Sex hormones impact early maturation and immune response in the arteriovenous fistula mouse model

Sustained tenascin-C expression drives neointimal hyperplasia and promotes aortocaval fistula failure

End-stage kidney disease (ESKD) impacts over 740,000 individuals in the United States, with many patients relying on arteriovenous fistulae (AVF) for hemodialysis due to superior patency and reduced infections. However, AVF patency is reduced by thrombosis and neointimal hyperplasia, yielding a 1-yr patency of only 40%-50%. We hypothesized that tenascin-C (TNC), a regulator of inflammation and immune responses after injury, also regulates venous remodeling during AVF maturation. AVF were created in wild-type (WT) and Tnc knockout (Tnc-/-) mice, and proteomic analyses were conducted to identify protein changes between sham and AVF WT tissue. Immunofluorescence and Western blot assays compared venous tissue from WT and Tnc-/- mice. In vitro studies using human umbilical vein endothelial cells and human umbilical vein smooth muscle cells examined TNC-siRNA effects on thrombomodulin (THBD) and NF-κB. Macrophages from WT and Tnc-/- mice were assessed for anti-inflammatory phenotype polarization and tissue factor expression. TNC expression was spatially and temporally regulated in WT mice with AVF, and TNC colocalized with matrix remodeling but not with THBD expression; TNC expression was downregulated in patent AVF but sustained in occluded AVF, both in WT mice and human AVF specimens. Tnc-/- mice had reduced AVF patency, less wall thickening, and increased thrombosis, with increased THBD expression. In vitro, TNC-siRNA increased THBD and reduced NF-κB activation. Macrophages from Tnc-/- mice showed increased anti-inflammatory macrophage polarization and tissue factor expression, facilitating thrombosis. Sustained TNC expression drives neointimal hyperplasia and AVF failure by promoting a prothrombotic, inflammatory microenvironment. Targeting TNC pathways may enhance AVF patency and improve dialysis outcomes.NEW & NOTEWORTHY This study identifies Tenascin-C (TNC) as a key regulator of arteriovenous fistula (AVF) patency. TNC is spatially and temporally regulated, driving neointimal hyperplasia and thrombosis by promoting a prothrombotic, inflammatory microenvironment. In Tnc-/- mice, reduced TNC expression increased thrombomodulin and anti-inflammatory macrophage polarization but impaired wall thickening and AVF patency. These findings link sustained TNC expression to AVF failure and suggest that targeting TNC pathways could enhance AVF outcomes in patients requiring hemodialysis.

The role of cellular senescence in endothelial dysfunction and vascular remodelling in arteriovenous fistula maturation

Haemodialysis (HD) is often required for patients with end-stage renal disease. Arteriovenous fistulas (AVFs), a surgical procedure connecting an artery to a vein, are the preferred vascular access for HD due to their durability and lower complication rates. The aim of AVFs is to promote vein remodelling to accommodate increased blood flow needed for dialysis. However, many AVFs fail to mature properly, making them unsuitable for dialysis. Successful maturation requires remodelling, resulting in an increased luminal diameter and thickened walls to support the increased blood flow. After AVF creation, haemodynamic changes due to increased blood flow on the venous side of the AVF initiate a cascade of events that, when successful, lead to the proper maturation of the AVF, making it suitable for cannulation. In this process, endothelial cells play a crucial role since they are in direct contact with the frictional forces exerted by the blood, known as shear stress. Patients requiring HD often have other conditions that increase the burden of senescent cells, such as ageing, diabetes and hypertension. These senescent cells are characterized by irreversible growth arrest and the secretion of pro-inflammatory and pro-thrombotic factors, collectively known as the senescence-associated secretory phenotype (SASP). This accumulation can impair vascular function by promoting inflammation, reducing vasodilatation, and increasing thrombosis risk, thus hindering proper AVF maturation and function. This review explores the contribution of senescent endothelial cells to AVF maturation and explores potential therapeutic strategies to alleviate the effects of senescent cell accumulation, aiming to improve AVF maturation rates.

Adventitial Injection of Hyaluronic Acid/Sodium Alginate Hydrogel Loaded With IL-33 Antibody Decreases Neointimal Hyperplasia

INTRODUCTION

Neointimal hyperplasia is one of the persistent complications after vascular interventions, and is the major cause of treatment failure. Interleukin-33 (IL-33) emerges as a crucial factor in many biological processes and plays an important role in vascular diseases. Adventitial injection is catching attention for its effectiveness and fewer side effects. We hypothesize that targeting IL-33 by adventitial injection can be a therapeutic method to inhibit neointimal hyperplasia.

