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P&F Grant Awards

Year 8

Grant # 16

Peptide-siRNA Nanotherapeutics for Osteoarthritis Treatment.

PI: Christine Pham, MD


Specific Aims

The long-term goal of this project is to develop safe, highly specific and readily translational nanomedicine platforms for the treatment of osteoarthritis (OA). OA represents the most common form of arthritis and a major cause of morbidity in the aging population.1 The annual health care burden for OA is 185 billion dollars, reflecting its very high prevalence and negative quality of life impact.2 OA is a progressive disease for which there are limited treatment options and no disease-modifying drugs. Critical barriers to the development of a successful treatment for OA lie in the fact that the pathways governing early cartilage degeneration have remained largely unexplored. Far from being a “wear and tear” process the current paradigm suggests that, in human OA, ongoing inflammation contributes to disease pathogenesis and progression.3 There is also growing awareness that autophagy regulates cartilage homeostasis and dysregulation of this pathway may negatively impact chondrocyte survival and cartilage repair.4 We posit that modulation of inflammation and autophagy will suppress chondrocyte death, prevent cartilage degeneration and eventually halt or retard OA development.

Much interest has focused on the role of inflammatory cytokines, especially TNF-α and IL-1β, in the pathogenesis of OA. These cytokines play a major role in inflammation and cartilage degeneration by modulating events leading to chondrocyte catabolism and, ultimately, apoptosis. NF-κB is a signaling pathway that controls the expression of gene products involved in myriad cellular responses and is essential for the expression of TNF-α, IL-1β in OA synovium and chondrocytes.5 Thus, we posit that the NF-κB pathway represents an attractive therapeutic target for OA. However, the indiscriminate systemic blockade of NF-κB poses significant risks, given its central role in host immune responses.5 Targeted strategies to silence NF-κB only in affected joints, which might avoid systemic unwanted effects, are highly desirable. However, the historical challenge of safely delivering therapeutic siRNA in effective doses to selected pathologies with targeted transport systems is well known. We employed a novel peptidic nanoparticle (NP) structure that features an amphipathic, cationic, cell penetrating peptide as an siRNA carrier that is stable in biological fluids and enables coordinated endosomal escape and release of siRNA into cytoplasm to rapidly engage the RISC complex and simultaneously suppress both canonical and noncanonical NF-κB activities.6,7 The entire complex can be formed within as little as ten minutes by a simple mixing procedure that allows noncovalent, selfassembly of cationic and anionic moieties into a ~55 nm nanocomplex. The self-assembling nanocomplexes suppress inflammation in a preclinical model of rheumatoid arthritis (RA) by down-regulating NF-κB p65 expression specifically in the joints without affecting p65 expression or host immune responses in offtarget organs, even after serial injections.8 These nanocomplexes, when injected intra-articularly (i.a.), suppress p65 activation and protect against early chondrocyte apoptosis and synovitis in a novel OA model that mimics traumatic joint injury.9 Moreover, our data suggest that NF-κB siRNA nanotherapy partially preserved cartilage integrity by protecting against the impact-injury-induced downmodulation of autophagy in chondrocytes.

Specific Aim #1. In vivo suppression of experimental OA with peptide-NF-κB siRNA nanocomplexes. To examine the long-term outcome of nanotherapy we will use the Destabilization of the Medial Meniscus ligament (DMM), a well-accepted model to generate slowly progressing OA that approximates the primary disease in humans.10 We will use this model to test the hypothesis that periodic intra-articular delivery of peptide-NF-κB siRNA nanocomplexes will halt or retard cartilage degeneration in OA. We will also incorporate chondrocyte/cartilagetargeting ligands to test for enhanced local accumulation/therapeutic benefit.

Specific Aim #2. Suppression of OA with combination of NPs that silence NF-κB and modulate autophagy. Autophagy is a key cellular pathway in the maintenance of cartilage homeostasis. Recent evidence suggests that autophagic dysfunction may negatively impact chondrocyte survival, contributing to OA development.11 There also exists a complex interplay between autophagy and NF-κB signaling pathways. We hypothesize that combination of nanomedicines that suppress NF-κB activation and induce autophagy may significantly improve the efficacy of OA treatment.