A Retrograde Implantation Approach for Peritoneal Dialysis Catheter Placement in Mice.

Murine models are employed to probe various aspects of peritoneal dialysis (PD), such as peritoneal inflammation and fibrosis. These events drive peritoneal membrane failure in humans, which remains an area of intense investigation due to its profound clinical implications in managing patients with end-stage kidney disease (ESKD). Despite the clinical importance of PD and its related complications, current experimental murine models suffer from key technical challenges that compromise the models' performance. These include PD catheter migration and kinking and usually warrant earlier catheter removal. These limitations also drive the need for a greater number of animals to complete a study. Addressing these drawbacks, this study introduces technical improvements and surgical nuances to prevent commonly observed PD catheter complications in a murine model. Moreover, this modified model is validated by inducing peritoneal inflammation and fibrosis using lipopolysaccharide injections. In essence, this paper describes an improved method to create an experimental model of PD.

Progress in hepatitis C virus management in chronic kidney disease.

PURPOSE OF REVIEW: The current review highlights advances in the use of direct-acting antiviral (DAA) agents in the treatment of hepatitis C virus (HCV) in chronic kidney disease (CKD) stages G4-5, end-stage renal disease, and kidney transplantation. The use of DAA to facilitate kidney transplantation of HCV negative recipients with kidneys from HCV-infected donors and in the management of HCV-related cryoglobulinemia are also reviewed. RECENT FINDINGS: DAA treatment results in rates of viral clearance (sustained virological response or SVR) of 90-100% in all studied CKD populations, comparable to SVR rates in the general population. DAA treatment allows safe and effective transplantation of HCV viremic kidneys into uninfected recipients. SUMMARY: The high SVR results achieved with DAA allow successful treatment of previously under-treated CKD populations, and encouraged innovative interventions such as the use of HCV-infected donor kidneys to uninfected kidney transplant recipients.

A conceptual framework linking immunology, pathology, and clinical features in primary membranous nephropathy.

Primary membranous nephropathy is a leading cause of adult nephrotic syndrome. The field took a major step forward with the identification of phospholipase A2 receptor (PLA2R) as a target antigen in the majority of cases and with the ability to measure circulating autoantibodies to PLA2R. Since then, the existence of additional target antigens such as thrombospondin type-1 domain-containing 7A, exostosin 1 and 2, neural EGFL like 1, and semaphorin 3B has been demonstrated. The ability to detect and monitor levels of circulating autoantibodies has opened a new window onto the humoral aspect of primary membranous nephropathy. Clinicians now rely on clinical parameters such as proteinuria, as well as levels of circulating autoantibodies against PLA2R and the results of immunofluorescence staining for PLA2R within kidney biopsy tissue, to guide the management of this disease. The relationship between immunologic and clinical disease course is consistent, but not necessarily intuitive. In addition, kidney biopsy provides only a single snapshot of disease that needs to be interpreted in light of changing clinical and serological findings. A clear understanding of these dynamic parameters is essential for staging, treatment, and management of this disease. This review aims to shed light on current knowledge regarding the development and time course of changes in the serum levels of autoantibodies against PLA2R, proteinuria, and histological findings that underlie the pathophysiology of primary membranous nephropathy.

Association of Medicaid Expansion with Tunneled Dialysis Catheter Use at the Time of First Arteriovenous Access Creation.

