Irazabal, María V.

Background Height-adjusted total kidney volume (htTKV) measured by imaging defined as Mayo Imaging Class (MIC) is a validated prognostic measure for autosomal dominant polycystic kidney disease (ADPKD) in adults to predict and stratify disease progression. However, no stratification tool is currently available in pediatric ADPKD. Because magnetic resonance imaging and computed tomography in children are difficult, we propose a novel 3D ultrasound-based pediatric Leuven Imaging Classification to complement the MIC. Methods A prospective study cohort of 74 patients with genotyped ADPKD (37 female) was followed longitudinally with ultrasound, including 3D ultrasound, and they underwent in total 247 3D ultrasound assessments, with patients' median age (interquartile range [IQR]) at diagnosis of 3 (IQR, 0–9) years and at first 3D ultrasound evaluation of 10 (IQR, 5–14) years. First, data matching was done to the published MIC classification, followed by subsequent optimization of parameters and model type. Results PKD1 was confirmed in 70 patients (95%), PKD2 in three (4%), and glucosidase IIα unit only once (1%). Over these 247 evaluations, the median height was 143 (IQR, 122–166) cm and total kidney volume was 236 (IQR, 144–344) ml, leading to an htTKV of 161 (IQR, 117–208) ml/m. Applying the adult Mayo classification in children younger than 15 years strongly underestimated ADPKD severity, even with correction for height. We therefore optimized the model with our pediatric data and eventually validated it with data of young patients from Mayo Clinic and the Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease used to establish the MIC. Conclusions We proposed a five-level Leuven Imaging Classification ADPKD pediatric model as a novel classification tool on the basis of patients' age and 3D ultrasound-htTKV for reliable discrimination of childhood ADPKD severity.

Background: Scattered tubular-like cells (STCs) are dedifferentiated renal tubular cells endowed with progenitor-like characteristics to repair injured parenchymal cells. STCs may be damaged and rendered ineffective by renal artery stenosis (RAS), but the underlying processes remain unclear. We hypothesized that RAS alters the epigenetic landscape on DNA and the ensuing gene transcriptional profile of swine STCs. Methods: CD24+/CD133+ STCs were isolated from pig kidneys after 10 weeks of RAS or sham (n = 3 each) and their whole 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) profiles were examined by 5mC and 5hmC immunoprecipitation sequencing (MeDIP-/hMeDIP-seq, respectively). A subsequent integrated (MeDIP/hMeDIP-seq/mRNA-seq) analysis was performed by comparing all online available gene sets using Gene Set Enrichment Analysis. Apoptosis, proteolysis, and mitochondrial structure and function were subsequently evaluated in vitro. Results: Differential expression (DE) analysis revealed 239 genes with higher and 236 with lower 5mC levels and 275 genes with higher and 315 with lower 5hmC levels in RAS-STCs compared to Normal-STCs (fold change ≥1.4 or ≤0.7, p ≤ 0.05). Integrated MeDIP-/hMeDIP-seq/mRNA-seq analysis identified several overlapping (DE-5mC/mRNA and DE-5hmC/mRNA levels) genes primarily implicated in apoptosis, proteolysis, and mitochondrial functions. Furthermore, RAS-STCs exhibited decreased apoptosis, mitochondrial matrix density, and ATP production, and increased intracellular amino acid concentration and ubiquitin expression. Conclusions: Renal ischemia induces epigenetic changes in apoptosis-, proteolysis-, and mitochondria-related genes, which correlate with alterations in the transcriptomic profile and corresponding function of swine STCs. These observations may contribute to developing novel targeted interventions to preserve the reparative potency of STCs in renal disease.

