Three-dimensional ultrastructure of capillary endothelial glycocalyx under normal and experimental endotoxemic conditions

Tissue damage between barbed suture and conventional sutures in animal laboratory model using scanning electron microscopy

This study aimed to compare the tissue damage caused by barbed sutures and conventional sutures using scanning electron microscopy (SEM). Porcine myocardium was incised and sutured using different thread types: barbed suture, (STRATAFIX® Spiral PDS PLUS) and conventional sutures, (VICRYL® and PDS Plus®). Needle hole shapes were examined at magnifications of 30×-100×. VICRYL® suture damaged the tissue and created large gaps around the needle holes. The tissue around the needle holes was smoother and less damaged in the single suture ligations with PDS®; however, a large gap had formed. In the continuous suture with STRATAFIX®, the tissue around the needle holes was significantly smoother and minimally damaged, with no noticeable gaps around the needle holes. Barbed sutures reduced the load on needle holes and minimised tissue damage owing to the dispersion of traction forces by the barbs compared with conventional sutures.

Recombinant thrombomodulin and recombinant antithrombin attenuate pulmonary endothelial glycocalyx degradation and neutrophil extracellular trap formation in ventilator-induced lung injury in the context of endotoxemia

BACKGROUND

Vascular endothelial damage is involved in the development and exacerbation of ventilator-induced lung injury (VILI). Pulmonary endothelial glycocalyx and neutrophil extracellular traps (NETs) are endothelial protective and damaging factors, respectively; however, their dynamics in VILI and the effects of recombinant thrombomodulin and antithrombin on these dynamics remain unclear. We hypothesized that glycocalyx degradation and NETs are induced by VILI and suppressed by recombinant thrombomodulin, recombinant antithrombin, or their combination.

METHODS

VILI was induced in male C57BL/6J mice by intraperitoneal lipopolysaccharide injection (20 mg/kg) and high tidal volume ventilation (20 mL/kg). In the intervention groups, recombinant thrombomodulin, recombinant antithrombin, or their combination was administered at the start of mechanical ventilation. Glycocalyx degradation was quantified by measuring serum syndecan-1, fluorescence-labeled lectin intensity, and glycocalyx-occupied area in the pulmonary vascular lumen. Double-stranded DNA in the bronchoalveolar fluid and fluorescent areas of citrullinated histone H3 and myeloperoxidase were quantified as NET formation.

RESULTS

Serum syndecan-1 increased, and lectin fluorescence intensity decreased in VILI. Electron microscopy revealed decreases in glycocalyx-occupied areas within pulmonary microvessels in VILI. Double-stranded DNA levels in the bronchoalveolar lavage fluid and the fluorescent area of citrullinated histone H3 and myeloperoxidase in lung tissues increased in VILI. Recombinant thrombomodulin, recombinant antithrombin, and their combination reduced glycocalyx injury and NET marker levels. There was little difference in glycocalyx injury and NET makers between the intervention groups.

CONCLUSION

VILI induced glycocalyx degradation and NET formation. Recombinant thrombomodulin and recombinant antithrombin attenuated glycocalyx degradation and NETs in our VILI model. The effect of their combination did not differ from that of either drug alone. Recombinant thrombomodulin and antithrombin have the potential to be therapeutic agents for biotrauma in VILI.

Endothelial glycocalyx degradation in critically ill foals

BACKGROUND

Endothelial glycocalyx (EG) degradation occurs in septic humans and EG products can be used as biomarkers of endothelial injury. Information about EG biomarkers and their association with disease severity is lacking in hospitalized foals.

OBJECTIVES

Measure serum syndecan-1 (SDC-1), heparan sulfate (HS), angiopoietin-2 (ANG-2), aldosterone (ALD), and plasma atrial natriuretic peptide (ANP) concentrations and to determine their association with disease severity and death in hospitalized foals.

ANIMALS

Ninety foals ≤3 days old.

METHODS

Prospective, multicenter, longitudinal study. Foals were categorized into hospitalized (n = 74; 55 septic; 19 sick nonseptic) and 16 healthy foals. Serum ([SDC-1], [HS], [ANG-2], [ALD]) and plasma (ANP) were measured over 72 hours using immunoassays.

RESULTS

Serum ([SDC-1], [HS], [ANG-2], [ALD]) and plasma (ANP) were significantly higher in hospitalized and septic than healthy foals (P < .05). Serum (ANG-2) and plasma (ANP) were significantly higher in hospitalized nonsurvivors than in survivors (P < .05). On admission, hospitalized foals with serum (HS) > 58.7 ng/mL had higher odds of nonsurvival (odds ratio [OR] = 6.1; 95% confidence interval [CI] = 1.02-36.7). Plasma (ANP) >11.5 pg/mL was associated with the likelihood of nonsurvival in hospitalized foals (OR = 7.2; 95% CI = 1.4-37.4; P < .05). Septic foals with serum (ANG-2) >1018 pg/mL on admission had higher odds of nonsurvival (OR = 6.5; 95% CI =1.2-36.6; P < .05).

CONCLUSION AND CLINICAL IMPORTANCE

Critical illness in newborn foals is associated with EG degradation and injury, and these biomarkers are related to the severity of disease on admission and the outcome of sick foals.

HYDROGEN-RICH SALINE UPREGULATES THE SIRT1/NF-ΚB SIGNALING PATHWAY AND REDUCES VASCULAR ENDOTHELIAL GLYCOCALYX SHEDDING IN SEPSIS-INDUCED ACUTE KIDNEY INJURY

ABSTRACT

Sepsis causes dysfunction in different organs, but the pathophysiological mechanisms behind it are similar and mainly involve complex hemodynamic and cellular dysfunction. The importance of microcirculatory dysfunction in sepsis is becoming increasingly evident, in which endothelial dysfunction and glycocalyx degradation play a major role. This study aimed to investigate the effects of hydrogen-rich saline (HRS) on renal microcirculation in septic renal failure, and whether Sirt1 was involved in the renoprotective effects of HRS. Rats model of sepsis was established by cecal ligation and puncture, and septic rats were intraperitoneal injected with HRS (10 mL/kg). We found that in sepsis, the degree of glycocalyx shedding was directly proportional to the severity of sepsis. The seven-day survival rate of rats in the HRS+CLP group (70%) was higher than that of the CLP group (30%). HRS improved acidosis and renal function and reduced the release of inflammatory factors (TNF, IL-1β, and IL-6). The endothelial glycocalyx of capillaries in the HRS+CLP group (115 nm) was observed to be significantly thicker than that in the CLP group (44 nm) and EX527 (67.2 nm) groups by electron microscopy, and fewer glycocalyx metabolites (SDC-1, HS, HA, and MMP9) were found in the blood. Compared with the CLP group, HRS reduced renal apoptosis and upregulated Sirt1 expression, and inhibited the NF-κB/MMP9 signaling pathway. In addition, HRS did not damage immune function in septic rats as well. Generally speaking, our results suggest that HRS can alleviate the inflammatory response, inhibit glycocalyx shedding, improve septic kidney injury, and enhance survival rate.

