An injectable thermosensitive hydrogel delivering M2 macrophage-derived exosomes alleviates osteoarthritis by promoting synovial lymphangiogenesis

Osteoarthritis (OA) is a prevalent chronic degenerative disease affecting millions worldwide, with current treatment measures lacking efficacy in slowing disease progression. The synovial lymphatic system (SLS) has emerged as a crucial player in OA pathogenesis, with compromised drainage function contributing to disease advancement. Lymphatic endothelial cells (LECs) within the SLS are influenced by synovial macrophages, whose precise impact on LEC function remains unclear. Exosomes released by macrophages may serve as mediators of this interaction, with potential implications for OA progression. Here, we propose that polarized macrophages modulate LEC activity via exosome release in synovial tissue, with M2 macrophage-derived exosomes (M2Exo ) promoting LEC proliferation, migration, and lymphangiogenesis, potentially offering a therapeutic avenue for OA. Moreover, we developed an injectable thermosensitive hydrogel with the characteristic of sustained release of M2Exo for alleviating OA. The hydrogel was prepared by dynamically linking hyaluronic acid (HA) and Pluronic F-127 and loading M2Exo , termed as M2Exo loaded HP hydrogel. The in vitro and in vivo experiments showed that M2Exo loaded HP hydrogel exhibits a controlled release profile of exosomes, thereby efficaciously fostering synovial lymphangiogenesis and enhancing synovial lymphatic drainage functionality under OA conditions, thus alleviating OA progression, and providing promising insights into OA therapeutic strategies.