Total joint replacement (TJR) is a highly successful surgical procedure however the long-term survivorship is limited by wear of the bearing surfaces. Monocyte Chemoattractant Protein-1 (MCP-1) is the most important chemokine regulating systemic and local trafficking of monocyte/macrophages in inflammation. In vitro, in vivo and tissue retrieval studies have demonstrated a critical role for MCP-1 in wear particle-induced inflammation. The goals of this grant proposal are twofold 1) to develop, functionalize and validate a novel orthopaedic implant nano-coating that will deliver anti-MCP-1 protein therapy to the implant-bone interface and 2) to modulate macrophage polarization at the interface from an M1 (pro-inflammatory) to an M2 (pro- tissue remodeling and angiogenesis) phenotype with local infusion of the anti-inflammatory cytokine Interleukin-4 (IL-4). Both of these strategies will decrease chronic inflammation near the implant, improve bone apposition, and decrease particle-induced bone loss due to continuous local infusion of wear particles using our established in vivo murine model.
Specific Aim #1 : To construct, optimize and validate a local delivery system in which mutant anti-MCP-1 protein (called 7ND protein) is eluted from a titanium rod in vitro.
Specific Aim #2 : To demonstrate that local delivery of 7ND protein decreases systemic macrophage trafficking to the protein eluting titanium implant, thereby improving bone apposition and decreasing peri- implant osteolysis, using the murine continuous polyethylene particle infusion model.
Specific Aim #3 : To demonstrate that transformation of macrophages located at the bone-implant interface in the presence of continuously infused polyethylene particles from an M1 (pro-inflammatory) to an M2 (pro- tissue remodeling and angiogenesis) phenotype with local delivery of IL-4 will decrease bone loss and improve bone apposition adjacent to the implant. The proposed studies aspire to modulate the inflammatory reaction to polymer wear particles using a murine model of continuous polyethylene particle infusion, similar to the clinical scenario in humans. Strategies which target macrophage migration (delivery of a mutant MCP-1 protein near the implant) and alter the phenotype of local peri-implant macrophages to one supporting tissue remodeling and angiogenesis (local infusion of IL-4) will be tested. The techniques of bioluminescence, microCT and micro PET scanning, histology and morphometry will be used to delineate systemic trafficking of macrophages to the particles, the characteristics of the local inflammatory reaction, and development or prevention of osteolysis. Both of the biological strategies proposed are novel, mechanistic and directly translational;they should result in decreased peri-implant inflammation, improved bone apposition and decreased particle-induced bone loss, potentially extending the lifetime of joint replacements.
Total joint replacement (TJR) is a highly successful surgical procedure for end-stage arthritis however the longevity of TJRs is limited by wear of the bearing surfaces. Wear particles stimulate a chronic inflammatory reaction that causes local bone destruction around the implant. The purpose of this grant is to test two novel translational strategies to mitigate particle-associated bone destruction by interfering with inflammatory cell signaling, and transforming the inflammatory cells to cells favoring tissue regeneration. Both strategies have a high likelihood of extending the lifetime of TJRs in humans.
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