Citations

Introduction: Venous neointimal hyperplasia (VNH) is a major cause of hemodialysis arteriovenous fistula (AVF) vascular access failure. CX3CR1 mediates macrophage infiltration into the vasculature. Mice were used which had been genetically engineered to knock in the human CX3CR1 gene. Hypothesis: The hypothesis to be tested is that increased CX3CR1 gene expression results in VNH formation associated with AVF. Methods: We used 50 CX3CR1 knock in mice which were divided into 2 groups: 1. CX3CR1 antibody (30 mg/kg administered intraperitoneally two times per week) or vehicle (equal amount of volume used for CX3CR1 antibody administered intraperitoneally). AVFs were created by connecting the carotid artery to ipsilateral jugular vein 28 days after nephrectomy was performed to induce chronic kidney disease. Histology and Immunohistochemistry analysis at the outflow vein of AVF were performed to assess the pathological changes. Results: There was a significant decrease in neointima area in the outflow veins of AVF in CX3CR1 antibody group compared to the vehicle group at day 28 (43085 ± 12678 vs. 58963.4 ± 9273 μm 2 , P<0.05). There was a significant decrease in the ratio of neointima/media+adventitia area in the outflow veins of AVF in CX3CR1 antibody group compared to the vehicle group at day 28 (0.34 ± 0.1 vs. 0.61 ± 0.1, P<0.05). Cell density in neointima area in CX3CR1 group outflow veins was significantly lower than the vehicle group at day 14 (9600 ± 1000 vs. 13000 ± 3000 /mm 2 , P<0.01). There was a significant decrease in the average CD68-positive cell density in the CX3CR1 group outflow veins compared to the vehicle group (0.96 ± 0.34 vs.15.9 ±10, P<0.001) at day 14. Conclusion: Decreasing CX3CR1 significantly reduces macrophages infiltration and results in a significant reduction in VNH. This study provides a rationale for using CX3CR1 antibody in reducing VNH formation.

Abstract The hemodialysis population continues to grow. Although procedures for dialysis have existed for >60 years, significant challenges with vascular access to support hemodialysis persist. Failure of arteriovenous fistulas (AVFs) to mature, loss of AVF and graft patency, thrombosis, and infection hinder long-term access, and add extra health care costs and patient morbidity. There have been numerous innovations over the last decade aimed at addressing the issues. In this study, we review the literature and summarize the recent evolution of drug delivery, graft development, minimally invasive AVF creation, and stem-cell therapy for hemodialysis access.

Significance Statement Fractalkine receptor 1 (CX3CR1) mediates macrophage infiltration into the vasculature. In this study, we used humanized mice knocked in with the human CX3CR1 gene and inhibited CX3CR1 signaling using a variable domains of camelid heavy-chain-only molecule (BI 655088) to test the hypothesis that blockade of CX3CR1 results in less of the venous neointimal hyperplasia formation that is associated with arteriovenous fistula (AVF) failure. We also used human samples removed from failed AVFs combined with cell culture experiments. Our results demonstrate a novel role for CX3CR1 in reducing venous stenosis formation in AVFs. Background Fractalkine receptor 1 (CX3CR1) mediates macrophage infiltration and accumulation, causing venous neointimal hyperplasia (VNH)/venous stenosis (VS) in arteriovenous fistula (AVF). The effect of blocking CX3CR1 using an anti–human variable VHH molecule (hCX3CR1 VHH, BI 655088) on VNH/VS was determined using a humanized mouse in which the human CX3CR1 ( hCX3CR1 ) gene was knocked in (KI). Methods Whole-transcriptomic RNA sequencing with bioinformatics analysis was used on human stenotic AVF samples, C57BL/6J, hCX3CR1 KI mice with AVF and CKD, and in in vitro experiments to identify the pathways involved in preventing VNH/VS formation after hCX3CR1 VHH administration. Results Accumulation of CX3CR1 and CD68 was significantly increased in stenotic human AVFs. In C57BL/6J mice with AVF, there was increased Cx3cr1, Cx3cl1, Cd68 , and Tnf-α gene expression, and increased immunostaining of CX3CR1 and CD68. In hCX3CR1-KI mice treated with hCX3CR1 VHH molecule (KI-A), compared with vehicle controls (KI-V), there was increased lumen vessel area and patency, and decreased neointima in the AVF outflow veins. RNA-seq analysis identified TNF- α and NF- κ B as potential targets of CX3CR1 inhibition. In KI-A–treated vessels compared with KI-V, there was decreased gene expression of Tnf- α , Mcp-1 , and Il-1 β ; with reduction of Cx3cl1 , NF- κ B, and Cd68 ; decreased M1, Ly6C, smooth muscle cells, fibroblast-activated protein, fibronectin, and proliferation; and increased TUNEL and M2 staining. In cell culture, monocytes stimulated with PMA and treated with hCX3CR1 VHH had decreased TNF- α , CD68 , proliferation, and migration. Conclusions CX3CR1 blockade reduces VNH/VS formation by decreasing proinflammatory cues.

