Endothelial Glycocalyx Degradation in Critical Illness and Injury

Association Between Endothelial Alterations, Cardiac Function, and Outcomes From Health to Heart Failure: Insight From the STANISLAS, MEDIA-DHF, and BIOSTAT-CHF Cohorts

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is a multifaceted syndrome, likely stemming from comorbidity-induced inflammation resulting in endothelial dysfunction. Endothelial glycocalyx degradation's role in the development and prognosis of HFpEF remains largely unexplored. Our study aimed at exploring the association between glycocalyx degradation and diastolic dysfunction and determining whether glycocalyx degradation can predict clinical outcomes in patients with HFpEF.

METHODS

Perlecan and thrombomodulin concentrations were assessed in individuals deemed healthy (STANISLAS [Suivi Temporaire Annuel Non-Invasif de la Santé des Lorrains Assurés Sociaux (Annual Noninvasive Temporary Monitoring of the Health of Insured Lorrainers)] cohort, n=1705) and patients with HFpEF (MEDIA-DHF [Metabolic Road to Diastolic Heart Failure], n=460 and BIOSTAT-CHF [Biology Study to Tailored Treatment in Chronic Heart Failure], n=556) to evaluate endothelial glycocalyx degradation.

RESULTS

In patients with HFpEF, perlecan but not thrombomodulin was increased compared with controls (P<0.0001 versus P=0.73). In adjusted analysis, perlecan was associated with peak early mitral inflow velocity/peak early diastolic mitral annular velocity ratio and thrombomodulin with peak early diastolic mitral annular velocity in control individuals, whereas perlecan and thrombomodulin were associated with peak early mitral inflow velocity/peak early diastolic mitral annular velocity and left atrial volume index in patients with HFpEF (all P<0.03). Perlecan was significantly associated with cardiovascular hospitalization and death in the MEDIA-DHF (adjusted hazard ratio [HR] for highest tertile versus first tertile, 2.44 [95% CI, 1.11-5.34]; P=0.026) and BIOSTAT-CHF cohorts (adjusted HR, 2.12 [95% CI, 1.49-3.03]; P<0.0001). Thrombomodulin was associated with a worse outcome in BIOSTAT-CHF (P=0.004) but not in MEDIA-DHF.

CONCLUSIONS

Higher circulating levels of the endothelial glycocalyx degradation biomarkers like perlecan and, to a lesser extent, thrombomodulin are associated with features of diastolic dysfunction in population and HFpEF settings and predict poor outcome in patients with HFpEF. These results suggest that glycocalyx degradation may be an early step in the pathological processes leading to HFpEF and gain further prognostic value in later stages (ie, overt HFpEF).

REGISTRATION

URL: https://clinicaltrials.gov/; Unique identifiers: NCT01391442, https://clinicaltrials.gov/study/NCT01391442?cond=stanislas&rank=1; NCT02446327; URL: https://cordis.europa.eu; BIOSTAT-CHF ID: 242209.

Glycocalyx Disintegration Is Associated with Mortality in Chronic Heart Failure

Background: Glycocalyx disintegration is associated with adverse outcomes in patients with trauma or sepsis. As microvascular dysfunction has an impact on disease progression in chronic heart failure (CHF) patients, we hypothesized that changes in microcirculation might be associated with mortality. Methods: Fifty patients with ischemic and non-ischemic cardiomyopathy and conservative treatment with baseline measurements of the sublingual microcirculation (via Sidestream Darkfield videomicroscopy) were followed up for two years. Glycocalyx thickness was assessed indirectly by calculation of the perfused boundary region (PBR). Results: Loss of glycocalyx was pronounced in non-survivors after one, n = 10, and two years, n = 16; PBR: 2.05 μm (1.88-2.15 μm) vs. 1.87 μm (1.66-2.03 μm) and 2.04 (1.93-2.11) vs. 1.84 (1.62-1.97); p = 0.042 and p = 0.003, respectively. Area under the ROC curve for the analysis of the predictive value of PBR on two-year mortality was 0.77 (p = 0.003; SE: 0.07, CI (95%): 0.63-0.91). ROC curve analysis determined a PBR of 1.9 μm as the best predictor for two-year mortality (sensitivity: 0.81; specificity: 0.59). Moreover, multivariate regression analysis revealed PBR and functional capillary density as significant predictors of two-year mortality, p = 0.036 and p = 0.048, respectively. Conclusions: Glycocalyx disintegration is related to poor overall survival in CHF patients.

Multi-omic analysis reveals the unique glycan landscape of the blood-brain barrier glycocalyx

The blood-brain barrier (BBB) glycocalyx is the dense layer of glycans and glycoconjugates that coats the luminal surface of the central nervous system (CNS) vasculature. Despite being the first point of contact between the blood and brain, not much is known about the BBB glycocalyx. Here, we performed a multi-omic investigation of the BBB glycocalyx which revealed a unique glycan landscape characterized by enrichment of sialic acid, chondroitin sulfate, and hyaluronan. We found that the BBB glycocalyx was thicker than glycocalyces in the peripheral vasculature and that hyaluronan was the major contributor to its ultrastructure. Using endothelial RNA sequencing, we found potential genetic determinants for these differences, including BBB enrichment of genes involved in sialic acid addition and peripheral enrichment of Tmem2 and Hyal2, the only known cell-surface hyaluronidases. Glycocalyx degradation and increases in vascular permeability are widely associated with inflammation. However, we found that the BBB glycocalyx remains largely unchanged in neuroinflammation during the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis and that its degradation is not sufficient to alter BBB permeability in health. Moreover, we showed that CNS endothelial sialic acid removal delays onset of EAE, indicating that BBB glycocalyx sialic acid may contribute to the progression of neuroinflammation. These findings underscore the unique and robust nature of the BBB glycocalyx and provide targets and tools for future studies into its role in health and neuroinflammation.

