Glycocalyx Structure Research Articles

Ag/Cu nanoparticles-loaded glycocalyx biomimetic corneal bandage lenses for combatting bacterial keratitis

Bacterial keratitis is a major cause of blindness, hindered by the rising threat of antibiotic resistance. Although corneal bandage lenses (CBLs) are widely utilized in ophthalmic treatment, their effectiveness in treating bacterial keratitis remains limited due to risks of secondary infections, patient discomfort, and complications. In this study, we developed a novel biomimetic coating on CBLs by grafting Ag/Cu bimetallic nanoparticles (Ag/Cu-NPs) and thiol-functionalized heparin (Hep-SH) using a rapid polydopamine (PDA) deposition technique, effectively mimicking the ocular surface glycocalyx structure. The resulting Ag/Cu-NPs/Hep-SH coated CBLs (PNH-CBLs) exhibited significant antibacterial activity, with over 80 % reduction in Staphylococcus aureus (S. aureus) and 70 % in Escherichia coli (E. coli) due to the sustained release of Ag+ and Cu2+, along with displaying favorable in vitro biocompatibility. Animal experiments conducted on New Zealand white rabbits with bacterial keratitis demonstrated successful treatment therapeutic outcomes, with PNH-CBLs leading to a significant decrease in clinical score. These biomimetic lenses also exhibited selective anti-protein adsorption properties, minimizing inflammation and promoting surface lubrication. Overall, this innovative approach addresses critical challenges in antibiotic resistance and offers a promising therapeutic strategy for managing ophthalmic infectious diseases.

Evaluating glycocalyx morphology and composition in frozen and formalin-fixed liver tumor sections

BackgroundThe glycocalyx (GCX) is a glycan structure on the vascular endothelium and cancer cells. It is crucial for blood flow regulation, tumor invasion, and cancer drug resistance. Understanding the role of GCX in human tumors could help develop new cancer biomarkers and therapies. AimThis study aimed to demonstrate microstructural changes in human primary and metastatic liver tumors (henceforth termed liver tumors) by visualizing GCX using surgical specimens and comparing formalin-fixed paraffin-embedded sections (FFPEs) with frozen sections. The results of lectin staining were also compared between frozen and FFPE specimens to determine which was more useful for accurately assessing GCX structure and composition. MethodsLiver tumors and normal tissue samples from three patients were collected and processed into FFPEs and frozen sections, respectively. Lanthanum nitrate staining and scanning electron microscopy (SEM) were used to assess the GCX structures. Twenty lectins were analyzed for their glycan components in the samples. ResultsSEM revealed significant differences in GCX morphology among the cancer specimens. Frozen sections provided a more accurate GCX evaluation than FFPEs, showing distinct glycan compositions in hepatocellular carcinoma, colorectal carcinoma liver metastases, and melanoma liver metastases. Hepatocellular carcinoma samples exhibited a loss of N-acetylgalactosamine-related lectins. ConclusionThe results revealed that liver tumors have distinct and bulky GCX compared to normal liver tissue, while frozen sections are more reliable for GCX evaluation. These findings highlight glycan alterations in liver tumors and contribute to the development of new cancer therapies targeting GCX on tumor cell surfaces.

A comprehensive review of glycocalyx investigation and therapeutic applications in sepsis and septic shock

Abstract Background Sepsis is a global health challenge that causes more than 11 million deaths annually and represents a substantial medical and economic burden. With rising treatment costs and significant mortality rates associated with organ dysfunction and septic shock, research efforts have focused on investigating the mechanism of glycocalyx (GCX) degradation as well as its regenerative capacity. Therefore, GCX has become a target in therapeutic strategies. Methods We performed a comprehensive review of articles published in PubMed database between 2014 and 2024, in the English language, dealing with statistical data, morphological and physiological aspects of the GCX, pathophysiological mechanisms, in vivo and in vitro research methods, clinical and laboratory experiences, therapeutic strategies, and innovative methods of prevention, both in the context of sepsis and its associated complications. Results The database search identified 300 records on the topic. After title/abstract screening, 187 articles were assessed in full text for eligibility, including articles with additional topics addressing the main topic. Of these, a total of 70 studies were included. Conclusions Exploring the structure of GCX holds real potential in the diagnosis and treatment of sepsis and its complications. Current research focuses on understanding GCX degradation, correlating its components with sepsis severity, predicting disease progression, and evaluating the impact of therapeutic strategies on GCX components.