Significance Statement Expression of immediate early response gene X-1 ( Iex-1 ), also known as Ier-3, is increased in venous neointimal hyperplasia (VNH) and stenosis in hemodialysis arteriovenous fistulas (AVF). In a porcine model, 1α,25(OH) 2 D 3 , an inhibitor of Ier3, reduced VNH/stenosis formation. The 1α,25(OH) 2 D 3 released in the perivascular AVF space from poly(lactic-co-glycolic acid) nanoparticles embedded in a Pluronic F127 hydrogel (1,25 NP) reduced Ier3 gene and protein expression, MCP-1, CD68, HIF-1α, and VEGF-A immunostaining. Concomitantly, blood flow, lumen area, pulse wave velocity, and Young’s modulus increased, and neointima area, peak systolic velocity, and wall shear stress decreased in 1,25 NP–treated vessels. RNA sequencing analysis identified 242 genes involved in inflammatory and apoptotic pathways that had decreased expression in 1,25 NP vessels. Background Few therapies prevent venous neointimal hyperplasia (VNH) and venous stenosis (VS) formation in arteriovenous fistulas (AVF). Expression of the immediate early response gene X-1 ( Iex-1 ), also known as Ier3, is associated with VNH and stenosis in murine AVFs. The study aimed to determine if local release of Ier3 long-acting inhibitor 1α,25(OH) 2 D 3 from poly(lactic-co-glycolic acid) (PLGA) nanoparticles embedded in a thermosensitive Pluronic F127 hydrogel (1,25 NP) could affect VNH/VS formation in a large animal model. Methods Immediately after AVF creation in a porcine model of renal failure, 1,25 NP or vehicle control was injected into the adventitia space of AVF outflow veins. Scanning electron microscopy and dynamic light scattering characterized drug and control nanoparticles. Animals were sacrificed 3 and 28 days later for gene expression, immunohistologic, magnetic resonance imaging and angiography, and ultrasound analyses. Whole transcriptome RNA sequencing with differential gene expression analysis was performed on outflow veins of AVF. Results Encapsulation of 1α,25(OH) 2 D 3 in PLGA nanoparticles formed nanoparticles of uniform size that were similar to nanoparticles without 1α,25(OH) 2 D 3 . The 1,25 NP–treated AVFs exhibited lower VNH/VS, Ier3 gene expression, and IER-3, MCP-1, CD68, HIF-1α, and VEGF-A immunostaining, fibrosis, and proliferation. Blood flow and lumen area increased significantly, whereas peak systolic velocity and wall shear stress decreased. Treatment increased Young’s modulus and correlated with histologic assessment of fibrosis and with no evidence of vascular calcification. RNA sequencing analysis showed changes in the expression of genes associated with inflammatory, TGFβ1, and apoptotic pathways. Conclusions Local release of 1,25 NP improves AVF flow and hemodynamics, and reduces stenosis in association with reduction in inflammation, apoptosis, and fibrosis in a porcine model of arteriovenous fistula.

