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Pediatric patients with nephrotic syndrome take medications long-term with significant toxicity and complex regimens, yet data on medication adherence are limited.In a multicenter observational study of patients with nephrotic syndrome, NEPTUNE (NCT01209000), we surveyed caregivers of patients19 years old and adolescent patients on medication adherence during longitudinal follow-up beginning in June 2015. Data extraction was in October 2020. We described the proportion of nonadherent patients at first survey. Participant social and economic factors, condition-related factors, therapy-related factors, and patient-related factors were examined for relationships with nonadherence by generalized linear mixed models using the longitudinal data. In exploratory fashion, we assessed the relationship between adherence and subsequent steroid response classification by binary logistic regression and adherence with healthcare utilization by Poisson regression.A total of 225 participants completed a median of 3 surveys during follow-up (IQR, 2-5), with a total of 743 surveys. Overall, 80 (36%) reported nonadherence with medications. In adjusted analysis, older age (per 1 year; OR 1.08; 95% CI, 1.03 1.12), lower maternal educational level (≥ high school vs.high school; OR 0.47; 95% CI 0.25 to 0.89), and increased parent and self-identification of medications barriers (per 1 point; OR 1.57; 95% CI, 1.15-2.15) were significantly associated with nonadherence. No relationship between nonadherence and subsequent frequency of healthcare utilization was observed. A trend toward increased subsequent steroid resistance classification was seen with nonadherence, though not statistically significant.Medication nonadherence is common in pediatric nephrotic syndrome. Investigations into the use of surveys in the clinic setting to identify at-risk patients and ways to support families over time are needed. A higher resolution version of the Graphical abstract is available as Supplementary information.

Background: The G1 and G2 alleles of apolipoprotein L1 (APOL1) are common in the Black population and associated with increased risk of focal segmental glomerulosclerosis (FSGS). The molecular mechanisms linking APOL1 risk variants with FSGS are not clearly understood, and APOL1’s natural absence in laboratory animals makes studying its pathobiology challenging. Methods: In a cohort of 90 Black patients with either FSGS or minimal change disease (MCD) enrolled in the Nephrotic Syndrome Study Network (58% pediatric onset), we used kidney biopsy traits as an intermediate outcome to help illuminate tissue-based consequences of APOL1 risk variants and expression. We tested associations between APOL1 risk alleles or glomerular APOL1 mRNA expression and 83 light- or electron-microscopy traits measuring structural and cellular kidney changes. Results: Under both recessive and dominant models in the FSGS patient subgroup (61%), APOL1 risk variants were significantly correlated (defined as FDR

The application of deep learning for automated segmentation (delineation of boundaries) of histologic primitives (structures) from whole slide images can facilitate the establishment of novel protocols for kidney biopsy assessment. Here, we developed and validated deep learning networks for the segmentation of histologic structures on kidney biopsies and nephrectomies. For development, we examined 125 biopsies for Minimal Change Disease collected across 29 NEPTUNE enrolling centers along with 459 whole slide images stained with Hematoxylin & Eosin (125), Periodic Acid Schiff (125), Silver (102), and Trichrome (107) divided into training, validation and testing sets (ratio 6:1:3). Histologic structures were manually segmented (30048 total annotations) by five nephropathologists. Twenty deep learning models were trained with optimal digital magnification across the structures and stains. Periodic Acid Schiff-stained whole slide images yielded the best concordance between pathologists and deep learning segmentation across all structures (F-scores: 0.93 for glomerular tufts, 0.94 for glomerular tuft plus Bowman's capsule, 0.91 for proximal tubules, 0.93 for distal tubular segments, 0.81 for peritubular capillaries, and 0.85 for arteries and afferent arterioles). Optimal digital magnifications were 5X for glomerular tuft/tuft plus Bowman's capsule, 10X for proximal/distal tubule, arteries and afferent arterioles, and 40X for peritubular capillaries. Silver stained whole slide images yielded the worst deep learning performance. Thus, this largest study to date adapted deep learning for the segmentation of kidney histologic structures across multiple stains and pathology laboratories. All data used for training and testing and a detailed online tutorial will be publicly available.

Introduction Childhood-onset nephrotic syndrome has a variable clinical course. Improved predictive markers of long-term outcomes in children with nephrotic syndrome are needed. This study tests the association between baseline urinary epidermal growth factor (uEGF) excretion and longitudinal kidney function in children with nephrotic syndrome. Methods The study evaluated 191 participants younger than 18 years enrolled in the Nephrotic Syndrome Study Network, including 118 with their first clinically indicated kidney biopsy (68 minimal change disease; 50 focal segmental glomerulosclerosis) and 73 with incident nephrotic syndrome without a biopsy. uEGF was measured at baseline for all participants and normalized by the urine creatinine (Cr) concentration. Renal epidermal growth factor (EGF) mRNA was measured in the tubular compartment microdissected from kidney biopsy cores from a subset of patients. Linear mixed models were used to test if baseline uEGF/Cr and EGF mRNA expression were associated with change in estimated glomerular filtration rate (eGFR) over time. Results Higher uEGF/Cr at baseline was associated with slower eGFR decline during follow-up (median follow-up = 30 months). Halving of uEGF/Cr was associated with a decrease in eGFR slope of 2.0 ml/min per 1.73 m2 per year (P < 0.001) adjusted for age, race, diagnosis, baseline eGFR and proteinuria, and APOL1 genotype. In the biopsied subgroup, uEGF/Cr was correlated with EGF mRNA expression (r = 0.74; P < 0.001), but uEGF/Cr was retained over mRNA expression as the stronger predictor of eGFR slope after multivariable adjustment (decrease in eGFR slope of 1.7 ml/min per 1.73 m2 per year per log2 decrease in uEGF/Cr; P < 0.001). Conclusion uEGF/Cr may be a useful noninvasive biomarker that can assist in predicting the long-term course of kidney function in children with incident nephrotic syndrome., Graphical abstract

