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Lang K, Milosavljevic J, Heinkele H, Chen M, Gerstner L, Spitz D, Kayser S, Helmstädter M, Walz G, Köttgen M, Spracklen A, Poulton J, Hermle T. Selective endocytosis controls slit diaphragm maintenance and dynamics in Drosophila nephrocytes. eLife 2022; 11:79037. [PMID: 35876643 PMCID: PMC9355562 DOI: 10.7554/elife.79037] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 07/24/2022] [Indexed: 11/28/2022] Open
Abstract
The kidneys generate about 180 l of primary urine per day by filtration of plasma. An essential part of the filtration barrier is the slit diaphragm, a multiprotein complex containing nephrin as major component. Filter dysfunction typically manifests with proteinuria and mutations in endocytosis regulating genes were discovered as causes of proteinuria. However, it is unclear how endocytosis regulates the slit diaphragm and how the filtration barrier is maintained without either protein leakage or filter clogging. Here, we study nephrin dynamics in podocyte-like nephrocytes of Drosophila and show that selective endocytosis either by dynamin- or flotillin-mediated pathways regulates a stable yet highly dynamic architecture. Short-term manipulation of endocytic functions indicates that dynamin-mediated endocytosis of ectopic nephrin restricts slit diaphragm formation spatially while flotillin-mediated turnover of nephrin within the slit diaphragm is needed to maintain filter permeability by shedding of molecules bound to nephrin in endosomes. Since slit diaphragms cannot be studied in vitro and are poorly accessible in mouse models, this is the first analysis of their dynamics within the slit diaphragm multiprotein complex. Identification of the mechanisms of slit diaphragm maintenance will help to develop novel therapies for proteinuric renal diseases that are frequently limited to symptomatic treatment.
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Affiliation(s)
- Konrad Lang
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Helena Heinkele
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Mengmeng Chen
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Lea Gerstner
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Dominik Spitz
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Severine Kayser
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Gerd Walz
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Köttgen
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Andrew Spracklen
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - John Poulton
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Tobias Hermle
- Department of Medicine, University of Freiburg, Freiburg, Germany
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52
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Nephroprotective Effects of Semaglutide as Mono- and Combination Treatment with Lisinopril in a Mouse Model of Hypertension-Accelerated Diabetic Kidney Disease. Biomedicines 2022; 10:biomedicines10071661. [PMID: 35884965 PMCID: PMC9313388 DOI: 10.3390/biomedicines10071661] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/02/2022] [Accepted: 07/04/2022] [Indexed: 11/25/2022] Open
Abstract
Background: Obesity, hyperglycemia and hypertension are critical risk factors for development of diabetic kidney disease (DKD). Emerging evidence suggests that glucagon-like peptide-1 receptor (GLP-1R) agonists improve cardiovascular and renal outcomes in type 2 diabetes patients. Here, we characterized the effect of the long-acting GLP-1R agonist semaglutide alone and in combination with an ACE inhibitor (lisinopril) in a model of hypertension-accelerated, advanced DKD facilitated by adeno-associated virus-mediated renin overexpression (ReninAAV) in uninephrectomized (UNx) female diabetic db/db mice. Methods: Female db/db mice received a single intravenous injection of ReninAAV 1 week prior to UNx. Six weeks post-nephrectomy, db/db UNx-ReninAAV mice were administered (q.d.) vehicle, semaglutide (30 nmol/kg, s.c.) or semaglutide (30 nmol/kg, s.c.) + lisinopril (30 mg/kg, p.o.) for 11 weeks. Endpoints included blood pressure, plasma/urine biochemistry, kidney histopathology and RNA sequencing. Results: Vehicle-dosed db/db UNx-ReninAAV mice developed hallmarks of DKD characterized by severe albuminuria and advanced glomerulosclerosis. Semaglutide robustly reduced hyperglycemia, hypertension and albuminuria concurrent with notable improvements in glomerulosclerosis severity, podocyte filtration slit density, urine/renal kidney injury molecule-1 (KIM-1) levels and gene expression markers of inflammation and fibrogenesis in db/db UNx-ReninAAV mice. Co-administration of lisinopril further ameliorated hypertension and glomerulosclerosis. Conclusions: Semaglutide improves disease hallmarks in the db/db UNx-ReninAAV mouse model of advanced DKD. Further benefits on renal outcomes were obtained by adjunctive antihypertensive standard of care. Collectively, our study supports the development of semaglutide for management of DKD.
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53
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Röck R, Rizzo L, Lienkamp SS. Kidney Development: Recent Insights from Technological Advances. Physiology (Bethesda) 2022; 37:0. [PMID: 35253460 DOI: 10.1152/physiol.00041.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The kidney is a complex organ, and how it forms is a fascinating process. New technologies, such as single-cell transcriptomics, and enhanced imaging modalities are offering new approaches to understand the complex and intertwined processes during embryonic kidney development.
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Affiliation(s)
- Ruth Röck
- Institute of Anatomy, University of Zurich, Zurich, Switzerland.,Swiss National Centres of Competence in Research (NCCR) Kidney Control of Homeostasis (Kidney.CH), Zurich, Switzerland
| | - Ludovica Rizzo
- Institute of Anatomy, University of Zurich, Zurich, Switzerland.,Swiss National Centres of Competence in Research (NCCR) Kidney Control of Homeostasis (Kidney.CH), Zurich, Switzerland.,PhD program "Molecular and Translational Biomedicine," Life Science Zurich Graduate School, Zurich, Switzerland
| | - Soeren S Lienkamp
- Institute of Anatomy, University of Zurich, Zurich, Switzerland.,Swiss National Centres of Competence in Research (NCCR) Kidney Control of Homeostasis (Kidney.CH), Zurich, Switzerland
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54
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Mechanisms of podocyte injury and implications for diabetic nephropathy. Clin Sci (Lond) 2022; 136:493-520. [PMID: 35415751 PMCID: PMC9008595 DOI: 10.1042/cs20210625] [Citation(s) in RCA: 47] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 02/25/2022] [Accepted: 03/25/2022] [Indexed: 02/06/2023]
Abstract
Albuminuria is the hallmark of both primary and secondary proteinuric glomerulopathies, including focal segmental glomerulosclerosis (FSGS), obesity-related nephropathy, and diabetic nephropathy (DN). Moreover, albuminuria is an important feature of all chronic kidney diseases (CKDs). Podocytes play a key role in maintaining the permselectivity of the glomerular filtration barrier (GFB) and injury of the podocyte, leading to foot process (FP) effacement and podocyte loss, the unifying underlying mechanism of proteinuric glomerulopathies. The metabolic insult of hyperglycemia is of paramount importance in the pathogenesis of DN, while insults leading to podocyte damage are poorly defined in other proteinuric glomerulopathies. However, shared mechanisms of podocyte damage have been identified. Herein, we will review the role of haemodynamic and oxidative stress, inflammation, lipotoxicity, endocannabinoid (EC) hypertone, and both mitochondrial and autophagic dysfunction in the pathogenesis of the podocyte damage, focussing particularly on their role in the pathogenesis of DN. Gaining a better insight into the mechanisms of podocyte injury may provide novel targets for treatment. Moreover, novel strategies for boosting podocyte repair may open the way to podocyte regenerative medicine.
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55
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Abstract
Circulating blood is filtered across the glomerular barrier to form an ultrafiltrate of plasma in the Bowman's space. The volume of glomerular filtration adjusted by time is defined as the glomerular filtration rate (GFR), and the total GFR is the sum of all single-nephron GFRs. Thus, when the single-nephron GFR is increased in the context of a normal number of functioning nephrons, single glomerular hyperfiltration results in 'absolute' hyperfiltration in the kidney. 'Absolute' hyperfiltration can occur in healthy people after high protein intake, during pregnancy and in patients with diabetes, obesity or autosomal-dominant polycystic kidney disease. When the number of functioning nephrons is reduced, single-nephron glomerular hyperfiltration can result in a GFR that is within or below the normal range. This 'relative' hyperfiltration can occur in patients with a congenitally reduced nephron number or with an acquired reduction in nephron mass consequent to surgery or kidney disease. Improved understanding of the mechanisms that underlie 'absolute' and 'relative' glomerular hyperfiltration in different clinical settings, and of whether and how the single-nephron haemodynamic and related biomechanical forces that underlie glomerular hyperfiltration promote glomerular injury, will pave the way toward the development of novel therapeutic interventions that attenuate glomerular hyperfiltration and potentially prevent or limit consequent progressive kidney injury and loss of function.
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56
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Synergic Renoprotective Effects of Combined ASC Therapy with RAAS Blockade in Experimental Advanced CKD. Stem Cells Int 2022; 2022:5111782. [PMID: 35371263 PMCID: PMC8975629 DOI: 10.1155/2022/5111782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 02/23/2022] [Indexed: 11/18/2022] Open
Abstract
Global prevalence of chronic kidney disease (CKD) has increased considerably in the recent decades. Overactivity of the renin-angiotensin-aldosterone system (RAAS), associated to renal inflammation and fibrosis, contributes to its evolution. The treatments currently employed to control CKD progression are limited and mainly based on the pharmacological inhibition of RAAS, associated with diuretics and immunosuppressive drugs. However, this conservative management promotes only partial deceleration of CKD evolution and does not completely avoid the progression of the disease and the loss of renal function, which motivates the medical and scientific community to investigate new therapeutic approaches to detain renal inflammation/fibrosis and CKD progression. Recent studies have shown the application of mesenchymal stem cells (mSC) to exert beneficial effects on the renal tissue of animals submitted to experimental models of CKD. In this context, the aim of the present study was to evaluate the effects of subcapsular application of adipose tissue-derived mSC (ASC) in rats submitted to the 5/6 renal ablation model, 15 days after the establishment of CKD, when the nephropathy was already severe. We also verify whether ASC associated to Losartan would promote greater renoprotection when compared to the respective monotherapies. Animals were followed until 30 days of CKD, when body weight, systolic blood pressure, biochemical, histological, immunohistochemical, and gene expression analysis were performed. The combination of ASC and Losartan was more effective than Losartan monotherapy in reducing systolic blood pressure and glomerulosclerosis and also promoted the complete normalization of proteinuria and albuminuria, a significant reduction in renal interstitial macrophage infiltration and downregulation of renal IL-6 gene expression. The beneficial effects of ACS are possibly due to the immunomodulatory and anti-inflammatory role of factors secreted by these cells, modulating the local immune response. Although studies are still required, our results demonstrated that a subcapsular inoculation of ASC, associated with the administration of Losartan, exerted additional renoprotective effect in rats submitted to a severe model of established CKD, when compared to Losartan monotherapy, thus suggesting ASC may be a potential adjuvant to RAAS-blockade therapy currently employed in the conservative management of CKD.
