Polyploid tubular cells initiate a TGF-ß1 controlled loop that sustains polyploidization and fibrosis after acute kidney injury.

Polyploidization of tubular cells (TC) is triggered by acute kidney injury (AKI) to allow survival in the early phase after AKI, but in the long run promotes fibrosis and AKI-chronic kidney disease (CKD) transition. The molecular mechanism governing the link between polyploid TC and kidney fibrosis remains to be clarified. In this study, we demonstrate that immediately after AKI, expression of cell cycle markers mostly identifies a population of DNA-damaged polyploid TC. Using transgenic mouse models and single-cell RNA sequencing we show that, unlike diploid TC, polyploid TC accumulate DNA damage and survive, eventually resting in the G1 phase of the cell cycle. In vivo and in vitro single-cell RNA sequencing along with sorting of polyploid TC shows that these cells acquire a profibrotic phenotype culminating in transforming growth factor (TGF)-ß1 expression and that TGF-ß1 directly promotes polyploidization. This demonstrates that TC polyploidization is a self-sustained mechanism. Interactome analysis by single-cell RNA sequencing revealed that TGF-ß1 signaling fosters a reciprocal activation loop among polyploid TC, macrophages, and fibroblasts to sustain kidney fibrosis and promote CKD progression. Collectively, this study contributes to the ongoing revision of the paradigm of kidney tubule response to AKI, supporting the existence of a tubulointerstitial cross talk mediated by TGF-ß1 signaling produced by polyploid TC following DNA damage.NEW & NOTEWORTHY Polyploidization in tubular epithelial cells has been neglected until recently. Here, we showed that polyploidization is a self-sustained mechanism that plays an important role during chronic kidney disease development, proving the existence of a cross talk between infiltrating cells and polyploid tubular cells. This study contributes to the ongoing revision of kidney adaptation to injury, posing polyploid tubular cells at the center of the process.

A Clinical Workflow for Cost-Saving High-Rate Diagnosis of Genetic Kidney Diseases.

SIGNIFICANCE STATEMENT: To optimize the diagnosis of genetic kidney disorders in a cost-effective manner, we developed a workflow based on referral criteria for in-person evaluation at a tertiary center, whole-exome sequencing, reverse phenotyping, and multidisciplinary board analysis. This workflow reached a diagnostic rate of 67%, with 48% confirming and 19% modifying the suspected clinical diagnosis. We obtained a genetic diagnosis in 64% of children and 70% of adults. A modeled cost analysis demonstrated that early genetic testing saves 20% of costs per patient. Real cost analysis on a representative sample of 66 patients demonstrated an actual cost reduction of 41%. This workflow demonstrates feasibility, performance, and economic effect for the diagnosis of genetic kidney diseases in a real-world setting. BACKGROUND: Whole-exome sequencing (WES) increases the diagnostic rate of genetic kidney disorders, but accessibility, interpretation of results, and costs limit use in daily practice. METHODS: Univariable analysis of a historical cohort of 392 patients who underwent WES for kidney diseases showed that resistance to treatments, familial history of kidney disease, extrarenal involvement, congenital abnormalities of the kidney and urinary tract and CKD stage ≥G2, two or more cysts per kidney on ultrasound, persistent hyperechoic kidneys or nephrocalcinosis on ultrasound, and persistent metabolic abnormalities were most predictive for genetic diagnosis. We prospectively applied these criteria to select patients in a network of nephrology centers, followed by centralized genetic diagnosis by WES, reverse phenotyping, and multidisciplinary board discussion. RESULTS: We applied this multistep workflow to 476 patients with eight clinical categories (podocytopathies, collagenopathies, CKD of unknown origin, tubulopathies, ciliopathies, congenital anomalies of the kidney and urinary tract, syndromic CKD, metabolic kidney disorders), obtaining genetic diagnosis for 319 of 476 patients (67.0%) (95% in 21 patients with disease onset during the fetal period or at birth, 64% in 298 pediatric patients, and 70% in 156 adult patients). The suspected clinical diagnosis was confirmed in 48% of the 476 patients and modified in 19%. A modeled cost analysis showed that application of this workflow saved 20% of costs per patient when performed at the beginning of the diagnostic process. Real cost analysis of 66 patients randomly selected from all categories showed actual cost reduction of 41%. CONCLUSIONS: A diagnostic workflow for genetic kidney diseases that includes WES is cost-saving, especially if implemented early, and is feasible in a real-world setting.