A Novel Drug Candidate for Sepsis Targeting Heparanase by Inhibiting Cytokine Storm.

Sepsis is an infection-triggered, rapidly progressive systemic inflammatory syndrome with a high mortality rate. Currently, there are no promising therapeutic strategies for managing this disease in the clinic. Heparanase plays a crucial role in the pathology of sepsis, and its inhibition can significantly relieve related symptoms. Here, a novel heparanase inhibitor CV122 is rationally designed and synthesized, and its therapeutic potential for sepsis with Lipopolysaccharide (LPS) and Cecal Ligation and Puncture (CLP)-induced sepsis mouse models are evaluated. It is found that CV122 potently inhibits heparanase activity in vitro, protects cell surface glycocalyx structure, and reduces the expression of adhesion molecules. In vivo, CV122 significantly reduces the systemic levels of proinflammatory cytokines, prevents organ damage, improves vitality, and efficiently protects mice from sepsis-induced death. Mechanistically, CV122 inhibits the activity of heparanase, reduces its expression in the lungs, and protects glycocalyx structure of lung tissue. It is also found that CV122 provides effective protection from organ damage and death caused by Crimean-Congo hemorrhagic fever virus (CCHFV) infection. These results suggest that CV122 is a potential drug candidate for sepsis therapy targeting heparanase by inhibiting cytokine storm.

Organ-on-a-Chip Approach for Accelerating Blood-Brain Barrier Nanoshuttle Discovery.

Organ-on-a-chip, which recapitulates the dynamics of in vivo vasculature, has emerged as a promising platform for studying organ-specific vascular beds. However, its practical advantages in identifying vascular-targeted drug delivery systems (DDS) over traditional in vitro models remain underexplored. This study demonstrates the reliability and efficacy of the organ-on-a-chip in screening efficient DDS by comparing its performance with that of a conventional transwell, both designed to simulate the blood-brain barrier (BBB). The BBB nanoshuttles discovered through BBB Chip-based screening demonstrated superior functionality in vivo compared to those identified using transwell methods. This enhanced effectiveness is attributed to the BBB Chip's accurate replication of the structure and dynamics of the endothelial glycocalyx, a crucial protective layer within blood vessels, especially under shear stress. This capability of the BBB Chip has enabled the identification of molecular shuttles that efficiently exploit the endothelial glycocalyx, thereby enhancing transendothelial transport efficacy. Our findings suggest that organ-on-a-chip technology holds considerable promise for advancing research in vascular-targeted DDS due to its accurate simulation of molecular transport within endothelial systems.

Podocyte glycocalyx plays an essential role in the function of GFB and the development of albumin leakage