Sepsis-associated endothelial glycocalyx damage: a review of animal models, clinical evidence, and molecular mechanisms

In the mammalian cardiovascular system, endothelial glycocalyx is a gel-like layer that covers the luminal surface of endothelial cells (ECs) and plays crucial roles in vascular homeostasis, permeability and leukocyte adhesion. Degradation of this structure occurs early in sepsis and becomes accordingly dysfunctional. In severe cases, it is not self-regulated by the organism. However, the relationship between the glycocalyx and the occurrence and development of sepsis remains poorly understood. One possibility is that thinned glycocalyx promotes leukocyte recognition and adhesion, thereby facilitating the elimination of pathogens from infected areas. This may represent a protective mechanism developed by the organism during through evolutionary processes. However, if the damage persists and disrupts the dynamic balance of the microcirculation, interstitial edema or organ failure can occur. Thus, we asked the questions, what is the precise composition and structure of the glycocalyx? How is it degraded? What animal models are available to study the relationship between the glycocalyx and sepsis? What glycocalyx biomarkers are found in the blood of patients with sepsis? To determine whether sepsis can be treated by interfering with the glycocalyx, this study provides a systematic summary and discussion of the latest progress in addressing these questions.

Application of Human Plasma/Serum to Cell Culture In Vitro: A Translational Research Approach to Better Define Disease Mechanisms

In vitro cell culture experiments play an important role in medical research. Various cellular mechanisms and signaling pathways have been identified with in vitro experimental techniques. Unfortunately, the clinical and translational impact of these studies is often limited due to their inability to closely resemble physiological or pathophysiological milieus in cell culture and the use of unrealistic experimental conditions. Thus, further developments must be made to improve the translation of in vitro cell culture work. The application of human plasma or serum as a stimulus for cells, human or otherwise, is a relatively new approach that ultimately overcomes many of the in vitro limitations and provides a more physiologically relevant model. While this technique has been used for the investigation of various diseases and pharmacological mechanisms, discrepancies remain regarding the appropriate methodologies. This review provides insight into recent findings through the application of human plasma or serum as stimuli, as well as an analysis of methodological considerations and suggestions for future directions.

Association of endotheliopathy with coagulofibrinolytic reactions and disseminated intravascular coagulation after trauma: a retrospective observational study

We carried out a retrospective observational investigation to explore the association of endotheliopathy with coagulofibrinolytic reactions and the progression of disseminated intravascular coagulation (DIC) in adult trauma patients. We measured syndecan-1 (SDC-1), an indicator of endotheliopathy, and biomarkers of coagulofibrinolysis in 100 trauma patients immediately transferred to Ehime University Hospital. We evaluated the correlations between the coagulofibrinolytic parameters and SDC-1. We also investigated the association between SDC-1 elevations and the development of DIC, and determined the discriminators of DIC development. The median SDC-1 concentration was 82.7 (43.5-178.1) ng/mL. DIC developed in 16 patients (16.0%), and SDC-1 concentrations were significantly higher in DIC patients than in non-DIC patients (218.8 [134.5-798.2] ng/mL vs. 67.2 [39.6-114.5] ng/mL, p < 0.001). Receiver operating characteristic curve analysis revealed that the circulating SDC-1 level effectively predicted the progression of DIC, with an area under the curve of 0.862 (95% confidence interval [CI], 0.789-0.936). The optimal cut-off value was determined to be 92.5 ng/mL, yielding a sensitivity of 100.0% and a specificity of 67.8% (p < 0.001). A simple logistic regression analysis showed that a circulating SDC-1 concentration of > 92.5 ng/mL was significantly correlated with DIC progression (odds ratio [OR], 31.67; 95%CI: 3.97-252.31, p = 0.001). Many coagulofibrinolytic parameters were significantly correlated with SDC-1. Estimating the discriminators of DIC development by the least absolute shrinkage and selection operator (LASSO) and elastic-net regression analysis identified markers of coagulofibrinolytic activation, such as thrombin-antithrombin complex (TAT) and tissue plasminogen activator (tPA). A multivariate logistic regression model using TAT, tPA, and SDC-1 demonstrated that TAT and tPA, but not SDC-1, were independent factors predicting the development of DIC (TAT per 10 µg/L: OR, 1.14, 95%CI: 1.05-1.24, p = 0.003; tPA per 100pg/mL: OR, 1.03, 95%CI: 1.01-1.05, p = 0.003; SDC-1 per 10ng/mL: OR, 1.00, 95%CI: 0.99-1.01, p = 0.973). Mediation analysis showed that SDC-1 elevation was predominantly associated with the development of DIC indirectly through the increase in TAT (proportion mediated = 96.1%, p < 0.001), while there was no significant indirect effect of SDC-1 elevation on the role of TAT elevation in DIC development was observed (p = 0.340). The primary pathogenesis of DIC in the acute phase of trauma is likely driven by coagulofibrinolytic activation. Endotheliopathy, as reflected by elevated circulating levels of SDC-1, is strongly associated with coagulofibrinolytic responses. Although endotheliopathy may contribute to the early development of DIC through coagulation activation, its role appears to be limited.

Endothelial dysfunction markers syndecan-1 and thrombomodulin are associated with higher albuminuria levels in type 2 diabetes with no history of clinical cardiovascular disease

INTRODUCTION

Individuals with type 2 diabetes and increased albuminuria, a well-established marker of microvascular complications, are at a higher risk for cardiovascular disease (CVD) and premature mortality. Therefore, a better understanding of the underlying pathophysiology is needed to improve risk stratification and tailor prevention and intervention.

METHODS

We conducted a cross-sectional study including 463 individuals with type 2 diabetes, various degrees of albuminuria and without CVD. We analysed the association between albuminuria and markers of endothelial function (thrombomodulin and syndecan-1), thrombin generation (thrombin-antithrombin complex, prothrombin fragment 1 + 2), fibrinogen, platelet function (activation using soluble plasma selectin and aggregation using Multiplate® Analyzer) using regression models.

RESULTS

In the study cohort 33 % were women, the mean ± SD age was 65 ± 9 years, and median [IQR] diabetes duration was 15 [9-20] years. In total, 344 (74 %) individuals had normal albuminuria, 87 (19 %) moderately- and 32 (7 %) severely increased albuminuria levels. Higher markers of endothelial function and fibrinogen were independently associated with higher albuminuria levels (p < 0.01). No association between albuminuria and markers of thrombin generation and platelet was demonstrated.

CONCLUSION

We demonstrated an independent association between albuminuria and markers of endothelial function and fibrinogen in individuals with type 2 diabetes and no history of CVD.

