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Khalil R, Boels MGS, van den Berg BM, Bruijn JA, Rabelink TJ, Hogendoorn PCW, Baelde HJ. Mutations in the heparan sulfate backbone elongating enzymes EXT1 and EXT2 have no major effect on endothelial glycocalyx and the glomerular filtration barrier. Mol Genet Genomics 2022; 297:397-405. [PMID: 35103870 PMCID: PMC8960589 DOI: 10.1007/s00438-022-01854-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 12/31/2021] [Indexed: 11/30/2022]
Abstract
In this study, the effect of heterozygous germline mutations in the heparan sulfate (HS) glycosaminoglycan chain co-polymerases EXT1 and EXT2 on glomerular barrier function and the endothelial glycocalyx in humans is investigated. Heparan sulfate (HS) glycosaminoglycans are deemed essential to the glomerular filtration barrier, including the glomerular endothelial glycocalyx. Animal studies have shown that loss of HS results in a thinner glycocalyx. Also, decreased glomerular HS expression is observed in various proteinuric renal diseases in humans. A case report of a patient with an EXT1 mutation indicated that this could result in a specific renal phenotype. This patient suffered from multiple osteochondromas, an autosomal dominant disease caused by mono-allelic germline mutations in the EXT1 or EXT2 gene. These studies imply that HS is indeed essential to the glomerular filtration barrier. However, loss of HS did not lead to proteinuria in various animal models. We demonstrate that multiple osteochondroma patients do not have more microalbuminuria or altered glycocalyx properties compared to age-matched controls (n = 19). A search for all Dutch patients registered with both osteochondroma and kidney biopsy (n = 39) showed that an EXT1 or EXT2 mutation does not necessarily lead to specific glomerular morphological phenotypic changes. In conclusion, this study shows that a heterozygous mutation in the HS backbone elongating enzymes EXT1 and EXT2 in humans does not result in (micro)albuminuria, a specific renal phenotype or changes to the endothelial glycocalyx, adding to the growing knowledge on the role of EXT1 and EXT2 genes in pathophysiology.
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Affiliation(s)
- Ramzi Khalil
- Department of Pathology, Leiden University Medical Center, L1Q, Room P0-107, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Margien G S Boels
- The Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, The Netherlands
| | - Bernard M van den Berg
- The Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jan A Bruijn
- Department of Pathology, Leiden University Medical Center, L1Q, Room P0-107, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Ton J Rabelink
- The Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, The Netherlands
| | - Pancras C W Hogendoorn
- Department of Pathology, Leiden University Medical Center, L1Q, Room P0-107, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Hans J Baelde
- Department of Pathology, Leiden University Medical Center, L1Q, Room P0-107, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
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van den Berg BM, Wang G, Boels MGS, Avramut MC, Jansen E, Sol WMPJ, Lebrin F, van Zonneveld AJ, de Koning EJP, Vink H, Gröne HJ, Carmeliet P, van der Vlag J, Rabelink TJ. Glomerular Function and Structural Integrity Depend on Hyaluronan Synthesis by Glomerular Endothelium. J Am Soc Nephrol 2019; 30:1886-1897. [PMID: 31308073 DOI: 10.1681/asn.2019020192] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 05/20/2019] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND A glycocalyx envelope consisting of proteoglycans and adhering proteins covers endothelial cells, both the luminal and abluminal surface. We previously demonstrated that short-term loss of integrity of the luminal glycocalyx layer resulted in perturbed glomerular filtration barrier function. METHODS To explore the role of the glycocalyx layer of the endothelial extracellular matrix in renal function, we generated mice with an endothelium-specific and inducible deletion of hyaluronan synthase 2 (Has2), the enzyme that produces hyaluronan, the main structural component of the endothelial glycocalyx layer. We also investigated the presence of endothelial hyaluronan in human kidney tissue from patients with varying degrees of diabetic nephropathy. RESULTS Endothelial deletion of Has2 in adult mice led to substantial loss of the glycocalyx structure, and analysis of their kidneys and kidney function showed vascular destabilization, characterized by mesangiolysis, capillary ballooning, and albuminuria. This process develops over time into glomerular capillary rarefaction and glomerulosclerosis, recapitulating the phenotype of progressive human diabetic nephropathy. Using a hyaluronan-specific probe, we found loss of glomerular endothelial hyaluronan in association with lesion formation in tissue from patients with diabetic nephropathy. We also demonstrated that loss of hyaluronan, which harbors a specific binding site for angiopoietin and a key regulator of endothelial quiescence and maintenance of EC barrier function results in disturbed angiopoietin 1 Tie2. CONCLUSIONS Endothelial loss of hyaluronan results in disturbed glomerular endothelial stabilization. Glomerular endothelial hyaluronan is a previously unrecognized key component of the extracelluar matrix that is required for glomerular structure and function and lost in diabetic nephropathy.
