Cellular phenotypes in human stenotic lesions from haemodialysis vascular access

Correlation between preoperative cephalic vein pathological types and autogenous arteriovenous fistula (AVF) maturation in patients with stage 5 chronic kidney disease

PURPOSE

To explore the correlation between preoperative cephalic vein pathological types and the maturation of autogenous arteriovenous fistula (AVF) in patients with chronic kidney disease (CKD), providing new ideas and methods for clinical prediction of fistula maturation.

METHODS

A retrospective analysis was performed in 80 patients who underwent AVF creation surgery from June 2021 to June 2023 at our hospital. Patients were followed up for 6 months. Patients were classified into the mature group (n = 57) and the power loss group (n = 23) based on the AVF maturation status. Preoperative excised venous tissues were examined using Masson's trichrome staining to compare the intimal area (Ia), medial area (Ma), lumen diameter (Ld), average intimal thickness (Avg It), and average medial thickness (Avg Mt), along with the calculations and comparisons of Ia/Ma, Avg It/Avg Mt ratios. Factors influencing AVF power loss were identified using the multifactorial logistic regression analysis.

RESULTS

Ia, Ia/Ma, and Ld were lower in the power loss group compared to the mature group (P < 0.01). No significant difference was found in Avg Mt and Avg It/Avg Mt levels between the two groups (P > 0.05). The level of Avg It was higher in the power loss group (P < 0.05). Avg It was a risk factor (P < 0.001), while Ld was a protective factor for AVF power loss (P < 0.05).

CONCLUSION

The levels of Avg It and Ld in preoperative cephalic vein tissue before AVF formation were correlated with AVF power loss. Early monitoring may improve therapeutic outcomes and prognosis of patients with stage 5 CKD.

Polymer-coated paclitaxel-eluting stents for the treatment of stenosed native arteriovenous fistulas: Long-term results from the ELUDIA study

BACKGROUND

Percutaneous transluminal angioplasty is the preferred treatment of stenosed failing arteriovenous fistulas (AVF) but is hampered by increasing rates of vascular restenosis because of development of myointimal hyperplasia.

METHODS

This multicenter observational study of polymer-coated low-dose paclitaxel-eluting stents (ELUvia stents by Boston Scientific) in stenosed AVF undergoing hemoDIAlysis (ELUDIA) was jointly conducted in three tertiary hospitals from Greece and Singapore. Failure of AVF was defined according to K-DOQI criteria and significant fistula stenosis (>50%DS by visual estimate) was determined with subtraction angiography. Patients were considered for ELUVIA stent insertion based on significant elastic recoil following balloon angioplasty for the treatment of a single vascular stenosis within a native AVF. The primary outcome measure was sustained long-term patency of the treated lesion/fistula circuit defined as successful stent placement with resumption of uninterrupted hemodialysis and without significant vascular restenosis (50%DS threshold) or other secondary interventions during follow-up.

RESULTS

Some 23 patients received the ELUVIA paclitaxel-eluting stent (eight radiocephalic, 12 brachiocephalic, and three transposed brachiobasilic native AVFs). Mean AVF age at the time of failure was 33.9 ± 20.4 months. Treated lesions included 12 stenoses at the juxta-anastomotic segment, nine at the outflow veins, and two cephalic arch lesions with a mean diameter stenosis of 86 ± 8%. Median stent diameter and length used were 7 mm and 40 mm, respectively. After a median follow-up period of 20 months, some 18 stents out of 23 cases remained patent (cumulative rate 78.3%) without any clinical or imaging evidence of recurrent stenosis. Estimated primary patency of the ELUVIA stents was 80.6% and of the corresponding fistula circuit 65.1% at 2 years by Kaplan-Meier methods.

CONCLUSIONS

This observational study has shown promising long-term results of polymer-coated paclitaxel-eluting stents for the treatment of failing arteriovenous fistulas. Large-scale controlled studies are necessary.

Early Injury Landscape in Vein Harvest by Single-Cell and Spatial Transcriptomics

BACKGROUND

Vein graft failure following cardiovascular bypass surgery results in significant patient morbidity and cost to the healthcare system. Vein graft injury can occur during autogenous vein harvest and preparation, as well as after implantation into the arterial system, leading to the development of intimal hyperplasia, vein graft stenosis, and, ultimately, bypass graft failure. Although previous studies have identified maladaptive pathways that occur shortly after implantation, the specific signaling pathways that occur during vein graft preparation are not well defined and may result in a cumulative impact on vein graft failure. We, therefore, aimed to elucidate the response of the vein conduit wall during harvest and following implantation, probing the key maladaptive pathways driving graft failure with the overarching goal of identifying therapeutic targets for biologic intervention to minimize these natural responses to surgical vein graft injury.

METHODS

Employing a novel approach to investigating vascular pathologies, we harnessed both single-nuclei RNA-sequencing and spatial transcriptomics analyses to profile the genomic effects of vein grafts after harvest and distension, then compared these findings to vein grafts obtained 24 hours after carotid-carotid vein bypass implantation in a canine model (n=4).

RESULTS

Spatial transcriptomic analysis of canine cephalic vein after initial conduit harvest and distention revealed significant enrichment of pathways (P<0.05) involved in the activation of endothelial cells (ECs), fibroblasts, and vascular smooth muscle cells, namely pathways responsible for cellular proliferation and migration and platelet activation across the intimal and medial layers, cytokine signaling within the adventitial layer, and ECM (extracellular matrix) remodeling throughout the vein wall. Subsequent single-nuclei RNA-sequencing analysis supported these findings and further unveiled distinct EC and fibroblast subpopulations with significant upregulation (P<0.05) of markers related to endothelial injury response and cellular activation of ECs, fibroblasts, and vascular smooth muscle cells. Similarly, in vein grafts obtained 24 hours after arterial bypass, there was an increase in myeloid cell, protomyofibroblast, injury response EC, and mesenchymal-transitioning EC subpopulations with a concomitant decrease in homeostatic ECs and fibroblasts. Among these markers were genes previously implicated in vein graft injury, including VCAN, FBN1, and VEGFC, in addition to novel genes of interest, such as GLIS3 and EPHA3. These genes were further noted to be driving the expression of genes implicated in vascular remodeling and graft failure, such as IL-6, TGFBR1, SMAD4, and ADAMTS9. By integrating the spatial transcriptomics and single-nuclei RNA-sequencing data sets, we highlighted the spatial architecture of the vein graft following distension, wherein activated and mesenchymal-transitioning ECs, myeloid cells, and fibroblasts were notably enriched in the intima and media of distended veins. Finally, intercellular communication network analysis unveiled the critical roles of activated ECs, mesenchymal-transitioning ECs, protomyofibroblasts, and vascular smooth muscle cells in upregulating signaling pathways associated with cellular proliferation (MDK [midkine], PDGF [platelet-derived growth factor], VEGF [vascular endothelial growth factor]), transdifferentiation (Notch), migration (ephrin, semaphorin), ECM remodeling (collagen, laminin, fibronectin), and inflammation (thrombospondin), following distension.

CONCLUSIONS

Vein conduit harvest and distension elicit a prompt genomic response facilitated by distinct cellular subpopulations heterogeneously distributed throughout the vein wall. This response was found to be further exacerbated following vein graft implantation, resulting in a cascade of maladaptive gene regulatory networks. Together, these results suggest that distension initiates the upregulation of pathological pathways that may ultimately contribute to bypass graft failure and presents potential early targets warranting investigation for targeted therapies. This work highlights the first applications of single-nuclei and spatial transcriptomic analyses to investigate venous pathologies, underscoring the utility of these methodologies and providing a foundation for future investigations.

Application of modified no-touch technique in rabbit arteriovenous fistula model and its effect on venous neointimal hyperplasia

BACKGROUND

To investigate the technical advantages of a modified no-touch technique (MNTT) in constructing arteriovenous fistulas (AVF) compared to the conventional technique (CT) and assess its potential to reduce neointimal hyperplasia in the outflow vein.

METHODS

Forty-seven New Zealand rabbits were randomly divided into three groups: control, CT, and MNTT. Rabbits in control group were observed using ultrasound and then euthanized to obtain external jugular vein (EJV) for Hematoxylin-eosin (H-E). We established common carotid artery (CCA)-EJV AVF using MNTT in the MNTT group and the CT in the CT group. AVF patency and complications were compared between the CT and MNTT groups. Rabbits with patent AVF in both groups were observed using ultrasound 2 weeks after surgery to evaluate changes in the vessel diameter and blood flow spectrum of the AVFs. H-E staining measured the intima thickness of EJV adjacent to the anastomosis and histologic characteristics of the AVF at 2 and 4 weeks after surgery.

RESULTS

Five rabbits died after surgery with common symptoms of sneezing, coughing, runny nose, anorexia, and diarrhea; two in the MNTT group and three in the CT group. There were significant differences in the diameter (p = 0.010) and peak systolic velocities (PSV) (p = 0.001) of EJV between the CT and MNTT groups 2 weeks after surgery. Spiral laminar flow (SLF) was observed in CCA and EJV adjacent to anastomosis in the MNTT group. Additionally, histological observations showed less venous neointimal hyperplasia in the MNTT group than in the CT group 4 weeks after surgery.

CONCLUSION

The rabbit model of CCA-EJV AVF established using MNTT demonstrated fewer complications, larger vein diameters, and reduced venous neointimal hyperplasia, indicating that this maybe an ideal animal model to further investigate the application of MNTT in AVF surgery.

