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A new arteriovenous fistula model to study the development of neointimal hyperplasia.

ABSTRACT: This study describes an alternative arteriovenous fistula (AVF) model in the rat in which the animals develop significant neointimal hyperplasia (NIH) not only at the distal anastomotic site, but also throughout the fistula body. This aortocaval fistula was established by anastomosing the distal end of the renal vein to the abdominal aorta after unilateral nephrectomy. The increased hemodynamic stress resulting from exposing the renal vein to the arterial circulation induced venous NIH as early as 7 days after surgery. This experimental AVF was characterized by the early lack of endothelium, the accumulation of proliferating vascular smooth muscle cells and the neovascularization of the fistula adventitia. In summary, we have described an informative animal model to study the pathobiology of NIH in native AVF.

SUBMITTER: Manning E

PROVIDER: S-EPMC3290023 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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A new arteriovenous fistula model to study the development of neointimal hyperplasia.

Manning Eddie E Skartsis Nikolaos N Orta Armando M AM Velazquez Omaida C OC Liu Zhao-Jun ZJ Asif Arif A Salman Loay H LH Vazquez-Padron Roberto I RI

Journal of vascular research 20120113 2

This study describes an alternative arteriovenous fistula (AVF) model in the rat in which the animals develop significant neointimal hyperplasia (NIH) not only at the distal anastomotic site, but also throughout the fistula body. This aortocaval fistula was established by anastomosing the distal end of the renal vein to the abdominal aorta after unilateral nephrectomy. The increased hemodynamic stress resulting from exposing the renal vein to the arterial circulation induced venous NIH as early ...[more]

PMID: 22249138

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Project description:In patients with severe kidney disease AVF are surgically placed in order to create good access for hemodialysis. In these dialysis patients the failure rates of AVF can be as high as 24% within 6 months after surgery, causing ineffective dialysis and necessitating additional clinical interventions. The pathological processes known to lead to AVF failure are beginning to be unravelled include the formation of venous neointimal hyperplasia (VNIH), thrombosis (Chang et al. PMID 16105066), and venous stenosis (Kanterman et al. PMID7892454, Tang et al. 1998), resulting in a reduced blood flow through the fistula. We established a rat model for AVF failure in human kidney dialysis patients. The characterization of this model has been previously described (Globerman et al. 2011, PubmedID:22002501). In this model the AVFs are surgically constructed in the right leg by connecting the superficial epigastric vein SEV to the common femoral artery (CFA), resulting in exposure of the SEV to arterial pressure with pulsatile and low resistant flow patterns (Globerman et al. 2011, PMID22002501). In the present study we utilized this AVF model in order to assess the effects of arterialized flow, with consequent pathological changes of the vessel wall due to surgical AVF instalment, on the transcriptome of endothelium from the SEV. Within the SEV these pathologies of the vessel wall include the formation of NIH in the main branch, and stenosis in the side branches. By employing this rat model we assessed the changes of the endothelial transcriptome in relation to these pathologies in order to gain mechanistic understanding of the potential roles of venous endothelium in AVF failure, as well as to identify potential biomarkers preceding AVF failure. AVF surgery was performed on N=6 rats, and 13-14 days after surgery the rats were sacrificed. AVFs were extracted from the rats, and microarray transcriptome analyses were performed on luminal endothelial cells that isolated from four different sites of the AVF by employing Laser Capture Microdissection (LCM). These sites included (i) N=5 AVF sections of the superficial epigastric vein (SEV) with neointimal hyperplasia (NIH), (ii) N=3 AVF sections of SEV side branches with luminal stenosis, (iii), N=6 sections of the SEV located distally from a ligation thereby omitting exposure to arterialized flow and consequently preventing the development of NIH or stenosis, and (iv) N=3 sections of the AVF common femoral artery without signs of NIH or stenosis.

Project description: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.

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A new arteriovenous fistula model to study the development of neointimal hyperplasia.

Publications

A new arteriovenous fistula model to study the development of neointimal hyperplasia.

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