Defining diagnostic trajectories in patients with podocytopathies.

Podocytopathies are glomerular disorders in which podocyte injury drives proteinuria and progressive kidney disease. They encompass a broad spectrum of aetiologies, resulting in pathological pictures of minimal-changes, focal segmental glomerulosclerosis, diffuse mesangial sclerosis or collapsing glomerulopathy. Despite improvement in classifying podocytopathies as a distinct group of disorders, the histological definition fails to capture the relevant biological heterogeneity underlying each case, manifesting as extensive variability in disease progression and response to therapies. Increasing evidence suggests that podocytopathies can result from a single causative factor or a combination of multiple genetic and/or environmental risk factors with different relative contributions, identifying complex physiopathological mechanisms. Consequently, the diagnosis can still be challenging. In recent years, significant advances in genetic, microscopy and biological techniques revolutionized our understanding of the molecular mechanisms underlying podocytopathies, pushing nephrologists to integrate innovative information with more conventional data obtained from kidney biopsy in the diagnostic workflow. In this review, we will summarize current approaches in the diagnosis of podocytopathies, focusing on strategies aimed at elucidating the aetiology underlying the histological picture. We will provide several examples of an integrative view of traditional concepts and new data in patients with suspected podocytopathies, along with a perspective on how a reclassification could help to improve not only diagnostic pathways and therapeutic strategies, but also the management of disease recurrence after kidney transplantation. In the future, the advantages of precision medicine will probably allow diagnostic trajectories to be increasingly focused, maximizing therapeutic results and long-term prognosis.

Differentiation of crescent-forming kidney progenitor cells into podocytes attenuates severe glomerulonephritis in mice.

Crescentic glomerulonephritis is characterized by vascular necrosis and parietal epithelial cell hyperplasia in the space surrounding the glomerulus, resulting in the formation of crescents. Little is known about the molecular mechanisms driving this process. Inducing crescentic glomerulonephritis in two Pax2Cre reporter mouse models revealed that crescents derive from clonal expansion of single immature parietal epithelial cells. Preemptive and delayed histone deacetylase inhibition with panobinostat, a drug used to treat hematopoietic stem cell disorders, attenuated crescentic glomerulonephritis with recovery of kidney function in the two mouse models. Three-dimensional confocal microscopy and stimulated emission depletion superresolution imaging of mouse glomeruli showed that, in addition to exerting an anti-inflammatory and immunosuppressive effect, panobinostat induced differentiation of an immature hyperplastic parietal epithelial cell subset into podocytes, thereby restoring the glomerular filtration barrier. Single-cell RNA sequencing of human renal progenitor cells in vitro identified an immature stratifin-positive cell subset and revealed that expansion of this stratifin-expressing progenitor cell subset was associated with a poor outcome in human crescentic glomerulonephritis. Treatment of human parietal epithelial cells in vitro with panobinostat attenuated stratifin expression in renal progenitor cells, reduced their proliferation, and promoted their differentiation into podocytes. These results offer mechanistic insights into the formation of glomerular crescents and demonstrate that selective targeting of renal progenitor cells can attenuate crescent formation and the deterioration of kidney function in crescentic glomerulonephritis in mice.

Clinical and Genetic Characterization of Patients with Bartter and Gitelman Syndrome.

