Hypoxia and hypoxia-inducible factors promote the development of neointimal hyperplasia in arteriovenous fistula

The prevalence of frailty among older adults with maintenance hemodialysis: a systematic

BACKGROUND

To evaluate the epidemiological data on the prevalence of frailty and prefrailty in individuals aged 60 years or older on MHD patients.

METHODS

PubMed, Web of Science, Embase, CNKI, WanFang, CBM, and VIP were searched from inception to February 2023 using combinations of subject words and free words. The methodological quality of all the selected studies was assessed using the Joanna Briggs Institute Critical Appraisal of Epidemiological Studies Checklist and Newcastle‒Ottawa Cohort Quality Assessment Scale. Random effects meta-analysis was used to pool estimates from different studies. Subgroup analysis and meta-regression were performed to explore potential sources of heterogeneity.

RESULTS

Of the 4,190 documents retrieved, 16 observational studies involving 2,446 participants from 8 countries were included in this systematic review. Among older adults receiving MHD, the overall prevalence of frailty and prefrailty was 41% (95% CI = 34-49%) and 37% (95% CI = 26-48%), respectively, with considerable heterogeneity. The pooled prevalence of frailty was greater among individuals aged > 70 years (45%) than among those aged ≤ 70 years (37%). However, subgroup analyses indicated that the confidence intervals for the age group overlap substantially.

CONCLUSION

Our research showed that the prevalence of frailty and prefrailty in older patients with MHD are high.

TRIAL REGISTRATION

The PROSPERO registration number for this study was CRD42023442569.

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.

Identification of the Neointimal Hyperplasia-Related LncRNA-mRNA-Immune Cell Regulatory Network in a Rat Carotid Artery Balloon Injury Model

Excessive neointimal hyperplasia (NIH) of coronary vessels in patients is the main cause of restenosis (RS) after percutaneous coronary intervention (PCI). This study aimed to identify the regulatory genes related to NIH in a rat carotid artery balloon injury model.We established a rat model and performed RNA sequencing to identify differentially expressed long non-coding RNAs (DElncRNAs) and differentially expressed message RNAs (DEmRNAs). Immune cells were analyzed using a murine Microenvironment Cell Population counter. The Pearson correlation between DEmRNAs, DElncRNAs, and immune cells was analyzed, followed by function enrichment analysis. Core DEmRNA was identified using Cytoscape. Next, a core lncRNAs-mRNAs-immune cell regulatory network was constructed. NIH-related gene sets from the Gene Expression Omnibus and GeneCards databases were used for validation.A total of 2,165 DEmRNAs and 705 DElncRNAs were identified in rat carotid artery tissue. Four key immune cells were screened out, including mast cells, vessels, endothelial cells, and fibroblasts. Based on the Pearson correlation between DEmRNAs, DElncRNAs and 4 key immune cells, 246 DEmRNAs and 93 DElncRNAs were obtained. DEmRNAs that interact with lncRNAs were mainly involved in the cell cycle, MAPK signaling pathway, and PI3K-Akt signaling pathway. A core lncRNA-mRNA-immune cell regulatory network was constructed, including 9 mRNAs, 4 lncRNAs, and fibroblasts. External datasets validation confirmed the significant correlation of both these mRNAs and lncRNAs with NIH.In this study, an lncRNA-mRNA-immune cell regulatory network related to NIH was constructed, which provided clues for exploring the potential mechanism of RS in cardiovascular diseases.

Frequent use of percutaneous transluminal angioplasty is not associated with reduced vascular access recreation in a longitudinal ecology study

The frequency of percutaneous transluminal angioplasty (PTA) procedures has substantially increased, but its effect on vascular access recreation (VAR) remains inconclusive. We conducted a population-based retrospective analysis of Taiwan hemodialysis (HD) centers from 2004 to 2012. Data was accumulated into center-level characteristics, including patients' demographics, baseline characteristics, PTA procedures, and VAR. Center-level characteristics were summarized annually using appropriate measures. A mixed model assessed the association between PTA frequency and VAR rates, considering within-center correlation and adjusting for potential confounders. A total of 82,005 patients (mean age 62.7 ± 13.9 years, 50.5% male, 48.5% with diabetes mellitus) from 820 HD centers were analyzed. From 2004 to 2012, PTA frequency significantly increased from 1.24 to 3.23 per 1000 HD sessions, while VAR rates did not decline as expected (0.5-0.8 per 1000 HD sessions). Compared with the HD centers of infrequent use of PTA (annual lowest quartile, range 0.39-1.20 per 1000 HD sessions), the ones of frequent use (annual highest quartile, range 2.52-5.10 per 1000 HD sessions) didn't have lower VAR (range 0.54-0.99 vs. 0.50-0.91 per 1000 HD sessions, respectively). After controlling the potential confounders, the HD centers' PTA rates were not significantly associated with lower VAR rates (- 2.6, 95% confidence interval: - 30.3; 25.0, p = 0.85). Frequent use of PTA does not seem to improve VA patency at the center level, with no significant association identified with lower VAR. The indication of PTA in daily practice should be re-evaluated in terms of its efficiency in lowering VAR.