Anatomy of blood microcirculation in the pig epicardial ganglionated nerve plexus

Embolization of coronary arteries and their terminal arterioles causes ischemia of all tissues distributed within a cardiac wall including the intrinsic cardiac ganglionated nerve plexus (ICGP). The disturbed blood supply to the ICGP causes chronic sympathetic activation with succeeding atrial and ventricular arrhythmias. This study analyses the anatomy of microcirculation of epicardial nerves and ganglia using the hearts of 11 domestic pigs. Our findings demonstrate that thicker epicardial nerves are normally supplied with blood via 12 epineural arterioles penetrating the endoneurium regularly along a nerve, and forming an endoneurial capillary network, which drains the blood into the myocardial blood flow. The mean diameter of intraneural capillaries was 7.2 ± 0.2 µm, while the diameters of arterioles were 25.8 ± 0.7 μm and involved 45 endothelial cells accompanied by circular smooth muscle cells. Usually, two or three arterioles with a mean diameter of 28.9 ± 1.7 μm supplied blood to any epicardial ganglion, in which arterioles proceeded into a network of capillaries with a mean diameter of 6.9 ± 0.3 μm. Both the epicardial nerves and the ganglia distributed near the porta venarum of the heart had tiny arterioles that anastomosed blood vessels from the right and the left coronary arteries. The density of blood vessels in the epicardial nerves was significantly lesser compared with the ganglia. Our electron microscopic observations provided evidence that blood vessels of the pig epicardial nerves and ganglia may be considered as either arterioles or capillaries that have quantitative and qualitative differences comparing to the corresponding blood vessels in humans and, therefore, a pig should not be considered as an animal model of the first choice for further heart functional studies seeking to improve the treatment of cardiac arrhythmias via trans-coronary cardiac neuroablation. STRUCTURED ABSTRACT: This study details the anatomy of microcirculation of epicardial nerves and ganglia, from which intracardiac nerves and bundles of nerve fibers extend into all layers of the atrial and ventricular walls in the most popular animal model of experimental cardiology and cardiac surgery - the domestic pig. Our findings provided evidence that blood vessels of the pig epicardial nerves and ganglia may be considered as either arterioles or capillaries that have quantitative and qualitative differences comparing to the corresponding blood vessels in humans and, therefore, a pig should not be considered as an animal model of the first choice for further heart functional studies seeking to improve the treatment of cardiac arrhythmias via trans-coronary cardiac neuroablation.

Mechanisms of triple-negative breast cancer extravasation: Impact of the physical environment and endothelial glycocalyx

Cancer metastasis is the leading cause of death for those afflicted with cancer. In cancer metastasis, the cancer cells break off from the primary tumor, penetrate nearby blood vessels, and attach and extravasate out of the vessels to form secondary tumors at distant organs. This makes extravasation a critical step of the metastatic cascade. Herein, with a focus on triple-negative breast cancer, the role that the prospective secondary tumor microenvironment's mechanical properties play in circulating tumor cells' extravasation is reviewed. Specifically, the effects of the physically regulated vascular endothelial glycocalyx barrier element, vascular flow factors, and subendothelial extracellular matrix mechanical properties on cancer cell extravasation are examined. The ultimate goal of this review is to clarify the physical mechanisms that drive triple-negative breast cancer extravasation, as these mechanisms may be potential new targets for anti-metastasis therapy.

Endothelial Glycocalyx in the Peripheral Capillaries is Injured Under Oxaliplatin-Induced Neuropathy

Oxaliplatin, a platinum-based anticancer drug, is associated with peripheral neuropathy (oxaliplatin-induced peripheral neuropathy, OIPN), which can lead to worsening of quality of life and treatment interruption. The endothelial glycocalyx, a fragile carbohydrate-rich layer covering the luminal surface of endothelial cells, acts as an endothelial gatekeeper and has been suggested to protect nerves, astrocytes, and other cells from toxins and substances released from the capillary vessels. Mechanisms underlying OIPN and the role of the glycocalyx remain unclear. This study aimed to define changes in the three-dimensional ultrastructure of capillary endothelial glycocalyx near nerve fibers in the hind paws of mice with OIPN. The mouse model of OPIN revealed disruption of the endothelial glycocalyx in the peripheral nerve compartment, accompanied by vascular permeability, edema, and damage to the peripheral nerves. To investigate the potential treatment interventions, nafamostat mesilate, a glycocalyx protective agent was used in tumor-bearing male mice. Nafamostat mesilate suppressed mechanical allodynia associated with neuropathy. It also prevented intra-epidermal nerve fiber loss and improved vascular permeability in the peripheral paws. The disruption of endothelial glycocalyx in the capillaries that lie within peripheral nerve bundles is a novel finding in OPIN. Furthermore, these findings point toward the potential of a new treatment strategy targeting endothelial glycocalyx to prevent vascular injury as an effective treatment of neuropathy as well as of many other diseases. PERSPECTIVE: OIPN damages the endothelial glycocalyx in the peripheral capillaries, increasing vascular permeability. In order to prevent OIPN, this work offers a novel therapy approach that targets endothelial glycocalyx.

Nafamostat mesylate decreases skin flap necrosis in a mouse model of type 2 diabetes by protecting the endothelial glycocalyx

The success rate of flap tissue reconstruction has increased in recent years owing to advancements in microsurgical techniques. However, complications, such as necrosis, are still more prevalent in diabetic patients compared to non-diabetic individuals, presenting an ongoing challenge. To address this issue, many previous studies have examined vascular anastomoses dilation and stability, primarily concerning surgical techniques or drugs. In contrast, in the present study, we focused on microvascular damage of the peripheral microvessels in patients with diabetes mellitus and the preventative impact of nafamostat mesylate. Herein, we aimed to investigate the effects of hyperglycemia on glycocalyx (GCX) levels in mice with type 2 diabetes. We examined the endothelial GCX (eGCX) in skin flap tissue of 9-12-week-old type 2 diabetic mice (db/db mice) using a perforator skin flap and explored treatment with nafamostat mesylate. The growth rates were compared after 1 week. Heterotype (db/+) mice were used as the control group. Morphological examination of postoperative tissues was performed at 1, 3, 5, and 7 days post-surgery. In addition, db/db mice were treated with 30 mg/kg/day of nafamostat mesylate daily and were evaluated on postoperative day 7. Seven days after surgery, all db/db mice showed significant partial flap necrosis. Temporal observation of the skin flaps revealed a stasis-like discoloration and necrosis starting from the contralateral side of the remaining perforating branch. The control group did not exhibit flap necrosis, and the flap remained intact. In the quantitative assessment of endothelial glycans using lectins, intensity scoring showed that the eGCX in the db/db group was significantly thinner than that in the db/+ group. These results were consistent with the scanning electron microscopy findings. In contrast, treatment with nafamostat mesylate significantly improved the flap engraftment rate and suppressed eGCX injury. In conclusion, treatment with nafamostat mesylate improves the disrupted eGCX structure of skin flap tissue in db/db mice, potentially ameliorating the impaired capillary-to-venous return in the skin flap tissue.

Doxycycline protects against sepsis-induced endothelial glycocalyx shedding

Endothelial glycocalyx (eGC) covers the inner surface of the vessels and plays a role in vascular homeostasis. Syndecan is considered the "backbone" of this structure. Several studies have shown eGC shedding in sepsis and its involvement in organ dysfunction. Matrix metalloproteinases (MMP) contribute to eGC shedding through their ability for syndecan-1 cleavage. This study aimed to investigate if doxycycline, a potent MMP inhibitor, could protect against eGC shedding in lipopolysaccharide (LPS)-induced sepsis and if it could interrupt the vascular hyperpermeability, neutrophil transmigration, and microvascular impairment. Rats that received pretreatment with doxycycline before LPS displayed ultrastructural preservation of the eGC observed using transmission electronic microscopy of the lung and heart. In addition, these animals exhibited lower serum syndecan-1 levels, a biomarker of eGC injury, and lower perfused boundary region (PBR) in the mesenteric video capillaroscopy, which is inversely related to the eGC thickness compared with rats that only received LPS. Furthermore, this study revealed that doxycycline decreased sepsis-related vascular hyperpermeability in the lung and heart, reduced neutrophil transmigration in the peritoneal lavage and inside the lungs, and improved some microvascular parameters. These findings suggest that doxycycline protects against LPS-induced eGC shedding, and it could reduce vascular hyperpermeability, neutrophils transmigration, and microvascular impairment.

