Flow-induced high frequency vascular wall vibrations in an arteriovenous fistula: a specific stimulus for stenosis development?

Hemodialysis is the lifeline for nearly three million end stage renal disease patients worldwide. Native arteriovenous fistula (AVF) is the preferred vascular access, but 40% fail within 1 year. We recently demonstrated that AVFs harbour transitional flows and the goal of the present study was to investigate whether the associated high-frequency pressure fluctuations could promote vibrations within the vascular wall. We acquired MRI images and flow rates immediately after surgery in one patient and generated a 3D patient-specific model. High-fidelity fluid structure interaction simulations revealed the presence of wall vibrations in distinct frequency bands up to 200 Hz and amplitude of 200 μm. A sensitivity analysis to assess the impact of flow rates, and vascular wall stiffness and thickness, changes that typically occur during AVF maturation, confirmed the robustness of the results. Interestingly, the vibrations were always predominant at the anastomosis floor and on the inner venous side, which correlates with typical stenotic regions. As studies seeking to correlate aberrant stresses and vascular remodelling have been largely inconclusive, the focal colocalization between vibrations and stenosis may suggest an unknown mechanobiological process between high-frequency mechanical stresses within the vascular wall and adverse vascular remodelling.

Arteriovenous fistula creation with VasQTM device: A feasibility study to reveal hemodynamic implications

BACKGROUND

Arteriovenous fistula (AVF) is the preferred vascular access (VA) for hemodialysis, but it is still affected by high non-maturation and early failure rates due to stenosis development. Increasing evidence suggests that the presence of turbulent-like flow may play a key role, therefore, to stabilize the flow in the venous segment, an external support device (VasQTM) has been designed. The aim of this study was to provide preliminary evidence of VasQTM impact on AVF hemodynamics as compared to AVFs created with conventional surgery.

METHODS

In this pilot single-center prospective randomized study six patients were enrolled, three in the VasQ group and three in the control group. Contrast-free magnetic resonance imaging (MRI) scans were acquired at 3 days, 3 months and 1 year after AVF surgery and were used to generate 3D patient-specific models. Computational fluid dynamic (CFD) simulations were performed using pimpleFoam, imposing patient-specific flow waveforms derived from ultrasound (US) examinations at the inlet of the proximal and distal artery, and a traction-free condition at the venous outflow. Morphologic and hemodynamic changes occurring over time were compared between VasQ and control AVFs.

RESULTS

Our MRI protocol provided high-quality images suitable for reliable segmentation and reconstruction of patient-specific 3D models of AVFs at all three timepoints in four out of six patients. The VasQTM device maintained the angle between the artery and the vein almost unchanged over time, with a more stable flow in the AVFs supported by the device. In contrast, one of the AVFs of the control group evolved to an extreme dilatation of the vein and highly disturbed flow, while the other developed a stenosis in the juxta-anastomotic region.

CONCLUSIONS

This study demonstrated the feasibility of characterizing the morphological and hemodynamic changes occurring over time in AVFs created using the VasQTM device and provided preliminary evidence of the potential hemodynamic benefits of its use.

Functional Magnetic Resonance Imaging to Monitor Disease Progression: a prospective study in Patients with Primary Membranoproliferative Glomerulonephritis

INTRODUCTION

Primary membranoproliferative glomerulonephritis (MPGN) is a rare kidney disease with poor prognosis and no specific therapies. The disease heterogeneity and the difficulty of performing repeated kidney biopsies poses big challenges. This study investigates the correlation between non-contrast enhanced magnetic resonance imaging (MRI) and histologic and clinical findings in patients with primary MPGN.

METHODS

Patients with primary MPGN underwent baseline and 1-year kidney MRI in addition to biopsy and laboratory testing as part of a prospective MRI subproject of a clinical trial (ClinicalTrials.gov identifier NCT03723512). Diffusion-weighted and phase-contrast MRI were used to investigate kidney diffusivity and perfusion. Peritubular interstitial volume and fibrosis were quantified on kidney biopsies.

RESULTS

Seven patients with primary MPGN (18[17-21] years, 43% females) were included. Kidney biopsies showed variable degree of global and segmental glomerular sclerosis ([5-30]% and [10-60]%), mild interstitial fibrosis (<10%), and increased peritubular interstitial volume ([19-40]%). MRI and laboratory parameters changed very differently from patient to patient over 1 year. Peritubular interstitial volume and glomerular sclerosis negatively associated with renal blood flow (RBF)(rho = -0.81 and -0.77), and positively with renal vascular resistance (RVR)(rho = 0.65 and 0.73). Urinary albumin to creatinine ratio (uACR) negatively associated with RBF and filtration fraction (FF)(rho = -0.86 and -0.6), while positively with RVR (rho = 0.88). uACR decrease was associated with kidney diffusivity increase (rho = -0.5). Measured glomerular filtration rate (GFR) positively associated with kidney diffusivity, RBF, and FF (rho = 0.87, 0.85 and 0.59), while negatively with RVR (rho = -0.89); GFR increase was associated with kidney diffusivity, RBF, and FF increase (rho = 0.77, 0.7, and 0.7) and RVR decrease (rho = -0.7).

DISCUSSION/CONCLUSION

The strong correlation found between MRI and histologic and clinical findings, despite the rather limited number of patients, highlights MRI potential to monitor disease progression in patients with rare kidney disease.

Hemodynamics in AVF over time: A protective role of vascular remodeling toward flow stabilization

The mechanisms underlying vascular stenosis formation in the arteriovenous fistula (AVF) for hemodialysis (HD) remain mostly unknown. Several computational fluid dynamics (CFD) studies have suggested a potential role for unsteady flow in inducing intimal hyperplasia and AVF stenosis, but the majority of these observations have been limited to a single time point after surgical creation. The aim of the present study was to investigate the relation between hemodynamic conditions and AVF vascular remodeling through a CFD longitudinal study. Non contrast-enhanced MR images and Doppler Ultrasound (US) examinations were acquired at 3 days, 40 days, 6 months, 1 year, and 1.5 years after surgery in a 72-year male referred for native radio-cephalic AVF. Three-dimensional AVF models were generated and high fidelity CFD simulations were performed using pimpleFoam, setting patient-specific boundary conditions derived from US. Morphological and hemodynamic changes over time were then analyzed. Analysis of vessel morphology and hemodynamics during follow-up showed that the AVF had a successful maturation process, characterized by a massive arterial and venous dilatation within the 6 months after surgery, a corresponding increase in blood flow volume and important flow instabilities. Between 6 months and 1 year, a stenosis developed in the juxta-anastomotic vein and caused AVF failure at 1.5 years. The development of stenosis was paralleled by the regularization of blood flow velocity pattern and consequent decrease in the near-wall disturbed flow metrics. These results suggest that development of intimal hyperplasia and vessel stenosis, triggered by unsteady flow, could be the result of vascular inward remodeling toward regularization of turbulent-like flow.

Diffusion magnetic resonance imaging for kidney cyst volume quantification and non-cystic tissue characterisation in ADPKD

OBJECTIVES

Beyond total kidney and cyst volume (TCV), non-cystic tissue plays an important role in autosomal dominant polycystic kidney disease (ADPKD) progression. This study aims at presenting and preliminarily validating a diffusion MRI (DWI)-based TCV quantification method and providing evidence of DWI potential in characterising non-cystic tissue microstructure.

METHODS

T2-weighted MRI and DWI scans (b = 0, 15, 50, 100, 200, 350, 500, 700, 1000; 3 directions) were acquired from 35 ADPKD patients with CKD stage 1 to 3a and 15 healthy volunteers on a 1.5 T scanner. ADPKD classification was performed using the Mayo model. DWI scans were processed by mono- and segmented bi-exponential models. TCV was quantified on T2-weighted MRI by the reference semi-automatic method and automatically computed by thresholding the pure diffusivity (D) histogram. The agreement between reference and DWI-based TCV values and the differences in DWI-based parameters between healthy and ADPKD tissue components were assessed.