BACKGROUND: In the United States, many low-income patients initiating hemodialysis are uninsured before qualifying for Medicare. Inadequate access to predialysis care may delay their arteriovenous (AV) access creation and increase tunneled dialysis catheter (TDC) use. The 2014 Affordable Care Act expanded eligibility for Medicaid among low-income adults, but not every state adopted this measure. We evaluated whether Medicaid expansion was associated with decreased TDC use for hemodialysis initiation. METHODS: We queried the United States Vascular Quality Initiative state-level database for non-Medicare patients undergoing initial AV access creation from 2011 to 2018. We evaluated associations of receiving initial AV access in states that expanded Medicaid with concurrent TDC use, survival, and insurance coverage. RESULTS: Data were available for patients in 31 states: 19 states expanded Medicaid from January 2014 to February 2015. Among 8462 patients in the postexpansion period from March 2015 to December 2018, 58% were in Medicaid expansion states. Patients in Medicaid expansion states less often had concurrent TDCs (40% vs. 48%, P < 0.001). In multivariable analysis, Medicaid expansion was independently associated with fewer TDCs (OR 0.7, 95% CI 0.6-0.8, P < 0.001). Three-year survival was similar between patients in Medicaid expansion and nonexpansion states (84.7% vs. 85.2%, P = 0.053). Multivariable cox-regression confirmed the finding (HR 0.95, 95% CI 0.82-1.1, P = 0.482). In difference-in-differences analysis, Medicaid expansion was associated with a 9.2-percentage point increase in Medicaid coverage (95% CI 2.7-15.8, P = 0.009). Hispanic patients exhibited a 30.1-percentage point increase in any insurance coverage (95% CI 0.3-59.9, P = 0.048). CONCLUSIONS: Patients in Medicaid expansion states were less likely to have TDCs during initial AV access creation, suggesting earlier predialysis care. Hispanic patients benefited from increased insurance coverage. Expanding insurance options for the underserved may improve quality metrics and cost-savings for hemodialysis patients.

Advances in BK Virus Complications in Organ Transplantation and Beyond.

Reactivation of BK virus (BKV) remains a dreaded complication in immunosuppressed states. Conventionally, BKV is known as a cause for BKV-associated nephropathy and allograft dysfunction in kidney transplant recipients. However, emerging studies have shown its negative impact on native kidney function and patient survival in other transplants and its potential role in diseases such as cancer. Because BKV-associated nephropathy is driven by immunosuppression, reduction in the latter is a convenient standard of care. However, this strategy is risk prone due to the development of donor-specific antibodies affecting long-term allograft survival. Despite its pathogenic role, there is a distinct lack of effective anti-BKV therapeutics. This limitation combined with increased morbidity and health care cost of BKV-associated diseases add to the complexity of BKV management. While summarizing recent advances in the pathogenesis of BKV-associated nephropathy and its reactivation in other organ transplants, this review illustrates the limitations of current and emerging therapeutic options and provides a compelling argument for an effective targeted anti-BKV drug.

Hyperthrombotic Milieu in COVID-19 Patients.

COVID-19 infection has protean systemic manifestations. Experience from previous coronavirus outbreaks, including the current SARS-CoV-2, has shown an augmented risk of thrombosis of both macrovasculature and microvasculature. The former involves both arterial and venous beds manifesting as stroke, acute coronary syndrome and venous thromboembolic events. The microvascular thrombosis is an underappreciated complication of SARS-CoV-2 infection with profound implications on the development of multisystem organ failure. The telltale signs of perpetual on-going coagulation and fibrinolytic cascades underscore the presence of diffuse endothelial damage in the patients with COVID-19. These parameters serve as strong predictors of mortality. While summarizing the alterations of various components of thrombosis in patients with COVID-19, this review points to the emerging evidence that implicates the prominent role of the extrinsic coagulation cascade in COVID-19-related coagulopathy. These mechanisms are triggered by widespread endothelial cell damage (endotheliopathy), the dominant driver of macro- and micro-vascular thrombosis in these patients. We also summarize other mediators of thrombosis, clinically relevant nuances such as the occurrence of thromboembolic events despite thromboprophylaxis (breakthrough thrombosis), current understanding of systemic anticoagulation therapy and its risk-benefit ratio. We conclude by emphasizing a need to probe COVID-19-specific mechanisms of thrombosis to develop better risk markers and safer therapeutic targets.

Metabolites in a mouse cancer model enhance venous thrombogenicity through the aryl hydrocarbon receptor-tissue factor axis.

