Mineral Metabolism Disturbances and Arteriovenous Fistula Maturation

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.

Arteriovenous fistula creation by nephrologist and its outcomes: a prospective cohort study from Vietnam

BACKGROUND

Arteriovenous fistula (AVF) is the gold standard vascular access for effective hemodialysis. There is a growing interest in AVF creations performed by nephrologists to help reduce vascular surgeons' workload and enhance the timely treatment of patients with end-stage renal disease (ESRD). However, little is known about the feasibility and effectiveness of this approach in the low-resource settings. We examined the AVF surgical success and failure rates and associated predictors as well as early complications of AVF creations by a trained nephrologist with supports from vascular surgeons in Vietnam.

METHODS

A prospective cohort study was conducted on all adult ESRD patients at the Hemodialysis Department of Thong Nhat Hospital between April 2018 and October 2020. Information on demographic characteristics, comorbidities, and AVF creations was collected using a standardized questionnaire. All patients were followed up until 18 weeks post-surgery.

RESULTS

Among 100 patients with a mean age of 61.22 ± 17.11 years old, male accounted for 54%. Common causes of ESRD included hypertension (57%) and diabetes (32%). Just more than half (52%) of them reported having an AVF creation prior to ESRD. The successful first-time AVF creation rate was 98% (13/99, 95%CI: 8.74-21.18%). The primary and secondary AVF failure rates were 13.13% (13/99, 95%CI: 8.74-21.18%) and 16.87% (14/83, 95%CI: 10.32-26.25%), respectively. Early complications included bleeding (1%) and early thrombosis of the anastomosis (2%). There was a statistically significant association between age and primary AVF failure (P = 0.005) and between operation time and secondary AVF failure (P = 0.038).

CONCLUSIONS

AVF creations performed by well-trained and skilled interventional nephrologists with supports from vascular surgeons can result in favorable short- and long-term outcomes. It is important to follow up older patients and those with a long operation time to detect AVF failures. A standardized AVF creation training program and practice for nephrologists is needed to increase successful rates.

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.

Composite indices of femoral neck strength predicts the collapse of steroid-associated osteonecrosis of the femoral head: a retrospective study

PURPOSES

The purpose of this study was to investigate the predictive effect exerted by composite indices of femoral neck strength (compressive strength index (CSI), bending strength index (BSI) and impact strength index (ISI) on the femoral head collapse in steroid-associated ONFH patients.

METHODS

Nonoperative steroid-associated osteonecrosis of the femoral head (ONFH) patients from 2017 to 2019 were selected. The patients fell into the collapsed group and the non-collapsed group according to whether the femoral head collapsed. CSI, BSI and ISI were calculated. Moreover, bone turnover markers were measured. The statistical analysis was conducted on the predictive effects of composite indices of femoral neck strength and bone turnover index on ONFH collapse.

RESULTS

A total of 62 patients were included. The mean CSI, BSI and ISI were significantly lower in the collapsed group than those in the non-collapsed group (P < 0.05). CSI, ISI,t-P1NP and β-CTx were suggested as the protective risk factors for the femoral head collapse in ONFH patients. The ISI area under the curve values was 0. 878.The mean survival time of the hips of patients with ISI greater than 0.435 was greater (P < 0.05) than that of patients with ISI less than 0.435.

CONCLUSION

The composite indices of femoral neck strength can predict steroid-associated ONFH femoral head collapse more effectively than the bone turnover markers. The ISI value of 0.435 is a potential cut-off value, lower than this value can predict the early collapse of steroid-associated ONFH.

[Predictive effect of femoral neck strength composite indexes on femoral head collapse in non-traumatic osteonecrosis of femoral head]

Objective

To explore the predictive effect of the femoral neck strength composite indexes on femoral head collapse in non-traumatic osteonecrosis of the femoral head (ONFH) compared with bone turnover marker.

Methods

The non-traumatic ONFH patients who were admitted and received non-surgical treatment between January 2010 and December 2016 as the research object. And 96 cases (139 hips) met the selection criteria and were included in the study. There were 54 males (79 hips) and 42 females (60 hips), with an average age of 40.2 years (range, 22-60 years). According to whether the femoral head collapsed during follow-up, the patients were divided into collapsed group and non-collapsed group. The femoral neck width, hip axis length, height, body weight, and bone mineral density of femoral neck were measured. The femoral neck strength composite indexes, including the compressive strength index (CSI), bending strength index (BSI), and impact strength index (ISI), were calculated. The bone turnover marker, including the total typeⅠcollagen amino terminal elongation peptide (t-P1NP), β-crosslaps (β-CTx), alkaline phosphatase (ALP), 25 hydroxyvitamin D [25(OH)D], and N-terminal osteocalcin (N-MID), were measured. The age, gender, height, body weight, body mass index (BMI), bone mineral density of femoral neck, etiology, Japanese Osteonecrosis Investigation Committee (JIC) classification, femoral neck strength composite indexes, and bone turnover marker were compared between the two groups, and the influencing factors of the occurrence of femoral head collapse were initially screened. Then the significant variables in the femoral neck strength composite indexes and bone turnover marker were used for logistic regression analysis to screen risk factors; and the receiver operating characteristic (ROC) curve was used to determine the significant variables' impact on non-traumatic ONFH.