Bartter (BS) and Gitelman (GS) syndrome are autosomal recessive inherited tubulopathies, whose clinical diagnosis can be challenging, due to rarity and phenotypic overlap. Genotype-phenotype correlations have important implications in defining kidney and global outcomes. The aim of our study was to assess the diagnostic rate of whole-exome sequencing (WES) coupled with a bioinformatic analysis of copy number variations in a population of 63 patients with BS and GS from a single institution, and to explore genotype-phenotype correlations. We obtained a diagnostic yield of 86% (54/63 patients), allowing disease reclassification in about 14% of patients. Although some clinical and laboratory features were more commonly reported in patients with BS or GS, a significant overlap does exist, and age at onset, preterm birth, gestational age and nephro-calcinosis are frequently misleading. Finally, chronic kidney disease (CKD) occurs in about 30% of patients with BS or GS, suggesting that the long-term prognosis can be unfavorable. In our cohort the features associated with CKD were lower gestational age at birth and a molecular diagnosis of BS, especially BS type 1. The results of our study demonstrate that WES is useful in dealing with the phenotypic heterogeneity of these disorders, improving differential diagnosis and genotype-phenotype correlation.

Molecular Mechanisms and Biomarkers Associated with Chemotherapy-Induced AKI.

Acute kidney injury (AKI) is a life-threatening condition characterized by a rapid and transient decrease in kidney function. AKI is part of an array of conditions collectively defined as acute kidney diseases (AKD). In AKD, persistent kidney damage and dysfunction lead to chronic kidney disease (CKD) over time. A variety of insults can trigger AKI; however, chemotherapy-associated nephrotoxicity is increasingly recognized as a significant side effect of chemotherapy. New biomarkers are urgently needed to identify patients at high risk of developing chemotherapy-associated nephrotoxicity and subsequent AKI. However, a lack of understanding of cellular mechanisms that trigger chemotherapy-related nephrotoxicity has hindered the identification of effective biomarkers to date. In this review, we aim to (1) describe the known and potential mechanisms related to chemotherapy-induced AKI; (2) summarize the available biomarkers for early AKI detection, and (3) raise awareness of chemotherapy-induced AKI.

Idiopathic retroperitoneal fibrosis: an update for nephrologists.

Idiopathic retroperitoneal fibrosis (IRF) is a rare condition characterized by the development of a peri-aortic and peri-iliac tissue showing chronic inflammatory infiltrates and pronounced fibrosis. Ureteral entrapment with consequent obstructive uropathy is one of the most common complications of IRF, which can lead to acute renal failure and, in the long term, to varying degrees of chronic kidney disease. IRF may be isolated or develop in association with autoimmune diseases (e.g. Hashimoto's thyroiditis and psoriasis) and other fibro-inflammatory disorders (often within the spectrum of immunoglobulin G4-related disease), which suggests that it should be considered as a potentially systemic condition. IRF is an immune-mediated disease: genetic variants (e.g. human leukocyte antigen (HLA)-DRB1*03) and environmental agents (mainly exposure to asbestos and smoking) are strongly associated with an increased risk of developing the disease, while a complex network of chemokines (e.g. CXCL12 and C-C moti chemokine 11 (CCL11)) and cytokines [e.g. interleukin (IL)-6, IL-12 and IL-13] is likely to orchestrate the inflammatory response and simultaneously promote fibrosis. Glucocorticoids, alone or in combination with traditional immunosuppressants such as methotrexate and mycophenolate mofetil, are usually efficacious and promptly induce disease remission; however, up to 50% of patients relapse, thus requiring repeat immunosuppressive courses. Biologic drugs, namely rituximab, are being explored for the treatment of IRF. In addition to medical therapies, interventional procedures (mainly ureteral stenting) are required to relieve ureteral obstruction, whereas surgical ureterolysis is generally reserved to refractory cases. If appropriately treated, then the overall and renal prognosis of IRF are good, with <5% patients developing end-stage renal disease.

Cheyne-Stokes respiration related oscillations in cardiopulmonary hemodynamics in patients with heart failure.

