Rapgef3 modulates macrophage reprogramming and exacerbates synovitis and osteoarthritis under excessive mechanical loading

Evidences indicate that mechanical loading plays an important role in osteoarthritis (OA) progression, while the specific pathological changes of the synovium under excessive mechanical loading are unclear. Results showed excessive mechanical loading caused pro-inflammatory of synovial macrophages, which has been confirmed to exists in OA. High Rapgef3 expression level was found in RNA sequencing of RAW246.7 subjected to 0.5Hz-20%-cyclic tensile strain. We verified this in the synovium of OA patients and DMM-OA mice. Interestingly, the Rapgef3 content of chondrocytes was very low. Primary chondrocytes treated with Rapgef3 alone did not show metabolic phenotype, but an OA phenotype appeared when treated with Rapgef3-stimulated macrophage culture supernatant. Mechanically, excessive mechanical loading activated p65-NF-?B pathway through Rapgef3, which promoted the inflammatory of macrophage, resulting in severe articular cartilage injury. Intra-articular Rapgef3 knockout reversed synovitis and cartilage degeneration, which might provide a therapeutic target for osteoarthritis. Overall design: differentially expressed in RAW246.7 cells treated with normal and 20% elongation strain loading for 24 hours