Deep venous thrombosis (DVT) is a severe complication of coronavirus disease 2019 (COVID-19). The purpose of this study was to study the prevalence, risk factors, anticoagulant therapy and sex differences of DVT in patients with COVID-19. The enrolled 121 hospitalized non-ventilator patients were confirmed positive for COVID-19. All suspected patients received color Doppler ultrasound (US) to screen for DVT in both lower extremities. Multivariate logistic regression was performed to identify risk factors related to DVT in COVID-19 patients. DVT was found in 48% of the asymptomatic COVID-19 patients with an increased PADUA or Caprini index using US scanning. The multivariate logistic regression determined that age (OR, 1.05; p = .0306), C-reactive protein (CRP) (OR, 1.02; p = .0040), and baseline D-dimer (OR, 1.42; p = .0010) were risk factors among COVID-19 patients. Although the most common DVT location was infrapopliteal (classes I and II), higher mortality in DVT-COVID-19 patients was confirmed. DVT-COVID-19 patients presented significant increases in CRP, neutrophil count, and D-dimer throughout the whole inpatient period compared to non-DVT-COVID-19 patients. Although anticoagulation therapy accelerated the recovery of lymphocytopenia in DVT patients, men DVT-COVID-19 patients with anticoagulant therapy showed significant higher CRP and neutrophil count vs. lymphocyte count (N/L) ratio, but showed lower lymphocyte counts compared to women DVT-COVID-19 patients. DVT is common in COVID-19 patients with high-risk factors, especially for older age and higher CRP and baseline D-dimer populations. It is important to consider sex differences in anticoagulant therapy among DVT-COVID-19 patients.

Background Venous neointimal hyperplasia and venous stenosis (VS) formation can result in a decrease in arteriovenous fistula (AVF) patency in patients with end‐stage renal disease. There are limited therapies that prevent VNH/VS. Systemic delivery of simvastatin has been shown to reduce VNH/VS but local delivery may help decrease the side effects associated with statin use. We determined if microparticles (MP) composed of cyclodextrins loaded with simvastatin (MP‐SV) could reduce VS/VNH using a murine arteriovenous fistula model with chronic kidney disease. Methods and Results Male C57BL/6J mice underwent nephrectomy to induce chronic kidney disease. Four weeks later, an arteriovenous fistula was placed and animals were randomized to 3 groups: 20 μL of PBS or 20 μL of PBS with 16.6 mg/mL of either MP or MP‐SV. Animals were euthanized 3 days later and the outflow veins were harvested for quantitative reverse transcriptase–polymerase chain reaction analysis and 28 days later for immunohistochemistical staining with morphometric analysis. Doppler ultrasound was performed weekly. Gene expression of vascular endothelial growth factor‐A ( Vegf‐A ), matrix metalloproteinase‐9 ( Mmp‐9 ), transforming growth factor beta 1 ( Tgf‐β1 ), and monocyte chemoattractant protein‐1 ( Mcp‐1 ) were significantly decreased in MP‐SV treated vessels compared with controls. There was a significant decrease in the neointimal area, cell proliferation, inflammation, and fibrosis, with an increase in apoptosis and peak velocity in MP‐SV treated outflow veins. MP‐SV treated fibroblasts when exposed to hypoxic injury had decreased gene expression of Vegf‐A and Mmp‐9 . Conclusions In experimental arteriovenous fistulas, periadventitial delivery of MP‐SV decreased gene expression of Vegf‐A , Mmp‐9 , Tgf‐β1 and Mcp‐1, VNH/VS, inflammation, and fibrosis.

