Periadventitial Delivery of Simvastatin-Loaded Microparticles Attenuate Venous Neointimal Hyperplasia Associated With Arteriovenous Fistula.

Background Venous neointimal hyperplasia and venous stenosis (VS) formation can result in a decrease in arteriovenous fistula (AVF) patency in patients with end-stage renal disease. There are limited therapies that prevent VNH/VS. Systemic delivery of simvastatin has been shown to reduce VNH/VS but local delivery may help decrease the side effects associated with statin use. We determined if microparticles (MP) composed of cyclodextrins loaded with simvastatin (MP-SV) could reduce VS/VNH using a murine arteriovenous fistula model with chronic kidney disease. Methods and Results Male C57BL/6J mice underwent nephrectomy to induce chronic kidney disease. Four weeks later, an arteriovenous fistula was placed and animals were randomized to 3 groups: 20 μL of PBS or 20 μL of PBS with 16.6 mg/mL of either MP or MP-SV. Animals were euthanized 3 days later and the outflow veins were harvested for quantitative reverse transcriptase-polymerase chain reaction analysis and 28 days later for immunohistochemistical staining with morphometric analysis. Doppler ultrasound was performed weekly. Gene expression of vascular endothelial growth factor-A (), matrix metalloproteinase-9 (), transforming growth factor beta 1 (), and monocyte chemoattractant protein-1 () were significantly decreased in MP-SV treated vessels compared with controls. There was a significant decrease in the neointimal area, cell proliferation, inflammation, and fibrosis, with an increase in apoptosis and peak velocity in MP-SV treated outflow veins. MP-SV treated fibroblasts when exposed to hypoxic injury had decreased gene expression of and . Conclusions In experimental arteriovenous fistulas, periadventitial delivery of MP-SV decreased gene expression of , , and VNH/VS, inflammation, and fibrosis.