Plasma syndecan-1 is associated with fluid requirements and clinical outcomes in emergency department patients with sepsis

Glycosaminoglycans: Participants in Microvascular Coagulation of Sepsis

Sepsis represents a syndromic response to infection and frequently acts as a common pathway leading to fatality in the context of various infectious diseases globally. The pathology of severe sepsis is marked by an excess of inflammation and activated coagulation. A substantial contributor to mortality in sepsis patients is widespread microvascular thrombosis-induced organ dysfunction. Multiple lines of evidence support the notion that sepsis induces endothelial damage, leading to the release of glycosaminoglycans, potentially causing microvascular dysfunction. This review aims to initially elucidate the relationship among endothelial damage, excessive inflammation, and thrombosis in sepsis. Following this, we present a summary of the involvement of glycosaminoglycans in coagulation, elucidating interactions among glycosaminoglycans, platelets, and inflammatory cells. In this section, we also introduce a reasoned generalization of potential signal pathways wherein glycosaminoglycans play a role in clotting. Finally, we discuss current methods for detecting microvascular conditions in sepsis patients from the perspective of glycosaminoglycans. In conclusion, it is imperative to pay closer attention to the role of glycosaminoglycans in the mechanism of microvascular thrombosis in sepsis. Dynamically assessing glycosaminoglycan levels in patients may aid in predicting microvascular conditions, enabling the monitoring of disease progression, adjustment of clinical treatment schemes, and mitigation of both acute and long-term adverse outcomes associated with sepsis.

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.

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.

Increased R-spondin 3 contributes to aerobic exercise-induced protection against renal vascular endothelial hyperpermeability and acute kidney injury

AIM

Exercise training exerts protective effects against sepsis-associated multiple organ dysfunction. This study aimed to investigate whether aerobic exercise protected against sepsis-associated acute kidney injury (AKI) via modulating R-spondin 3 (RSPO3) expression.

METHODS

To investigate the effects of aerobic exercise on lipopolysaccharide (LPS)-induced AKI, LPS (20 mg/kg) was intraperitoneally injected after six weeks of treadmill training. To investigate the role of RSPO3 in LPS-induced AKI, wild-type (WT) or inducible endothelial cell-specific RSPO3 knockout (RSPO3EC-/- ) mice were intraperitoneally injected with 12 mg/kg LPS. RSPO3 was intraperitoneally injected 30 min before LPS treatment.

RESULTS

Aerobic exercise-trained mice were more resistant to LPS-induced body weight loss and hypothermia and had a significant higher survival rate than sedentary mice exposed to LPS. Exercise training restored the LPS-induced decreases in serum and renal RSPO3 levels. Exercise or RSPO3 attenuated, whereas inducible endothelial cell-specific RSPO3 knockout exacerbated LPS-induced renal glycocalyx loss, endothelial hyperpermeability, inflammation, and AKI. Bioinformatics analysis results revealed significant increases in the expression of matrix metalloproteinases (MMPs) in kidney tissues of mice exposed to sepsis or endotoxaemia, which was validated in renal tissue from LPS-exposed mice and LPS-treated human microvascular endothelial cells (HMVECs). Both RSPO3 and MMPs inhibitor restored LPS-induced downregulation of tight junction protein, adherens junction protein, and glycocalyx components, thus ameliorating LPS-induced endothelial leakage. Exercise or RSPO3 reversed LPS-induced upregulation of MMPs in renal tissues.

CONCLUSION

Increased renal expression of RSPO3 contributes to aerobic exercise-induced protection against LPS-induced renal endothelial hyperpermeability and AKI by suppressing MMPs-mediated disruption of glycocalyx and tight and adherens junctions.

Resuscitation-associated endotheliopathy (RAsE): a conceptual framework based on a systematic review and meta-analysis

INTRODUCTION

Shock-induced endotheliopathy (SHINE), defined as a profound sympathoadrenal hyperactivation in shock states leading to endothelial activation, glycocalyx damage, and eventual compromise of end-organ perfusion, was first described in 2017. The aggressive resuscitation therapies utilised in treating shock states could potentially lead to further worsening endothelial activation and end-organ dysfunction.