BACKGROUND: Although Cheyne-Stokes respiration (CSR) is an oscillatory phenomenon, the direct effects of cyclical hyperventilation and apnea on cardiopulmonary hemodynamics have been poorly investigated. The aim of the study was to examine the echocardiographic changes associated with CSR phases in a group of patients with systolic heart failure (HF) and daytime CSR. METHODS: 14 HF patients (age 70 ±â€¯9 years, LVEF 24 ±â€¯5) underwent a thorough clinical evaluation, 24-h respiratory polygraphy, chemoreflex evaluation by rebreathing technique and neuro-hormonal assessment. Furthermore, they received a simultaneous echocardiographic and respiratory monitoring embedding the respiratory signal in the echocardiographic machine. RESULTS: All patients had daytime CSR (diurnal apnea-hypopnea index, AHI: 18.5, interquartile range: 15.3-39.5 events/h). Systolic pulmonary artery pressure and pulmonary vascular resistances (PVR) increased from hyperventilation to apnea (H 45.3 ±â€¯11.4 vs A 52.4 ±â€¯13.8 mmHg, p = 0.004, and H 3.3 ±â€¯2.5 vs A 5.1 ±â€¯3.2 Wood units, p = 0.0003, respectively), while acceleration time of the pulmonary artery decreased (H 110.1 ±â€¯19.8 vs A 92.0 ±â€¯19.9 ms, p = 0.001). During apnea a reduction of right and left ventricular outflow tract VTI (H 12.8 ±â€¯4.9 versus A 9.9 ±â€¯3.1, p = 0.002 and H 26.9 ±â€¯8.8 versus A 22.8 ±â€¯7.9 mm, p = 0.006, respectively), and a reduction in tricuspid annular plane systolic excursion (H 15.9 ±â€¯4.4 versus A 14.4 ±â€¯4.1 mm, p = 0.005) were also observed. Notably, PVR variation strongly correlated with chemosensitivity to hypercapnia (R = 0.89, p = 0.0004) and plasma norepinephrine level (R = 0.78, p = 0.003). CONCLUSIONS: In HF patients with CSR, an increase in pulmonary pressure and pulmonary vascular resistances was observed during apnea. Pulmonary vasoconstriction strongly correlated with chemosensitivity to hypercapnia and indexes of adrenergic activation.

Autonomic, functional, skeletal muscle, and cardiac abnormalities are associated with increased ergoreflex sensitivity in mitochondrial disease.

AIMS: Mitochondrial disease (MD) is a genetic disorder affecting skeletal muscles, with possible myocardial disease. The ergoreflex, sensitive to skeletal muscle work, regulates ventilatory and autonomic responses to exercise. We hypothesized the presence of an increased ergoreflex sensitivity in MD patients, its association with abnormal ventilatory and autonomic responses, and possibly with subclinical cardiac involvement. METHODS AND RESULTS: Twenty-five MD patients (aged 46 ± 3 years, 32% male) with skeletal myopathy but without known cardiac disease, underwent a thorough evaluation including BNPs, galectin-3, soluble suppression of tumorigenesis 2 (sST2), high sensitivity troponin T/I, catecholamines, ECG, 24-h ECG recording, cardiopulmonary exercise testing, echocardiography, cardiac/muscle magnetic resonance (C/MMR), and ergoreflex assessment. Thirteen age- and sex-matched healthy controls were chosen. Among these myopathic patients, subclinical cardiac damage was detected in up to 80%, with 44% showing fibrosis at CMR. Ergoreflex sensitivity was markedly higher in patients than in controls (64% vs. 37%, P < 0.001), and correlated with muscle fat to water ratio and extracellular volume at MMR (both P < 0.05). Among patients, ergoreflex sensitivity was higher in those with cardiac involvement (P = 0.034). Patients showed a lower peak oxygen consumption (VO2 /kg) than controls (P < 0.001), as well as ventilatory inefficiency (P = 0.024). Ergoreflex sensitivity correlated with reduced workload and peak VO2 /kg (both P < 0.001), and several indicators of autonomic imbalance (P < 0.05). Plasma norepinephrine was the unique predictor of myocardial fibrosis at univariate analysis (P < 0.05). CONCLUSIONS: Skeletal myopathy in MD is characterized by enhanced ergoreflex sensitivity, which is associated with a higher incidence of cardiac involvement, exercise intolerance, and sympathetic activation.

