AIM2 Suppresses Inflammation and Epithelial Cell Proliferation during Glomerulonephritis.

Absent in melanoma-2 (AIM2) is an inflammasome-forming innate immune sensor for dsDNA but also exhibits inflammasome-independent functions such as restricting cellular proliferation. AIM2 is expressed in the kidney, but its localization and function are not fully characterized. In normal human glomeruli, AIM2 localized to podocytes. In patients with glomerulonephritis, AIM2 expression increased in CD44+-activated parietal epithelial cells within glomerular crescents. To explore AIM2 effects in glomerular disease, studies in Aim2 -/- mice were performed. Aim2-/- glomeruli showed reduced expression of Wilm tumor gene-1 (WT1), WT1-driven podocyte genes, and increased proliferation in outgrowth assays. In a nephrotoxic serum (NTS)-induced glomerulonephritis model, Aim2-/- (B6) mice exhibited more severe glomerular crescent formation, tubular injury, inflammation, and proteinuria compared with wild-type controls. Inflammasome activation markers were absent in both Aim2 -/- and wild-type kidneys, despite an increased inflammatory transcriptomic signature in Aim2 -/- mice. Aim2 -/- mice also demonstrated dysregulated cellular proliferation and an increase in CD44+ parietal epithelial cells during glomerulonephritis. The augmented inflammation and epithelial cell proliferation in Aim2 -/- (B6) mice was not due to genetic background, as Aim2 -/- (B6.129) mice demonstrated a similar phenotype during NTS glomerulonephritis. The AIM2-like receptor (ALR) locus was necessary for the inflammatory glomerulonephritis phenotype observed in Aim2 -/- mice, as NTS-treated ALR -/- mice displayed equal levels of injury as wild-type controls. Podocyte outgrowth from ALR -/- glomeruli was still increased, however, confirming that the ALR locus is dispensable for AIM2 effects on epithelial cell proliferation. These results identify a noncanonical role for AIM2 in suppressing inflammation and epithelial cell proliferation during glomerulonephritis.

Methods for Quantifying the Metabolic Boundary Fluxes of Cell Cultures in Large Cohorts by High-Resolution Hydrophilic Liquid Chromatography Mass Spectrometry.

Metabolomics is a mainstream approach for investigating the metabolic underpinnings of complex biological phenomena and is increasingly being applied to large-scale studies involving hundreds or thousands of samples. Although metabolomics methods are robust in smaller-scale studies, they can be challenging to apply to larger cohorts due to the inherent variability of liquid chromatography mass spectrometry (LC-MS). Much of this difficulty results from the time-dependent changes in the LC-MS system, which affects both the qualitative and quantitative performances of the instrument. Herein, we introduce an analytical strategy for addressing this problem in large-scale microbial studies. Our approach quantifies microbial boundary fluxes using two zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) columns that are plumbed to enable offline column equilibration. Using this strategy, we show that over 397 common metabolites can be resolved in 4.5 min per sample and that metabolites can be quantified with a median coefficient of variation of 0.127 across 1100 technical replicates. We illustrate the utility of this strategy via an analysis of 960 strains of Staphylococcus aureus isolated from bloodstream infections. These data capture the diversity of metabolic phenotypes observed in clinical isolates and provide an example of how large-scale investigations can leverage our novel analytical strategy.

Detecting Proteomic Indicators to Distinguish Diabetic Nephropathy from Hypertensive Nephrosclerosis by Integrating Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging with High-Mass Accuracy Mass Spectrometry.

INTRODUCTION: Diabetic nephropathy (DN) and hypertensive nephrosclerosis (HN) represent the most common causes of chronic kidney disease (CKD) and many patients progress to -end-stage renal disease. Patients are treated primarily through the management of cardiovas-cular risk factors and hypertension; however patients with HN have a more favorable outcome. A noninvasive clinical approach to separate these two entities, especially in hypertensive patients who also have diabetes, would allow for targeted treatment and more appropriate resource allocation to those patients at the highest risk of CKD progression. Meth-ods: In this preliminary study, high-spatial-resolution matrix-assisted laser desorption/ion-ization (MALDI) mass spectrometry imaging (MSI) was integrated with high-mass accuracy MALDI-FTICR-MS and nLC-ESI-MS/MS analysis in order to detect tissue proteins within kidney biopsies to discriminate cases of DN (n = 9) from cases of HN (n = 9). RESULTS: Differences in the tryptic peptide profiles of the 2 groups could clearly be detected, with these becoming even more evident in the more severe histological classes, even if this was not evident with routine histology. In particular, 4 putative proteins were detected and had a higher signal intensity within regions of DN tissue with extensive sclerosis or fibrosis. Among these, 2 proteins (PGRMC1 and CO3) had a signal intensity that increased at the latter stages of the disease and may be associated with progression. DISCUSSION/CONCLUSION: This preliminary study represents a valuable starting point for a future study employing a larger cohort of patients to develop sensitive and specific protein biomarkers that could reliably differentiate between diabetic and hypertensive causes of CKD to allow for improved diagnosis, fewer biopsy procedures, and refined treatment approaches for clinicians.

