Extracellular vesicles derived from aspirin-treated macrophages promote osteochondral tissue regeneration

Despite significant advancements in osteochondral tissue engineering, the treatment of osteochondral defect remains a challenging clinical issue due to the limited availability of seed cells and persistent inflammation at the defect site. Modulating the local immune microenvironment can facilitate tissue repair. Herein, we prepared extracellular vesicles (EVs) derived from aspirin-treated M₁ macrophages (A-EVs) and loaded them into a thermosensitive hydrogel composed of mono-functional polyhedral oligomeric silsesquioxane (MPOSS), polyethylene glycol (PEG), and polypropylene glycol (PPG) (mPEP). This hydrogel formulation serves as a sustained-release system for A-EVs. More importantly, the A-EVs showed the capacity to promote in vitro polarization of M₁ to M₂-like macrophages and mesenchymal stem cells (MSCs) chondrogenesis, which significantly promote in vivo osteochondral regeneration compared to EVs from untreated M₁ macrophages (1-EVs) without the use of exogenous cells and growth factors. Dual-luciferase assay revealed that aspirin can reprogram the M₁ macrophage through PPARα/NF-κB. The miRNA microarray analysis showed that multiple miRNAs (e.g., miR-127, miR-132 and miR-155, especially miR-140) in A-EVs can activate multiple signaling pathways related to repolarization of macrophages and MSC chondrogenesis. In summary, this study reveals a novel therapeutic application for aspirin in managing osteochondral defects through macrophage-derived EVs, preventing the issue of delayed healing by using aspirin directly.