Recombinant antithrombin attenuates acute kidney injury associated with rhabdomyolysis: an in vivo animal study

BACKGROUND

Rhabdomyolysis is characterized by the destruction and necrosis of skeletal muscle tissue, resulting in acute kidney injury (AKI). Recombinant antithrombin (rAT) has DNA repair and vascular endothelial-protection properties. Herein, we investigated whether rAT therapy has beneficial effects against rhabdomyolysis-induced AKI. Ten-week-old male B6 mice were injected with 5 mL/kg of 50% glycerol intramuscularly in the left thigh after 24 h of fasting to create a rhabdomyolysis mouse model. Further, 750 IU/kg rAT was injected intraperitoneally at 24 and 72 h after the rhabdomyolysis model was established. The mice were euthanized after 96 h for histological analysis. Saline was administered to mice in the control group.

RESULTS

Blood tests show elevated serum creatinine, urea nitrogen, and neutrophil gelatinase-associated lipocalin levels in rhabdomyolysis. Loss of tubular epithelial cell nuclei and destruction of the tubular luminal surface structure was observed in the untreated group, which improved with rAT treatment. Immunostaining for Ki-67 showed increased Ki-67-positive nuclei in the tubular epithelial cells in the rAT group, suggesting that rAT may promote tubular epithelial cell regeneration. The microvilli of the brush border of the renal tubules were shed during rhabdomyolysis, and rAT treatment reduced this injury. The vascular endothelial glycocalyx, which is usually impaired by rhabdomyolysis, became functional following rAT treatment.

CONCLUSIONS

Treatment with rAT suppressed rhabdomyolysis-induced AKI, suggesting that rAT therapy may be a novel therapeutic approach.

Prevention of vincristine-induced peripheral neuropathy by protecting the endothelial glycocalyx shedding

Vincristine-induced peripheral neuropathy (VIPN) adversely affects the quality of life and treatment continuity of patients. The endothelial glycocalyx (eGCX) protects nerves from harmful substances released from the capillary vessels, but its role in peripheral neuropathy remains unclear. We investigated the impact of eGCX protection on VIPN. Using a murine model of VIPN, we administered nafamostat mesylate to protect the eGCX shedding, and analyzed the eGCX integrity and manifestation of peripheral neuropathy. Nafamostat treatment suppressed allodynia associated with neuropathy. Additionally, nafamostat administration resulted in the suppression of increased vascular permeability in capillaries of peripheral nerves, further indicating its positive influence on eGCX in VIPN model mice. This study provided the importance of eGCX in VIPN. With the potential for rapid clinical translation through drug repositioning, nafamostat may be a new promising treatment for the prevention of VIPN.

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.

Fast-track preparation of lung specimens for electron microscope observations of the pulmonary endothelial glycocalyx

The glycocalyx (GCX) covers the luminal surface of blood vessels and regulates vascular permeability. As GCX degradation predicts various types of vasculopathy, confirming the presence of this structure is useful for diagnosis. Since the GCX layer is very fragile, careful fixation is necessary to preserve its structure. We explored appropriate and feasible methodologies for visualizing the GCX layer using lung tissue specimens excised from anesthetized mice. Each specimen was degassed and immersed in Alcian blue (ALB) fixative solution, and then observed using electron microscopy. Specimens from septic mice were prepared as negative GCX controls. Using these immersion-fixed specimens, the GCX layer was successfully observed using both transmission and scanning electron microscopy; these observations were similar to those obtained using the conventional method of lanthanum perfusion fixation. Spherical aggregates of GCX were observed in the septic mouse specimens, and the GCX density was lower in the septic specimens than in the non-septic specimens. Of note, the presently reported methodology reduced the specimen preparation time from 6 to 2 days. We, therefore, concluded that our novel method could be applied to human lung specimens and could potentially contribute to the further elucidation of vasculopathies.

Endothelial Glycocalyx of Peritubular Capillaries in Experimental Diabetic Nephropathy: A Target of ACE Inhibitor-Induced Kidney Microvascular Protection

Peritubular capillary rarefaction is a recurrent aspect of progressive nephropathies. We previously found that peritubular capillary density was reduced in BTBR ob/ob mice with type 2 diabetic nephropathy. In this model, we searched for abnormalities in the ultrastructure of peritubular capillaries, with a specific focus on the endothelial glycocalyx, and evaluated the impact of treatment with an angiotensin-converting enzyme inhibitor (ACEi). Mice were intracardially perfused with lanthanum to visualise the glycocalyx. Transmission electron microscopy analysis revealed endothelial cell abnormalities and basement membrane thickening in the peritubular capillaries of BTBR ob/ob mice compared to wild-type mice. Remodelling and focal loss of glycocalyx was observed in lanthanum-stained diabetic kidneys, associated with a reduction in glycocalyx components, including sialic acids, as detected through specific lectins. ACEi treatment preserved the endothelial glycocalyx and attenuated the ultrastructural abnormalities of peritubular capillaries. In diabetic mice, peritubular capillary damage was associated with an enhanced tubular expression of heparanase, which degrades heparan sulfate residues of the glycocalyx. Heparanase was also detected in renal interstitial macrophages that expressed tumor necrosis factor-α. All these abnormalities were mitigated by ACEi. Our findings suggest that, in experimental diabetic nephropathy, preserving the endothelial glycocalyx is important in order to protect peritubular capillaries from damage and loss.

A Disintegrin and Metalloproteinase with Thrombospondin Motifs 4 Regulates Pulmonary Vascular Hyperpermeability through Destruction of Glycocalyx in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) has no specific and effective treatment, and there is an urgent need to understand its pathogenesis. Therefore, based on the hypothesis that molecules whose expression is upregulated in injured pulmonary vascular endothelial cells (VECs) are involved in the pathogenesis of ARDS, we conducted a study to elucidate the molecular mechanisms and identify target factors for treatment. Primary human lung microvascular endothelial cells (HMVEC-Ls) were stimulated with lipopolysaccharide (LPS) or poly (I:C) and analyzed via a microarray to identify target genes for ARDS. We found that a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4) was induced in murine lung VECs in an LPS-mediated ARDS model. Elevated ADAMTS4 was also observed by the immunostaining of lung samples from ARDS patients. The suppression of ADAMTS4 by siRNA in VECs ameliorated LPS-stimulated vascular permeability. The impairment of the cell surface expression of syndecan-1, a marker of the glycocalyx that is an extracellular matrix involved in vascular permeability, was dramatically inhibited by ADAMTS4 suppression. In addition, the suppression of ADAMTS4 protected against LPS-induced reductions in syndecan-1 and the adherens junction protein vascular endothelial cadherin. These results suggest that ADAMTS4 regulates VEC permeability in ARDS and may be a predictive marker and therapeutic target for ARDS.