RESULTS

There was strong correlation between DWI-based and reference TCV (rho = 0.994, p < 0.001). Non-cystic ADPKD tissue had significantly higher D, and lower pseudo-diffusion and flowing fraction than healthy tissue (p < 0.001). Moreover, apparent diffusion coefficient and D values significantly differed by Mayo imaging class, both in the whole kidney (Wilcoxon p = 0.007 and p = 0.004) and non-cystic tissue (p = 0.024 and p = 0.007).

CONCLUSIONS

DWI shows potential in ADPKD to quantify TCV and characterise non-cystic kidney tissue microstructure, indicating the presence of microcysts and peritubular interstitial fibrosis. DWI could complement existing biomarkers for non-invasively staging, monitoring, and predicting ADPKD progression and evaluating the impact of novel therapies, possibly targeting damaged non-cystic tissue besides cyst expansion.

CLINICAL RELEVANCE STATEMENT

This study shows diffusion-weighted MRI (DWI) potential to quantify total cyst volume and characterise non-cystic kidney tissue microstructure in ADPKD. DWI could complement existing biomarkers for non-invasively staging, monitoring, and predicting ADPKD progression and evaluating the impact of novel therapies, possibly targeting damaged non-cystic tissue besides cyst expansion.

KEY POINTS

• Diffusion magnetic resonance imaging shows potential to quantify total cyst volume in ADPKD. • Diffusion magnetic resonance imaging might allow to non-invasively characterise non-cystic kidney tissue microstructure. • Diffusion magnetic resonance imaging-based biomarkers significantly differ by Mayo imaging class, suggesting their possible prognostic value.

The use of AVF.SIM system for the surgical planning of arteriovenous fistulae in routine clinical practice

BACKGROUND

The number of patients treated with hemodialysis (HD) in Europe is more than half a million and this number increases annually. The arteriovenous fistula (AVF) is the vascular access (VA) of first choice, but the clinical outcome is still poor. A consistent number of AVFs fails to reach the desired blood flow rate for HD treatment, while some have too high flow and risk for cardiac complications. Despite the skill of the surgeons and the possibility to use Ultrasound investigation for mapping arm vasculature, it is still not possible to predict the blood flow volume that will be obtained after AVF maturation.

METHODS

We evaluated the potential of using a computational model (AVF.SIM) to predict the blood flow volume that will be achieved after AVF maturation, within a multicenter international clinical investigation aimed at assessing AVF.SIM predictive power. The study population included 231 patients, with data on AVF maturation in 124 patients, and on long-term primary patency in 180 patients.

RESULTS

At 1 year of follow-up, about 60% of AVFs were still patent, with comparable primary patency in proximal and distal anastomosis. The correlation between predicted and measured blood flow volume in the brachial artery at 40 days after surgery was statistically significant, with an overall correlation coefficient of 0.58 (p < 0.001). The percent difference between measured and predicted brachial blood flow 40 days after surgery was less than 30% in 72% of patients investigated.

CONCLUSIONS

The results indicate that the use of the AVF.SIM system allowed to predict with a good accuracy the blood flow volume achievable after VA maturation, for a given location and type of anastomosis. This information may help in AVF surgical planning, reducing the AVFs with too low or too high blood flow, thus improving AVF patency rate and clinical outcome of renal replacement therapy.

COVID-19 teleassistance and teleconsultation: a matched case-control study (MIRATO project, Lombardy, Italy)

Background

During the COVID-19 pandemic, telemedicine has been recognised as a powerful modality to shorten the length of hospital stay and to free up beds for the sicker patients. Lombardy, and in particular the areas of Bergamo, Brescia, and Milan, was one of the regions in Europe most hit by the COVID-19 pandemic. The primary aim of the MIRATO project was to compare the incidence of severe events (hospital readmissions and mortality) in the first three months after discharge between COVID-19 patients followed by a Home-Based Teleassistance and Teleconsultation (HBTT group) program and those discharged home without Telemedicine support (non-HBTT group).

Methods

The study was designed as a matched case-control study. The non-HBTT patients were matched with the HBTT patients for sex, age, presence of COVID-19 pneumonia and number of comorbidities. After discharge, the HBTT group underwent a telecare nursing and specialist teleconsultation program at home for three months, including monitoring of vital signs and symptoms. Further, in this group we analysed clinical data, patients' satisfaction with the program, and quality of life.

Results

Four hundred twenty-two patients per group were identified for comparison. The median age in both groups was 70 ± 11 years (62% males). One or more comorbidities were present in 86% of the HBTT patients and 89% in the non-HBTT group (p = ns). The total number of severe events was 17 (14 hospitalizations and 3 deaths) in the HBTT group and 40 (26 hospitalizations and 16 deaths) in the non-HBTT group (p = 0.0007). The risk of hospital readmission or death after hospital discharge was significantly lower in HBTT patients (Log-rank Test p = 0.0002). In the HBTT group, during the 3-month follow-up, 5,355 teleassistance contacts (13 ± 4 per patient) were performed. The number of patients with one or more symptoms declined significantly: from 338 (78%) to 183 (45%) (p < 0.00001). Both the physical (ΔPCS12: 5.9 ± 11.4) component and the mental (ΔMCS12: 4.4 ± 12.7) component of SF-12 improved significantly (p < 0.0001). Patient satisfaction with the program was very high in all participants.

Conclusions

Compared to usual care, an HBTT program can reduce severe events (hospital admissions/mortality) at 3-months from discharge and improve symptoms and quality of life.

Clinical trial registration

www.ClinicalTrials.gov, NCT04898179.

Another piece in the puzzle of kidney fibrosis

Kidney fibrosis is a chronic physiomorphologic transformation of the renal parenchyma. Despite the known characteristics of the related structural and cellular changes, the mechanisms responsible for the initiation and progression of renal fibrosis are not completely understood. Development of efficient therapeutic drugs aimed at preventing the progressive loss of renal function requires an in-depth understanding of the complex phenomena associated with the pathophysiology of human diseases. The investigation of Li et al. provides novel evidence in this direction.

Surgical planning of arteriovenous fistulae in routine clinical practice: A machine learning predictive tool

BACKGROUND

Arteriovenous fistula (AVF) is the preferred vascular access (VA) for hemodialysis, but it is associated with high non-maturation and failure rates. Predicting patient-specific AVF maturation and postoperative changes in blood flow volumes (BFVs) and vessel diameters is of fundamental importance to support the choice of optimal AVF location and improve VA survival. The goal of this study was to employ machine learning (ML) in order to give physicians a fast and easy-to-use tool that provides accurate patient-specific predictions, useful to make AVF surgical planning decisions.

METHODS

We applied a set of ML approaches on a dataset of 156 patients. Both parametric and non-parametric ML approaches, taking preoperative data as input, were exploited to predict maturation, postoperative BFVs, and diameters. The best approach associated with lowest cross-validation errors between predictions and real measurements was then chosen to provide estimates and quantify prediction errors.

RESULTS

The k-NN was the best approach to predict brachial BFV, AVF maturation, and other VA variables, and it was also associated with the least computational effort. With this approach, the confusion matrices proved the high accuracy of the prediction for AVF maturation (96.8%) and the low absolute error distribution for the continuous BFV and diameter variables.