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57
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Rogg M, Maier JI, Van Wymersch C, Helmstädter M, Sammarco A, Lindenmeyer M, Zareba P, Montanez E, Walz G, Werner M, Endlich N, Benzing T, Huber TB, Schell C. α-Parvin Defines a Specific Integrin Adhesome to Maintain the Glomerular Filtration Barrier. J Am Soc Nephrol 2022; 33:786-808. [PMID: 35260418 PMCID: PMC8970443 DOI: 10.1681/asn.2021101319] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 01/17/2022] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND The cell-matrix adhesion between podocytes and the glomerular basement membrane is essential for the integrity of the kidney's filtration barrier. Despite increasing knowledge about the complexity of integrin adhesion complexes, an understanding of the regulation of these protein complexes in glomerular disease remains elusive. METHODS We mapped the in vivo composition of the podocyte integrin adhesome. In addition, we analyzed conditional knockout mice targeting a gene (Parva) that encodes an actin-binding protein (α-parvin), and murine disease models. To evaluate podocytes in vivo, we used super-resolution microscopy, electron microscopy, multiplex immunofluorescence microscopy, and RNA sequencing. We performed functional analysis of CRISPR/Cas9-generated PARVA single knockout podocytes and PARVA and PARVB double knockout podocytes in three- and two-dimensional cultures using specific extracellular matrix ligands and micropatterns. RESULTS We found that PARVA is essential to prevent podocyte foot process effacement, detachment from the glomerular basement membrane, and the development of FSGS. Through the use of in vitro and in vivo models, we identified an inherent PARVB-dependent compensatory module at podocyte integrin adhesion complexes, sustaining efficient mechanical linkage at the filtration barrier. Sequential genetic deletion of PARVA and PARVB induces a switch in structure and composition of integrin adhesion complexes. This redistribution of these complexes translates into a loss of the ventral actin cytoskeleton, decreased adhesion capacity, impaired mechanical resistance, and dysfunctional extracellular matrix assembly. CONCLUSIONS The findings reveal adaptive mechanisms of podocyte integrin adhesion complexes, providing a conceptual framework for therapeutic strategies to prevent podocyte detachment in glomerular disease.
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Affiliation(s)
- Manuel Rogg
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Jasmin I Maier
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Clara Van Wymersch
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Martin Helmstädter
- Department of Medicine IV, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Alena Sammarco
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Maja Lindenmeyer
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Paulina Zareba
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Eloi Montanez
- Department of Physiological Sciences, Faculty of Medicine, University of Barcelona and Health Sciences and Bellvitge Biomedical Research Institute (IDIBELL), Barcelona, Spain
| | - Gerd Walz
- Department of Medicine IV, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Martin Werner
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany
| | - Nicole Endlich
- Department of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Tobias B Huber
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christoph Schell
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center-University of Freiburg, Freiburg, Germany .,Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany
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58
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Doi K, Kimura H, Matsunaga YT, Fujii T, Nangaku M. Glomerulus-on-a-Chip: Current Insights and Future Potential Towards Recapitulating Selectively Permeable Filtration Systems. Int J Nephrol Renovasc Dis 2022; 15:85-101. [PMID: 35299832 PMCID: PMC8922329 DOI: 10.2147/ijnrd.s344725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Accepted: 02/14/2022] [Indexed: 01/27/2023] Open
Affiliation(s)
- Kotaro Doi
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Hiroshi Kimura
- Department of Mechanical Engineering, School of Engineering, Tokai University, Kanagawa, Japan
| | | | | | - Masaomi Nangaku
- Division of Nephrology and Endocrinology, The University of Tokyo Graduate School of Medicine, Tokyo, Japan
- Correspondence: Masaomi Nangaku, Division of Nephrology and Endocrinology, The University of Tokyo Graduate School of Medicine, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan, Tel/Fax +81358009736, Email
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59
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Edwards A, Long KR, Baty CJ, Shipman KE, Weisz OA. Modeling normal and nephrotic axial uptake of albumin and other filtered proteins along the proximal tubule. J Physiol 2022; 600:1933-1952. [PMID: 35178707 PMCID: PMC9012691 DOI: 10.1113/jp282885] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 02/10/2022] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We used new and published data to develop a mathematical model that predicts the profile of albumin uptake in the mouse proximal tubule (PT) in normal and nephrotic states, and partially accounts for competitive inhibition of uptake by normally filtered and pathologic ligands. Three pathways, consisting of high-affinity uptake by cubilin receptors, low-affinity uptake by megalin receptors, and fluid phase uptake, contribute to the overall retrieval of filtered proteins. The axial profile and efficiency of protein uptake depend on the initial filtrate composition and the individual protein affinities for megalin and cubilin. Under normal conditions, the majority of albumin is retrieved in S1 but shifts to S2 under nephrotic conditions. Other proteins exhibit different uptake profiles. Our model explains how tubular proteinuria can occur despite a large excess in potential PT uptake capacity. ABSTRACT Recent studies indicate that filtered albumin is retrieved in the proximal tubule (PT) via three pathways: receptor-mediated endocytosis via cubilin (high affinity) and megalin (low affinity), and fluid-phase uptake. Expression of megalin is required to maintain all three pathways, making it challenging to determine their respective contributions. Moreover, uptake of filtered molecules varies between the sub-segments (S1, S2, and S3) that make up the PT. Here we used new and published data to develop a mathematical model that predicts the rates of albumin uptake in mouse PT sub-segments in normal and nephrotic states, and partially accounts for competition by β2-microglobulin (β2m) and Immunoglobulin G (IgG). Our simulations indicate that receptor-mediated, rather than fluid-phase uptake, accounts for the vast majority of ligand recovery. Our model predicts that ∼75% of normally filtered albumin is reabsorbed via cubilin; however, megalin-mediated uptake predominates under nephrotic conditions. Our results also suggest that ∼80% of albumin is normally recovered in S1, whereas nephrotic conditions or knockout of cubilin shifts the bulk of albumin uptake to S2. The model predicts β2m and IgG axial recovery profiles qualitatively similar to those of albumin under normal conditions. In contrast with albumin however, the bulk of IgG and β2m uptake still occurs in S1 under nephrotic conditions. Overall, our model provides a kinetic rationale for why tubular proteinuria can occur even though a large excess in potential PT uptake capacity exists, and suggests testable predictions to expand our understanding of the recovery profile of filtered proteins along the PT. Abstract figure legend. Data from mouse models and from cultured proximal tubule (PT) cells were used to create a mathematical model that predicts the uptake profile of albumin and other filtered ligands along the mouse PT in normal and nephrotic states. The distinct contributions of cubilin receptors (magenta), megalin receptors (green), and fluid phase uptake (blue) to total albumin retrieval (black) in S1, S2, and S3 subsegments of the PT are delineated. Under normal conditions, albumin is primarily recovered in the S1 segment by cubilin, whereas the majority is retrieved in S2 under nephrotic conditions. Other proteins exhibit strikingly different uptake profiles. Our model explains how the distribution and capacity of high-affinity and low-affinity uptake pathways enable uptake of albumin over a broad range of filtered concentrations, and how tubular proteinuria can occur despite a large excess in potential PT uptake capacity. Created with BioRender.com. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Aurélie Edwards
- Department of Biomedical Engineering, Boston University, Boston, MA, 02215, USA
| | - Kimberly R Long
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Catherine J Baty
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Katherine E Shipman
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Ora A Weisz
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
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60
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Kabasawa K, Hosojima M, Ito Y, Matsushima K, Tanaka J, Hara M, Nakamura K, Narita I, Saito A. Association of metabolic syndrome traits with urinary biomarkers in Japanese adults. Diabetol Metab Syndr 2022; 14:9. [PMID: 35033174 PMCID: PMC8760661 DOI: 10.1186/s13098-021-00779-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 12/28/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Although metabolic syndrome traits are risk factors for chronic kidney disease, few studies have examined their association with urinary biomarkers. METHODS Urinary biomarkers, including A-megalin, C-megalin, podocalyxin, albumin, α1-microglobulin, β2-microglobulin, and N-acetyl-β-D-glucosaminidase, were cross-sectionally assessed in 347 individuals (52.7% men) with a urine albumin-to-creatinine ratio (ACR) < 300 mg/g in a health checkup. Metabolic syndrome traits were adopted from the National Cholesterol Education Program (third revision) of the Adult Treatment Panel criteria modified for Asians. RESULTS Participants had a mean body mass index, estimated glomerular filtration rate (eGFR), and median ACR of 23.0 kg/m2, 74.8 mL/min/1.73 m2, and 7.5 mg/g, respectively. In age- and sex-adjusted logistic regression analysis, A-megalin and albumin were significantly associated with the clustering number of metabolic syndrome traits (3 or more). After further adjustment with eGFR, higher quartiles of A-megalin and albumin were each independently associated with the clustering number of metabolic syndrome traits (adjusted odds ratio for A-megalin: 1.30 per quartile, 95% CI 1.03-1.64; albumin: 1.42 per quartile, 95% CI 1.12-1.79). CONCLUSIONS Both urinary A-megalin and albumin are associated with the clustering number of metabolic syndrome traits. Further research on urinary A-megalin is warranted to examine its role as a potential marker of kidney damage from metabolic risk factors.