The Crucial Triad: Endothelial Glycocalyx, Oxidative Stress, and Inflammation in Cardiac Surgery-Exploring the Molecular Connections

Since its introduction, the number of heart surgeries has risen continuously. It is a high-risk procedure, usually involving cardiopulmonary bypass, which is associated with an inflammatory reaction that can lead to perioperative and postoperative organ dysfunction. The extent of complications following cardiac surgery has been the focus of interest for several years because of their impact on patient outcomes. Recently, numerous scientific efforts have been made to uncover the complex mechanisms of interaction between inflammation, oxidative stress, and endothelial dysfunction that occur after cardiac surgery. Numerous factors, such as surgical and anesthetic techniques, hypervolemia and hypovolemia, hypothermia, and various drugs used during cardiac surgery trigger the development of systemic inflammatory response and the release of oxidative species. They affect the endothelium, especially endothelial glycocalyx (EG), a thin surface endothelial layer responsible for vascular hemostasis, its permeability and the interaction between leukocytes and endothelium. This review highlights the current knowledge of the molecular mechanisms involved in endothelial dysfunction, particularly in the degradation of EG. In addition, the major inflammatory events and oxidative stress responses that occur in cardiac surgery, their interaction with EG, and the clinical implications of these events have been summarized and discussed in detail. A better understanding of the complex molecular mechanisms underlying cardiac surgery, leading to endothelial dysfunction, is needed to improve patient management during and after surgery and to develop effective strategies to prevent adverse outcomes that complicate recovery.

Histon activities in the extracellular environment: regulation and prothrombotic implications

PURPOSE OF REVIEW

Thromboembolic complications are a major contributor to global mortality. The relationship between inflammation and coagulation pathways has become an emerging research topic where the role of the innate immune response, and specifically neutrophils in "immunothrombosis" are receiving much attention. This review aims to dissect the intricate interplay between histones (from neutrophils or cellular damage) and the haemostatic pathway, and to explore mechanisms that may counteract the potentially procoagulant effects of those histones that have escaped their nuclear localization.

RECENT FINDINGS

Extracellular histones exert procoagulant effects via endothelial damage, platelet activation, and direct interaction with coagulation proteins. Neutralization of histone activities can be achieved by complexation with physiological molecules, through pharmacological compounds, or via proteolytic degradation. Details of neutralization of extracellular histones are still being studied.

SUMMARY

Leveraging the understanding of extracellular histone neutralization will pave the way for development of novel pharmacological interventions to treat and prevent complications, including thromboembolism, in patients in whom extracellular histones contribute to their overall clinical status.

Vascular access device selection: Optimizing patient outcomes - Part 1

ABSTRACT

A systematic evaluation of vascular access device (VAD) selection incorporates patient, device, and infusate characteristics to ensure optimal device placement. This article explores VAD selection from the perspective of vessel health and preservation and describes VAD selection options and indications, VAD-related complications, and strategies to reduce those complications.

Impaired instructive and protective barrier functions of the endothelial cell glycocalyx pericellular matrix is impacted in COVID-19 disease

The aim of this study was to review the roles of endothelial cells in normal tissue function and to show how COVID-19 disease impacts on endothelial cell properties that lead to much of its associated symptomatology. This places the endothelial cell as a prominent cell type to target therapeutically in the treatment of this disorder. Advances in glycosaminoglycan analytical techniques and functional glycomics have improved glycosaminoglycan mimetics development, providing agents that can more appropriately target various aspects of the behaviour of the endothelial cell in-situ and have also provided polymers with potential to prevent viral infection. Thus, promising approaches are being developed to combat COVID-19 disease and the plethora of symptoms this disease produces. Glycosaminoglycan mimetics that improve endothelial glycocalyx boundary functions have promising properties in the prevention of viral infection, improve endothelial cell function and have disease-modifying potential. Endothelial cell integrity, forming tight junctions in cerebral cell populations in the blood-brain barrier, prevents the exposure of the central nervous system to circulating toxins and harmful chemicals, which may contribute to the troublesome brain fogging phenomena reported in cognitive processing in long COVID disease.

High salt intake and HIV infection on endothelial glycocalyx shedding in salt-sensitive hypertension

The endothelial glycocalyx is closely associated with various physiological and pathophysiological events. Significant modification of the endothelial glycocalyx is an early process in the pathogenesis of cardiovascular disease. High dietary salt and HIV infection damages the endothelial glycocalyx causing endothelial dysfunction and increasing the risk for salt-sensitive hypertension and cardiovascular disease. The two factors, HIV infection and dietary salt are critical independent predictors of hypertension and cardiovascular disease and often synergize to exacerbate and accelerate disease pathogenesis. Salt-sensitive hypertension is more common among people living with HIV and is associated with risk for cardiovascular disease, stroke, heart attack and even death. However, the underlying mechanisms linking endothelial glycocalyx damage to dietary salt and HIV infection are lacking. Yet, both HIV infection/treatment and dietary salt are closely linked to endothelial glycocalyx damage and development of salt-sensitive hypertension. Moreover, the majority of individuals globally, consume more salt than is recommended and the burden of HIV especially in sub-Sahara Africa is disproportionately high. In this review, we have discussed the missing link between high salt and endothelial glycocalyx shedding in the pathogenesis of salt-sensitive hypertension. We have further elaborated the role played by HIV infection and treatment in modifying endothelial glycocalyx integrity to contribute to the development of hypertension and cardiovascular disease.

Treatment of vascular dementia in female rats with AV-001, an Angiopoietin-1 mimetic peptide, improves cognitive function

Background

Vascular dementia (VaD) is a complex neurodegenerative disorder. We previously found that treatment of VaD in middle-aged male rats subjected to multiple microinfarction (MMI) with AV-001, a Tie2 receptor agonist, significantly improves cognitive function. Age and sex affect the development and response of VaD to therapeutic intervention. Thus, the present study investigated the therapeutic effect of AV-001 on VaD in aged female rats subjected to MMI.

Methods

Female 18-month-old Wistar rats were subjected to MMI by injecting either 1,000 (low dose, LD-MMI) or 6,000 (high dose, HD-MMI) cholesterol crystals of size 70-100 μm into the right internal carotid artery. AV-001 (1 μg/Kg, i.p.) was administered once daily after MMI for 1 month, with treatment initiated 1 day after MMI. A battery of behavioral tests to examine sensorimotor and cognitive functions was performed at 21-28 days after MMI. All rats were sacrificed at 1 month after MMI.