Abstract Chronic kidney disease (CKD) is a public health concern that affects over 200 million people worldwide and is associated with a tremendous economic burden. Therefore, deciphering the mechanisms underpinning CKD is crucial to decelerate its progression towards end-stage renal disease (ESRD). Renal tubular cells are populated with a high number of mitochondria, which produce cellular energy and modulate several important cellular processes, including generation of reactive oxygen species (ROS), calcium homeostasis, proliferation, and apoptosis. Over the past few years, increasing evidence has implicated renal mitochondrial damage in the pathogenesis of common etiologies of CKD, such as diabetes, hypertension, metabolic syndrome (MetS), chronic renal ischemia, and polycystic kidney disease (PKD). However, most compelling evidence is based on preclinical studies because renal biopsies are not routinely performed in many patients with CKD. Previous studies have shown that urinary mitochondrial DNA (mtDNA) copy numbers may serve as non-invasive biomarkers of renal mitochondrial dysfunction. Emerging data also suggest that CKD is associated with altered expression of mitochondria-related microRNAs (mitomiRs), which localize in mitochondria and regulate the expression of mtDNA and nucleus-encoded mitochondrial genes. This review summarizes relevant evidence regarding the involvement of renal mitochondrial injury and dysfunction in frequent forms of CKD. We further provide an overview of non-invasive biomarkers and potential mechanisms of renal mitochondrial damage, especially focusing on mtDNA and mitomiRs.

Polycystic kidney disease (PKD) is the most common monogenic kidney disorder and an important cause of end stage renal disease. Vascular abnormalities are the most important non‐cystic complication and contribute to renal disease progression. Homocysteine (Hcy)‐mediated endothelial dysfunction (ED) and oxidative stress are evident early on, but the underlying mechanisms remain unknown. We hypothesized that abnormalities in Hcy metabolism are responsible for the increased levels, leading to Hcy‐induced ED from early stages of PKD. Methods We investigated the Hcy metabolic pathway (transulfuration/remethylation fig. 1) and downstream effects ‐main sources of renal tubular (RT) and endothelial cell (EC) reactive oxygen species (ROS), NADPH oxidase 4, (NOX4) and mitochondria‐ in 4‐week‐old PCK and Sprague‐Dawley (SD) control rats (n=12 each). Kidneys were harvested, frozen in liquid nitrogen, or preserved in formalin for metabolomics and ex‐vivo studies. Twenty‐four‐hour urine and terminal blood samples were collected for metabolite analysis and chemistries. Plasma folic acid, vitamin B12, and Hcy were determined by ELISA. Hcy pathway metabolites (betaine, dimethylglycine) were determined by 1 HNMR. Endothelial NO (eNOS) and oxidative stress were assessed by double immunofluorescence staining for CD31/eNOS and CD31/NOX4, respectively. RT and EC mitochondrial structure was assessed by electron microscopy. Results Serum creatinine and BUN remained unchanged, yet kidney weight/body weight ratio were increased in PCK. eNOS immunoreactivity was lower in PCK vs SD. Plasma Hcy and urine excretion of methyl donor betaine were elevated in PCK, and Hcy positively correlated with urine betaine. Plasma betaine was similar between the groups, but its tissue concentration was lower in PCK, which may lead to betaine insufficiency, impaired betaine dependent remethylation, and hyperhomocysteinemia. Contrarily, tissue glutathione concentration was higher in PCK vs SD, and plasma folate and vitamin B12 were similar, arguing against a defect in the transsulfuration or folate‐dependent remethylation pathways. RT NOX4 expression and immunoreactivity were increased in PCK compared to SD, in association with renal oxidative stress. PCK had increased number of CD31/NOX4 positive cells in peritubular capillaries, indicating increased EC ROS production. Collecting duct and EC mitochondria were swollen and showed cristae remodeling. Conclusion In PKD, early elevation in Hcy is likely related to betaine insufficiency and impaired betaine‐dependent remethylation may be responsible for the early elevation of Hcy. NOX4 and mitochondria abnormalities may be important contributors to oxidative stress and disease severity. Our data suggests these may not only be early vascular disease markers, but also play an important pathogenic role in vascular complications associated with PKD, and contribute to renal disease progression. Support or Funding Information R25‐DK101405, NIDDK P30 DK090728, NIDDK P30 DK 106912 This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

