同时发现FCSCs在向SOX9+细胞定向分化过程表现出显著的时空表达变化规律。课题组进而对人类来源FCSCs(hFCSCs)的干细胞特性进行观察，发现成软骨转录因子SOX9的表达激活与抑制对炎症环境下hFCSCs的增殖、凋亡以及成软骨向分化起关键调控作用。采用Gli1-CreER+;Rosa-tdTomatofl/fl谱系示踪小鼠模型，观察到经TNF/Nf-κB炎症靶向抑制能够有效激活TMJOA状态下Gli1+FCSCs干细胞潜能，促使其更广泛地向SOX9+成软骨前体细胞定向分化，从而发挥延缓TMJOA软骨破坏的作用。以保留颞下颌关节干细胞潜能为理论基础，结合临床实践，指导髁突陈旧性骨折/颞下颌关节强直患者的临床治疗，建立充分保留髁突FCSCs潜能的关节外科治疗新策略。