Patients with malignancy are at 4- to 7-fold higher risk of venous thromboembolism (VTE), a potentially fatal, yet preventable complication. Although general mechanisms of thrombosis are enhanced in these patients, malignancy-specific triggers and their therapeutic implication remain poorly understood. Here we examined a colon cancer-specific VTE model and probed a set of metabolites with prothrombotic propensity in the inferior vena cava (IVC) ligation model. Athymic mice injected with human colon adenocarcinoma cells exhibited significantly higher IVC clot weights, a biological readout of venous thrombogenicity, compared with the control mice. Targeted metabolomics analysis of plasma of mice revealed an increase in the blood levels of kynurenine and indoxyl sulfate (tryptophan metabolites) in xenograft-bearing mice, which correlated positively with the increase in the IVC clot size. These metabolites are ligands of aryl hydrocarbon receptor (AHR) signaling. Accordingly, plasma from the xenograft-bearing mice activated the AHR pathway and augmented tissue factor (TF) and plasminogen activator inhibitor 1 (PAI-1) levels in venous endothelial cells in an AHR-dependent manner. Consistent with these findings, the endothelium from the IVC of xenograft-bearing animals revealed nuclear AHR and upregulated TF and PAI-1 expression, telltale signs of an activated AHR-TF/PAI-1 axis. Importantly, pharmacological inhibition of AHR activity suppressed TF and PAI-1 expression in endothelial cells of the IVC and reduced clot weights in both kynurenine-injected and xenograft-bearing mice. Together, these data show dysregulated tryptophan metabolites in a mouse cancer model, and they reveal a novel link between these metabolites and the control of the AHR-TF/PAI-1 axis and VTE in cancer.

Segmentation of Glomeruli Within Trichrome Images Using Deep Learning.

INTRODUCTION: The number of glomeruli and glomerulosclerosis evaluated on kidney biopsy slides constitute standard components of a renal pathology report. Prevailing methods for glomerular assessment remain manual, labor intensive, and nonstandardized. We developed a deep learning framework to accurately identify and segment glomeruli from digitized images of human kidney biopsies. METHODS: Trichrome-stained images (n = 275) from renal biopsies of 171 patients with chronic kidney disease treated at the Boston Medical Center from 2009 to 2012 were analyzed. A sliding window operation was defined to crop each original image to smaller images. Each cropped image was then evaluated by at least 3 experts into 3 categories: (i) no glomerulus, (ii) normal or partially sclerosed (NPS) glomerulus, and (iii) globally sclerosed (GS) glomerulus. This led to identification of 751 unique images representing nonglomerular regions, 611 images with NPS glomeruli, and 134 images with GS glomeruli. A convolutional neural network (CNN) was trained with cropped images as inputs and corresponding labels as output. Using this model, an image processing routine was developed to scan the test images to segment the GS glomeruli. RESULTS: The CNN model was able to accurately discriminate nonglomerular images from NPS and GS images (performance on test data: Accuracy: 92.67% ± 2.02% and Kappa: 0.8681 ± 0.0392). The segmentation model that was based on the CNN multilabel classifier accurately marked the GS glomeruli on the test data (Matthews correlation coefficient = 0.628). CONCLUSION: This work demonstrates the power of deep learning for assessing complex histologic structures from digitized human kidney biopsies.

Towards minimally-invasive, quantitative assessment of chronic kidney disease using optical spectroscopy.

The universal pathologic features implicated in the progression of chronic kidney disease (CKD) are interstitial fibrosis and tubular atrophy (IFTA). Current methods of estimating IFTA are slow, labor-intensive and fraught with variability and sampling error, and are not quantitative. As such, there is pressing clinical need for a less-invasive and faster method that can quantitatively assess the degree of IFTA. We propose a minimally-invasive optical method to assess the macro-architecture of kidney tissue, as an objective, quantitative assessment of IFTA, as an indicator of the degree of kidney disease. The method of elastic-scattering spectroscopy (ESS) measures backscattered light over the spectral range 320-900 nm and is highly sensitive to micromorphological changes in tissues. Using two discrete mouse models of CKD, we observed spectral trends of increased scattering intensity in the near-UV to short-visible region (350-450 nm), relative to longer wavelengths, for fibrotic kidneys compared to normal kidney, with a quasi-linear correlation between the ESS changes and the histopathology-determined degree of IFTA. These results suggest the potential of ESS as an objective, quantitative and faster assessment of IFTA for the management of CKD patients and in the allocation of organs for kidney transplantation.

Non-immunological complications following kidney transplantation.