OBJECTIVE

This study aimed to systematically review the literature on resuscitation-associated and resuscitation-induced endotheliopathy.

METHODS

A predetermined structured search of literature published over an 11-year and 6-month period (1 January 2011 to 31 July 2023) was performed in two indexed databases (PubMed/MEDLINE and Embase) per PRISMA guidelines. Inclusion was restricted to original studies published in English (or with English translation) reporting on endothelial dysfunction in critically ill human subjects undergoing resuscitation interventions. Reviews or studies conducted in animals were excluded. Qualitative synthesis of studies meeting the inclusion criteria was performed. Studies reporting comparable biomarkers of endothelial dysfunction post-resuscitation were included in the quantitative meta-analysis.

RESULTS

Thirty-two studies met the inclusion criteria and were included in the final qualitative synthesis. Most of these studies (47%) reported on a combination of mediators released from endothelial cells and biomarkers of glycocalyx breakdown, while only 22% reported on microvascular flow changes. Only ten individual studies were included in the quantitative meta-analysis based on the comparability of the parameters assessed. Eight studies measured syndecan-1, with a heterogeneity index, I2 = 75.85% (pooled effect size, mean = 0.27; 95% CI - 0.07 to 0.60; p = 0.12). Thrombomodulin was measured in four comparable studies (I2 = 78.93%; mean = 0.41; 95% CI - 0.10 to 0.92; p = 0.12). Three studies measured E-selectin (I2 = 50.29%; mean =  - 0.15; 95% CI - 0.64 to 0.33; p = 0.53), and only two were comparable for the microvascular flow index, MFI (I2 = 0%; mean =  - 0.80; 95% CI - 1.35 to - 0.26; p < 0.01).

CONCLUSION

Resuscitation-associated endotheliopathy (RAsE) refers to worsening endothelial dysfunction resulting from acute resuscitative therapies administered in shock states. In the included studies, syndecan-1 had the highest frequency of assessment in the post-resuscitation period, and changes in concentrations showed a statistically significant effect of the resuscitation. There are inadequate data available in this area, and further research and standardisation of the ideal assessment and panel of biomarkers are urgently needed.

Exploring NT-proBNP, syndecan-1, and cytokines as biomarkers for transfusion-associated circulatory overload in a critically ill patient population receiving a single-unit red blood cell transfusion

BACKGROUND

Transfusion-associated circulatory overload (TACO) is an often underdiagnosed pulmonary transfusion complication. A biomarker could aid with the diagnosis. To date, B-type natriuretic peptide (BNP) and N-terminal prohormone B-type natriuretic peptide (NT-proBNP) seem the most promising biomarkers in the general hospital population. The aim was to evaluate NT-proBNP as a biomarker for TACO in a critically ill patient population and explore syndecan-1 and cytokines as other potential biomarkers.

STUDY DESIGN AND METHODS

A retrospective study was performed using samples and clinical data collected during a prospective observational study. Adult patients admitted to the intensive care and transfused with a single red blood cell unit were included. TACO cases were retrospectively identified using a case definition based on the current TACO definition. The primary biomarker was NT-proBNP, also we measured syndecan-1 IL-6, IL-8, and IL-10. All markers were measured directly before transfusion, 1 and 24 h after transfusion.

RESULTS

Our cohort included 64 patients, 12 of which were identified as TACO patients. TACO patients had a lower PaO2 /FiO2 ratio and were more often ventilated following transfusion compared to non-TACO patients. There was no significant difference in NT-proBNP between pre- and post-transfusion levels nor between TACO and non-TACO patients. Syndecan-1 was significantly elevated in TACO patients both pre- and post-transfusion compared to non-TACO patients.

DISCUSSION

NT-proBNP was not associated with TACO in this critically ill patient population. Interestingly, levels of syndecan-1 were increased in TACO patients at baseline. More research is needed to clarify this association and its possibilities as a biomarker to predict patients at risk for TACO.

