<p>Macrophages play a pivotal role in modulating inflammation and osteoclastogenesis during the progression of rheumatoid arthritis (RA). Although local mRNA-mediated gene editing offers high precision and efficiency, there remains a lack of robust strategies tailored for effective editing of synovial macrophages. Here, we identified RhoA as a macrophage target <i>via</i> bioinformatics, validated its therapeutic potential, and built a heparinylated LNP-microsphere system (hLNP-RhoA^−/−@MS) to replace PEGylated LNPs for in situ RhoA editing. Specifically, a low-molecular weight heparin-cholesterol conjugate was employed in place of PEG during LNP formulation. Substituting PEG with heparin on the LNP surface markedly enhanced the transfection efficiency of delivered mRNA/sgRNA. In parallel, integration of the microsphere system substantially improved LNP stability and intra-articular retention. In vitro RNA-seq analysis revealed broad and significant suppression of multiple key inflammation-related signaling pathways following RhoA editing. In the RA mouse model in vivo, hLNP-RhoA^−/−@MS conferred pronounced therapeutic benefits, including attenuation of joint inflammation, inhibition of cartilage and bone destruction, and remodeling of the immune microenvironment, thereby demonstrating strong anti-RA efficacy. Overall, we present a feasible, effective local mRNA editing strategy for precise modulation of synovial macrophages in RA.</p> Graphical Abstract <p></p>