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      Multiple Mechanisms in Renal Artery Stenosis-Induced Renal Interstitial Fibrosis

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          Abstract

          Background/Aims: Renal artery stenosis (RAS), which may lead to renal fibrosis, is a common cause of end-stage renal disease in elderly patients. However, the potential mechanisms leading to the development of renal fibrosis and atrophy have not been clarified. Methods: A two-kidney, one-clip Goldblatt mouse model was established in the present study . Blood pressure, morphological and pathological alterations were examined on days 7, 14, and 28 after surgery. Peritubular capillary loss and pericyte changes after injury were evaluated. Inflammatory macrophage infiltration and Wnt/β-catenin signaling were also investigated. Results: A significant increase in blood pressure and obvious renal atrophy were observed on days 7, 14, and 28 after surgery. Following surgery, the clipped kidneys developed aggravated interstitial fibrosis and tubular epithelial injury over time. Moreover, RAS induced obvious peritubular capillary loss and inflammatory macrophage infiltration. Increased pericyte number was found in the clipped kidneys, but these cells detached from the endothelial cells and migrated to the interstitium. Wnt/β-catenin signaling was also significantly upregulated in the clipped kidneys after surgery. Conclusion: Our study provides a novel insight into the mechanisms linking peritubular capillary loss and pericyte changes in RAS-induced renal fibrosis. Our findings also suggest that inflammatory macrophages and Wnt/β-catenin signaling participate in these pathological processes. Therefore, multi-target therapeutic strategies may significantly contribute to the prevention of renal interstitial fibrosis and the preservation of renal function in patients with RAS.

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          Most cited references 27

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          Wnt/beta-catenin signaling promotes renal interstitial fibrosis.

          Wnts compose a family of signaling proteins that play an essential role in kidney development, but their expression in adult kidney is thought to be silenced. Here, we analyzed the expression and regulation of Wnts and their receptors and antagonists in normal and fibrotic kidneys after obstructive injury. In the normal mouse kidney, the vast majority of 19 different Wnts and 10 frizzled receptor genes was expressed at various levels. After unilateral ureteral obstruction, all members of the Wnt family except Wnt5b, Wnt8b, and Wnt9b were upregulated in the fibrotic kidney with distinct dynamics. In addition, the expression of most Fzd receptors and Wnt antagonists was also induced. Obstructive injury led to a dramatic accumulation of beta-catenin in the cytoplasm and nuclei of renal tubular epithelial cells, indicating activation of the canonical pathway of Wnt signaling. Numerous Wnt/beta-catenin target genes (c-Myc, Twist, lymphoid enhancer-binding factor 1, and fibronectin) were induced, and their expression was closely correlated with renal beta-catenin abundance. Delivery of the Wnt antagonist Dickkopf-1 gene significantly reduced renal beta-catenin accumulation and inhibited the expression of Wnt/beta-catenin target genes. Furthermore, gene therapy with Dickkopf-1 inhibited myofibroblast activation; suppressed expression of fibroblast-specific protein 1, type I collagen, and fibronectin; and reduced total collagen content in the model of obstructive nephropathy. In summary, these results establish a role for Wnt/beta-catenin signaling in the pathogenesis of renal fibrosis and identify this pathway as a potential therapeutic target.
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            Revascularization versus medical therapy for renal-artery stenosis.

            Percutaneous revascularization of the renal arteries improves patency in atherosclerotic renovascular disease, yet evidence of a clinical benefit is limited. In a randomized, unblinded trial, we assigned 806 patients with atherosclerotic renovascular disease either to undergo revascularization in addition to receiving medical therapy or to receive medical therapy alone. The primary outcome was renal function, as measured by the reciprocal of the serum creatinine level (a measure that has a linear relationship with creatinine clearance). Secondary outcomes were blood pressure, the time to renal and major cardiovascular events, and mortality. The median follow-up was 34 months. During a 5-year period, the rate of progression of renal impairment (as shown by the slope of the reciprocal of the serum creatinine level) was -0.07x10(-3) liters per micromole per year in the revascularization group, as compared with -0.13x10(-3) liters per micromole per year in the medical-therapy group, a difference favoring revascularization of 0.06x10(-3) liters per micromole per year (95% confidence interval [CI], -0.002 to 0.13; P=0.06). Over the same time, the mean serum creatinine level was 1.6 micromol per liter (95% CI, -8.4 to 5.2 [0.02 mg per deciliter; 95% CI, -0.10 to 0.06]) lower in the revascularization group than in the medical-therapy group. There was no significant between-group difference in systolic blood pressure; the decrease in diastolic blood pressure was smaller in the revascularization group than in the medical-therapy group. The two study groups had similar rates of renal events (hazard ratio in the revascularization group, 0.97; 95% CI, 0.67 to 1.40; P=0.88), major cardiovascular events (hazard ratio, 0.94; 95% CI, 0.75 to 1.19; P=0.61), and death (hazard ratio, 0.90; 95% CI, 0.69 to 1.18; P=0.46). Serious complications associated with revascularization occurred in 23 patients, including 2 deaths and 3 amputations of toes or limbs. We found substantial risks but no evidence of a worthwhile clinical benefit from revascularization in patients with atherosclerotic renovascular disease. (Current Controlled Trials number, ISRCTN59586944.) 2009 Massachusetts Medical Society
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              Wnt/beta-catenin signaling promotes podocyte dysfunction and albuminuria.

              Podocyte dysfunction, one of the major causes of proteinuria, leads to glomerulosclerosis and end stage renal disease, but its underlying mechanism remains poorly understood. Here we show that Wnt/beta-catenin signaling plays a critical role in podocyte injury and proteinuria. Treatment with adriamycin induced Wnt and activated beta-catenin in mouse podocytes. Overexpression of Wnt1 in vivo activated glomerular beta-catenin and aggravated albuminuria and adriamycin-induced suppression of nephrin expression, whereas blockade of Wnt signaling with Dickkopf-1 ameliorated podocyte lesions. Podocyte-specific knockout of beta-catenin protected against development of albuminuria after injury. Moreover, pharmacologic activation of beta-catenin induced albuminuria in wild-type mice but not in beta-catenin-knockout littermates. In human proteinuric kidney diseases such as diabetic nephropathy and focal segmental glomerulosclerosis, we observed upregulation of Wnt1 and active beta-catenin in podocytes. Ectopic expression of either Wnt1 or stabilized beta-catenin in vitro induced the transcription factor Snail and suppressed nephrin expression, leading to podocyte dysfunction. These results suggest that targeting hyperactive Wnt/beta-catenin signaling may represent a novel therapeutic strategy for proteinuric kidney diseases.
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                Author and article information

                Journal
                NEE
                Nephron Exp Nephrol
                10.1159/issn.1660-2129
                Cardiorenal Medicine
                S. Karger AG
                1660-2129
                2014
                December 2014
                08 November 2014
                : 128
                : 1-2
                : 57-66
                Affiliations
                aDepartment of Nephrology, 2nd Affiliated Hospital of Harbin Medical University, and bDepartment of Nephrology, 4th Affiliated Hospital of Harbin Medical University, Harbin, China
                Author notes
                *Prof. Bing Li, Department of Nephrology, 2nd Affiliated, Hospital of Harbin Medical University, 246 Xuefu Road, Harbin 150086 (China), E-Mail icecreamlee@hotmail.com
                Article
                366481 Nephron Exp Nephrol 2014;128:57-66
                10.1159/000366481
                25402740
                © 2014 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 4, Pages: 10
                Categories
                Original Paper

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