Precision fluid and vasoactive drug therapy for critically ill patients

There are several clinical practice guidelines concerning the use of fluid and vasoactive drug therapies in critically ill adult patients, but the recommendations in these guidelines are often based on low-quality evidence. Further, some were compiled prior to the publication of landmark clinical trials, particularly in the comparison of balanced crystalloid and normal saline. An important consideration in the treatment of critically ill patients is the application of precision medicine to provide the most effective care to groups of patients most likely to benefit from the therapy. Although not currently widely integrated into these practice guidelines, the utility of precision medicine in critical illness is a recognized research priority for fluid and vasoactive therapy management. The purpose of this narrative review was to illustrate the evaluation and challenges of providing precision fluid and vasoactive therapies to adult critically ill patients. The review includes a discussion of important investigations published after the release of currently available clinical practice guidelines to provide insight into how recommendations and research priorities may change future guidelines and bedside care for critically ill patients.

Sulodexide improves vascular permeability via glycocalyx remodelling in endothelial cells during sepsis

Background

Degradation of the endothelial glycocalyx is critical for sepsis-associated lung injury and pulmonary vascular permeability. We investigated whether sulodexide, a precursor for the synthesis of glycosaminoglycans, plays a biological role in glycocalyx remodeling and improves endothelial barrier dysfunction in sepsis.

Methods

The number of children with septic shock that were admitted to the PICU at Children's Hospital of Fudan University who enrolled in the study was 28. On days one and three after enrollment, venous blood samples were collected, and heparan sulfate, and syndecan-1 (SDC1) were assayed in the plasma. We established a cell model of glycocalyx shedding by heparinase III and induced sepsis in a mouse model via lipopolysaccharide (LPS) injection and cecal ligation and puncture (CLP). Sulodexide was administrated to prevent endothelial glycocalyx damage. Endothelial barrier function and expression of endothelial-related proteins were determined using permeability, western blot and immunofluorescent staining. The survival rate, histopathology evaluation of lungs and wet-to-dry lung weight ratio were also evaluated.

Results

We found that circulating SDC1 levels were persistently upregulated in the non-alive group on days 1 and 3 and were positively correlated with IL-6 levels. Receiver operating characteristic curve analysis showed that SDC1 could distinguish patients with mortality. We showed that SDC1-shedding caused endothelial permeability in the presence of heparinase III and sepsis conditions. Mechanistically, sulodexide (30 LSU/mL) administration markedly inhibited SDC1 shedding and prevented endothelial permeability with zonula occludens-1 (ZO-1) upregulation via NF-κB/ZO-1 pathway. In mice with LPS and CLP-induced sepsis, sulodexide (40 mg/kg) administration decreased the plasma levels of SDC1 and increased survival rate. Additionally, sulodexide alleviated lung injury and restored endothelial glycocalyx damage.

Conlusions

In conclusion, our data suggest that SDC1 predicts prognosis in children with septic shock and sulodexide may have therapeutic potential for the treatment of sepsis-associated endothelial dysfunction.

Effect of intravenous fluid volume on biomarkers of endothelial glycocalyx shedding and inflammation during initial resuscitation of sepsis

PURPOSE

To investigate the effect of IV fluid resuscitation on endothelial glycocalyx (EG) shedding and activation of the vascular endothelium and inflammation.

MATERIALS AND METHODS

A planned biomarker sub-study of the REFRESH trial in which emergency department (ED) patients) with suspected sepsis and hypotension were randomised to a restricted fluid/early vasopressor regimen or IV fluid resuscitation with later vasopressors if required (usual care). Blood samples were collected at randomisation (T0) and at 3 h (T3), 6 h (T6)- and 24 h (T24) for measurement of a range of biomarkers if EG shedding, endothelial cell activation and inflammation.