A case of aggressive atypical anti-GBM disease complicated by CMV pneumonitis.

BACKGROUND: Anti-glomerular basement membrane (anti-GBM) disease is characterized by circulating IgG glomerular basement membrane antibodies and is clinically expressed as a rapidly progressive crescentic glomerulonephritis (GN), with 30-60% of patients also developing pulmonary hemorrhage. Classically, the renal biopsy shows glomerular crescent formation, bright linear staining of glomerular basement membranes (GBM) for IgG on direct immunofluorescence (IF), and the serologic presence of circulating anti-GBM antibodies. Recently, patients with linear IgG IF staining, undetectable circulating anti-GBM antibodies and glomerular changes atypical for anti-GBM disease have been described as "atypical anti-GBM disease", with a distinctly more benign clinical course than typical anti-GBM disease. We present a case report of a patient with negative anti-GBM serology but positive linear IgG staining by IF, severe diffuse crescentic and endocapillary proliferative glomerulonephritis, and renal failure, complicated by severe pulmonary hemorrhage after immunosuppression, likely due to cytomegalovirus (CMV) pneumonitis. CASE PRESENTATION: A 24-year-old man was admitted to hospital with hemoptysis and renal failure. Investigations for anti-GBM serology by addressable laser bead immunoassay (ALBIA) was negative for anti-GBM antibodies. Renal biopsy showed diffuse endocapillary proliferative glomerulonephritis with membranoproliferative features and diffuse circumferential crescents. Direct IF showed strong linear staining for IgG along GBMs. The patient's hemoptysis improved with immunosuppression, but 1 month later he was readmitted with gross hemoptysis, which was refractory to further cyclophosphamide, plasma exchange and rituximab. Bronchoalveolar lavage (BAL) and blood work confirmed CMV pneumonitis, and the patient's hemoptysis resolved with ganciclovir, though he became dialysis dependent. CONCLUSIONS: This case demonstrates an atypical presentation of anti-GBM disease with both crescents and endocapillary hypercellularity and negative serology. The patient is dialysis dependent, unlike most previously described patients with atypical anti-GBM disease. The course was complicated by CMV pneumonitis, which contributed to the severity of the pulmonary manifestations and added diagnostic difficulty.

Macrophage Uptake of Necrotic Cell DNA Activates the AIM2 Inflammasome to Regulate a Proinflammatory Phenotype in CKD.

Nonmicrobial inflammation contributes to CKD progression and fibrosis. Absent in melanoma 2 (AIM2) is an inflammasome-forming receptor for double-stranded DNA. AIM2 is expressed in the kidney and activated mainly by macrophages. We investigated the potential pathogenic role of the AIM2 inflammasome in kidney disease. In kidneys from patients with diabetic or nondiabetic CKD, immunofluorescence showed AIM2 expression in glomeruli, tubules, and infiltrating leukocytes. In a mouse model of unilateral ureteral obstruction (UUO), Aim2 deficiency attenuated the renal injury, fibrosis, and inflammation observed in wild-type (WT) littermates. In bone marrow chimera studies, UUO induced substantially more tubular injury and IL-1ß cleavage in Aim2-/- or WT mice that received WT bone marrow than in WT mice that received Aim2-/- bone marrow. Intravital microscopy of the kidney in LysM(gfp/gfp) mice 5-6 days after UUO demonstrated the significant recruitment of GFP+ proinflammatory macrophages that crawled along injured tubules, engulfed DNA from necrotic cells, and expressed active caspase-1. DNA uptake occurred in large vacuolar structures within recruited macrophages but not resident CX3CR1+ renal phagocytes. In vitro, macrophages that engulfed necrotic debris showed AIM2-dependent activation of caspase-1 and IL-1ß, as well as the formation of AIM2+ ASC specks. ASC specks are a hallmark of inflammasome activation. Cotreatment with DNaseI attenuated the increase in IL-1ß levels, confirming that DNA was the principal damage-associated molecular pattern in this process. Therefore, the activation of the AIM2 inflammasome by DNA from necrotic cells drives a proinflammatory phenotype that contributes to chronic injury in the kidney.