Kidney transplantation (KT) is the most effective way to decrease the high morbidity and mortality of patients with end-stage renal disease. However, KT does not completely reverse the damage done by years of decreased kidney function and dialysis. Furthermore, new offending agents (in particular, immunosuppression) added in the post-transplant period increase the risk of complications. Cardiovascular (CV) disease, the leading cause of death in KT recipients, warrants pre-transplant screening based on risk factors. Nevertheless, the screening methods currently used have many shortcomings and a perfect screening modality does not exist. Risk factor modification in the pre- and post-transplant periods is of paramount importance to decrease the rate of CV complications post-transplant, either by lifestyle modification (for example, diet, exercise, and smoking cessation) or by pharmacological means (for example, statins, anti-hyperglycemics, and so on). Post-transplantation diabetes mellitus (PTDM) is a major contributor to mortality in this patient population. Although tacrolimus is a major contributor to PTDM development, changes in immunosuppression are limited by the higher risk of rejection with other agents. Immunosuppression has also been implicated in higher risk of malignancy; therefore, proper cancer screening is needed. Cancer immunotherapy is drastically changing the way certain types of cancer are treated in the general population; however, its use post-transplant is limited by the risk of allograft rejection. As expected, higher risk of infections is also encountered in transplant recipients. When caring for KT recipients, special attention is needed in screening methods, preventive measures, and treatment of infection with BK virus and cytomegalovirus. Hepatitis C virus infection is common in transplant candidates and in the deceased donor pool; however, newly developed direct-acting antivirals have been proven safe and effective in the pre- and post-transplant periods. The most important and recent developments on complications following KT are reviewed in this article.

Unique aspects of peripheral artery disease in patients with chronic kidney disease.

Peripheral artery disease (PAD) represents a major health care burden. Despite the advent of screening and interventional procedures, the long-term clinical outcomes remain suboptimal, especially in patients with chronic kidney disease (CKD). While CKD and PAD share common predisposing factors, emerging studies indicate that their co-existence is not merely an association; instead, CKD represents a strong, independent risk factor for PAD. These findings implicate CKD-specific mediators of PAD that remain incompletely understood. Moreover, there is a need to understand the mechanisms underlying poor outcomes after interventions for PAD in CKD. This review discusses unique clinical aspects of PAD in patients with CKD, including high prevalence and worse outcomes after vascular interventions and the influence of renal allograft transplantation. In doing so, it also highlights underappreciated aspects of PAD in patients with CKD, such as disparities in revascularization and higher peri-procedural mortality. While previous reviews have discussed general mechanisms of PAD pathogenesis, focusing on PAD in CKD, this review underscores a need to probe for CKD-specific pathogenic pathways that may unravel novel biomarkers and therapeutic targets in PAD and ultimately improve the risk stratification and management of patients with CKD and PAD.

Monoclonal IgG4/2κ Deposition Following Eculizumab Therapy for Recurrent Atypical Hemolytic Uremic Syndrome in Kidney Transplantation.

Eculizumab is an emerging therapy for atypical hemolytic uremic syndrome (aHUS). Early identification and treatment of recurrent aHUS after kidney transplantation requires a high clinical suspicion but results in improved graft function and patient outcome. We present a patient who developed recurrent aHUS after kidney transplantation that responded to eculizumab therapy. A kidney biopsy was performed to confirm resolution of thrombotic microangiopathy 8 weeks after eculizumab treatment initiation and revealed no features of thrombotic microangiopathy. Instead, the biopsy revealed monoclonal immunoglobulin G (IgG)4/2κ deposition in the glomerular tufts, vasculature, and atrophic tubular basement membranes. IgG4/2κ deposits are a rare pathologic finding following eculizumab therapy, and the long-term effect of these deposits on kidney function remains unknown.

Summary of the 2018 Kidney Disease Improving Global Outcomes (KDIGO) Guideline on hepatitis C in chronic kidney disease.

KDIGO recently updated its clinical practice guideline for the prevention, diagnosis, evaluation, and treatment of hepatitis C virus (HCV) infection in patients with chronic kidney disease (CKD). The management of HCV in patients with CKD has dramatically shifted over the past 10 years with the development of direct-acting antiviral (DAA) agents and subsequent demonstration of their efficacy in CKD populations. The opportunity to cure HCV with DAA treatment has impacted all aspects of the KDIGO guideline on HCV in CKD including: (a) HCV diagnosis in CKD populations; (b) HCV treatment in CKD populations; (c) preventing HCV transmission in HD units; (d) management of HCV before and after kidney transplantation; and (e) management of HCV-associated glomerular disease. This review summarizes and discusses the major recommendations, along with the implication of the guideline on clinical practice.