The role of the cell surface layer, glycocalyx is emerging in various areas of cell biology including signaling, metabolism, and immune response. Although a decrease of podocyte glycocalyx depth in glomerular pathologies has been reported before, the specific role of specialized glycocalyx between the podocyte foot processes and the glomerular basement membrane (GBM) in the function and dysfunction of the glomerular filtration barrier (GFB) is elusive. Here we aimed to develop podocyte or endothelial glycocalyx targeting strategies to gain mechanistic understanding of the specific roles of the glycocalyx in the function of GFB and in the development of albumin leakage. Our overall hypothesis is that the specialized podocyte glycocalyx forms an important additional layer of the GFB and changes in the structure and composition of podocyte glycocalyx leads to GFB dysfunction and the development of albumin leakage. New genetic mouse models were generated by the knock-in of pCAG-Lox-STOP-Lox-EGFP-Sdc1 to generate animals with Cre-dependent expression of a syndecan-1 (Sdc1) fusion protein with N-terminal, extracellular GFP. Sdc1-GFPflox animals were crossed with either Podocin-Cre or Cdh5-Cre mice for the specific genetic labeling of the glycocalyx in podocytes or endothelial cells, respectively. Intravital multiphoton microscopy (MPM) was used to measure changes in the depth of glycocalyx and corresponding changes in GFB function in vivo over time. Endoglycosidase enzymes, such as hyaluronidase (50U/animal), heparinase (0.7 U/mouse), and chondroitinase (1 U/mouse) were used to acutely modify the composition of glycocalyx. Alexa-680 conjugated wheat germ agglutinin (WGA) lectin was used to label the glycosaminoglycan (GAG) component of the glycocalyx; Alexa-594 conjugated albumin was used to visualize GFB permeability. Classic phenotyping of Pod and Cdh5 Sdc1-GFP animals showed no significant difference in terms of systolic blood pressure, glomerular filtration rate, body and kidney weight between the Sdc1-GFP and wild type littermates. The co-localization of the genetic GFP and anti-podocin immunofluorescence co-staining confirmed the podocyte-specific expression of Sdc1-GFP. In vivo MPM imaging of Pod-Sdc1-GFP mouse kidneys revealed intense linear labeling of the podocyte cell surface including the apical and basolateral surfaces of the cell body as well as the surfaces of primary, secondary, and foot processes. Interestingly, the thickness and fluorescence intensity of Sdc1-GFP labeled glycocalyx was greater on the basal surface of the podocyte at the GBM as compared to the apical surface implying the role of glycocalyx in the function of GFB. In addition, labeling of the basolateral surface of the podocyte cell body and podocyte foot processes enabled the visualization of sub-podocyte space. Acute injection of endoglycosidase enzymes significantly (3-fold) reduced Sdc1-GFP fluorescence intensity and the thickness of the linear labeling suggesting the acute shedding of podocyte glycocalyx. Importantly, increased albumin permeability of the GFB was observed simultaneously with the shedding of podocyte glycocalyx, indicating the disruption of GFB charge and size-selective functions. In conclusion, the specialized podocyte glycocalyx at the GBM may function as an important new layer of the GFB and may play an important role in the disruption of GFB functions in disease. ASN Carl W. Gottschalk Research Scholar Grant University of Southern California Dean's Pilot Project Award DK123564. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Multivalent, calcium-independent binding of surfactant protein A and D to sulfated glycosaminoglycans of the alveolar epithelial glycocalyx.

Lung surfactant collectins, surfactant protein A (SP-A) and D (SP-D), are oligomeric C-type lectins involved in lung immunity. Through their carbohydrate recognition domain, they recognize carbohydrates at pathogen surfaces and initiate lung innate immune response. Here, we propose that they may also be able to bind to other carbohydrates present in typical cell surfaces, such as the alveolar epithelial glycocalyx. To test this hypothesis, we analyzed and quantified the binding affinity of SP-A and SP-D to different sugars and glycosaminoglycans (GAGs) by microscale thermophoresis (MST). In addition, by changing the calcium concentration, we aimed to characterize any consequences on the binding behavior. Our results show that both oligomeric proteins bind with high affinity (in nanomolar range) to GAGs, such as hyaluronan (HA), heparan sulfate (HS) and chondroitin sulfate (CS). Binding to HS and CS was calcium-independent, as it was not affected by changing calcium concentration in the buffer. Quantification of GAGs in bronchoalveolar lavage (BAL) fluid from animals deficient in either SP-A or SP-D showed changes in GAG composition, and electron micrographs showed differences in alveolar glycocalyx ultrastructure in vivo. Taken together, SP-A and SP-D bind to model sulfated glycosaminoglycans of the alveolar epithelial glycocalyx in a multivalent and calcium-independent way. These findings provide a potential mechanism for SP-A and SP-D as an integral part of the alveolar epithelial glycocalyx binding and interconnecting free GAGs, proteoglycans, and other glycans in glycoproteins, which may influence glycocalyx composition and structure.NEW & NOTEWORTHY SP-A and SP-D function has been related to innate immunity of the lung based on their binding to sugar residues at pathogen surfaces. However, their function in the healthy alveolus was considered as limited to interaction with surfactant lipids. Here, we demonstrated that these proteins bind to glycosaminoglycans present at typical cell surfaces like the alveolar epithelial glycocalyx. We propose a model where these proteins play an important role in interconnecting alveolar epithelial glycocalyx components.