Sociodemographic associations with abnormal estimated glomerular filtration rate (eGFR) in a large Canadian city: a cross-sectional observation study.

BACKGROUND: Chronic kidney disease (CKD) is often asymptomatic in its early stages but is indicated and is diagnosed with an estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73m2. Certain sociodemographic groups are known to be at risk for CKD, but it is unclear if there are strong associations between these at risk groups with abnormal eGFR test results in Canada. Using only secondary laboratory and Census data, geospatial variation and sociodemographic associations with abnormal eGFR result rate were investigated in Calgary, Alberta. METHODS: Secondary laboratory data from all adult community patients who received an eGFR test result were collected from Calgary Laboratory Service's Laboratory Information System, which is the sole supplier of laboratory services for the large metropolitan city. Group-level sociodemographic variables were inferred by combining laboratory data with the 2011 Canadian Census data. Poisson regression and relative risk (RR) were used to calculate associations between sociodemographic variables with abnormal eGFR. Geographical distribution of abnormal eGFR result rates were analyzed by geospatial analysis using ArcGIS. RESULTS: Of the 346,663 adult community patients who received an eGFR test result, 28,091 were abnormal (8.1%; eGFR < 60 ml/min/1.73m2). Geospatial analysis revealed distinct geographical variation in abnormal eGFR result rates in Calgary. Women (RR = 1.11, P < 0.0001), and the elderly (age ≥ 70 years; P < 0.0001) were significantly associated with an increased risk for CKD, while visible minority Chinese (RR = 0.73, P = 0.0011), South Asians (RR = 0.67, P < 0.0001) and those with a high median household income (RR = 0.88, P < 0.0001) had a significantly reduced risk for CKD. CONCLUSIONS: Presented here are significant sociodemographic risk associations, and geospatial clustering of abnormal eGFR result rates in a large metropolitan Canadian city. Using solely publically available secondary laboratory and Census data, the results from this study aligns with known sociodemographic risk factors for CKD, as certain sociodemographic variables were at a higher risk for having an abnormal eGFR test result, while others were protective in this analysis.

The biobank for the molecular classification of kidney disease: research translation and precision medicine in nephrology.

BACKGROUND: Advances in technology and the ability to interrogate disease pathogenesis using systems biology approaches are exploding. As exemplified by the substantial progress in the personalized diagnosis and treatment of cancer, the application of systems biology to enable precision medicine in other disciplines such as Nephrology is well underway. Infrastructure that permits the integration of clinical data, patient biospecimens and advanced technologies is required for institutions to contribute to, and benefit from research in molecular disease classification and to devise specific and patient-oriented treatments. METHODS AND RESULTS: We describe the establishment of the Biobank for the Molecular Classification of Kidney Disease (BMCKD) at the University of Calgary, Alberta, Canada. The BMCKD consists of a fully equipped wet laboratory, an information technology infrastructure, and a formal operational, ethical and legal framework for banking human biospecimens and storing clinical data. The BMCKD first consolidated a large retrospective cohort of kidney biopsy specimens to create a population-based renal pathology database and tissue inventory of glomerular and other kidney diseases. The BMCKD will continue to prospectively bank all kidney biopsies performed in Southern Alberta. The BMCKD is equipped to perform molecular, clinical and epidemiologic studies in renal pathology. The BMCKD also developed formal biobanking procedures for human specimens such as blood, urine and nucleic acids collected for basic and clinical research studies or for advanced diagnostic technologies in clinical care. The BMCKD is guided by standard operating procedures, an ethics framework and legal agreements with stakeholders that include researchers, data custodians and patients. The design and structure of the BMCKD permits its inclusion in a wide variety of research and clinical activities. CONCLUSION: The BMCKD is a core multidisciplinary facility that will bridge basic and clinical research and integrate precision medicine into renal pathology and nephrology.