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Affiliation(s)
- Bernard M van den Berg
- The Einthoven Laboratory for Vascular and Regenerative Medicine, Division of Nephrology, Department of Internal Medicine, and
| | - Gangqi Wang
- The Einthoven Laboratory for Vascular and Regenerative Medicine, Division of Nephrology, Department of Internal Medicine, and
| | - Margien G S Boels
- The Einthoven Laboratory for Vascular and Regenerative Medicine, Division of Nephrology, Department of Internal Medicine, and
| | - M Cristina Avramut
- Section Electron Microscopy, Department of Cell and Chemical Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Erik Jansen
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Wendy M P J Sol
- The Einthoven Laboratory for Vascular and Regenerative Medicine, Division of Nephrology, Department of Internal Medicine, and
| | - Franck Lebrin
- The Einthoven Laboratory for Vascular and Regenerative Medicine, Division of Nephrology, Department of Internal Medicine, and
| | - Anton Jan van Zonneveld
- The Einthoven Laboratory for Vascular and Regenerative Medicine, Division of Nephrology, Department of Internal Medicine, and
| | - Eelco J P de Koning
- The Einthoven Laboratory for Vascular and Regenerative Medicine, Division of Nephrology, Department of Internal Medicine, and.,Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Hans Vink
- Department of Physiology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Hermann-Josef Gröne
- Department of Cellular and Molecular Pathology, The German Cancer Research Center, Heidelberg, Germany
| | - Peter Carmeliet
- Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology, Katholieke Universiteit Leuven, Vesalius Research Center, Vascular Institute Belgium, Leuven, Belgium.,Laboratory of Angiogenesis and Vascular Metabolism, Vesalius Research Center, Vascular Institute Belgium, Leuven, Belgium; and
| | - Johan van der Vlag
- Department of Nephrology, Nijmegen Centre for Molecular Life Sciences, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Ton J Rabelink
- The Einthoven Laboratory for Vascular and Regenerative Medicine, Division of Nephrology, Department of Internal Medicine, and
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Boels MGS, Koudijs A, Avramut MC, Sol WMPJ, Wang G, van Oeveren-Rietdijk AM, van Zonneveld AJ, de Boer HC, van der Vlag J, van Kooten C, Eulberg D, van den Berg BM, IJpelaar DHT, Rabelink TJ. Systemic Monocyte Chemotactic Protein-1 Inhibition Modifies Renal Macrophages and Restores Glomerular Endothelial Glycocalyx and Barrier Function in Diabetic Nephropathy. Am J Pathol 2017; 187:2430-2440. [PMID: 28837800 DOI: 10.1016/j.ajpath.2017.07.020] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 06/26/2017] [Accepted: 07/05/2017] [Indexed: 11/25/2022]
Abstract
Inhibition of monocyte chemotactic protein-1 (MCP-1) with the Spiegelmer emapticap pegol (NOX-E36) shows long-lasting albuminuria-reducing effects in diabetic nephropathy. MCP-1 regulates inflammatory cell recruitment and differentiation of macrophages. Because the endothelial glycocalyx is also reduced in diabetic nephropathy, we hypothesized that MCP-1 inhibition restores glomerular barrier function through influencing macrophage cathepsin L secretion, thus reducing activation of the glycocalyx-degrading enzyme heparanase. Four weeks of treatment of diabetic Apoe knockout mice with the mouse-specific NOX-E36 attenuated albuminuria without any change in systemic hemodynamics, despite persistent loss of podocyte function. MCP-1 inhibition, however, increased glomerular endothelial glycocalyx coverage, with preservation of heparan sulfate. Mechanistically, both glomerular cathepsin L and heparanase expression were reduced. MCP-1 inhibition resulted in reduced CCR2-expressing Ly6Chi monocytes in the peripheral blood, without affecting overall number of kidney macrophages at the tissue level. However, the CD206+/Mac3+ cell ratio, as an index of presence of anti-inflammatory macrophages, increased in diabetic mice after treatment. Functional analysis of isolated renal macrophages showed increased release of IL-10, whereas tumor necrosis factor and cathepsin L release was reduced, further confirming polarization of tissue macrophages toward an anti-inflammatory phenotype during mouse-specific NOX-E36 treatment. We show that MCP-1 inhibition restores glomerular endothelial glycocalyx and barrier function and reduces tissue inflammation in the presence of ongoing diabetic injury, suggesting a therapeutic potential for NOX-E36 in diabetic nephropathy.