EFFECT OF MIR-21-3P ON INTESTINAL INJURY IN RATS WITH TRAUMATIC HEMORRHAGIC SHOCK RESUSCITATED WITH THE SODIUM BICARBONATE RINGER'S SOLUTION.

Background : This study aims to determine the impact and mechanism of miR-21-3p on intestinal injury and intestinal glycocalyx during fluid resuscitation in traumatic hemorrhagic shock (THS), and the different impacts of sodium lactate Ringer's solution (LRS) and sodium bicarbonate Ringer's solution (BRS) for resuscitation on intestinal damage. Methods : A rat model of THS was induced by hemorrhage from the left femur fracture. The pathological changes of intestinal tissues and glycocalyx structure were observed by hematoxylin-eosin staining and transmission electron microscope. MiR-21-3p expression in intestinal tissues was detected by real-time quantitative polymerase chain reaction. The expression of glycocalyx-, cell junction-, and PI3K/Akt/NF-κB signaling pathway-related proteins was analyzed by western blot. Results : MiR-21-3p expression was increased in THS rats, which was suppressed by resuscitation with BRS. BRS or LRS aggravated the intestinal injury and damaged intestinal glycocalyx in THS rats. The expression of SDC-1, HPA, β-catenin, MMP2, and MMP9 was upregulated, the expression of E-cad was downregulated, and the PI3K/Akt/NF-κB signaling pathway was activated in THS rats, which were further aggravated by BRS or LRS. The adverse effect of LRS was more serious than BRS. MiR-21-3p overexpression deteriorated the injury of intestinal tissues and intestinal glycocalyx; increased the expression of SDC-1, HPA, β-catenin, MMP2, and MMP9 while decreasing E-cad expression; and activated the PI3K/Akt/NF-κB signaling pathway in BRS-resuscitated THS rats. Conclusion : MiR-21-3p aggravated intestinal tissue injury and intestinal glycocalyx damage through activating PI3K/Akt/NF-κB signaling pathway in rats with THS resuscitated with BRS.

Vasoprotective Effect of Sulodexide in Diabetic Retinopathy

Diabetes is a group of metabolic diseases, considered a lifestyle disease. Diabetic retinopathy is the leading cause of blindness in working-age adults worldwide. Pathogenetically, due to the changed anionic charge, collagen gradually replaces glycosaminoglycans (GAG) in the basement membrane of retinal capillaries, affecting vascular permeability. Clinically, these changes cause leakage from the retinal capillaries, which leads to the development of microaneurysms and, consequently, the formation of hard effusions (HE). Sulodexide is a glycosaminoglycan containing 80% of small molecular weight, fast moving heparin fraction (FMH) and 20% of dermatan sulfate. An important target of sulodexide's action are vascular endothelial cells, and its protective effect is partially related to the preservation and reconstruction of the glycocalyx structure on the surface of the endothelial layer cells. Additionally, sulodexide has been documented to strengthen the glycocalyx of retinal arterioles in people with diabetes. These findings suggest that sulodexide holds promise as a potential therapeutic agent for the treatment of diabetic retinopathy.

Effect of sodium bicarbonate Ringer's solution on lung injury in rats with traumatic hemorrhagic shock.

