Gene expression analysis in microdissected renal tissue - Current challenges and strategies

The architecture and compartmentalization of the kidney has stimulated the development of an array of microtechniques to study the functional differences between the distinct nephron segments. With the vast amounts of genomic sequence data now available, the groundwork has been laid for a comprehensive characterization of the molecular pathways defining the differences in nephron function. With the development of sensitive gene expression techniques the tools for a comprehensive molecular analysis of specific renal microenvironments have been provided: Quantitative RT-PCR technologies now allow the analysis of specific mRNAs from as little as single microdissected renal cells. A more global view of gene expression regulation is a logical development from the application of large scale profiling techniques. In this review, we will discuss the power and pitfalls of these approaches, including their potential for the functional characterization of nephron heterogeneity and diagnostic application in renal disease. Copyright (C) 2002 S. Karger AG, Basel

Genexpressionsanalysen an Nierenbiopsien: Die Europäische Renale cDNA Bank - Kröner-Fresenius Biopsiebank

Zusammenfassung: Die Nierenbiopsie und deren histologische Aufarbeitung sind klinische Routine und diagnostischer Goldstandard in der Nephrologie. Neue Methoden ermöglichen an dem gewonnenen Material neben der etablierten Diagnostik auch die umfassende Analyse der Genexpression. Anhand von Ergebnissen einer europäischen Multicenterstudie zur Genexpressionsanalyse an Nierenbiopsien wird gezeigt, dass dieser moderne Ansatz nicht nur die sogenannte Grundlagenforschung bereichert, sondern in Zukunft die Biopsiediagnostik ergänzen könnte. Die Ziele sind hierbei erweiterte Diagnosestellung, spezifischere Therapieentscheidung und individuelle Prognoseabschätzun

The immune cell landscape in kidneys of patients with lupus nephritis.

Lupus nephritis is a potentially fatal autoimmune disease for which the current treatment is ineffective and often toxic. To develop mechanistic hypotheses of disease, we analyzed kidney samples from patients with lupus nephritis and from healthy control subjects using single-cell RNA sequencing. Our analysis revealed 21 subsets of leukocytes active in disease, including multiple populations of myeloid cells, T cells, natural killer cells and B cells that demonstrated both pro-inflammatory responses and inflammation-resolving responses. We found evidence of local activation of B cells correlated with an age-associated B-cell signature and evidence of progressive stages of monocyte differentiation within the kidney. A clear interferon response was observed in most cells. Two chemokine receptors, CXCR4 and CX3CR1, were broadly expressed, implying a potentially central role in cell trafficking. Gene expression of immune cells in urine and kidney was highly correlated, which would suggest that urine might serve as a surrogate for kidney biopsies

A role for genetic susceptibility in sporadic focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a syndrome that involves kidney podocyte dysfunction and causes chronic kidney disease. Multiple factors including chemical toxicity, inflammation, and infection underlie FSGS; however, highly penetrant disease genes have been identified in a small fraction of patients with a family history of FSGS. Variants of apolipoprotein L1 (APOL1) have been linked to FSGS in African Americans with HIV or hypertension, supporting the proposal that genetic factors enhance FSGS susceptibility. Here, we used sequencing to investigate whether genetics plays a role in the majority of FSGS cases that are identified as primary or sporadic FSGS and have no known cause. Given the limited number of biopsy-proven cases with ethnically matched controls, we devised an analytic strategy to identify and rank potential candidate genes and used an animal model for validation. Nine candidate FSGS susceptibility genes were identified in our patient cohort, and three were validated using a high-throughput mouse method that we developed. Specifically, we introduced a podocyte-specific, doxycycline-inducible transactivator into a murine embryonic stem cell line with an FSGS-susceptible genetic background that allows shRNA-mediated targeting of candidate genes in the adult kidney. Our analysis supports a broader role for genetic susceptibility of both sporadic and familial cases of FSGS and provides a tool to rapidly evaluate candidate FSGS-associated genes

Estimated GFR Trajectories in Pediatric and Adult Nephrotic Syndrome: Results From the Nephrotic Syndrome Study Network (NEPTUNE)

56% and 16% had PNL 50%, respectively. In both adults and pediatric patients, higher baseline eGFR was associated with higher PNL, whereas longer follow-up time was associated with lower PNL. Higher urine protein-creatinine ratio and steroid use were also associated with higher PNL in adults. Higher percentages of tubular atrophy and foot-process effacement were associated with lower and higher PNLs, respectively, in adults. Limitations: Relatively short follow-up time, inability to assess acute kidney injury events, and variable eGFR measurement frequency across patients. Conclusions: Although increasing follow-up time resulted in more linear trajectories, nonlinear eGFR trajectories were common in this cohort. Future studies in nephrotic syndrome should consider novel outcomes that do not rely on linearity assumptions.Rationale & Objective: Surrogate outcomes for end-stage kidney disease often assume linear changes, which may not reflect true estimated glomerular filtration rate (eGFR) trajectories. This study's objective was to characterize nonlinear eGFR trajectories in nephrotic syndrome. Study Design: Observational cohort study. Setting & Participants: Nephrotic Syndrome Study Network (NEPTUNE) is a multicenter study of adult and pediatric patients with proteinuria enrolled at clinically indicated kidney biopsy or initial presentation of disease (pediatric only). Predictors: Patient demographic, clinical, and pathology variables at study enrollment and follow-up time. Outcome: eGFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration (patients ≥ 18 years old) or modified Chronic Kidney Disease in Children Study–Schwartz (patients < 18 years) formulas. The probability of nonlinearity (PNL) was calculated for individual eGFR trajectories. Analytical Approach: Associations between predictors and PNL were assessed using multivariable linear regression. Results: 453 patients with ≥3 eGFR measurements and 1 or more year of follow-up were included (median follow-up, 3.6 years). Median PNL was 0.05