The Pathological Mechanisms and Therapeutic Molecular Targets in Arteriovenous Fistula Dysfunction

The number of patients with end-stage renal disease (ESRD) requiring hemodialysis is increasing worldwide. Although arteriovenous fistula (AVF) is the best and most important vascular access (VA) for hemodialysis, its primary maturation failure rate is as high as 60%, which seriously endangers the prognosis of hemodialysis patients. After AVF establishment, the venous outflow tract undergoes hemodynamic changes, which are translated into intracellular signaling pathway cascades, resulting in an outward and inward remodeling of the vessel wall. Outward remodeling refers to the thickening of the vessel wall and the dilation of the lumen to accommodate the high blood flow in the AVF, while inward remodeling is mainly characterized by intimal hyperplasia. More and more studies have shown that the two types of remodeling are closely related in the occurrence and development of, and jointly determining the final fate of, AVF. Therefore, it is essential to investigate the underlying mechanisms involved in outward and inward remodeling for identifying the key targets in alleviating AVF dysfunction. In this review, we summarize the current clinical diagnosis, monitoring, and treatment techniques for AVF dysfunction and discuss the possible pathological mechanisms related to improper outward and inward remodeling in AVF dysfunction, as well as summarize the similarities and differences between the two remodeling types in molecular mechanisms. Finally, the representative therapeutic targets of potential clinical values are summarized.

Omentin reduces venous neointimal hyperplasia in arteriovenous fistula through hypoxia-inducible factor-1 alpha inhibition

Arteriovenous fistula (AVF) failure often involves venous neointimal hyperplasia (VNH) driven by elevated hypoxia-inducible factor-1 alpha (HIF-1α) in the venous wall. Omentin, known for its anti-inflammatory and anti-hyperplasia properties, has an uncertain role in early AVF failure. This study investigates omentin's impact on VNH using a chronic renal failure (CRF) rabbit model. The CRF rabbit model of AVF received omentin-expressing adenoviral vector or control β-gal vector to assess omentin's effects on VNH. Human vascular smooth muscle cells (HVSMCs), stimulated with tumor necrosis factor-α (TNF-α), were exposed to recombinant human omentin (Rh-OMT) to study its influence on cell proliferation and migration. The AMP-activated protein kinase (AMPK) inhibitor compound C and the mammalian target of rapamycin (mTOR) activator MHY1485 were employed to explore omentin's mechanisms in VNH reduction through HIF-1α inhibition. Omentin treatment reduced VNH in CRF rabbits, concomitant with HIF-1α down-regulation and the suppression of downstream factors, including vascular endothelial growth factor and matrix metalloproteinases. Rh-OMT inhibited TNF-α-induced HVSMC proliferation and migration by modulating both cell cycle and cell adhesion proteins. Additionally, omentin reduced HIF-1α expression through the AMPK/mTOR pathway activation. Notably, the blockade of AMPK/mTOR signaling reversed omentin-mediated inhibition of VNH, cell proliferation, and migration, both in vivo and in vitro. In conclusion, omentin mitigates VNH post-AVF creation by restraining HIF-1α via AMPK/mTOR signaling. Strategies boosting circulating omentin levels may offer promise in averting AVF failure.

Periadventitial biomaterials to improve arteriovenous fistula and graft outcomes

Periadventitial biomaterials have been employed for nearly three decades to promote adaptive venous remodeling following hemodialysis vascular access creation in preclinical models and clinical trials. These systems are predicated on the combination of scaffolds, hydrogels, and/or particles with therapeutics (small molecules, proteins, genes, and cells) to prevent venous stenosis and subsequent maturation failure. Periadventitial biomaterial therapies have evolved from simple drug delivery vehicles for traditional drugs to more thoughtful designs tailored to the pathophysiology of access failure. The emergence of tissue engineering strategies and gene therapies are another exciting new direction. Despite favorable results in experimental and preclinical studies, no periadventitial therapy has been clinically approved to improve vascular access outcomes. After conducting an exhaustive review of the literature, we identify the seminal studies and clinical trials that utilize periadventitial biomaterials and discuss the key features of each biomaterial format and their respective shortcomings as they pertain to access maturation. This review provides a foundation from which clinicians, surgeons, biologists, and engineers can refer to and will hopefully inspire thoughtful, translatable treatments to finally address access failure.