This study aimed to explore the impact of different pH values of resuscitation fluid on traumatic hemorrhagic shock (THS),focusing on their effects on glycocalyx and inflammation. A rat model of THS was induced by hemorrhage from a left femur fracture, while an oxygen-glucose deprivation/reoxygenation (OGD/R)-induced HULEC-5acell model was considered as an in vitro THSmodel. The lung tissue pathology and glycocalyx structure were assessed through hematoxylin-eosin (H&E) staining and transmission electron microscope examination. The levels of glycocalyx-related factors and inflammation-related factors were determined by enzyme-linked immunosorbent assay (ELISA).The expression of glycocalyx-related proteins, cell junction-related proteins, and proteins involved in the PI3K/Akt/NF-κB signaling pathway was analyzed by western blot. The results showed that both sodium bicarbonate Ringer's solution (BRS)and lactate Ringer's solution (LRS)were effective in restoring mean arterial pressure and heart rate in THS rats. However, LRS has a stronger impact on promoting inflammation and damaging the glycocalyx compared withBRS. In OGD/R-induced HULEC-5a cells, a pH of 7.4 and 6.5 increased inflammation and disrupted the glycocalyx, while a pH of 8.1 had no significant effect on inflammation or glycocalyx. Furthermore, the PI3K/Akt/NF-κBsignaling pathway was activated by fluid resuscitation and different pH values. However, the activating effect of BRS and pH 8.1 on the PI3K/Akt/NF-κBsignaling pathway was milder compared withLRS and pH6.5. In conclusion, an alkaline recovery environment was more beneficial for the treatment of THS.

Microvascular Endothelial Glycocalyx Surface Layer Visualization and Quantification.

As a primary interface between the blood and underlying vascular wall, the endothelial glycocalyx layer is common to all blood vessels and covers the luminal surface of all endothelial cells. The endothelial glycocalyx has important roles as a regulator of microvascular endothelial functions such as mechanotransduction, leukocyte adhesion, and microvascular permeability. Disruption of the molecular structure of the endothelial glycocalyx disturbs physiological, and hemodynamic processes associated with the microvascular wall leads to microvascular hyperpermeability. Studying the glycocalyx is challenging because cultured cells present aberrant glycocalyx structure and tissue fixation techniques lead to the degradation and loss of this fine and delicate layer. Therefore, studying the glycocalyx requires in vivo imaging of the microcirculation. Here we describe two techniques for direct imaging and assessment of the glycocalyx surface layer integrity using intravital microscopy (IVM), a method widely used in the study of the dynamic changes that occur in the microcirculation during inflammation or injury.

Heat stress combined with lipopolysaccharide induces pulmonary microvascular endothelial cell glycocalyx inflammatory damage in vitro.

Heat stroke is a life-threatening disease with high mortality and complications. Endothelial glycocalyx (EGCX) is essential for maintaining endothelial cell structure and function as well as preventing theadhesion of inflammatory cells. Potential relationship that underlies the imbalance in inflammation and coagulation remains elusive. Moreover, the role of EGCX in heat stroke-induced organ injury remained unclear. Therefore, the current study aimed to illustrate if EGCX aggravates apoptosis, inflammation, and oxidative damage in human pulmonary microvascular endothelial cells (HPMEC). Heat stress and lipopolysaccharide (LPS) were employed to construct in vitro models to study the changes of glycocalyx structure and function, as well as levels of heparansulfate proteoglycan (HSPG), syndecan-1 (SDC-1), heparansulfate (HS), tumor necrosis factor-α (TNF-α), interleukin (IL)-6, Von Willebrand factor (vWF), endothelin-1 (ET-1), occludin, E-selectin, vascular cell adhesion molecule-1 (VCAM-1), and reactive oxygen species (ROS). Here, we showed that heat stress and LPS devastated EGCX structure, activated EGCX degradation, and triggered oxidative damage and apoptosis in HPMEC. Stimulation of heat stress and LPS decreased expression of HSPG, increased levels of SDC-1 and HS in culture supernatant, promoted the production and release of proinflammation cytokines (TNF-α and IL-6,) and coagulative factors (vWF and ET-1) in HPMEC. Furthermore, Expressions of E-selection, VCAM-1, and ROS were upregulated, while that of occludin was downregulated. These changes could be deteriorated by heparanase, whereas they meliorated by unfractionated heparin. This study indicated that EGCX may contribute to apoptosis and heat stroke-induced coagulopathy, and these effects may have been due to the decrease in the shedding of EGCX.

The Pulmonary Endothelial Glycocalyx Modifications in Glypican 1 Knockout Mice Do Not Affect Lung Endothelial Function in Physiological Conditions.