Non-invasive biomarkers of disease activity and organ damage in ANCA-associated vasculitis: a systematic review.

BACKGROUND: In anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), histopathological assessment of affected tissue is often necessary for diagnosis and assessment of disease extent. There is a requirement for validated non-invasive biomarkers to avoid the need for serial tissue biopsies. METHODS: A systematic review of scientific databases from 2012 until present was performed to identify studies fulfilling the inclusion criteria. Studies were assessed for quality using the Strengthening the Reporting of Observational Studies in Epidemiology checklist for cohort, case-control and cross-sectional studies and the Risk of Bias Assessment tool for Non-randomised Studies, or the Cochrane Risk of Bias tool 2.0 for randomised controlled trials. A descriptive synthesis of the data for non-invasive (blood-based or urinary) biomarkers of AAV-related disease activity and organ damage was performed. RESULTS: Twenty-two high quality studies were included. These articles reported the value of blood-based and urinary biomarkers including anti-neutrophil cytoplasmic antibodies, immune cells, complement factors, gene expression profiles, cytokines, chemokines and other proteins in the assessment of disease activity and/or organ damage in patients with AAV. Many of these biomarkers involve the alternative complement pathway, neutrophil activation and macrophage activation. CONCLUSION: This is the first contemporary systematic review synthesising the value of non-invasive biomarkers of AAV-related disease activity and organ damage. The incorporation of individual markers in combined biomarker profiles might enhance clinical decision-making. Many unmet needs were identified; few studies involve oeosinophilic granulomatosis with polyangiitis and patients with childhood-onset AAV. Further validation of the candidate biomarkers is warranted in large prospective studies to bridge the existing knowledge gaps and apply precision health to systemic vasculitis.

Proteinase-activated receptor-1 and immunomodulatory effects of a PAR1-activating peptide in a mouse model of prostatitis.

BACKGROUND: Nonbacterial prostatitis has no established etiology. We hypothesized that proteinase-activated receptor-1 (PAR1) can play a role in prostatitis. We therefore investigated the effects of PAR1 stimulation in the context of a new model of murine nonbacterial prostatitis. METHODS: Using a hapten (ethanol-dinitrobenzene sulfonic acid- (DNBS-)) induced prostatitis model with both wild-type and PAR1-null mice, we examined (1) the location of PAR1 in the mouse prostate and (2) the impact of a PAR1-activating peptide (TFLLR-NH2: PAR1-TF) on ethanol-DNBS-induced inflammation. RESULTS: Ethanol-DNBS-induced inflammation was maximal at 2 days. In the tissue, PAR1 was expressed predominantly along the apical acini of prostatic epithelium. Although PAR1-TF on its own did not cause inflammation, its coadministration with ethanol-DNBS reduced all indices of acute prostatitis. Further, PAR1-TF administration doubled the prostatic production of interleukin-10 (IL-10) compared with ethanol-DNBS treatment alone. This enhanced IL-10 was not observed in PAR1-null mice and was not caused by the reverse-sequence receptor-inactive peptide, RLLFT-NH2. Surprisingly, PAR1-TF, also diminished ethanol-DNBS-induced inflammation in PAR1-null mice. CONCLUSIONS: PAR1 is expressed in the mouse prostate and its activation by PAR1-TF elicits immunomodulatory effects during ethanol-DNBS-induced prostatitis. However, PAR1-TF also diminishes ethanol-DNBS-induced inflammation via a non-PAR1 mechanism by activating an as-yet unknown receptor.

Detection and Typing of Renal Amyloidosis by Fluorescence Spectroscopy Using the Environmentally Sensitive Fluorophore K114.

PURPOSE: To demonstrate that spectral analysis using the K114 fluorophore can detect and differentiate AL and AA renal amyloidosis. PROCEDURES: Kidney biopsies from patients with AL amyloidosis, AA amyloidosis, and normal samples with no evident pathology were stained with Congo Red and K114. The specimens were imaged on a spectral confocal microscope. RESULTS: Congo Red displayed homogeneous spectra across the three tissue types while K114 chromatically distinguished between normal tissue, AL amyloid, and AA amyloid. Additionally, Congo Red displayed an increased risk of false positive staining compared to K114. Spectral phasors computed from K114-stained tissue sections quantitatively differentiated the three tissue types. K114-stained amyloid deposits displayed a significantly greater increase in brightness after 50 images acquired in rapid succession compared to normal tissue. Quantitative analysis of intensity changes in the background of diseased tissue also differentiated AL and AA amyloid samples, suggesting widespread amyloid deposition. Both amyloid and the backgrounds of diseased samples red-shifted while normal tissue blue-shifted in response to repeated imaging, supporting this theory. CONCLUSIONS: K114 staining of renal biopsies is a promising technique to detect and differentiate types of renal amyloidosis. Due to the advantages this method has over traditional Congo Red staining, the techniques presented here warrant further development for potential use in clinical settings.

