(17f) siRNA Loaded Lipidoid Nanoparticles for Diabetic Ulcer Treatment

Diabetes is one of the most formidable diseases facing the world today, with the number of patients growing every year. Poor glycemic control yields a host of complications, such as impaired wound healing. This often results in the formation of diabetic foot ulcers, which carry a poor prognosis because they are notoriously difficult to treat. Current therapies do not address the increased infiltration of macrophages to the wound bed, where they overproduce tumor necrosis factor α (TNFα). An inflammatory cytokine, TNFα, promotes fibroblast apoptosis and collagen dismantling, and decreases levels of angiogenesis. In this study, we investigated the potential of RNA interference therapy to reduce the inappropriately high levels of TNFα in the wound bed. Although TNFα is a difficult gene silencing target, our lipidoid nanoparticles potently silence TNFα mRNA and protein expression at siRNA doses of 5 - 100 nM without inducing vehicle-related off-target gene silencing or cell death. We also describe the creation of an in vitro macrophage – fibroblast co-culture model, which reflects the TNFα and monocyte chemotactant protein-1 (MCP-1/CCL2) cross-talk that exists in diabetic wounds. Because TNFα induces fibroblasts to produce MCP-1, we show that silencing TNFα results in a downregulation of MCP-1, which should inhibit the recruitment of additional macrophages to the wound. In co-culture experiments, a single lipidoid nanoparticle dose of 100 nM siTNFα knocked down TNFα production by 64% and MCP-1 by 32%. These data underscore the potential of lipidoid nanoparticle RNAi treatment to inhibit a positive feedback cycle that fuels the pathogenesis of diabetic foot ulcers. Current in vivo work silencing TNFα and MCP-1 in inflamed and non-inflamed mouse wound models is ongoing and promising.