Dual-Targeted Inhibition of PAR₂ Endosomal Signaling in Synoviocytes and Nociceptors Attenuates Osteoarthritis Pain

Osteoarthritis (OA) is the most prevalent chronic joint disease characterized by the progressive degeneration of articular cartilage leading to debilitating locomotor restrictions and persistent pain. The pathogenesis of OA is driven by a complex cycle of inflammatory mediators, where G protein-coupled receptor protease-activated receptor 2 (PAR₂) has emerged as a key driver of both tissue degradation and joint inflammation. PAR₂ is expressed on various joint tissues, and on the terminals of nociceptive sensory neurons, providing a direct link to structural joint inflammation and chronic nociception. However, the therapeutic potential of PAR₂ antagonists is hampered by the rapid clearance of drugs from the synovial space. Here, we investigate the therapeutic potential of nanoparticle-mediated drug delivery to achieve sustained PAR₂ inhibition in OA. OA was induced in C57BL/6 mice via intra-articular injection of sodium iodoacetate, followed by treatment with the PAR₂ antagonist, AZ3451, encapsulated within PAMAM-Chol nanoparticles (PAMAM-Chol-AZ3451). Our results demonstrate that the PAMAM-Chol-AZ3451 nanoparticles blocked cytokine release from synoviocytes and provided a significantly more sustained and effective antinociceptive effect compared to the free AZ3451, with confirmed nanoparticle uptake by neurons and synoviocytes. Furthermore, cell-specific genetic deletion confirmed that PAR₂ expressed on Nav1.8 nociceptors is a critical contributor to OA-induced nociception and locomotor deficits. These findings establish that PAR₂ signaling in neurons is critical for OA nociception and that nanoparticle delivery of PAR₂ antagonists (PAMAM-Chol-AZ3451) represents an effective strategy for sustained inhibition of PAR₂ activity, offering a novel approach for managing chronic OA pain.