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O’Hare N, Millican K, Ebong EE. Unraveling neurovascular mysteries: the role of endothelial glycocalyx dysfunction in Alzheimer's disease pathogenesis. Front Physiol 2024; 15:1394725. [PMID: 39027900 PMCID: PMC11254711 DOI: 10.3389/fphys.2024.1394725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2024] [Accepted: 05/27/2024] [Indexed: 07/20/2024] Open
Abstract
While cardiovascular disease, cancer, and human immunodeficiency virus (HIV) mortality rates have decreased over the past 20 years, Alzheimer's Disease (AD) deaths have risen by 145% since 2010. Despite significant research efforts, effective AD treatments remain elusive due to a poorly defined etiology and difficulty in targeting events that occur too downstream of disease onset. In hopes of elucidating alternative treatment pathways, now, AD is commonly being more broadly defined not only as a neurological disorder but also as a progression of a variety of cerebrovascular pathologies highlighted by the breakdown of the blood-brain barrier. The endothelial glycocalyx (GCX), which is an essential regulator of vascular physiology, plays a crucial role in the function of the neurovascular system, acting as an essential vascular mechanotransducer to facilitate ultimate blood-brain homeostasis. Shedding of the cerebrovascular GCX could be an early indication of neurovascular dysfunction and may subsequently progress neurodegenerative diseases like AD. Recent advances in in vitro modeling, gene/protein silencing, and imaging techniques offer new avenues of scrutinizing the GCX's effects on AD-related neurovascular pathology. Initial studies indicate GCX degradation in AD and other neurodegenerative diseases and have begun to demonstrate a possible link to GCX loss and cerebrovascular dysfunction. This review will scrutinize the GCX's contribution to known vascular etiologies of AD and propose future work aimed at continuing to uncover the relationship between GCX dysfunction and eventual AD-associated neurological deterioration.
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Affiliation(s)
- Nicholas O’Hare
- Department of Chemical Engineering, Northeastern University, Boston, MA, United States
| | - Karina Millican
- Department of Bioengineering, Northeastern University, Boston, MA, United States
| | - Eno E. Ebong
- Department of Chemical Engineering, Northeastern University, Boston, MA, United States
- Department of Bioengineering, Northeastern University, Boston, MA, United States
- Department of Neuroscience, Albert Einstein College of Medicine, New York, NY, United States
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2
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Drost CC, Unger A, Linke WA, Vink H, Kümpers P. The dynamics of the endothelial glycocalyx: a rare snapshot by electron microscopy. Angiogenesis 2023; 26:487-491. [PMID: 37184739 PMCID: PMC10184622 DOI: 10.1007/s10456-023-09880-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 04/25/2023] [Indexed: 05/16/2023]
Affiliation(s)
- Carolin C Drost
- Department of Medicine D, Division of General Internal Medicine, Nephrology, and Rheumatology, University Hospital Münster, Münster, Germany.
| | - Andreas Unger
- Institute of Physiology II, University Hospital Münster, Münster, Germany
| | - Wolfgang A Linke
- Institute of Physiology II, University Hospital Münster, Münster, Germany
| | - Hans Vink
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
- Microvascular Health Solutions, Alpine, USA
| | - Philipp Kümpers
- Department of Medicine D, Division of General Internal Medicine, Nephrology, and Rheumatology, University Hospital Münster, Münster, Germany
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3
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Chatzimpinou A, Funaya C, Rogers D, O'Connor S, Kapishnikov S, Sheridan P, Fahy K, Weinhardt V. Dehydration as alternative sample preparation for soft X-ray tomography. J Microsc 2023; 291:248-255. [PMID: 37433616 DOI: 10.1111/jmi.13214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 06/26/2023] [Accepted: 07/09/2023] [Indexed: 07/13/2023]
Abstract