CONCLUSIONS

Our data-based approach provided accurate patient-specific predictions for different AVF configurations, requiring short computational time as compared to a physical model we previously developed. By supporting VA surgical planning, this fast computing approach could allow AVF surgical planning and help reducing the rate of non-maturation, which might ultimately have a broad impact on the management of hemodialysis patients.

Effects of Octreotide-Long-Acting Release Added-on Tolvaptan in Patients with Autosomal Dominant Polycystic Kidney Disease: Pilot, Randomized, Placebo-Controlled, Cross-Over Trial

BACKGROUND

Tolvaptan and octreotide-long-acting release (LAR) have renoprotective effects in autosomal dominant polycystic kidney disease (ADPKD) that are partially mediated by amelioration of compensatory glomerular hyperfiltration. We compared the effects of tolvaptan and octreotide-LAR combination therapy versus those of tolvaptan monotherapy in patients with ADPKD.

METHODS

This pilot, randomized, placebo-controlled, cross-over trial primarily compared the effects of 1- and 4-week treatments with octreotide-LAR (two 20-mg i.m. injections) or placebo (two i.m. 0.9% saline solution injections) added-on tolvaptan (up to 90 and 30 mg/d) on GFR (iohexol plasma clearance) in 19 consenting patients with ADPKD referred to a clinical research center in Italy. Analyses were intention-to-treat. The local ethical committee approved the study.

RESULTS

At 4 weeks, GFR significantly decreased by a median (interquartile range) of 3 (-1 to 5) ml/min per 1.73 m2 with tolvaptan and placebo (P=0.01) and by 7 (3-14) ml/min per 1.73 m2 with tolvaptan and octreotide-LAR (P=0.03). GFR changes during the two treatment periods differed by 2 (-5 to 14) ml/min per 1.73 m2 (P=0.28). At 1 week, GFR significantly decreased by 3 (0-7) ml/min per 1.73 m2 with tolvaptan and placebo (P=0.006) and by 10 (-6 to 16) ml/min per 1.73 m2 with tolvaptan and octreotide-LAR add-on therapy (P<0.001). GFR changes during the two treatment periods significantly differed by 3 (0-12) ml/min per 1.73 m2 (P=0.012). Total kidney volume nonsignificantly changed by 4 (-48 to 23) ml with tolvaptan and placebo (P=0.74), whereas it decreased significantly by 41 (25-77) ml with tolvaptan and octreotide-LAR (P=0.001). Changes during the two treatment periods differed by 36 (0-65) ml (P=0.01). Octreotide-LAR also attenuated (P=0.02) the aquaretic effect of tolvaptan. Treatments were well tolerated.

CONCLUSIONS

In patients with ADPKD, octreotide-LAR added-on tolvaptan reduced GFR more effectively than octreotide-LAR and placebo. Octreotide-LAR also reduced total and cystic kidney volumes and attenuated the acquaretic effect of tolvaptan.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

Tolvaptan-Octreotide LAR Combination in ADPKD (TOOL), NCT03541447.

Velocity vector comparison between vector flow imaging and computational fluid dynamics in the carotid bifurcation

It has been largely documented that local hemodynamic conditions, characterized by low and oscillating wall shear stresses, play a key role in the initiation and progression of vascular atherosclerotic lesions. Thus, investigation of the flow field in the carotid bifurcation can lead to early identification of vulnerable plaques. In this scenario, the development of novel non-invasive imaging tools that can be used in routine clinical practice to identify disturbed and recirculating blood flow becomes crucial. In this context, Vector Flow Imaging is becoming a relevant tool as it provides an angle independent assessment of blood flow velocity and multidimensional flow vector visualization. The purpose of the present study was to validate, in several locations of the carotid bifurcation, the high-frame rate vector flow imaging (HiFR-VFI) technique by comparing with computational fluid dynamic simulations (CFD). In all eight carotid bifurcations, HiFR-VFI accurately detected regions of laminar flow as well as recirculation and unsteady flow areas. An accurate and statistically significant agreement was observed between velocity vectors obtained by HiFR-VFI and those computed by CFD, both for vector magnitude (R = 0.85) and direction (R = 0.74). Our study demonstrated that HiFR-VFI is a valid technique for rapid and advanced visual representation of velocity field in large arteries. Thus, it has a great potential in research-based clinical practice for the identification of flow recirculation, low and oscillating velocity gradients near vessel wall. The use of HiFR-VFI may provide a great improvement in the investigation of the role of local hemodynamics in vascular pathologies, as well in the assessment of the effect of pharmacological treatments.

Brain diffusion alterations in patients with COVID-19 pathology and neurological manifestations

BACKGROUND AND OBJECTIVE

COVID-19 neurological manifestations have been progressively recognized. Among available MRI techniques, diffusion weighted imaging (DWI) shows promise to study microstructure, inflammation, and edema. Previous DWI studies reported alterations in brain diffusivity in COVID-19 patients, as assessed by morphologic evaluation of brain DWI scans only. The aim of this study was to assess and quantify brain diffusion alterations in COVID-19 patients with neurological manifestations.

METHODS

215 COVID-19 patients with neurological manifestations (olfactory and/or other neurological disorders) and 36 normal controls were compared and studied with DWI and T1-weighted MRI scans. MRI scans were processed by a semi-automatic processing procedure specifically developed for the purpose of this study, and the Apparent Diffusion Coefficient (ADC) was quantified in different brain tissues and individual white matter (WM) and gray matter (GM) regions. Differences in ADC values were assessed between COVID-19 patients and normal controls, as well as in the COVID-19 patient population grouped by hospitalization and neurological symptoms.

RESULTS

Among COVID-19 patients (median [IQR] = 52 [42 - 60] years of age, 58 % females), 91 were hospitalized and 26 needed intensive care. 84 patients had hyposmia/ageusia only, while 131 ones showed other neurological disorders. COVID-19 patients showed significantly increased ADC values in the WM and in several GM regions (p < 0.001). ADC values were significantly correlated with MRI time from disease onset (p < 0.05). Hospitalized patients showed significantly higher ADC alteration than non-hospitalized patients in all brain tissues; similarly, COVID-19 patients with neurological disorders showed significantly higher ADC values than those with olfactory loss only. ADC alteration was highest in patients with cognitive or memory disorder and in those with encephalitis or meningitis. ADC values were neither associated with the duration of hospitalization nor with the need for intensive care.

CONCLUSION

Current findings suggest DWI potential as a non-invasive marker of neuroinflammation in COVID-19, and the transient nature of the same. Future longitudinal studies are needed to confirm our findings.

MRI evidence of olfactory system alterations in patients with COVID-19 and neurological symptoms

BACKGROUND AND OBJECTIVE

Despite olfactory disorders being among the most common neurological complications of coronavirus disease 2019 (COVID-19), their pathogenesis has not been fully elucidated yet. Brain MR imaging is a consolidated method for evaluating olfactory system's morphological modification, but a few quantitative studies have been published so far. The aim of the study was to provide MRI evidence of olfactory system alterations in patients with COVID-19 and neurological symptoms, including olfactory dysfunction.

METHODS

196 COVID-19 patients (median age: 53 years, 56% females) and 39 controls (median age 55 years, 49% females) were included in this cross-sectional observational study; 78 of the patients reported olfactory loss as the only neurological symptom. MRI processing was performed by ad-hoc semi-automatic processing procedures. Olfactory bulb (OB) volume was measured on T2-weighted MRI based on manual tracing and normalized to the brain volume. Olfactory tract (OT) median signal intensity was quantified on fluid attenuated inversion recovery (FLAIR) sequences, after preliminary intensity normalization.

RESULTS

COVID-19 patients showed significantly lower left, right and total OB volumes than controls (p < 0.05). Age-related OB atrophy was found in the control but not in the patient population. No significant difference was found between patients with olfactory disorders and other neurological symptoms. Several outliers with abnormally high OT FLAIR signal intensity were found in the patient group.