Integrated single-nuclei and spatial transcriptomic analysis reveals propagation of early acute vein harvest and distension injury signaling pathways following arterial implantation

Background

Vein graft failure (VGF) following cardiovascular bypass surgery results in significant patient morbidity and cost to the healthcare system. Vein graft injury can occur during autogenous vein harvest and preparation, as well as after implantation into the arterial system, leading to the development of intimal hyperplasia, vein graft stenosis, and, ultimately, bypass graft failure. While previous studies have identified maladaptive pathways that occur shortly after implantation, the specific signaling pathways that occur during vein graft preparation are not well defined and may result in a cumulative impact on VGF. We, therefore, aimed to elucidate the response of the vein conduit wall during harvest and following implantation, probing the key maladaptive pathways driving graft failure with the overarching goal of identifying therapeutic targets for biologic intervention to minimize these natural responses to surgical vein graft injury.

Methods

Employing a novel approach to investigating vascular pathologies, we harnessed both single-nuclei RNA-sequencing (snRNA-seq) and spatial transcriptomics (ST) analyses to profile the genomic effects of vein grafts after harvest and distension, then compared these findings to vein grafts obtained 24 hours after carotid-cartoid vein bypass implantation in a canine model (n=4).

Results

Spatial transcriptomic analysis of canine cephalic vein after initial conduit harvest and distention revealed significant enrichment of pathways (P < 0.05) involved in the activation of endothelial cells (ECs), fibroblasts (FBs), and vascular smooth muscle cells (VSMCs), namely pathways responsible for cellular proliferation and migration and platelet activation across the intimal and medial layers, cytokine signaling within the adventitial layer, and extracellular matrix (ECM) remodeling throughout the vein wall. Subsequent snRNA-seq analysis supported these findings and further unveiled distinct EC and FB subpopulations with significant upregulation (P < 0.00001) of markers related to endothelial injury response and cellular activation of ECs, FBs, and VSMCs. Similarly, in vein grafts obtained 24 hours after arterial bypass, there was an increase in myeloid cell, protomyofibroblast, injury-response EC, and mesenchymal-transitioning EC subpopulations with a concomitant decrease in homeostatic ECs and fibroblasts. Among these markers were genes previously implicated in vein graft injury, including VCAN (versican), FBN1 (fibrillin-1), and VEGFC (vascular endothelial growth factor C), in addition to novel genes of interest such as GLIS3 (GLIS family zinc finger 3) and EPHA3 (ephrin-A3). These genes were further noted to be driving the expression of genes implicated in vascular remodeling and graft failure, such as IL-6, TGFBR1, SMAD4, and ADAMTS9. By integrating the ST and snRNA-seq datasets, we highlighted the spatial architecture of the vein graft following distension, wherein activated and mesenchymal-transitioning ECs, myeloid cells, and FBs were notably enriched in the intima and media of distended veins. Lastly, intercellular communication network analysis unveiled the critical roles of activated ECs, mesenchymal transitioning ECs, protomyofibroblasts, and VSMCs in upregulating signaling pathways associated with cellular proliferation (MDK, PDGF, VEGF), transdifferentiation (Notch), migration (ephrin, semaphorin), ECM remodeling (collagen, laminin, fibronectin), and inflammation (thrombospondin), following distension.

Conclusions

Vein conduit harvest and distension elicit a prompt genomic response facilitated by distinct cellular subpopulations heterogeneously distributed throughout the vein wall. This response was found to be further exacerbated following vein graft implantation, resulting in a cascade of maladaptive gene regulatory networks. Together, these results suggest that distension initiates the upregulation of pathological pathways that may ultimately contribute to bypass graft failure and presents potential early targets warranting investigation for targeted therapies. This work highlights the first applications of single-nuclei and spatial transcriptomic analyses to investigate venous pathologies, underscoring the utility of these methodologies and providing a foundation for future investigations.

Comparative analysis of RADAR vs. conventional techniques for AVF maturation in patients with blood viscosity and vessel elasticity-related diseases through fluid-structure interaction modeling: Anemia, hypertension, and diabetes

PURPOSE

This study aims to compare two surgical techniques, the standard Vein-to-Artery and the newer Artery-to-Vein (Radial Artery Deviation And Reimplantation; RADAR), for enhancing the success of Arterio-Venous Fistula maturation in end-stage renal disease patients. The impact of diseases like anemia, diabetes, hypertension, and chronic kidney disease were considered. The goals are to advance Arterio-Venous Fistula (AVF) surgery, improve patient outcomes, and contribute to evidence-based surgical guidelines.

METHODS

Fluid-structure interaction modeling was employed to investigate how hemodynamic and mechanical stresses impact arteriovenous fistula maturation, with a particular focus on the role of wall shear stress in determining maturation outcomes. The critical threshold for vessel injury was identified as wall shear stress values exceeding 35 N/m2, while stenosis formation was projected to occur at levels below 1 N/m2. This work introduced a novel approach by considering disease-related factors, including blood viscosity (anemia), and vessel elasticity (diabetes, hypertension, and chronic kidney diseases), which directly influence hemodynamics and the generation of wall shear stress. Furthermore, the model was designed to incorporate varying thicknesses and elasticities for both the vein and artery, accurately representing authentic vascular anatomy.

RESULTS

The RADAR technique has demonstrated superior performance compared to the standard technique by providing appropriate wall shear stress in critical regions and minimizing the risk of wall damage. Its use of a thicker vessel also reduces the risk of vessel injury, making it particularly effective for patients with Chronic Kidney Disease (CKD), hypertension, anemia, and diabetes, ensuring optimal blood flow and fewer complications. However, there are minor concerns about stenosis formation in hypertension and anemia cases, which could be mitigated by adjusting the anastomosis angle to be lower than 30°.

CONCLUSION

Diabetes and hypertension have significant physiological effects that increase the risks associated with arteriovenous fistula maturation. The anemic condition resulting from CKD may help reduce vessel injury but raises concerns about potential stenosis formation. Despite these co-morbidities, the RADAR technique has demonstrated its ability to induce more favorable hemodynamic changes, promoting arteriovenous fistula maturation.

Early arteriovenous fistula failure associated with mortality and major adverse cardiovascular events in patients undergoing incident hemodialysis

BACKGROUND

Arteriovenous fistula (AVF) patency is important for patients undergoing hemodialysis. The association between early AVF failure and the prognosis, including all-cause mortality and major adverse cardiovascular events (MACE), has not been fully investigated. The present study was performed to investigate the association between early AVF failure and 3-year mortality, cardiovascular disease (CVD) mortality, and MACE.

METHODS

We analyzed 358 patients who started hemodialysis in our institution from October 2008 to February 2020. We defined early AVF failure as cases requiring percutaneous transluminal angioplasty or reoperation within 1 year after AVF surgery. The patients were divided into two groups according to the presence or absence of early AVF failure, and the prognosis of each group was examined. The association between early AVF failure and outcomes (3-year all-cause mortality, CVD mortality, and MACE) was determined using Cox proportional hazards regression analysis.

RESULTS

During the 3-year follow-up, 75 (20.9%) patients died (cardiovascular death: n = 39) and 145 patients developed MACE. According to the multivariable analysis, the early AVF failure group had a significantly higher risk of 3-year all-cause mortality (hazard ratio [HR], 1.42; 95% confidence interval [CI], 1.09-1.83; p = 0.009), CVD mortality (HR, 1.54; 95% CI, 1.29-2.08; p < 0.001), and MACE (HR, 1.68; 95% CI, 1.25-2.26; p < 0.001). When the patients were stratified by age, early AVF failure was associated with 3-year all-cause mortality in all groups except for the younger group (<65 years of age).

CONCLUSIONS

Early AVF failure was associated with an increased risk of 3-year all-cause mortality, CVD mortality, and MACE.

Dialysis Access Maintenance: Plain Balloon Angioplasty

Plain balloon angioplasty remains the first-line treatment for dialysis access stenosis. This chapter reviews the outcomes of plain balloon angioplasty from cohort studies and comparative studies. Angioplasty outcomes are more favourable in arteriovenous fistulae (AVF) compared to arteriovenous grafts (AVG) with primary patency at 6 months ranging from 42-63% compared to 27-61%, respectively, and improved for forearm fistulae compared with upper arm fistulae. Higher pressures are required to treat stenoses in AVFs compared to AVGs. Outcomes are worse in more severe stenoses, increased patient age, previous interventions and fistulae that develop early stenoses. Major complication rates following angioplasty in dialysis access are between 3 and 5%. Repeat treatments and the use of adjuncts such as drug-coated balloons and stents can prolong the patency of dialysis access. Level of Evidence No level of evidence (Review paper).

Long-term mortality and patency after drug-coated balloon angioplasty in the hemodialysis circuit: A systematic review and meta-analysis of randomized controlled trials

PURPOSE

To compare all-cause mortality and primary patency with drug-coated balloon angioplasty (DCBA) compared with plain balloon angioplasty (PBA) in people with hemodialysis-related stenosis.

MATERIALS AND METHODS

PubMed, Embase, and Cochrane Library databases were searched from November 1966 to February 2021 to identify randomized controlled trials (RCTs) that assessed the use of DCBA versus PBA for stenosis in hemodialysis circuits. Data extracted from the articles were integrated to determine all-cause mortality, target lesion primary patency (TLPP), circuit access primary patency (CAPP), 30-day adverse events, and technical success for the two approaches. We performed meta-analysis on these results using a fixed-effects model to evaluate odds ratios (ORs) and 95% confidence intervals (CIs) where I2 < 50% in a test for heterogeneity, or a random-effect model if otherwise. Sensitivity and subgroup analyses were also performed.