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Affiliation(s)
- Margien G S Boels
- Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Angela Koudijs
- Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - M Cristina Avramut
- Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Wendy M P J Sol
- Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Gangqi Wang
- Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Annemarie M van Oeveren-Rietdijk
- Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Anton Jan van Zonneveld
- Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Hetty C de Boer
- Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Johan van der Vlag
- Department of Nephrology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Cees van Kooten
- Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | | | - Bernard M van den Berg
- Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Daphne H T IJpelaar
- Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Ton J Rabelink
- Einthoven Laboratory for Vascular and Regenerative Medicine, Department of Internal Medicine, Division of Nephrology, Leiden University Medical Center, Leiden, the Netherlands.
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Boels MGS, van Faassen EEH, Avramut MC, van der Vlag J, van den Berg BM, Rabelink TJ. Direct Observation of Enhanced Nitric Oxide in a Murine Model of Diabetic Nephropathy. PLoS One 2017; 12:e0170065. [PMID: 28103268 PMCID: PMC5245862 DOI: 10.1371/journal.pone.0170065] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 12/28/2016] [Indexed: 11/18/2022] Open
Abstract
Uncoupling of nitric oxide synthase (NOS) secondary to redox signaling is a central mechanism in endothelial and macrophage activation. To date studies on the production of nitric oxide (NO) during the development of diabetic complications show paradoxical results. We previously showed that recoupling eNOS by increasing the eNOS cofactor tetrahydrobiopterin (BH4) could restore endothelial function and prevent kidney injury in experimental kidney transplantation. Here, we employed a diabetic mouse model to investigate the effects of diabetes on renal tissue NO bioavailability. For this, we used in vivo NO trapping, followed by electron paramagnetic resonance spectroscopy. In addition, we investigated whether coupling of NOS by supplying the cofactor BH4 could restore glomerular endothelial barrier function. Our data show that overall NO availability at the tissue level is not reduced sixteen weeks after the induction of diabetes in apoE knockout mice, despite the presence of factors that cause endothelial dysfunction, and the presence of the endogenous NOS inhibitor ADMA. Targeting uncoupled NOS with the BH4 precursor sepiapterin further increases NO availability, but did not modify renal glomerular injury. Notably, glomerular heparanase activity as a driver for loss of glomerular barrier function was not reduced, pointing towards NOS-independent mechanisms. This was confirmed by unaltered increased glomerular presence of cathepsin L, the protease that activates heparanase.
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Affiliation(s)
- Margien G. S. Boels
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Internal Medicine (Nephrology), Leiden University Medical Center, Leiden, The Netherlands
- * E-mail:
| | - Ernst E. H. van Faassen
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Internal Medicine (Nephrology), Leiden University Medical Center, Leiden, The Netherlands
| | - M. Cristina Avramut
- Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Johan van der Vlag
- Department of Nephrology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Bernard M. van den Berg
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Internal Medicine (Nephrology), Leiden University Medical Center, Leiden, The Netherlands
| | - Ton J. Rabelink
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Internal Medicine (Nephrology), Leiden University Medical Center, Leiden, The Netherlands
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Boels MGS, Avramut MC, Koudijs A, Dane MJC, Lee DH, van der Vlag J, Koster AJ, van Zonneveld AJ, van Faassen E, Gröne HJ, van den Berg BM, Rabelink TJ. Atrasentan Reduces Albuminuria by Restoring the Glomerular Endothelial Glycocalyx Barrier in Diabetic Nephropathy. Diabetes 2016; 65:2429-39. [PMID: 27207530 DOI: 10.2337/db15-1413] [Citation(s) in RCA: 95] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 03/20/2016] [Indexed: 12/17/2022]
Abstract
Atrasentan, a selective endothelin A receptor antagonist, has been shown to reduce albuminuria in type 2 diabetes. We previously showed that the structural integrity of a glomerular endothelial glycocalyx is required to prevent albuminuria. Therefore we tested the potential of atrasentan to stabilize the endothelial glycocalyx in diabetic apolipoprotein E (apoE)-deficient mice in relation to its antialbuminuric effects. Treatment with atrasentan (7.5 mg/kg/day) for 4 weeks reduced urinary albumin-to-creatinine ratios by 26.0 ± 6.5% (P < 0.01) in apoE knockout (KO) mice with streptozotocin-induced diabetes consuming an atherogenic diet, without changes in gross glomerular morphology, systemic blood pressure, and blood glucose concentration. Endothelial cationic ferritin surface coverage, investigated using large-scale digital transmission electron microscopy, revealed that atrasentan treatment increases glycocalyx coverage in diabetic apoE KO mice from 40.7 ± 3.2% to 81.0 ± 12.5% (P < 0.05). This restoration is accompanied by increased renal nitric oxide concentrations, reduced expression of glomerular heparanase, and a marked shift in the balance of M1 and M2 glomerular macrophages. In vitro experiments with endothelial cells exposed to laminar flow and cocultured with pericytes confirmed that atrasentan reduced endothelial heparanase expression and increased glycocalyx thickness in the presence of a diabetic milieu. Together these data point toward a role for the restoration of endothelial function and tissue homeostasis through the antialbuminuric effects of atrasentan, and they provide a mechanistic explanation for the clinical observations of reduced albuminuria with atrasentan in diabetic nephropathy.
