The Role of Iex-1 in the Pathogenesis of Venous Neointimal Hyperplasia Associated with Hemodialysis Arteriovenous Fistula

Abstract

Arteriovenous fistulas (AVFs) used for hemodialysis fail because of venous neointimal hyperplasia (VNH). There are 1,500,000 patients that have end stage renal disease worldwide and the majority requires hemodialysis. In the present study, the role of the intermediate early response gene X-1 (IEX-1), also known as IER-3 in the pathogenesis of VNH was evaluated. In human samples removed from failed AVF, there was a significant increase in IEX-1 expression localized to the adventitia. In Iex-1 −/− mice and wild type (WT) controls, chronic kidney disease was induced and an AVF placed 28 days later by connecting the carotid artery to jugular vein. The outflow vein was removed three days following the creation of the AVF and gene expression analysis demonstrated a significant decrease in vascular endothelial growth factor-A (Vegf-A) and monocyte chemoattractant protein-1 (Mcp-1) gene expression in Iex-1 −/− mice when compared to WT mice (P<0.05). At 28 days after AVF placement, histomorphometric and immune-histochemical analyses of the outflow vein demonstrated a significant decrease in neointimal hyperplasia with an increase in average lumen vessel area associated with a decrease in fibroblast, myofibroblast, and Ly6C staining. There was a decrease in proliferation (Ki-67) and an increase in the TUNEL staining in Iex-1 KO mice compared to WT. In addition, there was a decrease in Vegf-A, Mcp-1, and matrix metalloproteiniase-9 (Mmp-9) staining. Iex-1 expression was reduced in vivo and in vitro using nanoparticles coated with calcitriol, an inhibitor of Iex-1 that demonstrated that Iex-1 reduction results in decrease in Vegf-A. In aggregate, these results indicate that the absence of IEX-1 gene results in reduced VNH accompanied with a decrease in proliferation, reduced fibroblast, myofibroblast, and Ly6C staining accompanied with increased apoptosis mediated through a reduction in Vegf-A/Mcp-1 axis and Mmp-9. Adventitial delivery of nanoparticles coated with calcitriol reduced Iex-1 and VNH.

New Insights into Dialysis Vascular Access: Molecular Targets in Arteriovenous Fistula and Arteriovenous Graft Failure and Their Potential to Improve Vascular Access Outcomes

“…Finally, a small pilot study using adventitial delivery of calcitriol, a 1,25-dihydroxyvitamin D3 and inhibitor of Iex-1, at the time of angioplasty showed reduction in venous stenosis formation (75). Similar results have been observed experimentally in Iex-1 knockout mice with AVF (76).…”

CD44 Promotes Inflammation and Extracellular Matrix Production During Arteriovenous Fistula Maturation

“…30 With a similar jugular-to-carotid AVF model in mice with chronic renal failure, Misra reported lex-1 regulates MCP-1, with lex-1 KO mice having reduced MCP-1 and neointimal hyperplasia. 31 Our data shows no increase in MCP-1 RNA and protein expression, as well as fewer MCP-1-positive cells, in the AVF of CD44 KO mice (Figure 3), suggesting that one function of CD44 is to promote macrophage accumulation in the maturing AVF limb. However, it is also noteworthy that the increase in macrophages at day 21 is preceded by increased MCP-1 expression at day 7 (Figure 3).…”

The Role of Repeat Administration of Adventitial Delivery of Lentivirus-shRNA-Vegf-A in Arteriovenous Fistula to Prevent Venous Stenosis Formation

“…Recently, elastin deposition within experimental fistulas has been described [19]. Local pharmaceutical delivery has been felt to be a potential strategy for treating access failure [9, 10, 20]. In fact, adventitial delivery of blood outgrowth endothelial progenitor cells has been shown to alleviate vascular injury associated with hemodialysis vascular access grafts [21].…”

“…Fourteen days later, the same therapy was repeated using a separate surgical procedure [8]. Previously, experiments conducted using this technique have shown that venous stenosis forms in this model at the outflow vein [5–7, 9–11]. Seventy-nine male C57BL/6 mice weighing 25–30 grams underwent nephrectomy.…”