Blood Purification in Patients with Sepsis Associated with Acute Kidney Injury: A Narrative Review

Sepsis leads to organ dysfunction. Acute kidney injury, a common type of organ dysfunction, is associated with a high mortality rate in patients with sepsis. Kidney replacement therapy can correct the metabolic, electrolyte, and fluid imbalances caused by acute kidney injury. While this therapy can improve outcomes, evidence of its beneficial effects is lacking. Herein, we review the indications for blood purification therapy, including kidney replacement therapy, and the current knowledge regarding acute kidney injury in terms of renal and non-renal indications. While renal indications have been well-documented, indications for blood purification therapy in sepsis (non-renal indications) remain controversial. Excessive inflammation is an important factor in the development of sepsis; blood purification therapy has been shown to reduce inflammatory mediators and improve hemodynamic instability. Given the pathophysiology of sepsis, blood purification therapy may decrease mortality rates in these patients. Further trials are needed in order to establish the effectiveness of blood purification therapy for sepsis.

Endothelial cell activation and glycocalyx shedding - potential as biomarkers in patients with lupus nephritis

Lupus nephritis (LN) is a common and severe manifestation of systemic lupus erythematosus and an important cause of acute and chronic kidney injury. Early diagnosis of LN and preventing relapses are key to preserving renal reserve. However, due to the complexity and heterogeneity of the disease, clinical management remains challenging. Kidney biopsy remains the gold standard for confirming the diagnosis of LN and subsequent assessment of kidney histopathology, but it is invasive and cannot be repeated frequently. Current clinical indicators of kidney function such as proteinuria and serum creatinine level are non-specific and do not accurately reflect histopathological changes, while anti-dsDNA antibody and C3 levels reflect immunological status but not kidney injury. Identification of novel and specific biomarkers for LN is prerequisite to improve management. Renal function deterioration is associated with changes in the endothelial glycocalyx, a delicate gel-like layer located at the interface between the endothelium and bloodstream. Inflammation induces endothelial cell activation and shedding of glycocalyx constituents into the circulation. This review discusses the potential role of soluble glycocalyx components as biomarkers of active LN, especially in patients in whom conventional serological and biochemical markers do not appear helpful.

The unique structural and functional characteristics of glomerular endothelial cell fenestrations and their potential as a therapeutic target in kidney disease

Glomerular endothelial cell (GEnC) fenestrations are a critical component of the glomerular filtration barrier. Their unique nondiaphragmed structure is key to their function in glomerular hydraulic permeability, and their aberration in disease can contribute to loss of glomerular filtration function. This review provides a comprehensive update of current understanding of the regulation and biogenesis of fenestrae. We consider diseases in which GEnC fenestration loss is recognized or may play a role and discuss methods with potential to facilitate the study of these critical structures. Literature is drawn from GEnCs as well as other fenestrated cell types such as liver sinusoidal endothelial cells that most closely parallel GEnCs.

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.

Circulating Syndecan-1 Levels Are Associated with Chronological Coagulofibrinolytic Responses and the Development of Disseminated Intravascular Coagulation (DIC) after Trauma: A Retrospective Observational Study

BACKGROUND

The purpose of this study was to evaluate the association between endotheliopathy represented by high levels of circulating syndecan-1 (SDC-1) and coagulofibrinolytic responses due to trauma, which can lead to disseminated intravascular coagulation (DIC).

METHODS

We retrospectively evaluated 48 eligible trauma patients immediately admitted to our hospital and assessed SDC-1 and coagulofibrinolytic parameters for 7 days after admission. We compared the longitudinal changes of coagulofibrinolytic parameters and SDC-1 levels between two groups (high and low SDC-1) according to median SDC-1 value on admission.

RESULTS

The median circulating SDC-1 level was 99.6 (61.1-214.3) ng/mL on admission, and levels remained high until 7 days after admission. Coagulofibrinolytic responses assessed by biomarkers immediately after trauma were correlated with SDC-1 elevation (thrombin-antithrombin complex, TAT: r = 0.352, p = 0.001; antithrombin, AT: r = -0.301, p < 0.001; plasmin-α₂-plasmin inhibitor complex, PIC: r = 0.503, p = 0.035; tissue plasminogen activator, tPA: r = 0.630, p < 0.001). Sustained SDC-1 elevation was associated with intense and prolonged coagulation activation, impairment of anticoagulation, and fibrinolytic activation followed by inhibition of fibrinolysis, which are the primary responses associated with development of DIC in the acute phase of trauma. Elevation of circulating SDC-1 level was also associated with consumption coagulopathy and the need for transfusion, which revealed a significant association between high SDC-1 levels and the development of DIC after trauma (area under the curve, AUC = 0.845, cut-off value = 130.38 ng/mL, p = 0.001).

CONCLUSIONS

High circulating levels of syndecan-1 were associated with intense and prolonged coagulation activation, impairment of anticoagulation, fibrinolytic activation, and consumption coagulopathy after trauma. Endotheliopathy represented by SDC-1 elevation was associated with trauma induced coagulopathy, which can lead to the development of DIC.

The role of PLVAP in endothelial cells

Endothelial cells play a major part in the regulation of vascular permeability and angiogenesis. According to their duty to fit the needs of the underlying tissue, endothelial cells developed different subtypes with specific endothelial microdomains as caveolae, fenestrae and transendothelial channels which regulate nutrient exchange, leukocyte migration, and permeability. These microdomains can exhibit diaphragms that are formed by the endothelial cell-specific protein plasmalemma vesicle-associated protein (PLVAP), the only known protein component of these diaphragms. Several studies displayed an involvement of PLVAP in diseases as cancer, traumatic spinal cord injury, acute ischemic brain disease, transplant glomerulopathy, Norrie disease and diabetic retinopathy. Besides an upregulation of PLVAP expression within these diseases, pro-angiogenic or pro-inflammatory responses were observed. On the other hand, loss of PLVAP in knockout mice leads to premature mortality due to disrupted homeostasis. Generally, PLVAP is considered as a major factor influencing the permeability of endothelial cells and, finally, to be involved in the regulation of vascular permeability. Following these observations, PLVAP is debated as a novel therapeutic target with respect to the different vascular beds and tissues. In this review, we highlight the structure and functions of PLVAP in different endothelial types in health and disease.

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

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

Serum syndecan-1 concentration in hemolysis, elevated liver enzymes, and low platelets syndrome: A case report

Background

Hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome occurs in pregnant and postpartum individuals. We observed serum syndecan-1 (SDC-1) levels, which is a component of the glycocalyx, in a patient with HELLP syndrome from admission to the postpartum period and examined their association as reflecting the pathophysiology related to endothelial injury.

Case presentation

A 31-year-old primiparous female patient without a previous medical history at a gestational age of 37 weeks and 6 days was transferred to our hospital the morning after a visit to a previous hospital with headache and nausea. Elevated transaminase, platelet count, and proteinuria were noted. Head magnetic resonance imaging revealed a caudate nucleus hemorrhage and posterior reversible encephalopathy syndrome. After she delivered her newborn through an emergency cesarean section, she was admitted to the intensive care unit. On day 4 post-delivery, the patient’s D-dimer concentration was elevated, and contrast-enhanced computed tomography was performed. The results indicated pulmonary embolism, and heparin administration was initiated. The serum SDC-1 level was highest on day 1 post-delivery and quickly decreased subsequently; however, it remained elevated during the postpartum period. Her condition gradually improved, and she was extubated on day 6 and discharged from the ICU on day 7 post-delivery.

Conclusion

We measured SDC-1 concentration in a patient with HELLP syndrome and found that the clinical course correlated with SDC-1 levels, indicating that SDC-1 is elevated immediately before and after pregnancy termination in patients with HELLP syndrome. Therefore, SDC-1 fluctuations, combined with the elevation of the D-dimer level, may be a potential marker for the early detection of HELLP syndrome and estimation of the syndrome’s severity in the future.

