Abstract 620: miRNA Nanoparticles Targeting Cholesterol Efflux: a Promising Tool for the Treatment of Atherosclerosis

The prevention and treatment of cardiovascular diseases (CVD) has largely focused on lowering circulating LDL cholesterol, yet a significant burden of atherosclerotic disease remains even with low LDL. Recently, microRNAs (miRNAs) have emerged as exciting therapeutic targets for CVD. miRNAs are small noncoding RNAs that post-transcriptionally regulate gene expression by degradation or translational inhibition of target mRNAs. A number of miRNAs have been found to modulate all stages of atherosclerosis, particularly those that promote cholesterol efflux from lipid laden macrophages in the vessel wall. However, one of the major challenges of miRNA-based therapy is to achieve tissue-specific, efficient and safe delivery of miRNAs in vivo . Objective: We therefore sought to develop chitosan/miRNA nanoparticles, deliver them to the plaque, and determine if these miRNAs can promote cholesterol efflux to decrease atherosclerosis. Results: We conjugated negatively charged miRNAs with tripolyphosphate (TPP) to support crosslinks between polymeric and nucleic acid units, which were then mixed with varying ratios of chitosan polymer to form nanoparticles that ranged from 150-180nm in size. We next optimized the efficiency of intracellular delivery of different chitosan/miRNA ratios to mouse macrophages (MΦ). We find chitosan nanoparticles can protect as well as transfer exogenous miR-33 to naïve MΦ and reduce mRNA and protein expression of its target gene, ABCA1, confirming that miRNAs delivered via nanoparticle can escape the endosomal system and function in the RISC complex. Because ABCA1 plays a key role in stimulating the efflux of cholesterol from MΦ, we also confirmed that MΦ treated with chitosan/miR-33 nanoparticles exhibited reduced cholesterol efflux to Apolipoprotein A1, further confirming functional delivery of the miRNA. Using this formulation, we have developed a panel of miRNA nanoparticles delivering miRNAs that enhance ABCA1 expression and promote cholesterol efflux. Conclusions: miRNAs can be efficiently delivered to macrophages via nanoparticles where they can function to regulate ABCA1 expression and cholesterol efflux, suggesting that these miRNA-nanoparticles can be used in vivo to target atherosclerotic lesions.