RESULTS

Sixteen RCTs of 1672 individuals were included in our meta-analysis, of which 839 individuals received DCBA and 833 received PBA. The pooled outcome showed no statistical difference between DCBA and PBA in all-cause mortality at 6 months (OR = 1.29, 95% CI = 0.72-2.32, p = 0.39, I2 = 4%), 12 months (OR = 1.02, 95% CI = 0.68-1.53, p = 0.91, I2 = 0%), and 24 months (OR = 1.50, 95% CI = 0.87-2.57, p = 0.15, I2 = 0%), 30-day adverse events (OR = 1.09, 95% CI = 0.30-3.98, p = 0.90, I2 = 66%), and technical success (OR = 0.18, 95% CI = 0.02-1.92, p = 0.16, I2 = 65%). The DCBA had significantly better outcomes versus PBA in TLPP at 6 months (OR = 2.37, 95% CI = 1.84-3.04, p < 0.001, I2 = 44%) and 12 months (OR = 1.77, 95% CI = 1.22-2.56, p = 0.002, I2 = 56%), and CAPP at 6 months (OR = 2.07, 95% CI = 1.21-3.54, p = 0.008, I2 = 67%) and 12 months (OR = 1.66, 95% CI = 1.29-2.15, p < 0.001, I2 = 0%).

CONCLUSION

In hemodialysis circuit stenosis, DCBA appears to have similar safety but greater efficacy than PBA.

Choosing the right treatment for the right lesion, part I: a narrative review of the role of plain balloon angioplasty in dialysis access maintenance

Background and Objective

The majority of patients with end-stage renal disease (ESRD) requiring hemodialysis (HD) do so via an arteriovenous fistula (AVF) or graft. Both of these accesses are complicated by dysfunction related to neointimal hyperplasia (NIH) and subsequent stenosis. Percutaneous balloon angioplasty using plain balloons is the first line treatment for clinically-significant stenosis, with excellent initial response rates, however, with poor long-term patency and need for frequent reintervention. Recent research has sought to improve patency rates utilizing antiproliferative drug-coated balloons (DCBs), however, their role in treatment has not yet been fully determined. In part one of this two-part review, we aim to provide a comprehensive overview of the mechanisms of arteriovenous (AV) access stenosis, the evidence behind their treatment with high-quality plain balloon angioplasty techniques, and treatment considerations for specific stenotic lesions.

Methods

An electronic search was performed on PubMed and EMBASE to identify relevant articles from 1980 to 2022. The highest available level of evidence regarding stenosis pathophysiology, angioplasty techniques, and approaches to treating different types of lesions within fistulas and grafts were included as part of this narrative review.

Key Content and Findings

NIH, and subsequent stenoses, develop via a combination of upstream events, causing vascular damage, and downstream events, representing the subsequent biologic response. The large majority of stenotic lesions can be treated utilizing high-pressure balloon angioplasty, with the addition of ultra-high pressure balloon (UHPB) angioplasty for resistant lesions and prolonged angioplasty with progressive balloon upsizing for elastic lesions. Additional treatment considerations must be taken into account when treating specific lesions, including cephalic arch and swing point stenoses in fistulas and graft-vein anastomotic stenoses in grafts, amongst others.

Conclusions

High-quality plain balloon angioplasty, performed utilizing the available evidence-basis regarding technique and considerations for specific lesion locations, is successful in treating the large majority of AV access stenoses. While initially successful, patency rates remain non-durable. Part two of this review will discuss the evolving role of DCBs, which seek to improve angioplasty outcomes.

Sex Differences in Arteriovenous Fistula Failure: Insights from Bioinformatics Analysis

(1) Background: Arteriovenous fistulas (AVFs) are the preferred access for hemodialysis. Unfortunately, about 60% of patients, especially female patients, fail to receive normal dialysis within one year after surgery because of AVF failure. However, the underlying mechanisms caused by sex differences in AVF failure remain unclear. (2) Methods: We performed analysis of DEGs and functional analysis with the dataset GSE119296 to reveal the biology underlying AVF failure. Immune responses were calculated using CIBERSORT. A protein-protein interaction network and hub gene were constructed using STRING and stepwise identification of potential drugs was performed online. (3) Results: Functional analysis showed that extracellular matrix reprogramming and PI3K-AKT pathway enrichment were significant in both male and female patients. COL1A1 was the hub gene in male patients, whereas CDK1 was the hub gene in female patients. Immune responses including γδ-T cells and mast cells are activated in female patients while no significant differences were noted in the male group. (4) Conclusions: In this study, we used a series of mature and recognized bioinformatic strategies to determine the following items: (1) Reveal the pathogenesis of AVF failure through HUB genes and signaling pathways between the different sexes. (2) Determine the relationship between sex differences in AVF failure and immune abnormalities. (3) Search for relevant sex-specific drugs targeting AVF failure.

A proteomics analysis of neointima formation on decellularized vascular grafts reveals regenerative alterations in protein signature running head: Proteomics analysis of neointima formation

Background: Neointima formation contributes to vascular grafts stenosis and thrombosis. It is a complex reaction that plays a significant role in the performance of vascular grafts. Despite its critical implications, little is known about the mechanisms underlying neointima formation. This study compares neointima proteome in different stages and plasma samples.

Methods: Heterogenous acellular native arteries were implanted as abdominal aortic interposition grafts in a rabbit model. Grafts were harvested at 0.5, 1, 4, 6, 7, 14, 21, and 28 days post-surgery for histological and proteomic analysis of the neointima.

Results: Histological examination showed a transformed morphological pattern and components, including serum proteins, inflammatory cells, and regenerative cells. Proteomics analysis of the neointima showed distinct characteristics after 14 days of implantation compared to early implantation. Early changes in the neointima samples were proteins involved in acute inflammation and thrombosis, followed by the accumulation of extracellular matrix (ECM) proteins. A total of 110 proteins were found to be differentially expressed in later samples of neointima compared to early controls. The enriched pathways were mainly protein digestion and adsorption, focal adhesion, PI3K-Akt signaling pathway, and ECM-receptor interaction in the late stage. All distributions of proteins in the neointima are different compared to plasma.

Conclusion: The biological processes of neointima formation at different stages identified with proteome found developmental characteristics of vascular structure on a decellularized small vascular graft, and significant differences were identified by proteomics in the neointima of early-stage and late-stage after implantation. In the acute unstable phase, the loose and uniform neointima was mainly composed of plasma proteins and inflammatory cells. However, in the relatively stable later stage, the most notable results were an up-regulation of ECM components. The present study demonstrates an interaction between biological matter and vascular graft, provides insights into biological process changes of neointima and facilitates the construction of a functional bioengineered small vascular graft for future clinical applications.

von Willebrand Factor: A Central Regulator of Arteriovenous Fistula Maturation Through Smooth Muscle Cell Proliferation and Outward Remodeling

Background Arteriovenous fistula (AVF) maturation failure is a main limitation of vascular access. Maturation is determined by the intricate balance between outward remodeling and intimal hyperplasia, whereby endothelial cell dysfunction, platelet aggregation, and vascular smooth muscle cell (VSMC) proliferation play a crucial role. von Willebrand Factor (vWF) is an endothelial cell-derived protein involved in platelet aggregation and VSMC proliferation. We investigated AVF vascular remodeling in vWF-deficient mice and vWF expression in failed and matured human AVFs. Methods and Results Jugular-carotid AVFs were created in wild-type and vWF^-/- mice. AVF flow was determined longitudinally using ultrasonography, whereupon AVFs were harvested 14 days after surgery. VSMCs were isolated from vena cavae to study the effect of vWF on VSMC proliferation. Patient-matched samples of the basilic vein were obtained before brachio-basilic AVF construction and during superficialization or salvage procedure 6 weeks after AVF creation. vWF deficiency reduced VSMC proliferation and macrophage infiltration in the intimal hyperplasia. vWF^-/- mice showed reduced outward remodeling (1.5-fold, P=0.002) and intimal hyperplasia (10.2-fold, P<0.0001). AVF flow in wild-type mice was incremental over 2 weeks, whereas flow in vWF^-/- mice did not increase, resulting in a two-fold lower flow at 14 days compared with wild-type mice (P=0.016). Outward remodeling in matured patient AVFs coincided with increased local vWF expression in the media of the venous outflow tract. Absence of vWF in the intimal layer correlated with an increase in the intima-media ratio. Conclusions vWF enhances AVF maturation because its positive effect on outward remodeling outweighs its stimulating effect on intimal hyperplasia.

Oxidative stress: An essential factor in the process of arteriovenous fistula failure

For more than half a century, arteriovenous fistula (AVFs) has been recognized as a lifeline for patients requiring hemodialysis (HD). With its higher long-term patency rate and lower probability of complications, AVF is strongly recommended by guidelines in different areas as the first choice for vascular access for HD patients, and its proportion of application is gradually increasing. Despite technological improvements and advances in the standards of postoperative care, many deficiencies are still encountered in the use of AVF related to its high incidence of failure due to unsuccessful maturation to adequately support HD and the development of neointimal hyperplasia (NIH), which narrows the AVF lumen. AVF failure is linked to the activation and migration of vascular cells and the remodeling of the extracellular matrix, where complex interactions between cytokines, adhesion molecules, and inflammatory mediators lead to poor adaptive remodeling. Oxidative stress also plays a vital role in AVF failure, and a growing amount of data suggest a link between AVF failure and oxidative stress. In this review, we summarize the present understanding of the pathophysiology of AVF failure. Furthermore, we focus on the relation between oxidative stress and AVF dysfunction. Finally, we discuss potential therapies for addressing AVF failure based on targeting oxidative stress.

Overview of hemodialysis access and assessment

OBJECTIVE

To provide family physicians with an evidence-based overview on the various methods of vascular access for hemodialysis (HD) and to provide a framework for the clinical assessment of HD access.