Targeting Mitochondrial Dysfunction in Chronic Heart Failure: Current Evidence and Potential Approaches.

BACKGROUND: Mitochondria are cellular organelles responsible for energy production, calcium handling, controlled synthesis of reactive oxygen species (ROS), and regulation of apoptosis. All these functions are crucial for cardiac homeostasis, and may be impaired in chronic heart failure (CHF). Therefore, mitochondrial dysfunction might represent a crucial element in the onset and progression of CHF and, as such, a promising therapeutic target. METHODS: Original articles and review on the treatment of mitochondrial dysfunction in CHF were searched on Medline and Scopus. RESULTS: The present review summarizes the current knowledge about mitochondrial modulation as a therapeutic strategy for CHF, and proposes some perspectives for future studies. Mitochondrial dysfunction can be ascribed to neuro-humoral activation and cardiac remodeling associated with CHF. Conceptually, the correction of mitochondrial dysfunction could provide an additive benefit to optimal CHF treatment. Increasing glucose metabolism and reducing oxidative stress within mitochondria are the two most promising approaches, even though further studies are required before implementing new treatments in the setting of CHF. On the other hand, inhibition of apoptosis, and normalization of calcium and mitochondrial dynamics have been assessed almost exclusively in ex vivo models, and mostly in settings other than CHF. CONCLUSION: Mitochondrial modulation in CHF is an intriguing example of translational research and a potentially rewarding field.

Influence of central apneas and chemoreflex activation on pulmonary artery pressure in chronic heart failure.

BACKGROUND: Pulmonary artery hypertension (PH), associated with increased left ventricular (LV) diastolic pressure and pulmonary vasoconstriction, is frequently observed in heart failure (HF), where it holds prognostic significance. We hypothesized that Cheyne-Stokes respiration (CSR) may contribute to increased pulmonary arterartery pressure (PAP) and right ventricular (RV) remodeling in HF, via hypoxia/hypercapnia cycles and adrenergic activation by the chemoreflex stimulation. METHODS: Seventy-two HF patients (57 males, aged 65.1 SD 12.3 years, LV ejection fraction<50%, 33.2 SD 7.5%), on guideline recommended pharmacological/device treatment underwent thorough clinical, echocardiographic and neurohormonal assessment, 24-hour cardiorespiratory screening for arrhythmias and CSR, and chemoreflex test for hypoxic (HVR) and hypercapnic (HCVR) ventilatory responses. RESULTS: Twenty patients (28%) showed significant CSR (24-hour apnea-hypopnea index, AHI≥15). Patients with CSR presented with: a) higher systolic pulmonary artery pressure (sPAP: 42.8 standard deviation-SD 10.1 vs 32.3 SD 5.7 mmHg, p<0.001), despite similar LV systolic and diastolic function; b) indexes of right chamber remodeling (all p<0.05); c) enhanced HVR (median 0.78, interquartile range-IR 0.46-1.22 vs 0.42, IR 0.18-0.67 L/min/%, p=0.01) and HCVR (1.17, IR 0.97-1.29 vs 0.72, IR 0.47-0.93 L/min/mmHg, p=0.02); d) increased plasma norepinephrine levels (690, IR 477-868 vs 366, IR 226-508 ng/L, p<0.001). Univariate predictors of sPAP>35 mmHg were AHI, HVR, HCVR; only AHI maintained its predictive value at multivariate analysis (p=0.017). CONCLUSIONS: CSR may contribute to increased pulmonary artery pressure and right chamber remodeling in HF, independently of the severity of LV systolic and diastolic dysfunction, likely via recurrent hypoxia/hypercapnia cycles and chemoreflex mediated adrenergic discharge.