Results

All patients were followed up 3.2 years on average (range, 2-4 years). During follow-up, 46 cases (64 hips) had femoral head collapse (collapsed group), and the remaining 50 cases (75 hips) did not experience femoral head collapse (non-collapsed group). Univariate analysis showed that the difference in JIC classification between the two groups was significant ( Z=-7.090, P=0.000); however, the differences in age, gender, height, body weight, BMI, bone mineral density of femoral neck, and etiology were not significant ( P>0.05). In the femoral neck strength composite indexes, the CSI, BSI, and ISI of the collapsed group were significantly lower than those of the non-collapsed group ( P<0.05); in the bone turnover marker, the t-P1NP and β-CTx of the collapsed group were significantly lower than those of the non-collapsed group ( P<0.05); there was no significant difference in N-MID, 25(OH)D or ALP between groups ( P>0.05). Multivariate analysis showed that the CSI, ISI, and t-P1NP were risk factors for femoral collapse in patients with non-traumatic ONFH ( P<0.05). ROC curve analysis showed that the cut-off points of CSI, BSI, ISI, t-P1NP, and β-CTx were 6.172, 2.435, 0.465, 57.193, and 0.503, respectively, and the area under the ROC curve (AUC) were 0.753, 0.642, 0.903, 0.626, and 0.599, respectively.

Conclusion

The femoral neck strength composite indexes can predict the femoral head collapse in non-traumatic ONFH better than the bone turnover marker. ISI of 0.465 is a potential cut-off point below which future collapse of early non-traumatic ONFH can be predicted.

1α,25-Dihydroxyvitamin D3 Encapsulated in Nanoparticles Prevents Venous Neointimal Hyperplasia and Stenosis in Porcine Arteriovenous Fistulas

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)₂D₃ 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)₂D₃ in PLGA nanoparticles formed nanoparticles of uniform size that were similar to nanoparticles without 1α,25(OH)₂D₃. 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.

Bone turnover markers may predict the progression of osteonecrosis of the femoral head in aged males

Background

Recent studies suggest that the imbalance of bone metabolism is associated with the pathogenesis of osteonecrosis of the femoral head (ONFH). However, limited data exist on the bone turnover markers (BTMs) in these patients compared with the healthy control (HC) comprehensively.

Methods

In total, 196 participants aged 29-83 [53 patients were excluded, 70 nontraumatic ONFH (mean age 57.75±12.61; mean BMI 24.10±3.04) and 73 HC (mean age 54.04±11.12; mean BMI 23.67±3.64)] were recruited in our cross-sectional study. Osteocalcin (OC), t-P1NP (N-terminal procollagen type 1 extension pro-peptide), β-CTx (beta-isomerized type I collagen C-telopeptide breakdown products), 25-hydroxy-cholecalciferol, and parathormone (PTH) were measured using automated analyser.

Results

In comparison to controls, nontraumatic ONFH patients have lower 25(OH)D levels and higher levels of t-P1NP, β-CTx and OC (P<0.01). But there was no significant difference in PTH levels between these two groups. Logistic regression analysis revealed that low 25(OH)D and high t-P1NP were significantly associated with nontraumatic ONFH. ROC curve analysis showed the highest AUC for t-P1NP+25(OH)D model [t-P1NP+25(OH)D: 0.702, 95% CI: 0.620-0.776; t-P1NP: 0.621, 95% CI: 0.536-0.701; 25(OH)D: 0.678, 95% CI: 0.594-0.753]. With regard to the cutoff values calculated from the ROC curves, t-P1NP+25(OH)D model showed 64.29% sensitivity and 73.97% specificity. The deficiency of 25(OH)D occurred at all phases, and other BTMs were in a high rate during different phases according to the ARCO classification.

Conclusions

Both 25(OH)D deficiency and high t-P1NP were independent risk factors for nontraumatic ONFH. Our results suggest that BTMs, t-P1NP+25(OH)D model (t-P1NP ≥54.82 ng/mL and 25(OH)D ≤21.86 ng/mL), may facilitate to diagnose nontraumatic ONFH in aged male patients.