SOURCES OF INFORMATION

A MEDLINE literature search was conducted using the MeSH terms arteriovenous fistula, arteriovenous graft, central venous catheter, and hemodialysis (or haemodialysis), including all relevant English-language articles published between January 1995 and September 2021.

MAIN MESSAGE

The main types of permanent vascular access for HD are arteriovenous fistulas, arteriovenous grafts, and central venous catheters. A pragmatic, patient-centred approach is required when choosing the type of access for an individual. Common complications of vascular access creation include thrombosis, central venous stenosis, dialysis access steal syndrome, and arteriovenous fistula aneurysms.

CONCLUSION

Family physicians play an important role in the clinical assessment and monitoring of HD vascular access. A thorough clinical assessment can detect a failing arteriovenous fistula and any associated complications, which can allow for prompt investigation and intervention to restore functionality, maintain access longevity, and improve patient quality of life.

Aperçu de l’accès pour l’hémodialyse et de son évaluation

Objectif

Présenter aux médecins de famille un aperçu fondé sur des données probantes des diverses méthodes d’accès vasculaire pour l’hémodialyse (HD), et fournir des paramètres pour l’évaluation clinique de l’accès vasculaire pour l’HD.

Sources de l’information

Une recherche documentaire dans MEDLINE a été effectuée au moyen des termes MeSH en anglais arteriovenous fistula , arteriovenous graft , central venous catheter et hemodialysis (ou haemodialysis ), et tous les articles pertinents publiés en anglais entre janvier 1995 et septembre 2021.

Message principal

Les principaux types d’accès vasculaire permanent pour l’HD sont les fistules artérioveineuses, les greffes artérioveineuses et les cathéters veineux centraux. Il faut suivre une approche pratique et centrée sur le patient dans le choix du type d’accès pour chaque personne. Les complications courantes de la création d’un accès vasculaire comprennent la thrombose, la sténose veineuse centrale, le syndrome vasculaire de vol d’accès en dialyse et les anévrismes des fistules artérioveineuses.

Conclusion

Les médecins de famille jouent un rôle important dans l’évaluation clinique et la surveillance de l’accès vasculaire pour l’HD. Une évaluation clinique rigoureuse peut détecter une fistule artérioveineuse déficiente et ses complications connexes, et peut permettre une investigation et une intervention rapides pour restaurer le fonctionnement, maintenir la longévité de l’accès et améliorer la qualité de vie du patient.

Downregulation of the endothelial histone demethylase JMJD3 is associated with neointimal hyperplasia of arteriovenous fistulas in kidney failure

Jumonji domain-containing protein-3 (JMJD3), a histone H3 lysine 27 (H3K27) demethylase, promotes endothelial regeneration, but its function in neointimal hyperplasia (NIH) of arteriovenous fistulas (AVFs) has not been explored. In this study, we examined the contribution of endothelial JMJD3 to NIH of AVFs and the mechanisms underlying JMJD3 expression during kidney failure. We found that endothelial JMJD3 expression was negatively associated with NIH of AVFs in patients with kidney failure. JMJD3 expression in endothelial cells (ECs) was also downregulated in the vasculature of chronic kidney disease (CKD) mice. In addition, specific knockout of endothelial JMJD3 delayed EC regeneration, enhanced endothelial mesenchymal transition, impaired endothelial barrier function as determined by increased Evans blue staining and inflammatory cell infiltration, and accelerated neointima formation in AVFs created by venous end to arterial side anastomosis in CKD mice. Mechanistically, JMJD3 expression was downregulated via binding of transforming growth factor beta 1-mediated Hes family transcription factor Hes1 to its gene promoter. Knockdown of JMJD3 enhanced H3K27 methylation, thereby inhibiting transcriptional activity at promoters of EC markers and reducing migration and proliferation of ECs. Furthermore, knockdown of endothelial JMJD3 decreased endothelial nitric oxide synthase expression and nitric oxide production, leading to the proliferation of vascular smooth muscle cells. In conclusion, we demonstrate that decreased expression of endothelial JMJD3 impairs EC regeneration and function and accelerates neointima formation in AVFs. We propose increasing the expression of endothelial JMJD3 could represent a new strategy for preventing endothelial dysfunction, attenuating NIH, and improving AVF patency in patients with kidney disease.

Effect of local anti-vascular endothelial growth factor therapy to prevent the formation of stenosis in outflow vein in arteriovenous fistula

BACKGROUND AND OBJECTIVES

Vascular stenosis and angiogenesis are the major causes of short expectancy of arteriovenous fistula (AVF). Increased expression of vascular endothelial growth factor-A (VEGF-A) has been suggested to play an important role in the pathophysiologic process. Anti-VEGF has been proved to be effective on anti-angiogenesis and applied in clinical practice, but its effect on anti-stenosis remains to be verified before it could be applied to prevent stenosis of AVF. This study was aimed to evaluate the effect of local anti-VEGF therapy to prevent the formation of stenosis in the outflow vein in AVF and its mechanism.

METHODS

Bioinformatics of VEGF-A and its downstream-regulated molecules from the STRING PPI database were analyzed in this study. The biopsy samples from outflow veins of AVF in patients and C57BL/6 mouse models were analyzed to examine the mechanisms of pathologic vascular stenosis associated with VEGF pathways and their potential therapeutic targets.

RESULTS

We found that the reduction of VEGF-A could downregulate downstream molecules and subsequently reduce the intimal hyperplasia and abnormal vascular remodeling by analyzing the STRING PPI database. Venous wall thickening, intimal neointima formation, and apoptosis of vascular endothelial cells in the proliferative outflow vein of the AVF were significantly more obvious, and upregulation of expression of VEGF was observed in dysfunctional AVF in patients. In mouse models, the expression of VEGF, Ephrin receptor B4 (EphB4), matrix metalloproteinase (MMP)2, MMP9, tissue inhibitor of metalloproteinase (TIMP)1, TIMP2, and caspase 3 in the control-shRNA surgical group was significantly higher than in the sham group (P < 0.05), and all of these indicators were significantly lower in lentiviral transfection group and Avastin group than in control-shRNA surgical group (P < 0.05) on the 14th day after AVF operation.

CONCLUSION

VEGF expression is significantly increased in vascular endothelial cells in stenosed or occluded outflow veins of dysfunctional AVF. Local injection of Avastin into the adventitia of the proximal outflow vein in autologous AVF procedure has an excellent potential to prevent the subsequent local stenosis of the proximal outflow vein.

Early Adventitial Activation and Proliferation in a Mouse Model of Arteriovenous Stenosis: Opportunities for Intervention

Background: Arteriovenous fistula (AVF) stenosis remains an important cause of AVF maturation failure, for which there are currently no effective therapies. We examined the pattern and phenotype of cellular proliferation at different timepoints in a mouse model characterized by a peri-anastomotic AVF stenosis. Methods: Standard immunohistochemical analyses for cellular proliferation and macrophage infiltration were performed at 2, 7 and 14 d on our validated mouse model of AVF stenosis to study the temporal profile, geographical location and cellular phenotype of proliferating and infiltrating cells in this model. Results: Adventitial proliferation and macrophage infiltration (into the adventitia) began at 2 d, peaked at 7 d and then declined over time. Surprisingly, there was minimal macrophage infiltration or proliferation in the neointimal region at either 7 or 14 d, although endothelial cell proliferation increased rapidly between 2 d and 7 d, and peaked at 14 d. Conclusions: Early and rapid macrophage infiltration and cellular proliferation within the adventitia could play an important role in the downstream pathways of both neointimal hyperplasia and inward or outward remodelling.

Immuno-regenerative biomaterials for in situ cardiovascular tissue engineering - Do patient characteristics warrant precision engineering?

In situ tissue engineering using bioresorbable material implants - or scaffolds - that harness the patient's immune response while guiding neotissue formation at the site of implantation is emerging as a novel therapy to regenerate human tissues. For the cardiovascular system, the use of such implants, like blood vessels and heart valves, is gradually entering the stage of clinical translation. This opens up the question if and to what extent patient characteristics influence tissue outcomes, necessitating the precision engineering of scaffolds to guide patient-specific neo-tissue formation. Because of the current scarcity of human in vivo data, herein we review and evaluate in vitro and preclinical investigations to predict the potential role of patient-specific parameters like sex, age, ethnicity, hemodynamics, and a multifactorial disease profile, with special emphasis on their contribution to the inflammation-driven processes of in situ tissue engineering. We conclude that patient-specific conditions have a strong impact on key aspects of in situ cardiovascular tissue engineering, including inflammation, hemodynamic conditions, scaffold resorption, and tissue remodeling capacity, suggesting that a tailored approach may be required to engineer immuno-regenerative biomaterials for safe and predictive clinical applicability.

