Annexin A5 Derived from Cell-free Fat Extract Attenuates Osteoarthritis via Macrophage Regulation.

Osteoarthritis (OA) is a challenging degenerative joint disease to manage. Previous research has indicated that cell-free fat extract (CEFFE) may hold potential for OA treatment. This study investigated the role of Annexin A5 (AnxA5) within CEFFE in regulating macrophage polarization and protecting chondrocytes. In vitro experiments demonstrated that AnxA5 effectively inhibited M1 macrophage polarization by facilitating toll-like receptor (TLR) 4 internalization and lysosomal degradation through calcium-dependent endocytosis. This process decreased TLR4 expression, suppressed pro-inflammatory mediator release, and reduced the production of reactive oxygen species. Furthermore, AnxA5 displayed protective effects against chondrocyte necrosis and apoptosis. In vivo, studies revealed that intra-articular administration of AnxA5 ameliorated pain symptoms in a monosodium iodoacetate-induced osteoarthritis rat model. Histological analyses indicated a decrease in synovial inflammation and mitigation of cartilage damage following AnxA5 treatment. These results underscored the potential of AnxA5 as a therapeutic option for OA due to its capacity to regulate macrophage polarization and maintain chondrocyte viability. Further investigation into the specific mechanisms and clinical applications of AnxA5 may help improve the management of OA.