The Biomechanical Effects of Resuscitation Colloids on the Compromised Lung Endothelial Glycocalyx

Early high-volume resuscitation with crystalloid solution combined with albumin improves survival of critically ill patients: A retrospective analysis from MIMIC-IV database

BACKGROUND

Volume resuscitation is often required in critically ill patients. However, we have no clear consensus on the choice between crystalloid solution and colloidal solution. This study aimed to explore the effect of albumin administration in massive fluid resuscitation.

METHODS

This was a retrospective cohort study based on the Medical Information Mart for Intensive Care IV (MIMIC-IV) database (2008 and 2019). The prognosis of patients receiving albumin in combination with crystalloids and those receiving crystalloids alone was compared to assess the benefits of albumin in fluid resuscitation.

RESULTS

4426 patients received crystalloids alone (crystalloids group), 692 patients received albumin in combination with crystalloids within the first 24 h of initiation of crystalloids (early albumin combination group), and 382 patients received albumin after the first 24 h (late albumin combination group). Patients in early albumin combination group were more severe than those in Crystalloids group. Nevertheless, we found no statistically significant difference in mortality between the two groups. Multivariate logistic regression analysis using the propensity-score matched cohort showed that the 28-day and 60-day mortality in the early albumin combination group were lower than those in the crystalloids group (odds ratio: 0.64 [95% CI 0.50-0.82; P < 0.001] and 0.71 [95% CI 0.56-0.90; P = 0.004], respectively. Patients in early albumin combination group lived, on average, 1.16 days (95% CI 0.33-2.00; P < 0.01) and 3.3 days (95% CI 1.15-5.44; P < 0.01) longer than the crystalloids group during 28-day follow-up and 60-day follow-up.

CONCLUSION

Administration of albumin within 24 h after the initiation of crystalloids was associated with a lower mortality and a longer restricted mean survival time during 28-day follow-up and 60-day follow-up compared with crystalloid infusion alone. However, administration of albumin 24 h after the initiation of crystalloids was not associated with better prognosis compared to crystalloid infusion alone.

Serum adiponectin level is positively associated with vascular reactivity index by digital thermal monitoring in patients with coronary artery disease

Objectives

Adiponectin has anti-inflammatory and antiatherogenic effects and is important in the pathogenesis of cardiovascular diseases. In this cross-sectional study, our objective was to study the potential correlation between serum adiponectin levels and endothelial function in participants with coronary artery disease (CAD).

Materials and Methods

We collected serum specimens from 125 fasting participants with CAD. The endothelial function was measured using the vascular reactivity index (VRI) determined by digital thermal monitoring, and VRI values of >2.0, 1.0-1.9, and <1.0 indicated good, intermediate, and poor vascular reactivity, respectively. A commercially available enzyme immunoassay kit was used to measure serum adiponectin levels.

Results

The cohort included 55, 57, and 13 patients with good, intermediate, and poor vascular reactivity, respectively. Poor vascular reactivity was shown to be associated with older age, higher levels of serum total cholesterol, low-density lipoprotein cholesterol (LDL-C), C-reactive protein, and lower levels of serum albumin and adiponectin. The linear regression analysis with multivariable forward stepwise approach revealed that age (β = -0.232), serum LDL-C (β = -0.264), and serum adiponectin (β = 0.574) were correlated with the VRI in CAD patients significantly.

Conclusion

Fasting serum adiponectin levels were associated with good endothelial function determined using the VRI in patients with CAD.

The effect of tetrastarch on the endothelial glycocalyx layer in early hemorrhagic shock using fluorescence intravital microscopy: a mouse model

PURPOSE

To investigate vascular endothelial dysfunction based on glycocalyx impairment in massive hemorrhage and to evaluate fluid therapy.

METHODS

In this randomized controlled animal study, we withdrew 1.5 mL blood and administered 1.5 mL resuscitation fluid. Mice were divided into six groups according to the infusion type and administration timing: NS-NS (normal saline), NS-HES ([hydroxyethyl starch]130), HES-NS, NS-ALB (albumin), ALB-NS, and C (control) groups.