Identification of the Crucial Gene in Overflow Arteriovenous Fistula by Bioinformatics Analysis

Objective: The aim was to study the preliminary screening of the crucial genes in intimal hyperplasia in the venous segment of arteriovenous (AV) fistula and the underlying potential molecular mechanisms of intimal hyperplasia with bioinformatics analysis. Methods: The gene expression profile data (GSE39488) was analyzed to identify differentially expressed genes (DEGs). We performed Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis of DEGs. Gene set enrichment analysis (GSEA) was used to understand the potential activated signaling pathway. The protein-protein interaction (PPI) network was constructed with the STRING database and Cytoscape software. The Venn diagram between 10 hub genes and gene sets of 4 crucial signaling pathways was used to obtain core genes and relevant potential pathways. Furthermore, GSEAs were performed to understand their biological functions. Results: A total of 185 DEGs were screened in this study. The main biological function of the 111 upregulated genes in AV fistula primarily concentrated on cell proliferation and vascular remodeling, and the 74 downregulated genes in AV fistula were enriched in the biological function mainly relevant to inflammation. GSEA found four signaling pathways crucial for intimal hyperplasia, namely, MAPK, NOD-like, Cell Cycle, and TGF-beta signaling pathway. A total of 10 hub genes were identified, namely, EGR1, EGR2, EGR3, NR4A1, NR4A2, DUSP1, CXCR4, ATF3, CCL4, and CYR61. Particularly, DUSP1 and NR4A1 were identified as core genes that potentially participate in the MAPK signaling pathway. In AV fistula, the biological processes and pathways were primarily involved with MAPK signaling pathway and MAPK-mediated pathway with the high expression of DUSP1 and were highly relevant to cell proliferation and inflammation with the low expression of DUSP1. Besides, the biological processes and pathways in AV fistula with the high expression of NR4A1 similarly included the MAPK signaling pathway and the pathway mediated by MAPK signaling, and it was mainly involved with inflammation in AV fistula with the low expression of NR4A1. Conclusion: We screened four potential signaling pathways relevant to intimal hyperplasia and identified 10 hub genes, including two core genes (i.e., DUSP1 and NR4A1). Two core genes potentially participate in the MAPK signaling pathway and might serve as the therapeutic targets of intimal hyperplasia to prevent stenosis after AV fistula creation.

Intimal Hyperplasia and Arteriovenous Fistula Failure: Looking Beyond Size Differences

The development of venous intimal hyperplasia (IH) has been historically associated with failure of arteriovenous fistulas (AVF) used for hemodialysis. This long-standing assumption, based on histological observations, has been recently challenged by clinical studies indicating that the size of the intima by itself is not enough to explain stenosis or AVF maturation failure. Irrespective of this lack of association, IH is present in most native veins and fistulas, is prominent in many cases, and suggests a role in the vein that may not be reflected by its dimensions. Therefore, the contribution of IH to AVF dysfunction remains controversial. Using only clinical data and avoiding extrapolations from animal models, we critically discuss the biological significance of IH in vein remodeling, vascular access function, and the response of the venous wall to repeated trauma in hemodialysis patients. We address questions and pose new ones such as: What are the factors that contribute to IH in pre-access veins and AVFs? Do cellular phenotypes and composition of the intima influence AVF function? Are there protective roles of the venous intima? This review explores these possibilities, with hopes of rekindling a critical discussion about venous IH that goes beyond thickness and AVF outcomes.

Tissue Ki67 proliferative index expression and pathological changes in hemodialysis arteriovenous fistulae: Preliminary single-center results

BACKGROUND

Arteriovenous fistula (AVF) for hemodialysis integrates outward remodeling with vessel wall thickening in response to drastic hemodynamic changes. Aim of this study is to determine the role of Ki67, a well-established proliferative marker, related to AVF, and its relationship with time-dependent histological morphologic changes.

MATERIALS AND METHODS

All patients were enrolled in 1 year and stratified in two groups: (A) pre-dialysis patients submitted to first AVF and (B) patients submitted to revision of AVF. Morphological changes: neo-angiogenesis (NAG), myointimal thickening (MIT), inflammatory infiltrate (IT), and aneurysmatic fistula degeneration (AD). The time of AVF creation was recorded. A biopsy of native vein in Group A and of arterialized vein in Group B was submitted to histological and immunohistochemical (IHC) analysis. IHC for Ki67 was automatically performed in all specimens. Ki67 immunoreactivity was assessed as the mean number of positive cells on several high-power fields, counted in the hot spots.

RESULTS

A total of 138 patients were enrolled, 69 (50.0%) Group A and 69 (50.0%) Group B. No NAG or MIT were found in Group A. Seven (10.1%) Group A veins showed a mild MIT. Analyzing the Group B, a moderate-to-severe MIT was present in 35 (50.7%), IT in 19 (27.5%), NAG in 37 (53.6%); AD was present in 10 (14.5%). All AVF of Group B with the exception of one (1.4%) showed a positivity for Ki67, with a mean of 12.31 ± 13.79 positive cells/hot spot (range 0-65). Ki67-immunoreactive cells had a subendothelial localization in 23 (33.3%) cases, a myointimal localization in SMC in 35 (50.7%) cases. The number of positive cells was significantly correlated with subendothelial localization of Ki67 (p = 0.001) and with NA (p = 0.001).

CONCLUSIONS

Native veins do not contain cycling cells. In contrast, vascular cell proliferation starts immediately after AVF creation and persists independently of the time the fistula is set up. The amount of proliferating cells is significantly associated with MIT and subendothelial localization of Ki67-immunoreactive cells, thus suggesting a role of Ki-67 index in predicting AVF failure.

Recent Advances in Liposomal-Based Anti-Inflammatory Therapy

Liposomes can be seen as ideal carriers for anti-inflammatory drugs as their ability to (passively) target sites of inflammation and release their content to inflammatory target cells enables them to increase local efficacy with only limited systemic exposure and adverse effects. Nonetheless, few liposomal formulations seem to reach the clinic. The current review provides an overview of the more recent innovations in liposomal treatment of rheumatoid arthritis, psoriasis, vascular inflammation, and transplantation. Cutting edge developments include the liposomal delivery of gene and RNA therapeutics and the use of hybrid systems where several liposomal bilayer features, or several drugs, are combined in a single formulation. The majority of the articles reviewed here focus on preclinical animal studies where proof-of-principle of an improved efficacy-safety ratio is observed when using liposomal formulations. A few clinical studies are included as well, which brings us to a discussion about the challenges of clinical translation of liposomal nanomedicines in the field of inflammatory diseases.

MMP-9 Deletion Attenuates Arteriovenous Fistula Neointima through Reduced Perioperative Vascular Inflammation

Matrix metalloproteinase 9 (MMP-9) expression is upregulated in vascular inflammation and participates in vascular remodeling, including aneurysm dilatation and arterial neointima development. Neointima at the arteriovenous (AV) fistula anastomosis site primarily causes AV fistula stenosis and failure; however, the effects of MMP-9 on perioperative AV fistula remodeling remain unknown. Therefore, we created AV fistulas (end-to-side anastomosis) in wild-type (WT) and MMP-9 knockout mice with chronic kidney disease to further clarify this. Neointima progressively developed in the AV fistula venous segment of WT mice during the four-week postoperative course, and MMP-9 knockout increased the lumen area and attenuated neointima size by reducing smooth muscle cell and collagen components. Early perioperative AV fistula mRNA sequencing data revealed that inflammation-related gene sets were negatively enriched in AV fistula of MMP-9 knockout mice compared to that in WT mice. qPCR results also showed that inflammatory genes, including tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1), were downregulated. In addition, Western blot results showed that MMP-9 knockout reduced CD44 and RAC-alpha serine/threonine-protein kinase (Akt) and extracellular signal-regulated kinases (ERK) phosphorylation. In vitro, MMP-9 addition enhanced IL-6 and MCP-1 expression in vascular smooth muscle cells, as well as cell migration, which was reversed by an MMP-9 inhibitor. In conclusion, MMP-9 knockout attenuated AV fistula stenosis by reducing perioperative vascular inflammation.

The anatomical sources of neointimal cells in the arteriovenous fistula

Neointimal cells are an elusive population with ambiguous origins, functions, and states of differentiation. Expansion of the venous intima in arteriovenous fistula (AVF) is one of the most prominent remodeling processes in the wall after access creation. However, most of the current knowledge about neointimal cells in AVFs comes from extrapolations from the arterial neointima in non-AVF systems. Understanding the origin of neointimal cells in fistulas may have important implications for the design and effective delivery of therapies aimed to decrease intimal hyperplasia (IH). In addition, a broader knowledge of cellular dynamics during postoperative remodeling of the AVF may help clarify other transformation processes in the wall that combined with IH determine the successful remodeling or failure of the access. In this review, we discuss the possible anatomical sources of neointimal cells in AVFs and their relative contribution to intimal expansion.

Effect of galectin-3 in the pathogenesis of arteriovenous fistula stenosis formation

Objective

This study sought to investigate the effect of local expression of galectin-3 in the development of stenotic arteriovenous fistula (AVF).

Methods

We collected stenotic venous tissues, adjacent nonstenotic venous tissues, and blood samples from end-stage renal disease (ESRD) patients with AVF stenosis, while normal venous tissues and blood samples were collected from ESRD patients before AVF creation as controls. Also blood samples were collected from ESRD patients with nonstenosis functional AVF. Galectin-3, proliferating cell nuclear antigen (PCNA), matrix metalloproteinase-9 (MMP-9), and α-SMA expression in the venous tissues were examined by immunohistochemistry, and the ERK1/2 pathway activity in the intima was accessed by western blot. Serum galectin-3 level was measured by ELISA. Thereafter, human pulmonary arterial smooth muscle cells (HPASMCs) were cultured in vitro, and the interaction between Galectin-3 and ERK1/2 pathway in HPASMCs was estimated by western blot.

Results

ESRD patients with stenotic AVF had a significant higher serum galectin-3 level than normal controls, and patients with non-stenotic functional AVF. The expression levels of galectin-3, phosphorylated ERK1/2, PCNA, MMP-9, and α-SMA in the stenotic venous tissues were higher than that in the normal venous tissues or the adjacent nonstenotic AVF venous tissues. Correlation analysis showed that the expression of galectin-3 of the neointima was positively correlated with PCNA and α-SMA in the stenotic AVF venous tissues. In HPASMCs, galectin-3 can increase the activity of phosphorylated ERK1/2 and promote the expression of α-SMA.

Conclusion

In the stenotic AVF of ESRD patients, expression of the galectin-3 was significantly increased, showing a positive relation with neointima development.