Association of Pathological Fibrosis With Renal Survival Using Deep Neural Networks.

INTRODUCTION: Chronic kidney damage is routinely assessed semiquantitatively by scoring the amount of fibrosis and tubular atrophy in a renal biopsy sample. Although image digitization and morphometric techniques can better quantify the extent of histologic damage, we need more widely applicable ways to stratify kidney disease severity. METHODS: We leveraged a deep learning architecture to better associate patient-specific histologic images with clinical phenotypes (training classes) including chronic kidney disease (CKD) stage, serum creatinine, and nephrotic-range proteinuria at the time of biopsy, and 1-, 3-, and 5-year renal survival. Trichrome-stained images processed from renal biopsy samples were collected on 171 patients treated at the Boston Medical Center from 2009 to 2012. Six convolutional neural network (CNN) models were trained using these images as inputs and the training classes as outputs, respectively. For comparison, we also trained separate classifiers using the pathologist-estimated fibrosis score (PEFS) as input and the training classes as outputs, respectively. RESULTS: CNN models outperformed PEFS across the classification tasks. Specifically, the CNN model predicted the CKD stage more accurately than the PEFS model (κ = 0.519 vs. 0.051). For creatinine models, the area under curve (AUC) was 0.912 (CNN) versus 0.840 (PEFS). For proteinuria models, AUC was 0.867 (CNN) versus 0.702 (PEFS). AUC values for the CNN models for 1-, 3-, and 5-year renal survival were 0.878, 0.875, and 0.904, respectively, whereas the AUC values for PEFS model were 0.811, 0.800, and 0.786, respectively. CONCLUSION: The study demonstrates a proof of principle that deep learning can be applied to routine renal biopsy images.

Hepatitis C virus infection in kidney transplantation-changing paradigms with novel agents.

Hepatitis C virus (HCV) is a common cause of increased morbidity and mortality in kidney transplant patients. It is associated with posttransplant glomerulonephritis, chronic allograft nephropathy, and New Onset Diabetes after Transplant (NODAT). In the past, HCV was difficult to treat due to the presence of interferon alpha-based therapies that were difficult to tolerate and were associated with adverse side-effects, such as the risk of rejection. With the advent of oral directly acting antiviral therapies, the landscape for HCV and transplantation has changed. These agents are highly effective and well tolerated with minimal side-effects. Sustained viral response rates in excess of 90% are achieved with most current treatment regimens active against all HCV genotypes. These new agents may show an improvement in graft and patient survival while essentially eliminating the risk of acute rejection from the use of prior interferon-based HCV therapies. These agents may also result in an improvement in organ allocation for HCV donor/HCV recipient transplantation. This review is meant to discuss the epidemiology of HCV, the new oral direct-acting antiviral agents (DAAs) and future opportunities for research in the field of HCV related transplantation.

Timing of hepatitis C virus infection treatment in kidney transplant candidates.

Hepatitis C virus (HCV) infection is prevalent in patients with kidney disease including transplant candidates and recipients. It is associated with increased morbidity and mortality in end-stage renal disease patients and also increases the risk of allograft rejection and decreases allograft and patient survival post-transplant. Newly developed direct acting antivirals have revolutionized the way HCV is treated. Whether patients are treated before or after kidney transplantation, the cure rates with direct acting antivirals are >90%. Great debate has formed revolving the optimal timing to treat kidney transplant candidates. On the one hand, treatment before transplantation decreases early post-transplant complications related to HCV. On the other, postponing treatment until after transplantation opens the possibility of transplanting a kidney from a HCV positive donor, which is associated with shorter waiting time and improved organ utilization by expanding the organ donor pool. Most patients living in an area where waiting time is reduced by accepting an HCV positive kidney would benefit by the strategy of treatment post-transplantation, but this decision needs to be individualized in a patient-by-patient basis given that there are special circumstances (i.e., severe HCV-related extrahepatic manifestations, availability of live donors, etc.) in which treatment before transplant might be preferred.