The endothelial glycocalyx is a dynamic signaling surface layer that is involved in the maintenance of cellular homeostasis. The glycocalyx has a very diverse composition, with glycoproteins, proteoglycans, and glycosaminoglycans interacting with each other to form a mesh-like structure. Due to its highly interactive nature, little is known about the relative contribution of each glycocalyx constituent to its overall function. Investigating the individual roles of the glycocalyx components to cellular functions and system physiology is challenging, as the genetic manipulation of animals that target specific glycocalyx components may result in the development of a modified glycocalyx. Thus, it is crucial that genetically modified animal models for glycocalyx components are characterized and validated before the development of mechanistic studies. Among the glycocalyx components, glypican 1, which acts through eNOS-dependent mechanisms, has recently emerged as a player in cardiovascular diseases. Whether glypican 1 regulates eNOS in physiological conditions is unclear. Herein, we assessed how the deletion of glypican 1 affects the development of the pulmonary endothelial glycocalyx and the impact on eNOS activity and endothelial function. Male and female 5-9-week-old wild-type and glypican 1 knockout mice were used. Transmission electron microscopy, immunofluorescence, and immunoblotting assessed the glycocalyx structure and composition. eNOS activation and content were assessed by immunoblotting; nitric oxide production was assessed by the Griess reaction. The pulmonary phenotype was evaluated by histological signs of lung injury, in vivo measurement of lung mechanics, and pulmonary ventilation. Glypican 1 knockout mice showed a modified glycocalyx with increased glycocalyx thickness and heparan sulfate content and decreased expression of syndecan 4. These alterations were associated with decreased phosphorylation of eNOS at S1177. The production of nitric oxides was not affected by the deletion of glypican 1, and the endothelial barrier was preserved in glypican 1 knockout mice. Pulmonary compliance was decreased, and pulmonary ventilation was unaltered in glypican 1 knockout mice. Collectively, these data indicate that the deletion of glypican 1 may result in the modification of the glycocalyx without affecting basal lung endothelial function, validating this mouse model as a tool for mechanistic studies that investigate the role of glypican 1 in lung endothelial function.

A nitric oxide-catalytically generating carboxymethyl chitosan/sodium alginate hydrogel coating mimicking endothelium function for improving the biocompatibility

Thanks to their outstanding mechanical properties and corrosion resistance in physiological environments, titanium and its alloys are broadly explored in the field of intravascular devices. However, the biocompatibility is insufficient, causing thrombus formation and even implantation failure. In this study, inspired by the functions of endothelial glycocalyx and the NO-releasing of endothelial cells (ECs), a biomimetic coating (TNTA-Se) with three-dimensional gel-like structures and NO-catalytically generating ability was constructed on the titanium surface. To this end, the titanium alloy was firstly anodized and then annealed to form nanotube structures imitating the three-dimensional villous of glycocalyx, followed by the preparation of the Cu2+-loaded polydopamine intermediate layer for the immobilization of carboxymethyl chitosan and sodium alginate to form the hydrogel structure. Finally, an organoselenium compound (selenocystamine) as an active catalyst was covalently immobilized on the surface to develop a bioactive coating mimicking endothelial function with NO-generating activity. The surface morphologies and chemical structures of the biomimetic coating were characterized by scanning electron microscopy (SEM), energy dispersion X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and the results indicated that the NO-catalytically generating hydrogel coating was successfully constructed. The results of water contact angle and protein adsorption suggested that the TNTA-Se coating exhibited excellent hydrophilicity, the promotion of bovine serum albumin (BSA) adsorption while the inhibition of fibrinogen (FIB) adsorption. Upon the addition of NO donor S-nitroso glutathione (GSNO) and reducing agent glutathione (GSH), the surface (TNTA-NO) displayed excellent blood compatibility and cytocompatibility to ECs. Compared with other surfaces, the TNTA-NO coating can not only further promote BSA adsorption and inhibit the adhesion and activation of platelets as well as hemolysis, but also significantly enhance ECs adhesion and proliferation and up-regulate VEGF and NO expression of ECs. The current study demonstrated that the NO-catalytically generating hydrogel coating on the titanium alloy can mimic the glycocalyx structure and endothelium function to catalyze a large number of NO donors in human blood to produce NO, and thus simultaneously enhance the surface hemocompatibility and endothelialization, representing a promising strategy for long-term cardiovascular implants of titanium-based devices.