Significance Statement Efficacy of rituximab (RTX) in ANCA-associated vasculitis (AAV) in patients with severe renal involvement (eGFR<30 ml/min per 1.73 m 2 ) has not been addressed in clinical trials. This observational study did not find statistically significant differences between RTX and cyclophosphamide (CYC) for remission-induction therapy or any apparent benefit from the addition of plasma exchange (PLEX) to standard remission-induction therapy for patients with AAV and severe renal involvement. Although our analyses suggest that the benefits and risks of these therapeutic choices (RTX versus CYC with and without PLEX) are balanced, a randomized, controlled trial is needed to confirm these findings. Background Treatment of patients with ANCA-associated vasculitis (AAV) and severe renal involvement is not established. We describe outcomes in response to rituximab (RTX) versus cyclophosphamide (CYC) and plasma exchange (PLEX). Methods A retrospective cohort study of MPO- or PR3-ANCA–positive patients with AAV (MPA and GPA) and severe kidney disease (eGFR <30 ml/min per 1.73 m 2 ). Remission, relapse, ESKD and death after remission-induction with CYC or RTX, with or without the use of PLEX, were compared. Results Of 467 patients with active renal involvement, 251 had severe kidney disease. Patients received CYC ( n =161) or RTX ( n =64) for remission-induction, and 51 were also treated with PLEX. Predictors for ESKD and/or death at 18 months were eGFR <15 ml/min per 1.73 m 2 at diagnosis (IRR 3.09 [95% CI 1.49 to 6.40], P =0.002), renal recovery (IRR 0.27 [95% CI 0.12 to 0.64], P =0.003) and renal remission at 6 months (IRR 0.40 [95% CI 0.18 to 0.90], P =0.027). RTX was comparable to CYC in remission-induction (BVAS/WG=0) at 6 months (IRR 1.37 [95% CI 0.91 to 2.08], P =0.132). Addition of PLEX showed no benefit on remission-induction at 6 months (IRR 0.73 [95% CI 0.44 to 1.22], P =0.230), the rate of ESKD and/or death at 18 months (IRR 1.05 [95% CI 0.51 to 2.18], P =0.891), progression to ESKD (IRR 1.06 [95% CI 0.50 to 2.25], P =0.887), and survival at 24 months (IRR 0.54 [95% CI 0.16 to 1.85], P =0.330). Conclusions The apparent benefits and risks of using CYC or RTX for the treatment of patients with AAV and severe kidney disease are balanced. The addition of PLEX to standard remission-induction therapy showed no benefit in our cohort. A randomized controlled trial is the only satisfactory means to evaluate efficacy of remission-induction treatments in AAV with severe renal involvement.

Significance Statement Accurate prediction of risk for disease progression is crucial for clinical management of autosomal dominant polycystic kidney disease (ADPKD). The Mayo imaging classification of ADPKD uses height-adjusted total kidney volume (htTKV) and age to identify patients at highest risk. Because the current Mayo classification applies only to patients with typical diffuse cystic disease (class 1) and poorly predicts eGFR decline for the remaining 5%–10% of patients with atypical morphology (class 2), imaging-based risk modeling remains unresolved. The authors report an expanded imaging classification model in which use of a recalculated htTKV value that excludes prominent exophytic cysts improved prediction for eGFR trajectory. Using a recalculated htTKV may allow inclusion of class 2 patients in the Mayo classification of ADPKD and reclassification of class 1 patients with prominent exophytic cysts. Background The Mayo Clinic imaging classification of autosomal dominant polycystic kidney disease (ADPKD) uses height-adjusted total kidney volume (htTKV) and age to identify patients at highest risk for disease progression. However, this classification applies only to patients with typical diffuse cystic disease (class 1). Because htTKV poorly predicts eGFR decline for the 5%–10% of patients with atypical morphology (class 2), imaging-based risk modeling remains unresolved. Methods Of 558 adults with ADPKD in the HALT-A study, we identified 25 patients of class 2A with prominent exophytic cysts (class 2Ae) and 43 patients of class 1 with prominent exophytic cysts; we recalculated their htTKVs to exclude exophytic cysts. Using original and recalculated htTKVs in association with imaging classification in logistic and mixed linear models, we compared predictions for developing CKD stage 3 and for eGFR trajectory. Results Using recalculated htTKVs increased specificity for developing CKD stage 3 in all participants from 82.6% to 84.2% after adjustment for baseline age, eGFR, BMI, sex, and race. The predicted proportion of class 2Ae patients developing CKD stage 3 using a cutoff of 0.5 for predicting case status was better calibrated to the observed value of 13.0% with recalculated htTKVs (45.5%) versus original htTKVs (63.6%). Using recalculated htTKVs reduced the mean paired difference between predicted and observed eGFR from 17.6 (using original htTKVs) to 4.0 ml/min per 1.73 m 2 for class 2Ae, and from −1.7 (using original htTKVs) to 0.1 ml/min per 1.73 m 2 for class 1. Conclusions Use of a recalculated htTKV measure that excludes prominent exophytic cysts facilitates inclusion of class 2 patients and reclassification of class 1 patients in the Mayo classification model.