RESULTS

The glycocalyx index (GCXI) of a 40-μm artery was significantly larger in group C than in other groups (P < 0.01). Similarly, the GCXI for a 60-μm artery was significantly higher in group C than in NS-NS (P ≤ 0.05), NS-HES (P ≤ 0.01), and NS-ALB groups (P ≤ 0.05). The plasma syndecan-1 concentration, at 7.70 ± 5.71 ng/mL, was significantly lower in group C than in group NS-NS (P ≤ 0.01). The tetramethylrhodamine-labeled dextran (TMR-DEX40) fluorescence intensity in ALB-NS and HES-NS groups and the fluorescein isothiocyanate-labeled hydroxyethyl starch (FITC-HES130) fluorescence intensity in NS-HES and HES-NS groups were not significantly different from those of group C at any time point. FITC-HES130 was localized on the inner vessel wall in groups without HES130 infusion but uniformly distributed in HES130-treated groups in intravital microscopy. FITC-FITC-HES130 was localized remarkably in the inner vessel walls in group HES-NS in electron microscopy.

CONCLUSIONS

In an acute massive hemorrhage mouse model, initial fluid resuscitation therapy with saline administration impaired glycocalyx and increased vascular permeability. Prior colloid-fluid administration prevented the progression of glycocalyx damage and improve prognosis. Prior HES130 administration may protect endothelial cell function.

Endothelial glycocalyx in hepatopulmonary syndrome: An indispensable player mediating vascular changes

Hepatopulmonary syndrome (HPS) is a serious pulmonary vascular complication that causes respiratory insufficiency in patients with chronic liver diseases. HPS is characterized by two central pathogenic features-intrapulmonary vascular dilatation (IPVD) and angiogenesis. Endothelial glycocalyx (eGCX) is a gel-like layer covering the luminal surface of blood vessels which is involved in a variety of physiological and pathophysiological processes including controlling vascular tone and angiogenesis. In terms of lung disorders, it has been well established that eGCX contributes to dysregulated vascular contraction and impaired blood-gas barrier and fluid clearance, and thus might underlie the pathogenesis of HPS. Additionally, pharmacological interventions targeting eGCX are dramatically on the rise. In this review, we aim to elucidate the potential role of eGCX in IPVD and angiogenesis and describe the possible degradation-reconstitution equilibrium of eGCX during HPS through a highlight of recent literature. These studies strongly underscore the therapeutic rationale in targeting eGCX for the treatment of HPS.

Differential effects of obesity on visceral versus subcutaneous adipose arteries: role of shear-activated Kir2.1 and alterations to the glycocalyx

Obesity imposes well-established deficits to endothelial function. We recently showed that obesity-induced endothelial dysfunction was mediated by disruption of the glycocalyx and a loss of Kir channel flow sensitivity. However, obesity-induced endothelial dysfunction is not observed in all vascular beds: visceral adipose arteries (VAAs), but not subcutaneous adipose arteries (SAAs), exhibit endothelial dysfunction. To determine whether differences in SAA versus VAA endothelial function observed in obesity are attributed to differential impairment of Kir channels and alterations to the glycocalyx, mice were fed a normal rodent diet, or a high-fat Western diet to induce obesity. Flow-induced vasodilation (FIV) was measured ex vivo. Functional downregulation of endothelial Kir2.1 was accomplished by transducing adipose arteries from mice and obese humans with adenovirus containing a dominant-negative Kir2.1 construct. Kir function was tested in freshly isolated endothelial cells seeded in a flow chamber for electrophysiological recordings under fluid shear. Atomic force microscopy was used to assess biophysical properties of the glycocalyx. Endothelial dysfunction was observed in VAAs of obese mice and humans. Downregulating Kir2.1 blunted FIV in SAAs, but had no effect on VAAs, from obese mice and humans. Obesity abolished Kir shear sensitivity in VAA endothelial cells and significantly altered the VAA glycocalyx. In contrast, Kir shear sensitivity was observed in SAA endothelial cells from obese mice and effects on SAA glycocalyx were less pronounced. We reveal distinct differences in Kir function and alterations to the glycocalyx that we propose contribute to the dichotomy in SAA versus VAA endothelial function with obesity.NEW & NOTEWORTHY We identified a role for endothelial Kir2.1 in the differences observed in VAA versus SAA endothelial function with obesity. The endothelial glycocalyx, a regulator of Kir activation by shear, is unequally perturbed in VAAs as compared with SAAs, which we propose results in a near complete loss of VAA endothelial Kir shear sensitivity and endothelial dysfunction. We propose that these differences underly the preserved endothelial function of SAA in obese mice and humans.