Reproducibility of the NEPTUNE descriptor-based scoring system on whole-slide images and histologic and ultrastructural digital images

The multicenter Nephrotic Syndrome Study Network (NEPTUNE) digital pathology scoring system employs a novel and comprehensive methodology to document pathologic features from whole-slide images, immunofluorescence and ultrastructural digital images. To estimate inter- and intra-reader concordance of this descriptor-based approach, data from 12 pathologists (eight NEPTUNE and four non-NEPTUNE) with experience from training to 30 years were collected. A descriptor reference manual was generated and a webinar-based protocol for consensus/cross-training implemented. Intra-reader concordance for 51 glomerular descriptors was evaluated on jpeg images by seven NEPTUNE pathologists scoring 131 glomeruli three times (Tests I, II, and III), each test following a consensus webinar review. Inter-reader concordance of glomerular descriptors was evaluated in 315 glomeruli by all pathologists; interstitial fibrosis and tubular atrophy (244 cases, whole-slide images) and four ultrastructural podocyte descriptors (178 cases, jpeg images) were evaluated once by six and five pathologists, respectively. Cohen’s kappa for inter-reader concordance for 48/51 glomerular descriptors with sufficient observations was moderate (0.40<kappa ≤0.60) for 17 and good (0.60<kappa ≤0.80) for 8, for 52% with moderate or better kappas. Clustering of glomerular descriptors based on similar pathologic features improved concordance. Concordance was independent of years of experience, and increased with webinar cross-training. Excellent concordance was achieved for interstitial fibrosis and tubular atrophy. Moderate-to-excellent concordance was achieved for all ultrastructural podocyte descriptors, with good-to-excellent concordance for descriptors commonly used in clinical practice, foot process effacement, and microvillous transformation. NEPTUNE digital pathology scoring system enables novel morphologic profiling of renal structures. For all histologic and ultrastructural descriptors tested with sufficient observations, moderate-to-excellent concordance was seen for 31/54 (57%). Descriptors not sufficiently represented will require further testing. This study proffers the NEPTUNE digital pathology scoring system as a model for standardization of renal biopsy interpretation extendable outside the NEPTUNE consortium, enabling international collaborations

Global kidney health 2017 and beyond: a roadmap for closing gaps in care, research, and policy

The global nephrology community recognises the need for a cohesive plan to address the problem of chronic kidney disease (CKD). In July, 2016, the International Society of Nephrology hosted a CKD summit of more than 85 people with diverse expertise and professional backgrounds from around the globe. The purpose was to identify and prioritise key activities for the next 5-10 years in the domains of clinical care, research, and advocacy and to create an action plan and performance framework based on ten themes: strengthen CKD surveillance; tackle major risk factors for CKD; reduce acute kidney injury-a special risk factor for CKD; enhance understanding of the genetic causes of CKD; establish better diagnostic methods in CKD; improve understanding of the natural course of CKD; assess and implement established treatment options in patients with CKD; improve management of symptoms and complications of CKD; develop novel therapeutic interventions to slow CKD progression and reduce CKD complications; and increase the quantity and quality of clinical trials in CKD. Each group produced a prioritised list of goals, activities, and a set of key deliverable objectives for each of the themes. The intended users of this action plan are clinicians, patients, scientists, industry partners, governments, and advocacy organisations. Implementation of this integrated comprehensive plan will benefit people who are at risk for or affected by CKD worldwide

Blood Pressure and Visit-to-Visit Blood Pressure Variability among Individuals with Primary Proteinuric Glomerulopathies

Hypertension and blood pressure variability (BPV; SD and average real variability) in primary proteinuric glomerulopathies are not well described. Data were from 433 participants in the NEPTUNE (Nephrotic Syndrome Study Network). Hypertensive BP status was defined as previous history of hypertension or BP ≥140/90 mm Hg for adults/≥95th percentile for children at baseline. BPV was measured in participants with ≥3 visits in the first year. Two-hundred ninety-six adults (43 years [interquartile range, 32-57.8 years], 61.5% male) and 147 children (11 years [interquartile range, 5-14 years], 57.8% male) were evaluated. At baseline, 64.8% of adults and 46.9% of children were hypertensive. Histological diagnosis was associated with hypertensive status in adults (P=0.036). In adults, hypertensive status was associated with lower hazard of complete remission (hazard ratio, 0.36; 95% confidence interval, 0.19-0.68) and greater hazard of achieving the composite end point (end-stage renal disease or estimated glomerular filtration rate decline >40%; hazard ratio, 4.1; 95% confidence interval, 1.4-12). Greater systolic and diastolic SD and average real variability were also associated with greater hazard of reaching the composite end point in adults (all P<0.01). In children, greater BPV was an independent predictor of composite end point (determined by systolic SD and average real variability) and complete remission (determined by systolic and diastolic average real variability; all P<0.05). Hypertensive status was common among adults and children enrolled in NEPTUNE. Differences in hypertensive status prevalence, BPV, and treatment were found by age and histological diagnosis. In addition, hypertensive status and greater BPV were associated with poorer clinical outcomes