Endothelial Dysfunction in Patients Undergoing Cardiac Surgery: A Narrative Review and Clinical Implications

Cardiac surgery is one of the highest-risk procedures, usually involving cardiopulmonary bypass and commonly inducing endothelial injury that contributes to the development of perioperative and postoperative organ dysfunction. Substantial scientific efforts are being made to unravel the complex interaction of biomolecules involved in endothelial dysfunction to find new therapeutic targets and biomarkers and to develop therapeutic strategies to protect and restore the endothelium. This review highlights the current state-of-the-art knowledge on the structure and function of the endothelial glycocalyx and mechanisms of endothelial glycocalyx shedding in cardiac surgery. Particular emphasis is placed on potential strategies to protect and restore the endothelial glycocalyx in cardiac surgery. In addition, we have summarized and elaborated the latest evidence on conventional and potential biomarkers of endothelial dysfunction to provide a comprehensive synthesis of crucial mechanisms of endothelial dysfunction in patients undergoing cardiac surgery, and to highlight their clinical implications.

Albumin protects the ultrastructure of the endothelial glycocalyx of coronary arteries in myocardial ischemia-reperfusion injury in vivo

Myocardial ischemia-reperfusion (I/R) injury induces endothelial glycocalyx (GCX) degradation. Several candidate GCX-protective factors including albumin have been identified, few have been demonstrated in in vivo studies and most albumins used to date have been heterologous. Albumin is a carrier protein for sphingosine 1-phosphate (S1P), which has protective effects on the cardiovascular system. However, changes inhibited by albumin in the endothelial GCX structure in I/R in vivo via the S1P receptor has not been reported. In this study, we aimed to determine whether albumin prevents the shedding of endothelial GCX in response to I/R in vivo. Rats were divided into four groups: control (CON), I/R, I/R with albumin preload (I/R + ALB), and I/R + ALB with S1P receptor agonist fingolimod (I/R + ALB + FIN). FIN acts as an initial agonist of S1P receptor 1 and downregulates the receptor in an inhibitory manner. The CON and I/R groups received saline and I/R + ALB and I/R + ALB + FIN groups received albumin solution before left anterior descending coronary artery ligation. Our study used rat albumin. Shedding of endothelial GCX was evaluated in the myocardium by electron microscopy, and the concentration of serum syndecan-1 was measured. Thus, albumin administration maintained the structure of endothelial GCX and prevented shedding of endothelial GCX via the S1P receptor in myocardial I/R, and FIN annihilated the protective effect of albumin against I/R injury.

Endothelial glycocalyx in retina, hyperglycemia, and diabetic retinopathy.

The endothelial glycocalyx (EG) is a meshlike network present on the apical surface of the endothelium. Membrane-bound proteoglycans, the major backbone molecules of the EG, consist of glycosaminoglycans attached to core proteins. In addition to maintaining the integrity of the endothelial barrier, the EG regulates inflammation and perfusion and acts as a mechanosensor. The loss of the EG can cause endothelial dysfunction and drive the progression of vascular diseases including diabetic retinopathy. Therefore, the EG presents a novel therapeutic target for treatment of vascular complications. In this review article, we provide an overview of the structure and function of the EG in the retina. Our particular focus is on hyperglycemia-induced perturbations in the glycocalyx structure in the retina, potential underlying mechanisms, and clinical trials studying protective treatments against degradation of the EG.

The role of the alveolar epithelial glycocalyx in acute respiratory distress syndrome.

