Extracellular vesicles derived from synovial inflammatory macrophages induce the onset of osteoarthritis in a FMRP-selectively sorted manner

Osteoarthritis (OA) is an aging-related degenerative joint disease without effective therapeutic. In the early stage of OA, mild synovitis has been proven to induce normal cartilage lesions. However, the mechanism is poorly defined. Here, we identified that the extracellular vesicles (EVs) derived from synovial inflammatory macrophages regulate the autophagy function of chondrocytes, acting as the dominant inducer of the onset of cartilage degeneration in normal and OA joints. Mechanistically, the active transfer of miR-155-5p via EVs from synovial inflammatory macrophages to chondrocytes accelerates cartilage degeneration by suppressing GSK 3β/mTORC1 axis-mediated autophagy function during OA progression.