Endothelial glycocalyx detection and characterization by means of atomic force spectroscopy: Comparison of various data analysis approaches

In recent years, atomic force spectroscopy (AFS) has been used to detect and characterize the endothelial glycocalyx (eGlx) in in vitro and ex vivo experiments. Several analysis methods were proposed, which differ not only in the numerical implementations, but also in physical models of glycocalyx description. Therefore, it is difficult to directly relate the experiments performed by different groups. In this work, we compared different models used for quantitative analysis of atomic force spectroscopy datasets recorded for eGlx. To capture glycocalyx at various structural conditions, we used basic enzymatic protocols for glycocalyx removal and restoration in human aortal endothelial cells (HAEC). Nanoindentation experiments for this model system were performed for (i) untreated cells, (ii) for cells after heparinase incubation, which enzymatically removes glycocalyx, (iii) for cells with successive heparin treatment, which partially restores the glycocalyx layer. Analysis of nanoindentation data was performed using different models: (a) a single-layer contact mechanics, (b) a double-layer model contact mechanics, (c) a polymer "brush" two-layer model based on the Alexander - de Gennes theory and (d) a simple single-layer "mechanical spring" model. Although different physical parameters are evaluated in methods (a-d), we show that all approaches revealed similar qualitative changes of the glycocalyx layer, which reflected the processes of glycocalyx degradation and its partial restoration. This paper may facilitate a direct comparison of past and future glycocalyx oriented AFS experiments that are analysed with different approaches.

Effects of 5% Albumin Plus Saline Versus Saline Alone on Outcomes From Large-Volume Resuscitation in Critically Ill Patients

OBJECTIVES

To compare 5% albumin with 0.9% saline for large-volume resuscitation (> 60 mL/Kg within 24 hr), on mortality and development of acute kidney injury.

DESIGN

Retrospective cohort study.

SETTING

Patients admitted to ICUs in 13 hospitals across Western Pennsylvania. We analyzed two independent cohorts, the High-Density Intensive Care databases: High-Density Intensive Care-08 (July 2000 to October 2008, H08) and High-Density Intensive Care-15 (October 2008 to December 2014, H15).

PATIENTS

Total of 18,629 critically ill patients requiring large-volume resuscitation.

INTERVENTIONS

Five percent of albumin in addition to saline versus 0.9% saline.

MEASUREMENTS AND MAIN RESULTS

After excluding patients with acute kidney injury prior to large-volume resuscitation, 673 of 2,428 patients (27.7%) and 1,814 of 16,201 patients (11.2%) received 5% albumin in H08 and H15, respectively. Use of 5% albumin was associated with decreased 30-day mortality by multivariate regression in H08 (odds ratio 0.65; 95% CI 0.49-0.85; p = 0.002) and in H15 (0.52; 95% CI 0.44-0.62; p < 0.0001) but was associated with increased acute kidney injury in H08 (odds ratio 1.98; 95% CI 1.56-2.51; p < 0.001) and in H15 (odds ratio 1.75; 95% CI 1.58-1.95; p < 0.001). However, 5% albumin was not associated with persistent acute kidney injury and resulted in decreased major adverse kidney event at 30, 90, and 365 days. Propensity matched analysis confirmed similar associations with mortality and acute kidney injury.

CONCLUSIONS

During large-volume resuscitation, 5% albumin was associated with reduced mortality and major adverse kidney event at 30, 90, and 365 days. However, a higher rate of acute kidney injury of any stage was observed that did not translate into persistent renal dysfunction.

