Local and Systemic siRNA Drug Delivery Strategies for the Treatment of Arthritis

Abstract

Osteoarthritis (OA) is a debilitating and prevalent chronic joint disease. Matrix metalloproteinase 13 (MMP13) is a key driver of OA, as it degrades collagen type 2 (CII), a key structural ECM component of cartilage. CII degradation fragments increase MMP13 and inflammation, perpetuating this degenerative cycle. Current OA treatments tend to be only palliative in nature and/or are rapidly cleared from the joint. Treatment of multi-joint (MJ) OA or rheumatoid arthritis (RA) is further complicated by the need for systemically delivered therapeutics that selectively hone to afflicted joints. These limitations to arthritis treatment were addressed herein. We engineered endosome-escaping siMMP13 nanoparticles (siMMP13-NPs) embedded within PLGA microplates (uPLs) to create siMMP13-NP delivering microplates (siMMP13-μPLs). A single intra-articular injection of siNPs-µPLs provided sustained retention within the joint for up to at least 25 days, meanwhile free siNPs were only visualized 1 day after injection. In vivo studies demonstrated that a single intra-articular injection of siMMP13-μPLs achieved 65-75% MMP13 gene knockdown over a 28-day study with consequently reduced MMP13 protein leading to protected articular cartilage integrity, improved total joint histopathology, reduced ectopic mineralization, lessened osteophyte formation, and reduction of inflammatory markers. Lastly, we optimized MMP13 siRNA stability, and modified the siRNA with albumin-binding lipid tails (siRNA<(EG18L)2), enabling accumulation within the albumin-enriched microenvironment of arthritic joints following systemic delivery. Modifications of the siRNA, including 2′-OMe and 2′-F ribosugar modifications and phosphorothiate linkages on the backbone, protected against endo- and exonucleases, respectively, while the lipid conjugates interacted strongly with the albumin-enriched synovial fluid of OA and RA patients. siMMP13<(EG18L)2 accumulated in OA mouse knees, was retained for at least 30 days, and accumulated in multiple joints in a mouse model of RA. Histology demonstrated cellular siRNA-lipid uptake within cartilage and synovium of affected joints. Importantly, the elevated MMP13 seen in OA and RA models was diminished upon treatment decreasing clinical manifestations of arthritis, diminishing markers of inflammation, and decreasing synovial inflammation and cartilage destruction. Together, these data demonstrate the utility of nano-in-micro and albumin ‘hitchhiking’ for siRNA delivery and retention in arthritic joints, the therapeutic promise of MMP13 targeting, and the extra-hepatic therapeutic potential of siRNA.