RESULTS

Blood samples were obtained in 95 of 99 enrolled patients (46 usual care, 49 restricted fluid). Differences in the change in biomarker over time between the groups were observed for Hyaluronan (2.2-fold from T3 to T24, p = 0.03), SYN-4 (1.5-fold from T3 to T24, P = 0.01) and IL-6 (2.5-fold from T0 to T3, p = 0.03). No difference over time was observed between groups for the other biomarkers.

CONCLUSIONS

A consistent signal across a range of biomarkers of EG shedding or of endothelial activation or inflammation was not demonstrated. This could be explained by pre-existing EG shedding or overlap between the fluid volumes administered in the two groups in this clinical trial. Trial registration Australia New Zealand Clinical Trials Registry ACTRN126160000006448 Registered 12 January 2016.

Endothelial dysfunction and immunothrombosis in sepsis

Sepsis is a life-threatening clinical syndrome characterized by multiorgan dysfunction caused by a dysregulated or over-reactive host response to infection. During sepsis, the coagulation cascade is triggered by activated cells of the innate immune system, such as neutrophils and monocytes, resulting in clot formation mainly in the microcirculation, a process known as immunothrombosis. Although this process aims to protect the host through inhibition of the pathogen’s dissemination and survival, endothelial dysfunction and microthrombotic complications can rapidly lead to multiple organ dysfunction. The development of treatments targeting endothelial innate immune responses and immunothrombosis could be of great significance for reducing morbidity and mortality in patients with sepsis. Medications modifying cell-specific immune responses or inhibiting platelet–endothelial interaction or platelet activation have been proposed. Herein, we discuss the underlying mechanisms of organ-specific endothelial dysfunction and immunothrombosis in sepsis and its complications, while highlighting the recent advances in the development of new therapeutic approaches aiming at improving the short- or long-term prognosis in sepsis.

Elevated endothelial dysfunction-related biomarker levels indicate the severity and predict sepsis incidence

This study was conducted to investigate the relationship between serum endothelial dysfunction-related biomarker levels and organ dysfunction severity in septic patients and the predictive value of these levels during sepsis. In total, 105 patients admitted to the Department of Critical Care Medicine were enrolled between September 2020 and November 2021. Serum syndecan-1 and soluble thrombomodulin(sTM) levels were measured by enzyme-linked immunosorbent assay, and clinical and laboratory data were recorded. Enroll patients were divided into the infection (n = 28), septic nonshock (n = 31), and septic shock (n = 46) groups . Serum syndecan-1 (102.84 ± 16.53 vs. 55.38 ± 12.34 ng/ml), and sTM(6.60 ± 1.44 ng/ml vs. 5.23 ± 1.23 ng/ml, P < 0.01) levels were increased in the septic group compared with those in the infection group. Serum syndecan-1 levels were closely positively correlated with serum sTM (r_s = 0.712, r² = 0.507, P < 0.001). Additionally, serum syndecan-1(r_s = 0.687, r² = 0.472, P < 0.001) and sTM levels (r_s = 0.6, r² = 0.36, P < 0.01) levels were significantly positively correlated with the sequential organ failure assessment scores respectively. Syndecan-1 (AUC 0.95 ± 0.02, P < 0.0001) was more valuable for prediction sepsis than was sTM (AUC 0.87 ± 0.04, P < 0.0001). Compared with sTM (AUC 0.88 ± 0.03, P < 0.001), syndecan-1 (AUC 0.95 ± 0.02, P < 0.001) and SOFA score (AUC 0.95 ± 0.02, P < 0.001) were better predictors of septic shock. Serum syndecan-1 and sTM levels were associated with organ dysfunction severity in septic patients, and both were good predictors for early identification of sepsis, particularly in patients undergoing septic shock.

Biomarkers for the Prediction and Judgement of Sepsis and Sepsis Complications: A Step towards precision medicine?