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Affiliation(s)
- Keiko Kabasawa
- Department of Health Promotion Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
| | - Michihiro Hosojima
- Department of Clinical Nutrition Science, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Yumi Ito
- Department of Health Promotion Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | | | - Junta Tanaka
- Department of Health Promotion Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | | | - Kazutoshi Nakamura
- Division of Preventive Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Ichiei Narita
- Department of Health Promotion Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
- Division of Clinical Nephrology and Rheumatology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Akihiko Saito
- Department of Applied Molecular Medicine, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
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61
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Qu C, Roth R, Puapatanakul P, Loitman C, Hammad D, Genin GM, Miner JH, Suleiman HY. Three-Dimensional Visualization of the Podocyte Actin Network Using Integrated Membrane Extraction, Electron Microscopy, and Machine Learning. J Am Soc Nephrol 2022; 33:155-173. [PMID: 34758982 PMCID: PMC8763187 DOI: 10.1681/asn.2021020182] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 10/19/2021] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Actin stress fibers are abundant in cultured cells, but little is known about them in vivo. In podocytes, much evidence suggests that mechanobiologic mechanisms underlie podocyte shape and adhesion in health and in injury, with structural changes to actin stress fibers potentially responsible for pathologic changes to cell morphology. However, this hypothesis is difficult to rigorously test in vivo due to challenges with visualization. A technology to image the actin cytoskeleton at high resolution is needed to better understand the role of structures such as actin stress fibers in podocytes. METHODS We developed the first visualization technique capable of resolving the three-dimensional cytoskeletal network in mouse podocytes in detail, while definitively identifying the proteins that comprise this network. This technique integrates membrane extraction, focused ion-beam scanning electron microscopy, and machine learning image segmentation. RESULTS Using isolated mouse glomeruli from healthy animals, we observed actin cables and intermediate filaments linking the interdigitated podocyte foot processes to newly described contractile actin structures, located at the periphery of the podocyte cell body. Actin cables within foot processes formed a continuous, mesh-like, electron-dense sheet that incorporated the slit diaphragms. CONCLUSIONS Our new technique revealed, for the first time, the detailed three-dimensional organization of actin networks in healthy podocytes. In addition to being consistent with the gel compression hypothesis, which posits that foot processes connected by slit diaphragms act together to counterbalance the hydrodynamic forces across the glomerular filtration barrier, our data provide insight into how podocytes respond to mechanical cues from their surrounding environment.
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Affiliation(s)
- Chengqing Qu
- Department of Mechanical Engineering, National Science Foundation Science and Technology Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, Missouri
| | - Robyn Roth
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri
| | | | - Charles Loitman
- Division of Nephrology, Washington University School of Medicine, St. Louis, Missouri
| | - Dina Hammad
- Division of Nephrology, Washington University School of Medicine, St. Louis, Missouri
| | - Guy M. Genin
- Department of Mechanical Engineering, National Science Foundation Science and Technology Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, Missouri
| | - Jeffrey H. Miner
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri,Division of Nephrology, Washington University School of Medicine, St. Louis, Missouri
| | - Hani Y. Suleiman
- Division of Nephrology, Washington University School of Medicine, St. Louis, Missouri
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62
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Butt L, Unnersjö-Jess D, Höhne M, Hahnfeldt R, Reilly D, Rinschen MM, Plagmann I, Diefenhardt P, Brähler S, Brinkkötter PT, Brismar H, Blom H, Schermer B, Benzing T. Super-Resolution Imaging of the Filtration Barrier Suggests a Role for Podocin R229Q in Genetic Predisposition to Glomerular Disease. J Am Soc Nephrol 2022; 33:138-154. [PMID: 34853150 PMCID: PMC8763184 DOI: 10.1681/asn.2020060858] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 10/07/2021] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Diseases of the kidney's glomerular filtration barrier are a leading cause of end stage renal failure. Despite a growing understanding of genes involved in glomerular disorders in children, the vast majority of adult patients lack a clear genetic diagnosis. The protein podocin p.R229Q, which results from the most common missense variant in NPHS2, is enriched in cohorts of patients with FSGS. However, p.R229Q has been proposed to cause disease only when transassociated with specific additional genetic alterations, and population-based epidemiologic studies on its association with albuminuria yielded ambiguous results. METHODS To test whether podocin p.R229Q may also predispose to the complex disease pathogenesis in adults, we introduced the exact genetic alteration in mice using CRISPR/Cas9-based genome editing (PodR231Q ). We assessed the phenotype using super-resolution microscopy and albuminuria measurements and evaluated the stability of the mutant protein in cell culture experiments. RESULTS Heterozygous PodR231Q/wild-type mice did not present any overt kidney disease or proteinuria. However, homozygous PodR231Q/R231Q mice developed increased levels of albuminuria with age, and super-resolution microscopy revealed preceding ultrastructural morphologic alterations that were recently linked to disease predisposition. When injected with nephrotoxic serum to induce glomerular injury, heterozygous PodR231Q/wild-type mice showed a more severe course of disease compared with Podwild-type/wild-type mice. Podocin protein levels were decreased in PodR231Q/wild-type and PodR231Q/R231Q mice as well as in human cultured podocytes expressing the podocinR231Q variant. Our in vitro experiments indicate an underlying increased proteasomal degradation. CONCLUSIONS Our findings demonstrate that podocin R231Q exerts a pathogenic effect on its own, supporting the concept of podocin R229Q contributing to genetic predisposition in adult patients.
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Affiliation(s)
- Linus Butt
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne and University Hospital Cologne, Cologne, Germany
| | - David Unnersjö-Jess
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne and University Hospital Cologne, Cologne, Germany
| | - Martin Höhne
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne and University Hospital Cologne, Cologne, Germany
| | - Robert Hahnfeldt
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne and University Hospital Cologne, Cologne, Germany
| | - Dervla Reilly
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne and University Hospital Cologne, Cologne, Germany
| | - Markus M. Rinschen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark,III Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Ingo Plagmann
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne and University Hospital Cologne, Cologne, Germany
| | - Paul Diefenhardt
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne and University Hospital Cologne, Cologne, Germany
| | - Sebastian Brähler
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne and University Hospital Cologne, Cologne, Germany
| | - Paul T. Brinkkötter
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne and University Hospital Cologne, Cologne, Germany
| | - Hjalmar Brismar
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Hans Blom
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Stockholm, Sweden
| | - Bernhard Schermer
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne and University Hospital Cologne, Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne and University Hospital Cologne, Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
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Koehler S, Odenthal J, Ludwig V, Jess DU, Höhne M, Jüngst C, Grawe F, Helmstädter M, Janku JL, Bergmann C, Hoyer PF, Hagmann HHH, Walz G, Bloch W, Niessen C, Schermer B, Wodarz A, Denholm B, Benzing T, Iden S, Brinkkoetter PT. Scaffold polarity proteins Par3A and Par3B share redundant functions while Par3B acts independent of atypical protein kinase C/Par6 in podocytes to maintain the kidney filtration barrier. Kidney Int 2021; 101:733-751. [PMID: 34929254 DOI: 10.1016/j.kint.2021.11.030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 11/08/2021] [Accepted: 11/22/2021] [Indexed: 10/19/2022]
Abstract
Glomerular diseases are a major cause for chronic kidney disorders. In most cases podocyte injury is causative for disease development. Cytoskeletal rearrangements and morphological changes are hallmark features of podocyte injury and result in dedifferentiation and loss of podocytes. Here, we establish a link between the Par3 polarity complex and actin regulators necessary to establish and maintain podocyte architecture by utilizing mouse and Drosophila models to characterize the functional role of Par3A and Par3B and its fly homologue Bazooka in vivo. Only simultaneous inactivation of both Par3 proteins caused a severe disease phenotype. Rescue experiments in Drosophila nephrocytes revealed atypical protein kinase C (aPKC)-Par6 dependent and independent effects. While Par3A primarily acts via aPKC-Par6, Par3B function was independent of Par6. Actin-associated synaptopodin protein levels were found to be significantly upregulated upon loss of Par3A/B in mouse podocytes. Tropomyosin2, which shares functional similarities with synaptopodin, was also elevated in Bazooka depleted nephrocytes. The simultaneous depletion of Bazooka and Tropomyosin2 resulted in a partial rescue of the Bazooka knockdown phenotype and prevented increased Rho1, a member of a GTPase protein family regulating the cytoskeleton. The latter contribute to the nephrocyte phenotype observed upon loss of Bazooka. Thus, we demonstrate that Par3 proteins share a high functional redundancy but also have specific functions. Par3A acts in an aPKC-Par6 dependent way and regulates RhoA-GTP levels, while Par3B exploits Par6 independent functions influencing synaptopodin localization. Hence, Par3A and Par3B link elements of polarity signaling and actin regulators to maintain podocyte architecture.