BackgroundClassification of nephrotic syndrome relies on clinical presentation and descriptive patterns of injury on kidney biopsies. This approach does not reflect underlying disease biology, limiting the ability to predict progression or treatment response.MethodsSystems biology approaches were used to categorize patients with minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) based on kidney biopsy tissue transcriptomics across three cohorts and assessed association with clinical outcomes. Patient-level tissue pathway activation scores were generated using differential gene expression. Then, functional enrichment and non-invasive urine biomarker candidates were identified. Biomarkers were validated in kidney organoid models and single nucleus RNA-seq (snRNAseq) from kidney biopsies.ResultsTranscriptome-based categorization identified three subgroups of patients with shared molecular signatures across independent North American, European and African cohorts. One subgroup demonstrated worse longterm outcomes (HR 5.2, p = 0.001) which persisted after adjusting for diagnosis and clinical measures (HR 3.8, p = 0.035) at time of biopsy. This subgroup’s molecular profile was largely (48%) driven by tissue necrosis factor (TNF) activation and could be predicted based on levels of TNF pathway urinary biomarkers TIMP-1 and MCP-1 and clinical features (correlation 0.63, p ConclusionsMolecular profiling identified a patient subgroup within nephrotic syndrome with poor outcome and kidney TNF pathway activation. Clinical trials using non-invasive biomarkers of pathway activation to target therapies are currently being evaluated.Significance StatementMechanistic, targeted therapies are urgently needed for patients with nephrotic syndrome. The inability to target an individual’s specific disease mechanism using currently used diagnostic parameters leads to potential treatment failure and toxicity risk. Patients with focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) were grouped by kidney tissue transcriptional profiles and a subgroup associated with poor outcomes defined. The segregation of the poor outcome group was driven by tumor necrosis factor (TNF) pathway activation and could be identified by urine biomarkers, MCP1 and TIMP1. Based on these findings, clinical trials utilizing non-invasive biomarkers of pathway activation to target therapies, improve response rates and facilitate personalized treatment in nephrotic syndrome have been initiated.

Introduction There is limited information on effective disease monitoring for prompt interventions in childhood nephrotic syndrome. We examined the feasibility and effectiveness of a novel text messaging system (SMS) for disease monitoring in a multicenter, prospective study. Methods A total of 127 patients, Graphical abstract

Introductions: Kidney injury molecule-1 (KIM-1) and periostin (POSTN) are proximal and distal tubule injury biomarkers. We tested whether baseline urine KIM-1/Cr (uKIM-1/Cr) and/or uPOSTN/Cr correlated with disease severity or improved a remission prediction model. Methods: Baseline uKIM-1/Cr and uPOSTN/Cr were measured on spot urine samples from immunosuppression-free patients enrolled in Nephrotic Syndrome Study Network until December 15, 2014. Urine protein/Cr (UPCR) and albumin/Cr (UACR) were measured at baseline, 4 months, and until last follow-up. Glomerular and tubulointerstitial (TI) expression arrays were analyzed from a baseline research renal biopsy core collected during a clinically indicated biopsy. Renal diagnoses were centrally confirmed, sections scanned, and measured morphometrically. Correlations between baseline uKIM-1/Cr and uPOSTN/Cr and UPCR, UACR, histopathologic features, glomerular and TI KIM-1 and POSTN expression levels, and renal outcomes were assessed. Results: Baseline uKIM-1/cr correlated with UPCR and UACR and were associated with complete remission (CR) after adjustment for proteinuria, histopathologic diagnosis, and treatment. Baseline uKIM-1/Cr also correlated with degree of foot process effacement and acute tubular injury. Glomerular and TI KIM-1 expression levels correlated with UPCR and UACR. Higher TI KIM-1 expression levels correlated with interstitial fibrosis, tubular atrophy, and global glomerulosclerosis, while glomerular KIM-1 expression correlated with time to remission. Findings for POSTN were of lesser statistical strength. Discussion/Conclusion: Lower baseline uKIM-1/Cr values were associated with more rapid time to CR after adjusting for proteinuria, histopathologic diagnosis, and treatment. Increased TI KIM-1 expression levels in proteinuric states were associated with chronic morphological injury; lower glomerular expression levels were associated with a greater potential for proteinuria reversibility.

Autosomal recessive polycystic kidney disease (ARPKD) is a rare but potentially lethal genetic disorder typically characterized by diffuse renal microcysts. Clinical trials for patients with ARPKD are not currently possible due to the absence of sensitive measures of ARPKD kidney disease progression and/or therapeutic efficacy.In this study, animal and human magnetic resonance imaging (MRI) scanners were used to obtain quantitative kidney T1 and T2 relaxation time maps for both excised kidneys from bpk and wild-type (WT) mice as well as for a pediatric patient with ARPKD and a healthy adult volunteer.Mean kidney T1 and T2 relaxation times showed significant increases with age (p 0.05) as well as significant increases in comparison to WT mice (p 2 × 10These preclinical and initial clinical MRI studies suggest that renal T1 and T2 relaxometry may provide an additional outcome measure to assess cystic kidney disease progression in patients with ARPKD.A major roadblock for implementing clinical trials in patients with ARPKD is the absence of sensitive measures of ARPKD kidney disease progression and/or therapeutic efficacy. A clinical need exists to develop a safe and sensitive measure for kidney disease progression, and eventually therapeutic efficacy, for patients with ARPKD. Mean kidney T1 and T2 MRI relaxation times showed significant increases with age (p 0.05) as well as significant increases in comparison to WT mice (p 2 ×10

Background Understanding the relationship between clinical and patient-reported outcomes (PROs) will help support clinical care and future clinical trial design of novel therapies for focal segmental glomerulosclerosis (FSGS). Methods FSGS patients ≥8 years of age enrolled in the Nephrotic Syndrome Study Network completed Patient-Reported Outcomes Measurement Information System PRO measures of health-related quality of life (HRQoL) (children: global health, mobility, fatigue, pain interference, depression, anxiety, stress and peer relationships; adults: physical functioning, fatigue, pain interference, sleep impairment, mental health, depression, anxiety and social satisfaction) at baseline and during longitudinal follow-up for a maximum of 5 years. Linear mixed-effects models were used to determine which demographic, clinical and laboratory features were associated with PROs for each of the eight children and eight adults studied. Results There were 45 children and 114 adult FSGS patients enrolled that had at least one PRO assessment and 519 patient visits. Multivariable analyses among children found that edema was associated with global health (−7.6 points, P = 0.02) and mobility (−4.2, P = 0.02), the number of reported symptoms was associated with worse depression (−2.7 per symptom, P = 0.009) and anxiety (−2.3, P = 0.02) and the number of emergency room (ER) visits in the prior 6 months was associated with worse mobility (−2.8 per visit, P Conclusions PROs provide important information about HRQoL for persons with FSGS that is not captured solely by the examination of laboratory-based markers of disease. However, it is critical that instruments capture the patient experience and FSGS clinical trials may benefit from a disease-specific instrument more sensitive to within-patient changes.