Role of albumin in the preservation of endothelial glycocalyx integrity and the microcirculation: a review

The endothelial glycocalyx comprises a complex layer of membrane-bound proteoglycans, secreted glycosaminoglycans, glycoproteins, glycolipids and bound plasma proteins such as albumin and antithrombin associated with the endothelial surface. The glycocalyx plays an important role in vascular homeostasis, regulating vascular permeability and cell adhesion, and acts as a mechanosensor for hemodynamic shear stresses; it also has antithrombotic and anti-inflammatory functions. Plasma proteins such as albumin are physiologically bound within the glycocalyx, thus contributing to stability of the layer. Albumin is the major determinant of plasma colloid osmotic pressure. In addition, albumin transports sphingosine-1-phosphate which has protective endothelial effects, acts as a free radical scavenger, and has immunomodulatory and anti-inflammatory effects. This review examines the physiological function of the endothelial glycocalyx and the role of human albumin in preserving glycocalyx integrity and the microcirculation.

The Beneficial Effect of HES on Vascular Permeability and Its Relationship With Endothelial Glycocalyx and Intercellular Junction After Hemorrhagic Shock

Background

Vascular leakage is a common complication of hemorrhagic shock. Endothelial glycocalyx plays a crucial role in the protection of vascular endothelial barrier function. Hydroxyethyl starch (HES) is a commonly used resuscitation fluid for hemorrhagic shock. However, whether the protective effect of HES on vascular permeability after hemorrhagic shock is associated with the endothelial glycocalyx is unclear.

Methods

Using hemorrhagic shock rat model and hypoxia treated vascular endothelial cells (VECs), effects of HES (130/0.4) on pulmonary vascular permeability and the relationship to endothelial glycocalyx were observed.

Results

Pulmonary vascular permeability was significantly increased after hemorrhagic shock, as evidenced by the increased permeability of pulmonary vessels to albumin-fluorescein isothiocyanate conjugate (FITC-BSA) and Evans blue, the decreased transendothelial electrical resistance of VECs and the increased transmittance of FITC-BSA. The structure of the endothelial glycocalyx was destroyed, showing a decrease in thickness. The expression of heparan sulfate, hyaluronic acid, and chondroitin sulfate, the components of the endothelial glycocalyx, was significantly decreased. HES (130/0.4) significantly improved the vascular barrier function, recovered the thickness and the expression of components of the endothelial glycocalyx by down-regulating the expression of heparinase, hyaluronidase, and neuraminidase, and meanwhile increased the expression of intercellular junction proteins ZO-1, occludin, and VE-cadherin. Degradation of endothelial glycocalyx with degrading enzyme (heparinase, hyaluronidase, and neuraminidase) abolished the beneficial effect of HES on vascular permeability, but had no significant effect on the recovery of the expression of endothelial intercellular junction proteins induced by HES (130/0.4). HES (130/0.4) decreased the expression of cleaved-caspase-3 induced by hemorrhagic shock.

Conclusions

HES (130/0.4) has protective effect on vascular barrier function after hemorrgic shock.The mechanism is mainly related to the protective effect of HES on endothelial glycocalyx and intercellular junction proteins. The protective effect of HES on endothelial glycocalyx was associated with the down-regulated expression of heparinase, hyaluronidase, and neuraminidase. HES (130/0.4) had an anti-apoptotic effect in hemorrhagic shock.

The Endothelial Glycocalyx: A Fundamental Determinant of Vascular Permeability in Sepsis

OBJECTIVES

Sepsis is a significant cause of morbidity and mortality. Children with sepsis often have alterations in microcirculation and vascular permeability. Our objective is current evidence regarding the role of the endothelial glycocalyx as a determinant of capillary leakage in these patients.

DATA SOURCES

We reviewed PubMed, EMBASE, and Google scholar using MeSH terms "glycocalyx", "fluids", "syndecan", "endothelium", "vascular permeability", "edema", "sepsis", "septic shock", "children".

STUDY SELECTION

Articles in all languages were included. We include all studies in animals and humans related to glycocalyx and vascular permeability.

DATA EXTRACTION

Studies in children and adults, as well as animal studies, were included.