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Affiliation(s)
- Sybille Koehler
- Department II of Internal Medicine; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Biomedical Sciences, University of Edinburgh, Edinburgh, Scotland, UK.
| | - Johanna Odenthal
- Department II of Internal Medicine; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Vivian Ludwig
- Department II of Internal Medicine; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - David Unnersjö Jess
- Department II of Internal Medicine; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Martin Höhne
- Department II of Internal Medicine; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Christian Jüngst
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Ferdi Grawe
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; Molecular Cell Biology, Institute I for Anatomy, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Martin Helmstädter
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Johanna L Janku
- Department II of Internal Medicine; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Carsten Bergmann
- Medizinische Genetik Mainz, Limbach Genetics, Mainz, Germany; Department of Medicine, Nephrology, University Hospital Freiburg, Germany
| | - Peter F Hoyer
- Klinik für Kinderheilkunde 2, Zentrum für Kinder- und Jugendmedizin, Universitätsklinikum Essen, Essen, Germany
| | - H H Henning Hagmann
- Department II of Internal Medicine; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Gerd Walz
- Renal Division, Department of Medicine, Faculty of Medicine and Medical Center, University of Freiburg, Freiburg, Germany
| | - Wilhelm Bloch
- Department of Molecular and Cellular Sport Medicine, Institute of Cardiovascular Research and Sport Medicine, German Sport University Cologne, Cologne, Germany
| | - Carien Niessen
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; Department of Dermatology, University Hospital of Cologne, Cologne, Germany
| | - Bernhard Schermer
- Department II of Internal Medicine; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Andreas Wodarz
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; Molecular Cell Biology, Institute I for Anatomy, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Barry Denholm
- Biomedical Sciences, University of Edinburgh, Edinburgh, Scotland, UK
| | - Thomas Benzing
- Department II of Internal Medicine; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Sandra Iden
- Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany; Institute for Cell and Developmental Biology, Saarland University, Homburg/Saar, Germany
| | - Paul T Brinkkoetter
- Department II of Internal Medicine; Center for Molecular Medicine Cologne (CMMC), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany.
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Ballermann BJ, Nyström J, Haraldsson B. The Glomerular Endothelium Restricts Albumin Filtration. Front Med (Lausanne) 2021; 8:766689. [PMID: 34912827 PMCID: PMC8667033 DOI: 10.3389/fmed.2021.766689] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Accepted: 11/05/2021] [Indexed: 12/29/2022] Open
Abstract
Inflammatory activation and/or dysfunction of the glomerular endothelium triggers proteinuria in many systemic and localized vascular disorders. Among them are the thrombotic microangiopathies, many forms of glomerulonephritis, and acute inflammatory episodes like sepsis and COVID-19 illness. Another example is the chronic endothelial dysfunction that develops in cardiovascular disease and in metabolic disorders like diabetes. While the glomerular endothelium is a porous sieve that filters prodigious amounts of water and small solutes, it also bars the bulk of albumin and large plasma proteins from passing into the glomerular filtrate. This endothelial barrier function is ascribed predominantly to the endothelial glycocalyx with its endothelial surface layer, that together form a relatively thick, mucinous coat composed of glycosaminoglycans, proteoglycans, glycolipids, sialomucins and other glycoproteins, as well as secreted and circulating proteins. The glycocalyx/endothelial surface layer not only covers the glomerular endothelium; it extends into the endothelial fenestrae. Some glycocalyx components span or are attached to the apical endothelial cell plasma membrane and form the formal glycocalyx. Other components, including small proteoglycans and circulating proteins like albumin and orosomucoid, form the endothelial surface layer and are bound to the glycocalyx due to weak intermolecular interactions. Indeed, bound plasma albumin is a major constituent of the endothelial surface layer and contributes to its barrier function. A role for glomerular endothelial cells in the barrier of the glomerular capillary wall to protein filtration has been demonstrated by many elegant studies. However, it can only be fully understood in the context of other components, including the glomerular basement membrane, the podocytes and reabsorption of proteins by tubule epithelial cells. Discovery of the precise mechanisms that lead to glycocalyx/endothelial surface layer disruption within glomerular capillaries will hopefully lead to pharmacological interventions that specifically target this important structure.
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Affiliation(s)
| | - Jenny Nyström
- Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden
| | - Börje Haraldsson
- Institute of Neuroscience and Physiology, University of Gothenburg, Gothenburg, Sweden
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65
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Nephron overload as a therapeutic target to maximize kidney lifespan. Nat Rev Nephrol 2021; 18:171-183. [PMID: 34880459 DOI: 10.1038/s41581-021-00510-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2021] [Indexed: 12/27/2022]
Abstract
Kidney lifespan is a patient-oriented outcome that provides much needed context for understanding chronic kidney disease (CKD). Nephron endowment, age-associated decline in nephron number, kidney injury history and the intrinsic capacity of nephrons to adapt to haemodynamic and metabolic overload vary widely within the population. Defining percentiles of kidney function might therefore help to predict individual kidney lifespan and distinguish healthy ageing from progressive forms of CKD. In response to nephron loss, the remaining nephrons undergo functional and structural adaptations to meet the ongoing haemodynamic and metabolic demands of the organism. When these changes are no longer sufficient to maintain kidney cell homeostasis, remnant nephron demise occurs and CKD progression ensues. An individual's trajectory of glomerular filtration rate and albuminuria reflects the extent of nephron loss and adaptation of the remaining nephrons. Nephron overload represents the final common pathway of CKD progression and is largely independent of upstream disease mechanisms. Thus, interventions that efficiently attenuate nephron overload in early disease stages can protect remnant kidney cells and nephrons, and delay CKD progression. This Review provides a conceptual framework for individualized diagnosis, monitoring and treatment of CKD with the goal of maximizing kidney lifespan.
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66
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Unnersjö-Jess D, Ramdedovic A, Höhne M, Butt L, Koehler FC, Müller RU, Hoyer PF, Blom H, Schermer B, Benzing T. Three-Dimensional Super-Resolved Imaging of Paraffin-Embedded Kidney Samples. KIDNEY360 2021; 3:446-454. [PMID: 35582181 PMCID: PMC9034812 DOI: 10.34067/kid.0005882021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 11/30/2021] [Indexed: 01/10/2023]
Abstract
Background Diseases of the glomeruli, the renal filtration units, are a leading cause of progressive kidney disease. Assessment of the ultrastructure of podocytes at the glomerular filtration barrier is essential for diagnosing diverse disease entities, providing insight into the disease pathogenesis, and monitoring treatment responses. Methods Here we apply previously published sample preparation methods together with stimulated emission depletion and confocal microscopy for resolving nanoscale podocyte substructure. The protocols are modified and optimized in order to be applied to formalin-fixed paraffin-embedded (FFPE) samples. Results We successfully modified our protocols to allow for deep three-dimensional stimulated emission depletion and confocal imaging of FFPE kidney tissue with similar staining and image quality compared with our previous approaches. We further show that quantitative analysis can be applied to extract morphometrics from healthy and diseased samples from both mice and humans. Conclusions The results from this study could increase the feasibility of implementing optical kidney imaging protocols in clinical routines because FFPE is the gold-standard method for storage of patient samples.
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Affiliation(s)
- David Unnersjö-Jess
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Amer Ramdedovic
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Martin Höhne
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Linus Butt
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
| | - Felix C. Koehler
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Roman-Ulrich Müller
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Peter F. Hoyer
- Pediatric Nephrology, Pediatrics II, University of Duisburg-Essen, Essen, Germany
| | - Hans Blom
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Solna, Sweden
| | - Bernhard Schermer
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
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67
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Abstract
Morphological transitions are typically attributed to the actions of proteins and lipids. Largely overlooked in membrane shape regulation is the glycocalyx, a pericellular membrane coat that resides on all cells in the human body. Comprised of complex sugar polymers known as glycans as well as glycosylated lipids and proteins, the glycocalyx is ideally positioned to impart forces on the plasma membrane. Large, unstructured polysaccharides and glycoproteins in the glycocalyx can generate crowding pressures strong enough to induce membrane curvature. Stress may also originate from glycan chains that convey curvature preference on asymmetrically distributed lipids, which are exploited by binding factors and infectious agents to induce morphological changes. Through such forces, the glycocalyx can have profound effects on the biogenesis of functional cell surface structures as well as the secretion of extracellular vesicles. In this review, we discuss recent evidence and examples of these mechanisms in normal health and disease.
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Affiliation(s)
- Joe Chin-Hun Kuo
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA; ,
| | - Matthew J Paszek
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA; , .,Field of Biomedical Engineering and Field of Biophysics, Cornell University, Ithaca, New York 14853, USA.,Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA
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68
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The Atypical Cyclin-Dependent Kinase 5 (Cdk5) Guards Podocytes from Apoptosis in Glomerular Disease While Being Dispensable for Podocyte Development. Cells 2021; 10:cells10092464. [PMID: 34572114 PMCID: PMC8470701 DOI: 10.3390/cells10092464] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 09/10/2021] [Accepted: 09/13/2021] [Indexed: 12/03/2022] Open
Abstract
Cyclin-dependent kinase 5 (Cdk5) is expressed in terminally differentiated cells, where it drives development, morphogenesis, and survival. Temporal and spatial kinase activity is regulated by specific activators of Cdk5, dependent on the cell type and environmental factors. In the kidney, Cdk5 is exclusively expressed in terminally differentiated glomerular epithelial cells called podocytes. In glomerular disease, signaling mechanisms via Cdk5 have been addressed by single or combined conventional knockout of known specific activators of Cdk5. A protective, anti-apoptotic role has been ascribed to Cdk5 but not a developmental phenotype, as in terminally differentiated neurons. The effector kinase itself has never been addressed in animal models of glomerular disease. In the present study, conditional and inducible knockout models of Cdk5 were analyzed to investigate the role of Cdk5 in podocyte development and glomerular disease. While mice with podocyte-specific knockout of Cdk5 had no developmental defects and regular lifespan, loss of Cdk5 in podocytes increased susceptibility to glomerular damage in the nephrotoxic nephritis model. Glomerular damage was associated with reduced anti-apoptotic signals in Cdk5-deficient mice. In summary, Cdk5 acts primarily as master regulator of podocyte survival during glomerular disease and—in contrast to neurons—does not impact on glomerular development or maintenance.
