MIF-CD74 orchestrates synovial macrophage metabolic-inflammatory reprogramming by ENO2 interaction to drive osteoarthritis pathogenesis

Synovitis is a central driver of osteoarthritis (OA) progression, yet the cellular and molecular mechanisms sustaining inflammatory circuits in the synovium remain incompletely understood. Through integrative analysis of time-resolved single-cell RNA sequencing in murine synovium and spatial transcriptomics of human OA tissues, we identified a pathogenic CD74⁺ macrophage subset that expands in OA and localizes at the synovial-cartilage interface. This subset exhibits a proinflammatory, nonclassical polarization and displays a metabolic dependency on glycolysis. Multiomics and mechanistic studies revealed that CD74 interacts with the glycolytic enzyme enolase 2 (ENO2). This interaction orchestrates a feed-forward signaling axis wherein CD74/ENO2 facilitates the nuclear translocation of hypoxia-inducible factor 1-α (HIF-1α)/β-catenin dimers, which coactivate glycolytic and inflammatory gene programs, thereby sustaining a metabolically driven inflammatory state. Genetic ablation of CD74 in myeloid cells or its pharmacological blockade mitigated synovitis and cartilage degradation in murine OA models. To translate this axis therapeutically, we developed synovium-targeted cationic lipid nanoparticles decorated with MIF-mimetic peptides (PcLNPs) for the delivery of CD74 siRNA. Intra-articular administration of PcLNPs efficiently targeted CD74⁺ macrophages, attenuated their inflammatory and glycolytic phenotypes, and ameliorated murine OA progression in vivo. Our findings establish the CD74/ENO2/HIF-1α/β-catenin axis as a critical integrator of metabolic reprogramming and inflammation in OA synovitis and present a potential targeted nanotherapeutic strategy for disease modification.