TGF-β/Alk5经β-Catenin调控关节软骨表层细胞衰老在关节软骨稳态维持中的作用及机制研究

Osteoarthritis (OA) is a frequently-occurred disease in the elderly. There is no effective drug for OA. Recent research have been shown that the articular cartilage superficial cells (ACSCs) may contain a population of stem cells, which provid new strategy against OA. We recently found that conditional knockout Alk5 of the ACSCs, the cells present senescent appearance. In addition, the notable of hypertrophy of articular cartilage, the decrease of positive cell labeled by Edu and the increase of apoptosis cells in 4 months old mice, and notable OA phenotypic in 8 months old mice. However, the underlying mechanism is still unclear. Many studies have indicated that there is crosstalk between TGF-β/ALK5 and Wnt/β-Catenin in multiple tissues. Combined with recent advances, we propose a hypothesis that TGF-β/Alk5 through β-catenin regulates the senescence of ACSCs and plays an important role in the homeostasis of the articular cartilage. Based on the hypothesis, we will use Alk5 cKO mice and different OA models, combined with different technologies of cell, molecular biology and other research methods, to study of the mechanisms by which the TGF-β/Alk5 and β-catenin regulates the senescence of ACSCs and plays an important role in the homeostasis of the articular cartilage. Will provide more theorical and experimental basis for finding new approaches to prevent the OA based on Alk5 and anti-senescence.

骨性关节炎(OA)是中老年人常见多发病，目前无有效的治疗手段。近年来研究提示存在一群具有自我复制和自我更新能力的关节软骨表层细胞(ACSCs)，为OA的治疗提供了新的机遇。前期我们发现在ACSCs中敲除Alk5(Alk5 cKO)，细胞呈类似衰老的形态。另外，4月龄关节软骨细胞明显肥大，长时程标记Edu细胞减少；随年龄增加，8月龄小鼠出现严重OA表型，但具体机制不清楚。有报道提示TGF-β与β-Catenin在多个组织/器官中存在串话。结合最新研究进展，我们提出Alk5通过β-catenin调节ACSCs衰老参与OA发生发展的假说。本研究中，我们将利用Alk5 cKO小鼠和多种OA模型，结合细胞、分子生物学等多种研究手段，多层次研究TGF-β/Alk5与β-Catenin在ACSCs衰老及OA发生发展中的作用及其机制。将为从调节Alk5和抗ACSCs衰老的角度来寻找治疗OA的措施提供依据。

骨性关节炎(OA)是中老年人常见多发病，目前无有效的治疗手段。关节软骨表面是关节软骨(AC)的防御结构，也是OA进程中最先受到影响的软骨。Alk5在软骨发育和稳态维持中起重要作用。然而，Alk5信号在关节软骨表面干细胞(ACSCs)中的作用和潜在机制目前尚不清楚。构建ACSCs特异性Alk5缺陷(cKO)小鼠模型，对软骨病理改变进行组织学评价，对原代ACSCs进行SA‐β‐gal，活性氧(ROS)、MitoTracker和LysoTracker染色用于检测与衰老相关的变化。此外，小鼠关节内注射更昔洛韦以限制衰老细胞(SnCs)的有害作用。成功建立在ACSCs中可诱导敲除Alk5的小鼠模型 (Alk5 cKO)，研究发现ACSCs中缺失Alk5加速年龄依赖性和创伤性OA的进展，进一步分析发现ACSCs中Alk5对细胞增殖和数量维持至关重要，ACSCs中缺失Alk5降低细胞的自我更新和分化能力，ACSCs中缺失Alk5细胞呈现衰老表型，关节腔注射GCV缓解ACSCs中缺失Alk5细胞呈现的衰老表型。前期发现 TGF-β1/Alk5 通过 PKA-CREB 信号通路诱导软骨细胞中 PRG4 的表达，进一步机制研究发现 Alk5 cKO 小鼠关节 pSmad3和 PRG4 蛋白的表达显著降低，提示ACSCs 中 Alk5/Smads 可能通过 β-Catenin 影响 ACSCs 的衰老来调节关节软骨稳态。