Disturbed flow in the juxta-anastomotic area of an arteriovenous fistula correlates with endothelial loss, acute thrombus formation and neointimal hyperplasia
Background: Clinical failure of arteriovenous fistulae (AVF) is frequently due to juxta-anastomotic neointimal hyperplasia (JANIH). Although the mouse AVF model recapitulates human AVF maturation, previous studies focused on the outflow vein distal to the anastomosis. We hypothesized that the juxta-anastomotic area (JAA) has increased NIH compared to the outflow vein. Method: AVF were created in C57BL/6 mice without or with chronic kidney disease (CKD). Temporal and spatial changes of the JAA were examined using histology and immunofluorescence. Computational techniques were used to model the AVF. RNA-seq and bioinformatic analyses were performed to compare the JAA with the outflow vein. The jugular vein to carotid artery AVF model was created in Wistar rats. Result: The neointima in the JAA shows increased volume compared to the outflow vein. Computational modeling shows increased volume of disturbed flow at the JAA compared to the outflow vein. Endothelial cells are immediately lost from the wall contralateral to the fistula exit, followed by thrombus formation and JANIH. Gene Ontology (GO) enrichment analysis of the 1862 differentially expressed genes (DEG) between the JANIH and the outflow vein identified 525 overexpressed genes. The rat jugular vein to carotid artery AVF showed changes similar to the mouse AVF. Conclusion: Disturbed flow through the JAA correlates with rapid endothelial cell loss, thrombus formation, and JANIH; late endothelialization of the JAA channel correlates with late AVF patency. Early thrombus formation in the JAA may influence later development of JANIH. Overall design: All animal experiments were performed in strict compliance with federal guidelines and with approval from the Institutional Animal Care and Use Committee of the Yale University. Mice were 9 to 11 weeks of age when the surgeries were performed. Anesthesia was administered using 2% to 2.5% isoflurane, and extended-release buprenorphine (Ethiqa XR; North Brunswick, NJ, USA) was administered subcutaneously with a dosage of 3.25 mg/kg body weight for intraoperative and postoperative analgesia. Briefly, after exposing the IVC and aorta, an aortocaval fistula was created by puncturing the distal aorta into the IVC using a 25-gauge needle, as described previously.(Yamamoto et al., 2013)  Visualization of pulsatile arterial blood flow in the IVC was used to assess initial technical success of AVF creation. The abdomen was then closed in two layers using running 6-0 sutures. On postoperative day 7, the anastomotic neointimas (combined from 4 mice) and outflow veins (combined from 2 mice) were carefully harvested.