Arteriovenous access in hemodialysis: A multidisciplinary perspective for future solutions

In hemodialysis, vascular access is a key issue. The preferred access is an arteriovenous fistula on the non-dominant lower arm. If the natural vessels are insufficient for such access, the insertion of a synthetic vascular graft between artery and vein is an option to construct an arteriovenous shunt for punctures. In emergency situations and especially in elderly with narrow and atherosclerotic vessels, a cuffed double-lumen catheter is placed in a larger vein for chronic use. The latter option constitutes a greater risk for infections while arteriovenous fistula and arteriovenous shunt can fail due to stenosis, thrombosis, or infections. This review will recapitulate the vast and interdisciplinary scenario that characterizes hemodialysis vascular access creation and function, since adequate access management must be based on knowledge of the state of the art and on future perspectives. We also discuss recent developments to improve arteriovenous fistula creation and patency, the blood compatibility of arteriovenous shunt, needs to avoid infections, and potential development of tissue engineering applications in hemodialysis vascular access. The ultimate goal is to spread more knowledge in a critical area of medicine that is importantly affecting medical costs of renal replacement therapies and patients’ quality of life.

Paclitaxel drug-coated balloon angioplasty for the treatment of failing arteriovenous fistulas: a single-center experience

Objectives: To report our experience of angioplasty with Lutonix (Bard Peripheral Vascular, Inc., Tempe, AZ) drug-coated balloon (DCB) for the treatment of failing arteriovenous fistulas (AVF).Materials and methods: Retrospective, single-center analysis consisting of 14 patients treated with Lutonix paclitaxel DCBs in the period from July 2015 through April 2017. We analyzed technical success, clinical success, primary patency of the target lesion, primary patency of the dialysis circuit, and the rate of complications. Regular follow-up of AVF patency was realized by clinical examination and duplex ultrasonography. The Kaplan-Meier survival method was applied to determine the cumulative primary patency of the target lesion and the dialysis circuit.Results: Technical success was 100% and clinical success 92.9%. There were no major or minor complications. Cumulative target lesion primary patency after DCB was 69.2% at 6 months and 31.6% at 12 months. Cumulative vascular circuit primary patency was 61.5% at 6 months and 31.6% at 12 months.Conclusion: Compared to results reported in literature with plain old balloon angioplasty (POBA), Lutonix paclitaxel DCB angioplasty proved a short-term patency benefit in treatment of dialysis AVF stenosis.

KDOQI Clinical Practice Guideline for Vascular Access: 2019 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for hemodialysis vascular access since 1996. Since the last update in 2006, there has been a great accumulation of new evidence and sophistication in the guidelines process. The 2019 update to the KDOQI Clinical Practice Guideline for Vascular Access is a comprehensive document intended to assist multidisciplinary practitioners care for chronic kidney disease patients and their vascular access. New topics include the end-stage kidney disease "Life-Plan" and related concepts, guidance on vascular access choice, new targets for arteriovenous access (fistulas and grafts) and central venous catheters, management of specific complications, and renewed approaches to some older topics. Appraisal of the quality of the evidence was independently conducted by using a Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach, and interpretation and application followed the GRADE Evidence to Decision frameworks. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Comparative Effectiveness of Drug-Coated Balloon vs Balloon Angioplasty for the Treatment of Arteriovenous Fistula Stenosis: A Meta-analysis

Purpose: To compare the effectiveness and safety outcomes of drug-coated balloon angioplasty (DCBA) vs conventional balloon angioplasty (BA) for arteriovenous fistula (AVF) stenosis. Materials and Methods: A systematic review was conducted of PubMed and Embase databases from 1966 to May 2019 to identify English-language articles evaluating DCBA vs BA for the treatment of AVF stenosis. Data extracted from each study were synthesized to evaluate target lesion revascularization (TLR), technical success, and mortality for the 2 approaches. Meta-analyses were performed on these outcomes using random effects models to estimate the odds ratios (ORs) and 95% confidence intervals (CIs). Subgroup and sensitivity analyses were performed. Results: Twelve studies [6 randomized controlled trials (RCTs) and 6 cohort studies] comprising 979 patients were included in this meta-analysis. The pooled results showed that AVFs treated with DCBA had significantly fewer TLRs at 6 months (OR 0.31, 95% CI 0.14 to 0.69, p=0.004) and 12 months (OR 0.45, 95% CI 0.21 to 0.97, p=0.04) than BA. The 2 approaches had similar technical success rates (OR 0.22, 95% CI 0.03 to 1.43, p=0.11). Additionally, the pooled OR of 12-month mortality was 0.71 (95% CI 0.20 to 2.51, p=0.60), indicating no significant difference between DCBA and BA. Subgroup analysis based on study design showed the superiority of DCBA to BA in cohort studies but not RCTs, which had high heterogeneity. Significant publication bias was found in the cohort studies. Conclusion: In de novo or recurrent AVF stenosis, DCBA appears to be an effective procedure associated with lower 6- and 12-month TLR compared with BA. However, larger and randomized controlled studies are warranted to draw definitive conclusions.

Effects of Caveolin-1-ERK1/2 pathway on endothelial cells and smooth muscle cells under shear stress

Hemodynamic forces have an important role in venous intimal hyperplasia, which is the main cause of arteriovenous fistula dysfunction. Endothelial cells (ECs) constantly exposed to the shear stress of blood flow, converted the mechanical stimuli into intracellular signals, and interacted with the underlying vascular smooth muscle cells (VSMCs). Caveolin-1 is one of the important mechanoreceptors on cytomembrane, which is related to vascular abnormalities. Extracellular signal-regulated kinase1/2 (ERK1/2) pathway is involved in the process of VSMCs proliferation and migration. In the present study, we explore the effects of Caveolin-1-ERK1/2 pathway and uremia toxins on the endothelial cells and VSMCs following shear stress application. Different shear stress was simulated with a ECs/VSMCs cocultured parallel-plate flow chamber system. Low shear stress and oscillating shear stress up-regulated the expression of fibroblast growth factor-4, platelet-derived growth factor-BB, vascular endothelial growth factor-A, ERK1/2 phosphorylation in endothelial cells, and proliferation and migration of VSMCs but down-regulated the Caveolin-1 expression in endothelial cells. Uremia toxin induces the proliferation and migration of VSMCs but not in a Caveolin-1-dependent manner in the static environment. Low shear stress-induced proliferation and migration of VSMCs is inhibited by Caveolin-1 overexpression and ERK1/2 suppression. Shear stress-regulated VSMC proliferation and migration is an endothelial cells-dependent process. Low shear stress and oscillating shear stress exert atherosclerotic influences on endothelial cells and VSMCs. Low shear stress modulated proliferation and migration of VSMCs through Caveolin-1-ERK1/2 pathway, which suggested that Caveolin-1 and ERK1/2 can be used as a new therapeutic target for the treatment of arteriovenous fistula dysfunction.

Impact statement

Venous intimal hyperplasia is the leading cause of arteriovenous fistula (AVF) dysfunction. This article reports that shear stress-regulated vascular smooth muscle cells (VSMCs) proliferation and migration is an endothelial cell (EC)-dependent process. Low shear stress (LSS) and oscillating shear stress (OSS) exert atherosclerotic influences on the ECs and VSMCs. LSS-induced proliferation and migration of VSMCs is inhibited by Caveolin-1 overexpression and extracellular signal-regulated kinase1/2 (ERK1/2) suppression, which suggested that Caveolin-1 and ERK1/2 can be used as a new therapeutic target for the treatment of AVF dysfunction.

Role of Hypoxia and Metabolism in the Development of Neointimal Hyperplasia in Arteriovenous Fistulas

For patients with end-stage renal disease requiring hemodialysis, their vascular access is both their lifeline and their Achilles heel. Despite being recommended as primary vascular access, the arteriovenous fistula (AVF) shows sub-optimal results, with about 50% of patients needing a revision during the year following creation. After the AVF is created, the venous wall must adapt to new environment. While hemodynamic changes are responsible for the adaptation of the extracellular matrix and activation of the endothelium, surgical dissection and mobilization of the vein disrupt the vasa vasorum, causing wall ischemia and oxidative stress. As a consequence, migration and proliferation of vascular cells participate in venous wall thickening by a mechanism of neointimal hyperplasia (NH). When aggressive, NH causes stenosis and AVF dysfunction. In this review we show how hypoxia, metabolism, and flow parameters are intricate mechanisms responsible for the development of NH and stenosis during AVF maturation.

Notch signaling in bone marrow-derived FSP-1 cells initiates neointima formation in arteriovenous fistulas

Neointima formation is a major contributor to arteriovenous fistula (AVF) failure. We have previously shown that activation of the Notch signaling pathway contributes to neointima formation by promoting the migration of vascular smooth muscle cells (VSMCs) into the venous anastomosis. In the current study we investigated the mechanisms underlying the dedifferentiation and migration of VSMCs, and in particular the role of bone marrow-derived fibroblast specific protein 1 (FSP-1)+ cells, another cell type found in models of vascular injury. Using VSMC-specific reporter mice, we found that most of the VSMCs participating in AVF neointima formation originated from dedifferentiated VSMCs. We also observed infiltration of bone marrow-derived FSP-1+ cells into the arterial anastomosis where they could interact with VSMCs. In vitro, conditioned media from FSP-1+ cells stimulated VSMC proliferation and phenotype switching. Activated Notch signaling transformed FSP-1+ cells into type I macrophages and stimulated secretion of cytokines and growth factors. Pretreatment with a Notch inhibitor or knockout of the canonical downstream factor RBP-Jκ in bone marrow-derived FSP1+ cells decreased FSP1+ cell infiltration into murine AVFs, attenuating VSMC dedifferentiation and neointima formation. Our results suggest that targeting Notch signaling could provide a new therapeutic strategy to improve AVF patency.