Acute Kidney Allograft Rejection Following Coronavirus mRNA Vaccination: A Case Report.

Supplemental Digital Content is available in the text.

Dipeptidase-1 governs renal inflammation during ischemia reperfusion injury.

The mechanisms that drive leukocyte recruitment to the kidney are incompletely understood. Dipeptidase-1 (DPEP1) is a major neutrophil adhesion receptor highly expressed on proximal tubular cells and peritubular capillaries of the kidney. Renal ischemia reperfusion injury (IRI) induces robust neutrophil and monocyte recruitment and causes acute kidney injury (AKI). Renal inflammation and the AKI phenotype were attenuated in Dpep1-/- mice or mice pretreated with DPEP1 antagonists, including the LSALT peptide, a nonenzymatic DPEP1 inhibitor. DPEP1 deficiency or inhibition primarily blocked neutrophil adhesion to peritubular capillaries and reduced inflammatory monocyte recruitment to the kidney after IRI. CD44 but not ICAM-1 blockade also decreased neutrophil recruitment to the kidney during IRI and was additive to DPEP1 effects. DPEP1, CD44, and ICAM-1 all contributed to the recruitment of monocyte/macrophages to the kidney following IRI. These results identify DPEP1 as a major leukocyte adhesion receptor in the kidney and potential therapeutic target for AKI.

Analysis of the glomerular basement membrane in images of renal biopsies using the split-and-merge method: a pilot study.

Abnormal thinning, thickening, or variation in the thickness of the glomerular basement membrane (GBM) are caused by familial hematuria, diabetes mellitus, and Alport syndrome, respectively. We propose a semi-automated procedure for the segmentation and analysis of the thickness of the GBM in images of renal biopsy samples obtained by using a transmission electron microscope (TEM). The procedure includes the split-and-merge algorithm, morphological image processing, skeletonization, and statistical analysis of the width of the GBM. The procedure was tested with 34 TEM images of six patients. The mean and standard deviation of the GBM width for a patient with normal GBM were estimated to be 368 +/- 177 nm, those for a patient with thin GBM associated with familial hematuria were 216 +/- 95 nm, and those for a patient with thick GBM due to diabetic nephropathy were 1,094 +/- 361 nm. Comparative analysis of the results of image processing with manual measurements by an experienced renal pathologist indicated low error in the range of 12 +/- 9 nm.

Segmentation and analysis of the glomerular basement membrane in renal biopsy samples using active contours: a pilot study.

Some renal diseases cause changes in the structure of the glomerular basement membranes (GBM). Measurement of the thickness of the GBM can be performed on transmission electron microscopy (TEM) images of renal biopsy samples. Increased thickness of the GBM is observed in patients with diabetic nephropathy. Abnormally thin GBMs are associated with hematuria. We propose image processing methods for the detection and measurement of the GBM. The methods include edge detection, morphological image processing, active contour modeling, skeletonization, and statistical analysis of the width of the GBM. In the present pilot study, the methods were tested with 34 TEM images of six patients. The estimated mean and standard deviation of the GBM width for a patient with normal GBM were 348 +/- 135 nm; those for a patient with thin GBMs due to hematuria were 227 +/- 94 nm; and those for a patient with diabetic nephropathy were 1,152 +/- 411 nm. Comparison with manual measurements by an experienced renal pathologist indicated low error in the range of 36 +/- 11 nm.

Trends in Biopsy-Based Diagnosis of Kidney Disease: A Population Study.

