Department of Spine Surgery, The Second Xiangya Hospital of Central South University, Changsha, China.
J Cell Physiol. 2020 Jan;235(1):281-293. doi: 10.1002/jcp.28968. Epub 2019 Jun 18.
The inflammatory microenvironment in the joints is one of the critical issues during osteoarthritis (OA) and also the main factor that may aggravate symptoms. Under inflammatory microenvironment, M1 macrophages are activated and produce large numbers of proinflammatory mediators, leading to the production of degradative enzymes, the disturbance of chondrocyte apoptosis and cartilage catabolic processes, and finally the deterioration of OA. In the present study, we reveal that the overexpression of osteopontin (OPN), a cytokine, and a matrix protein involved in arthritis and chondrocyte apoptosis in OA, could exacerbate the inflammatory microenvironment in OA via promoting the production of proinflammation cytokines and the levels of degradative enzymes in M1 macrophages, therefore, enhancing the cytotoxicity of M1 macrophage on chondrocytes. XIST expression significantly increases in OA tissue specimens. XIST serves as a competing endogenous RNA for miR-376c-5p to compete with OPN for miR-376c-5p binding, thus counteracting miR-376c-5p-mediated OPN suppression. XIST knockdown could improve the inflammatory microenvironment in OA via acting on M1 macrophages, subsequently affecting the apoptosis of cocultured chondrocytes. miR-376c-5p inhibition exerts an opposing effect on M1 macrophages and cocultured chondrocytes, as well as significantly reverses the effect of XIST knockdown. As a further confirmation, XIST and OPN mRNA expression significantly increased in OA tissues and was positively correlated in tissue samples. In summary, we provide a novel mechanism of macrophages and the inflammatory microenvironment affecting chondrocyte apoptosis. XIST and OPN might be potential targets for OA treatment, which needs further in vivo experimental confirmation.
关节中的炎症微环境是骨关节炎(OA)的关键问题之一,也是可能加重症状的主要因素。在炎症微环境下,M1 巨噬细胞被激活并产生大量促炎介质,导致降解酶的产生、软骨细胞凋亡和软骨分解代谢过程的紊乱,最终导致 OA 的恶化。在本研究中,我们揭示了细胞因子和基质蛋白骨桥蛋白(OPN)在关节炎和软骨细胞凋亡中的过度表达,可能通过促进 M1 巨噬细胞中促炎细胞因子和降解酶的产生,从而加重 OA 中的炎症微环境,增强 M1 巨噬细胞对软骨细胞的细胞毒性。XIST 在 OA 组织标本中的表达显著增加。XIST 作为 miR-376c-5p 的竞争性内源性 RNA,与 OPN 竞争 miR-376c-5p 的结合,从而抵消 miR-376c-5p 介导的 OPN 抑制。XIST 敲低可通过作用于 M1 巨噬细胞改善 OA 中的炎症微环境,进而影响共培养软骨细胞的凋亡。miR-376c-5p 的抑制对 M1 巨噬细胞和共培养软骨细胞产生相反的作用,并显著逆转 XIST 敲低的作用。进一步证实,XIST 和 OPN mRNA 在 OA 组织中的表达显著增加,且在组织样本中呈正相关。总之,我们提供了一种巨噬细胞和炎症微环境影响软骨细胞凋亡的新机制。XIST 和 OPN 可能是 OA 治疗的潜在靶点,需要进一步的体内实验证实。