The alveolar epithelial glycocalyx is a dense anionic layer of glycosaminoglycans (GAGs) and proteoglycans that lines the apical surface of the alveolar epithelium. In contrast to the pulmonary endothelial glycocalyx, which has well-established roles in vascular homeostasis and septic organ dysfunction, the alveolar epithelial glycocalyx is less understood. Recent preclinical studies demonstrated that the epithelial glycocalyx is degraded in multiple murine models of acute respiratory distress syndrome (ARDS), particularly those that result from inhaled insults (so-called "direct" lung injury), leading to shedding of GAGs into the alveolar airspaces. Epithelial glycocalyx degradation also occurs in humans with respiratory failure, as quantified by analysis of airspace fluid obtained from ventilator heat moisture exchange (HME) filters. In patients with ARDS, GAG shedding correlates with the severity of hypoxemia and is predictive of the duration of respiratory failure. These effects may be mediated by surfactant dysfunction, as targeted degradation of the epithelial glycocalyx in mice was sufficient to cause increased alveolar surface tension, diffuse microatelectasis, and impaired lung compliance. In this review, we describe the structure of the alveolar epithelial glycocalyx and the mechanisms underlying its degradation during ARDS. We additionally review the current state of knowledge regarding the attributable effect of epithelial glycocalyx degradation in lung injury pathogenesis. Finally, we address glycocalyx degradation as a potential mediator of ARDS heterogeneity, and the subsequent value of point-of-care quantification of GAG shedding to potentially identify patients who are most likely to respond to pharmacological agents aimed at attenuating glycocalyx degradation.

Human collecting lymphatic glycocalyx identification by electron microscopy and immunohistochemistry

Blood flow is translated into biochemical inflammatory or anti-inflammatory signals based onshear stress type, by means of sensitive endothelial receptors. Recognition of the phenomenon is of paramount importance for enhanced insights into the pathophysiological processes of vascular remodeling. The endothelial glycocalyx is a pericellular matrix, identified in both arteries and veins, acting collectively as a sensor responsive to blood flow changes. Venous and lymphatic physiology is interconnected; however, to our knowledge, a lymphatic glycocalyx structure has never been identified in humans. The objective of this investigation is to identify glycocalyx structures from ex vivo lymphatic human samples. Lower limb vein and lymphatic vessels were harvested. The samples were analyzed by transmission electron microscopy. The specimens were also examined by immunohistochemistry. Transmission electron microscopy identified a glycocalyx structure in human venous and lymphatic samples. Immunohistochemistry for podoplanin, glypican-1, mucin-2, agrin and brevican characterized lymphatic and venous glycocalyx-like structures. To our knowledge, the present work reports the first identification of a glycocalyx-like structure in human lymphatic tissue. The vasculoprotective action of the glycocalyx could become an investigational target in the lymphatic system as well, with clinical implications for the many patients affected by lymphatic disorders.

The endothelial glycocalyx-All the same? No, it is not.

The endothelial glycocalyx covers the lumen of blood vessels throughout the body and plays an important role in endothelial homeostasis. Advances in electron microscopy techniques have provided clues to better understand the structure and composition of identical vascular endothelial glycocalyx. The morphology and thickness of the endothelial glycocalyx differ from organ to organ. The content of the endothelial glycocalyx covering the vascular lumen differs even in the brain, heart, and lungs, which have the same continuous capillaries. Various types of inflammation are known to attenuate the endothelial glycocalyx; however, we found that the morphology of the glycocalyx damaged by acute inflammation differed from that damaged by chronic inflammation. Acute inflammation breaks the endothelial glycocalyx unevenly, whereas chronic inflammation leads to the overall shortening of the endothelial glycocalyx. The same drug has different effects on the endothelial glycocalyx, depending on the location of the target blood vessels. This difference in response may reflect not only the size and shape of the endothelial glycocalyx but also the different constituents. In the cardiac tissue, the expression of glypican-1, a core protein of the endothelial glycocalyx, was enhanced. By contrast, in the pulmonary tissue, the expression of heparan sulfate 6-O-sulfotransferase 1 and endothelial cell-specific molecule-1 significantly increased in the treatment group compared with that in the no-treatment group. In this review, we present the latest findings on the evolution of the vascular endothelial glycocalyx and consider the microstructural differences.