Co-Polymer Carrier with Dual Advantages of Cartilage-Penetrating and Targeting Improves Delivery and Efficacy of MicroRNA Treatment of Osteoarthritis.

Osteoarthritis (OA) is a debilitating joint disease affecting nearly 400 million people with no efficient etiological therapies. OA is primarily identified by cartilage destruction, and gradual degeneration of the whole joint would happen when the OA progresses. Hence, cartilage has been identified as the primary therapeutic target of OA. Unfortunately, numerous barriers block the delivery of therapeutic agents into cartilage, including avascular traits and high hardness of the extracellular matrix. Herein, a cartilage-targeting peptide (CAP) modified polyvinylamine (PVAm)- poly (lactic-co-glycolic acid) (PLGA) copolymer (CAP-PVAm-PLGA) is designed, which can form spherical nanoparticles with the r-miR-140 (CPP-NPs). CPP-NPs possessed enhanced mechanical properties due to the introduction of PLGA to vehicles. Meanwhile, CAP endowed the cartilage targeting which facilitated CPP-NPs localization in cartilage. With such dual advantages, CPP-NPs exhibited outstanding penetrability and accumulation in cartilage even subchondral bone, and can penetrate to a depth of 1000 µm into human cartilage. The degeneration area of cartilage is reduced by 65% and synovial inflammation score by 80% in OA mice, and the microarchitecture of subchondral bone is also ameliorated. These studies established a promising platform for therapeutic RNA delivery in OA therapy that overcame the cartilage barriers.

Polyvinylamine with moderate binding affinity as a highly effective vehicle for RNA delivery.

Polymeric carriers for RNA therapy offer potential advantages in terms of low immunogenicity, promoting modifiability and accelerating intracellular transport. However, balancing high transfection efficacy with low toxicity remains challenging with polymer-based vehicles; indeed, polyethyleneimine (PEI) remains the "gold standard" polymer for this purpose despite its significant toxicity limitations. Herein, we demonstrate the potential of polyvinylamine (PVAm), a commodity high-charge cationic polymer used in the papermaking industry and has similar structure with PEI, as an alternative carrier for RNA delivery. High levels of transfection of normal, tumor, and stem cells with a variety of RNA cargoes including small interfering RNA (siRNA), microRNA (miRNA), and recombinant RNA can be achieved in vitro under the proper complex conditions. While, both the anti-tumor effect achieved in a xenograft osteosarcoma model and lipid-lowering activity observed in a hyperlipidemia mice indicate the potential for highly effective in vivo activity. Of note, both the transfection efficiency and the cytotoxicity of PVAm compare more favorably with those of PEI, with PVAm offering the additional advantages of simpler purification and significantly lower cost. In addition, the mechanism for the difference in transfection efficiency between PVAm and PEI is explored by molecular docking as well as analyzing the process of association and dissociation between polymers (PVAm and PEI) and nucleic acids. Our research provides a novel, non-toxic, and cost-effective carrier candidate for next generation RNA therapy, and elucidates the potential mechanism of PVAm for its efficient delivery of RNA.