Sepsis and septic shock are a major public health concern and are still associated with high rates of morbidity and mortality. Whilst there is growing understanding of different phenotypes and endotypes of sepsis, all too often treatment strategies still only employ a “one-size-fits-all” approach. Biomarkers offer a unique opportunity to close this gap to more precise treatment approaches by providing insight into clinically hidden, yet complex, pathophysiology, or by individualizing treatment pathways. Predicting and evaluating systemic inflammation, sepsis or septic shock are essential to improve outcomes for these patients. Besides opportunities to improve patient care, employing biomarkers offers a unique opportunity to improve clinical research in patients with sepsis. The high rate of negative clinical trials in this field may partly be explained by a high degree of heterogeneity in patient cohorts and a lack of understanding of specific endotypes or phenotypes. Moving forward, biomarkers can support the selection of more homogeneous cohorts, thereby potentially improving study conditions of clinical trials. This may finally pave the way to a precision medicine approach to sepsis, septic shock and complication of sepsis in the future.

No association between intravenous fluid volume and endothelial glycocalyx shedding in patients undergoing resuscitation for sepsis in the emergency department

Endothelial glycocalyx (EG) shedding is associated with septic shock and described following intravenous (IV) fluid administration. To investigate the possible impact of IV fluids on the pathobiology of septic shock we investigated associations between biomarkers of EG shedding and endothelial cell activation, and relationships with IV fluid volume. Serum samples were obtained on admission (T0) and at 24 h (T24) in patients undergoing haemodynamic resuscitation for suspected septic shock in the emergency department. Biomarkers of EG shedding—Syndecan-1 (Syn-1), Syndecan-4 (Syn-4), Hyaluronan, endothelial activation—Endothelin-1 (ET-1), Angiopoeitin-2 (Ang-2), Vascular Endothelial Growth Factor Receptor-1(VEGF-1) and leucocyte activation/inflammation—Resistin, Neutrophil Gelatinase Associated Lipocalin (NGAL) and a marker of cardiac stretch—Pro-Atrial Natriuretic Peptide (Pro-ANP) were compared to the total IV fluid volume administered using Tobit regression. Data on 86 patients (52 male) with a mean age of 60 (SD 18) years were included. The mean fluid volume administered to T24 was 4038 ml (SD 2507 ml). No significant association between fluid volume and Pro-ANP or any of the biomarkers were observed. Syn-1 and Syn-4 were significantly correlated with each other (Spearman Rho 0.43, p < 0.001) but not with Hyaluronan. Syn-1 and Syn-4 both correlated with VEGFR-1 (Rho 0.56 and 0.57 respectively, p < 0.001) whereas Hyaluronan correlated with ET-1 (Rho 0.43, p < 0.001) and Ang-2 (Rho 0.43, p < 0.001). There was no correlation between Pro-ANP and any of the EG biomarkers. Distinct patterns of association between biomarkers of EG shedding and endothelial cell activation were observed among patients undergoing resuscitation for sepsis. No relationship between IV fluid volume and Pro-ANP or any of the other biomarkers was observed.

Prognostic Value of Syndecan-1 in the Prediction of Sepsis-Related Complications and Mortality: A Meta-Analysis

Aim

Syndecan-1 (SDC-1) has been shown to have a high predictive value for sepsis development, though uncertainty around these results exists. The aim of this meta-analysis was to assess the prognostic ability of SDC-1 in predicting sepsis-related complications and mortality.

Methods

We searched PubMed, EMBASE, Cochrane Library, and Google Scholar databases from January 01, 1990, to March 17, 2021, to identify eligible studies. The search terms used were “SDC-1,” “sepsis,” “severe sepsis,” and “septic shock,” and a meta-analysis was performed using the RevMan 5.4 software.

Results

Eleven studies with a total of 2,318 enrolled patients were included. SDC-1 concentrations were significantly higher in the composite poor outcome group [standardized mean difference (SMD) = 0.55; 95% CI: 0.38–0.72; P < 0.001] as well as in deceased patients (SMD = 0.53; 95% CI: 0.40–0.67; P < 0.001), patients with septic shock (SMD = 0.81; 95% CI: 0.36–1.25; P < 0.001), and patients with acute kidney injury (SMD = 0.48; 95% CI: 0.33–0.62; P < 0.001). Statistical significance was also found in the subgroup analysis when stratified by different sepsis diagnostic criteria.

