Synergistic RNA therapy for scar reduction: co-delivery mRNA and siRNA attenuates MDA5/RIG-I activation to enhance anti-fibrotic efficacy.

Fibrotic diseases including corneal scarring and hypertrophic skin scarring cause visual impairment, disfigurement, and functional limitations with limited clinical therapeutic options. mRNA-based therapies are promising but hampered by the intrinsic immunogenicity of mRNA-loaded lipid nanoparticles. Here, we developed a LNP-mediated co-delivery system (Co-delivery@LNPs) encapsulating ID3 mRNA and MMP9 siRNA. Then, Co-delivery@LNPs were synthesized, characterized, and evaluated in cellular and animal fibrotic models. ID3 mRNA delivered by LNPs exerted therapeutic effects but activated pattern recognition receptors (MDA5/RIG-I) and downstream inflammatory pathways. Notably, co-delivered MMP9 siRNA inhibited NF-κB p65 and p38 MAPK, thus suppressing MDA5/RIG-I activation. This resulted in a 1.63-fold increase in detected ID3 mRNA levels and approximately 3.2-fold greater reduction in MMP9 mRNA levels compared with single-delivery groups in keratocytes. Co-delivery@LNPs synergistically suppressed TGF-β1-induced fibrosis by downregulating TGF-β1, α-SMA, Col III, and PDGF-BB. Co-delivery@LNPs significantly alleviated corneal scarring in Brown Norway rats and exerted robust anti-scarring effects in mouse hypertrophic skin scars. This study represents the first LNP-mediated co-delivery of ID3 mRNA and MMP9 siRNA, which not only provides a promising strategy for fibrotic diseases with efficacy in both corneal and skin scarring models, but also offers a novel solution to alleviate exogenous mRNA immunogenicity.