DATA SYNTHESIS

One of the fundamental components of the endothelial barrier structure is the glycocalyx. It is a variable thickness layer distributed throughout the whole body, which fulfills a very important function for life: the regulation of blood vessel permeability to water and solutes, favoring vascular protection, modulation, and hemostasis. In the last few years, there has been a special interest in glycocalyx disorders and their relationship to increased vascular permeability, especially in patients with sepsis in whom the alterations that occur in the glycocalyx are unknown when they are subjected to different water resuscitation strategies, vasopressors, etc. This review describes the structural and functional characteristics of the glycocalyx, alterations in patients with sepsis, with regard to its importance in vascular permeability conservation and the possible impact of strategies to prevent and/or treat the injury of this fundamental structure.

CONCLUSIONS

The endothelial glycocalyx is a fundamental component of the endothelium and an important determinant of the mechanotransduction and vascular permeability in patients with sepsis. Studies are needed to evaluate the role of the different types of solutions used in fluid bolus, vasoactive support, and other interventions described in pediatric sepsis on microcirculation, particularly on endothelial integrity and the glycocalyx.

Endothelial Glycocalyx Impairment in Disease: Focus on Hyaluronan Shedding

Hyaluronan (HA) is a ubiquitous glycosaminoglycan of the extracellular matrix. It is present in the endothelial glycocalyx covering the apical surface of endothelial cells. The endothelial glycocalyx regulates blood vessel permeability and homeostasis. HA plays a central role in numerous functions of the endothelial surface layer, protecting the endothelial cells, regulating the barrier permeability, and ensuring mechanosensing, which is essential to nitric oxide production and flow-induced vasodilation. During acute injury, inflammatory conditions, or many other pathologic conditions, the endothelial glycocalyx is damaged, and its degradation is accompanied by shedding of one or more glycocalyx components into the blood. Syndecan-1, heparan sulfate, and HA are the main components whose shedding has been claimed to represent the endothelial glycocalyx state of health. This review focuses on endothelial glycocalyx HA and highlights its key roles in the functions of the endothelial glycocalyx, its shedding in several pathologic conditions such as sepsis, diabetes, chronic and acute kidney injury, ischemia/reperfusion, atherosclerosis, and inflammation, which are all accompanied by increased circulating HA levels. Plasma/serum HA level is becoming recognized as a biomarker of endothelial glycocalyx damage in select pathologies. Hyaluronidase, the main HA-degrading enzyme, and its involvement in the impairment of endothelial glycocalyx are also addressed.

Childhood Obesity, Endothelial Cell Activation, and Critical Illness

Pediatric obesity is increasing in prevalence and is frequently an antecedent to adult obesity and adult obesity-associated morbidities such as atherosclerosis, type II diabetes, and chronic metabolic syndrome. Endothelial cell activation, one aspect of inflammation, is present in the early stages of atherosclerosis, often prior to the onset of symptoms. Endothelial activation is a pathological condition in which vasoconstricting, pro-thrombotic, and proliferative mediators predominate protective vasodilating, anti-thrombogenic, and anti-mitogenic mediators. Many studies report poor outcomes among obese children with systemic endothelial activation. Likewise, the link between childhood obesity and poor outcomes in critical illness is well-established. However, the link between obesity and severity of endothelial activation specifically in the setting of critical illness is largely unstudied. Although endothelial cell activation is believed to worsen disease in critically ill children, the nature and extent of this response is poorly understood due to the difficulty in measuring endothelial cell dysfunction and destruction. Based on the data available for the obese, asymptomatic population and the obese, critically ill population, the authors posit that obesity, and obesity-associated chronic inflammation, including oxidative stress and insulin resistance, may contribute to endothelial activation and associated worse outcomes among critically ill children. A research agenda to examine this hypothesis is suggested.

The protective effect of hydroxyethyl starch solution on the glycocalyx layer in an acute hemorrhage mouse model

PURPOSE

Fluid therapy focused on glycocalyx (GCX) protection in hemorrhagic shock is a current focus of research. Hydroxyethyl starch (HES) solution is commonly used for fluid resuscitation; however, its effects on the GCX remain unclear. The primary aim of this study was to explore the protective effect of HES130 in maintaining GCX thickness and reducing plasma syndecan-1 expression.