Overview and New Insights into the Metabolic Syndrome: Risk Factors and Emerging Variables in the Development of Type 2 Diabetes and Cerebrocardiovascular Disease

Metabolic syndrome (MetS) is considered a metabolic disorder that has been steadily increasing globally and seems to parallel the increasing prevalence of obesity. It consists of a cluster of risk factors which traditionally includes obesity and hyperlipidemia, hyperinsulinemia, hypertension, and hyperglycemia. These four core risk factors are associated with insulin resistance (IR) and, importantly, the MetS is known to increase the risk for developing cerebrocardiovascular disease and type 2 diabetes mellitus. The MetS had its early origins in IR and syndrome X. It has undergone numerous name changes, with additional risk factors and variables being added over the years; however, it has remained as the MetS worldwide for the past three decades. This overview continues to add novel insights to the MetS and suggests that leptin resistance with hyperleptinemia, aberrant mitochondrial stress and reactive oxygen species (ROS), impaired folate-mediated one-carbon metabolism with hyperhomocysteinemia, vascular stiffening, microalbuminuria, and visceral adipose tissues extracellular vesicle exosomes be added to the list of associated variables. Notably, the role of a dysfunctional and activated endothelium and deficient nitric oxide bioavailability along with a dysfunctional and attenuated endothelial glycocalyx, vascular inflammation, systemic metainflammation, and the important role of ROS and reactive species interactome are discussed. With new insights and knowledge regarding the MetS comes the possibility of new findings through further research.

Exploring the pathophysiological mechanism of interstitial edema focusing on the role of macrophages and their interaction with the glycocalyx

OBJECTIVES

Glycocalyx lines the vascular intraluminal space that regulates fluid movement between the intra- and extra-vascular compartments. The depletion of glycocalyx (GCX) is associated with leukocyte accumulation, possibly causing the endothelial cells to become hyperpermeable in various organs, including oral tissues. Whether neutrophils or macrophages are responsible for developing interstitial edema remains controversial. We explored the pathophysiological mechanism of interstitial edema by examining the role of reactive neutrophils and macrophages and their interactions with GCX.

METHODS

An anti-MHC class I antibody was administered intravenously to male BALB/c mice to induce pulmonary edema. Pulmonary edema was evaluated by measuring the lung wet-to-dry weight ratio. Changes in the GCX were evaluated by electron microscopy and measurements of the serum level of soluble syndecan-1. Heparin sulfate was administered to examine its protective effect on the GCX. The macrophages were depleted using clodronate to examine their role in developing edema.

RESULTS

The GCX degradation induced by the anti-MHC class I antibody was accompanied by increased serum syndecan-1 and heparan sulfate levels. Macrophage depletion inhibited the development of pulmonary edema, and the administration of supplemental heparin suppressed the edema.

CONCLUSIONS

We demonstrated that the degradation of the GCX induced by the anti-MHC class I antibody was suppressed by macrophage depletion. These results suggest that macrophages may play a key role in interstitial edema. Heparin inhibited both the degradation of the GCX and interstitial edema. This study's results may be extrapolated to develop an interventional strategy for inhibiting interstitial edema in various organs.

Mechanobiological modulation of blood-brain barrier permeability by laser stimulation of endothelial-targeted nanoparticles

The blood-brain barrier (BBB) maintains an optimal environment for brain homeostasis but excludes most therapeutics from entering the brain. Strategies that reversibly increase BBB permeability are essential for treating brain diseases and are the focus of significant preclinical and translational interest. Picosecond laser excitation of tight junction-targeted gold nanoparticles (AuNPs) generates a nanoscale mechanical perturbation and induces a graded and reversible increase in BBB permeability (OptoBBB). Here we advanced this technique by showing that targeting endothelial glycoproteins leads to >10-fold higher targeting efficiency than targeting tight junctions both in vitro and in vivo. With both tight-junction and glycoprotein targeting, we demonstrate that OptoBBB is associated with a transient elevation and propagation of Ca2+, actin polymerization, and phosphorylation of ERK1/2 (extracellular signal-regulated protein kinase). These collectively activate the cytoskeleton resulting in increased paracellular permeability. The Ca2+ response involves internal Ca2+ depletion and Ca2+ influx with contributions from mechanosensitive ion channels (TRPV4, Piezo1). We provide insight into how the excitation of tight junction protein (JAM-A)-targeted and endothelial (glycocalyx)-targeted AuNPs leads to similar mechanobiological modulation of BBB permeability while targeting the glycocalyx significantly improves the nanoparticle accumulation in the brain. The results will be critical for guiding the future development of this technology for brain disease treatment.

Gemcitabine alters sialic acid binding of the glycocalyx and induces inflammatory cytokine production in cultured endothelial cells

Gemcitabine (GEM) is an anticancer drug inhibiting DNA synthesis. Glomerular thrombotic microangiopathy (TMA) has been reported as an adverse effect. However, the precise mechanism of GEM-induced endothelial injury remains unknown. Cultured human umbilical vein endothelial cells (HUVECs) in the confluent phase were exposed to GEM (5-100 μM) for 48 h and evaluated cell viability and morphology, lectin binding concerning sialic acid of endothelial glycocalyx (GCX), and immunofluorescent staining of platelet-endothelial cell adhesion molecule (PECAM) and vascular endothelial growth factor receptor 2 (VEGFR2). The mRNA expression of α2,6-sialyltransferase (ST6Gal1), sialidase (neuraminidase-1: NEU-1), and interleukin (IL)-1β and IL-6 was also evaluated. GEM exposure at 5 μM induced cellular shrinkage and intercellular dissociation, accompanied by slight attenuation of PECAM and VEGFR2 immunostaining, although cell viability was still preserved. At this concentration, lectin binding showed a reduction of terminal sialic acids in endothelial GCX, probably associated with reduced ST6Gal1 mRNA expression. IL-1β and IL-6 mRNA expression was significantly increased after GEM exposure. GEM reduced terminal sialic acids in endothelial GCX through mRNA suppression of ST6Gal1 and induced inflammatory cytokine production in HUVECs. This phenomenon could be associated with the mechanism of GEM-induced TMA.

In Vivo Profiling of the Vascular Cell Surface Proteome in Murine Models of Bacteremia

Vascular dysfunction is a hallmark of systemic inflammatory responses such as bacterial sepsis. The luminal surface of the blood vessels is coated with a dense layer of glycans and proteoglycans, collectively known as the glycocalyx. Surface associated glycoproteins of endothelial origin, or derived from pericytes, intravascular leukocytes, and plasma, are other important components of the glycocalyx, constituting a vascular cell surface proteome that is dynamic, tissue-specific, and sensitive to changes in vascular homeostasis, blood infection, and inflammation. Here, we describe an experimental protocol to chemically tag and quantify the vascular cell surface proteome in murine models of bacteremia, in a time-resolved and organ-specific manner. This method facilitates the identification of markers of vascular activation and provides a molecular framework to understand the contribution of vascular dysfunction to the organ pathology of systemic inflammation.