Background and objectives The role of albuminuria as an indicator of progression has not been investigated in children with CKD in the absence of diabetes. Design, setting, participants, & measurements Children were enrolled from 49 centers of the CKD in Children study between January of 2005 and March of 2014. Cross-sectional multivariable linear regression (n=647) was used to examine the relationship between urine protein-to-creatinine (UP/C [milligrams per milligram]) and albumin-to-creatinine (ACR [milligrams per gram]) with eGFR (milliliters per minute per 1.73 m2). Parametric time-to-event analysis (n=751) was used to assess the association of UP/C, ACR, and urine nonalbumin-to-creatinine (Unon-alb/cr [milligrams per gram]) on the time to the composite endpoint of initiation of RRT or 50% decline in eGFR. Results The median follow-up time was 3.4 years and 202 individuals experienced the event. Participants with a UP/C≥0.2 mg/mg and ACR≥30 mg/g had a mean eGFR that was 16 ml/min per 1.73 m2 lower than those with a UP/C 2.0 mg/mg], RT=0.09 for ACR [>1333 mg/g], RT=0.07 for Unon-alb/cr [>715 mg/g]) levels to the lowest levels. A similar trend was seen when categories were created on the basis of clinically meaningful cutoff values of ACR ( 300 mg/g). Conclusions In children with CKD without diabetes, the utility of an initial UP/C, ACR, and Unon-alb/cr for characterizing progression is similar. Podcast This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2017_05_30_Schwartz.mp3

Background The process of developing patient management plans requires a series of clinical decision-making skills that can take years in practice to develop. For the inexperienced practitioner, providing a logical, systematic patient management framework may assist in clinical scenarios and accelerate their decision-making skill development. The purpose of this study was to assess whether a novel clinical management decision aid would improve the management decision-making of chiropractic students. Methods A prospective before and after study tracked chiropractic master degree students in their final year of study across a 10-week period from February–May, 2017. Case-based assessments were performed at baseline, after initial exposure to the decision aid, and after repeated exposure over the course of the semester. Outcome measures included the results from the 3 assessments, scored out of 20 by two markers using a standardised marking rubric, then averaged and converted to percentages; and 2 feedback questionnaires, given after initial exposure and at 10 weeks. Results A total of 75 students (44 males; 31 females) participated in the study. The mean score at baseline was 8.34/20 (41.7%) (95% CI: 7.98, 8.70; SD: 1.56) and after initial exposure was 9.52/20 (47.6%) (95% CI: 9.06, 9.98; SD: 2.02). The mean score after repeated exposure was 15.04/20 (75.2%) (95% CI: 14.46, 15.62; SD: 2.54). From baseline to initial exposure, there was a statistically significant absolute increase in mean score of 1.18/20 (5.9%) (95% CI: 0.6, 1.76; p p Conclusion Implementing a clinical management decision aid into the teaching curriculum helped to facilitate the ability of chiropractic students to develop patient management plans.

Objectives To determine the prevalence, age of onset, and risk factors for overweight and obesity in children with congenital heart disease (CHD). Study design Children with CHD who were seen at our institution from 1996 to 2017 were studied. Patients were full-time residents of the United States and were receiving all cardiac care at our institution. Patients were categorized by age and CHD diagnosis. The date of last normal weight for age and the date of first recorded weight in the range of overweight and obese were documented. Results Nine hundred sixty-eight patients with CHD were included. The prevalence of overweight and obesity was 31.5% and 16.4%, respectively. For patients who became overweight or obese, the last recorded normal weight was between 6 and 10 years of age. Electrophysiologic disease and older age were risk factors for obesity. Conclusions Children with CHD have an increasing risk of becoming overweight and obese in early childhood. This study provides important information and identifies critical period to implement preventative measures and counsel families about the risk of obesity in CHD.

Background and objectives This analysis from the Nephrotic Syndrome Study Network (NEPTUNE) assessed the phenotypic and pathology characteristics of proteinuric patients undergoing kidney biopsy and defined the frequency and factors associated with complete proteinuria remission (CRever). Design, setting, participants, & measurements We enrolled adults and children with proteinuria ≥0.5 g/d at the time of first clinically indicated renal biopsy at 21 sites in North America from April 2010 to June 2014 into a prospective cohort study. NEPTUNE central pathologists assigned participants to minimal-change disease (MCD), FSGS, membranous nephropathy, or other glomerulopathy cohorts. Outcome measures for this analysis were (1) CRever with urine protein-to-creatinine ratio (UPC)

SummaryA tissue transcriptome driven classification of nephrotic syndrome patients identified a high risk group of patients with TNF activation and established a non-invasive marker panel for pathway activity assessment paving the way towards precision medicine trials in NS.AbstractNephrotic syndrome from primary glomerular diseases can lead to chronic kidney disease (CKD) and/or end-stage renal disease (ESRD). Conventional diagnoses using a combination of clinical presentation and descriptive biopsy information do not accurately predict risk for progression in patients with nephrotic syndrome, which complicates disease management. To address this challenge, a transcriptome-driven approach was used to classify patients with minimal change disease and focal segmental glomerulosclerosis in the Nephrotic Syndrome Study Network (NEPTUNE). Transcriptome-based classification revealed a group of patients at risk for disease progression. High risk patients had a transcriptome profile consistent with TNF activation. Non-invasive urine biomarkers TIMP1 and CCL2 (MCP1), which are causally downstream of TNF, accurately predicted TNF activation in the NEPTUNE cohort setting the stage for patient stratification approaches and precision medicine in kidney disease.

Autosomal recessive polycystic kidney disease (ARPKD) is a potentially lethal multi-organ disease affecting both the kidneys and the liver. Unfortunately, there are currently no non-invasive methods to monitor liver disease progression in ARPKD patients, limiting the study of potential therapeutic interventions. Herein, we perform an initial investigation of T1 relaxation time as a potential imaging biomarker to quantitatively assess the two primary pathologic hallmarks of ARPKD liver disease: biliary dilatation and periportal fibrosis in the PCK rat model of ARPKD. T1 relaxation time results were obtained for five PCK rats at 3 months of age using a Look-Locker acquisition on a Bruker BioSpec 7.0 T MRI scanner. Six three-month-old Sprague-Dawley (SD) rats were also scanned as controls. All animals were euthanized after the three-month scans for histological and biochemical assessments of bile duct dilatation and hepatic fibrosis for comparison. PCK rats exhibited significantly increased liver T1 values (mean ± standard deviation = 935 ± 39 ms) compared with age-matched SD control rats (847 ± 26 ms, p = 0.01). One PCK rat exhibited severe cholangitis (mean T1 = 1413 ms), which occurs periodically in ARPKD patients. The observed increase in the in vivo liver T1 relaxation time correlated significantly with three histological and biochemical indicators of biliary dilatation and fibrosis: bile duct area percent (R = 0.85, p = 0.002), periportal fibrosis area percent (R = 0.82, p = 0.004), and hydroxyproline content (R = 0.76, p = 0.01). These results suggest that hepatic T1 relaxation time may provide a sensitive and non-invasive imaging biomarker to monitor ARPKD liver disease.