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69
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Sever S. Role of actin cytoskeleton in podocytes. Pediatr Nephrol 2021; 36:2607-2614. [PMID: 33188449 PMCID: PMC8116355 DOI: 10.1007/s00467-020-04812-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 09/14/2020] [Accepted: 10/05/2020] [Indexed: 12/11/2022]
Abstract
The selectivity of the glomerular filter is established by physical, chemical, and signaling interplay among its three core constituents: glomerular endothelial cells, the glomerular basement membrane, and podocytes. Functional impairment or injury of any of these three components can lead to proteinuria. Podocytes are injured in many forms of human and experimental glomerular disease, including minimal change disease, focal segmental glomerulosclerosis, and diabetes mellitus. One of the earliest signs of podocyte injury is loss of their distinct structure, which is driven by dysregulated dynamics of the actin cytoskeleton. The status of the actin cytoskeleton in podocytes depends on a set of actin binding proteins, nucleators and inhibitors of actin polymerization, and regulatory GTPases. Mutations that alter protein function in each category have been implicated in glomerular diseases in humans and animal models. In addition, a growing body of studies suggest that pharmacological modifications of the actin cytoskeleton have the potential to become novel therapeutics for podocyte-dependent chronic kidney diseases. This review presents an overview of the essential proteins that establish actin cytoskeleton in podocytes and studies demonstrating the feasibility of drugging actin cytoskeleton in kidney diseases.
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Affiliation(s)
- Sanja Sever
- Harvard Medical School and Massachusetts General Hospital, Boston, MA, USA.
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70
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Höhfeld J, Benzing T, Bloch W, Fürst DO, Gehlert S, Hesse M, Hoffmann B, Hoppe T, Huesgen PF, Köhn M, Kolanus W, Merkel R, Niessen CM, Pokrzywa W, Rinschen MM, Wachten D, Warscheid B. Maintaining proteostasis under mechanical stress. EMBO Rep 2021; 22:e52507. [PMID: 34309183 PMCID: PMC8339670 DOI: 10.15252/embr.202152507] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 06/28/2021] [Accepted: 07/01/2021] [Indexed: 12/11/2022] Open
Abstract
Cell survival, tissue integrity and organismal health depend on the ability to maintain functional protein networks even under conditions that threaten protein integrity. Protection against such stress conditions involves the adaptation of folding and degradation machineries, which help to preserve the protein network by facilitating the refolding or disposal of damaged proteins. In multicellular organisms, cells are permanently exposed to stress resulting from mechanical forces. Yet, for long time mechanical stress was not recognized as a primary stressor that perturbs protein structure and threatens proteome integrity. The identification and characterization of protein folding and degradation systems, which handle force-unfolded proteins, marks a turning point in this regard. It has become apparent that mechanical stress protection operates during cell differentiation, adhesion and migration and is essential for maintaining tissues such as skeletal muscle, heart and kidney as well as the immune system. Here, we provide an overview of recent advances in our understanding of mechanical stress protection.
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Affiliation(s)
- Jörg Höhfeld
- Institute for Cell BiologyRheinische Friedrich‐Wilhelms University BonnBonnGermany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne (CMMC)University of CologneCologneGermany
| | - Wilhelm Bloch
- Institute of Cardiovascular Research and Sports MedicineGerman Sport UniversityCologneGermany
| | - Dieter O Fürst
- Institute for Cell BiologyRheinische Friedrich‐Wilhelms University BonnBonnGermany
| | - Sebastian Gehlert
- Institute of Cardiovascular Research and Sports MedicineGerman Sport UniversityCologneGermany
- Department for the Biosciences of SportsInstitute of Sports ScienceUniversity of HildesheimHildesheimGermany
| | - Michael Hesse
- Institute of Physiology I, Life & Brain CenterMedical FacultyRheinische Friedrich‐Wilhelms UniversityBonnGermany
| | - Bernd Hoffmann
- Institute of Biological Information Processing, IBI‐2: MechanobiologyForschungszentrum JülichJülichGermany
| | - Thorsten Hoppe
- Institute for GeneticsCologne Excellence Cluster on Cellular Stress Responses in Aging‐Associated Diseases (CECAD) and CMMCUniversity of CologneCologneGermany
| | - Pitter F Huesgen
- Central Institute for Engineering, Electronics and Analytics, ZEA3Forschungszentrum JülichJülichGermany
- CECADUniversity of CologneCologneGermany
| | - Maja Köhn
- Institute of Biology IIIFaculty of Biology, and Signalling Research Centres BIOSS and CIBSSAlbert‐Ludwigs‐University FreiburgFreiburgGermany
| | - Waldemar Kolanus
- LIMES‐InstituteRheinische Friedrich‐Wilhelms University BonnBonnGermany
| | - Rudolf Merkel
- Institute of Biological Information Processing, IBI‐2: MechanobiologyForschungszentrum JülichJülichGermany
| | - Carien M Niessen
- Department of Dermatology and CECADUniversity of CologneCologneGermany
| | | | - Markus M Rinschen
- Department of Biomedicine and Aarhus Institute of Advanced StudiesAarhus UniversityAarhusDenmark
- Department of MedicineUniversity Medical Center Hamburg‐EppendorfHamburgGermany
| | - Dagmar Wachten
- Institute of Innate ImmunityUniversity Hospital BonnBonnGermany
| | - Bettina Warscheid
- Institute of Biology IIFaculty of Biology, and Signalling Research Centres BIOSS and CIBSSAlbert‐Ludwigs‐University FreiburgFreiburgGermany
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Shen JX, Couchet M, Dufau J, de Castro Barbosa T, Ulbrich MH, Helmstädter M, Kemas AM, Zandi Shafagh R, Marques M, Hansen JB, Mejhert N, Langin D, Rydén M, Lauschke VM. 3D Adipose Tissue Culture Links the Organotypic Microenvironment to Improved Adipogenesis. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2021; 8:e2100106. [PMID: 34165908 PMCID: PMC8373086 DOI: 10.1002/advs.202100106] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 04/06/2021] [Indexed: 05/15/2023]
Abstract
Obesity and type 2 diabetes are strongly associated with adipose tissue dysfunction and impaired adipogenesis. Understanding the molecular underpinnings that control adipogenesis is thus of fundamental importance for the development of novel therapeutics against metabolic disorders. However, translational approaches are hampered as current models do not accurately recapitulate adipogenesis. Here, a scaffold-free versatile 3D adipocyte culture platform with chemically defined conditions is presented in which primary human preadipocytes accurately recapitulate adipogenesis. Following differentiation, multi-omics profiling and functional tests demonstrate that 3D adipocyte cultures feature mature molecular and cellular phenotypes similar to freshly isolated mature adipocytes. Spheroids exhibit physiologically relevant gene expression signatures with 4704 differentially expressed genes compared to conventional 2D cultures (false discovery rate < 0.05), including the concerted expression of factors shaping the adipogenic niche. Furthermore, lipid profiles of >1000 lipid species closely resemble patterns of the corresponding isogenic mature adipocytes in vivo (R2 = 0.97). Integration of multi-omics signatures with analyses of the activity profiles of 503 transcription factors using global promoter motif inference reveals a complex signaling network, involving YAP, Hedgehog, and TGFβ signaling, that links the organotypic microenvironment in 3D culture to the activation and reinforcement of PPARγ and CEBP activity resulting in improved adipogenesis.
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Affiliation(s)
- Joanne X. Shen
- Department of Physiology and PharmacologyKarolinska InstitutetStockholm171 77Sweden
| | - Morgane Couchet
- Department of MedicineHuddingeKarolinska InstitutetKarolinska University HospitalStockholm141 86Sweden
| | - Jérémy Dufau
- InsermInstitute of Metabolic and Cardiovascular Diseases (I2MC)UMR1297Toulouse31432France
- Université de ToulouseUniversité Paul SabatierFaculté de Médecine, I2MCUMR1297Toulouse31432France
| | - Thais de Castro Barbosa
- Department of MedicineHuddingeKarolinska InstitutetKarolinska University HospitalStockholm141 86Sweden
| | - Maximilian H. Ulbrich
- Renal DivisionDepartment of MedicineUniversity Hospital Freiburg and Faculty of MedicineUniversity of FreiburgFreiburg79106Germany
- BIOSS Centre for Biological Signalling StudiesUniversity of FreiburgFreiburg79104Germany
| | - Martin Helmstädter
- Renal DivisionDepartment of MedicineUniversity Hospital Freiburg and Faculty of MedicineUniversity of FreiburgFreiburg79106Germany
| | - Aurino M. Kemas
- Department of Physiology and PharmacologyKarolinska InstitutetStockholm171 77Sweden
| | - Reza Zandi Shafagh
- Department of Physiology and PharmacologyKarolinska InstitutetStockholm171 77Sweden
- Division of Micro‐ and NanosystemsKTH Royal Institute of TechnologyStockholm100 44Sweden
| | - Marie‐Adeline Marques
- InsermInstitute of Metabolic and Cardiovascular Diseases (I2MC)UMR1297Toulouse31432France
- Université de ToulouseUniversité Paul SabatierFaculté de Médecine, I2MCUMR1297Toulouse31432France
| | - Jacob B. Hansen
- Department of BiologyUniversity of CopenhagenCopenhagen2100Denmark
| | - Niklas Mejhert
- Department of MedicineHuddingeKarolinska InstitutetKarolinska University HospitalStockholm141 86Sweden
| | - Dominique Langin
- InsermInstitute of Metabolic and Cardiovascular Diseases (I2MC)UMR1297Toulouse31432France
- Université de ToulouseUniversité Paul SabatierFaculté de Médecine, I2MCUMR1297Toulouse31432France
- Toulouse University HospitalsDepartment of BiochemistryToulouse31079France
| | - Mikael Rydén
- Department of MedicineHuddingeKarolinska InstitutetKarolinska University HospitalStockholm141 86Sweden
| | - Volker M. Lauschke
- Department of Physiology and PharmacologyKarolinska InstitutetStockholm171 77Sweden
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Remuzzi A, Remuzzi G. Insights into Glomerular Filtration and Albuminuria. N Engl J Med 2021; 385:478. [PMID: 34320300 DOI: 10.1056/nejmc2108129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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73
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Butt L, Unnersjö-Jess D, Höhne M, Schermer B, Edwards A, Benzing T. A mathematical estimation of the physical forces driving podocyte detachment. Kidney Int 2021; 100:1054-1062. [PMID: 34332959 DOI: 10.1016/j.kint.2021.06.040] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 05/27/2021] [Accepted: 06/18/2021] [Indexed: 01/21/2023]
Abstract
Loss of podocytes, possibly through the detachment of viable cells, is a hallmark of progressive glomerular disease. Podocytes are exposed to considerable physical forces due to pressure and flow resulting in circumferential wall stress and tangential shear stress exerted on the podocyte cell body, which have been proposed to contribute to podocyte depletion. However, estimations of in vivo alterations of physical forces in glomerular disease have been hampered by a lack of quantitative functional and morphological data. Here, we used ultra-resolution data and computational analyses in a mouse model of human disease, hereditary late-onset focal segmental glomerular sclerosis, to calculate increased mechanical stress upon podocyte injury. Transversal shear stress on the lateral walls of the foot processes was prominently increased during the initial stages of podocyte detachment. Thus, our study highlights the importance of targeting glomerular hemodynamics to treat glomerular disease.