Mineral Metabolism Disturbances and Arteriovenous Fistula Maturation

BACKGROUND

The arteriovenous fistula (AVF) is central to haemodialysis treatment, but up to half of surgically created AVF fail to mature. Chronic kidney disease often leads to mineral metabolism disturbances that may interfere with AVF maturation through adverse vascular effects. This study tested associations between mineral metabolism markers and vein histology at AVF creation and unassisted and overall clinical AVF maturation.

METHODS

Concentrations of fibroblast growth factor 23, parathyroid hormone, calcium, phosphate, and vitamin D metabolites: 1,25(OH)₂D, 24,25(OH)₂D, 25(OH)D, and bioavailable 25(OH)D were measured in pre-operative serum samples from 562 of 602 participants in the Haemodialysis Fistula Maturation Study, a multicentre, prospective cohort study of patients undergoing surgical creation of an autologous upper extremity AVF. Unassisted and overall AVF maturation were ascertained for 540 and 527 participants, respectively, within nine months of surgery or four weeks of dialysis initiation. Study personnel obtained vein segments adjacent to the portion of the vein used for anastomosis, which were processed, embedded, and stained for measurement of neointimal hyperplasia, calcification, and collagen deposition in the medial wall.

RESULTS

Participants in this substudy were 71% male, 43% black, and had a mean age of 55 years. Failure to achieve AVF maturation without assistance occurred in 288 (53%) participants for whom this outcome was determined. In demographic and further adjusted models, mineral metabolism markers were not significantly associated with vein histology characteristics, unassisted AVF maturation failure, or overall maturation failure, other than a biologically unexplained association of higher 24,25(OH)₂D with overall failure. This exception aside, associations were non-significant for continuous and categorical analyses and relevant subgroups.

CONCLUSIONS

Serum concentrations of measured mineral metabolites were not substantially associated with major histological characteristics of veins in patients undergoing AVF creation surgery, or with AVF maturation failure, suggesting that efforts to improve AVF maturation rates should increase attention to other processes such as vein mechanics, anatomy, and cellular metabolism among end stage renal disease patients.

Semiquantitative analysis of virtual histology derived from intravascular ultrasound images at vascular access stenosis

Vascular access failure, such as recurrent stenosis and thrombosis, is a major concern in patients with end-stage kidney disease. Neointimal hyperplasia development at the anastomosis site of outflow vessels is a primal cause for recurrent vascular access failure. We previously shed some lights into a role of vitamin D, which exerts a protective effect against neointimal hyperplasia formation. Virtual histology, derived from intravascular ultrasound technology, provides novel insights into plaque composition analysis in atherosclerotic diseases. However, there is so far a lack of evidence on the relation between virtual histology and pathophysiological findings. To elucidate this missing link, we comprehensively reviewed 10 chronic hemodialysis patients who underwent repeated intravascular ultrasound-guided balloon angioplasty. Their age, dialysis vintage, and follow-up period were 75.0 ± 4.24, 20.5 ± 2.12, and 11.5 ± 0.71 (mean ± standard deviation) years, respectively. Pathological cross-sectional analyses were performed using specimens from vascular access surgeries during the follow-up period. Interestingly, positive relation is found between virtual histology-constructed fibrous tissue and pathological neointimal hyperplasia. Strikingly, immunohistological analysis revealed that vitamin D receptor-positive myofibroblasts were abundantly distributed in the equivalent area to virtual histology fibrous tissue. Our 10-year follow-up data of resistant vascular access stenosis indicates strong correlation between vitamin D receptor-rich neointimal vessel hypertrophy and intravascular ultrasound-assisted virtual histological analysis. Intravascular ultrasound technology is one of the minimally invasive diagnostic tools to provide histologically relevant tissue structure information and help determine target vessel stenosis on vascular access.

Mineralocorticoid receptor: A hidden culprit for hemodialysis vascular access dysfunction

Hemodialysis vascular access dysfunction is a common and intractable problem in clinical practice with no definitive therapy yet available. As a key mediator of vascular and cardiac maladaptive remodeling, mineralocorticoid receptor (MR) plays a pivotal role in vascular fibrosis and intimal hyperplasia (IH) and is potentiated locally in hemodialysis vascular access following diverse injuries, like barotrauma, cannulation and shear stress. MR-related genomic and non-genomic pathways are responsible for triggering vascular smooth muscle cell activation, proliferation, migration and extracellular matrix overproduction. In endothelial cells, MR signaling diminishes nitric oxide production and its bioavailability, but amplifies reactive oxygen species, leading to an inflammatory state. Moreover, MR favors macrophage polarization towards a pro-inflammatory phenotype. In clinical settings like post-angioplasty or stenting restenosis, the beneficial effect of MR antagonists on vascular fibrosis and IH has been validated. In aggregate, therapeutic targeting of MR may provide a new avenue to prevent hemodialysis vascular access dysfunction.

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MR signaling is instrumental in both insufficient outward remodeling and exuberant inward remodeling of AVF.

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The effects of MR in VSMC, endothelial cell, and macrophage act synergistically to promote IH and vascular fibrosis in AVF.

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Pharmacological targeting of MR represents a novel therapeutic strategy to prevent hemodialysis vascular access dysfunction.

Treatment of juxta-anastomotic stenoses for failing distal radiocephalic arteriovenous fistulas: Drug-coated balloons versus angioplasty

The aim of our study is to report the results of two types (type A, type B) paclitaxel drug-coated balloon compared with standard percutaneous transluminal angioplasty in the treatment of juxta-anastomotic stenoses of mature but failing distal radiocephalic hemodialysis arteriovenous fistulas. Two groups of 26 and 44 patients treated with two different drug-coated balloon are compared with a control group of 86 treated with standard percutaneous transluminal angioplasty. A color Doppler ultrasound was performed to evaluate stenosis and for treatment planning. We assess primary patency, defined as the absence of dysfunction of the arteriovenous fistulas, patent lesion or residual stenosis < 30% and no need for further reintervention of target lesion. Primary patency and secondary patency are evaluated after 12 months with color Doppler ultrasound for the whole arteriovenous fistulas, defined as absolute (absolute primary patency, absolute secondary patency) and target lesion. Postprocedural technical and clinical success was 100%. After 12 months, absolute primary patency is 81.8% for type A, 84.1% type B, and 54.7% for standard percutaneous transluminal angioplasty; target lesion primary patency is 92% type A, 86.4% type B, and 62.8% standard percutaneous transluminal angioplasty; absolute secondary patency is 95.4% type A, 95.5% type B, and 80.7% standard percutaneous transluminal angioplasty; target lesion secondary patency is 100% type A, 97.7% type B, and 80.7% standard percutaneous transluminal angioplasty. All the patients treated with drug-coated balloon (type A + type B) have an absolute primary patency of 83.3%, a target lesion primary patency of 87.9%, an absolute secondary patency of 95.5%, and a target lesion secondary patency of 98.4%. Our study confirms that the use of drug-coated balloon, indiscriminately among different brands, improves primary patency with statistically significant difference in comparison with standard percutaneous transluminal angioplasty and decreases reintervention of target lesion in juxta-anastomotic stenoses of failing distal arteriovenous fistulas maintaining the radiocephalic fistula as long as possible.

Toward longitudinal studies of hemodynamically induced vessel wall remodeling

INTRODUCTION:

Autogenous arteriovenous fistula is the preferred vascular access for hemodialysis, but it has high rates of non-maturation and early failure due to vascular stenosis. Convincing evidence supports a key role of local hemodynamics in vascular remodeling, suggesting that unsteady and disturbed flow conditions may be related to stenosis formation in arteriovenous fistula. The purpose of our study was to explore the feasibility of coupling contrast-free magnetic resonance imaging and computational fluid dynamics in longitudinal studies to identify the role of local hemodynamic changes over time in inducing vessel wall remodeling in arteriovenous fistula.

METHODS:

We acquired contrast-free magnetic resonance imaging of arm vasculature at 1 week and 6 weeks after arteriovenous fistula creation in a 72-year-old patient. We then generated three-dimensional models and evaluated lumen cross-sectional area of arteriovenous fistula limbs. We performed high-resolution computational fluid dynamics to evaluate changes in local hemodynamics over time.

RESULTS:

Our contrast-free magnetic resonance imaging protocol provided good quality images in a short scan duration. We observed a homogeneous dilatation in the proximal artery, while there was a more pronounced lumen dilatation in the venous outflow as compared to a limited dilatation in the juxta-anastomotic vein. Furthermore, we observed a slight stabilization of the flow pattern over time, suggesting that vascular outward remodeling accommodates the flow to a more helicoidally phenotype.

CONCLUSION:

Coupling contrast-free magnetic resonance imaging and high-resolution computational fluid dynamics represents a promising approach to shed more light in the mechanisms of vascular remodeling and can be used for prospective clinical investigations aimed at identifying critical hemodynamic factors contributing to arteriovenous fistula failure.