METHODS

An acute hemorrhage murine model with the dorsal skin chambers was used to measure GCX thickness and to evaluate vascular permeability. Groups of mice were treated with normal saline (NS), albumin (NS-A), HES130 (NS-V), or no exsanguination or infusion (C). We measured syndecan-1 plasma concentrations, performed blood gas analysis, and analyzed the 7-day cumulative mortality.

RESULTS

GCX thickness in NS mice was significantly reduced compared to that in group C, but no other groups showed a difference compared to group C. The plasma concentration of syndecan-1 was significantly higher in NS mice than in group C. There were no significant differences in the fluorescence intensity of dextran in the interstitial space. HES70 leakage was suppressed in NS-V mice compared to those in other groups. HES70 was localized to the inner vessel wall in C, NS, and NS-A mice, but not in group NS-V. Blood gas analysis indicated that pH and lactate showed the greatest improvements in NS-V mice. The 7-day cumulative mortality rate was the highest in group NS.

CONCLUSION

Resuscitation with HES130 protected the GCX and suppressed vascular permeability of HES70 during early stages of acute massive hemorrhage.

Colloids and the Microcirculation

Colloid solutions have been advocated for use in treating hypovolemia due to their expected effect on improving intravascular retention compared with crystalloid solutions. Because the ultimate desired effect of fluid resuscitation is the improvement of microcirculatory perfusion and tissue oxygenation, it is of interest to study the effects of colloids and crystalloids at the level of microcirculation under conditions of shock and fluid resuscitation, and to explore the potential benefits of using colloids in terms of recruiting the microcirculation under conditions of hypovolemia. This article reviews the physiochemical properties of the various types of colloid solutions (eg, gelatin, dextrans, hydroxyethyl starches, and albumin) and the effects that they have under various conditions of hypovolemia in experimental and clinical scenarios.

Derangement of the endothelial glycocalyx in sepsis

The vascular endothelial surface is coated by the glycocalyx, a ubiquitous gel-like layer composed of a membrane-binding domain that contains proteoglycans, glycosaminoglycan side-chains, and plasma proteins such as albumin and antithrombin. The endothelial glycocalyx plays a critical role in maintaining vascular homeostasis. However, this component is highly vulnerable to damage and is also difficult to examine. Recent advances in analytical techniques have enabled biochemical, visual and computational investigation of this vascular component. The glycocalyx modulates leukocyte-endothelial interactions, thrombus formation and other processes that lead to microcirculatory dysfunction and critical organ injury in sepsis. It also acts as a regulator of vascular permeability and contains mechanosensors as well as receptors for growth factors and anticoagulants. During the initial onset of sepsis, the glycocalyx is damaged and circulating levels of glycocalyx components, including syndecans, heparan sulfate and hyaluronic acid, can be measured and are reportedly useful as biomarkers for sepsis. Also, a new methodology using side-stream dark-field imaging is now clinically available for assessing the glycocalyx. Multiple factors including hypervolemia and hyperglycemia are toxic to the glycocalyx, and several agents have been proposed as therapeutic modalities, although no single treatment has been proven to be clinically effective. In this article, we review the derangement of the glycocalyx in sepsis. Despite the accumulated knowledge regarding the important roles of the glycocalyx, the relationship between derangement of the endothelial glycocalyx and severity of sepsis or disseminated intravascular coagulation has not been adequately elucidated and further work is needed.

Contrasting effects of albumin and hydroxyethyl starch solutions on physical properties of sodium hyaluronate solution

Hydroxyethyl starch (HES) solution reportedly sheds the endothelial surface layer (ESL) consisting of polysaccharide glycosaminoglycans, whereas albumin stabilizes the ESL. Here we compared the effects of albumin and HES (M_W 130,000) solutions on the physical properties of sodium hyaluronate (NaHA, M_W 1.3 × 10⁶) solution, a constituent of the ESL. Partial specific volumes (v) and intrinsic viscosities ([η]) of NaHA in 0.15 M NaCl solution containing albumin or HES (1-3%) were calculated from densities and viscosities extrapolated at infinite dilutions. Flow activation energy (E) of 0.2% NaHA in phosphate-buffered saline containing albumin or HES was obtained from the temperature-dependence of viscosities. A 3% albumin solution decreased v of NaHA by 3% compared to HES. A 3% HES solution, but not albumin, decreased [η] of NaHA by 34%, and decreased E values by 11% compared to albumin. These findings suggest that HES locally restricts NaHA dispersion, whereas albumin contracts NaHA structure.