CONCLUSIONS

Brain MRI findings demonstrated OB damage in COVID-19 patients with neurological complications. Future longitudinal studies are needed to clarify the transient or permanent nature of OB atrophy in COVID-19 pathology.

Hybrid fibroin/polyurethane small-diameter vascular grafts: from fabrication to in vivo preliminary assessment

To address the need of alternatives to autologous vessels for small-calibre vascular applications (e.g. cardiac surgery), a hybrid semi-degradable material composed of silk fibroin and polyurethane (Silkothane®) was herein used to fabricate very small-calibre grafts (innner diameter = 1.5 mm) via electrospinning. Hybrid grafts were in vitro characterized in terms of morphology and mechanical behaviour, and compared to similar grafts of pure silk fibroin. Similarly, two native vessels from a rodent model (abdominal aorta and vena cava) were harvested and characterized. Preliminary implants were performed on Lewis rats to confirm the suitability of Silkothane® grafts for small-calibre applications, specifically as aortic insertion and femoral shunt. The manufacturing process generated pliable grafts consisting of a randomized fibrous mesh and exhibiting similar geometrical features to rat aortas. Both Silkothane® and pure silk fibroin grafts showed radial compliances in the range from 1.37 ± 0.86 to 1.88 ± 1.01 % 10-2 mmHg-1, lower than that of native vessels. The Silkothane® small-calibre devices were also implanted in rats demonstrating to be adequate for vascular applications; all the treated rats survived the surgery for 3 months after implantation, and 16 rats out of 17 (94%) still showed blood flow inside the graft at sacrifice. The obtained results lay the basis for a deeper investigation of the interaction between the Silktohane® graft and the implant site, which may deal with further analysis on the potentialities in terms of degradability and tissue formation, on longer time-points.

Cerebral Microbleeds Assessment and Quantification in COVID-19 Patients With Neurological Manifestations

It is increasingly acknowledged that Coronavirus Disease 2019 (COVID-19) can have neurological manifestations, and cerebral microbleeds (CMBs) have been observed in this setting. The aim of this study was to characterize CMBs patterns on susceptibility-weighted imaging (SWI) in hospitalized patients with COVID-19 with neurological manifestations. CMBs volume was quantified and correlated with clinical and laboratory parameters. The study included patients who were hospitalized due to COVID-19, exhibited neurological manifestations, and underwent a brain MRI between March and May 2020. Neurological, clinical, and biochemical variables were reported. The MRI was acquired using a 3T scanner, with a standardized protocol including SWI. Patients were divided based on radiological evidence of CMBs or their absence. The CMBs burden was also assessed with a semi-automatic SWI processing procedure specifically developed for the purpose of this study. Odds ratios (OR) for CMBs were calculated using age, sex, clinical, and laboratory data by logistic regression analysis. Of the 1,760 patients with COVID-19 admitted to the ASST Papa Giovanni XXIII Hospital between 1 March and 31 May 2020, 116 exhibited neurological symptoms requiring neuroimaging evaluation. Of these, 63 patients underwent brain MRI and were therefore included in the study. A total of 14 patients had radiological evidence of CMBs (CMBs+ group). CMBs+ patients had a higher prevalence of CSF inflammation (p = 0.020), a higher white blood cell count (p = 0.020), and lower lymphocytes (p = 0.010); the D-dimer (p = 0.026), LDH (p = 0.004), procalcitonin (p = 0.002), and CRP concentration (p < 0.001) were higher than in the CMBs- group. In multivariable logistic regression analysis, CRP (OR = 1.16, p = 0.011) indicated an association with CMBs. Estimated CMBs volume was higher in females than in males and decreased with age (Rho = −0.38; p = 0.18); it was positively associated with CRP (Rho = 0.36; p = 0.22), and negatively associated with lymphocytes (Rho = −0.52; p = 0.07). CMBs are a frequent imaging finding in hospitalized patients with COVID-19 with neurological manifestations and seem to be related to pro-inflammatory status.

Characterization of the Microflow Through 3D Synthetic Niche Microenvironments Hosted in a Millifluidic Bioreactor

Background: Development of new medicines is a lengthy process with high risk of failure since drug efficacy measured in vitro is difficult to confirm in vivo. Intended to add a new tool aiding drug discovery, the MOAB-NICHOID device was developed: a miniaturized optically accessible bioreactor (MOAB) housing the 3D engineered scaffold NICHOID. The aim of our study was to characterize the microflow through the 3D nichoid microenvironment hosted in the MOAB-NICHOID device.

Methods: We used computational fluid dynamics (CFD) simulations to compute the flow field inside a very fine grid resembling the scaffold microenvironment.

Results: The microflow inside the multi-array of nichoid blocks is fed and locally influenced by the mainstream flow developed in the perfusion chamber of the device. Here we have revealed a low velocity, complex flow field with secondary, backward, or local recirculation micro-flows induced by the intricate architecture of the nichoid scaffold.

Conclusion: Knowledge of the microenvironment inside the 3D nichoids allows planning of cell experiments, to regulate the transport of cells towards the scaffold substrate during seeding or the spatial delivery of nutrients and oxygen which affects cell growth and viability.

Basic principles and new advances in kidney imaging

Over the past few years, clinical renal imaging has seen great advances, allowing assessments of kidney structure and morphology, perfusion, function and metabolism, and oxygenation, as well as microstructure and the interstitium. Medical imaging is becoming increasingly important in the evaluation of kidney physiology and pathophysiology, showing promise in management of patients with renal disease, in particular with regard to diagnosis, classification, and prediction of disease development and progression, monitoring response to therapy, detection of drug toxicity, and patient selection for clinical trials. A variety of imaging modalities, ranging from routine to advanced tools, are currently available to probe the kidney both spatially and temporally, particularly ultrasonography, computed tomography, positron emission tomography, renal scintigraphy, and multiparametric magnetic resonance imaging. Given that the range is broad and varied, kidney imaging techniques should be chosen based on the clinical question and the specific underlying pathologic mechanism, taking into account contraindications and possible adverse effects. Integration of various modalities providing complementary information will likely provide the greatest insight into renal pathophysiology. This review aims to highlight major recent advances in key tools that are currently available or potentially relevant for clinical kidney imaging, with a focus on non-oncological applications. The review also outlines the context of use, limitations, and advantages of various techniques, and highlights gaps to be filled with future development and clinical adoption.

Functional Magnetic Resonance Imaging Versus Kidney Biopsy to Assess Response to Therapy in Nephrotic Syndrome: A Case Report

In recent years, kidney functional magnetic resonance imaging (MRI) has seen great advances, with several cross-sectional studies demonstrating correlations between MRI biomarkers and glomerular filtration rate. However, the potential of MRI to monitor response to therapy in kidney disease remains undescribed. In this case report, a man in his 40s with drug-resistant membranous nephropathy was addressed to ofatumumab therapy. He underwent kidney biopsy before and 2 years after treatment and repeat non–contrast-enhanced MRI of the kidney every 6 months. An age- and sex-matched healthy volunteer was included as a normal control. The patient showed a striking positive immunologic response to therapy. Repeat MRI of the kidney documented progressive kidney functional recovery, with a significant widespread increase in kidney diffusivity, assessed using diffusion-weighted imaging, paralleling the increase in glomerular filtration rate and regression of albuminuria. Renal blood flow and ultrafiltration coefficient, assessed using phase-contrast MRI, significantly increased, suggesting an increase in filtration fraction. This case report provides the first clinical evidence in support of MRI of the kidney as a tool to noninvasively monitor pathophysiologic changes occurring in response to treatment. Although kidney biopsy remains critical for diagnosis, functional MRI of the kidney has promise for monitoring disease progression and response to therapy.