Soft X-ray tomography (SXT) is an imaging technique to visualise whole cells without fixation, staining, and sectioning. For SXT imaging, cells are cryopreserved and imaged at cryogenic conditions. Such 'near-to-native' state imaging is in high demand and initiated the development of the laboratory table-top SXT microscope. As many laboratories do not have access to cryogenic equipment, we asked ourselves whether SXT imaging is feasible on dry specimens. This paper shows how the dehydration of cells can be used as an alternative sample preparation to obtain ultrastructure information. We compare different dehydration processes on mouse embryonic fibroblasts in terms of ultrastructural preservation and shrinkage. Based on this analysis, we chose critical point (CPD) dried cells for SXT imaging. In comparison to cryopreserved and air-dried cells, CPD dehydrated cells show high structural integrity although with about 3-7 times higher X-ray absorption for cellular organelles. As the difference in X-ray absorption values between organelles is preserved, 3D anatomy of CPD-dried cells can be segmented and analysed, demonstrating the applicability of CPD-dried sample preparation for SXT imaging. LAY DESCRIPTION: Soft X-ray tomography (SXT) is an imaging technique that allows to see the internal structures of cells without the need for special treatments like fixation or staining. Typically, SXT imaging involves freezing and imaging cells at very low temperatures. However, since many labs lack the necessary equipment, we explored whether SXT imaging could be done on dry samples instead. We compared different dehydration methods and found that critical point drying (CPD) was the most promising for SXT imaging. CPD-dried cells showed high structural integrity, although they absorbed more X-rays than hydrated cells, demonstrating that CPD-dried sample preparation is a viable alternative for SXT imaging.
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Affiliation(s)
| | - Charlotta Funaya
- Electron Microscopy Core Facility (EMCF), Heidelberg University, Heidelberg, Germany
| | | | | | | | | | | | - Venera Weinhardt
- Centre for Organismal Studies (COS), Heidelberg University, Heidelberg, Germany
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4
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Correlative nano-imaging of metals and proteins in primary neurons by synchrotron X-ray fluorescence and STED super resolution microscopy: Experimental validation. J Neurosci Methods 2022; 381:109702. [PMID: 36064068 DOI: 10.1016/j.jneumeth.2022.109702] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 08/29/2022] [Accepted: 08/31/2022] [Indexed: 12/14/2022]
Abstract
BACKGROUND It is becoming increasingly clear that biological metals such as iron, copper or zinc are involved in synaptic functions, and in particular in the mechanisms of synaptogenesis and subsequent plasticity. Understanding the role of metals on synaptic functions is a difficult challenge due to the very low concentration of these elements in neurons and to the submicrometer size of synaptic compartments. NEW METHOD To address this challenge we have developed a correlative nano-imaging approach combining metal and protein detection. First, stimulated emission depletion (STED) microscopy, a super resolution optical microscopy technique, is applied to locate fluorescently labeled proteins. Then, synchrotron radiation induced X-ray fluorescence (SXRF) is performed on the same regions of interest, e.g. synaptic compartments. RESULTS We present here the principle scheme that allows this correlative nano-imaging and its experimental validation. We applied this correlative nano-imaging to the study of the physiological distribution of metals in synaptic compartments of primary rat hippocampal neurons. We thus compared the nanometric distribution of metals with that of synaptic proteins, such as PSD95 or cytoskeleton proteins. COMPARISON WITH EXISTING METHOD(S) Compared to correlative imaging approaches currently used to characterize synaptic structures, such as electron microscopy correlated with optical fluorescence, our approach allows for ultra-sensitive detection of trace metals using highly focused synchrotron radiation beams. CONCLUSION We provide proof-of-principle for correlative imaging of metals and proteins at the synaptic scale and discuss the present limitations and future developments in this area.
