Chronic kidney disease (CKD) is a progressive, multisystemic disorder that augments the risks of cardiovascular (CV) morbidity and mortality as kidney function declines. The endothelium plays a key role in modulating vascular tone, integrity, and homeostasis by producing and releasing a variety of endothelium-derived relaxing factors, including nitric oxide (NO). Endothelial dysfunction is a salient pathogenic mechanism underlying the development and progression of CKD and is characterized by reduced production of vasodilators and increased production of vasoconstrictors (e.g., endothelin-1). Factors such as the uremic milieu, inflammation, and oxidative stress are putative contributors of endothelial dysfunction and reduced NO bioavailability that ultimately impact functional and structural integrity of the vasculature. Because endothelial dysfunction is an independent predictor of CV morbidity and mortality in patients with CKD, several clinical studies have examined disease-related changes in endothelium-dependent vasodilation across the arterial tree. This review will focus on the clinical evidence regarding CKD-associated endothelial dysfunction involving both the micro- and macrovasculature, briefly discussing underlying physiological mechanisms, and summarizing available and emerging pharmacotherapies along with a brief summary of exercise training as a lifestyle intervention.

Surgically-created blood conduits used for chronic hemodialysis, including native arteriovenous fistulas (AVFs) and synthetic AV grafts (AVGs), are the lifeline for kidney failure patients. Unfortunately, each has its own limitations; AVFs often fail to mature to become useful for dialysis and AVGs often fail due to stenosis as a result of neointimal hyperplasia, which preferentially forms at the graft-venous anastomosis. No clinical therapies are currently available to significantly promote AVF maturation or prevent neointimal hyperplasia in AVGs. Central to devising strategies to solve these problems is a complete mechanistic understanding of the pathophysiological processes. The pathology of arteriovenous access problems is likely multi-factorial. This review focuses on the roles of fluid-wall shear stress (WSS) and endothelial cells (ECs). In arteriovenous access, shunting of arterial blood flow directly into the vein drastically alters the hemodynamics in the vein. These hemodynamic changes are likely major contributors to non-maturation of an AVF vein and/or formation of neointimal hyperplasia at the venous anastomosis of an AVG. ECs separate blood from other vascular wall cells and also influence the phenotype of these other cells. In arteriovenous access, the responses of ECs to aberrant WSS may subsequently lead to AVF non-maturation and/or AVG stenosis. This review provides an overview of the methods for characterizing blood flow and calculating WSS in arteriovenous access and discusses EC responses to arteriovenous hemodynamics. This review also discusses the role of WSS in the pathology of arteriovenous access, as well as confounding factors that modulate the impact of WSS.

Hemodynamic factors, induced by pulsatile blood flow, play a crucial role in vascular health and diseases, such as the initiation and progression of atherosclerosis. Computational fluid dynamics, finite element analysis, and fluid-structure interaction simulations have been widely used to quantify detailed hemodynamic forces based on vascular images commonly obtained from computed tomography angiography, magnetic resonance imaging, ultrasound, and optical coherence tomography. In this review, we focus on methods for obtaining accurate hemodynamic factors that regulate the structure and function of vascular endothelial and smooth muscle cells. We describe the multiple steps and recent advances in a typical patient-specific simulation pipeline, including medical imaging, image processing, spatial discretization to generate computational mesh, setting up boundary conditions and solver parameters, visualization and extraction of hemodynamic factors, and statistical analysis. These steps have not been standardized and thus have unavoidable uncertainties that should be thoroughly evaluated. We also discuss the recent development of combining patient-specific models with machine-learning methods to obtain hemodynamic factors faster and cheaper than conventional methods. These critical advances widen the use of biomechanical simulation tools in the research and potential personalized care of vascular diseases.