A Novel Hybrid Silk Fibroin/Polyurethane Arteriovenous Graft for Hemodialysis: Proof-of-Concept Animal Study in an Ovine Model

To solve the problem of vascular access failure, a novel semi-degradable hybrid vascular graft, manufactured by electrospinning using silk fibroin and polyurethane (Silkothane), has been previously developed and characterized in vitro. This proof-of-concept animal study aims at evaluating the performances of Silkothane grafts in a sheep model of arteriovenous shunt, in terms of patency and short-term remodeling. Nine Silkothane grafts are implanted between the common carotid artery and the external jugular vein of nine sheep, examined by palpation three times per week, by echo-color Doppler every two weeks, and euthanized at 30, 60, and 90 days (N = 3 per group). At sacrifice, grafts are harvested and submitted for histopathology and/or scanning electron microcopy (SEM). No cases of graft-related complications are recorded. Eight of nine sheep (89%) show 100% primary unassisted patency at the respective time of sacrifice (flow rate 1.76 ± 0.61 L min^-1 , one case of surgery-related thrombosis excluded). Histopathology and SEM analysis evidence signs of inflammation and pseudointima inside the graft lumen, especially at the venous anastomosis; however, endoluminal stenosis never impairs the functionality of the shunt and coverage by endothelial cells is observed. In this model, Silkothane grafts grant safety and 100% patency up to 90 days.

Role of ultrastructural determinants of glomerular permeability in ultrafiltration function loss

The epithelial filtration slit is a crucial component of the glomerular capillary membrane, which is essential for maintaining glomerular filtration function. Though chronic kidney diseases are an immense clinical problem, the mechanisms through which structural alterations reduce glomerular water filtration have not yet been understood completely. To investigate the mechanisms underlying filtration function loss, we studied rats with spontaneously occurring progressive kidney disease, either treated with angiotensin II antagonist or untreated, combining high-resolution electron microscopy of the glomerular capillary wall with theoretical water filtration modeling. Under pathological conditions, epithelial filtration pores and the extension of the subpodocyte space were larger than in normal controls. Numerical analyses indicated that these ultrastructural changes increased hydraulic resistance of the glomerular capillary wall by extending coverage of the filtration barrier by the subpodocyte space, with the changes in hydrodynamic forces acting on podocytes likely being responsible for their detachment. Angiotensin II inhibition normalized the subpodocyte space's hydraulic resistance, restored mechanical podocyte load, and preserved CD151-α3 integrin complex assembly, improving podocyte adherence and survival. Our results show that ultrastructural changes in podocytes are major determinants of the hydraulic resistance of the glomerular capillary wall and highlight the mechanism of podocyte loss in kidney disease progression, as well as the mechanisms underlying angiotensin II inhibition.

Copper-dependent biological effects of particulate matter produced by brake systems on lung alveolar cells

Road traffic is one of the main sources of particulate emissions into the environment and has an increasing, negative impact on the release of potentially dangerous materials. Vehicle brakes release a significant amount of wear particles, and knowledge regarding their possible adverse effects is limited. One of the most dangerous elements contained in brake pads is copper (Cu), known to be toxic for human health. Therefore, our aim was to study the cell toxicity of particulate matter (PM) produced by different combinations of braking discs and pads containing different amounts of Cu. We investigated whether brake-derived microparticles have toxic effects on lung cells proportionally to their Cu content. Analyte content was measured in friction materials by XRFS and in PM2.5 captured during braking tests using SEM/EDX. The biological impact of brake-derived PM2.5 was investigated on a human epithelial alveolar cell line (A549). Cell viability, oxidative stress, mitochondrial membrane potential, apoptosis, and the pro-inflammatory response of the cells, as well as gene expression, were assessed following exposure to increasing PM2.5 concentrations (1, 10, 100, 200, and 500 µg/ml). The brake debris with the lowest Cu content did not induce significant changes in biological effects on A549 cells compared to normal controls, except for ROS production and IL6 gene expression. PM2.5 containing higher Cu quantities induced cell toxicity that correlated with Cu concentration. Our data suggest that the toxicity of PM2.5 from the brake system is mainly related to Cu content, thus confirming that eliminating Cu from brake pads will be beneficial for human health in urbanized environments.

Correction to: Phase-contrast magnetic resonance imaging to assess renal perfusion: a systematic review and statement paper

The article Phase‑contrast magnetic resonance imaging to assess renal perfusion: a systematic review and statement paper, written by Giulia Villa, Steffen Ringgaard, Ingo Hermann, Rebecca Noble, Paolo Brambilla, Dinah S. Khatir, Frank G. Zöllner, Susan T. Francis, Nicholas M. Selby, Andrea Remuzzi and Anna Caroli, was originally published electronically on the publisher's internet portal on 17 August 2019 without open access.

Arteriovenous access in hemodialysis: A multidisciplinary perspective for future solutions

In hemodialysis, vascular access is a key issue. The preferred access is an arteriovenous fistula on the non-dominant lower arm. If the natural vessels are insufficient for such access, the insertion of a synthetic vascular graft between artery and vein is an option to construct an arteriovenous shunt for punctures. In emergency situations and especially in elderly with narrow and atherosclerotic vessels, a cuffed double-lumen catheter is placed in a larger vein for chronic use. The latter option constitutes a greater risk for infections while arteriovenous fistula and arteriovenous shunt can fail due to stenosis, thrombosis, or infections. This review will recapitulate the vast and interdisciplinary scenario that characterizes hemodialysis vascular access creation and function, since adequate access management must be based on knowledge of the state of the art and on future perspectives. We also discuss recent developments to improve arteriovenous fistula creation and patency, the blood compatibility of arteriovenous shunt, needs to avoid infections, and potential development of tissue engineering applications in hemodialysis vascular access. The ultimate goal is to spread more knowledge in a critical area of medicine that is importantly affecting medical costs of renal replacement therapies and patients’ quality of life.

COVID-19 and Italy: what next?

The spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has already taken on pandemic proportions, affecting over 100 countries in a matter of weeks. A global response to prepare health systems worldwide is imperative. Although containment measures in China have reduced new cases by more than 90%, this reduction is not the case elsewhere, and Italy has been particularly affected. There is now grave concern regarding the Italian national health system's capacity to effectively respond to the needs of patients who are infected and require intensive care for SARS-CoV-2 pneumonia. The percentage of patients in intensive care reported daily in Italy between March 1 and March 11, 2020, has consistently been between 9% and 11% of patients who are actively infected. The number of patients infected since Feb 21 in Italy closely follows an exponential trend. If this trend continues for 1 more week, there will be 30 000 infected patients. Intensive care units will then be at maximum capacity; up to 4000 hospital beds will be needed by mid-April, 2020. Our analysis might help political leaders and health authorities to allocate enough resources, including personnel, beds, and intensive care facilities, to manage the situation in the next few days and weeks. If the Italian outbreak follows a similar trend as in Hubei province, China, the number of newly infected patients could start to decrease within 3-4 days, departing from the exponential trend. However, this cannot currently be predicted because of differences between social distancing measures and the capacity to quickly build dedicated facilities in China.

Protective Effect of Human Mesenchymal Stem Cells on the Survival of Pancreatic Islets

Background and Objectives

Transplantation of pancreatic islets is an intriguing new therapeutic option to face the worldwide spread problem of Type-I diabetes. Currently, its clinical use is limited by several problems, mainly based on the high number of islets required to restore normoglycaemia and by the low survival of the transplanted tissue. A promising attempt to overcome the limits to such an approach was represented by the use of Mesenchymal Stem Cells (MSC). Despite the encouraging results obtained with murine-derived MSC, little is still known about their protective mechanisms. The aim of the present study was to verify the effectiveness, (besides murine MSC), of clinically relevant human-derived MSC (hMSC) on protecting pancreatic islets, thus also shedding light on the putative differences between MSC of different origin.