Abstract Background Endoscopic cyanoacrylate (glue) injection of fundal varices may result in life-threatening embolic adverse events through spontaneous gastrorenal shunts (GRSs). Balloon-occluded retrograde transvenous occlusion (BRTOcc) of GRSs during cyanoacrylate injection may prevent serious systemic glue embolization through the shunt. This study aimed to evaluate the efficacy and safety of a combined endoscopic–interventional radiologic (BRTOcc) approach for the treatment of bleeding fundal varices. Methods We retrospectively analysed the data of patients who underwent the combined procedure for acutely bleeding fundal varices between January 2010 and April 2018. Data were extracted for patient demographics, clinical and endoscopic findings, technical details, and adverse events of the endoscopic–BRTOcc approach and patient outcomes. Results We identified 30 patients (13 [43.3%] women; median age 58 [range, 25–92] years) with gastroesophageal varices type 2 (53.3%, 16/30) and isolated gastric varices type 1 (46.7%, 14/30) per Sarin classification, and median clinical and endoscopic follow-up of 151 (range, 4–2,513) days and 98 (range, 3–2,373) days, respectively. The median volume of octyl-cyanoacrylate: Lipiodol injected was 7 (range, 4–22) mL. Procedure-related adverse events occurred in three (10.0%) patients, including transient fever, non-life-threatening pulmonary glue embolism, and an injection-site ulcer bleed. Complete gastric variceal obturation was achieved in 18 of 21 patients (85.7%) at endoscopic follow-up. Delayed variceal rebleeding was confirmed in one patient (3.3%) and suspected in two patients (6.7%). Although no procedure-related deaths occurred, the overall mortality rate was 46.7%, primarily from liver-disease progression and co-morbidities. Conclusion The combined endoscopic–BRTOcc procedure is a relatively safe and effective technique for bleeding fundal varices, with a high rate of variceal obturation and a low rate of serious adverse events.

Background Women have decreased hemodialysis arteriovenous fistula (AVF) maturation and patency rates. We determined the mechanisms responsible for the sex‐specific differences in AVF maturation and stenosis formation by performing whole transcriptome RNA sequencing with differential gene expression and pathway analysis, histopathological changes, and in vitro cell culture experiments from male and female smooth muscle cells. Methods and Results Mice with chronic kidney disease and AVF were used. Outflow veins were evaluated for gene expression, histomorphometric analysis, Doppler ultrasound, immunohistologic analysis, and fibrosis. Primary vascular smooth muscle cells were collected from female and male aorta vessels. In female AVFs, RNA sequencing with real‐time polymerase chain reaction analysis demonstrated a significant decrease in the average gene expression of BMP7 (bone morphogenetic protein 7) and downstream IL17Rb (interleukin 17 receptor b) , with increased transforming growth factor‐β1 ( Tgf‐β1) and transforming growth factor‐β receptor 1 ( Tgfβ‐r1) . There was decreased peak velocity, negative vascular remodeling with higher venous fibrosis and an increase in synthetic vascular smooth muscle cell phenotype, decrease in proliferation, and increase in apoptosis in female outflow veins at day 28. In vitro primary vascular smooth muscle cell experiments performed under hypoxic conditions demonstrated, in female compared with male cells, that there was increased gene expression of Tgf‐β1 , Tgfβ‐r1 , and Col1 with increased migration. Conclusions In female AVFs, there is decreased gene expression of BMP7 and IL17Rb with increased Tgf‐β1 and Tgfβ‐r1 , and the cellular and vascular differences result in venous fibrosis with negative vascular remodeling.