Results

Aged female rats subjected to LD-MMI exhibit severe neurological deficits, memory impairment, and significant white matter (WM) and oligodendrogenesis injury in the corpus callosum compared with control rats. HD-MMI in aged female rats induces significant anxiety- and depression-like behaviors, which were not detected in LD-MMI aged female rats. Also, HD-MMI induces significantly increased WM injury compared to LD-MMI. AV-001 treatment of LD-MMI and HD-MMI increases oligodendrogenesis, myelin and axon density in the corpus callosum and striatal WM bundles, promotes WM integrity and attenuates neurological and cognitive deficits. Additionally, both LD-MMI and HD-MMI rats exhibit a significant increase, while AV-001 significantly decreases the levels of inflammatory factors in the cerebrospinal fluid (CSF).

Conclusion

MMI reduces oligodendrogenesis, and induces demyelination, axonal injury and WM injury, and causes memory impairment, while HD-MMI induces increased WM injury and further depression-like behaviors compared to LD-MMI rats. AV-001 has a therapeutic effect on aged female rats with MMI by reducing WM damage and improving neuro-cognitive outcomes.

Cationic Polysaccharides Bind to the Endothelial Cell Surface Extracellular Matrix Involving Heparan Sulfate

Cationic polysaccharides have been extensively studied for drug delivery via the bloodstream, yet few have progressed to clinical use. Endothelial cells lining the blood vessel wall are coated in an anionic extracellular matrix called the glycocalyx. However, we do not fully comprehend the charged polysaccharide interactions with the glycocalyx. We reveal that the cationic polysaccharide poly(acetyl, arginyl) glucosamine (PAAG) exhibits the highest association with the endothelial glycocalyx, followed by dextran (neutral) and hyaluronan (anionic). Furthermore, we demonstrate that PAAG binds heparan sulfate (HS) within the glycocalyx, leading to intracellular accumulation. Using an in vitro glycocalyx model, we demonstrate a charge-based extent of association of polysaccharides with HS. Mechanistically, we observe that PAAG binding to HS occurs via a condensation reaction and functionally protects HS from degradation. Together, this study reveals the interplay between polysaccharide charge properties and interactions with the endothelial cell glycocalyx toward improved delivery system design and application.

Managing sepsis and septic shock in an endothelial glycocalyx-friendly way: from the viewpoint of surviving sepsis campaign guidelines

Maintaining tissue perfusion in sepsis depends on vascular integrity provided by the endothelial glycocalyx, the critical layer covering the luminal surface of blood vessels. The glycocalyx is composed of proteoglycans, glycosaminoglycans, and functional plasma proteins that are critical for antithrombogenicity, regulating tone, controlling permeability, and reducing endothelial interactions with leukocytes and platelets. Degradation of the glycocalyx in sepsis is substantial due to thromboinflammation, and treatments for sepsis and septic shock may exacerbate endotheliopathy via additional glycocalyx injury. As a result, therapeutic strategies aimed at preserving glycocalyx integrity should be considered, including modifications in fluid volume resuscitation, minimizing catecholamine use, controlling hyperglycemia, and potential use of corticosteroids and anticoagulants. In this review, we explore treatment strategies aligned with the recommendations outlined in the Surviving Sepsis Campaign Guidelines 2021 with a special emphasis on evidence regarding glycocalyx protection.

Revolutionizing trauma care: advancing coagulation management and damage control anesthesia

Despite advances in emergency transfer systems and trauma medicine, the incidence of preventable deaths due to massive hemorrhage remains high. Recent immunological research has elucidated key mechanisms underlying trauma-induced coagulopathy in the early stages of trauma, including sympathoadrenal stimulation, shedding of the glycocalyx, and endotheliopathy. Consequently, the condition progresses to fibrinogen depletion, hyperfibrinolysis, and platelet dysfunction. Coexisting factors such as uncorrected acidosis, hypothermia, excessive crystalloid administration, and a history of anticoagulant use exacerbate coagulopathy. This study introduces damage-control anesthetic management based on recent insights into damage-control resuscitation, emphasizing the importance of rapid transport, timely bleeding control, early administration of antifibrinolytics and fibrinogen concentrates, and maintenance of calcium levels and body temperature. Additionally, this study discusses brain-protective strategies for trauma patients with brain injuries and the utilization of cartridge-based viscoelastic assays for goal-directed coagulation management in trauma settings. This comprehensive approach may provide potential insights for anesthetic management in the fast-paced field of trauma medicine.

Temporal Alterations in Cerebrovascular Glycocalyx and Cerebral Blood Flow after Exposure to a High-Intensity Blast in Rats

The glycocalyx is a proteoglycan-glycoprotein structure lining the luminal surface of the vascular endothelium and is susceptible to damage due to blast overpressure (BOP) exposure. The glycocalyx is essential in maintaining the structural and functional integrity of the vasculature and regulation of cerebral blood flow (CBF). Assessment of alterations in the density of the glycocalyx; its components (heparan sulphate proteoglycan (HSPG/syndecan-2), heparan sulphate (HS), and chondroitin sulphate (CS)); CBF; and the effect of hypercapnia on CBF was conducted at 2-3 h, 1, 3, 14, and 28 days after a high-intensity (18.9 PSI/131 kPa peak pressure, 10.95 ms duration, and 70.26 PSI·ms/484.42 kPa·ms impulse) BOP exposure in rats. A significant reduction in the density of the glycocalyx was observed 2-3 h, 1-, and 3 days after the blast exposure. The glycocalyx recovered by 28 days after exposure and was associated with an increase in HS (14 and 28 days) and in HSPG/syndecan-2 and CS (28 days) in the frontal cortex. In separate experiments, we observed significant decreases in CBF and a diminished response to hypercapnia at all time points with some recovery at 3 days. Given the role of the glycocalyx in regulating physiological function of the cerebral vasculature, damage to the glycocalyx after BOP exposure may result in the onset of pathogenesis and progression of cerebrovascular dysfunction leading to neuropathology.

Evaluating the efficacy of a standardized 4 mL/kg fluid bolus technique in critically ill patients with elevated PvaCO2: secondary analysis of two prospective studies

Background

Limiting the fluid bolus (FB) volume may attenuate side effects, including hemodilution and increased filling pressures, but it may also reduce hemodynamic responsiveness. The minimum volume to create hemodynamic effects is considered to be 4 mL/kg. In critically ill patients, the hemodynamic effects of FB with this volume have not been adequately investigated and compared to higher quantities. We hypothesized that a standardized FB approach using 4 mL/kg has comparable hemodynamic and metabolic effects to the common practice of physician-determined FB in critically ill patients.

