Department of Medical Technology, Graduate School of Health Sciences, Okayama University, 2-5-1, Shikata-cho, Kita-ku, Okayama 700-8558, Japan.
Department of Orthopedic Surgery, Dentistry and Pharmaceutical Sciences, Okayama University Graduate School of Medicine, 2-5-1, Shikata-cho, Kita-ku, Okayama 700-8558, Japan.
Int J Mol Sci. 2024 Nov 6;25(22):11942. doi: 10.3390/ijms252211942.
Osteoarthritis (OA) is a chronic disease affecting over 500 million people worldwide. As the population ages and obesity rates rise, the societal burden of OA is increasing. Pro-inflammatory cytokines, particularly interleukin-1β, are implicated in the pathogenesis of OA. Recent studies suggest that crosstalk between cartilage and synovium contributes to OA development, but the mechanisms remain unclear. Extracellular vesicles (EVs) were purified from cell culture-conditioned medium via ultracentrifugation and confirmed using transmission electron microscopy, nanoparticle tracking analysis, and western blotting. We demonstrated that EVs were taken up by human synoviocytes and chondrocytes in vitro, while in vivo experiments revealed that fluorescent-labelled EVs injected into mouse joints were incorporated into chondrocytes and synoviocytes. EV uptake was significantly inhibited by dynamin-mediated endocytosis inhibitors, indicating that endocytosis plays a major role in this process. Additionally, co-culture experiments with HEK-293 cells expressing red fluorescent protein (RFP)-tagged CD9 and the chondrocytic cell line OUMS-27 confirmed the transfer of RFP-positive EVs across a 600-nm but not a 30-nm filter. These findings suggest that EVs from chondrocytes are released into joint fluid and taken up by cells within the cartilage, potentially facilitating communication between cartilage and synovium. The results underscore the importance of EVs in OA pathophysiology.
骨关节炎（OA）是一种影响全球超过 5 亿人慢性疾病。随着人口老龄化和肥胖率的上升，OA 的社会负担正在增加。促炎细胞因子，特别是白细胞介素-1β，与 OA 的发病机制有关。最近的研究表明，软骨和滑膜之间的串扰有助于 OA 的发展，但机制尚不清楚。通过超速离心从细胞培养条件培养基中纯化细胞外囊泡（EVs），并通过透射电子显微镜、纳米颗粒跟踪分析和 Western blot 进行确认。我们证明 EVs 可以被人滑膜细胞和软骨细胞摄取，而体内实验表明，注射到小鼠关节中的荧光标记 EVs 被整合到软骨细胞和滑膜细胞中。EV 的摄取被网格蛋白介导的内吞抑制剂显著抑制，表明内吞作用在这个过程中起着主要作用。此外，与表达红色荧光蛋白（RFP）标记的 CD9 的 HEK-293 细胞和软骨细胞系 OUMS-27 的共培养实验证实，RFP 阳性 EVs 可以穿过 600nm 但不能穿过 30nm 的过滤器。这些发现表明，软骨细胞释放的 EVs 进入关节液，并被软骨内的细胞摄取，这可能促进了软骨和滑膜之间的通讯。这些结果强调了 EVs 在 OA 病理生理学中的重要性。