Primary (immotile) cilia are specialized organelles present on most cell types. Almost all of proteins associated with a broad spectrum of human cystic kidney diseases have been localized to the region in or around the cilia. Abnormal cilia structure and function have both been reported in animal models and human cystic kidneys. The goal of this review is to discuss current understanding of the mechanisms by which abnormal genes/proteins and cilia interact to potentially influence renal cystogenesis.Novel direct recording of cilia calcium levels/channel activity suggests that cilia form a calcium-mediated signaling microenvironment separate from the cytoplasm, which could provide a mechanism for cilia-specific downstream signaling. Genetic-based studies confirm that cilia are not required for cystogenesis, but modulate cystic kidney disease severity through a novel, undefined mechanism. Mechanisms by which both cilia-associated and noncilia-associated proteins can alter cilia structure/function have also been identified.Considerable progress has been made in defining the mechanisms by which abnormal genes and proteins affect cilia structure and function. However, the exact mechanisms by which these interactions cause renal cyst formation and progression of cystic kidney disease are still unknown.

High field, preclinical magnetic resonance imaging (MRI) scanners are now commonly used to quantitatively assess disease status and efficacy of novel therapies in a wide variety of rodent models. Unfortunately, conventional MRI methods are highly susceptible to respiratory and cardiac motion artifacts resulting in potentially inaccurate and misleading data. We have developed an initial preclinical, 7.0 T MRI implementation of the highly novel Magnetic Resonance Fingerprinting (MRF) methodology that has been previously described for clinical imaging applications. The MRF technology combines a priori variation in the MRI acquisition parameters with dictionary-based matching of acquired signal evolution profiles to simultaneously generate quantitative maps of T1 and T2 relaxation times and proton density. This preclinical MRF acquisition was constructed from a Fast Imaging with Steady-state Free Precession (FISP) MRI pulse sequence to acquire 600 MRF images with both evolving T1 and T2 weighting in approximately 30 minutes. This initial high field preclinical MRF investigation demonstrated reproducible and differentiated estimates of in vitro phantoms with different relaxation times. In vivo preclinical MRF results in mouse kidneys and brain tumor models demonstrated an inherent resistance to respiratory motion artifacts as well as sensitivity to known pathology. These results suggest that MRF methodology may offer the opportunity for quantification of numerous MRI parameters for a wide variety of preclinical imaging applications.

BackgroundAutosomal recessive polycystic kidney disease (ARPKD) is associated with significant mortality and morbidity, and currently, there are no disease-specific treatments available for ARPKD patients. One major limitation in establishing new therapies for ARPKD is a lack of sensitive measures of kidney disease progression. Magnetic resonance imaging (MRI) can provide multiple quantitative assessments of the disease.MethodsWe applied quantitative image analysis of high-resolution (noncontrast) T2-weighted MRI techniques to study cystic kidney disease progression and response to therapy in the PCK rat model of ARPKD.ResultsSerial imaging over a 2-month period demonstrated that renal cystic burden (RCB, %)=[total cyst volume (TCV)/total kidney volume (TKV) × 100], TCV, and, to a lesser extent, TKV detected cystic kidney disease progression, as well as the therapeutic effect of octreotide, a clinically available medication shown previously to slow both kidney and liver disease progression in this model. All three MRI measures correlated significantly with histologic measures of renal cystic area, although the correlation of RCB and TCV was stronger than that of TKV.ConclusionThese preclinical MRI results provide a basis for applying these quantitative MRI techniques in clinical studies, to stage and measure progression in human ARPKD kidney disease.

Autosomal-recessive polycystic kidney disease (ARPKD; MIM 263200) is a severe, typically early-onset form of cystic disease that primarily involves the kidneys and biliary tract. Phenotypic expression and age at presentation can be quite variable. 1 The incidence of ARPKD is 1 in 20000livebirths, 2 anditspleotropicmanifestationsarepotentially life-threatening. Optimal care requires proper surveillance to limit morbidity and mortality, knowledgeable approaches to diagnosis and treatment, and informed strategies to optimize quality of life. Clinical management therefore isideallydirected by multidisciplinary care teams consisting of perinatologists, neonatologists, nephrologists, hepatologists, geneticists, and behavioral specialists to coordinate patient care from the perinatal period to adulthood. In May 2013, an international team of 25 multidisciplinary specialists from the United States, Canada, Germany, and the United Kingdom convened in Washington, DC, to review the literature published from 1990 to 2013 and to develop recommendations for diagnosis, surveillance, and clinical management. Identification of the gene PKHD1, and the significant advances in perinatal care, imaging, medical management, and behavioral therapies during the past decade provide the foundational elements to define diagnostic criteria and establish clinical management guidelines as the first steps towards standardizing the clinical care for patients with ARPKD. The key issues discussed included recommendations regarding perinatal interventions, diagnostic criteria, genetic testing, management of renal and biliary-associated morbidities, and behavioral assessment. The meeting was funded by the National Institutes of Health and an educational grant from the Polycystic Kidney Disease Foundation. Here we summarize the discussions and provide an updated set of diagnostic, surveillance, and management recommendations for optimizing the pediatric care of patients with ARPKD. Specialist care of ARPKD-related complications, including dialysis, transplantation, and management of severe portal hypertension (HTN), will be addressed in a subsequent report. Given the paucity of information regarding targeted therapies in ARPKD, this topic was not addressed in this conference.

Arterial spin labeling (ASL) is a valuable non-contrast perfusion MRI technique with numerous clinical applications. Many previous ASL MRI studies have utilized either echo-planar imaging (EPI) or true fast imaging with steady-state free precession (true FISP) readouts, which are prone to off-resonance artifacts on high-field MRI scanners. We have developed a rapid ASL-FISP MRI acquisition for high-field preclinical MRI scanners providing perfusion-weighted images with little or no artifacts in less than 2 s. In this initial implementation, a flow-sensitive alternating inversion recovery (FAIR) ASL preparation was combined with a rapid, centrically encoded FISP readout. Validation studies on healthy C57/BL6 mice provided consistent estimation of in vivo mouse brain perfusion at 7 and 9.4 T (249 ± 38 and 241 ± 17 mL/min/100 g, respectively). The utility of this method was further demonstrated in the detection of significant perfusion deficits in a C57/BL6 mouse model of ischemic stroke. Reasonable kidney perfusion estimates were also obtained for a healthy C57/BL6 mouse exhibiting differential perfusion in the renal cortex and medulla. Overall, the ASL-FISP technique provides a rapid and quantitative in vivo assessment of tissue perfusion for high-field MRI scanners with minimal image artifacts. Copyright © 2014 John Wiley & Sons, Ltd.

