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      Treatment-resistant nephrotic syndrome in dense deposit disease: complement-mediated glomerular capillary wall injury?

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          Abstract

          Background

          The C3 glomerulopathies (C3G) are recently defined glomerular diseases, attributed to abnormal complement regulation. Dense deposit disease (DDD) is part of the spectrum of C3G, characterized by electron-dense deposits in the lamina densa of the glomerular basement membrane. Patients with DDD present with hematuria, variable degrees of proteinuria, and kidney dysfunction. Kidney biopsies typically disclose proliferative and inflammatory patterns of injury. Treatment with glucocorticoids and mycophenolate mofetil has been shown to achieve remission of proteinuria in a significant proportion of C3G patients.

          Case-diagnosis/treatment

          We report two patients with persistent nephrotic syndrome while on immunosuppressive therapy. Repeat kidney biopsies disclosed massive C3 deposits with foot process effacement in the absence of proliferative or inflammatory lesions on light microscopy.

          Conclusion

          These cases, coupled with data from animal models of disease and the variable response to eculizumab in C3G patients, illustrate that two different pathways might be involved in the development of kidney injury in C3G: a C5-independent pathway leading to glomerular capillary wall injury and the development of proteinuria versus a C5-dependent pathway that causes proliferative glomerulonephritis and kidney dysfunction.

          Electronic supplementary material

          The online version of this article (10.1007/s00467-020-04600-9) contains supplementary material, which is available to authorized users.

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          Most cited references 15

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          C3a mediates epithelial-to-mesenchymal transition in proteinuric nephropathy.

          Tubulointerstitial inflammation and progressive fibrosis are common pathways that lead to kidney failure in proteinuric nephropathies. Activation of the complement system has been implicated in the development of tubulointerstitial injury in clinical and animal studies, but the mechanism by which complement induces kidney injury is not fully understood. Here, we studied the effect of complement on the phenotype of tubular epithelial cells. Tubular epithelial cells exposed to serum proteins adopted phenotypic and functional characteristics of mesenchymal cells. Expression of E-cadherin protein decreased and expression of both alpha-smooth muscle actin protein and collagen I mRNA increased. Exposure of the cells to the complement anaphylotoxin C3a induced similar features. Treating with a C3a receptor (C3aR) antagonist prevented both C3a- and serum-induced epithelial-to-mesenchymal transition. In the adriamycin-induced proteinuria model, C3aR-deficient mice demonstrated less injury, preserved renal function, and improved survival compared with wild-type mice. Furthermore, the kidneys of C3aR-deficient mice had significantly less interstitial collagen I and alpha-smooth muscle actin. In summary, the complement anaphylotoxin C3a is an important mediator of glomerular and tubulointerstitial injury and can induce tubular epithelial-to-mesenchymal transition.
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            Effectiveness of mycophenolate mofetil in C3 glomerulonephritis.

            C3 glomerulonephritis is a clinicopathologic entity defined by the presence of isolated or dominant deposits of C3 on immunofluorescence. To explore the effect of immunosuppression on C3 glomerulonephritis, we studied a series of 60 patients in whom a complete registry of treatments was available over a median follow-up of 47 months. Twenty patients had not received immunosuppressive treatments. In the remaining 40 patients, 22 had been treated with corticosteroids plus mycophenolate mofetil while 18 were treated with other immunosuppressive regimens (corticosteroids alone or corticosteroids plus cyclophosphamide). The number of patients developing end-stage renal disease was significantly lower among treated compared with untreated patients (3 vs. 7 patients, respectively). No patient in the corticosteroids plus mycophenolate mofetil group doubled serum creatinine nor developed end-stage renal disease, as compared with 7 (significant) and 3 (not significant), respectively, in patients treated with other immunosuppressive regimens. Renal survival (100, 80, and 72% at 5 years) and the number of patients achieving clinical remission (86, 50, and 25%) were significantly higher in patients treated with corticosteroids plus mycophenolate mofetil as compared with patients treated with other immunosuppressive regimens and untreated patients, respectively. Thus, immunosuppressive treatments, particularly corticosteroids plus mycophenolate mofetil, can be beneficial in C3 glomerulonephritis.
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              Prevention of C5 activation ameliorates spontaneous and experimental glomerulonephritis in factor H-deficient mice.

              Membranoproliferative glomerulonephritis (MPGN) type II (dense deposit disease) is an inflammatory renal disease characterized by electron-dense deposits and complement C3 on the glomerular basement membrane. There is no effective therapy. We investigated the role of C5 activation in a model of MPGN that develops spontaneously in complement factor H-deficient mice (Cfh(-/-)). At 12 months there was a significant reduction in mortality, glomerular cellularity, neutrophil numbers, and serum creatinine levels in Cfh(-/-) mice deficient in C5. Excessive glomerular neutrophil numbers, frequently seen in patients with MPGN during disease flares, were also observed in Cfh(-/-) mice after the administration of an antiglomerular basement membrane antibody. This exaggerated injurious phenotype was absent in Cfh(-/-) mice deficient in C5 but not in Cfh(-/-) mice deficient in C6, indicating a key role for C5 activation in the induction of renal lesions. Importantly, the renal injury was completely reversed in Cfh(-/-) mice pretreated with an anti-murine C5 antibody. These results demonstrate an important role for C5 in both spontaneous MPGN and experimentally induced nephritis in factor H-deficient mice and provide preliminary evidence that C5 inhibition therapy might be useful in human MPGN type II.
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                Author and article information

                Contributors
                caroline.duineveld@radboudumc.nl
                Journal
                Pediatr Nephrol
                Pediatr. Nephrol
                Pediatric Nephrology (Berlin, Germany)
                Springer Berlin Heidelberg (Berlin/Heidelberg )
                0931-041X
                1432-198X
                23 May 2020
                23 May 2020
                2020
                : 35
                : 9
                : 1791-1795
                Affiliations
                [1 ]GRID grid.10417.33, ISNI 0000 0004 0444 9382, Department of Nephrology, , Radboud University Medical Center, ; PO BOX 9101, 6500 HB Nijmegen, Netherlands
                [2 ]GRID grid.10417.33, ISNI 0000 0004 0444 9382, Department of Pathology, , Radboud University Medical Center, ; Nijmegen, Netherlands
                [3 ]GRID grid.239585.0, ISNI 0000 0001 2285 2675, Department of Medicine, Division of Nephrology, , Columbia University Medical Center, ; New York, NY USA
                [4 ]GRID grid.10417.33, ISNI 0000 0004 0444 9382, Department of Pediatric Nephrology, Radboud Institute for Molecular Life Sciences, Amalia Children’s Hospital, , Radboud University Medical Center, ; Nijmegen, Netherlands
                Article
                4600
                10.1007/s00467-020-04600-9
                7384995
                32447506
                © The Author(s) 2020

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

                Funding
                Funded by: Radboud University Medical Center
                Categories
                Brief Report
                Custom metadata
                © IPNA 2020

                Nephrology

                nephrotic syndrome, c3 glomerulopathy, dense deposit disease, podocyte

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