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

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

The Endothelial Glycocalyx and Neonatal Sepsis

Sepsis carries a substantial risk of morbidity and mortality in newborns, especially preterm-born neonates. Endothelial glycocalyx (eGC) is a carbohydrate-rich layer lining the vascular endothelium, with important vascular barrier function and cell adhesion properties, serving also as a mechano-sensor for blood flow. eGC shedding is recognized as a fundamental pathophysiological process generating microvascular dysfunction, which in turn contributes to multiple organ failure and death in sepsis. Although the disruption of eGC and its consequences have been investigated intensively in the adult population, its composition, development, and potential mechanisms of action are still poorly studied during the neonatal period, and more specifically, in neonatal sepsis. Further knowledge on this topic may provide a better understanding of the molecular mechanisms that guide the sepsis pathology during the neonatal period, and would increase the usefulness of endothelial glycocalyx dysfunction as a diagnostic and prognostic biomarker. We reviewed several components of the eGC that help to deeply understand the mechanisms involved in the eGC disruption during the neonatal period. In addition, we evaluated the potential of eGC components as biomarkers and future targets to develop therapeutic strategies for neonatal sepsis.

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.

Endogenous Glycosaminoglycans in Various Pathologic Plasma Samples as Measured by a Fluorescent Quenching Method

Endogenous glycosaminoglycans (GAGs) with a similar structure to heparin are widely distributed in various tissues. A fluorescence probe, namely Heparin Red, can detect polyanionic GAGs in plasma samples. The purpose of this study is to measure endogenous GAGs in various plasma samples obtained from different pathologic states in comparison to healthy controls utilizing this method. Plasma samples were obtained from patient groups including atrial fibrillation (AF), end-stage-renal-disease (ESRD), diabetes mellitus (DM), sepsis, cancer, liver disease (LD), and pulmonary embolism (PE). Normal human plasma (NHP) was used as healthy controls. The Heparin Red kit from Red Probes (Münster, Germany) was used for the quantification of endogenous GAGs in each sample before and after heparinase I degradation. All results were compiled as group means  ±  SD for comparison. NHP was found to have relatively low levels of endogenous GAGs with a mean concentration of 0.06 μg/mL. The AF, ESRD, DM, and sepsis patient samples had a mean endogenous GAG concentration of 0.55, 0.72, 0.92, and 0.94 μg/mL, respectively. The levels of endogenous GAGs were highest in cancer, LD, and PE patient plasma samples with a mean concentration of 1.95, 2.78, and 2.83 μg/mL, respectively. Heparinase I degradation resulted in a decline in GAG levels in plasma samples. These results clearly show that detectable Heparin Red sensitive endogenous GAGs are present in circulating plasma at varying levels in various patient groups. Additional studies are necessary to understand this complex pathophysiology.

Recombinant thrombomodulin may protect cardiac capillary endothelial glycocalyx through promoting Glypican-1 expression under experimental endotoxemia

Introduction

Myocardial dysfunction occurs in patients with sepsis due to vascular endothelial injury. Recombinant human thrombomodulin (rhTM) attenuates vascular endothelial injuries through endothelial glycocalyx (eGC) protection.

Hypothesis

We hypothesized that rhTM attenuates myocardial dysfunction via the inhibition of vascular endothelial injury during sepsis.

Methods

Ten-week-old male C57BL6 mice were injected intraperitoneally with 20 mg/kg of lipopolysaccharide (LPS). In rhTM-treated mice, rhTM was injected intraperitoneally at 3 and 24 h after LPS injection. Saline was injected intraperitoneally as control. To assess for eGC injury, intensity score was measured 48 h after the LPS injection. To confirm vascular endothelial injuries, ultrastructural analysis was performed using scanning (SEM) and transmission electron microscopy (TEM).

Results

The survival rate of the rhTM group at 48 h after LPS injection was significantly higher than that of the control group (68% vs. 17%, p < 0.05). The serum level of troponin I in the rhTM group was lower than that in the control (2.2 ± 0.4 ng/dL vs 9.4 ± 1.1 ng/dL, p < 0.05). The expression of interleukin-6 (IL-6) was attenuated in the rhTM-treated group than in the control (65.3 ± 15.3 ng/mL vs 226.3 ± 19.4 ng/mL, p < 0.05). The serum concentration of syndecan-1, a marker of glycocalyx damage, was significantly decreased 48 h post-administration of LPS in the rhTM-treated group than in the control group. In ultrastructural analysis using SEM and TEM, eGC peeled off from the surface of the capillary lumen in the control. Conversely, the eGC injury was attenuated in the rhTM group. Gene set enrichment analysis revealed that osteomodulin, osteoglycin proline/arginine-rich end leucine-rich repeat protein, and glypican-1, which are proteoglycans, were preserved by rhTM treatment. Their protein expression was retained in endothelial cells.

Conclusion

rhTM attenuates sepsis-induced myocardial dysfunction via eGC protection.

Glycocalyx Components Detune the Cellular Uptake of Gold Nanoparticles in a Size- and Charge-Dependent Manner

Functionalized nanoparticles (NPs) are widely used in targeted drug delivery and biomedical imaging due to their penetration into living cells. The outer coating of most cells is a sugar-rich layer of the cellular glycocalyx, presumably playing an important part in any uptake processes. However, the exact role of the cellular glycocalyx in NP uptake is still uncovered. Here, we in situ monitored the cellular uptake of gold NPs─functionalized with positively charged alkaline thiol (TMA)─into adhered cancer cells with or without preliminary glycocalyx digestion. Proteoglycan (PG) components of the glycocalyx were treated by the chondroitinase ABC enzyme. It acts on chondroitin 4-sulfate, chondroitin 6-sulfate, and dermatan sulfate and slowly on hyaluronate. The uptake measurements of HeLa cells were performed by applying a high-throughput label-free optical biosensor based on resonant waveguide gratings. The positively charged gold NPs were used with different sizes [d = 2.6, 4.2, and 7.0 nm, small (S), medium (M), and large(L), respectively]. Negatively charged citrate-capped tannic acid (CTA, d = 5.5 nm) NPs were also used in control experiments. Real-time biosensor data confirmed the cellular uptake of the functionalized NPs, which was visually proved by transmission electron microscopy. It was found that the enzymatic digestion facilitated the entry of the positively charged S- and M-sized NPs, being more pronounced for the M-sized. Other enzymes digesting different components of the glycocalyx were also employed, and the results were compared. Glycosaminoglycan digesting heparinase III treatment also increased, while glycoprotein and glycolipid modifying neuraminidase decreased the NP uptake by HeLa cells. This suggests that the sialic acid residues increase, while heparan sulfate decreases the uptake of positively charged NPs. Our results raise the hypothesis that cellular uptake of 2-4 nm positively charged NPs is facilitated by glycoprotein and glycolipid components of the glycocalyx but inhibited by PGs.

The glycocalyx as a permeability barrier: basic science and clinical evidence

Preclinical studies in animals and human clinical trials question whether the endothelial glycocalyx layer is a clinically important permeability barrier. Glycocalyx breakdown products in plasma mostly originate from 99.6–99.8% of the endothelial surface not involved in transendothelial passage of water and proteins. Fragment concentrations correlate poorly with in vivo imaging of glycocalyx thickness, and calculations of expected glycocalyx resistance are incompatible with measured hydraulic conductivity values. Increases in plasma breakdown products in rats did not correlate with vascular permeability. Clinically, three studies in humans show inverse correlations between glycocalyx degradation products and the capillary leakage of albumin and fluid.