Methods

We conducted post hoc analysis of two trials in non-selected critically ill patients with central venous-to-arterial CO2 tension (PvaCO2) >6 mmHg and no acute bleeding. All patients received crystalloids either at a physician-determined volume and rate or at 4 mL/kg pump-administered at 1.2 L/h. Cardiac index (CI) was calculated with transthoracic echocardiogram, and arterial and venous blood gas samples were assessed before and after FB. Endpoints were changes in CI and oxygen delivery (DO2) >15%.

Results

A total of 47 patients were eligible for the study, 15 of whom received physician-determined FB and 32 of whom received standardized FB. Patients in the physician-determined FB group received 16 (12-19) mL/kg at a fluid rate of 1.5 (1.5-1.9) L/h, compared to 4.1 (3.7-4.4) mL/kg at a fluid rate of 1.2 (1.2-1.2) L/h (p < 0.01) in the standardized FB group. The difference in CI elevations between the two groups was not statistically significant (8.8% [-0.1-19.9%] vs. 8.4% [0.3-23.2%], p = 0.76). Compared to physician-determined FB, the standardized FB technique had similar probabilities of increasing CI or DO2 by >15% (odds ratios: 1.3 [95% CI: 0.37-5.18], p = 0.66 and 1.83 [95% CI: 0.49-7.85], p = 0.38).

Conclusion

A standardized FB protocol (4 mL/kg at 1.2 L/h) effectively reduced the volume of fluid administered to critically ill patients without compromising hemodynamic or metabolic effects.

Pediatric sepsis inflammatory blood biomarkers that correlate with clinical variables and severity of illness scores

BACKGROUND

Sepsis is a dysregulated systemic inflammatory response triggered by infection, resulting in organ dysfunction. A major challenge in clinical pediatrics is to identify sepsis early and then quickly intervene to reduce morbidity and mortality. As blood biomarkers hold promise as early sepsis diagnostic tools, we aimed to measure a large number of blood inflammatory biomarkers from pediatric sepsis patients to determine their predictive ability, as well as their correlations with clinical variables and illness severity scores.

METHODS

Pediatric patients that met sepsis criteria were enrolled, and clinical data and blood samples were collected. Fifty-eight inflammatory plasma biomarker concentrations were determined using immunoassays. The data were analyzed with both conventional statistics and machine learning.

RESULTS

Twenty sepsis patients were enrolled (median age 13 years), with infectious pathogens identified in 75%. Vasopressors were administered to 85% of patients, while 55% received invasive ventilation and 20% were ventilated non-invasively. A total of 24 inflammatory biomarkers were significantly different between sepsis patients and age/sex-matched healthy controls. Nine biomarkers (IL-6, IL-8, MCP-1, M-CSF, IL-1RA, hyaluronan, HSP70, MMP3, and MMP10) yielded AUC parameters > 0.9 (95% CIs: 0.837-1.000; p < 0.001). Boruta feature reduction yielded 6 critical biomarkers with their relative importance: IL-8 (12.2%), MCP-1 (11.6%), HSP70 (11.6%), hyaluronan (11.5%), M-CSF (11.5%), and IL-6 (11.5%); combinations of 2 biomarkers yielded AUC values of 1.00 (95% CI: 1.00-1.00; p < 0.001). Specific biomarkers strongly correlated with illness severity scoring, as well as other clinical variables. IL-3 specifically distinguished bacterial versus viral infection (p < 0.005).

CONCLUSIONS

Specific inflammatory biomarkers were identified as markers of pediatric sepsis and strongly correlated to both clinical variables and sepsis severity.

Endothelial Glycocalyx Degradation Patterns in Sepsis-Associated Pediatric Acute Respiratory Distress Syndrome: A Single Center Retrospective Observational Study

BACKGROUND

Sepsis-associated destruction of the pulmonary microvascular endothelial glycocalyx (EGCX) creates a vulnerable endothelial surface, contributing to the development of acute respiratory distress syndrome (ARDS). Constituents of the EGCX shed into circulation, glycosaminoglycans and proteoglycans, may serve as biomarkers of endothelial dysfunction. We sought to define the patterns of plasma EGCX degradation products in children with sepsis-associated pediatric ARDS (PARDS), and test their association with clinical outcomes.

METHODS

We retrospectively analyzed a prospective cohort (2018-2020) of children (≥1 month to <18 years of age) receiving invasive mechanical ventilation for acute respiratory failure for ≥72 h. Children with and without sepsis-associated PARDS were selected from the parent cohort and compared. Blood was collected at time of enrollment. Plasma glycosaminoglycan disaccharide class (heparan sulfate, chondroitin sulfate, and hyaluronan) and sulfation subtypes (heparan sulfate and chondroitin sulfate) were quantified using liquid chromatography tandem mass spectrometry. Plasma proteoglycans (syndecan-1) were measured through an immunoassay.

RESULTS

Among the 39 mechanically ventilated children (29 with and 10 without sepsis-associated PARDS), sepsis-associated PARDS patients demonstrated higher levels of heparan sulfate (median 639 ng/mL [interquartile range, IQR 421-902] vs 311 [IQR 228-461]) and syndecan-1 (median 146 ng/mL [IQR 32-315] vs 8 [IQR 8-50]), both p = 0.01. Heparan sulfate subtype analysis demonstrated greater proportions of N-sulfated disaccharide levels among children with sepsis-associated PARDS (p = 0.01). Increasing N-sulfated disaccharide levels by quartile were associated with severe PARDS (n = 9/29) with the highest quartile including >60% of the severe PARDS patients (test for trend, p = 0.04). Higher total heparan sulfate and N-sulfated disaccharide levels were independently associated with fewer 28-day ventilator-free days in children with sepsis-associated PARDS (all p < 0.05).

CONCLUSIONS

Children with sepsis-associated PARDS exhibited higher plasma levels of heparan sulfate disaccharides and syndecan-1, suggesting that EGCX degradation biomarkers may provide insights into endothelial dysfunction and PARDS pathobiology.

Thrombotic Disease in Hemophilic Patients: Is This a Paradox in a State of Hypocoagulability?

Hemophilia patients have a deficiency in or dysfunction of clotting factors, which can lead to a bleeding tendency. However, paradoxically, some hemophilia patients may also be at an increased risk of developing thrombotic events such as deep vein thrombosis or pulmonary embolism. The pathophysiology of thrombosis in hemophilia patients is not fully understood, but it is thought to involve a complex interplay of various factors, including the severity of the hemophilia, the presence of other risk factors such as obesity, smoking, or the use of hormonal therapies, and the presence of certain genetic mutations that increase the risk of thrombosis. In addition, it has been suggested that the use of clotting factor replacement therapy, which is a standard treatment for hemophilia, may also contribute to the development of thrombosis in some cases.