Conclusion

Baseline SDC-1 levels may be a useful predictor of sepsis-related complications and mortality.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021246344, PROSPERO, identifier: CRD42021246344.

Endothelial glycocalyx degradation during sepsis: Causes and consequences

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The endothelial glycocalyx is a ubiquitous intravascular structure essential for vascular homeostasis.

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During sepsis, the glycocalyx is degraded via the collective action of a variety of redundant sheddases, the regulation of which remains the focus of active investigation.

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Septic loss of the glycocalyx imparts both local vascular injury (leading to acute respiratory distress syndrome and acute kidney injury) as well as the systemic consequences of circulating glycosaminoglycan fragments (leading to cognitive dysfunction).

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Glycocalyx degradation during sepsis is potentially shaped by clinically-modifiable factors, suggesting opportunities for therapeutic intervention to mitigate the end-organ consequences of sepsis.

The glycocalyx is a ubiquitous structure found on endothelial cells that extends into the vascular lumen. It is enriched in proteoglycans, which are proteins attached to the glycosaminoglycans heparan sulfate, chondroitin sulfate, dermatan sulfate, keratan sulfate, and hyaluronic acid. In health and disease, the endothelial glycocalyx is a central regulator of vascular permeability, inflammation, coagulation, and circulatory tonicity. During sepsis, a life-threatening syndrome seen commonly in hospitalized patients, the endothelial glycocalyx is degraded, significantly contributing to its many clinical manifestations. In this review we discuss the intrinsically linked mechanisms responsible for septic endothelial glycocalyx destruction: glycosaminoglycan degradation and proteoglycan cleavage. We then examine the consequences of local endothelial glycocalyx loss to several organ systems and the systemic consequences of shed glycocalyx constituents. Last, we explore clinically relevant non-modifiable and modifiable factors that exacerbate or protect against endothelial glycocalyx shedding during sepsis.

Vascular Endothelial Glycocalyx Plays a Role in the Obesity Paradox According to Intravital Observation

According to the “obesity paradox,” for severe conditions, individuals with obesity may be associated with a higher survival rate than those who are lean. However, the physiological basis underlying the mechanism of the obesity paradox remains unknown. We hypothesize that the glycocalyx in obese mice is thicker and more resistant to inflammatory stress than that in non-obese mice. In this study, we employed intravital microscopy to elucidate the differences in the vascular endothelial glycocalyx among three groups of mice fed diets with different fat concentrations. Male C57BL/6N mice were divided into three diet groups: low-fat (fat: 10% kcal), medium-fat (fat: 45% kcal), and high-fat (fat: 60% kcal) diet groups. Mice were fed the respective diet from 3 weeks of age, and a chronic cranial window was installed at 8 weeks of age. At 9 weeks of age, fluorescein isothiocyanate-labeled wheat germ agglutinin was injected to identify the glycocalyx layer, and brain pial microcirculation was observed within the cranial windows. We randomly selected arterioles of diameter 15–45 μm and captured images. The mean index of the endothelial glycocalyx was calculated using image analysis and defined as the glycocalyx index. The glycocalyx indexes of the high-fat and medium-fat diet groups were significantly higher than those of the low-fat diet group (p < 0.05). There was a stronger positive correlation between vessel diameter and glycocalyx indexes in the high-fat and medium-fat diet groups than in the low-fat diet group. The glycocalyx indexes of the non-sepsis model in the obese groups were higher than those in the control group for all vessel diameters, and the positive correlation was also stronger. These findings indicate that the index of the original glycocalyx may play an important role in the obesity paradox.

Endothelial dysfunction: a therapeutic target in bacterial sepsis?