Methods and Results

Threefold kinds of co-cultures were therefore in vitro set up (direct, indirect and mixed), to analyze the hMSC effect on pancreatic islet survival and function and to study the putative mechanisms involved. Although in a different way with respect to murine MSC, also human derived cells demonstrated to be effective on protecting pancreatic islet survival. This effect could be due to the release of some trophic factors, such as VEGF and Il-6, and by the reduction of inflammatory cytokine TNF-α.

Conclusions

Therefore, hMSC confirmed their great clinical potential to improve the feasibility of pancreatic islet transplantation therapy against diabetes.

Engineering the vasculature of decellularized rat kidney scaffolds using human induced pluripotent stem cell-derived endothelial cells

Generating new kidneys using tissue engineering technologies is an innovative strategy for overcoming the shortage of donor organs for transplantation. Here we report how to efficiently engineer the kidney vasculature of decellularized rat kidney scaffolds by using human induced pluripotent stem cell (hiPSCs)-derived endothelial cells (hiPSC-ECs). In vitro, hiPSC-ECs responded to flow stress by acquiring an alignment orientation, and attached to and proliferated on the acellular kidney sections, maintaining their phenotype. The hiPSC-ECs were able to self-organize into chimeric kidney organoids to form vessel-like structures. Ex vivo infusion of hiPSC-ECs through the renal artery and vein of acellular kidneys resulted in the uniform distribution of the cells in all the vasculature compartments, from glomerular capillaries to peritubular capillaries and small vessels. Ultrastructural analysis of repopulated scaffolds through transmission and scanning electron microscopy demonstrated the presence of continuously distributed cells along the vessel wall, which was also confirmed by 3D reconstruction of z-stack images showing the continuity of endothelial cell coverage inside the vessels. Notably, the detection of fenestrae in the endothelium of glomerular capillaries but not in the vascular capillaries was clear evidence of site-specific endothelial cell specialisation.

Toxicological evaluation of airborne particulate matter. Are cell culture technologies ready to replace animal testing?

Exposure to atmospheric particulate matter (PM) can affect human health, causing asthma, atherosclerosis, renal disease and cancer. In the last few years, outdoor air pollution has increased globally, leading to a public health emergency. Epidemiological studies have reported a correlation between the development of severe respiratory and systemic diseases and exposure to PM. To evaluate the toxic effect of PM of different origins, conventional experimental toxicological investigations have been conducted in animals; however, animal experimentation poses major ethical issues and usually differs from human conditions. As an alternative, human cell cultures are increasingly being used to investigate cellular and molecular mechanisms of PM toxicity. Although 2D cell cultures have been proven helpful, they are far from being a valid alternative to animal tests. Recently, 3D cell culture and organ-on-chip technology have provided systems that are more complex and that can be more informative for toxicity studies. In this review, the results of the 2D systems that are most frequently used for PM toxicity evaluations are summarized with a special focus on their limitations. We also examined to which extent 3D cell culture and particularly the organ-on-chip technology may overcome these limitations and represent effective tools to improve airborne PM toxicity evaluations.

Octreotide-LAR in later-stage autosomal dominant polycystic kidney disease (ALADIN 2): A randomized, double-blind, placebo-controlled, multicenter trial

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent genetically determined renal disease. In affected patients, renal function may progressively decline up to end-stage renal disease (ESRD), and approximately 10% of those with ESRD are affected by ADPKD. The somatostatin analog octreotide long-acting release (octreotide-LAR) slows renal function deterioration in patients in early stages of the disease. We evaluated the renoprotective effect of octreotide-LAR in ADPKD patients at high risk of ESRD because of later-stage ADPKD.

METHODS AND FINDINGS

We did an internally funded, parallel-group, double-blind, placebo-controlled phase III trial to assess octreotide-LAR in adults with ADPKD with glomerular filtration rate (GFR) 15-40 ml/min/1.73 m2. Participants were randomized to receive 2 intramuscular injections of 20 mg octreotide-LAR (n = 51) or 0.9% sodium chloride solution (placebo; n = 49) every 28 days for 3 years. Central randomization was 1:1 using a computerized list stratified by center and presence or absence of diabetes or proteinuria. Co-primary short- and long-term outcomes were 1-year total kidney volume (TKV) (computed tomography scan) growth and 3-year GFR (iohexol plasma clearance) decline. Analyses were by modified intention-to-treat. Patients were recruited from 4 Italian nephrology units between October 11, 2011, and March 20, 2014, and followed up to April 14, 2017. Baseline characteristics were similar between groups. Compared to placebo, octreotide-LAR reduced median (95% CI) TKV growth from baseline by 96.8 (10.8 to 182.7) ml at 1 year (p = 0.027) and 422.6 (150.3 to 695.0) ml at 3 years (p = 0.002). Reduction in the median (95% CI) rate of GFR decline (0.56 [-0.63 to 1.75] ml/min/1.73 m2 per year) was not significant (p = 0.295). TKV analyses were adjusted for age, sex, and baseline TKV. Over a median (IQR) 36 (24 to 37) months of follow-up, 9 patients on octreotide-LAR and 21 patients on placebo progressed to a doubling of serum creatinine or ESRD (composite endpoint) (hazard ratio [HR] [95% CI] adjusted for age, sex, baseline serum creatinine, and baseline TKV: 0.307 [0.127 to 0.742], p = 0.009). One composite endpoint was prevented for every 4 treated patients. Among 63 patients with chronic kidney disease (CKD) stage 4, 3 on octreotide-LAR and 8 on placebo progressed to ESRD (adjusted HR [95% CI]: 0.121 [0.017 to 0.866], p = 0.036). Three patients on placebo had a serious renal cyst rupture/infection and 1 patient had a serious urinary tract infection/obstruction, versus 1 patient on octreotide-LAR with a serious renal cyst infection. The main study limitation was the small sample size.

CONCLUSIONS

In this study we observed that in later-stage ADPKD, octreotide-LAR slowed kidney growth and delayed progression to ESRD, in particular in CKD stage 4.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01377246; EudraCT: 2011-000138-12.

A novel hybrid silk-fibroin/polyurethane three-layered vascular graft: towards in situ tissue-engineered vascular accesses for haemodialysis

Clinically available alternatives of vascular access for long-term haemodialysis-currently limited to native arteriovenous fistulae and synthetic grafts-suffer from several drawbacks and are associated to high failure rates. Bioprosthetic grafts and tissue-engineered blood vessels are costly alternatives without clearly demonstrated increased performance. In situ tissue engineering could be the ideal approach to provide a vascular access that profits from the advantages of vascular grafts in the short-term (e.g. early cannulation) and of fistulae in the long-term (e.g. high success rates driven by biointegration). Hence, in this study a three-layered silk fibroin/polyurethane vascular graft was developed by electrospinning to be applied as long-term haemodialysis vascular access pursuing a 'hybrid' in situ engineering approach (i.e. based on a semi-degradable scaffold). This Silkothane^® graft was characterized concerning morphology, mechanics, physical properties, blood contact and vascular cell adhesion/viability. The full three-layered graft structure, influenced by the polyurethane presence, ensured mechanical properties that are a determinant factor for the success of a vascular access (e.g. vein-graft compliance matching). The Silkothane^® graft demonstrated early cannulation potential in line with self-sealing commercial synthetic arteriovenous grafts, and a degradability driven by enzymatic activity. Moreover, the fibroin-only layers and extracellular matrix-like morphology, presented by the graft, revealed to be crucial in providing a non-haemolytic character, long clotting time, and favourable adhesion of human umbilical vein endothelial cells with increasing viability after 3 and 7 d. Accordingly, the proposed approach may represent a step forward towards an in situ engineered hybrid vascular access with potentialities for vein-graft anastomosis stability, early cannulation, and biointegration.