The Nephrotic Syndrome Study Network (NEPTUNE) is a North American multicenter collaborative consortium established to develop a translational research infrastructure for nephrotic syndrome. This includes a longitudinal observational cohort study, a pilot and ancillary study program, a training program, and a patient contact registry. NEPTUNE will enroll 450 adults and children with minimal change disease, focal segmental glomerulosclerosis, and membranous nephropathy for detailed clinical, histopathological, and molecular phenotyping at the time of clinically indicated renal biopsy. Initial visits will include an extensive clinical history, physical examination, collection of urine, blood and renal tissue samples, and assessments of quality of life and patient-reported outcomes. Follow-up history, physical measures, urine and blood samples, and questionnaires will be obtained every 4 months in the first year and biannually, thereafter. Molecular profiles and gene expression data will be linked to phenotypic, genetic, and digitalized histological data for comprehensive analyses using systems biology approaches. Analytical strategies were designed to transform descriptive information to mechanistic disease classification for nephrotic syndrome and to identify clinical, histological, and genomic disease predictors. Thus, understanding the complexity of the disease pathogenesis will guide further investigation for targeted therapeutic strategies.

Case reports have linked childhood nephrotic syndrome to food sensitivity, including gluten. We report our experience with 8 children (6 boys, 2 girls; age at implementation of special diet 2–14 years) with difficult-to-manage nephrotic syndrome who were placed on a gluten-free diet for 3.4 ± 4.3 years (range, 0.6–14 years) and who had clinical improvement enabling reduction or discontinuation in steroid dosage.

Background The pathogenesis of progressive renal insufficiency in autosomal dominant polycystic kidney disease (ADPKD) is unclear. Evidence from experimental models of ADPKD suggests that elevated endothelin-1 (ET-1) drives cyst growth, renal fibrosis and loss of renal function, but whether ET-1 is elevated in humans with ADPKD is uncertain. Methods In a cross-sectional study of ADPKD we measured urinary ET-1, a surrogate for ET-1 in kidney cortex, in spot collections corrected for creatinine. The volume of each kidney was measured using MRI-based stereology. The relationship of urine ET-1 with MDRD eGFR and kidney volume was modeled by multiple linear regression with adjustment for clinical covariates. Results Patients with ADPKD were ages 18 to 53 with eGFRs (median, interquartile range) of 63.2 (43.5–80.2) ml/min/1.73 m2 and albumin/creatinine ratios (ACR) of 115.0 (7.5–58.5) μg/mg. Urine ET-1 was inversely associated with eGFR (r = −0.480, P

In recent decades, the antihyperglycemic biguanide metformin has been used extensively in the treatment of type 2 diabetes, despite continuing uncertainty over its direct target. In this article, using two independent approaches, we demonstrate that cellular actions of metformin are disrupted by interference with its metal-binding properties, which have been known for over a century but little studied by biologists. We demonstrate that copper sequestration opposes known actions of metformin not only on AMP-activated protein kinase (AMPK)-dependent signaling, but also on S6 protein phosphorylation. Biguanide/metal interactions are stabilized by extensive π-electron delocalization and by investigating analogs of metformin; we provide evidence that this intrinsic property enables biguanides to regulate AMPK, glucose production, gluconeogenic gene expression, mitochondrial respiration, and mitochondrial copper binding. In contrast, regulation of S6 phosphorylation is prevented only by direct modification of the metal-liganding groups of the biguanide structure, supporting recent data that AMPK and S6 phosphorylation are regulated independently by biguanides. Additional studies with pioglitazone suggest that mitochondrial copper is targeted by both of these clinically important drugs. Together, these results suggest that cellular effects of biguanides depend on their metal-binding properties. This link may illuminate a better understanding of the molecular mechanisms enabling antihyperglycemic drug action.

Diffusion MRI is a useful imaging technique with many clinical applications. Many diffusion MRI studies have utilized echo-planar imaging (EPI) acquisition techniques. In this study, we have developed a rapid diffusion-prepared fast imaging with steady-state free precession MRI acquisition for a preclinical 7T scanner providing diffusion-weighted images in less than 500 ms and diffusion tensor imaging assessments in ∼1 min with minimal image artifacts in comparison with EPI. Phantom apparent diffusion coefficient (ADC) and fractional anisotropy (FA) assessments obtained from the diffusion-prepared fast imaging with steady-state free precession (DP-FISP) acquisition resulted in good agreement with EPI and spin echo diffusion methods. The mean apparent diffusion coefficient was 2.0 × 10(-3) mm(2) /s, 1.90 × 10(-3) mm(2) /s, and 1.97 × 10(-3) mm(2) /s for DP-FISP, diffusion-weighted spin echo, and diffusion-weighted EPI, respectively. The mean fractional anisotropy was 0.073, 0.072, and 0.070 for diffusion-prepared fast imaging with steady-state free precession, diffusion-weighted spin echo, and diffusion-weighted EPI, respectively. Initial in vivo studies show reasonable ADC values in a normal mouse brain and polycystic rat kidneys.

Autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD) are important inherited kidney diseases with distinct clinical features and genetics. Although these diseases have classically been considered "adult" (ADPKD) or "infantile/pediatric" (ARPKD), it is now clear that both diseases can present in children and adults. ADPKD and ARPKD also share important pathophysiologic features, including cilia dysfunction. ADPKD is a systemic disease involving cysts in the kidneys and abdominal organs as well as abnormalities in the heart and vasculature. Although it typically presents in adults, ADPKD has been diagnosed in fetuses, infants, children, and adolescents. The majority of children diagnosed with ADPKD are asymptomatic. Those with symptoms typically present with hypertension or gross hematuria. Routine screening for renal cysts in asymptomatic children who have a parent with ADPKD is generally not recommended. ARPKD is a disorder confined to the kidneys (polycystic kidneys) and liver (a developmental biliary lesion called congenital hepatic fibrosis). Although most children with ARPKD present in infancy with large, echogenic kidneys, a subset present later in childhood and even adulthood, primarily with complications related to the liver disease. As more patients with ARPKD survive to adulthood, these liver complications are likely to become more prevalent.