Uremic Solute-Aryl Hydrocarbon Receptor-Tissue Factor Axis Associates with Thrombosis after Vascular Injury in Humans.

Individuals with CKD are particularly predisposed to thrombosis after vascular injury. Using mouse models, we recently described indoxyl sulfate, a tryptophan metabolite retained in CKD and an activator of tissue factor (TF) through aryl hydrocarbon receptor (AHR) signaling, as an inducer of thrombosis across the CKD spectrum. However, the translation of findings from animal models to humans is often challenging. Here, we investigated the uremic solute-AHR-TF thrombosis axis in two human cohorts, using a targeted metabolomics approach to probe a set of tryptophan products and high-throughput assays to measure AHR and TF activity. Analysis of baseline serum samples was performed from 473 participants with advanced CKD from the Dialysis Access Consortium Clopidogrel Prevention of Early AV Fistula Thrombosis trial. Participants with subsequent arteriovenous thrombosis had significantly higher levels of indoxyl sulfate and kynurenine, another uremic solute, and greater activity of AHR and TF, than those without thrombosis. Pattern recognition analysis using the components of the thrombosis axis facilitated clustering of the thrombotic and nonthrombotic groups. We further validated these findings using 377 baseline samples from participants in the Thrombolysis in Myocardial Infarction II trial, many of whom had CKD stage 2-3. Mechanistic probing revealed that kynurenine enhances thrombosis after vascular injury in an animal model and regulates thrombosis in an AHR-dependent manner. This human validation of the solute-AHR-TF axis supports further studies probing its utility in risk stratification of patients with CKD and exploring its role in other diseases with heightened risk of thrombosis.

Thrombotic Microangiopathy: A Multidisciplinary Team Approach.

Thrombotic microangiopathy (TMA) is characterized by the presence of microangiopathic hemolytic anemia and thrombocytopenia along with organ dysfunction, and pathologically, by the presence of microthrombi in multiple microvascular beds. Delays in diagnosis and initiation of therapy are common due to the low incidence, variable presentation, and poor awareness of these diseases, underscoring the need for interdisciplinary approaches to clinical care for TMA. We describe a new approach to improve clinical management via a TMA team that originally stemmed from an Affinity Research Collaborative team focused on thrombosis and hemostasis. The TMA team consists of clinical faculty from different disciplines who together are charged with the responsibility to quickly analyze clinical presentations, guide laboratory testing, and streamline prompt institution of treatment. The TMA team also includes faculty members from a broad range of disciplines collaborating to elucidate the pathogenesis of TMA. To this end, a clinical database and biorepository have been constructed. TMA leaders educate front-line providers from other departments through presentations in various forums across multiple specialties. Facilitated by an Affinity Research Collaborative mechanism, we describe an interdisciplinary team dedicated to improving both clinical care and translational research in TMA.

Breaking down the complement system: a review and update on novel therapies.

PURPOSE OF REVIEW: The complement system represents one of the more primitive forms of innate immunity. It has increasingly been found to contribute to pathologies in the native and transplanted kidney. We provide a concise review of the physiology of the complement cascade, and discuss current and upcoming complement-based therapies. RECENT FINDINGS: Current agents in clinical use either bind to complement components directly or prevent complement from binding to antibodies affixed to the endothelial surface. These include C1 esterase inhibitors, anti-C5 mAbs, anti-CD20 mAbs, and proteasome inhibitors. Treatment continues to show efficacy in the atypical hemolytic uremic syndrome and antibody-mediated rejection. Promising agents not currently available include CCX168, TP10, AMY-101, factor D inhibitors, coversin, and compstatin. Several new trials are targeting complement inhibition to treat antineutrophilic cystoplasmic antibody (ANCA)-associated vasculitis, C3 glomerulopathy, thrombotic microangiopathy, and IgA nephropathy. New agents for the treatment of the atypical hemolytic uremic syndrome are also in development. SUMMARY: Complement-based therapies are being considered for targeted therapy in the atypical hemolytic uremic syndrome and antibody-mediated rejection, C3 glomerulopathy, and ANCA-associated vasculitis. A few agents are currently in use as orphan drugs. A number of other drugs are in clinical trials and, overall, are showing promising preliminary results.