METHOD

IL-33 expression was examined in human vein graft. The hydrogel was fabricated by the interaction of hyaluronic acid, sodium alginate, and CaCO3; and phosphate buffered saline (PBS) or IL-33 antibody or recombinant IL-33 was mixed within the hydrogel uniformly. A rat aortic wire injury-induced neointimal hyperplasia model was developed; rats were divided into three groups and received an adventitial injection of a hydrogel loaded with PBS or IL-33 antibody or recombinant IL-33 after wire injury. Tissues were harvested at day 21 and analyzed by histology and immunohistochemical staining. Hydrogel loaded with PBS, IL-33 antibody, or IL-33 was also used in a mouse carotid artery ligation neointimal hyperplasia model.

RESULT

There was a high expression of IL-33 in human vein graft neointima. Hydrogel can be successfully injected into the aortic wall and is encapsulated by the adventitia. The hydrogel could be seen beneath the adventitia after adventitial injection and was partly degraded at day 21. There was a significantly thinner neointimal thickness and less proliferation and inflammation in the IL-33 antibody group compared to the control group. On the contrary, the IL-33 group has a thicker neointima, increased proliferation, and inflammation. The mouse carotid artery ligation model showed similar results.

CONCLUSIONS

IL-33 plays a role in arterial neointimal hyperplasia in both human and rodent models; adventitial injection of hydrogel loaded with IL-33 antibody can effectively decrease neointimal thickness. Neutralizing IL-33 by IL-33 antibody may be a potential therapeutic method to inhibit intimal hyperplasia after vascular interventions.

Heterogeneous gene expression during early arteriovenous fistula remodeling suggests that downregulation of metabolism predicts adaptive venous remodeling

Clinical outcomes of arteriovenous fistulae (AVF) for hemodialysis remain inadequate since biological mechanisms of AVF maturation and failure are still poorly understood. Aortocaval fistula creation (AVF group) or a sham operation (sham group) was performed in C57BL/6 mice. Venous limbs were collected on postoperative day 7 and total RNA was extracted for high throughput RNA sequencing and bioinformatic analysis. Genes in metabolic pathways were significantly downregulated in the AVF, whereas significant sex differences were not detected. Since gene expression patterns among the AVF group were heterogenous, the AVF group was divided into a 'normal' AVF (nAVF) group and an 'outliers' (OUT) group. The gene expression patterns of the nAVF and OUT groups were consistent with previously published data showing venous adaptive remodeling, whereas enrichment analyses showed significant upregulation of metabolism, inflammation and coagulation in the OUT group compared to the nAVF group, suggesting the heterogeneity during venous remodeling reflects early gene expression changes that may correlate with AVF maturation or failure. Early detection of these processes may be a translational strategy to predict fistula failure and reduce patient morbidity.

Disturbed flow in the juxta-anastomotic area of an arteriovenous fistula correlates with endothelial loss, acute thrombus formation, and neointimal hyperplasia

Clinical failure of arteriovenous neointimal hyperplasia (NIH) fistulae (AVF) is frequently due to juxta-anastomotic NIH (JANIH). Although the mouse AVF model recapitulates human AVF maturation, previous studies focused on the outflow vein distal to the anastomosis. We hypothesized that the juxta-anastomotic area (JAA) has increased NIH compared with the outflow vein. AVF was created in C57BL/6 mice without or with chronic kidney disease (CKD). Temporal and spatial changes of the JAA were examined using histology and immunofluorescence. Computational techniques were used to model the AVF. RNA-seq and bioinformatic analyses were performed to compare the JAA with the outflow vein. The jugular vein to carotid artery AVF model was created in Wistar rats. The neointima in the JAA shows increased volume compared with the outflow vein. Computational modeling shows an increased volume of disturbed flow at the JAA compared with the outflow vein. Endothelial cells are immediately lost from the wall contralateral to the fistula exit, followed by thrombus formation and JANIH. Gene Ontology (GO) enrichment analysis of the 1,862 differentially expressed genes (DEG) between the JANIH and the outflow vein identified 525 overexpressed genes. The rat jugular vein to carotid artery AVF showed changes similar to the mouse AVF. Disturbed flow through the JAA correlates with rapid endothelial cell loss, thrombus formation, and JANIH; late endothelialization of the JAA channel correlates with late AVF patency. Early thrombus formation in the JAA may influence the later development of JANIH.NEW & NOTEWORTHY Disturbed flow and focal endothelial cell loss in the juxta-anastomotic area of the mouse AVF colocalizes with acute thrombus formation followed by late neointimal hyperplasia. Differential flow patterns between the juxta-anastomotic area and the outflow vein correlate with differential expression of genes regulating coagulation, proliferation, collagen metabolism, and the immune response. The rat jugular vein to carotid artery AVF model shows changes similar to the mouse AVF model.