Chronic kidney disease (CKD) remains a worldwide public health problem associated with serious complications and increased mortality rates. Accumulating evidence indicates that elevated intracellular levels of reactive oxygen species (ROS) play a major role in the pathogenesis of CKD. Increased intracellular levels of ROS can lead to oxidation of lipids, DNA, and proteins, contributing to cellular damage. On the other hand, ROS are also important secondary messengers in cellular signaling. Consequently, normal kidney cell function relies on the “right” amount of ROS. Mitochondria and NADPH oxidases represent major sources of ROS in the kidney, but renal antioxidant systems, such as superoxide dismutase, catalase, or glutathione peroxidase counterbalance ROS-mediated injury. This review discusses the main sources of ROS and antioxidant systems in the kidney, and redox signaling pathways leading to inflammation and fibrosis, which result in abnormal kidney function and CKD progression. We further discuss the important role of the nuclear factor erythroid 2-related factor 2 (Nrf2) in regulating antioxidant responses, and other mechanisms of redox signaling.

Introduction Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive development and enlargement of bilateral renal cysts, and the majority of renal complications including organ failure arise mainly as a consequence of the cystic burden along with associated inflammation and fibrosis. Abnormal epithelial cell proliferation, along with the inability to maintain planar cell polarity, underlies cyst formation and enlargement. Therefore, processes that stimulate renal cell proliferation have the potential to generate the cystic phenotype. Interestingly, an increased nuclear factor (erythroid‐derived 2)‐like 2 (Nrf2) response has been shown to direct cancer cells into an anabolic mode that favors cellular proliferation, and has been associated with renal cyst formation in experimental and human fumarate hydratase deficiency. However, the Nrf2 response has not been described in ADPKD. We hypothesized that early ADPKD presents with an elevation in the Nrf2 response that favors cellular proliferation and contributes to cystogenesis. Methods We sought to longitudinally characterize the Nrf2 response and association with cystogenesis and fibrosis in a slow progressive mouse model of ADPKD ( Pkd1 RC/RC ) and its wildtype controls (n=6 males, 6 females per group). Urine and plasma samples were collected at 30, 60, 120, and 180 days for chemistries and metabolic profiles, and cystic index (CI), and total kidney volume (TKV) were determined from abdominal MRI. Nrf2 levels and related response enzymes, as well as cell proliferation and fibrosis were analyzed using western‐blots, immunofluorescence, and assay kits. Results At 30 days, Pkd1 RC/RC mice presented increased CI (Figure ) and TKV/BW. However, serum creatinine and fibrotic markers were not different compared to controls. Pkd1 RC/RC mice exhibited elevated Nrf2 expression and immunoreactivity early on that declined as ADPKD progressed from 30 to 180 days (Figure ) and correlated directly with cell proliferation (R 2 =0.693, p<0.05) and inversely with fibrotic markers (R 2 =0.672, p<0.05). Conclusions Our study shows longitudinal changes in the Nrf2 response in Pkd1 RC/RC mice that are associated with cystogenesis early on and renal fibrosis at later stages of the disease. These findings have significant implications for the treatment of human ADPKD, and suggest that Nrf2 modulators might represent an advantageous intervention for the disease Support or Funding Information NIDDK R21 DK118391, R25‐DK101405, NIDDK P30 DK090728 A) Representative H&E‐stained kidney mid‐sections from Wild Type (WT) and Pkd1 RC/RC mice at 1 month. Pkd1 RC/RC mice presented increased cystic index (CI) from early stages of the disease. CI is calculated as % of cyst area within the total kidney section. B) Longitudinal levels of Nrf2 activation in WT and Pkd1 RC/RC mice. Pkd1 RC/RC mice exhibited elevated Nrf2 levels early on that declined as the disease progressed. Nrf2 activation is calculated from nuclear extracts by colorimetric assay. Figure 1