Objectives Congenital hepatic fibrosis (CHF) is an important cause of morbidity and mortality in patients with autosomal recessive polycystic kidney disease (ARPKD). The pathogenesis of CHF remains undefined. Several recent studies suggest that the renin-angiotensin system (RAS) is an important mediator of progressive hepatic fibrosis through activation of profibrotic mediators, such as transforming growth factor-beta (TGF-beta). RAS activation has not previously been studied in patients with CHF or in animal models. The aim of the present study was to characterize RAS expression during the course of CHF in the PCK rat. Materials and methods Studies were conducted in the PCK rat, an orthologous ARPKD/CHF model, and age-matched normal control Sprague-Dawley rats. Expression of the RAS components, renin, angiotensinogen, angiotensin-converting enzyme (ACE), and angiotensin II type 1 receptor (AT1R), as well as the profibrotic mediator TGF-beta, was examined in cystic PCK and control rat livers at 2, 4, and 6 months of age by quantitative real-time polymerase chain reaction (qRT-PCR). Angiotensin II (ANG II) was examined by immunohistochemistry (IHC). Fibrosis was assessed by IHC using reticulin staining and Masson trichrome. Collagen content was determined by hydroxyproline analysis. Results Progressive fibrosis and increased hepatic collagen content occurred in PCK rats with age. In 4- and 6-month-old PCK rat livers, ACE gene expression was markedly increased, 8- and 17-fold, respectively, compared with age-matched control livers. Expression of the other RAS components, renin, angiotensinogen, and AT1R were not significantly different. IHC demonstrated prominent ANG II protein expression in periportal regions in PCK rats. In contrast, no expression was noted in control livers. TGF-beta expression was also increased in PCK rat livers with progressive disease. Conclusions The present study demonstrates, for the first time, RAS upregulation in an orthologous rat ARPKD/CHF model. Increases in ACE and ANG II, as well as the downstream target, the profibrotic mediator TGF-beta, suggest that RAS activation may be an important mediator of CHF disease progression. The findings also suggest that treatment with RAS inhibitors, specifically ACE inhibitors or AT1R blockers, could be therapeutic in slowing disease progression in CHF.

BACKGROUND: Chronic Kidney Disease (CKD) occurs in over one third of patients with Sickle Cell Disease (SCD) and can progress to end-stage renal disease. Unfortunately, current clinical assessments of kidney function are insensitive to early-stage CKD. Prior studies have shown that diffusion Magnetic Resonance Imaging (MRI) can sensitively detect regional renal microstructure changes associated with early-stage chronic kidney disease. However, previous MRI studies in sickle cell disease patients have been largely limited to detection of renal iron deposition assessed by T2* relaxometry. In this pilot imaging study, we compare MRI assessments of renal microstructure (diffusion) and iron deposition (T2*) in SCD patients and non-SCD control subjects. METHODS: Diffusion Tensor Imaging (DTI) and T2* relaxometry MRI data were obtained for pediatric (n=5) and adult (n=4) SCD patients as well as non-SCD control subjects (n=10) on a Siemens Espree 1.5T MRI scanner. A region-of-interest analysis was used to calculate mean medullary and cortical values for each MRI metric. MRI findings were also compared with clinical assessments of renal function and hemolysis. RESULTS: SCD patients showed a significant decrease in medullary Fractional Anisotropy (FA, p=0.0001) in comparison to non-SCD subjects indicative of microstructural alterations in the renal medulla of SCD patients. Cortical and medullary reductions in T2* (increased iron deposition, p = ≤ 0.0001) were also observed. Significant correlations were also observed between kidney T2* assessments and multiple measures of hemolysis. CONCLUSION: This is the first DTI MRI study of SCD patients to demonstrate reductions in medullary FA despite no overt chronic kidney disease (eGFR > 100 ml/min/1.73m2). These medullary FA changes are consistent with prior studies in patients with chronic kidney disease and suggest that DTI MRI can provide a useful measure of kidney injury to complement MRI assessments of iron deposition.

Background: Steroid resistant nephrotic syndrome (SRNS) is an important cause of chronic kidney disease (CKD) in children that often progresses to end-stage renal disease (ESRD). Calcineurin inhibitors (CNIs) have been shown to be effective in inducing short-term remission in some patients with SRNS. However, there are little data examining their long-term impact on ESRD progression rates. Methods: We performed a retrospective chart review of all patients treated for SRNS with CNIs at our institution from 1995-2013. Data collected including demographics, initial response to medical therapy, number of relapses, progression to ESRD, and treatment complications. Results: A total of 16 patients met inclusion criteria with a mean follow-up of 6.6 years (range 0.6-17.6 years). Histopathological diagnoses were focal segmental glomerulosclerosis (8), mesangial proliferative glomerulonephritis (4), IgM nephropathy (3), and minimal change disease (1). Three patients (18.8%) were unresponsive to CNIs while the remaining 13 (81.2%) achieved remission with CNI therapy. Six patients (37.5%) progressed to ESRD during the study period, three of whom did so after initially responding to CNI therapy. Renal survival rates were 87%, 71%, and 57% at 2 years, 5 years, and 10 years respectively. Non-Caucasian ethnicity was associated with progression to ESRD. Finally, a higher number of acute kidney injury episodes was associated with a lower final estimated glomerular filtration rate. Discussion: Despite the majority of SRNS patients initially responding to CNI therapy, a significant percentage still progressed to ESRD despite achieving short-term remission. Recurrent episodes of AKI may be associated with progression of CKD in SRNS patients with.

Autosomal recessive polycystic kidney disease (ARPKD) is an inherited disorder characterized by enlarged, cystic kidneys with progressive chronic kidney disease (CKD), systemic hypertension, and congenital hepatic fibrosis. Children with ARPKD can have early onset CKD and severe hypertension, both of which are known to have adverse neurocognitive effects. The objectives of this study were (1) to determine whether ARPKD patients have greater neurocognitive deficits compared to that of children with other causes of CKD, and (2) to examine the relative prevalence of hypertension in ARPKD, a known risk factor for neurocognitive dysfunction. We performed a cross-sectional, control-matched analysis of 22 ARPKD patients with mild-to-moderate CKD in the Chronic Kidney Disease in Children (CKiD) cohort study, compared with a control group of 44 children with other causes of CKD, matched based on glomerular filtration rate, age at study entry, and age at diagnosis. Children with ARPKD in this cohort had neurocognitive functioning comparable to children with other causes of CKD in domains of intellectual functioning, academic achievement, attention regulation, executive functioning, and behavior. Blood pressure parameters were similar between the two groups; however, ARPKD patients required a significantly greater number of antihypertensive medications to achieve similar BP levels. ARPKD patients are potentially at risk for neurocognitive dysfunction due to early onset CKD and more severe hypertension. However, this study of children with mild-to-moderate CKD in the CKiD cohort did not demonstrate increased risk in children with ARPKD compared to children with other causes of CKD. Further studies are needed to determine if these findings are applicable to children with more severe manifestations of ARPKD.

Background Renal disease is a known contributor to mortality in adults with sickle cell disease (SCD) and renal abnormalities are evident in childhood. Hyperfiltration (evidenced by elevated glomerular filtration rate, GFR) occurs in children with SCD early in disease. However, the incidence of low GFR ( 120 mL/min/1.73 m2 and 9 patients (18.8%) had eGFRs in the normal range. Eight patients (16.7%) had evidence of elevated blood pressures (pre-hypertension or hypertension). There was no correlation between eGFR and age, and no association of eGFR with acute chest or stroke risk. Conclusion In this SCD cohort, we identified abnormally low eGFR (suggestive of early CKD) in 8.3% of patients and elevated blood pressure in 16.7%. These findings are in contrast to other published studies that show primarily normal or elevated GFR and the absence of or minimal hypertension. These findings indicate that elevated blood pressure and decreased eGFR are not uncommon in children with SCD, and should be more rigorously studied.

