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.

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

Arteriovenous fistulae (AVF) fail to mature more frequently in female patients compared with male patients, leading to inferior outcomes and decreased utilization. Since our mouse AVF model recapitulates sex differences in human AVF maturation, we hypothesized that sex hormones mediate these differences during AVF maturation. C57BL/6 mice (9-11 wk) were treated with aortocaval AVF surgery and/or gonadectomy. AVF hemodynamics were measured via ultrasound (days 0-21). Blood was collected for FACS and tissue for immunofluorescence and ELISA (days 3 and 7); wall thickness was assessed by histology (day 21). Inferior vena cava shear stress was higher in male mice (P = 0.0028) after gonadectomy, and they had increased wall thickness (22.0 ± 1.8 vs. 12.7 ± 1.2 µm; P < 0.0001). Conversely, female mice had decreased wall thickness (6.8 ± 0.6 vs. 15.3 ± 0.9 µm; P = 0.0002). Intact female mice had higher proportions of circulating CD3+ T cells on day 3 (P = 0.0043), CD4+ (P = 0.0003) and CD8+ T cells (P = 0.005) on day 7, and CD11b+ monocytes on day 3 (P = 0.0046). After gonadectomy, these differences disappeared. In intact female mice, CD3+ T cells (P = 0.025), CD4+ T cells (P = 0.0178), CD8+ T cells (P = 0.0571), and CD68+ macrophages (P = 0.0078) increased in the fistula wall on days 3 and 7. This disappeared after gonadectomy. Furthermore, female mice had higher IL-10 (P = 0.0217) and TNF-α (P = 0.0417) levels in their AVF walls than male mice. Sex hormones mediate AVF maturation, suggesting that hormone receptor signaling may be a target to improve AVF maturation.NEW & NOTEWORTHY After arteriovenous fistula creation, females have lower rates of maturation and higher rates of failure than males. In a mouse model of venous adaptation that recapitulates human fistula maturation, sex hormones may be mechanisms of the sexual dimorphism: testosterone is associated with reduced shear stress, whereas estrogen is associated with increased immune cell recruitment. Modulating sex hormones or downstream effectors suggests sex-specific therapies and could address disparities in sex differences in clinical outcomes.

Control of Hexamerization, Assembly, and Excluded Strand Specificity for the Sulfolobus solfataricus MCM Helicase.

A growing body of evidence supports a steric exclusion and wrapping model for DNA unwinding in which hexameric helicases interact with the excluded single-stranded DNA (ssDNA) in addition to the encircled strand. Interactions with the excluded ssDNA have been shown to be mediated primarily by electrostatic interactions, but base stacking with surface-exposed tyrosine residues is an alternative hypothesis. Here, we mutated several external tyrosine and positively charged residues from full-length Sulfolobus solfataricus MCM along the proposed path of excluded strand binding and assessed their impact on DNA unwinding. Four of the five tyrosine residues had significant decreases in their level of unwinding, and one, Y519A, located within the α/ß-α linker region of the C-terminal domain, had the most severe perturbation attributed to the disruption of hexamerization. The Y519 mutant exhibits an enhanced and stabilized secondary structure that is modulated by temperature, binding DNA with a higher apparent affinity and suggesting a pathway for hexameric assembly. Hydrogen/deuterium exchange coupled to mass spectrometry was used to map deuterium uptake differences between wild-type and Y519A apo structures highlighting global differences in solvent accessible areas consistent with altered quaternary structure. Two of the five electrostatic mutants had significantly reduced levels of DNA unwinding and combined with previous mutations better define the exterior binding path. The importance of the electrostatic excluded strand interaction was confirmed by use of morpholino DNA substrates that showed analogous reduced unwinding rates. These results better define the hexameric assembly and influence of the excluded strand interactions in controlling DNA unwinding by the archaeal MCM complex.

DNA Interactions Probed by Hydrogen-Deuterium Exchange (HDX) Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Confirm External Binding Sites on the Minichromosomal Maintenance (MCM) Helicase.

The archaeal minichromosomal maintenance (MCM) helicase from Sulfolobus solfataricus (SsoMCM) is a model for understanding structural and mechanistic aspects of DNA unwinding. Although interactions of the encircled DNA strand within the central channel provide an accepted mode for translocation, interactions with the excluded strand on the exterior surface have mostly been ignored with regard to DNA unwinding. We have previously proposed an extension of the traditional steric exclusion model of unwinding to also include significant contributions with the excluded strand during unwinding, termed steric exclusion and wrapping (SEW). The SEW model hypothesizes that the displaced single strand tracks along paths on the exterior surface of hexameric helicases to protect single-stranded DNA (ssDNA) and stabilize the complex in a forward unwinding mode. Using hydrogen/deuterium exchange monitored by Fourier transform ion cyclotron resonance MS, we have probed the binding sites for ssDNA, using multiple substrates targeting both the encircled and excluded strand interactions. In each experiment, we have obtained >98.7% sequence coverage of SsoMCM from >650 peptides (5-30 residues in length) and are able to identify interacting residues on both the interior and exterior of SsoMCM. Based on identified contacts, positively charged residues within the external waist region were mutated and shown to generally lower DNA unwinding without negatively affecting the ATP hydrolysis. The combined data globally identify binding sites for ssDNA during SsoMCM unwinding as well as validating the importance of the SEW model for hexameric helicase unwinding.

