Deficiency of TLR4 homologue RP105 aggravates outward remodeling in a murine model of arteriovenous fistula failure

Arteriovenous access dysfunction is a major cause of morbidity for hemodialysis patients. The pathophysiology of arteriovenous fistula (AVF) maturation failure is associated with inflammation, impaired outward remodeling (OR) and intimal hyperplasia. RP105 is a critical physiologic regulator of TLR4 signaling in numerous cell types. In the present study, we investigated the impact of RP105 on AVF maturation, and defined cell-specific effects of RP105 on macrophages and vascular smooth muscle cells (VSMCs). Overall, RP105(−/−) mice displayed a 26% decrease in venous OR. The inflammatory response in RP105(−/−) mice was characterized by accumulation of anti-inflammatory macrophages, a 76% decrease in pro- inflammatory macrophages, a 70% reduction in T-cells and a 50% decrease in MMP-activity. In vitro, anti-inflammatory macrophages from RP105(−/−) mice displayed increased IL10 production, while MCP1 and IL6 levels secreted by pro-inflammatory macrophages were elevated. VSMC content in RP105(−/−) AVFs was markedly decreased. In vitro, RP105(−/−) venous VSMCs proliferation was 50% lower, whereas arterial VSMCs displayed a 50% decrease in migration, relative to WT. In conclusion, the impaired venous OR in RP105(−/−) mice could result from of a shift in both macrophages and VSMCs towards a regenerative phenotype, identifying a novel relationship between inflammation and VSMC function in AVF maturation.