Matrix-targeted Nanoparticles for MMP13 RNA Interference Blocks Post-Traumatic Osteoarthritis.

Osteoarthritis (OA) is a debilitating and prevalent chronic disease, but there are no approved disease modifying OA drugs (DMOADs), only pharmaceuticals for pain management. OA progression, particularly for post-traumatic osteoarthritis (PTOA), is associated with inflammation and enzymatic degradation of the extracellular matrix. In particular, Matrix Metalloproteinase 13 (MMP13) breaks down collagen type 2 (CII), a key structural component of cartilage extracellular matrix, and consequently, matrix degradation fragments perpetuate inflammation and a degenerative cycle that leads to progressive joint pathology. Here, we tested targeted delivery of endosome-escaping, MMP13 RNA interference (RNAi) nanoparticles (NPs) as a DMOAD. The new targeting approach pursued here deviates from the convention of targeting specific cell types (e.g., through cell surface receptors) and instead leverages a monoclonal antibody (mAbCII) that targets extracellular CII that becomes uniquely accessible at early OA focal defects. Targeted mAbCII-siNPs create an in situ NP depot for retention and potent activity within OA joints. The mAbCII-siNPs loaded with MMP13 siRNA (mAbCII-siNP/siMMP13) potently suppressed MMP13 expression (95% silencing) in TNF-stimulated chondrocytes in vitro, and the targeted mAbCII-siNPs had higher binding to trypsin-damaged porcine cartilage than untargeted control NPs. In an acute mechanical injury mouse model of PTOA, mAbCII-siNP/siMMP13 achieved 80% reduction in MMP13 expression (p = 0.00231), whereas a non-targeted control achieved only 55% silencing. In a more severe, PTOA model, weekly mAbCII-siNP/siMMP13 long-term treatment provided significant protection of cartilage integrity (0.45+/- .3 vs 1.6+/-.5 on the OARSI scale; p=0.0166), and overall joint structure (1.3+/-.6 vs 2.8+/-.2 on the Degenerative Joint Disease scale; p View larger version (54K): org.highwire.dtl.DTLVardef@1803795org.highwire.dtl.DTLVardef@c1254dorg.highwire.dtl.DTLVardef@78233eorg.highwire.dtl.DTLVardef@151d96f_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOAbstract Figure:C_FLOATNO PTOA targeted delivery of MMP13 siRNA to block disease progressionThe top left schematic illustrates the progression (left to right) from healthy knee joint, through inflammation induction following traumatic injury, to cartilage loss and degenerative joint disease (including synovial response). Degradation of cartilage enhances inflammation, inducing a degenerative cycle (middle right). The bottom of the graphic illustrates the concept of the matrix targeted nanocarriers for enhanced retention and activity of MMP13 siRNA at sites of cartilage injury. C_FIG