A central arteriovenous fistula reduces systemic hypertension in a mouse model.

Objective: A central arteriovenous fistula (AVF) has been proposed as a potential novel solution to treat patients with refractory hypertension. We hypothesized that venous remodeling after AVF creation in the hypertensive environment reduces systemic blood pressure but results in increased AVF wall thickness compared with remodeling in the normotensive environment. Methods: A central AVF was performed in C57BL6/J mice previously made hypertensive with angiotensin II (Ang II); mice were sacrificed on postoperative day 7 or 21. Results: In mice treated with Ang II alone, the mean systolic blood pressure increased from 90 ± 5 mmHg to 160 ± 5 mmHg at day 21; however, in mice treated with both Ang II and an AVF, the blood pressure decreased with creation of an AVF. There were significantly more PCNA-positive cells, SM22α/PCNA-positive cells, collagen I deposition, and increased Krüppel-like Factor 2 immunoreactivity in hypertensive mice with an AVF compared with normotensive mice with an AVF. Conclusions: These data show that a central AVF decreases systemic hypertension as well as induces local alterations in venous remodeling.

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.

Computer Science meets Vascular Surgery: Keeping a pulse on artificial intelligence.

Artificial intelligence (AI)-based technologies have garnered interest across a range of disciplines in the past several years, with an even more recent interest in various health care fields, including Vascular Surgery. AI offers a unique ability to analyze health data more quickly and efficiently than could be done by humans alone and can be used for clinical applications such as diagnosis, risk stratification, and follow-up, as well as patient-used applications to improve both patient and provider experiences, mitigate health care disparities, and individualize treatment. As with all novel technologies, AI is not without its risks and carries with it unique ethical considerations that will need to be addressed before its broad integration into health care systems. AI has the potential to revolutionize the way care is provided to patients, including those requiring vascular care.

2023 Vascular Research Initiatives Conference: Structural and Immune Cells in Vascular Disease.

The 2023 Vascular Research Initiatives Conference (VRIC) was held in Boston, Massachusetts, and coincided with the first day of Vascular Discovery 2023, hosted by the American Heart Association. VRIC attracts vascular clinicians, surgeon-scientists, and basic science researchers to a common arena to facilitate the exchange of basic and translational science to stimulate and inspire participants to study and find solutions to vascular conditions. The theme of the conference this year was "Structural and Immune Cells in Vascular Disease." Abstract sessions focused on venous disease, vascular regeneration, stem cells and wound healing, aortopathies, and the role of the immune system in atherosclerosis. A moderated translational science panel included talks from Dr Chiara Giannarelli and Dr Bhama Ramkhelawon. Recipients of Society for Vascular Surgery partner grants and National Institutes of Health K08 awardees presented their progress reports, and the Resident Research and VRIC Trainee Awardees were acknowledged. The Alexander W. Clowes Distinguished Lecture, entitled "Co-stimulatory Immune Checkpoints in Atherosclerosis: Novel Immunotherapeutic Targets to Combat Atherosclerotic Cardiovascular Disease" was given by Dr Ester Lutgens. VRIC continues to foster interdisciplinary collaborations across the translational field of vascular disease.

Dietary Intake and Omega-3 DHA Status in Pregnant Women Who Are Overweight.

OBJECTIVE: To estimate dietary intake of pregnant women who are overweight, assess their omega-3 docosahexaenoic acid (DHA) status, and compare results between Black and White women. DESIGN: Cross-sectional study with a longitudinal component (dietary assessment). SETTING: Outpatient clinics at Woman's Hospital, Baton Rouge, Louisiana and telephone calls. PARTICIPANTS: Pregnant women (N = 21) who were overweight (body mass index = 25.0-29.9 kg/m2). METHODS: Repeated 24-hour dietary recalls using the University of Minnesota Nutrition Data System for Research were conducted to determine nutrient intakes. Red blood cell fatty acids were analyzed with gas chromatography to determine omega-3 DHA status. Descriptive statistics, one- and two-sample t tests, Fisher's exact tests, chi-square test, and analysis of covariance were used to analyze data. RESULTS: On average, participants consumed 72 ± 63 mg omega-3 DHA/day. Age, race, and socioeconomic status did not affect the probability of achieving recommended omega-3 DHA dietary intake (p > .05). Black women had lower omega-3 DHA status (7.98 ± 0.94 weight percentage) than White women (9.29 ± 1.68 weight percentage; p ≤ .05). CONCLUSION: Analysis of our data suggests a need for nutrition education regarding the benefits of omega-3 DHA consumption during pregnancy for women of childbearing age. The current finding warrants further exploration.