Relaxin receptor deficiency promotes vascular inflammation and impairs outward remodeling in arteriovenous fistulas

The pathophysiology of arteriovenous fistula (AVF) maturation failure is not completely understood but impaired outward remodeling (OR) and intimal hyperplasia are thought to be contributors. This adverse vascular response after AVF surgery results from interplay between vascular smooth muscle cells (VSMCs), the extracellular matrix (ECM), and inflammatory cells. Relaxin (RLN) is a hormone that acts on the vasculature via interaction with RLN/insulin-like peptide family receptor 1 (RXFP1), resulting in vasodilatation, ECM remodeling, and decreased inflammation. In the present study, we evaluated the consequences of RXFP1 knockout ( Rxfp1-/-) on AVF maturation in a murine model of AVF failure. Rxfp1-/- mice showed a 22% decrease in vessel size at the venous outflow tract 14 d after AVF surgery. Furthermore, a 43% increase in elastin content was observed in the lesions of Rxfp1-/- mice and coincided with a 41% reduction in elastase activity. In addition, Rxfp1-/- mice displayed a 6-fold increase in CD45+ leukocytes, along with a 2-fold increase in monocyte chemoattractant protein 1 (MCP1) levels, when compared with wild-type mice. In vitro, VSMCs from Rxfp1-/- mice exhibited a synthetic phenotype, as illustrated by augmentation of collagen, fibronectin, TGF-β, and platelet-derived growth factor mRNA. In addition, VSMCs derived from Rxfp1-/- mice showed a 5-fold increase in cell migration. Finally, RXFP1 and RLN expression levels were increased in human AVFs when compared with unoperated cephalic veins. In conclusion, RXFP1 deficiency hampers elastin degradation and results in induced vascular inflammation after AVF surgery. These processes impair OR in murine AVF, suggesting that the RLN axis could be a potential therapeutic target for promoting AVF maturation.-Bezhaeva, T., de Vries, M. R., Geelhoed, W. J., van der Veer, E. P., Versteeg, S., van Alem, C. M. A., Voorzaat, B. M., Eijkelkamp, N., van der Bogt, K. E., Agoulnik, A. I., van Zonneveld, A.-J., Quax, P. H. A., Rotmans, J. I. Relaxin receptor deficiency promotes vascular inflammation and impairs outward remodeling in arteriovenous fistulas.

Restoration of Autologous Arteriovenous Fistula by Removal of the Occluded Short Venous Part and Venovenous End-To-End Anastomosis in a Hemodialysis Patient

Standard salvage procedures for occuluded autologous arteriovenous fistula (AVF) in a hemodialysis patient are endovascular and/or surgical therapy. When endovascular therapy and thrombectomy prove unsuccessful, it is most likely that creating a new AVF or arteriovenous graft will be considered. However, if the occuluded venous part is short, we have adopted an operative technique for repair of AVF by removal of the occluded short venous part and venovenous end-to-end anastomosis. To our knowledge, the efficacy and clinical course of restoration of AVF by the technique have not been reported to date. Here, we describe the technique and report the successful treatment of a hemodialysis patient who developed AVF occlusion.

Randomized pilot study to compare metal needles versus plastic cannulae in the development of complications in hemodialysis access

BACKGROUND

Hemodialysis requires needle insertions every treatment. Needle injury (mechanical or hemodynamic) may cause complications (aneurysms/stenosis) that compromise dialysis delivery requiring interventions. Metal needles have a sharp slanted "V"-shaped cutting tip; plastic cannulae have a dull round tip and four side holes. Preliminary observations demonstrated a difference in intradialytic blood flow images and mean Doppler velocities at cannulation sites between the two devices. Complications from mechanical and hemodynamic trauma requiring interventions were compared in each group.

MATERIALS AND METHODS

In all, 33 patients (13 females and 17 new accesses) were randomized to metal group (n = 17) and plastic group (n = 16). Mechanical trauma was minimized by having five nurses performing ultrasound-guided cannulations. Complications were identified by the clinician and addressed by the interventionalists, both blinded to study participation. Patients were followed for up to 12 months.

RESULTS

Baseline characteristics were not significant. Procedures to treat complications along cannulation segments increased from 0.41 to 1.29 per patient (metal group) and decreased from 1.25 to 0.69 per patient (plastic group; p = 0.004). The relative risks of having an intervention (relative risk = 1.5, 95% confidence interval = 0.88-2.67) and having an infiltration during hemodialysis (relative risk = 2.26, 95% confidence interval = 1.03-4.97) were higher for metal needles. Time to first intervention trended in favor of plastic cannula (p = 0.069). Cost of supplies for these interventions was approximately CAD$20,000 lower for the plastic group.

CONCLUSION

Decreased burden of illness related to cannulation (less infiltrations during hemodialysis) and Qb were associated with plastic cannulae. Decreased procedure costs were suggested during the study period in the plastic group.

Similar degree of intimal hyperplasia in surgically detected stenotic and nonstenotic arteriovenous fistula segments: a preliminary report

BACKGROUND

Intimal hyperplasia has been historically associated with improper venous remodeling and stenosis after creation of an arteriovenous fistula. Recently, however, we showed that intimal hyperplasia by itself does not explain the failure of maturation of 2-stage arteriovenous fistulas. We seek to evaluate whether intimal hyperplasia plays a role in the development of focal stenosis of an arteriovenous fistula.

METHODS

This study compares intimal hyperplasia lesions in stenotic and nearby nonstenotic segments collected from the same arteriovenous fistula. Focal areas of stenosis were detected in the operating room in patients (n= 14) undergoing the second-stage vein transposition procedure. The entire vein was inspected, and areas of stenosis were visually located with the aid of manual palpation and hemodynamic changes in the vein peripheral and central to the narrowing. Stenotic and nonstenotic segments were documented by photography before tissue collection (14 tissue pairs). Intimal area and thickness, intima-media thickness, and intima to media area ratio were measured in hematoxylin and eosin stained cross-sections followed by pairwise statistical comparisons.

RESULTS

The intimal area in stenotic and nonstenotic segments ranged from 1.25 to 11.61 mm² and 1.29 to 5.81 mm², respectively. There was no significant difference between these 2 groups (P=.26). Maximal intimal thickness (P=.22), maximal intima-media thickness (P=.13), and intima to media area ratio (P=.73) were also similar between both types of segments.

CONCLUSION

This preliminary study indicates that postoperative intimal hyperplasia by itself is not associated with the development of focal venous stenosis in 2-stage fistulas.

Smooth Muscle Nitric Oxide Responsiveness and Clinical Maturation of Hemodialysis Arteriovenous Fistulae

The arteriovenous fistula is the preferred type of hemodialysis vascular access for patients with end-stage renal disease, but a high proportion of newly created fistulas fail to mature for use. Stenosis caused by neointimal hyperplasia often is present in fistulas with maturation failure, suggesting that local mechanisms controlling vascular smooth muscle cell (SMC) migration and proliferation are important contributors to maturation failure. SMCs cultured from explants of vein tissue obtained at the time of fistula creation from 19 patients with end-stage renal disease were studied to determine whether smooth muscle responsiveness to nitric oxide is associated with fistula maturation outcomes. Nitric oxide-induced inhibition of smooth muscle cell migration, but not proliferation, was greater in cells from patients with subsequent fistula maturation success than from patients with subsequent fistula maturation failure (mean inhibition percentage, 17 versus 5.7, respectively; P = 0.035). Impaired nitric oxide responsiveness was associated with oxidation of the calcium regulatory protein, sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA), and was reversed by overexpressing SERCA (1.8-fold increase in inhibition, P = 0.0128) or down-regulating Nox4-based NADPH oxidase (2.3-fold increase in inhibition; P = 0.005). Our data suggest that the nitric oxide responsiveness of SMC migration is associated with fistula maturation success and raises the possibility that therapeutic restoration of nitric oxide responsiveness through manipulation of local mediators may prevent fistula maturation failure.

Dual Function for Mature Vascular Smooth Muscle Cells During Arteriovenous Fistula Remodeling

BACKGROUND

The arteriovenous fistula (AVF) is the preferred form of hemodialysis access for patients with chronic kidney disease. However, AVFs are associated with significant problems including high incidence of both early and late failures, usually attributed to inadequate venous arterialization and neointimal hyperplasia, respectively. Understanding the cellular basis of venous remodeling in the setting of AVF could provide targets for improving AVF patency rates.

METHODS AND RESULTS

A novel vascular smooth muscle cell (VSMC) lineage tracing reporter mouse, Myh11-Cre/ERT2-mTmG, was used to track mature VSMCs in a clinically relevant AVF mouse model created by a jugular vein branch end to carotid artery side anastomosis. Prior to AVF surgery, differentiated medial layer VSMCs were labeled with membrane green fluorescent protein (GFP) following tamoxifen induction. Four weeks after AVF surgery, we observed medial VSMC layer thickening in the middle region of the arterialized vein branch. This thickened medial VSMC layer was solely composed of differentiated VSMCs that were GFP+/MYH11+/Ki67-. Extensive neointimal hyperplasia occurred in the AVF region proximal to the anastomosis site. Dedifferentiated VSMCs (GFP+/MYH11-) were a major cellular component of the neointima. Examination of failed human AVF samples revealed that the processes of VSMC phenotypic modulation and intimal hyperplasia, as well as medial VSMC layer thickening, also occurred in human AVFs.

CONCLUSIONS

We demonstrated a dual function for mature VSMCs in AVF remodeling, with differentiated VSMCs contributing to medial wall thickening towards venous maturation and dedifferentiated VSMCs contributing to neointimal hyperplasia. These results provide valuable insights into the mechanisms underlying venous adaptations during AVF remodeling.

Surgical technique determines the outcome of the Brescia/Cimino AVF

Over the past 50 years, since Dr. Appel performed the first internal vascular access procedure for hemodialysis, the distal radiocephalic arteriovenous fistula continues to be the access of choice. Over time, failure to maturation has evolved as a major problem associated with this procedure depriving its benefits to many patients with end-stage renal disease. A variable incidence of this problem within similar patients suggests that surgical technique may play an important role in the development of non-maturation. Evaluating the current surgical techniques based on the hemodynamic consequences of anatomic and physiologic alterations following this procedure highlights the role of surgical technique in mitigating or reducing complications. Piggy-back straight line on-lay, a technique that helps to tailor the blood flow and reduce the oscillatory shear stress appears to reduce the incidence of early juxta-anastomotic problems, which contribute significantly to the problem of non-maturation.