Osteoarthritis (OA) is a prevalent joint disease with no effective treatment strategies. Aberrant mechanical stimuli was demonstrated to be an essential factor for OA pathogenesis. Although multiple studies have detected potential regulatory mechanisms underlying OA and have concentrated on developing novel treatment strategies, the epigenetic control of OA remains unclear. Histone demethylase JMJD3 has been reported to mediate multiple physiological and pathological processes, including cell differentiation, proliferation, autophagy, and apoptosis. However, the regulation of JMJD3 in aberrant force-related OA and its mediatory effect on disease progression are still unknown. In this work, we confirmed the upregulation of JMJD3 in aberrant force-induced cartilage injury in vitro and in vivo. Functionally, inhibition of JMJD3 by its inhibitor, GSK-J4, or downregulation of JMJD3 by adenovirus infection of sh-JMJD3 could alleviate the aberrant force-induced chondrocyte injury. Mechanistic investigation illustrated that aberrant force induces JMJD3 expression and then demethylates H3K27me3 at the NR4A1 promoter to promote its expression. Further experiments indicated that NR4A1 can regulate chondrocyte apoptosis, cartilage degeneration, extracellular matrix degradation, and inflammatory responses. In vivo, anterior cruciate ligament transection (ACLT) was performed to construct an OA model, and the therapeutic effect of GSK-J4 was validated. More importantly, we adopted a peptide-siRNA nanoplatform to deliver si-JMJD3 into articular cartilage, and the severity of joint degeneration was remarkably mitigated. Taken together, our findings demonstrated that JMJD3 is flow-responsive and epigenetically regulates OA progression. Our work provides evidences for JMJD3 inhibition as an innovative epigenetic therapy approach for joint diseases by utilizing p5RHH-siRNA nanocomplexes.

骨关节炎（OA）是一种普遍存在的关节疾病，没有有效的治疗策略。异常机械刺激被证明是 OA 发病机制的重要因素。尽管多项研究已经发现了 OA 潜在的调控机制，并专注于开发新的治疗策略，但 OA 的表观遗传控制仍不清楚。据报道，组蛋白去甲基化酶 JMJD3 可介导多种生理和病理过程，包括细胞分化、增殖、自噬和凋亡。然而，JMJD3 在异常力相关 OA 中的调节及其对疾病进展的中介作用仍不清楚。在这项工作中，我们证实了 JMJD3 在体外和体内异常力诱导的软骨损伤中的上调。在功能上，通过其抑制剂抑制 JMJD3，GSK-J4，或通过腺病毒感染sh-JMJD3下调JMJD3可以减轻异常力诱导的软骨细胞损伤。机制研究表明，异常力诱导 JMJD3 表达，然后在 NR4A1 启动子处去甲基化 H3K27me3 以促进其表达。进一步的实验表明，NR4A1 可以调节软骨细胞凋亡、软骨退化、细胞外基质降解和炎症反应。在体内，通过前交叉韧带切断术（ACLT）构建OA模型，验证了GSK-J4的治疗效果。更重要的是，我们采用肽-siRNA 纳米平台将 si-JMJD3 递送到关节软骨中，显着减轻了关节退化的严重程度。综合起来，我们的研究结果表明，JMJD3 具有流动反应性，并在表观遗传上调节 OA 进展。我们的工作为利用 p5RHH-siRNA 纳米复合物抑制 JMJD3 作为一种创新的关节疾病表观遗传治疗方法提供了证据。