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Richter RP, Payne GA, Ambalavanan N, Gaggar A, Richter JR. The endothelial glycocalyx in critical illness: A pediatric perspective. Matrix Biol Plus 2022; 14:100106. [PMID: 35392182 PMCID: PMC8981764 DOI: 10.1016/j.mbplus.2022.100106] [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] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 02/28/2022] [Accepted: 03/01/2022] [Indexed: 12/18/2022] Open
Abstract
The vascular endothelium is the interface between circulating blood and end organs and thus has a critical role in preserving organ function. The endothelium is lined by a glycan-rich glycocalyx that uniquely contributes to endothelial function through its regulation of leukocyte and platelet interactions with the vessel wall, vascular permeability, coagulation, and vasoreactivity. Degradation of the endothelial glycocalyx can thus promote vascular dysfunction, inflammation propagation, and organ injury. The endothelial glycocalyx and its role in vascular pathophysiology has gained increasing attention over the last decade. While studies characterizing vascular glycocalyx injury and its downstream consequences in a host of adult human diseases and in animal models has burgeoned, studies evaluating glycocalyx damage in pediatric diseases are relatively few. As children have unique physiology that differs from adults, significant knowledge gaps remain in our understanding of the causes and effects of endothelial glycocalyx disintegrity in pediatric critical illness. In this narrative literature overview, we offer a unique perspective on the role of the endothelial glycocalyx in pediatric critical illness, drawing from adult and preclinical data in addition to pediatric clinical experience to elucidate how marked derangement of the endothelial surface layer may contribute to aberrant vascular biology in children. By calling attention to this nascent field, we hope to increase research efforts to address important knowledge gaps in pediatric vascular biology that may inform the development of novel therapeutic strategies.
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Key Words
- ACE2, angiotensin-converting enzyme 2
- CD, cell differentiation marker
- COVID-19, coronavirus disease 2019
- CPB, cardiopulmonary bypass
- CT, component therapy
- Children
- Critical illness
- DENV NS1, dengue virus nonstructural protein 1
- DM, diabetes mellitus
- ECLS, extracorporeal life support
- ECMO, extracorporeal membrane oxygenation
- EG, endothelial glycocalyx
- Endothelial glycocalyx
- FFP, fresh frozen plasma
- GAG, glycosaminoglycan
- GPC, glypican
- HPSE, heparanase
- HSV, herpes simplex virus
- IV, intravenous
- MIS-C, multisystem inflammatory syndrome in children
- MMP, matrix metalloproteinase
- Pragmatic, Randomized Optimal Platelet and Plasma Ratios
- RHAMM, receptor for hyaluronan-mediated motility
- S protein, spike protein
- SAFE, Saline versus Albumin Fluid Evaluation
- SARS-CoV-2, severe acute respiratory syndrome coronavirus 2
- SDC, syndecan
- SDF, sidestream darkfield
- SIRT1, sirtuin 1
- TBI, traumatic brain injury
- TBSA, total body surface area
- TMPRSS2, transmembrane protease serine 2
- Th2, type 2 helper T cell
- VSMC, vascular smooth muscle cell
- Vascular biology
- WB+CT, whole blood and component therapy
- eNOS, endothelial nitric oxide synthase
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Affiliation(s)
- Robert P. Richter
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA
- Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL, USA
- Center for Injury Science, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Gregory A. Payne
- Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Namasivayam Ambalavanan
- Department of Pediatrics, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
- Translational Research in Normal and Disordered Development Program, University of Alabama, Birmingham, AL, USA
| | - Amit Gaggar
- Program in Protease and Matrix Biology, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Jillian R. Richter
- Center for Injury Science, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Surgery, University of Alabama at Birmingham, Birmingham, AL, USA
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL, USA
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6
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The role of the cell surface glycocalyx in drug delivery to and through the endothelium. Adv Drug Deliv Rev 2022; 184:114195. [PMID: 35292326 DOI: 10.1016/j.addr.2022.114195] [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: 12/21/2021] [Revised: 02/05/2022] [Accepted: 03/08/2022] [Indexed: 11/20/2022]
Abstract
Cell membranes are key interfaces where materials engineering meets biology. Traditionally regarded as just the location of receptors regulating the uptake of molecules, we now know that all mammalian cell membranes are 'sugar coated'. These sugars, or glycans, form a matrix bound at the cell membrane via proteins and lipids, referred to as the glycocalyx, which modulate access to cell membrane receptors crucial for interactions with drug delivery systems (DDS). Focusing on the key blood-tissue barrier faced by most DDS to enable transport from the place of administration to target sites via the circulation, we critically assess the design of carriers for interactions at the endothelial cell surface. We also discuss the current challenges for this area and provide opportunities for future research efforts to more fully engineer DDS for controlled, efficient, and targeted interactions with the endothelium for therapeutic application.
