Extracellular matrix (ECM) stiffening is a typical characteristic of cartilage aging, which is a quintessential feature of knee osteoarthritis (KOA). However, little is known about how ECM stiffening affects chondrocytes and other molecules downstream. This study mimicked the physiological and pathological stiffness of human cartilage using polydimethylsiloxane (PDMS) substrates. It demonstrated that epigenetic Parkin regulation by histone deacetylase 3 (HDAC3) represents a new mechanosensitive mechanism by which the stiffness matrix affected chondrocyte physiology. We found that ECM stiffening accelerated cultured chondrocyte senescence in vitro, while the stiffness ECM downregulated HDAC3, prompting Parkin acetylation to activate excessive mitophagy and accelerating chondrocyte senescence and osteoarthritis (OA) in mice. Contrarily, intra-articular injection with an HDAC3-expressing adeno-associated virus restored the young phenotype of the aged chondrocytes stimulated by ECM stiffening and alleviated OA in mice. The findings indicated that changes in the mechanical ECM properties initiated pathogenic mechanotransduction signals, promoted the Parkin acetylation and hyperactivated mitophagy, and damaged chondrocyte health. These results may provide new insights into chondrocyte regulation by the mechanical properties of ECM, suggesting that the modification of the physical ECM properties may be a potential OA treatment strategy.

细胞外基质（ECM）硬化是软骨老化的典型特征，也是膝骨关节炎（KOA）的典型特征。然而，人们对 ECM 硬化如何影响软骨细胞和下游其他分子知之甚少。这项研究使用聚二甲基硅氧烷 (PDMS) 基材模拟了人类软骨的生理和病理硬度。结果表明，组蛋白脱乙酰酶 3 ( HDAC3 ) 对 Parkin 的表观遗传调节代表了一种新的机械敏感机制，硬度矩阵通过该机制影响软骨细胞生理学。我们发现，ECM 硬化加速了体外培养的软骨细胞的衰老，而僵硬的 ECM 下调了 HDAC3，促使 Parkin 乙酰化激活过度的线粒体自噬，加速小鼠软骨细胞衰老和骨关节炎 (OA)。相反，关节内注射表达 HDAC3 的腺相关病毒可恢复 ECM 硬化刺激的衰老软骨细胞的年轻表型，并减轻小鼠的 OA。研究结果表明，机械 ECM 特性的变化引发了致病性机械转导信号，促进 Parkin 乙酰化和过度激活的线粒体自噬，并损害软骨细胞的健康。这些结果可能为 ECM 机械特性对软骨细胞的调节提供新的见解，表明 ECM 物理特性的改变可能是一种潜在的 OA 治疗策略。