Endothelial nitric oxide synthase (eNOS) mediates neointimal thickness in arteriovenous fistulae with different anastomotic angles in rats

Abstract

Background: It is known that the anastomotic angle can influence neointimal hyperplasia and patency in arteriovenous fistulae (AVF). Endothelial nitric oxide synthase (eNOS) is released from the vascular endothelium and can inhibit neointimal hyperplasia. Therefore, here, we aimed to test the hypothesis that the manipulation of eNOS expression could influence neointimal thickness in a rat AVF model with different anastomosis angles. Methods: Rat carotid artery (inflow, CA) and jugular vein (outflow, JV) AVF were created with acute, blunt, or end-to-end (ETE) anastomosis angles. Aspirin was used to increase eNOS expression in the acute angle group, while N(G)-nitro-L-arginine methyl ester (L-name) was used to decrease eNOS expression in the obtuse angle group. The rats were sacrificed on day 21, and tissues were harvested and analyzed histologically and with immunostaining. Results: A larger anastomosis diameter ( p < 0.016) and smaller neointimal area ( p < 0.01) were observed in the obtuse and end-to-end (ETE) groups compared to in the acute group. In the acute angle group, there were more proliferating cell nuclear antigen (PCNA) and α-actin dual-positive cells ( p < 0.0001) and fewer phospho (p)-eNOS-positive endothelial cells ( p < 0.0001) in the neointima than in the obtuse and ETE angle groups. On treating the acute angle and blunt angle groups with aspirin and L-name, respectively, no significant differences in the neointima/lumen rate were observed ( p = 0.6526) between the groups; however, there were fewer von Willebrand factor (vWF) and p-eNOS dual-positive cells in the obtuse angle group treated with L-name ( p = 0.0045). Conclusions: We demonstrated that eNOS plays an important role in neointimal hyperplasia in AVF with different anastomosis angles; further, eNOS could potentially be used as a therapeutic target in patients with AVF in the future.