INTRODUCTION

Endothelial cells maintain vascular integrity, tone, and patency and have important roles in hemostasis and inflammatory responses. Although some degree of endothelial dysfunction with increased vascular permeability may be necessary to control local infection, excessive dysfunction plays a central role in the pathogenesis of sepsis-related organ dysfunction and failure as it results in dysregulated inflammation, vascular leakage, and abnormal coagulation. The vascular endothelium has thus been proposed as a potential target for therapeutic intervention in patients with sepsis.

AREAS COVERED

Different mechanisms underlying sepsis-related dysfunction of the vascular endothelium are discussed, including glycocalyx shedding, nitrosative stress, and coagulation factors. Potential therapeutic implications of each mechanism are mentioned.

EXPERT OPINION

Multiple targets to protect or restore endothelial function have been suggested, but endothelium-driven treatments remain a future potential at present. As some endothelial dysfunction and permeability may be necessary to remove infection and repair damaged tissue, targeting the endothelium may be a particular challenge. Ideally, therapies should be guided by biomarkers related to that specific pathway to ensure they are given only to patients most likely to respond. This enrichment based on biological plausibility and theragnostics will increase the likelihood of a beneficial response in individual patients and enable more personalized treatment.

The Endothelial Glycocalyx: Physiology and Pathology in Neonates, Infants and Children

The endothelial glycocalyx (EG) as part of the endothelial surface layer (ESL) is an important regulator of vascular function and homeostasis, including permeability, vascular tone, leukocyte recruitment and coagulation. Located at the interface between the endothelium and the blood stream, this highly fragile structure is prone to many disruptive factors such as inflammation and oxidative stress. Shedding of the EG has been described in various acute and chronic diseases characterized by endothelial dysfunction and angiopathy, such as sepsis, trauma, diabetes and cardiovascular disease. Circulating EG components including syndecan-1, hyaluronan and heparan sulfate are being evaluated in animal and clinical studies as diagnostic and prognostic markers in several pathologies, and advances in microscopic techniques have enabled in vivo assessment of the EG. While research regarding the EG in adult physiology and pathology has greatly advanced throughout the last decades, our knowledge of the development of the glycocalyx and its involvement in pathological conditions in the pediatric population is limited. Current evidence suggests that the EG is present early during fetal development and plays a critical role in vessel formation and maturation. Like in adults, EG shedding has been demonstrated in acute inflammatory conditions in infants and children and chronic diseases with childhood-onset. However, the underlying mechanisms and their contribution to disease manifestation and progression still need to be established. In the future, the glycocalyx might serve as a marker to identify pediatric patients at risk for vascular sequelae and as a potential target for early interventions.

Monitoring of the microcirculation in children undergoing major abdominal and thoracic surgery: A pilot study

BACKGROUND: Monitoring of the macrocirculation during surgery provides limited information on the quality of organ perfusion. OBJECTIVE: We investigated the feasibility of perioperative microcirculatory measurements in children. METHODS: Sublingual microvessels were visualized by handheld videomicroscopy in 11 children (19 mo – 10 yrs) undergoing surgery > 120 min at four time points: T0) after induction of anesthesia; T1) before end of anesthesia, T2) 6 h post surgery and T3) 24 h post surgery. RESULTS: Measurements were feasible in all children at T0 and T1. At T2 and T3, imaging was restricted to 6 and 4 infants, respectively, due to respiratory compromise and missing cooperation. The capillary density was reduced at T1 compared to T0 (8.1 mm/mm2 [4.0-17.0] vs. 10.6 mm/mm2 [5.1-19.3]; p = 0.01), and inversely related to norepinephrine dose (Pearson r = -0.65; p = 0.04). Microvascular flow and serum glycocalyx makers Syndecan-1 and Hyaluronan increased significantly from T0 to T1. CONCLUSION: Perioperative microcirculatory monitoring in children requires a high amount of personal and logistic resources still limiting its routine use. Major surgery is associated with microvascular alterations and glycocalyx perturbation. The possible consequences on patient outcome need further evaluation. Efforts should concentrate on the development of next generation devices designed to facilitate microcirculatory monitoring in children.