The relationship between glucose and lipid metabolism has been of significant interest in understanding the pathogenesis of obesity-induced insulin resistance. To gain insight into this metabolic paradigm, we explored the potential interplay between cellular glucose flux and lipid-induced metabolic dysfunction within skeletal muscle. Here, we show that palmitate (PA)-induced insulin resistance and proinflammation in muscle cells, which is associated with reduced mitochondrial integrity and oxidative capacity, can be attenuated under conditions of glucose withdrawal or glycolytic inhibition using 2-deoxyglucose (2DG). Importantly, these glucopenic-driven improvements coincide with the preservation of mitochondrial function and are dependent on PA oxidation, which becomes markedly enhanced in the absence of glucose. Intriguingly, despite its ability to upregulate mitochondrial PA oxidation, glucose withdrawal did not attenuate PA-induced increases in total intramyocellular diacylglycerol and ceramide. Furthermore, consistent with our findings in cultured muscle cells, we also report enhanced insulin sensitivity and reduced proinflammatory tone in soleus muscle from obese Zucker rats fed a 2DG-supplemented diet. Notably, this improved metabolic status after 2DG dietary intervention is associated with markedly reduced plasma free fatty acids. Collectively, our data highlight the key role that mitochondrial substrate availability plays in lipid-induced metabolic dysregulation both in vitro and in vivo.

Background/Aims: Currently available clinical indicators of kidney disease lack the sensitivity and/or specificity to identify early-stage diabetic nephropathy (DN). Quantitative diffusion magnetic resonance imaging (MRI), specifically diffusion tensor imaging (DTI), has been used to quantify pathophysiologic changes in other organs but has not been well studied in kidney diseases, including DN. The goal of this pilot study was to examine differences in kidney DTI parameters in diabetic subjects versus healthy controls. Methods: 16 diabetic and 5 healthy control subjects were recruited for this institutional review board-approved/Health Insurance Portability and Accountability Act-compliant study. Kidneys were scanned using DTI to generate apparent diffusion coefficient (ADC) and fractional anisotropy (FA) data. Mean cortical and medullary ADC and FA values were calculated by selecting multiple regions of interest. Diabetics were stratified by estimated glomerular filtration rate (eGFR) into 2 groups: eGFR ≧60 (n = 10) and eGFR 2. Mean diffusion parameters and eGFRs were compared between these groups of diabetic subjects and healthy controls. Results: Medullary FA, ADC and cortical ADC values were significantly lower in diabetics with eGFR Conclusions: This pilot study suggests that changes in medullary DTI assessments may serve as indicators of early DN. Further studies are needed to determine if these findings could serve as biomarkers to identify diabetics at risk of DN progression.

Chemical exchange saturation transfer (CEST) and magnetization transfer techniques provide unique and potentially quantitative contrast mechanisms in multiple MRI applications. However, the in vivo implementation of these techniques has been limited by the relatively slow MRI acquisition techniques, especially on high-field MRI scanners. A new, rapid CEST-fast imaging with steady-state free precession technique was developed to provide sensitive CEST contrast in ∼20 sec. In this study at 7 T with in vitro bovine glycogen samples and initial in vivo results in a rat liver, the CEST-fast imaging with steady-state free precession technique was shown to provide equivalent CEST sensitivity in comparison to a conventional CEST-spin echo acquisition with a 50-fold reduction in acquisition time. The sensitivity of the CEST-fast imaging with steady-state free precession technique was also shown to be dependent on k-space encoding with centric k-space encoding providing a 30-40% increase in CEST sensitivity relative to linear encoding for 256 or more k-space lines. Overall, the CEST-fast imaging with steady-state free precession acquisition technique provides a rapid and sensitive imaging platform with the potential to provide quantitative CEST and magnetization transfer imaging data.

BACKGROUND: In patients with sickle cell disease (SCD), renal disease is strikingly high, with up to one third of adults developing chronic kidney disease. Renal disease is associated with considerable morbidity and mortality although it has not been as well studied as other SCD-related complications. Studies which could provide insight into clinically silent renal injury are limited. To date, no large studies of functional or structural renal changes have been published, particularly in the context of sickle cell crises. Magnetic Resonance Imaging (MRI) is safe and capable of providing quantitative assessments of disease without ionizing radiation. Clinically available MRI techniques have already been used to assess both acute and chronic kidney disease. This is the first study to evaluate these MRI techniques in SCD renal disease. OBJECTIVE: The objective of this pilot study was to evaluate the capability of quantitative MRI techniques to assess both structural changes and renal blood flow in patients with SCD. METHODS: Pediatric and adult patients were recruited to an IRB approved study from the Sickle Cell Anemia Centers at UH Rainbow Babies & Children’s Hospital and University Hospitals Case Medical Center. Six pediatric patients (age 12-18 years, 1 male, 5 female, eGFR 110-185 mL/min/1.73m2) have been recruited to date. Healthy controls were also recruited. Diffusion (DTI) and Arterial Spin Labeling (ASL) scans were performed to assess medullary microstructure and cortical perfusion (non-contrast), respectively. Apparent Diffusion Coefficient (ADC) and Fractional Anisotropy (FA) maps were calculated using established methods. Mean renal T2* was measured to assess iron burden. A Student’s t-test was performed to compare the mean renal DTI and ASL results between subjects and healthy controls. RESULTS: In the six pediatric subjects, medullary FA values were decreased, suggesting degradation of medullary microstructure. Both cortical ADC and medullary FA were significantly reduced, indicative of microstructural changes in SCD subjects compared to controls. ASL perfusion maps, likewise, showed reduced cortical perfusion for SCD subjects in comparison to controls. Preliminary differences in blood flow and microstructure were seen between SCD subjects on hydroxyurea (HU) and those not on HU. Analysis of the T2* data showed increased renal iron deposition that did not appear to correlate with serum ferritin. CONCLUSIONS: Our results suggest that quantitative diffusion and ASL MRI are sensitive to medullary microstructural and cortical blood flow changes in pediatric patients with SCD. Preliminarily, iron deposition in the kidney appears to relate to chronic hemolysis rather than transfusional iron. These sensitive techniques may be useful in assessing the impact of therapeutic interventions, such as HU, on renal function in children. There may also be utility in assessing the impact of acute hemolysis/sickling on renal microstructure and perfusion. Disclosures Piccone: Novartis Pharmaceuticals Cooperation: Speakers Bureau.