BACKGROUND: Kidney biopsy is considered the gold standard for diagnosis of renal disease. It is increasingly performed in cases of diagnostic uncertainty, including in patients with coexistent diabetes and hypertension, for which a presumptive clinical diagnosis can be made. Little is known about the incidence and distribution of biopsy-proven kidney diseases. Changes in the distribution of biopsy diagnoses over time may have significant implications for resource allocation and future research. OBJECTIVE: We studied the relative frequency of kidney diseases in Southern Alberta over the past 30 years, to determine whether the population-standardized annual biopsy rate and incidence of selected diagnostic categories have changed. We hypothesized an increasing incidence of renal biopsies and a growing proportion of nonglomerular diseases (eg, tubulointerstitial disorders) likely due to evolving indications for biopsy. Given the rise in obesity, diabetes, and aging population with chronic kidney disease (CKD), we anticipated a rise in nephroangiosclerosis and diabetic nephropathy over time. DESIGN: Retrospective population-based cohort study using the Biobank for the Molecular Classification of Kidney Disease (BMCKD). SETTING: Southern Alberta, Canada. PATIENTS: All patients who underwent renal biopsy between 1985 and 2015 in our database. MEASUREMENTS: We used descriptive and quantitative analysis to characterize demographics and biopsy-based diagnoses. METHODS: We conducted a retrospective population-based cohort study to analyze all consecutive patients who underwent at least one kidney biopsy over a 30-year period in Southern Alberta (1985-2015). We considered the first adequate biopsy. We described the annual standardized incidence of biopsy-proven kidney diseases over time and summarized associated patient characteristics. We assumed a Poisson distribution for biopsy counts and used provincial demographic information to standardize rates. RESULTS: During the study period, 6434 people (58% male; mean age: 47.9 years) underwent a kidney biopsy. The population-standardized annual biopsy rate increased from 10.8 biopsies per 100 000 person-years in the first 5 years of the study (1985-1989) to 18.2 biopsies per 100 000 person-years in the last 5 years (2010-2014). The mean age at the time of biopsy increased from 42.5 years (1985-1989) to 51.4 years (2010-2014). Glomerular diseases remained the most prevalent histopathological group, with a growing representation of diabetic kidney disease from 3.69% to 16.18%, and a relative decrease in the proportion of other glomerular diseases from 72.32% to 62.92% of glomerular diagnoses. Tubulointerstitial diseases increased from 5.87% to 7.36% of total diagnoses. LIMITATIONS: Classification schemes have changed over time, so recently recognized conditions may have been misclassified in earlier data. There was a changing group of pathologists and nephrologists over this period. Variations in interpretation and application of biopsy indications by physician may influence recorded prevalence of certain diagnoses. We do not yet have complete information on indications or patient outcomes linked to the database. CONCLUSIONS: In Southern Alberta, kidney biopsy is being utilized more frequently and in older people. Diabetic nephropathy is increasingly diagnosed, which may reflect either or both changes in the prevalence of causative factors and local biopsy practices.