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Affiliation(s)
- Margien G S Boels
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - M Cristina Avramut
- Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Angela Koudijs
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Martijn J C Dane
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Dae Hyun Lee
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Johan van der Vlag
- Department of Nephrology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Abraham J Koster
- Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, the Netherlands
| | - Anton Jan van Zonneveld
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Ernst van Faassen
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Hermann-Josef Gröne
- Department of Cellular and Molecular Pathology, German Cancer Research Center, Heidelberg, Germany
| | - Bernard M van den Berg
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
| | - Ton J Rabelink
- Einthoven Laboratory for Experimental Vascular Medicine, Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands
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Dane MJC, van den Berg BM, Lee DH, Boels MGS, Tiemeier GL, Avramut MC, van Zonneveld AJ, van der Vlag J, Vink H, Rabelink TJ. A microscopic view on the renal endothelial glycocalyx. Am J Physiol Renal Physiol 2015; 308:F956-66. [PMID: 25673809 DOI: 10.1152/ajprenal.00532.2014] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 02/04/2015] [Indexed: 11/22/2022] Open
Abstract
Endothelial cells perform key homeostatic functions such as regulating blood flow, permeability, and aiding immune surveillance for pathogens. While endothelial activation serves normal physiological adaptation, maladaptation of these endothelial functions has been identified as an important effector mechanism in the progression of renal disease as well as the associated development of cardiovascular disease. The primary interface between blood and the endothelium is the glycocalyx. This carbohydrate-rich gel-like structure with its associated proteins mediates most of the regulatory functions of the endothelium. Because the endothelial glycocalyx is a highly dynamic and fragile structure ex vivo, and traditional tissue processing for staining and perfusion-fixation usually results in a partial or complete loss of the glycocalyx, studying its dimensions and function has proven to be challenging. In this review, we will outline the core functions of the glycocalyx and focus on different techniques to study structure-function relationships in kidney and vasculature.
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Affiliation(s)
- Martijn J C Dane
- Department of Nephrology, Einthoven laboratory for Vascular Medicine, LUMC, Leiden University Medical Center, Leiden, The Netherlands
| | - Bernard M van den Berg
- Department of Nephrology, Einthoven laboratory for Vascular Medicine, LUMC, Leiden University Medical Center, Leiden, The Netherlands
| | - Dae Hyun Lee
- Department of Nephrology, Einthoven laboratory for Vascular Medicine, LUMC, Leiden University Medical Center, Leiden, The Netherlands
| | - Margien G S Boels
- Department of Nephrology, Einthoven laboratory for Vascular Medicine, LUMC, Leiden University Medical Center, Leiden, The Netherlands
| | - Gesa L Tiemeier
- Department of Nephrology, Einthoven laboratory for Vascular Medicine, LUMC, Leiden University Medical Center, Leiden, The Netherlands
| | - M Cristina Avramut
- Department of Molecular Cell Biology, Section Electron Microscopy LUMC, Leiden University Medical Center, Leiden, The Netherlands
| | - Anton Jan van Zonneveld
- Department of Nephrology, Einthoven laboratory for Vascular Medicine, LUMC, Leiden University Medical Center, Leiden, The Netherlands
| | - Johan van der Vlag
- Department of Nephrology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands; and
| | - Hans Vink
- Department of Physiology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Ton J Rabelink
- Department of Nephrology, Einthoven laboratory for Vascular Medicine, LUMC, Leiden University Medical Center, Leiden, The Netherlands;