Form follows function: The endothelial glycocalyx

Three types of capillaries, namely continuous, fenestrated, and sinusoidal, form the microvascular system; each type has a specialized structure and function to respond to the demands of the organs they supply. The endothelial glycocalyx, a gel-like layer of glycoproteins that covers the luminal surface of the capillary endothelium, is also thought to maintain organ and vascular homeostasis by exhibiting different morphologies based on the functions of the organs and capillaries in which it is found. Recent advances in analytical technology have enabled more detailed observations of the endothelial glycocalyx, revealing that it indeed differs in structure across various organs. Furthermore, differences in the lectin staining patterns suggest the presence of different endothelial glycocalyx components across various organs. Interestingly, injury to the endothelial glycocalyx due to various pathologic and physiological stimuli causes the release of these components into the blood. Thus, circulating glycocalyx components may be useful biomarkers of organ dysfunction and disease severity. Moreover, a recent study suggested that chronic injury to the glycocalyx reduces the production of these glycocalyx components and changes their structure, leading it to become more vulnerable to external stimuli. In this review, we have summarized the various endothelial glycocalyx structures and their functions.

Endothelial Glycocalyx Degradation in Critical Illness and Injury

The endothelial glycocalyx is a gel-like layer on the luminal side of blood vessels that is composed of glycosaminoglycans and the proteins that tether them to the plasma membrane. Interest in its properties and function has grown, particularly in the last decade, as its importance to endothelial barrier function has come to light. Endothelial glycocalyx studies have revealed that many critical illnesses result in its degradation or removal, contributing to endothelial dysfunction and barrier break-down. Loss of the endothelial glycocalyx facilitates the direct access of immune cells and deleterious agents (e.g., proteases and reactive oxygen species) to the endothelium, that can then further endothelial cell injury and dysfunction leading to complications such as edema, and thrombosis. Here, we briefly describe the endothelial glycocalyx and the primary components thought to be directly responsible for its degradation. We review recent literature relevant to glycocalyx damage in several critical illnesses (sepsis, COVID-19, trauma and diabetes) that share inflammation as a common denominator with actions by several common agents (hyaluronidases, proteases, reactive oxygen species, etc.). Finally, we briefly cover strategies and therapies that show promise in protecting or helping to rebuild the endothelial glycocalyx such as steroids, protease inhibitors, anticoagulants and resuscitation strategies.

Single-cell adhesivity distribution of glycocalyx digested cancer cells from high spatial resolution label-free biosensor measurements

The glycocalyx is a cell surface sugar layer of most cell types that greatly influences the interaction of cells with their environment. Its components are glycolipids, glycoproteins, and oligosaccharides. Interestingly, cancer cells have a thicker glycocalyx layer compared to healthy cells, but to date, there has been no consensus in the literature on the exact role of cell surface polysaccharides and their derivatives in cellular adhesion and signaling. In our previous work we discovered that specific glycocalyx components of cancer cells regulate the kinetics and strength of adhesion on RGD (arginine-glycine-aspartic acid) peptide-coated surfaces [1]. Depending on the employed enzyme concentration digesting specific components both adhesion strengthening and weakening could be observed by monitoring the averaged behavior of thousands of cells. The enzyme chondroitinase ABC (ChrABC) was used to digest the chondroitin-4-sulfate, chondroitin-6-sulfate, and dermatan sulfate components in the glycocalyx of cancer cells. In the present work, a high spatial resolution label-free optical biosensor was employed to monitor the adhesivity of cancer cells both at the single-cell and population level. Population-level distributions of single-cell adhesivity were first recorded and analyzed when ChrABC was added to the adhering cells. At relatively low and high ChrABC concentrations subpopulations with remarkably large and weak adhesivity were identified. The changes in the adhesivity distribution due to the enzyme treatment were analyzed and the subpopulations most affected by the enzyme treatment were highlighted. The presented results open up new directions in glycocalyx related cell adhesion research and in the development of more meaningful targeted cancer treatments affecting adhesion.

The Endothelial Glycocalyx: A Possible Therapeutic Target in Cardiovascular Disorders

The physiological, anti-inflammatory, and anti-coagulant properties of endothelial cells (ECs) rely on a complex carbohydrate-rich layer covering the luminal surface of ECs, called the glycocalyx. In a range of cardiovascular disorders, glycocalyx shedding causes endothelial dysfunction and inflammation, underscoring the importance of glycocalyx preservation to avoid disease initiation and progression. In this review we discuss the physiological functions of the glycocalyx with particular focus on how loss of endothelial glycocalyx integrity is linked to cardiovascular risk factors, like hypertension, aging, diabetes and obesity, and contributes to the development of thrombo-inflammatory conditions. Finally, we consider the role of glycocalyx components in regulating inflammatory responses and discuss possible therapeutic interventions aiming at preserving or restoring the endothelial glycocalyx and therefore protecting against cardiovascular disease.

Updated Pathways in Cardiorenal Continuum after Kidney Transplantation

Cardiovascular disease (CVD) remains one of the leading causes for increased morbidity and mortality in chronic kidney disease (CKD). Kidney transplantation is the preferred treatment option for CKD G5. Improved perioperative and postoperative care, personalized immunosuppressive regimes, and refined matching procedures of kidney transplants improves cardiovascular health in the early posttransplant period. However, the long-term burden of CVD is considerable. Previously underrecognized, the role of the complement system alongside innate immunity, inflammaging, structural changes in the glomerular filtration barrier and early vascular ageing also seem to play an important role in the posttransplant management. This review provides up-to-date knowledge on these pathways that may influence the cardiovascular and renal continuum and identifies potential targets for future therapies. Arterial destiffening strategies and the applicability of sodium-glucose cotransporter 2 inhibitors and their role in cardiovascular health after kidney transplantation are also addressed.

Platelet Versus Megakaryocyte: Who Is the Real Bandleader of Thromboinflammation in Sepsis?

Platelets are mainly known for their key role in hemostasis and thrombosis. However, studies over the last two decades have shown their strong implication in mechanisms associated with inflammation, thrombosis, and the immune system in various neoplastic, inflammatory, autoimmune, and infectious diseases. During sepsis, platelets amplify the recruitment and activation of innate immune cells at the site of infection and contribute to the elimination of pathogens. In certain conditions, these mechanisms can lead to thromboinflammation resulting in severe organ dysfunction. Here, we discuss the interactions of platelets with leukocytes, neutrophil extracellular traps (NETs), and endothelial cells during sepsis. The intrinsic properties of platelets that generate an inflammatory signal through the NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome are discussed. As an example of immunothrombosis, the implication of platelets in vaccine-induced immune thrombotic thrombocytopenia is documented. Finally, we discuss the role of megakaryocytes (MKs) in thromboinflammation and their adaptive responses.

Qinghao-Biejia Herb Pair Alleviates Pristane-Induced Lupus-Like Disease and Associated Renal and Aortic Lesions in ApoE−/− Mice

Backgroud: Systemic lupus erythematosus (SLE) is a chronic autoimmune disease involving multiple systems with a high prevalence of nephritis and atherosclerosis. Jieduquyuziyin prescription is a famous prescription with immune modulating and inflammation controlling effects, which is efficacious in the treatment of SLE. The most critical herbs in this prescription are Qinghao and Biejia. The aim of this study was to evaluate the therapeutic effect of Qinghao-Biejia herb hair (QB) on mice with SLE combined with atherosclerosis.

Materials and Methods: The effect of QB (identification using UPLC-TOF-MS) was assessed in female ApoE−/− mice intraperitoneally injected with 0.5 ml of pristane. Serum autoantibodies and lipid metabolic parameters were tested every 4 weeks, and spleen index, serum inflammatory biomarkers, renal injury, and aortic injury were observed after 16 weeks. The expression of signaling pathway in kidney tissues was observed by RT-qPCR and Western blot.

Results: The mice of QB-treated group exhibited a significant reduced serum autoantibodies level, urine protein, and renal immune complex deposition. QB treatment reduced the levels of inflammatory cytokines and improved the renal pathological changes. In addition, there was a reduction in aortic atheromatous plaque and some improvement in dyslipidemia. Moreover, QB suppressed the expression of HMGB1, TLR4, and MyD88 to some extent.