Abstract BackgroundDeep venous thrombosis (DVT) is a severe complication of the coronavirus disease 2019 (COVID-19). It may interfere with COVID-19 treatment and delay the recovery, but there is less data about the anticoagulant therapy and sex difference of VTE in patients with COVID-19. The purpose of this study is to study the prevalence, risk factors, anticoagulant therapy and sex difference of deep venous thrombosis (DVT) in patients with COVID-19.MethodsThe enrolled 121 patients were confirmed positive for COVID-19. All suspected patients with a high Caprini index (≥4) or PADUA index (≥4) received color Doppler Ultrasound (US) to screen DVT in both lower extremities. Clinical characteristics of DVT-COVID-19 patients were analyzed. Multivariate logistic regression was performed to identify risk factors related to DVT in COVID-19 patients. The distribution of DVT locations, anticoagulation therapy with sex difference, and the outcomes were also analyzed.ResultsDVT was found in 48% asymptomatic COVID-19 patients with increased PAUDA index or Caprini index by US scanning. Multivariate logistic regression determined that age, CRP and baseline D-dimer were risk factors among COVDI-19 patients. Although the most common DVT location was infrapopliteal (Class I and Class II), higher mortality in DVT-COVID-19 patients was confirmed. DVT-COVID-19 patients presented significant increases in the CRP, neutrophil count and D-dimer throughout the whole inpatient period compared to non-DVT-COVID-19 patients. Although anticoagulation therapy accelerated the recovery of lymphocytopenia condition in DVT patients, men DVT-COVID-19 patients showed higher CRP and neutrophil count vs. lymphocyte count (N/L) ratio but lower lymphocyte count compared to women DVT-COVID-19 patients. ConclusionsDVT is common in COVID-19 patients with high risk factors, especially for older age, higher CRP and baseline D-dimer populations. It is important to consider sex differences in the anticoagulant therapy among DVT-COVID-19 patients.

Significance Statement The arteriovenous fistula (AVF) is the preferred vascular access for hemodialysis, but several studies have shown that the primary patency rate at 1 year is approximately 60%. Percutaneous transluminal angioplasty (PTA) is the first line of treatment for AVF stenosis. However, the rate of restenosis after angioplasty is high and the primary patency rate after PTA treatment in AVFs at 6, 12, and 24 months is 61%, 42%, and 35%, respectively. Currently, no durable therapies prolong patency after angioplasty. This paper describes the use of adipose-derived mesenchymal stem cells to reduce stenosis after PTA treatment in a murine AVF model and provides rationale for potential clinical use. Background Percutaneous transluminal angioplasty (PTA) is the first line of treatment for stenosis in the arteriovenous fistula (AVF) created to provide access for hemodialysis, but resenosis still occurs. Transplants of adipose-derived mesenchymal stem cells (AMSCs) labeled with green fluorescent protein (GFP) to the adventitia could reduce pro-inflammatory gene expression, possibly restoring patency in a murine model of PTA for venous stenosis. Methods Partial nephrectomy of male C57BL/6J mice induced CKD. Placement of the AVF was 28 days later and, 14 days after that, PTA of the stenotic outflow vein was performed with delivery of either vehicle control or AMSCs (5×10 5 ) to the adventitia of the vein. Mice were euthanized 3 days later and gene expression for interleukin-1 beta (IL-1 β ) and tumor necrosis factor-alpha TNF- α ) analyzed, and histopathologic analysis performed on day 14 and 28. GFP (+) AMSCs were tracked after transplantation for up to 28 days and Doppler ultrasound performed weekly after AVF creation. Results Gene and protein expression of IL-1 β and TNF- α, fibrosis, proliferation, apoptosis and smooth muscle actin decreased, and the proportions of macrophage types (M2/M1) shifted in a manner consistent with less inflammation in AMSC-transplanted vessels compared to controls. After PTA, AMSC-treated vessels had significantly higher wall shear stress, average peak, and mean velocity, with increased lumen vessel area and decreased neointima/media area ratio compared to the control group. At 28 days after delivery, GFP (+) AMSC were present in the adventitia of the outflow vein. Conclusions AMSC-treated vessels had improved vascular remodeling with decreased proinflammatory gene expression, inflammation, and fibrotic staining compared to untreated vessels.