Vázquez-Padrón, Roberto I.

Worldwide, more than 4 million patients with end-stage kidney disease require hemodialysis through an arteriovenous fistula (AVF). AVFs fail because of venous neointimal hyperplasia (VNH) resulting in venous stenosis formation. A phase 1 randomized trial in patients undergoing upper extremity AVF placement was performed to evaluate the safety and efficacy of autologous adipose–derived mesenchymal stem cells (MSCs) in improving AVF function. The mechanism of action by which MSCs exert their beneficial effects was investigated using AVFs created in mice and pigs treated with allogenic MSCs and xenotransplant using patient MSCs in CD1- Foxn1nu mice. At a median follow-up of 42 months, patients with MSC-treated AVFs had reduced time to maturation with an increase in the vein diameter compared with controls. AVFs treated with allogenic MSCs in mice and pigs had an increase in M2- and M1-like macrophages with a decrease in VNH. Transcriptomic analysis of AVFs treated with allogenic MSCs in mouse and MSC xenotransplants of patients with successful AVFs showed decreased peroxisome proliferator–activated receptor gamma ( Ppar γ) and leptin receptor ( Lepr ) and increased latent transforming growth factor–beta–binding protein 2 ( Ltbp2 ). PPARγ was reduced in CD68 (+) cells from successful AVFs and allogenic MSC-treated mouse AVFs. Venous stenosis and VNH formation were mitigated in AVFs of mice with Ppar γ ablation in immune cells. Conditioned medium from MSCs of responders versus nonresponders had decreased proinflammatory genes, senescence-associated proteins, and monocyte-to-macrophage differentiation induced by phorbol 12-myristate-13-acetate. Periadventitial delivery of MSCs to AVFs promoted positive vascular remodeling through decreased inflammatory responses.

Introduction: Hypertension (HTN) is highly prevalent among patients with chronic kidney disease (CKD) and end-stage kidney disease (ESKD), uncontrolled HTN as well as high blood pressure variability (BPV) can significantly impact cardiovascular health. This study aims to understand the impact of BPV in patients with ESKD following arteriovenous fistula (AVF) creation for hemodialysis, to better understand its association with age, sex, BMI, and cardiovascular risk. Methods: A retrospective analysis was conducted on 83 patients who underwent AVF creation between February 2019 and October 2020 at University of Miami Hospital. During 20 months, blood pressure measurements were collected from medical records at four different times during AVF access creation process, and BPV was quantified using machine learning clustering techniques. Results: The study identified three distinct clusters among the 83 patients with ESKD who underwent AVF creation. Cluster 1 ( n = 28) was characterized by high blood pressure variability, with a mean systolic blood pressure standard deviation of 16.2 mmHg. This cluster exhibited a significantly higher cardiovascular risk rate of 42.9% compared to Cluster 2 ( n = 30) and Cluster 3 ( n = 25), which had lower variability with mean systolic blood pressure standard deviations of 10.3 and 8.7 mmHg, respectively, and cardiovascular risk rates of 16.7% and 12.0%. Age, sex, and BMI did not differ significantly across the clusters. Conclusion: This study underscores the association between blood pressure variability and the increased risk of cardiovascular events, including myocardial infraction, stroke or heart failure in patients with ESKD undergoing AVF creation. Our findings highlight the critical need for vigilant monitoring of blood pressure fluctuations in this population and demonstrate how these variations are influenced by individual demographic factors. Further research is needed to develop targeted interventions to mitigate this risk.

Significance Statement Fractalkine receptor 1 (CX3CR1) mediates macrophage infiltration into the vasculature. In this study, we used humanized mice knocked in with the human CX3CR1 gene and inhibited CX3CR1 signaling using a variable domains of camelid heavy-chain-only molecule (BI 655088) to test the hypothesis that blockade of CX3CR1 results in less of the venous neointimal hyperplasia formation that is associated with arteriovenous fistula (AVF) failure. We also used human samples removed from failed AVFs combined with cell culture experiments. Our results demonstrate a novel role for CX3CR1 in reducing venous stenosis formation in AVFs. Background Fractalkine receptor 1 (CX3CR1) mediates macrophage infiltration and accumulation, causing venous neointimal hyperplasia (VNH)/venous stenosis (VS) in arteriovenous fistula (AVF). The effect of blocking CX3CR1 using an anti–human variable VHH molecule (hCX3CR1 VHH, BI 655088) on VNH/VS was determined using a humanized mouse in which the human CX3CR1 ( hCX3CR1 ) gene was knocked in (KI). Methods Whole-transcriptomic RNA sequencing with bioinformatics analysis was used on human stenotic AVF samples, C57BL/6J, hCX3CR1 KI mice with AVF and CKD, and in in vitro experiments to identify the pathways involved in preventing VNH/VS formation after hCX3CR1 VHH administration. Results Accumulation of CX3CR1 and CD68 was significantly increased in stenotic human AVFs. In C57BL/6J mice with AVF, there was increased Cx3cr1, Cx3cl1, Cd68 , and Tnf-α gene expression, and increased immunostaining of CX3CR1 and CD68. In hCX3CR1-KI mice treated with hCX3CR1 VHH molecule (KI-A), compared with vehicle controls (KI-V), there was increased lumen vessel area and patency, and decreased neointima in the AVF outflow veins. RNA-seq analysis identified TNF- α and NF- κ B as potential targets of CX3CR1 inhibition. In KI-A–treated vessels compared with KI-V, there was decreased gene expression of Tnf- α , Mcp-1 , and Il-1 β ; with reduction of Cx3cl1 , NF- κ B, and Cd68 ; decreased M1, Ly6C, smooth muscle cells, fibroblast-activated protein, fibronectin, and proliferation; and increased TUNEL and M2 staining. In cell culture, monocytes stimulated with PMA and treated with hCX3CR1 VHH had decreased TNF- α , CD68 , proliferation, and migration. Conclusions CX3CR1 blockade reduces VNH/VS formation by decreasing proinflammatory cues.