Conclusion: The present study implied that QB has clear efficacy for the treatment of SLE combined with atherosclerosis, and that inhibition of the HMGB1/TLR4 signaling pathway may be one of the therapeutic targets of QB for SLE combined with atherosclerosis.

Dexmedetomidine suppresses serum syndecan-1 elevation and improves survival in a rat hemorrhagic shock model

Hemorrhagic shock causes vascular endothelial glycocalyx (EGCX) damage and systemic inflammation. Dexmedetomidine (DEX) has anti-inflammatory and EGCX-protective effects, but its effect on hemorrhagic shock has not been investigated. Therefore, we investigated whether DEX reduces inflammation and protects EGCX during hemorrhagic shock. Anesthetized Sprague-Dawley rats were randomly assigned to five groups (n=7 per group): no shock (SHAM), hemorrhagic shock (HS), hemorrhagic shock with DEX (HS+DEX), hemorrhagic shock with DEX and the α7 nicotinic type acetylcholine receptor antagonist methyllycaconitine citrate (HS+DEX/MLA), and hemorrhagic shock with MLA (HS+MLA). HS was induced by shedding blood to a mean blood pressure of 25–30 mmHg, which was maintained for 30 min, after which rats were resuscitated with Ringer’s lactate solution at three times the bleeding volume. The survival rate was assessed up to 3 h after the start of fluid resuscitation. Serum tumor necrosis factor-alpha (TNF-α) and syndecan-1 concentrations, and wet-to-dry ratio of the heart were measured 90 min after the start of fluid resuscitation. The survival rate after 3 h was significantly higher in the HS+DEX group than in the HS group. Serum TNF-α and syndecan-1 concentrations, and the wet-to-dry ratio of heart were elevated by HS, but significantly decreased by DEX. These effects were antagonized by MLA. DEX suppressed the inflammatory response and serum syndecan-1 elevation, and prolonged survival in rats with HS.

Renal microvascular endothelial cell responses in sepsis-induced acute kidney injury

Microvascular endothelial cells in the kidney have been a neglected cell type in sepsis-induced acute kidney injury (sepsis-AKI) research; yet, they offer tremendous potential as pharmacological targets. As endothelial cells in distinct cortical microvascular segments are highly heterogeneous, this Review focuses on endothelial cells in their anatomical niche. In animal models of sepsis-AKI, reduced glomerular blood flow has been attributed to inhibition of endothelial nitric oxide synthase activation in arterioles and glomeruli, whereas decreased cortex peritubular capillary perfusion is associated with epithelial redox stress. Elevated systemic levels of vascular endothelial growth factor, reduced levels of circulating sphingosine 1-phosphate and loss of components of the glycocalyx from glomerular endothelial cells lead to increased microvascular permeability. Although coagulation disbalance occurs in all microvascular segments, the molecules involved differ between segments. Induction of the expression of adhesion molecules and leukocyte recruitment also occurs in a heterogeneous manner. Evidence of similar endothelial cell responses has been found in kidney and blood samples from patients with sepsis. Comprehensive studies are needed to investigate the relationships between segment-specific changes in the microvasculature and kidney function loss in sepsis-AKI. The application of omics technologies to kidney tissues from animals and patients will be key in identifying these relationships and in developing novel therapeutics for sepsis.

Extracellular HMGB1 Induced Glomerular Endothelial Cell Injury via TLR4/MyD88 Signaling Pathway in Lupus Nephritis

Previously, our study showed that HMGB1 was significantly elevated in the blood and located in the glomerular endothelium in LN patients. But whether extracellular HMGB1 is involved in the injury of glomerular endothelial cells (GECs) in LN still needs further investigation. Firstly, we detected the levels of SDC-1, VCAM-1, and proteinuria in LN patients and MRL/lpr mice and analyzed their correlations. Then, HMGB1 and TLR4/MyD88 were inhibited to observe the shedding of glycocalyx and injury of GECs in vivo and in vitro. Our results showed that HRGEC injury and SDC-1 shedding played an important role in the increase of permeability and proteinuria formation in LN. Additionally, inhibition of extracellular HMGB1 and/or downstream TLR4/MyD88/NF-κB/p65 signaling pathway also alleviated GEC monolayer permeability, reduced the shedding of the glomerular endothelial glycocalyx, improved the intercellular tight junction and cytoskeletal arrangement, and downregulated the NO level and VCAM-1 expression. These results suggested that extracellular HMGB1 might involve in GEC injury by activating the TLR4/MyD88 signaling pathway in LN, which provided novel insights and potential therapeutic target for the treatment of lupus nephritis.

Measuring the Concentration of Serum Syndecan-1 to Assess Vascular Endothelial Glycocalyx Injury During Hemodialysis

Glycocalyx is present on the surface of healthy endothelium, and the concentration of serum syndecan-1 can serve as an injury marker. This study aimed to assess endothelial injury using serum syndecan-1 as a marker of endothelial glycocalyx injury in patients who underwent hemodialysis. In this single-center, retrospective, observational study, 145 patients who underwent hemodialysis at the Gifu University Hospital between March 2017 and December 2019 were enrolled. The median dialysis period and time were 63 months and 3.7 h, respectively. The serum syndecan-1 concentration significantly increased from 124.6 ± 107.8 ng/ml before hemodialysis to 229.0 ± 138.1 ng/ml after hemodialysis (P &lt; 0.001). Treatment with anticoagulant nafamostat mesylate inhibited hemodialysis-induced increase in the levels of serum syndecan-1 in comparison to unfractionated heparin. Dialysis time and the change in the syndecan-1 concentration were positively correlated. Conversely, the amount of body fluid removed and the changes in the syndecan-1 concentration were not significantly correlated. The reduction in the amount of body fluid removed and dialysis time inhibited the change in the syndecan-1 levels before and after hemodialysis. In conclusion, quantitative assessment of the endothelial glycocalyx injury during hemodialysis can be performed by measuring the serum syndecan-1 concentration, which may aid in the selection of appropriate anticoagulants, reduction of hemodialysis time, and the amount of body fluid removed.

Serum syndecan-1 concentration in hospitalized patients with heart failure may predict readmission-free survival

Syndecan-1 is found in the endothelial glycocalyx and is released into the bloodstream during stressed conditions, including severe diseases such as acute kidney injury, chronic kidney disease, and cardiovascular disease. This study investigated the prognostic value of serum syndecan-1 concentration in patients with heart failure upon admission. Serum syndecan-1 concentration was analyzed in 152 patients who were hospitalized for worsening heart failure from September 2017 to June 2018. The primary outcome of the study was readmission-free survival, defined as the time from the first admission to readmission for worsened heart failure or death from any cause, which was assessed at 30 months after discharge from the hospital. The secondary outcome of the study was survival time. Blood samples and echocardiogram data were analyzed. Univariate and multivariable time-dependent Cox regression analyses adjusted for age, creatinine levels, and use of antibiotics were conducted. The serum syndecan-1 concentration was significantly associated with readmission-free survival. Subsequently, the syndecan-1 concentration may have gradually decreased with treatment. The administration of human atrial natriuretic peptide and antibiotics may have modified the relationship between readmission-free survival and serum syndecan-1 concentration (p = 0.01 and 0.008, respectively). Serum syndecan-1 concentrations, which may indicate injury to the endothelial glycocalyx, predict readmission-free survival in patients with heart failure.