Global trends in research on endothelial cells and sepsis between 2002 and 2022: A systematic bibliometric analysis

Sepsis is a systemic syndrome involving physiological, pathological, and biochemical abnormalities precipitated by infection and is a major global public health problem. Endothelial cells (ECs) dysfunction is a major contributor to sepsis-induced multiple organ failure. This bibliometric analysis aimed to identify and characterize the status, evolution of the field, and new research trends of ECs and sepsis over the past 20 years. For this analysis, the Web of Science Core Collection database was searched to identify relevant publications on ECs in sepsis published between January 1, 2002, and December 31, 2022. Microsoft Excel 2021, VOSviewer software, CiteSpace software, and the online analysis platform of literature metrology (http://bibliometric.com) were used to visualize the trends of publications' countries/regions, institutions, authors, journals, and keywords. In total, 4200 articles were identified and screened, primarily originating from 86 countries/regions and 3489 institutions. The USA was the leading contributor to this research field, providing 1501 articles (35.74 %). Harvard University's scientists were the most prolific, with 129 articles. Overall, 21,944 authors were identified, among whom Bae Jong Sup was the most prolific, contributing 129 publications. Additionally, Levi Marcel was the most frequently co-cited author, appearing 538 times. The journals that published the most articles were SHOCK, CRITICAL CARE MEDICINE, and PLOS ONE, accounting for 10.79 % of the total. The current emerging hotspots are concentrated on "endothelial glycocalyx," "NLRP3 inflammasome," "extracellular vesicle," "biomarkers," and "COVID-19," among others. In conclusion, this study provides a comprehensive overview of the scientific productivity and emerging research trends in the field of ECs in sepsis. The evidence supporting the significant role of ECs in both physiological and pathological responses to sepsis is continuously growing. More in-depth studies of the molecular mechanisms underlying sepsis-induced endothelial dysfunction and EC-targeted therapies are warranted in the future.

Myocardial Oedema as a Consequence of Viral Infection and Persistence-A Narrative Review with Focus on COVID-19 and Post COVID Sequelae

Microvascular integrity is a critical factor in myocardial fluid homeostasis. The subtle equilibrium between capillary filtration and lymphatic fluid removal is disturbed during pathological processes leading to inflammation, but also in hypoxia or due to alterations in vascular perfusion and coagulability. The degradation of the glycocalyx as the main component of the endothelial filtration barrier as well as pericyte disintegration results in the accumulation of interstitial and intracellular water. Moreover, lymphatic dysfunction evokes an increase in metabolic waste products, cytokines and inflammatory cells in the interstitial space contributing to myocardial oedema formation. This leads to myocardial stiffness and impaired contractility, eventually resulting in cardiomyocyte apoptosis, myocardial remodelling and fibrosis. The following article reviews pathophysiological inflammatory processes leading to myocardial oedema including myocarditis, ischaemia-reperfusion injury and viral infections with a special focus on the pathomechanisms evoked by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In addition, clinical implications including potential long-term effects due to viral persistence (long COVID), as well as treatment options, are discussed.

The association between hypoalbuminemia and microcirculation, endothelium, and glycocalyx disorders in children with sepsis

OBJECTIVE

The objective of this study was to evaluate the association between serum albumin levels and microcirculation changes, glycocalyx degradation, and the clinical outcomes of interest.

METHODS

Observational, prospective study in children with sepsis. The primary outcome was the association between hypoalbuminemia and microcirculation disorders, endothelial activation and glycocalyx degradation using a perfused boundary region (PBR) (abnormal >2.0 μm on sublingual video microscopy) or plasma biomarkers (syndecan-1, angiopoietin-2).

RESULTS

A total of 125 patients with sepsis were included. The median age was 2.0 years (IQR 0.5-12.5). Children with hypoalbuminemia had more abnormal microcirculation with a higher PBR (2.16 μm [IQR 2.03-2.47] vs. 1.92 [1.76-2.28]; p = .01) and more 4-6 μm capillaries recruited (60% vs. 40%; p = .04). The low albumin group that had the worst PBR had the most 4-6 μm capillaries recruited (rho 0.29; p < .01), 48% higher Ang-2 (p = .04), worse annexin A5 (p = 0.03) and no syndecan-1 abnormalities (p = .21). Children with hypoalbuminemia and a greater percentage of blood volume in their capillaries needed mechanical ventilation more often (56.3% vs. 43.7%; aOR 2.01 95% CI 1.38-3.10: p < .01).

CONCLUSIONS

In children with sepsis, an association was found between hypoalbuminemia and microcirculation changes, vascular permeability, and greater endothelial glycocalyx degradation.

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 the adhesion 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.

Heparanase inhibition leads to improvement in patients with acute gastrointestinal injuries induced by sepsis

BACKGROUND

Patients with sepsis are at high risk for acute gastrointestinal injury (AGI), but the diagnosis and treatment of AGI due to sepsis are unsatisfactory. Heparanase (HPA) plays an important role in septic AGI (S-AGI), but its specific mechanism is not completely understood, and few clinical reports are available.

AIM

To explore the effect and mechanism of HPA inhibition in S-AGI patients.

METHODS

In our prospective clinical trial, 48 patients with S-AGI were randomly assigned to a control group to receive conventional treatment, whereas 47 patients were randomly assigned to an intervention group to receive conventional treatment combined with low molecular weight heparin. AGI grade, sequential organ failure assessment score, acute physiology and chronic health evaluation II score, D-dimer, activated partial thromboplastin time (APTT), anti-Xa factor, interleukin-6, tumour necrosis factor-α, HPA, syndecan-1 (SDC-1), LC3B (autophagy marker), intestinal fatty acid binding protein, D-lactate, motilin, gastrin, CD4/CD8, length of intensive care unit (ICU) stay, length of hospital stay and 28-d survival on the 1st, 3rd and 7th d after treatment were compared. Correlations between HPA and AGI grading as well as LC3B were compared. Receiver operator characteristic (ROC) curves were generated to evaluate the diagnostic value of HPA, intestinal fatty acid binding protein and D-lactate in S-AGI.