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Affiliation(s)
- Linus Butt
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - David Unnersjö-Jess
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Martin Höhne
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Bernhard Schermer
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; CECAD, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Aurelie Edwards
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany; CECAD, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany.
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Daehn IS, Duffield JS. The glomerular filtration barrier: a structural target for novel kidney therapies. Nat Rev Drug Discov 2021; 20:770-788. [PMID: 34262140 PMCID: PMC8278373 DOI: 10.1038/s41573-021-00242-0] [Citation(s) in RCA: 86] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/28/2021] [Indexed: 12/19/2022]
Abstract
Loss of normal kidney function affects more than 10% of the population and contributes to morbidity and mortality. Kidney diseases are currently treated with immunosuppressive agents, antihypertensives and diuretics with partial but limited success. Most kidney disease is characterized by breakdown of the glomerular filtration barrier (GFB). Specialized podocyte cells maintain the GFB, and structure-function experiments and studies of intercellular communication between the podocytes and other GFB cells, combined with advances from genetics and genomics, have laid the groundwork for a new generation of therapies that directly intervene at the GFB. These include inhibitors of apolipoprotein L1 (APOL1), short transient receptor potential channels (TRPCs), soluble fms-like tyrosine kinase 1 (sFLT1; also known as soluble vascular endothelial growth factor receptor 1), roundabout homologue 2 (ROBO2), endothelin receptor A, soluble urokinase plasminogen activator surface receptor (suPAR) and substrate intermediates for coenzyme Q10 (CoQ10). These molecular targets converge on two key components of GFB biology: mitochondrial function and the actin-myosin contractile machinery. This Review discusses therapies and developments focused on maintaining GFB integrity, and the emerging questions in this evolving field.
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Affiliation(s)
- Ilse S Daehn
- Department of Medicine, Division of Nephrology, The Icahn School of Medicine at Mount Sinai, New York, NY, USA.
| | - Jeremy S Duffield
- Research and Development, Prime Medicine, Cambridge, MA, USA. .,Department of Medicine, University of Washington, Seattle, WA, USA. .,Department of Medicine, Massachusetts General Hospital, Boston, MA, USA.
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Matsumoto A, Matsui I, Katsuma Y, Yasuda S, Shimada K, Namba-Hamano T, Sakaguchi Y, Kaimori JY, Takabatake Y, Inoue K, Isaka Y. Quantitative Analyses of Foot Processes, Mitochondria, and Basement Membranes by Structured Illumination Microscopy Using Elastica-Masson- and Periodic-Acid-Schiff-Stained Kidney Sections. Kidney Int Rep 2021; 6:1923-1938. [PMID: 34307987 PMCID: PMC8258503 DOI: 10.1016/j.ekir.2021.04.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2021] [Accepted: 04/16/2021] [Indexed: 11/28/2022] Open
Abstract
Introduction Foot process effacement and mitochondrial fission associate with kidney disease pathogenesis. Electron microscopy is the gold-standard method for their visualization, but the observable area of electron microscopy is smaller than light microscopy. It is important to develop alternative ways to quantitatively evaluate these microstructural changes because the lesion site of renal diseases can be focal. Methods We analyzed elastica-Masson trichrome (EMT) and periodic acid-Schiff (PAS) stained kidney sections using structured illumination microscopy (SIM). Results EMT staining revealed three-dimensional (3D) structures of foot process, whereas ponceau xylidine acid fuchsin azophloxine solution induced fluorescence. Conversion of foot process images into their constituent frequencies by Fourier transform showed that the concentric square of (1/4)2-(1/16)2 in the power spectra (PS) included information for normal periodic structures of foot processes. Foot process integrity, assessed by PS, negatively correlated with proteinuria. EMT-stained sections revealed fragmented mitochondria in mice with mitochondrial injuries and patients with tubulointerstitial nephritis; Fourier transform quantified associated mitochondrial injury. Quantified mitochondrial damage in patients with immunoglobulin A (IgA) nephropathy predicted a decline in estimated glomerular filtration rate (eGFR) after kidney biopsy but did not correlate with eGFR at biopsy. PAS-stained sections, excited by a 640 nm laser, combined with the coefficient of variation values, quantified subtle changes in the basement membranes of patients with membranous nephropathy stage I. Conclusions Kidney microstructures are quantified from sections prepared in clinical practice using SIM.
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Affiliation(s)
- Ayumi Matsumoto
- Department of Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Isao Matsui
- Department of Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yusuke Katsuma
- Department of Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Seiichi Yasuda
- Department of Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Karin Shimada
- Department of Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Tomoko Namba-Hamano
- Department of Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yusuke Sakaguchi
- Department of Inter-Organ Communication Research in Kidney Disease, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Jun-Ya Kaimori
- Department of Inter-Organ Communication Research in Kidney Disease, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yoshitsugu Takabatake
- Department of Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Kazunori Inoue
- Department of Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yoshitaka Isaka
- Department of Nephrology, Osaka University Graduate School of Medicine, Osaka, Japan
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Affiliation(s)
- Thomas Benzing
- From Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine, and University Hospital Cologne, and the Excellence Cluster CECAD, University of Cologne, Cologne, Germany (T.B.); and the Section of Nephrology, Department of Medicine, Boston Medical Center and Boston University School of Medicine, Boston (D.S.)
| | - David Salant
- From Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine, and University Hospital Cologne, and the Excellence Cluster CECAD, University of Cologne, Cologne, Germany (T.B.); and the Section of Nephrology, Department of Medicine, Boston Medical Center and Boston University School of Medicine, Boston (D.S.)
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Ziegler V, Fremter K, Helmchen J, Witzgall R, Castrop H. Mesangial cells regulate the single nephron GFR and preserve the integrity of the glomerular filtration barrier: An intravital multiphoton microscopy study. Acta Physiol (Oxf) 2021; 231:e13592. [PMID: 33269519 DOI: 10.1111/apha.13592] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 11/26/2020] [Accepted: 11/27/2020] [Indexed: 12/25/2022]
Abstract
AIM The intraglomerular mesangial cells are located between the glomerular capillaries. Here we hypothesized that mesangial cells regulate the single nephron glomerular filtration rate (snGFR) and that mesangial cells support the integrity of the glomerular filtration barrier. METHODS We assessed the function of mesangial cells in vivo by multiphoton microscopy. Mesangial cells were depleted in Munich Wistar Froemter rats using the Thy1.1 antibody model. RESULTS The Thy1.1 antibody caused the cell-specific loss of 82 ± 3% of mesangial cells. After mesangial cell depletion, the baseline snGFR was reduced to 12.0 ± 1.2 vs 32.4 ± 3.2 nL/min in controls. In control rats, the snGFR decreased after angiotensin II infusion by 61 ± 3% (P = .004), whereas it remained unchanged in Thy1.1-treated rats. The changes in the snGFR after angiotensin II infusion in control rats were accompanied by the marked rotation of the capillary loops within Bowman's space. This phenomenon was absent in anti-Thy1.1-treated rats. The glomerular sieving coefficient (GSCA ) for albumin, used as a measure of the integrity of the glomerular filtration barrier, was low in control rats (0.00061 ± 0.00004) and increased after angiotensin II infusion (0.00121 ± 0.00015). In Thy1.1-treated rats, the GSC was elevated (0.0032 ± 0.00059) and did not change in response to angiotensin II. Electron microscopy revealed the increased thickness of the glomerular basement membrane after mesangial cell depletion. CONCLUSION Our data suggest that mesangial cells actively contribute to the regulation of the snGFR. Furthermore, mesangial cells are crucially involved in maintaining the integrity of the glomerular filtration barrier, in part by modulating the thickness of the glomerular basement membrane.