Transforming growth factor-alpha (TGF-alpha) is abnormally expressed in autosomal recessive polycystic kidney disease (ARPKD). Tumor necrosis factor-alpha converting enzyme (TACE), a metalloproteinase, mediates TGF-alpha processing. In this study, we sought to determine whether TGF-alpha was an absolute requirement for renal cystogenesis and whether its absence would modulate disease severity or related growth factors/receptors expression. Bpk heterozygotes were bred with TGF-alpha null mice to produce cystic and noncystic offspring with or without TGF-alpha. Assessments included kidney weight (KW), body weight (BW), blood urea nitrogen (BUN), and kidney and liver immunohistology. Western analysis assessed kidney expression of amphiregulin (AR), epidermal growth factor (EGF), heparin-binding EGF (HB-EGF), and their receptors, EGFR and ErbB4. A PCR-based methodology for genotyping bpk mice was also developed. No significant differences in KW, BW, KW/BW%, or BUN were seen in cystic mice with versus without TGF-alpha. Cystic kidney disease and liver disease histology were similar. AR, EGF, HB-EGF, EGFR, and ErbB4 were abnormally expressed to an equal degree in kidneys of mice with versus without TGF-alpha. Although previous data suggest a critical role of TGF-alpha in murine PKD, these data show that TGF-alpha is not required for renal cyst formation or kidney or liver disease progression. We speculate that the therapeutic effect of WTACE2 could have been due to effects on several TACE targets, including TGF-alpha, AR, and ErbB4, as well as metalloproteinases other than TACE.

EGF-related growth factors in the pathogenesis of murine ARPKD. Background Epidermal growth factor (EGF), transforming growth factor-α (TGF-α) and their receptor, EGFR, play key roles in polycystic kidney disease (PKD) pathogenesis. Renal expression of two related growth factors, amphiregulin and heparin-binding EGF, has not been examined previously in PKD. The aims of this study of murine autosomal-recessive polycystic kidney disease (ARPKD) were ( 1 ) to characterize amphiregulin and heparin-binding EGF expression in cystic versus normal kidneys and cells; and ( 2 ) to identify the functional effects of abnormal EGF-related growth factor expression. Methods Amphiregulin and heparin-binding-EGF expression were examined by immunohistology and Western blot of kidneys and conditionally-immortalized collecting tubule cells obtained from cystic bpk mice (a murine model of ARPKD) and normal littermates. EGF, TGF-α, amphiregulin, and heparin-binding EGF in vitro effects on cystic and control collecting tubule cells were assessed by cell proliferation, cyst fluid mitogenicity, and EGFR activation. Results By immunohistology, amphiregulin and heparin-binding EGF localized to apical and basolateral surfaces of proximal tubule cysts > normal proximal tubules. In cystic collecting tubules, heparin-binding EGF (but not amphiregulin) localized to both apical and basolateral surfaces; whereas in normal collecting tubules, amphiregulin and heparin-binding EGF localized to the basolateral surface only. Increased amphiregulin and heparin-binding EGF expression by Western blot was seen in cystic vs. normal kidneys and increased heparin-binding EGF (but not amphiregulin) expression was present in cystic collecting tubule cell lines vs. controls. EGF, TGF-α, amphiregulin, and heparin-binding EGF were all mitogenic to cystic > control collecting tubule cells. Immunoprecipitation of EGF and TGF-α reduced cyst fluid mitogenicity by almost 80%, whereas heparin-binding EGF and amphiregulin immunoprecipitations had minimal effects. Differential receptor activation was also seen: Heparin-binding EGF markedly activated EGFR (>EGF = TGF-α > amphiregulin), with a greater effect seen in cystic vs. control collecting tubule cells. Conclusion Multiple EGF-related growth factors are abnormally expressed in murine ARPKD and may have differential roles in disease pathogenesis. In particular, newly identified abnormalities in heparin-binding EGF expression in cystic kidneys and cells may have important implications for disease pathogenesis.

A novel inhibitor of tumor necrosis factor-α converting enzyme ameliorates polycystic kidney disease. Background Transforming growth factor-α (TGF-α) expression is abnormal in polycystic kidney disease. We previously demonstrated that blockade of the epidermal growth factor receptor (EGFR), the receptor for TGF-α, significantly slowed disease progression in the bpk murine model of autosomal-recessive kidney disease (ARPKD). In the present study, kidney TGF-α expression in this model is characterized, and the therapeutic potential of inhibiting TGF-α in ARPKD is examined using a novel inhibitor of tumor necrosis factor-α converting enzyme (TACE), the metalloproteinase that cleaves membrane-bound TGF-α to release the secreted ligand. Methods Immunohistochemistry (IH) and Western analysis were performed on kidneys from cystic bpk mice and noncystic littermates at postnatal days 7, 14, and 21. Bpk mice and normal controls were treated with WTACE2, a competitive inhibitor of TACE, from day 7 until day 21, and the effects on kidney histology and renal function were assessed. Results Increased TGF-α expression by IH was demonstrated in the proximal tubules (PT) at postnatal day 7 and collecting tubules (CT) by day 21. A parallel increase in kidney TGF-α expression was demonstrated by Western analysis. Treatment of cystic bpk mice with WTACE2 resulted in a 43% reduction in kidney weight to body weight ratio (11.2 vs. 19.7%), improved cystic index (3.2 vs. 4.8), reduced cystic CT to PT ratio (1.2 vs. 8), and a greater than 30% reduction in BUN and serum creatinine. Conclusions These findings support the pathophysiological role of the TGF-α/EGFR axis in murine ARPKD and demonstrate that inhibition of TGF-α secretion has therapeutic potential in PKD.

An extensive body of in vitro data implicates epithelial chloride secretion, mediated through cystic fibrosis transmembrane conductance regulator (CFTR) protein, in generating or maintaining fluid filled cysts in MDCK cells and in human autosomal dominant polycystic kidney disease (ADPKD). In contrast, few studies have addressed the pathophysiology of fluid secretion in cyst formation and enlargement in autosomal recessive polycystic kidney disease (ARPKD). Murine models of targeted disruptions or deletions of specific genes have created opportunities to examine the role of individual gene products in normal development and/or disease pathophysiology. The creation of a murine model of CF, which lacks functional CFTR protein, provides the opportunity to determine whether CFTR activity is required for renal cyst formation in vivo. Therefore, this study sought to determine whether renal cyst formation could be prevented by genetic complementation of the BPK murine model of ARPKD with the CFTR knockout mouse. The results of this study reveal that in animals that are homozygous for the cystic gene (bpk), the lack of functional CFTR protein on the apical surface of cystic epithelium does not provide protection against cyst growth and subsequent decline in renal function. Double mutant mice (bpk -/-; cftr -/-) developed massively enlarged kidneys and died, on average, 7 d earlier than cystic, non-CF mice (bpk -/-; cftr +/+/-). This suggests fundamental differences in the mechanisms of transtubular fluid secretion in animal models of ARPKD compared with ADPKD.