The rodent models of arteriovenous fistula

Arteriovenous fistulas (AVFs) have long been used as dialysis access in patients with end-stage renal disease; however, their maturation and long-term patency still fall short of clinical needs. Rodent models are irreplaceable to facilitate the study of mechanisms and provide reliable insights into clinical problems. The ideal rodent AVF model recapitulates the major features and pathology of human disease as closely as possible, and pre-induction of the uremic milieu is an important addition to AVF failure studies. Herein, we review different surgical methods used so far to create AVF in rodents, including surgical suturing, needle puncture, and the cuff technique. We also summarize commonly used evaluations after AVF placement. The aim was to provide recent advances and ideas for better selection and induction of rodent AVF models. At the same time, further improvements in the models and a deeper understanding of AVF failure mechanisms are expected.

Health care disparities involved in establishing functional arteriovenous fistula hemodialysis access

OBJECTIVE

Race-related disparities in outcomes associated with cardiovascular disease are well-documented. Arteriovenous fistula (AVF) maturation can be a challenge in establishing functional access in the population of patients with end-stage renal disease requiring hemodialysis. We sought to investigate the incidence of adjunctive procedures required to establish fistula maturation and evaluate the association with demographic factors including patient race.

METHODS

This study was a single-institution retrospective review of patients undergoing first-time AVF creation for hemodialysis from January 1, 2007, to December 31, 2021. Subsequent arteriovenous access interventions, such as percutaneous angioplasty, fistula superficialization, branch ligation and embolization, surgical revision, and thrombectomy, were recorded. The total number of interventions performed after index operation was recorded. Demographic data including age, sex, race, and ethnicity was recorded. The need for and number of subsequent interventions was evaluated using multivariable analysis.

RESULTS

A total of 669 patients were included in this study. Patients were 60.8% male and 39.2% female. Race was reported as White in 329 (49.2%), Black in 211 (31.5%), Asian in 27 (4.0%), and other/unknown in 102 (15.3%). Of the patients, 355 (53.1%) underwent no additional procedures after initial AVF creation, 188 (28.1%) underwent one additional procedure, 73 (10.9%) had two additional procedures, and 53 (7.9%) had three or more additional procedures. As compared with the White reference group, Black patients were at higher risk of having maintenance interventions (relative risk [RR], 1.900; P ≤ .0001) and additional AVF creation interventions (RR, 1.332; P = .05), and total interventions (RR, 1.551; P ≤ .0001).

CONCLUSIONS

Black patients were at significantly higher risk of undergoing additional surgical procedures, including both maintenance and new fistula creations, as compared with their counterparts of other racial groups. Further exploration of the root cause of these disparities is necessary to facilitate the achievement of equivalent high-quality outcomes across racial groups.

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.

Rationale and Trial Design of MesEnchymal Stem Cell Trial in Preventing Venous Stenosis of Hemodialysis Vascular Access Arteriovenous Fistula (MEST AVF Trial)

Background

Hemodialysis arteriovenous fistulas (AVFs) are the preferred vascular access for patients on hemodialysis. In the Hemodialysis Fistula Maturation Study, 44% of the patients achieved unassisted maturation of their fistula without needing an intervention. Venous neointimal hyperplasia (VNH) and subsequent venous stenosis are responsible for lack of maturation. There are no therapies that can prevent VNH/VS formation. The goal of this paper is to present the background, rationale, and trial design of an innovative phase 1/2 clinical study that is investigating the safety of autologous adipose-derived mesenchymal stem cells delivered locally to the adventitia of newly created upper extremity radiocephalic (RCF) or brachiocephalic fistula (BCF).

Methods

The rationale and preclinical studies used to obtain a physician-sponsored investigational new drug trial are discussed. The trial design and end points are discussed.

Results

This is an ongoing trial that will complete this year.

Conclusion

This is a phase 1/2 single-center, randomized trial that will investigate the safety and efficacy of autologous AMSCs in promoting maturation in new upper-extremity AVFs.Clinical Trial registration number: NCT02808208.

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.

Sex Differences in Inflammation During Venous Remodeling of Arteriovenous Fistulae

Vascular disorders frequently have differing clinical presentations among women and men. Sex differences exist in vascular access for hemodialysis; women have reduced rates of arteriovenous fistula (AVF) maturation as well as fistula utilization compared with men. Inflammation is increasingly implicated in both clinical studies and animal models as a potent mechanism driving AVF maturation, especially in vessel dilation and wall thickening, that allows venous remodeling to the fistula environment to support hemodialysis. Sex differences have long been recognized in arterial remodeling and diseases, with men having increased cardiovascular events compared with pre-menopausal women. Many of these arterial diseases are driven by inflammation that is similar to the inflammation during AVF maturation. Improved understanding of sex differences in inflammation during vascular remodeling may suggest sex-specific vascular therapies to improve AVF success.