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Dane MJC, Khairoun M, Lee DH, van den Berg BM, Eskens BJM, Boels MGS, van Teeffelen JWGE, Rops ALWMM, van der Vlag J, van Zonneveld AJ, Reinders MEJ, Vink H, Rabelink TJ. Association of kidney function with changes in the endothelial surface layer. Clin J Am Soc Nephrol 2014; 9:698-704. [PMID: 24458084 DOI: 10.2215/cjn.08160813] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND AND OBJECTIVES ESRD is accompanied by endothelial dysfunction. Because the endothelial glycocalyx (endothelial surface layer) governs interactions between flowing blood and the vessel wall, perturbation could influence disease progression. This study used a novel noninvasive sidestream-darkfield imaging method, which measures the accessibility of red blood cells to the endothelial surface layer in the microcirculation (perfused boundary region), to investigate whether renal function is associated with endothelial surface layer dimensions. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Perfused boundary region was measured in control participants (n=10), patients with ESRD (n=23), participants with normal kidney function after successful living donor kidney transplantation (n=12), and patients who developed interstitial fibrosis/tubular atrophy after kidney transplantation (n=10). In addition, the endothelial activation marker angiopoietin-2 and shed endothelial surface layer components syndecan-1 and soluble thrombomodulin were measured using ELISA. RESULTS Compared with healthy controls (1.82 ± 0.16 µm), ESRD patients had a larger perfused boundary region (+0.23; 95% confidence interval, 0.46 to <0.01; P<0.05), which signifies loss of endothelial surface layer dimensions. This large perfused boundary region was accompanied by higher circulating levels of syndecan-1 (+57.71; 95% confidence interval, 17.38 to 98.04; P<0.01) and soluble thrombomodulin (+12.88; 95% confidence interval, 0.29 to 25.46; P<0.001). After successful transplantation, the perfused boundary region was indistinguishable from healthy controls (without elevated levels of soluble thrombomodulin or syndecan-1). In contrast, however, patients who developed interstitial fibrosis and tubular atrophy showed a large perfused boundary region (+0.36; 95% confidence interval, 0.09 to 0.63; P<0.01) and higher levels of endothelial activation markers. In addition, a significant correlation between perfused boundary region, angiopoietin-2, and eGFR was observed (perfused boundary region versus GFR: Spearman's ρ=0.31; P<0.05; perfused boundary region versus angiopoietin-2: Spearman's ρ=-0.33; P<0.05). CONCLUSION Reduced renal function is strongly associated with low endothelial surface layer dimensions. After successful kidney transplantation, the endothelial surface layer is indistinguishable from control.
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Affiliation(s)
- Martijn J C Dane
- Department of Nephrology, Einthoven Laboratory for Vascular Medicine, Leiden University Medical Center, Leiden, The Netherlands;, †Department of Physiology, Maastricht University Medical Center, Maastricht, The Netherlands, ‡Department of Nephrology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Boels MGS, Lee DH, van den Berg BM, Dane MJC, van der Vlag J, Rabelink TJ. The endothelial glycocalyx as a potential modifier of the hemolytic uremic syndrome. Eur J Intern Med 2013; 24:503-9. [PMID: 23357408 DOI: 10.1016/j.ejim.2012.12.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 12/19/2012] [Accepted: 12/20/2012] [Indexed: 12/22/2022]
Abstract
Atypical hemolytic uremic syndrome (HUS) is a renal disease due to complement dysregulation. Many of the known causes of atypical HUS originate from genetic mutations of complement regulatory proteins, such as complement factor H (CFH) and thrombomodulin. However, atypical HUS has only a genetic penetrance of 40-50% of the cases and usually appears in adulthood. We introduce a novel factor that may be involved in the onset and development of atypical HUS, i.e. the endothelial surface glycocalyx. The glycocalyx is a highly interactive matrix covering the luminal side of vascular endothelial cells and consists of glycosaminoglycans, proteoglycans and glycoproteins, which has an important role in maintaining homeostasis of the vasculature. The surface-bound glycocalyx glycosaminoglycan constituent heparan sulfate is crucial for CFH binding and function, both in recognition of host tissue and prevention of spontaneous complement activation via the alternative pathway. Most of the clinically relevant genetic mutations in CFH result in incorrect binding to heparan sulfate. In addition, a role between proper function of thrombomodulin and the endothelial glycocalyx has also been observed. We suggest that not only changes in binding properties of the complement regulatory proteins play a role but also changes in the endothelial glycocalyx are involved in increased risk of clinical manifestation of atypical HUS. Finally, vascular glycocalyx heterogeneity in turn could dictate the specific vulnerability of the glomerular vascular bed in atypical HUS and may provide new therapeutic targets to intervene with endothelial cell activation and local complement pathway regulation.
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Affiliation(s)
- Margien G S Boels
- Department of Nephrology, Einthoven Laboratory for Vascular Medicine, Leiden University Medical Center, PO Box 9600, 2300 RC, Leiden, The Netherlands
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