RESULTS

Serum HPA and SCD-1 levels were significantly reduced in the intervention group compared with the control group (P < 0.05). In addition, intestinal fatty acid-binding protein, D-lactate, AGI grade, motilin, and gastrin levels and sequential organ failure assessment score were significantly decreased (P < 0.05) in the intervention group. However, LC3B, APTT, anti-Xa factor, and CD4/CD8 were significantly increased (P < 0.05) in the intervention group. No significant differences in interleukin-6, tumour necrosis factor-α, d-dimer, acute physiology and chronic health evaluation II score, length of ICU stay, length of hospital stay, or 28-d survival were noted between the two groups (P > 0.05). Correlation analysis revealed a significant negative correlation between HPA and LC3B and a significant positive correlation between HPA and AGI grade. ROC curve analysis showed that HPA had higher specificity and sensitivity in diagnosis of S-AGI.

CONCLUSION

HPA has great potential as a diagnostic marker for S-AGI. Inhibition of HPA activity reduces SDC-1 shedding and alleviates S-AGI symptoms. The inhibitory effect of HPA in gastrointestinal protection may be achieved by enhanced autophagy.

Aging and Vascular Disease: A Multidisciplinary Overview

Vascular aging, i.e., the deterioration of the structure and function of the arteries over the life course, predicts cardiovascular events and mortality. Vascular degeneration can be recognized before becoming clinically symptomatic; therefore, its assessment allows the early identification of individuals at risk. This opens the possibility of minimizing disease progression. To review these issues, a search was completed using PubMed, MEDLINE, and Google Scholar from 2000 to date. As a network of clinicians and scientists involved in vascular medicine, we here describe the structural and functional age-dependent alterations of the arteries, the clinical tools for an early diagnosis of vascular aging, and the cellular and molecular events implicated. It emerges that more studies are necessary to identify the best strategy to quantify vascular aging, and to design proper physical activity programs, nutritional and pharmacological strategies, as well as social interventions to prevent, delay, and eventually revert the disease.

The utility of syndecan-1 circulating levels as a biomarker in patients with previous or active COVID-19: a systematic review and meta-analysis

BACKGROUND

With the emergence of coronavirus disease of 2019 (COVID-19), several blood biomarkers have been identified, including the endothelial biomarker syndecan-1, a surface proteoglycan. In the current systematic review and meta-analysis, we aimed to assess the diagnostic and prognostic role of syndecan-1 in COVID-19.

METHODS

PubMed, Embase, Scopus, and Web of Science, as international databases, were searched for relevant studies measuring blood syndecan-1 levels in COVID-19 patients, COVID-19 convalescents, and healthy control subjects, in patients with different COVID-19 severities and/or in COVID-19 patients with poor outcomes. Random-effect meta-analysis was performed using STATA to calculate the standardized mean difference (SMD) and 95% confidence interval (CI) for the comparison between COVID-19 patients and healthy control subjects or COVID-19 convalescents and controls.

RESULTS

After screening by title/abstract and full text, 17 studies were included in the final review. Meta-analysis of syndecan-1 levels in COVID-19 compared with healthy control subjects revealed that patients with COVID-19 had significantly higher syndecan-1 levels (SMD 1.53, 95% CI 0.66 to 2.41, P < 0.01). In contrast, COVID-19 convalescent patients did not show significant difference with non-convalescents (SMD 0.08, 95% CI -0.63 to 0.78, P = 0.83). Regarding disease severity, two studies reported that more severe forms of the disease were associated with increased syndecan-1 levels. Moreover, patients who died from COVID-19 had higher syndecan-1 levels compared with survivors (SMD 1.22, 95% CI 0.10 to 2.33, P = 0.03).

CONCLUSION

Circulating syndecan-1 level can be used as a biomarker of endothelial dysfunction in COVID-19, as it was increased in COVID-19 patients and was higher in more severe instances of the disease. Further larger studies are needed to confirm these findings and further enlighten the role of syndecan-1 in clinical settings.

Experimental Models of Traumatic Injuries: Do They Capture the Coagulopathy and Underlying Endotheliopathy Induced by Human Trauma?

Trauma-induced coagulopathy (TIC) is a major cause of morbidity and mortality in patients with traumatic injury. It describes the spectrum of coagulation abnormalities that occur because of the trauma itself and the body's response to the trauma. These coagulation abnormalities range from hypocoagulability and hyperfibrinolysis, resulting in potentially fatal bleeding, in the early stages of trauma to hypercoagulability, leading to widespread clot formation, in the later stages. Pathological changes in the vascular endothelium and its regulation of haemostasis, a phenomenon known as the endotheliopathy of trauma (EoT), are thought to underlie TIC. Our understanding of EoT and its contribution to TIC remains in its infancy largely due to the scarcity of experimental research. This review discusses the mechanisms employed by the vascular endothelium to regulate haemostasis and their dysregulation following traumatic injury before providing an overview of the available experimental in vitro and in vivo models of trauma and their applicability for the study of the EoT and its contribution to TIC.

The unremarkable alveolar epithelial glycocalyx: a thorium dioxide-based electron microscopic comparison after heparinase or pneumolysin treatment

Recent investigations analyzed in depth the biochemical and biophysical properties of the endothelial glycocalyx. In comparison, this complex cell-covering structure is largely understudied in alveolar epithelial cells. To better characterize the alveolar glycocalyx ultrastructure, unaffected versus injured human lung tissue explants and mouse lungs were analyzed by transmission electron microscopy. Lung tissue was treated with either heparinase (HEP), known to shed glycocalyx components, or pneumolysin (PLY), the exotoxin of Streptococcus pneumoniae not investigated for structural glycocalyx effects so far. Cationic colloidal thorium dioxide (cThO₂) particles were used for glycocalyx glycosaminoglycan visualization. The level of cThO₂ particles orthogonal to apical cell membranes (≙ stained glycosaminoglycan height) of alveolar epithelial type I (AEI) and type II (AEII) cells was stereologically measured. In addition, cThO₂ particle density was studied by dual-axis electron tomography (≙ stained glycosaminoglycan density in three dimensions). For untreated samples, the average cThO₂ particle level was ≈ 18 nm for human AEI, ≈ 17 nm for mouse AEI, ≈ 44 nm for human AEII and ≈ 35 nm for mouse AEII. Both treatments, HEP and PLY, resulted in a significant reduction of cThO₂ particle levels on human and mouse AEI and AEII. Moreover, a HEP- and PLY-associated reduction in cThO₂ particle density was observed. The present study provides quantitative data on the differential glycocalyx distribution on AEI and AEII based on cThO₂ and demonstrates alveolar glycocalyx shedding in response to HEP or PLY resulting in a structural reduction in both glycosaminoglycan height and density. Future studies should elucidate the underlying alveolar epithelial cell type-specific distribution of glycocalyx subcomponents for better functional understanding.