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Stoddart P, Satchell SC, Ramnath R. Cerebral microvascular endothelial glycocalyx damage, its implications on the blood-brain barrier and a possible contributor to cognitive impairment. Brain Res 2022; 1780:147804. [DOI: 10.1016/j.brainres.2022.147804] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 01/21/2022] [Accepted: 01/24/2022] [Indexed: 12/31/2022]
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Haymet AB, Bartnikowski N, Wood ES, Vallely MP, McBride A, Yacoub S, Biering SB, Harris E, Suen JY, Fraser JF. Studying the Endothelial Glycocalyx in vitro: What Is Missing? Front Cardiovasc Med 2021; 8:647086. [PMID: 33937360 PMCID: PMC8079726 DOI: 10.3389/fcvm.2021.647086] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 03/19/2021] [Indexed: 12/16/2022] Open
Abstract
All human cells are coated by a surface layer of proteoglycans, glycosaminoglycans (GAGs) and plasma proteins, called the glycocalyx. The glycocalyx transmits shear stress to the cytoskeleton of endothelial cells, maintains a selective permeability barrier, and modulates adhesion of blood leukocytes and platelets. Major components of the glycocalyx, including syndecans, heparan sulfate, and hyaluronan, are shed from the endothelial surface layer during conditions including ischaemia and hypoxia, sepsis, atherosclerosis, diabetes, renal disease, and some viral infections. Studying mechanisms of glycocalyx damage in vivo can be challenging due to the complexity of immuno-inflammatory responses which are inextricably involved. Previously, both static as well as perfused in vitro models have studied the glycocalyx, and have reported either imaging data, assessment of barrier function, or interactions of blood components with the endothelial monolayer. To date, no model has simultaneously incorporated all these features at once, however such a model would arguably enhance the study of vasculopathic processes. This review compiles a series of current in vitro models described in the literature that have targeted the glycocalyx layer, their limitations, and potential opportunities for further developments in this field.
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Affiliation(s)
- Andrew B Haymet
- Critical Care Research Group, The Prince Charles Hospital, Chermside, QLD, Australia.,Faculty of Medicine, University of Queensland, St Lucia, QLD, Australia
| | - Nicole Bartnikowski
- Critical Care Research Group, The Prince Charles Hospital, Chermside, QLD, Australia.,Science and Engineering Faculty, Queensland University of Technology, Brisbane, QLD, Australia
| | - Emily S Wood
- Critical Care Research Group, The Prince Charles Hospital, Chermside, QLD, Australia.,Faculty of Medicine, University of Queensland, St Lucia, QLD, Australia
| | - Michael P Vallely
- Division of Cardiac Surgery, The Ohio State University Wexner Medical Center, Columbus, OH, United States
| | - Angela McBride
- Department of Global Health and Infection, Brighton and Sussex Medical School, Brighton, United Kingdom.,Oxford University Clinical Research Unit, Wellcome Trust Africa Asia Programme, Ho Chi Minh City, Vietnam
| | - Sophie Yacoub
- Oxford University Clinical Research Unit, Wellcome Trust Africa Asia Programme, Ho Chi Minh City, Vietnam.,Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, United Kingdom
| | - Scott B Biering
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, United States
| | - Eva Harris
- Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley, Berkeley, CA, United States
| | - Jacky Y Suen
- Critical Care Research Group, The Prince Charles Hospital, Chermside, QLD, Australia.,Faculty of Medicine, University of Queensland, St Lucia, QLD, Australia
| | - John F Fraser
- Critical Care Research Group, The Prince Charles Hospital, Chermside, QLD, Australia.,Faculty of Medicine, University of Queensland, St Lucia, QLD, Australia
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9
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Moore KH, Murphy HA, George EM. The glycocalyx: a central regulator of vascular function. Am J Physiol Regul Integr Comp Physiol 2021; 320:R508-R518. [PMID: 33501896 DOI: 10.1152/ajpregu.00340.2020] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The endothelial glycocalyx is a specialized extracellular matrix that covers the apical side of vascular endothelial cells, projecting into the lumen of blood vessels. The composition of the glycocalyx has been studied in great detail, and it is known to be composed of a mixture of proteoglycans, glycosaminoglycans, and glycoproteins. Although this structure was once believed to be a passive physical barrier, it is now recognized as a multifunctional and dynamic structure that participates in many vascular processes, including but not limited to vascular permeability, inflammation, thrombosis, mechanotransduction, and cytokine signaling. Because of its participation in many physiological and pathophysiological states, comprehensive knowledge of the glycocalyx will aid future vascular biologists in their research. With that in mind, this review discusses the biochemical structure of the glycocalyx and its function in many vascular physiological processes. We also briefly review a more recent discovery in glycocalyx biology, the placental glycocalyx.
