Hydrogel microspheres loaded with sinomenine and Drynaria rhizome enhance the treatment of rheumatoid arthritis via immune regulation and promoting bone repair

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic synovial inflammation, cartilage destruction, and bone loss. Current therapeutic approaches are often limited by short drug half-life, insufficient local drug release, and substantial systemic side effects.In this study, we developed a composite thermosensitive hydrogel system that integrates in situ gelation, sustained drug release, and multitarget therapeutic effects for localized precision treatment of RA.The system consists of a thermosensitive hydrogel matrix composed of hydroxypropyl methylcellulose (HPMC), hyaluronic acid (HA), and glycerol, in which gelatin methacryloyl (GelMA) hydrogel microspheres are embedded. The microspheres efficiently encapsulate Drynaria rhizome-derived extracellular vesicles (DR-EVs), while sinomenine is incorporated into the thermosensitive hydrogel to enhance anti-inflammatory activity. Characterization by transmission electron microscopy (TEM), scanning electron microscopy (SEM), nanoparticle tracking analysis (NTA), rheological measurements, and Fourier-transform infrared spectroscopy (FTIR) confirmed the intact morphology of DR-EVs, the uniform porous structure of the microspheres, and the favorable thermoresponsive gelation behavior and controllable degradation properties of the composite system. Functional assays revealed that, in vitro, the system effectively suppressed TH17 cell proliferation, promoted Treg cell differentiation, and inhibited M1 macrophage polarization.Meanwhile, it upregulated osteogenesis-related genes (Runx2, BMP2) and inhibited osteoclast formation. In a collagen-induced arthritis (CIA) rat model, the system significantly alleviated joint swelling, restored cartilage and bone architecture, and suppressed the progression of synovial inflammation. In summary, this composite thermosensitive hydrogel system possesses injectability, thermoresponsive behavior, prolonged release capability, and multiple biological activities, offering a safe, efficient, and controllable novel strategy for localized precision therapy of RA.