Endothelial Glycocalyx as a Shield Against Diabetic Vascular Complications: Involvement of Hyaluronan and Hyaluronidases

The endothelial glycocalyx (EG), which covers the apical surface of the endothelial cells and floats into the lumen of the vessels, is a key player in vascular integrity and cardiovascular homeostasis. The EG is composed of PGs (proteoglycans), glycoproteins, glycolipids, and glycosaminoglycans, in particular hyaluronan (HA). HA seems to be implicated in most of the functions described for EG such as creating a space between blood and the endothelium, controlling vessel permeability, restricting leukocyte and platelet adhesion, and allowing an appropriate endothelial response to flow variation through mechanosensing. The amount of HA in the EG may be regulated by HYAL (hyaluronidase) 1, the most active somatic hyaluronidase. HYAL1 seems enriched in endothelial cells through endocytosis from the bloodstream. The role of the other main somatic hyaluronidase, HYAL2, in the EG is uncertain. Damage to the EG, accompanied by shedding of one or more of its components, is an early sign of various pathologies including diabetes mellitus. Shedding increases the blood or plasma concentration of several EG components, such as HA, heparan sulfate, and syndecan. The plasma levels of these molecules can then be used as sensitive markers of EG degradation. This has been shown in type 1 and type 2 diabetic patients. Recent experimental studies suggest that preserving the size and amount of EG HA in the face of diabetic insults could be a useful novel therapeutic strategy to slow diabetic complications. One way to achieve this goal, as suggested by a murine model of HYAL1 deficiency, may be to inhibit the function of HYAL1. The same approach may succeed in other pathological situations involving endothelial dysfunction and EG damage.

6% Hydroxyethyl starch (HES 130/0.4) diminishes glycocalyx degradation and decreases vascular permeability during systemic and pulmonary inflammation in mice

Background

Increased vascular permeability is a pathophysiological hallmark of sepsis and results in increased transcapillary leakage of plasma fluid, hypovolemia, and interstitial edema formation. 6% hydroxyethyl starch (HES 130/0.4) is commonly used to treat hypovolemia to maintain adequate organ perfusion and oxygen delivery. The present study was designed to investigate the effects of 6% HES 130/0.4 on glycocalyx integrity and vascular permeability in lipopolysaccharide (LPS)-induced pulmonary inflammation and systemic inflammation in mice.

Methods

6% HES 130/0.4 or a balanced electrolyte solution (20 ml/kg) was administered intravenously 1 h after cecal ligation and puncture (CLP) or LPS inhalation. Sham-treated animals receiving 6% HES 130/0.4 or the electrolyte solution served as controls. The thickness of the endovascular glycocalyx was visualized by intravital microscopy in lung (LPS inhalation model) or cremaster muscle (CLP model). Syndecan-1, hyaluronic acid, and heparanase levels were measured in blood samples. Vascular permeability in the lungs, liver, kidney, and brain was measured by Evans blue extravasation.

Results

Both CLP induction and LPS inhalation resulted in increased vascular permeability in the lung, liver, kidney, and brain. 6% HES 130/0.4 infusion led to significantly reduced plasma levels of syndecan-1, heparanase, and hyaluronic acid, which was accompanied by a preservation of the glycocalyx thickness in postcapillary venules of the cremaster (0.78 ± 0.09 μm vs. 1.39 ± 0.10 μm) and lung capillaries (0.81 ± 0.09 μm vs. 1.49 ± 0.12 μm).

Conclusions

These data suggest that 6% HES 130/0.4 exerts protective effects on glycocalyx integrity and attenuates the increase of vascular permeability during systemic inflammation.

Electronic supplementary material

The online version of this article (doi: 10.1186/s13054-017-1846-3) contains supplementary material, which is available to authorized users.