Bioengineering Organs for Blood Detoxification

For patients with severe kidney or liver failure the best solution is currently organ transplantation. However, not all patients are eligible for transplantation and due to limited organ availability, most patients are currently treated with therapies using artificial kidney and artificial liver devices. These therapies, despite their relative success in preserving the patients' life, have important limitations since they can only replace part of the natural kidney or liver functions. As blood detoxification (and other functions) in these highly perfused organs is achieved by specialized cells, it seems relevant to review the approaches leading to bioengineered organs fulfilling most of the native organ functions. There, the culture of cells of specific phenotypes on adapted scaffolds that can be perfused takes place. In this review paper, first the functions of kidney and liver organs are briefly described. Then artificial kidney/liver devices, bioartificial kidney devices, and bioartificial liver devices are focused on, as well as biohybrid constructs obtained by decellularization and recellularization of animal organs. For all organs, a thorough overview of the literature is given and the perspectives for their application in the clinic are discussed.

Platelet Adhesion to Subendothelium - Effect of Shear Rate, Hematocrit and Platelet Count on the Dynamic Equilibrium Between Platelets Adhering to and Detaching from the Surface

The adherence of human 3H-adenine-labeled platelets to rat subendothelium was quantitated using a rotating probe device. Platelet adhesion increased in relation to the rotation time, reaching a plateau value in about 4-6 min without any further increase. A non-linear fitting analysis of experimental data allowed calculations of initial rate and plateau value of platelet adhesion. Increasing the shear rates (from 35 to 150 sec-1) or the hematocrit (from 10% to 40%), both the adhesion rate and the plateau value were increased. When different platelet concentrations were used the adhesion rate and the plateau calculated increased with platelet concentration. Different plateau values were obtained in the experimental conditions considered. This suggests that the plateau was not reached for the complete occupation of the subendothelial surface by the adherent platelets. Experiments using two different vessels rotated in the same platelet suspension or, viceversa, the same vessel rotated successively in two fresh platelet suspensions, showed that the plateau was not determined by reduced platelet reactivity. Rotating the same vessel first in radiolabeled platelets, until the plateau was reached, and secondly in non labeled platelets, or viceversa, showed that the plateau was indeed a dynamic condition where the number of platelets adhering and detaching reached equilibrium. These observations suggest that the platelet adhesion to subendothelium is the final equilibrium of two platelet fluxes, one adhering to the surface and another detaching from the surface.

Toward longitudinal studies of hemodynamically induced vessel wall remodeling

INTRODUCTION:

Autogenous arteriovenous fistula is the preferred vascular access for hemodialysis, but it has high rates of non-maturation and early failure due to vascular stenosis. Convincing evidence supports a key role of local hemodynamics in vascular remodeling, suggesting that unsteady and disturbed flow conditions may be related to stenosis formation in arteriovenous fistula. The purpose of our study was to explore the feasibility of coupling contrast-free magnetic resonance imaging and computational fluid dynamics in longitudinal studies to identify the role of local hemodynamic changes over time in inducing vessel wall remodeling in arteriovenous fistula.

METHODS:

We acquired contrast-free magnetic resonance imaging of arm vasculature at 1 week and 6 weeks after arteriovenous fistula creation in a 72-year-old patient. We then generated three-dimensional models and evaluated lumen cross-sectional area of arteriovenous fistula limbs. We performed high-resolution computational fluid dynamics to evaluate changes in local hemodynamics over time.

RESULTS:

Our contrast-free magnetic resonance imaging protocol provided good quality images in a short scan duration. We observed a homogeneous dilatation in the proximal artery, while there was a more pronounced lumen dilatation in the venous outflow as compared to a limited dilatation in the juxta-anastomotic vein. Furthermore, we observed a slight stabilization of the flow pattern over time, suggesting that vascular outward remodeling accommodates the flow to a more helicoidally phenotype.

CONCLUSION:

Coupling contrast-free magnetic resonance imaging and high-resolution computational fluid dynamics represents a promising approach to shed more light in the mechanisms of vascular remodeling and can be used for prospective clinical investigations aimed at identifying critical hemodynamic factors contributing to arteriovenous fistula failure.

Recombinant Versus High-sensitivity Conventional Thromboplastin: A Randomized Clinical Study in Patients on Oral Anticoagulation

A prospective, randomized, double-blind clinical trial was carried out in a single center to compare the clinical and laboratory quality of oral anticoagulant therapy monitored with recombinant tissue factor (RTF) or with a sensitive, human-derived, conventional thromboplastin (CT) in the PT test. Seven hundred and fifty-seven consecutive patients receiving oral anticoagulation for various indications were randomized to RTF (n = 379) or CT (n = 368) for 6 months. Total follow-up was 167 and 153 patient-years for RTF and TP groups respectively. Fifty-six bleeding events were observed: 31 in the RTF group and 25 in the TP group. The incidence of bleeding was 18.5 and 16.5% pt-yrs for RTF and TP patients respectively (n.s.). The event-free follow-up curves were not significantly different between the two groups. The laboratory quality of oral anticoagulation was evaluated with the “last check in file” method: therapeutic INR was found in the same propor-tipn of RTF and TP patients (70.2% vs 68.8%). Our study shows that RTF is as effective as a sensitive, conventional thromboplastin for monitoring oral anticoagulation.

Thrombotic and Hemorrhagic Complications in Patients with Mechanical Heart Valve Prosthesis Attending an Anticoagulation Clinic

This study evaluated the advantage of an anticoagulation clinic in terms of the improvement of the clinical quality of oral anticoagulation (i.e. prevention of thromboembolism and low rate of hemorrhagic complications). The incidence of thromboembolic events and major hemorrhagic complications was assessed in a series of 271 patients on oral anticoagulation for mechanical heart valve prosthesis before and after their enrollment in our anticoagulation clinic from January 1987 to December 1990. Risk factors for hemostatic events were also analyzed. The incidence of major hemostatic complications was significantly lower when patients attended the clinic: 1.0 vs 4.9%/pt-yr for hemorrhage and 0.6 vs 6.6%/pt-yr for thrombosis. This depended on three main factors: better dose regulation of warfarin, continuous patient education and early identification of clinical conditions potentially at risk for thrombosis and hemorrhage. Only previous hemorrhagic or thromboembolic events were recognized as major risk factors for hemostatic complications.

In conclusion, our study shows that an anticoagulation clinic offers a real advantage to patients with mechanical heart valve prosthesis in terms of prevention of thromboembolic events and hemorrhagic complications.

Albumin Treatment Reduces in Vitro Platelet Deposition to Pmma Dialysis Membrane

We investigated in an in vitro system the effect of albumin on the interaction between circulating platelets and artificial membranes used for hemodialysers. Using a recently described method we evaluated platelet adhesion to polymethylmethacrylate (PMMA) and cuprophan (CU) hollow-fibers. Deposition of washed radiolabelled platelets on these two membranes was measured in small dialysis filters with or without previous perfusion with an albumin solution. Also measured was the amount of albumin that adhered to the membranes after perfusion of the filters with radiolabelled albumin. Platelet deposition to PMMA was significantly reduced by albumin treatment (from 1070 ± 498 to 296 ± 174 plt/mm2, P < 0.01). Platelet deposition on the CU membrane was comparable with and without albumin pre-perfusion (141 ± 70 vs. 152 ± 100 plt/mm2). Deposition of radiolabelled albumin was higher on PMMA than on CU membrane. Thus, higher adborption of this protein, observed in our in vitro system, might explain the lower platelet deposition found on the PMMA rather than on the CU membrane. These results suggest that platelet interactions with PMMA during dialysis could be improved by treating the dialyser with albumin before blood contact. However, before this treatment is used clinically further experimental studies are required to confirm that our in vitro observation also applies to in vivo conditions.