LncRNA-LncDACH1 mediated phenotypic switching of smooth muscle cells during neointimal hyperplasia in male arteriovenous fistulas

Arteriovenous fistulas (AVFs) are the most common vascular access points for hemodialysis (HD), but they have a high incidence of postoperative dysfunction, mainly due to excessive neointimal hyperplasia (NIH). Our previous studies have revealed a highly conserved LncRNA-LncDACH1 as an important regulator of cardiomyocyte and fibroblast proliferation. Herein, we find that LncDACH1 regulates NIH in AVF in male mice with conditional knockout of smooth muscle cell-specific LncDACH1 and in male mice model of AVF with LncDACH1 overexpression by adeno-associated virus. Mechanistically, silence of LncDACH1 activates p-AKT through promoting the expression of heat shock protein 90 (HSP90) and serine/arginine-rich splicing factor protein kinase 1 (SRPK1). Moreover, LncDACH1 is transcriptionally activated by transcription factor KLF9 that binds directly to the promoter region of the LncDACH1 gene. In this work, during AVF NIH, LncDACH1 is downregulated by KLF9 and promotes NIH through the HSP90/ SRPK1/ AKT signaling axis.

Sex as a biological variable for cardiovascular physiology

There have been ongoing efforts by federal agencies and scientific communities since the early 1990s to incorporate sex and/or gender in all aspects of cardiovascular research. Scientific journals provide a critical function as change agents to influence transformation by encouraging submissions for topic areas, and by setting standards and expectations for articles submitted to the journal. As part of ongoing efforts to advance sex and gender in cardiovascular physiology research, the American Journal of Physiology-Heart and Circulatory Physiology recently launched a call for papers on Considering Sex as a Biological Variable. This call was an overwhelming success, resulting in 78 articles published in this collection. This review summarizes the major themes of the collection, including Sex as a Biological Variable Within: Endothelial Cell and Vascular Physiology, Cardiovascular Immunity and Inflammation, Metabolism and Mitochondrial Energy, Extracellular Matrix Turnover and Fibrosis, Neurohormonal Signaling, and Cardiovascular Clinical and Epidemiology Assessments. Several articles also focused on establishing rigor and reproducibility of key physiological measurements involved in cardiovascular health and disease, as well as recommendations and considerations for study design. Combined, these articles summarize our current understanding of sex and gender influences on cardiovascular physiology and pathophysiology and provide insight into future directions needed to further expand our knowledge.

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.

Coil-assisted ethanol embolotherapy for refractory head and neck arteriovenous malformations with Onyx recrudescence: 10-Year experiences

OBJECTIVE

This study aimed to evaluate the outcomes of coil-assisted ethanol embolotherapy in recanalized head and neck arteriovenous malformations (HNAVMs) with dilated outflowing veins after Onyx treatment.

METHODS

Thirty-six patients with HNAVMs (18 females and 18 males with a mean age of 26.83 years) who experienced recurrence after Onyx embolization from October 2007 to October 2017 were included in this study. All patients underwent complete clinical and angiographic examinations. Further, each patient was classified based on the Schobinger stage before undergoing staged ethanol embolization. All patients were followed up for 5 years in-person at an interval of 3 months after discharge. The Kaplan-Meier method was used to perform the recurrence-free survival analysis.

RESULTS

Sixteen patients (44.4%) had Schobinger stage II HNAVMs, and the remaining patients had Schobinger stage III or IV (20/36 patients [55.6%]) HNAVMs. A total of 116 embolization procedures were performed, coils were applied in 107 procedures (92.2%) among patients with dilated outflowing veins. The dose of absolute ethanol was 16.39 mL per procedure in patients with Schobinger II HNAVMs, and 22.45 mL per procedure in patients with Schobinger III and IV HNAVMs (P = .024, 95% confidence interval, 1.128-5.009). During the 3-month evaluation, complete response was observed in 13 of 36 patients (36.1%), and partial response was observed in 23 of 36 patients (63.9%). The 5-year recurrence-free survival rate for patients who underwent Onyx treatment had improved 58.3% after ethanol embolization (95% confidence interval, 2.853-9.595; P < .0001).

CONCLUSIONS

Coil-assisted ethanol embolotherapy could treat refractory HNAVMs with Onyx recrudescence effectively.