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Affiliation(s)
- Vera Ziegler
- Institute of Physiology University of Regensburg Regensburg Germany
| | | | - Julia Helmchen
- Institute of Physiology University of Regensburg Regensburg Germany
| | - Ralph Witzgall
- Institute of Molecular and Cellular Anatomy University of Regensburg Regensburg Germany
| | - Hayo Castrop
- Institute of Physiology University of Regensburg Regensburg Germany
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Talyan S, Filipów S, Ignarski M, Smieszek M, Chen H, Kühne L, Butt L, Göbel H, Hoyer-Allo KJR, Koehler FC, Altmüller J, Brinkkötter P, Schermer B, Benzing T, Kann M, Müller RU, Dieterich C. CALINCA-A Novel Pipeline for the Identification of lncRNAs in Podocyte Disease. Cells 2021; 10:692. [PMID: 33804736 PMCID: PMC8003990 DOI: 10.3390/cells10030692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 03/13/2021] [Accepted: 03/15/2021] [Indexed: 11/16/2022] Open
Abstract
Diseases of the renal filtration unit-the glomerulus-are the most common cause of chronic kidney disease. Podocytes are the pivotal cell type for the function of this filter and focal-segmental glomerulosclerosis (FSGS) is a classic example of a podocytopathy leading to proteinuria and glomerular scarring. Currently, no targeted treatment of FSGS is available. This lack of therapeutic strategies is explained by a limited understanding of the defects in podocyte cell biology leading to FSGS. To date, most studies in the field have focused on protein-coding genes and their gene products. However, more than 80% of all transcripts produced by mammalian cells are actually non-coding. Here, long non-coding RNAs (lncRNAs) are a relatively novel class of transcripts and have not been systematically studied in FSGS to date. The appropriate tools to facilitate lncRNA research for the renal scientific community are urgently required due to a row of challenges compared to classical analysis pipelines optimized for coding RNA expression analysis. Here, we present the bioinformatic pipeline CALINCA as a solution for this problem. CALINCA automatically analyzes datasets from murine FSGS models and quantifies both annotated and de novo assembled lncRNAs. In addition, the tool provides in-depth information on podocyte specificity of these lncRNAs, as well as evolutionary conservation and expression in human datasets making this pipeline a crucial basis to lncRNA studies in FSGS.
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Affiliation(s)
- Sweta Talyan
- German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg/Mannheim, Im Neuenheimer Feld 669, 69120 Heidelberg, Germany;
- Section of Bioinformatics and Systems Cardiology, Klaus Tschira Institute for Integrative Computational Cardiology and Department of Internal Medicine III, Im Neuenheimer Feld 669, 69120 Heidelberg, Germany;
| | - Samantha Filipów
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Michael Ignarski
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Magdalena Smieszek
- Section of Bioinformatics and Systems Cardiology, Klaus Tschira Institute for Integrative Computational Cardiology and Department of Internal Medicine III, Im Neuenheimer Feld 669, 69120 Heidelberg, Germany;
| | - He Chen
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Lucas Kühne
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Linus Butt
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Heike Göbel
- Institute for Pathology, Diagnostic and Experimental Nephropathology Unit, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany;
| | - K. Johanna R. Hoyer-Allo
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Felix C. Koehler
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Janine Altmüller
- Cologne Center for Genomics, University of Cologne, 50931 Cologne, Germany;
| | - Paul Brinkkötter
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Bernhard Schermer
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Martin Kann
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Roman-Ulrich Müller
- Department II of Internal Medicine and Center for Molecular Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, 50931 Cologne, Germany; (S.F.); (M.I.); (H.C.); (L.K.); (L.B.); (K.J.R.H.-A.); (F.C.K.); (P.B.); (B.S.); (T.B.); (M.K.)
- Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany
| | - Christoph Dieterich
- German Center for Cardiovascular Research (DZHK), Partner Site Heidelberg/Mannheim, Im Neuenheimer Feld 669, 69120 Heidelberg, Germany;
- Section of Bioinformatics and Systems Cardiology, Klaus Tschira Institute for Integrative Computational Cardiology and Department of Internal Medicine III, Im Neuenheimer Feld 669, 69120 Heidelberg, Germany;
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Rogg M, Maier JI, Dotzauer R, Artelt N, Kretz O, Helmstädter M, Abed A, Sammarco A, Sigle A, Sellung D, Dinse P, Reiche K, Yasuda-Yamahara M, Biniossek ML, Walz G, Werner M, Endlich N, Schilling O, Huber TB, Schell C. SRGAP1 Controls Small Rho GTPases To Regulate Podocyte Foot Process Maintenance. J Am Soc Nephrol 2021; 32:563-579. [PMID: 33514561 PMCID: PMC7920176 DOI: 10.1681/asn.2020081126] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 11/15/2020] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Previous research demonstrated that small Rho GTPases, modulators of the actin cytoskeleton, are drivers of podocyte foot-process effacement in glomerular diseases, such as FSGS. However, a comprehensive understanding of the regulatory networks of small Rho GTPases in podocytes is lacking. METHODS We conducted an analysis of podocyte transcriptome and proteome datasets for Rho GTPases; mapped in vivo, podocyte-specific Rho GTPase affinity networks; and examined conditional knockout mice and murine disease models targeting Srgap1. To evaluate podocyte foot-process morphology, we used super-resolution microscopy and electron microscopy; in situ proximity ligation assays were used to determine the subcellular localization of the small GTPase-activating protein SRGAP1. We performed functional analysis of CRISPR/Cas9-generated SRGAP1 knockout podocytes in two-dimensional and three-dimensional cultures and quantitative interaction proteomics. RESULTS We demonstrated SRGAP1 localization to podocyte foot processes in vivo and to cellular protrusions in vitro. Srgap1fl/fl*Six2Cre but not Srgap1fl/fl*hNPHS2Cre knockout mice developed an FSGS-like phenotype at adulthood. Podocyte-specific deletion of Srgap1 by hNPHS2Cre resulted in increased susceptibility to doxorubicin-induced nephropathy. Detailed analysis demonstrated significant effacement of podocyte foot processes. Furthermore, SRGAP1-knockout podocytes showed excessive protrusion formation and disinhibition of the small Rho GTPase machinery in vitro. Evaluation of a SRGAP1-dependent interactome revealed the involvement of SRGAP1 with protrusive and contractile actin networks. Analysis of glomerular biopsy specimens translated these findings toward human disease by displaying a pronounced redistribution of SRGAP1 in FSGS. CONCLUSIONS SRGAP1, a podocyte-specific RhoGAP, controls podocyte foot-process architecture by limiting the activity of protrusive, branched actin networks. Therefore, elucidating the complex regulatory small Rho GTPase affinity network points to novel targets for potentially precise intervention in glomerular diseases.
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Affiliation(s)
- Manuel Rogg
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany,Department of Medicine IV, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Jasmin I. Maier
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Robert Dotzauer
- Department of Medicine IV, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Nadine Artelt
- Department of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
| | - Oliver Kretz
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Martin Helmstädter
- Department of Medicine IV, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Ahmed Abed
- Department of Medicine IV, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Alena Sammarco
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - August Sigle
- Department of Medicine IV, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany,Department of Urology, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Dominik Sellung
- Department of Medicine IV, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany,Department of Neurology, Heimer Institute for Muscle Research, University Hospital Bergmannsheil, Ruhr-University Bochum, Bochum, Germany
| | - Patrick Dinse
- Department of Medicine IV, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Karoline Reiche
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Mako Yasuda-Yamahara
- Department of Medicine IV, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany,Department of Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Martin L. Biniossek
- Institute of Molecular Medicine and Cell Research, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Gerd Walz
- Department of Medicine IV, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Martin Werner
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Nicole Endlich
- Department of Anatomy and Cell Biology, University Medicine Greifswald, Greifswald, Germany
| | - Oliver Schilling
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany
| | - Tobias B. Huber
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christoph Schell
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center – University of Freiburg, Freiburg, Germany,Berta-Ottenstein Program, Medical Faculty, Medical Center – University of Freiburg, Freiburg, Germany
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80
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EPB41L5 controls podocyte extracellular matrix assembly by adhesome-dependent force transmission. Cell Rep 2021; 34:108883. [PMID: 33761352 DOI: 10.1016/j.celrep.2021.108883] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 12/21/2020] [Accepted: 02/25/2021] [Indexed: 12/14/2022] Open
Abstract
The integrity of the kidney filtration barrier essentially relies on the balanced interplay of podocytes and the glomerular basement membrane (GBM). Here, we show by analysis of in vitro and in vivo models that a loss of the podocyte-specific FERM-domain protein EPB41L5 results in impaired extracellular matrix (ECM) assembly. By using quantitative proteomics analysis of the secretome and matrisome, we demonstrate a shift in ECM composition characterized by diminished deposition of core GBM components, such as LAMA5. Integrin adhesome proteomics reveals that EPB41L5 recruits PDLIM5 and ACTN4 to integrin adhesion complexes (IACs). Consecutively, EPB41L5 knockout podocytes show insufficient maturation of integrin adhesion sites, which translates into impaired force transmission and ECM assembly. These observations build the framework for a model in which EPB41L5 functions as a cell-type-specific regulator of the podocyte adhesome and controls a localized adaptive module in order to prevent podocyte detachment and thereby ensures GBM integrity.