Blood Flow in Idealized Vascular Access for Hemodialysis: A Review of Computational Studies

Although our understanding of the failure mechanism of vascular access for hemodialysis has increased substantially, this knowledge has not translated into successful therapies. Despite advances in technology, it is recognized that vascular access is difficult to maintain, due to complications such as intimal hyperplasia. Computational studies have been used to estimate hemodynamic changes induced by vascular access creation. Due to the heterogeneity of patient-specific geometries, and difficulties with obtaining reliable models of access vessels, idealized models were often employed. In this review we analyze the knowledge gained with the use of computational such simplified models. A review of the literature was conducted, considering studies employing a computational fluid dynamics approach to gain insights into the flow field phenotype that develops in idealized models of vascular access. Several important discoveries have originated from idealized model studies, including the detrimental role of disturbed flow and turbulent flow, and the beneficial role of spiral flow in intimal hyperplasia. The general flow phenotype was consistent among studies, but findings were not treated homogeneously since they paralleled achievements in cardiovascular biomechanics which spanned over the last two decades. Computational studies in idealized models are important for studying local blood flow features and evaluating new concepts that may improve the patency of vascular access for hemodialysis. For future studies we strongly recommend numerical modelling targeted at accurately characterizing turbulent flows and multidirectional wall shear disturbances.

Kidney volume measurement methods for clinical studies on autosomal dominant polycystic kidney disease

Background

In autosomal dominant polycystic kidney disease (ADPKD), total kidney volume (TKV) is regarded as an important biomarker of disease progression and different methods are available to assess kidney volume. The purpose of this study was to identify the most efficient kidney volume computation method to be used in clinical studies evaluating the effectiveness of treatments on ADPKD progression.

Methods and findings

We measured single kidney volume (SKV) on two series of MR and CT images from clinical studies on ADPKD (experimental dataset) by two independent operators (expert and beginner), twice, using all of the available methods: polyline manual tracing (reference method), free-hand manual tracing, semi-automatic tracing, Stereology, Mid-slice and Ellipsoid method. Additionally, the expert operator also measured the kidney length. We compared different methods for reproducibility, accuracy, precision, and time required. In addition, we performed a validation study to evaluate the sensitivity of these methods to detect the between-treatment group difference in TKV change over one year, using MR images from a previous clinical study. Reproducibility was higher on CT than MR for all methods, being highest for manual and semiautomatic contouring methods (planimetry). On MR, planimetry showed highest accuracy and precision, while on CT accuracy and precision of both planimetry and Stereology methods were comparable. Mid-slice and Ellipsoid method, as well as kidney length were fast but provided only a rough estimate of kidney volume. The results of the validation study indicated that planimetry and Stereology allow using an importantly lower number of patients to detect changes in kidney volume induced by drug treatment as compared to other methods.

Conclusions

Planimetry should be preferred over fast and simplified methods for accurately monitoring ADPKD progression and assessing drug treatment effects. Expert operators, especially on MR images, are required for performing reliable estimation of kidney volume. The use of efficient TKV quantification methods considerably reduces the number of patients to enrol in clinical investigations, making them more feasible and significant.

Automatic Segmentation of Kidneys using Deep Learning for Total Kidney Volume Quantification in Autosomal Dominant Polycystic Kidney Disease

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common inherited disorder of the kidneys. It is characterized by enlargement of the kidneys caused by progressive development of renal cysts, and thus assessment of total kidney volume (TKV) is crucial for studying disease progression in ADPKD. However, automatic segmentation of polycystic kidneys is a challenging task due to severe alteration in the morphology caused by non-uniform cyst formation and presence of adjacent liver cysts. In this study, an automated segmentation method based on deep learning has been proposed for TKV computation on computed tomography (CT) dataset of ADPKD patients exhibiting mild to moderate or severe renal insufficiency. The proposed method has been trained (n = 165) and tested (n = 79) on a wide range of TKV (321.2-14,670.7 mL) achieving an overall mean Dice Similarity Coefficient of 0.86 ± 0.07 (mean ± SD) between automated and manual segmentations from clinical experts and a mean correlation coefficient (ρ) of 0.98 (p < 0.001) for segmented kidney volume measurements in the entire test set. Our method facilitates fast and reproducible measurements of kidney volumes in agreement with manual segmentations from clinical experts.

Clinical use of computational modeling for surgical planning of arteriovenous fistula for hemodialysis

BACKGROUND

Autogenous arteriovenous fistula (AVF) is the best vascular access (VA) for hemodialysis, but its creation is still a critical procedure. Physical examination, vascular mapping and doppler ultrasound (DUS) evaluation are recommended for AVF planning, but they can not provide direct indication on AVF outcome. We recently developed and validated in a clinical trial a patient-specific computational model to predict pre-operatively the blood flow volume (BFV) in AVF for different surgical configuration on the basis of demographic, clinical and DUS data. In the present investigation we tested power of prediction and usability of the computational model in routine clinical setting.

METHODS

We developed a web-based system (AVF.SIM) that integrates the computational model in a single procedure, including data collection and transfer, simulation management and data storage. A usability test on observational data was designed to compare predicted vs. measured BFV and evaluate the acceptance of the system in the clinical setting. Six Italian nephrology units were involved in the evaluation for a 6-month period that included all incident dialysis patients with indication for AVF surgery.

RESULTS

Out of the 74 patients, complete data from 60 patients were included in the final dataset. Predicted brachial BFV at 40 days after surgery showed a good correlation with measured values (in average 787 ± 306 vs. 751 ± 267 mL/min, R = 0.81, p < 0.001). For distal AVFs the mean difference (±SD) between predicted vs. measured BFV was -2.0 ± 20.9%, with 50% of predicted values in the range of 86-121% of measured BFV. Feedbacks provided by clinicians indicate that AVF.SIM is easy to use and well accepted in clinical routine, with limited additional workload.

CONCLUSIONS

Clinical use of computational modeling for AVF surgical planning can help the surgeon to select the best surgical strategy, reducing AVF early failures and complications. This approach allows individualization of VA care, with the aim to reduce the costs associated with VA dysfunction, and to improve AVF clinical outcome.

Experimental Evaluation of Kidney Regeneration by Organ Scaffold Recellularization

The rising number of patients needing renal replacement therapy, alongside the significant clinical and economic limitations of current therapies, creates an imperative need for new strategies to treat kidney diseases. Kidney bioengineering through the production of acellular scaffolds and recellularization with stem cells is one potential strategy. While protocols for obtaining organ scaffolds have been developed successfully, scaffold recellularization is more challenging. We evaluated the potential of in vivo and in vitro kidney scaffold recellularization procedures. Our results show that acellular scaffolds implanted in rats cannot be repopulated with host cells, and in vitro recellularization is necessary. However, we obtained very limited and inconsistent cell seeding when using different infusion protocols, regardless of injection site. We also obtained experimental and theoretical data indicating that uniform cell delivery into the kidney scaffolds cannot be obtained using these infusion protocols, due to the permeability of the extracellular matrix of the scaffold. Our results highlight the major physical barriers that limit in vitro recellularization of acellular kidney scaffolds and the obstacles that must be investigated to effectively advance this strategy for regenerative medicine.