Glycocalyx-Sodium Interaction in Vascular Endothelium

The glycocalyx generally covers almost all cellular surfaces, where it participates in mediating cell-surface interactions with the extracellular matrix as well as with intracellular signaling molecules. The endothelial glycocalyx that covers the luminal surface mediates the interactions of endothelial cells with materials flowing in the circulating blood, including blood cells. Cardiovascular diseases (CVD) remain a major cause of morbidity and mortality around the world. The cardiovascular risk factors start by causing endothelial cell dysfunction associated with destruction or irregular maintenance of the glycocalyx, which may culminate into a full-blown cardiovascular disease. The endothelial glycocalyx plays a crucial role in shielding the cell from excessive exposure and absorption of excessive salt, which can potentially cause damage to the endothelial cells and underlying tissues of the blood vessels. So, in this mini review/commentary, we delineate and provide a concise summary of the various components of the glycocalyx, their interaction with salt, and subsequent involvement in the cardiovascular disease process. We also highlight the major components of the glycocalyx that could be used as disease biomarkers or as drug targets in the management of cardiovascular diseases.

Treating COVID-19: Targeting the Host Response, Not the Virus

In low- and middle-income countries (LMICs), inexpensive generic drugs like statins, ACE inhibitors, and ARBs, especially if used in combination, might be the only practical way to save the lives of patients with severe COVID-19. These drugs will already be available in all countries on the first pandemic day. Because they target the host response to infection instead of the virus, they could be used to save lives during any pandemic. Observational studies show that inpatient statin treatment reduces 28–30-day mortality but randomized controlled trials have failed to show this benefit. Combination treatment has been tested for antivirals and dexamethasone but, with the exception of one observational study in Belgium, not for inexpensive generic drugs. Future pandemic research must include testing combination generic drug treatments that could be used in LMICs.

Immuno-Modulatory Effects of Dexamethasone in Severe COVID-19-A Swedish Cohort Study

Dexamethasone (Dex) has been shown to decrease mortality in severe coronavirus disease 2019 (COVID-19), but the mechanism is not fully elucidated. We aimed to investigate the physiological and immunological effects associated with Dex administration in patients admitted to intensive care with severe COVID-19. A total of 216 adult COVID-19 patients were included-102 (47%) received Dex, 6 mg/day for 10 days, and 114 (53%) did not. Standard laboratory parameters, plasma expression of cytokines, endothelial markers, immunoglobulin (Ig) IgA, IgM, and IgG against SARS-CoV-2 were analyzed post-admission to intensive care. Patients treated with Dex had higher blood glucose but lower blood lactate, plasma cortisol, IgA, IgM, IgG, D-dimer, cytokines, syndecan-1, and E-selectin and received less organ support than those who did not receive Dex (Without-Dex). There was an association between Dex treatment and IL-17A, macrophage inflammatory protein 1 alpha, syndecan-1 as well as E-selectin in predicting 30-day mortality. Among a subgroup of patients who received Dex early, within 14 days of COVID-19 debut, the adjusted mortality risk was 0.4 (95% CI 0.2-0.8), i.e., 40% compared with Without-Dex. Dex administration in a cohort of critically ill COVID-19 patients resulted in altered immunological and physiologic responses, some of which were associated with mortality.

Recent advances in critical care: Part II

With the increasing number of critically ill patients being admitted to intensive care units (ICUs), newer techniques and treatment modalities continue to evolve for their adequate management. Thus, it has become imperative to understand existing tools and resources, and utilise or repurpose them to achieve better results that can decrease morbidity and mortality. In this writeup, we chose five areas of interest, including analgosedation, role of colloids, recent advancements in the management of respiratory failure, the role of extracorporeal membrane oxygenation, and newer antimicrobials. The role of analgosedation in the critically ill has gained importance with focus on post-ICU syndromes, and albumin has re-entered the fray as a possible repairer of the injured glycocalyx. The coronavirus disease 2019 (COVID-19) pandemic forced us to relook at various ventilator strategies and mechanical support for the failing circulation has now become more common with clear end-points. Rising microbial antibiotic resistance has opened up the research on newer antibiotics.

The effects of female sexual hormones on the endothelial glycocalyx

The glycocalyx is a layer composed of carbohydrate side chains bound to core proteins that lines the vascular endothelium. The integrity of the glycocalyx is essential for endothelial cells' performance and vascular homeostasis. The neuroendocrine and immune systems influence the composition, maintenance, activity and degradation of the endothelial glycocalyx. The female organism has unique characteristics, and estrogen and progesterone, the main female hormones are essential to the development and physiology of the reproductive system and to the ability to develop a fetus. Female sex hormones also exert a wide variety of effects on other organs, including the vascular endothelium. They upregulate nitric oxide synthase expression and activity, decrease oxidative stress, increase vasodilation, and protect from vascular injury. This review will discuss how female hormones and pregnancy, which prompts to high levels of estrogen and progesterone, modulate the endothelial glycocalyx. Diseases prevalent in women that alter the glycocalyx, and therapeutic forms to prevent glycocalyx degradation and potential treatments that can reconstitute its structure and function will also be discussed.

Alterations in heparan sulfate proteoglycan synthesis and sulfation and the impact on vascular endothelial function

The glycocalyx attached to the apical surface of vascular endothelial cells is a rich network of proteoglycans, glycosaminoglycans, and glycoproteins with instrumental roles in vascular homeostasis. Given their molecular complexity and ability to interact with the intra- and extracellular environment, heparan sulfate proteoglycans uniquely contribute to the glycocalyx's role in regulating endothelial permeability, mechanosignaling, and ligand recognition by cognate cell surface receptors. Much attention has recently been devoted to the enzymatic shedding of heparan sulfate proteoglycans from the endothelial glycocalyx and its impact on vascular function. However, other molecular modifications to heparan sulfate proteoglycans are possible and may have equal or complementary clinical significance. In this narrative review, we focus on putative mechanisms driving non-proteolytic changes in heparan sulfate proteoglycan expression and alterations in the sulfation of heparan sulfate side chains within the endothelial glycocalyx. We then discuss how these specific changes to the endothelial glycocalyx impact endothelial cell function and highlight therapeutic strategies to target or potentially reverse these pathologic changes.