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Affiliation(s)
- Kyle H Moore
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, Mississippi
| | - Hayley A Murphy
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, Mississippi
| | - Eric M George
- Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, Mississippi.,Department of Cell and Molecular Biology, University of Mississippi Medical Center, Jackson, Mississippi
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10
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Brandt R, Timm S, Gorenflos López JL, Kwame Abledu J, Kuebler WM, Hackenberger CPR, Ochs M, Lopez-Rodriguez E. Metabolic Glycoengineering Enables the Ultrastructural Visualization of Sialic Acids in the Glycocalyx of the Alveolar Epithelial Cell Line hAELVi. Front Bioeng Biotechnol 2021; 8:614357. [PMID: 33520965 PMCID: PMC7841390 DOI: 10.3389/fbioe.2020.614357] [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: 10/05/2020] [Accepted: 11/23/2020] [Indexed: 12/13/2022] Open
Abstract
The glycocalyx—a plethora of sugars forming a dense layer that covers the cell membrane—is commonly found on the epithelial surface of lumen forming tissue. New glycocalyx specific properties have been defined for various organs in the last decade. However, in the lung alveolar epithelium, its structure and functions remain almost completely unexplored. This is partly due to the lack of physiologically relevant, cost effective in vitro models. As the glycocalyx is an essential but neglected part of the alveolar epithelial barrier, understanding its properties holds the promise to enhance the pulmonary administration of drugs and delivery of nanoparticles. Here, using air-liquid-interface (ALI) cell culture, we focus on combining metabolic glycoengineering with glycan specific electron and confocal microscopy to visualize the glycocalyx of a recently immortalized human alveolar epithelial cell line (hAELVi). For this purpose, we applied different bioorthogonal labeling approaches to visualize sialic acid—an amino sugar that provides negative charge to the lung epithelial glycocalyx—using both fluorescence and gold-nanoparticle labeling. Further, we compared mild chemical fixing/freeze substitution and standard cytochemical electron microscopy embedding protocols for their capacity of contrasting the glycocalyx. In our study, we established hAELVi cells as a convenient model for investigating human alveolar epithelial glycocalyx. Transmission electron microscopy revealed hAELVi cells to develop ultrastructural features reminiscent of alveolar epithelial type II cells (ATII). Further, we visualized extracellular uni- and multilamellar membranous structures in direct proximity to the glycocalyx at ultrastructural level, indicating putative interactions. The lamellar membranes were able to form structures of higher organization, and we report sialic acid to be present within those. In conclusion, combining metabolite specific glycoengineering with ultrastructural localization presents an innovative method with high potential to depict the molecular distribution of individual components of the alveolar epithelial glycocalyx and its interaction partners.
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Affiliation(s)
- Raphael Brandt
- Institute of Functional Anatomy, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Sara Timm
- Core Facility Electron Microscopy, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jacob L Gorenflos López
- Department Chemical Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Department of Chemistry, Humboldt Universität zu Berlin, Berlin, Germany
| | | | - Wolfgang M Kuebler
- Institute of Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.,German Center for Lung Research (DZL), Berlin, Germany
| | - Christian P R Hackenberger
- Department Chemical Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany.,Department of Chemistry, Humboldt Universität zu Berlin, Berlin, Germany
| | - Matthias Ochs
- Institute of Functional Anatomy, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Core Facility Electron Microscopy, Charité - Universitätsmedizin Berlin, Berlin, Germany.,German Center for Lung Research (DZL), Berlin, Germany
| | - Elena Lopez-Rodriguez
- Institute of Functional Anatomy, Charité - Universitätsmedizin Berlin, Berlin, Germany
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