Vascular abnormalities are the most important non-cystic complications in Polycystic Kidney Disease (PKD) and contribute to renal disease progression. Endothelial dysfunction and oxidative stress are evident in patients with ADPKD, preserved renal function, and controlled hypertension. The underlying biological mechanisms remain unknown. We hypothesized that in early ADPKD, the reactive oxygen species (ROS)-producing nicotinamide adenine dinucleotide phosphate hydrogen (NAD(P)H)-oxidase complex-4 (NOX4), a major source of ROS in renal tubular epithelial cells (TECs) and endothelial cells (ECs), induces EC mitochondrial abnormalities, contributing to endothelial dysfunction, vascular abnormalities, and renal disease progression. Renal oxidative stress, mitochondrial morphology (electron microscopy), and NOX4 expression were assessed in 4- and 12-week-old PCK and Sprague-Dawley (wild-type, WT) control rats (n = 8 males and 8 females each). Endothelial function was assessed by renal expression of endothelial nitric oxide synthase (eNOS). Peritubular capillaries were counted in hematoxylin–eosin (H&E)-stained slides and correlated with the cystic index. The enlarged cystic kidneys of PCK rats exhibited significant accumulation of 8-hydroxyguanosine (8-OHdG) as early as 4 weeks of age, which became more pronounced at 12 weeks. Mitochondria of TECs lining cysts and ECs exhibited loss of cristae but remained preserved in non-cystic TECs. Renal expression of NOX4 was upregulated in TECs and ECs of PCK rats at 4 weeks of age and further increased at 12 weeks. Contrarily, eNOS immunoreactivity was lower in PCK vs. WT rats at 4 weeks and further decreased at 12 weeks. The peritubular capillary index was lower in PCK vs. WT rats at 12 weeks and correlated inversely with the cystic index. Early PKD is associated with NOX4-induced oxidative stress and mitochondrial abnormalities predominantly in ECs and TECs lining cysts. Endothelial dysfunction precedes capillary loss, and the latter correlates with worsening of renal disease. These observations position NOX4 and EC mitochondria as potential therapeutic targets in PKD.

Abstract Abstract 3468 Engraftment syndrome (ES) is a complication of hematopoietic stem cell transplantation classically characterized by fever, rash, diarrhea, weight gain and non-cardiogenic pulmonary edema. Renal failure has been observed but is not considered to be a major part of the syndrome. We have noted that acute renal failure (ARF) is common around the time of leukocyte engraftment in light chain amyloidosis (AL) patients after autologous stem cell transplant (ASCT). We suspect this is due to ES and this retrospective review was conducted to further study this entity. Data were collected from 377 AL patients who underwent ASCT from 7/1997 to 10/2009. Patients who experienced an elevation of serum creatinine (Scr) > 0.5 mg/dl within 4 days of leukocyte engraftment were selected. Patients who carried a diagnosis of ES were also included regardless of Scr elevation. Nephrotoxic insults were reviewed. Vitals were collected. Forty-one patients met criteria. Four patients were found not to have ES, 2 sepsis, 1 allergic interstitial nephritis (AIN), 1 acute cellular rejection. ES was noted in 37 (9.8%) patients, 2 presented with mainly pulmonary ES and 8 had both pulmonary and renal involvement. The degree of renal failure varied from mild and self-limited to severe and requiring dialysis. The renal failure is usually preceded by fever, rash, increasing edema, relative hypotension and low urine sodium (Figure 1). Treatment with glucocorticoids (60 mg/d) was successful in reversing the renal failure in most patients but those with pulmonary involvement required higher doses. Our study showed that ES presents more commonly with renal failure than pulmonary involvement in AL patients. Further complications may be prevented by early treatment with corticosteroids once infection is ruled out. Dosing depends on concurrent pulmonary findings. Distinguishing ES with AIN is difficult as presentations are similar but AIN will continue until the offending drug is removed while ES generally responds quickly to steroids alone. Figure 1. Figure 1. Disclosures: Dispenzieri: Celgene: Honoraria, Research Funding; Binding Site: Honoraria. Kumar:Celgene: Consultancy, Research Funding; Millennium: Research Funding; Merck: Consultancy, Research Funding; Novartis: Research Funding; Genzyme: Consultancy, Research Funding; Cephalon: Research Funding.