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81
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The role of pulse pressure in navigating the paradigm of chronic kidney disease progression in type 2 diabetes mellitus. J Nephrol 2021; 34:1429-1444. [PMID: 33492590 DOI: 10.1007/s40620-020-00954-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 12/27/2020] [Indexed: 10/22/2022]
Abstract
BACKGROUND AND AIMS Arterial stiffness is a risk factor for chronic kidney disease progression (CKD). Pulse pressure is a surrogate marker of arterial stiffness. It is unclear if pulse pressure predicts CKD progression in type 2 diabetes mellitus. METHODS This was prospective study involving 1494 patients with estimated glomerular filtration rate (eGFR) ≥ 15 ml/min/1.73 m2. Carotid-femoral pulse wave velocity was measured using applanation tonometry. Pulse pressure was calculated as difference between systolic and diastolic blood pressures. CKD progression was defined as worsening of eGFR categories (stage 1, ≥ 90 ml/min/1.73 m2; stage 2, 60-89 ml/min/1.73 m2; stage 3a, 45-59 ml/min/1.73 m2; stage 3b, 30-44 ml/min/1.73 m2; stage 4; 15-29 ml/min/1.73 m2; and stage 5, < 15 ml/min/1.73 m2) with ≥ 25% decrease in eGFR from baseline. RESULTS After follow-up of up to 6 years, CKD progression occurred in 33.5% of subjects. Subjects in 2nd, 3rd and 4th quartiles of peripheral pulse pressure experienced higher risk of CKD progression with unadjusted hazard ratios (HRs) 1.55 [95% confidence interval (CI) 1.13-2.11; p = 0.006], 2.58 (1.93-3.45; p < 0.001) and 3.41 (2.58-4.52; p < 0.001). In the fully adjusted model, the association for 2nd, 3rd and 4th quartiles remained with HRs 1.40 (1.02-1.93; p = 0.038), 1.87 (1.37-2.56; p < 0.001) and 1.75 (1.25-2.44; p = 0.001) respectively. Similarly, 2nd, 3rd and 4th quartiles of aortic pulse pressure were associated with higher hazards of CKD progression with HRs 1.73 (1.25-2.40; p = 0.001), 1.65 (1.18-2.29; p = 0.003) and 1.81 (1.26-2.60; p = 0.001). Increasing urinary albumin-to-creatinine ratio accounted for 44.0% of the association between peripheral pulse pressure and CKD progression. CONCLUSIONS Individuals with high pulse pressure were more susceptible to deterioration of renal function. Pulse pressure could potentially be incorporated in clinical practice as an inexpensive and readily available biomarker of renal decline in type 2 diabetes mellitus. Graphic abstract.
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82
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Unnersjö-Jess D, Butt L, Höhne M, Witasp A, Kühne L, Hoyer PF, Patrakka J, Brinkkötter PT, Wernerson A, Schermer B, Benzing T, Scott L, Brismar H, Blom H. A fast and simple clearing and swelling protocol for 3D in-situ imaging of the kidney across scales. Kidney Int 2020; 99:1010-1020. [PMID: 33285146 DOI: 10.1016/j.kint.2020.10.039] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 10/02/2020] [Accepted: 10/15/2020] [Indexed: 11/29/2022]
Abstract
In recent years, many light-microscopy protocols have been published for visualization of nanoscale structures in the kidney. These protocols present researchers with new tools to evaluate both foot process anatomy and effacement, as well as protein distributions in foot processes, the slit diaphragm and in the glomerular basement membrane. However, these protocols either involve the application of different complicated super resolution microscopes or lengthy sample preparation protocols. Here, we present a fast and simple, five-hour long procedure for three-dimensional visualization of kidney morphology on all length scales. The protocol combines optical clearing and tissue expansion concepts to produce a mild swelling, sufficient for resolving nanoscale structures using a conventional confocal microscope. We show that the protocol can be applied to visualize a wide variety of pathologic features in both mouse and human kidneys. Thus, our fast and simple protocol can be beneficial for conventional microscopic evaluation of kidney tissue integrity both in research and possibly in future clinical routines.
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Affiliation(s)
- David Unnersjö-Jess
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Solna, Sweden; Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany.
| | - Linus Butt
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Martin Höhne
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Anna Witasp
- Division of Renal Medicine, Department of Clinical Sciences, Intervention, and Technology, Karolinska Institutet, Stockholm, Sweden
| | - Lucas Kühne
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Peter F Hoyer
- Pediatric Nephrology, Pediatrics II, University of Duisburg-Essen, Essen, Germany
| | - Jaakko Patrakka
- KI/AZ Integrated CardioMetabolic Center, Department of Laboratory Medicine, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Paul T Brinkkötter
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Annika Wernerson
- Division of Renal Medicine, Department of Clinical Sciences, Intervention, and Technology, Karolinska Institutet, Stockholm, Sweden; Clinical Pathology and Cytology, Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Bernhard Schermer
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany
| | - Lena Scott
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Solna, Sweden
| | - Hjalmar Brismar
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Solna, Sweden; Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institutet, Solna, Sweden
| | - Hans Blom
- Science for Life Laboratory, Department of Applied Physics, Royal Institute of Technology, Solna, Sweden
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83
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Yamada H, Shirata N, Makino S, Miyake T, Trejo JAO, Yamamoto-Nonaka K, Kikyo M, Empitu MA, Kadariswantiningsih IN, Kimura M, Ichimura K, Yokoi H, Mukoyama M, Hotta A, Nishimori K, Yanagita M, Asanuma K. MAGI-2 orchestrates the localization of backbone proteins in the slit diaphragm of podocytes. Kidney Int 2020; 99:382-395. [PMID: 33144214 DOI: 10.1016/j.kint.2020.09.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 08/22/2020] [Accepted: 09/10/2020] [Indexed: 01/19/2023]
Abstract
Podocytes are highly specialized cells within the glomerulus that are essential for ultrafiltration. The slit diaphragm between the foot processes of podocytes functions as a final filtration barrier to prevent serum protein leakage into urine. The slit-diaphragm consists mainly of Nephrin and Neph1, and localization of these backbone proteins is essential to maintaining the integrity of the glomerular filtration barrier. However, the mechanisms that regulate the localization of these backbone proteins have remained elusive. Here, we focused on the role of membrane-associated guanylate kinase inverted 2 (MAGI-2) in order to investigate mechanisms that orchestrate localization of slit-diaphragm backbone proteins. MAGI-2 downregulation coincided with a reduced expression of slit-diaphragm backbone proteins in human kidneys glomerular disease such as focal segmental glomerulosclerosis or IgA nephropathy. Podocyte-specific deficiency of MAGI-2 in mice abrogated localization of Nephrin and Neph1 independently of other scaffold proteins. Although a deficiency of zonula occuldens-1 downregulated the endogenous Neph1 expression, MAGI-2 recovered Neph1 expression at the cellular edge in cultured podocytes. Additionally, overexpression of MAGI-2 preserved Nephrin localization to intercellular junctions. Co-immunoprecipitation and pull-down assays also revealed the importance of the PDZ domains of MAGI-2 for the interaction between MAGI-2 and slit diaphragm backbone proteins in podocytes. Thus, localization and stabilization of Nephrin and Neph1 in intercellular junctions is regulated mainly via the PDZ domains of MAGI-2 together with other slit-diaphragm scaffold proteins. Hence, these findings may elucidate a mechanism by which the backbone proteins are maintained.
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Affiliation(s)
- Hiroyuki Yamada
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan; Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Naritoshi Shirata
- Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Sohyaku, Innovative Research Division, Mitsubishi Tanabe Pharmaceutical Corporation, Saitama, Japan
| | - Shinichi Makino
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan; Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Takafumi Miyake
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | | | - Kanae Yamamoto-Nonaka
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Mitsuhiro Kikyo
- Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Sohyaku, Innovative Research Division, Mitsubishi Tanabe Pharmaceutical Corporation, Saitama, Japan
| | - Maulana A Empitu
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | | | - Maiko Kimura
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan
| | - Koichiro Ichimura
- Department of Anatomy and Life Structure, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Hideki Yokoi
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
| | - Masashi Mukoyama
- Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Kumamoto, Japan
| | - Akitsu Hotta
- Department of Reprogramming Science, Center for iPS Cell Research and Application (CiRA), Kyoto University, Kyoto, Japan
| | - Katsuhiko Nishimori
- Department of Obesity and Inflammation Research, Fukushima Medical University, Fukushima, Japan
| | - Motoko Yanagita
- Department of Nephrology, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan; Institute for the Advanced Study of Human Biology (ASHBi), Kyoto University, Kyoto, Japan
| | - Katsuhiko Asanuma
- Department of Nephrology, Graduate School of Medicine, Chiba University, Chiba, Japan; Medical Innovation Center, TMK Project, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
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84
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Moeller MJ, Chia-Gil A. A step forward in understanding glomerular filtration. Nat Rev Nephrol 2020; 16:431-432. [PMID: 32601383 DOI: 10.1038/s41581-020-0313-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Marcus J Moeller
- Department of Nephrology and Clinical Immunology, RWTH Aachen University Clinic, Aachen, Germany.
| | - Arnaldo Chia-Gil
- Department of Nephrology and Clinical Immunology, RWTH Aachen University Clinic, Aachen, Germany
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Abstract
The glomerular basement membrane (GBM) is a key component of the glomerular capillary wall and is essential for kidney filtration. The major components of the GBM include laminins, type IV collagen, nidogens and heparan sulfate proteoglycans. In addition, the GBM harbours a number of other structural and regulatory components and provides a reservoir for growth factors. New technologies have improved our ability to study the composition and assembly of basement membranes. We now know that the GBM is a complex macromolecular structure that undergoes key transitions during glomerular development. Defects in GBM components are associated with a range of hereditary human diseases such as Alport syndrome, which is caused by defects in the genes COL4A3, COL4A4 and COL4A5, and Pierson syndrome, which is caused by variants in LAMB2. In addition, the GBM is affected by acquired autoimmune disorders and metabolic diseases such as diabetes mellitus. Current treatments for diseases associated with GBM involvement aim to reduce intraglomerular pressure and to treat the underlying cause where possible. As our understanding about the maintenance and turnover of the GBM improves, therapies to replace GBM components or to stimulate GBM repair could translate into new therapies for patients with GBM-associated disease.
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