Regulatory gene-chemokine networks in the formation of hemodialysis AVF stenosis

Mayo Clinic Rochester, Rochester MN

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Abstract

PROJECT SUMMARY/ABSTRACT: More than 435,000 patients in the US have end stage renal disease (ESRD), a population expected to double in the next decade. The long-term goal of this current proposal and research program is to improve the care of patients with ESRD, the vast majority of who use long-term hemodialysis as their mode of renal replacement therapy. These patients require highly functioning vascular access for optimal therapeutic adequacy. Hemodialysis vascular access failure is frequently from venous stenosis secondary to neointimal hyperplasia (VNH). Our preliminary data demonstrate an important role for the Iex-1/Mcp-1 pathway in VNH. We show that: 1. IEX-1 staining is increased in venous stenoses removed from patients with AVF. 2. Venous stenoses in AVF removed from a Iex-1 knockout (KO) mice with chronic kidney disease (CKD) have a significant increase in lumen vessel area, decrease in neointima area with a significant increase in apoptosis, decrease in cellular proliferation, significant reduction in ?-SMA and Ly6C monocyte staining, and a significant decline in MCP-1 and MMP-9 immunostaining. 3. Gene expression of Mcp-1, Fgf-1, and Tgf-? are all significantly decreased in venous segments removed from Iex-1 KO mice implying that Iex-1 decreases fibrotic and inflammatory function. 4. Adventitial delivery of nanoparticles composed of polylactic-co-glycolic acid (PLGA) with calcitriol significantly reduces Iex-1 gene expression at day 7 and VNH 28 days later (P<0.05). 5. Gene expression of Mcp-1 is significantly increased in venous stenosis removed from WT mice with AVF and CKD. These data implicate Iex-1 in the regulation of Mcp-1 expression in the pathogenesis of VNH [11, 16-22]. 6. Finally, increased shear stress at the outflow vein has been observed after hemodialysis vascular access placement [23-26]. Taken collectively, these observations support our central hypothesis: Venous stenosis in AVFs occurs in part due to an increase in shear stress upon endothelial cells and mechanical stretch upon smooth muscle cells causing up-regulation of the Iex-1 gene with subsequent increases in Mcp-1 expression which results in recruitment of monocytes/macrophages (cartoon). The specific aims are as follows: SPECIFIC AIM 1: Assess the in vivo role(s) of endothelial (EC) and vascular smooth muscle (VSMC) Iex-1 on VNH formation in AVFs of mice with CKD. We will use novel mice with EC and VSMC conditional deletion of Iex-1 to assess infiltration of monocytes and macrophages, proliferation, migration, apoptosis, fibrosis, lumen diameter, wall thickness and expression of Mcp-1, Fgf-1, Tgf-b, and Mmp-9 in the AVF. Hypothesis: AVFs of mice with decreased Iex-1 expression in ECs and VSMCs will have reduced venous stenosis formation as a result of reduced AVF Mcp-1 expression and reduced monocyte/macrophage infiltration. SPECIFIC AIM 2: Assess the effect of restoration of the Mcp-1 expression in AVFs of mice with EC and VSMC Iex-1 deletion. We will restore Mcp-1 expression in AVFs of mice with EC and VSMC deletion of Iex-1 with adenoviral technique. We will assess monocyte and macrophage infiltration, vessel wall cell proliferation, migration, apoptosis, fibrosis, lumen diameter, wall thickness and the expression of Mcp-1, Fgf-1, Tgf-b, and Mmp-9 in the AVF. Hypothesis: In AVFs of mice with CKD and reduced Iex-1 expression in EC and VSMCs, restoration of Mcp-1 expression will be associated with AVF stenosis. SPECIFIC AIM 3: Determine the role(s) of calcitriol in preventing and/or attenuating VNH formation in pigs with AVFs and CKD. We will use pigs with AVF and CKD to determine the role of adventitial delivery of calcitriol on inhibiting VNH. Hypothesis: Adventitial delivery of calcitriol to the outflow vein of AVF in pigs with CKD will have reduced monocyte/macrophage infiltration and subsequent VNH with downstream reduction in IEX-1, MCP-1, FGF-1, TGF-?, and MMP-9 compared with controls.