CONTEXTE: La biopsie rénale est considérée comme la méthode par excellence pour diagnostiquer des néphropathies. Elle est de plus en plus pratiquée dans les cas de diagnostics incertains, notamment chez les patients souffrant également de diabète et d'hypertension, et pour lesquels un diagnostic clinique présomptif peut être posé. On en sait encore peu sur l'incidence et la distribution statistique des néphropathies avérées par biopsie. Des variations dans la distribution statistique des diagnostics par biopsie au fil du temps pourraient avoir des répercussions significatives sur l'affectation des ressources et sur les recherches futures. OBJECTIFS: Nous voulions savoir si le taux de biopsies annuel normalisé selon la population et l'incidence des catégories de diagnostic sélectionnées avaient varié. Nous avions émis l'hypothèse d'une incidence croissante des biopsies rénales et d'une proportion croissante d'affections non glomérulaires (notamment les troubles tubulo-interstitiels) susceptibles d'être attribuables à une demande croissante pour des biopsies. Compte tenu de l'augmentation des cas d'obésité et de diabète, et du vieillissement de la population atteinte de néphropathies chroniques, nous avions anticipé une augmentation des cas de néphroangiosclérose et de néphropathie diabétique au fil du temps. TYPE D'ÉTUDE: Une étude de cohorte rétrospective sur des données provenant de la biobanque BMCKD (Biobank for the Molecular Classification of Kidney Disease). CADRE DE L'ÉTUDE: Le sud de la province de l'Alberta, au Canada. SUJETS: Tous les patients répertoriés dans notre base de données en raison d'une biopsie rénale subie entre 1985 et 2015. MESURES: Nous avons employé l'analyse descriptive et quantitative pour caractériser les données démographiques des patients et le diagnostic posé à la suite d'une biopsie. MÉTHODOLOGIE: Nous avons mené une étude de cohorte rétrospective pour examiner tous les patients consécutifs ayant subi au moins une biopsie rénale sur une période de 30 ans (1985 à 2015) dans le sud de l'Alberta. Nous avons tenu compte de la première biopsie satisfaisante. Nous avons mesuré l'incidence annuelle normalisée des néphropathies avérées par biopsie au fil du temps et nous avons résumé les caractéristiques des patients qui y étaient associés. Une distribution de Poisson a permis d'établir le nombre de biopsies, alors que les données démographiques provinciales ont servi à la normalisation des taux. RÉSULTATS: Au cours de la période étudiée, 6 434 personnes (âge moyen : 47,9 ans), dont 58 % étaient des hommes, ont subi une biopsie rénale. Entre les cinq premières années (1985-1989) et les cinq dernières années de l'étude (2010-2014), le taux de biopsies annuel normalisé selon la population est passé de 10,8 par 100 000 années-personnes à 12,8 par 100 000 années-personnes; l'âge moyen au moment de subir la biopsie est passé de 42,5 ans à 51,4 ans. Le groupe histopathologique des atteintes glomérulaires est demeuré le plus prévalent des diagnostics glomérulaires avec une représentation croissante des cas de néphropathies diabétiques (de 3,69 % à 16,18 %) et une diminution relative de la proportion des autres atteintes glomérulaires (de 72,32 % à 62,92 %). Quant aux affections tubulo-insterstitielles, elles sont passées de 5,87 % à 7,36 % de tous les diagnostics posés au cours de la période étudiée. LIMITES: Plusieurs variables ont évolué au cours de la période étudiée : les équipes de pathologistes et de néphrologues ont changé, et les systèmes de classification ont été modifiés; de sorte que certaines affections diagnostiquées récemment pourraient avoir été mal classées dans les données antérieures. De plus, des différences dans l'interprétation et l'application des biopsies de la part des médecins pourraient avoir influencé la prévalence consignée pour certains diagnostics. Nous ne disposons toujours pas d'informations complètes sur les indications et les résultats des patients liés à la base de données. CONCLUSION: Dans le sud de l'Alberta, la biopsie rénale est de plus pratiquée, et ce, chez des patients plus âgés. La néphropathie diabétique est de plus en plus diagnostiquée; ce qui pourrait indiquer des variations dans la prévalence des facteurs en cause et/ou des changements dans les pratiques locales quant à l'usage de la biopsie.

Anticoagulant Related Nephropathy Induced by Dabigatran.

We describe a case of biopsy-proven dabigatran related nephropathy in a patient without underlying IgA nephropathy. To date, dabigatran related nephropathy was only reported in patients with concurrent or undiagnosed IgA nephropathy, suggesting that it may predispose patients to dabigatran associated injury. The patient is an 81-year-old woman with multiple medical comorbidities, including nonvalvular atrial fibrillation, who was anticoagulated with dabigatran. She presented to hospital with acute kidney injury in the setting of volume overload. Her estimated glomerular filtration rate decreased from a baseline of 57 mL/min/1.73 m2 to 4 mL/min/1.73 m2, necessitating hemodialysis. Renal ultrasound findings, fractional excretion of sodium, and urinalysis suggested acute kidney injury. Renal biopsy showed acute tubular injury, tubular red blood cell casts, and an absence of active glomerulonephritis, similar to the pathological findings of warfarin related nephropathy. A diagnosis of anticoagulant related nephropathy secondary to dabigatran was therefore established. This case demonstrates that dabigatran, like warfarin, may increase tubular bleeding risk in patients, irrespective of underlying kidney or glomerular disease.

Renal immune surveillance and dipeptidase-1 contribute to contrast-induced acute kidney injury.

Radiographic contrast agents cause acute kidney injury (AKI), yet the underlying pathogenesis is poorly understood. Nod-like receptor pyrin containing 3-deficient (Nlrp3-deficient) mice displayed reduced epithelial cell injury and inflammation in the kidney in a model of contrast-induced AKI (CI-AKI). Unexpectedly, contrast agents directly induced tubular epithelial cell death in vitro that was not dependent on Nlrp3. Rather, contrast agents activated the canonical Nlrp3 inflammasome in macrophages. Intravital microscopy revealed diatrizoate (DTA) uptake within minutes in perivascular CX3CR1+ resident phagocytes in the kidney. Following rapid filtration into the tubular luminal space, DTA was reabsorbed and concentrated in tubular epithelial cells via the brush border enzyme dipeptidase-1 in volume-depleted but not euvolemic mice. LysM-GFP+ macrophages recruited to the kidney interstitial space ingested contrast material transported from the urine via direct interactions with tubules. CI-AKI was dependent on resident renal phagocytes, IL-1, leukocyte recruitment, and dipeptidase-1. Levels of the inflammasome-related urinary biomarkers IL-18 and caspase-1 were increased immediately following contrast administration in patients undergoing coronary angiography, consistent with the acute renal effects observed in mice. Taken together, these data show that CI-AKI is a multistep process that involves immune surveillance by resident and infiltrating renal phagocytes, Nlrp3-dependent inflammation, and the tubular reabsorption of contrast via dipeptidase-1.

Glomerular mesangial fibrillary deposits in a patient with diabetes mellitus.

Various systemic or primary glomerular diseases can result in deposition of fibrillary material in the glomerular tuft and may cause an important diagnostic challenge for the pathologists. Biopsy findings of a patient with type 2 diabetes is presented here in which striking fibrillary structures were identified in the mesangium by ultrastructural examination. The distinction between diabetic fibrillosis and fibrillary glomerulonephritis accompanying diabetic nephropathy is discussed in the setting of a literature review.

NLRP3 Localizes to the Tubular Epithelium in Human Kidney and Correlates With Outcome in IgA Nephropathy.

Nod-like receptor pyrin domain-containing-3 (NLRP3) has been implicated in the pathogenesis of experimental renal injury, yet its characterization in human kidney disease remains largely unexplored. NLRP3 expression was evaluated in human kidney biopsies, primary renal tubular cells (HPTC) and correlated to disease outcomes in patients with IgA nephropathy (IgAN). NLRP3 localized to renal tubules in normal human kidney tissue and to mitochondria within HPTC by immunohistochemistry and immunofluorescence microscopy. Compared to control kidneys, NLRP3 gene expression was increased in biopsies of patients with IgAN. While NLRP3 expression in IgAN was detected in glomeruli, it remained largely confined to the tubular epithelial compartment. In vitro NLRP3 mRNA and protein expression were transiently induced in HPTC by TGF-ß1 but subsequently diminished over time as cells lost their epithelial phenotype in a process regulated by transcription and ubiquitin-mediated degradation. Consistent with the in vitro data, low NLRP3 mRNA expression in kidney biopsies was associated with a linear trend of higher risk of composite endpoint of doubling serum creatinine and end stage renal disease in patients with IgAN. Taken together, these data show that NLRP3 is primarily a kidney tubule-expressed protein that decreases in abundance in progressive IgAN.

The absence of delayed graft function is predicted by the presence of manganese-superoxide dismutase in distal tubules of renal allografts.

BACKGROUND: Acute tubular necrosis (ATN) in renal allograft biopsies correlates poorly with delayed graft function (DGF). Factors involved in the pathogenesis of DGF were evaluated in biopsies in an attempt to refine the recognition of DGF. METHODS: Anti-cubulin and anti-AE-1/AE-3 antibodies identified proximal and distal tubules, respectively. The terminal deoxynucleotide transferase-mediated dUTP nick-end labeling technique and active caspase-3 staining were used to demonstrate apoptosis. Antibodies against superoxide dismutase (SOD) were used as markers of the protective tubular response. Tubular regeneration was evaluated using anti-ki 67 and antivimentin antibodies. RESULTS: Of a total of 40 biopsies, 9 were associated with DGF. ATN was seen in 16 biopsies; 5 were associated with DGF. The finding of ATN in the biopsy of a graft predicted DGF in only 56% of cases. Absence of distal caspase-3 staining predicted the absence of ATN in 87% of cases. The presence of caspase-3 predicted ATN in 54% of cases. The detection of manganese-SOD in distal tubules predicts the absence of DGF in 76% of the cases. CONCLUSIONS: The use of immunohistochemical staining on posttransplant renal biopsies improved its predictive value with respect to ATN and DGF: The absence of active caspase-3 in distal tubular epithelium predicts the absence of ATN in 87% of cases, whereas its presence predicts ATN in 54% of cases. The presence of manganese-SOD in distal tubules predicts the absence of DGF in 76% of cases.