A review on the physiological and pathophysiological role of endothelial glycocalyx

Focus of endothelial glycocalyx dysfunction in ischemic stroke and Alzheimer's disease: Possible intervention strategies

The integrity of the endothelial glycocalyx (eGCX), a mixture of carbohydrates attached to proteins expressed on the surface of blood vessel endothelial cells (EC), is critical for the maintenance of homeostasis of the cardiovascular system and all systems of the human body, the endothelium being the critical component of the stroma of all tissues. Consequently, dysfunction of eGCX results in a dysfunctional cardiovascular wall and severe downstream cardiovascular events, which contribute to the onset of cardio- and cerebrovascular diseases and neurodegenerative disorders, as well as other age-related diseases (ARDs). The key role of eGCX dysfunction in the onset of ARDs is examined here, with a focus on the most prevalent neurological diseases: ischemic stroke and Alzheimer's disease. Furthermore, the advantages and limitations of some treatment strategies for anti-eGCX dysfunction are described, ranging from experimental drug therapies, which need to be better tested and explored not only in animal models but also in humans, as well as reprogramming, the use of nutraceuticals, which are emerging as regenerative and new approaches. The promotion of these strategies is essential to keep eGCX and endothelium healthy, as is the development of intravital (e.g., intravascular) tools to estimate eGCX health status and treatment efficacy, which could lead to advanced solutions to address ARDs.

Role of endothelial glycocalyx in central nervous system diseases and evaluation of the targeted therapeutic strategies for its protection: a review of clinical and experimental data

Central nervous system (CNS) diseases, such as stroke, traumatic brain injury, dementia, and demyelinating diseases, are generally characterized by high morbidity and mortality, which impose a heavy economic burden on patients and their caregivers throughout their lives as well as on public health. The occurrence and development of CNS diseases are closely associated with a series of pathophysiological changes including inflammation, blood-brain barrier disruption, and abnormal coagulation. Endothelial glycocalyx (EG) plays a key role in these changes, making it a novel intervention target for CNS diseases. Herein, we review the current understanding of the role of EG in common CNS diseases, from the perspective of individual pathways/cytokines in pathophysiological and systematic processes. Furthermore, we emphasize the recent developments in therapeutic agents targeted toward protection or restoration of EG. Some of these treatments have yielded unexpected pharmacological results, as previously unknown mechanisms underlying the degradation and destruction of EG has been brought to light. Furthermore, the anti-inflammatory, anticoagulative, and antioxidation effects of EG and its protective role exerted via the blood-brain barrier have been recognized.

Down-regulating lncRNA KCNQ1OT1 relieves type II alveolar epithelial cell apoptosis during one-lung ventilation via modulating miR-129-5p/HMGB1 axis induced pulmonary endothelial glycocalyx

OBJECTIVE

Endothelial glycocalyx (EG) maintains vascular homeostasis and is destroyed after one-lung ventilation (OLV)-induced lung injury. Long noncoding RNAs (lncRNAs) are critically involved in various lung injuries. This study aimed to investigate the role and regulatory mechanism of KCNQ1 overlapping transcript 1 (KCNQ1OT1) in OLV-induced lung injury and LPS-induced type II alveolar epithelial cell (AECII) apoptosis.

METHODS

The rat OLV model was established, and the effects of KCNQ1OT1 on OLV-induced ALI in vivo were explored. Bax and Caspase-3 expression in rat lung tissues was measured by immunochemistry (IHC). AECIIs were isolated from rat lungs and treated with LPS or normal saline (control) for in vitro analysis. The expression of KCNQ1OT1, miR-129-5p, and HMGB1 was measured by quantitative real-time PCR (qRT-PCR) or Western blot (WB). Cell proliferation and apoptosis were examined by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di- phenytetrazoliumromide (MTT) and flow cytometry. The downstream targets of KCNQ1OT1 were predicted by bioinformatics, and the binding relationship between KCNQ1OT1 and miR-129-3p was verified by dual-luciferase reporter assays. The potential target of miR-129-5p was further explored on the Targetscan website and revealed to target HMGB1. Enzyme-linked immunosorbent assay (ELISA) or WB was adopted to determine the levels of IL-1β, TNF-α, MDA, SOD, heparanase (HPA), matrix metalloproteinase 9 (MMP9), heparan sulfate (HS) and syndecan-1 (SDC-1).

RESULTS

KCNQ1OT1 and HMGB1 were up-regulated during OLV-induced lung injury, and their expression was positively correlated. KCNQ1OT1 knockdown reduced OLV-induced pulmonary edema and lung epithelial cell apoptosis, increased vascular permeability, reduced IL-1β, TNF-α, MDA, and SOD levels and glycocalyx markers by targeting miR-129-5p or upregulating HMGB1. Overexpressing KCNQ1OT1 promoted cell apoptosis, reduced cell proliferation, aggravated inflammation and oxidative stress, and up-regulated HMGB1, HPA and MMP9 in LPS-treated AECIIs, while the HMGB1 silencing showed the opposite effects. MiR-129-5p mimics partially eliminated the KCNQ1OT1-induced effects, while recombinant HMGB1 restored the effects of miR-129-5p overexpression on AECIIs. Additionally, KCNQ1OT1 was demonstrated to promote the activation of the p38 MAPK/Akt/ERK signaling pathways in AECIIs via HMGB1.

CONCLUSION

KCNQ1OT1 knockdown alleviated AECII apoptosis and EG damage during OLV by targeting miR-129-5p/HMGB1 to inactivate the p38 MAPK/Akt/ERK signaling. The findings of our study might deepen our understanding of the molecular basis in OLV-induced lung injury and provide clues for the targeted disease management.

Destruction of vascular endothelial glycocalyx during formation of pre-metastatic niches

A special microenvironment called the "pre-metastatic niche" is thought to help primary tumor cells migrate to new tissues and invade them, in part because the normal barrier function of the vascular endothelium is compromised. While the primary tumor itself can promote the creation of such niches by secreting pro-metastatic factors, the underlying molecular mechanisms are still poorly understood. Here, we show that the injection of primary tumor-secreted pro-metastatic factors from B16F10 melanoma or 4T1 breast cancer cells into healthy mice can induce the destruction of the vascular endothelial glycocalyx, which is a polysaccharide coating on the vascular endothelial lumen that normally inhibits tumor cell passage into and out of the circulation. However, when human umbilical vein endothelial cultures were treated in vitro with these secreted pro-metastatic factors, no significant destruction of the glycocalyx was observed, implying that this destruction requires a complex in vivo microenvironment. The tissue section analysis revealed that secreted pro-metastatic factors could clearly upregulate macrophage-related molecules such as CD11b and tumor necrosis factor-α (TNF-α) in the heart, liver, spleen, lung, and kidney, which is associated with the upregulation and activation of heparanase. In addition, macrophage depletion significantly attenuated the degradation of the vascular endothelial glycocalyx induced by secreted pro-metastatic factors. This indicates that the secreted pro-metastatic factors that destroy the vascular endothelial glycocalyx rely primarily on macrophages. Our findings suggest that the formation of pre-metastatic niches involves degradation of the vascular endothelial glycocalyx, which may hence be a useful target for developing therapies to inhibit cancer metastasis.

ADAMTS5 Promotes Permeability of the Blood-Brain Barrier during Treponema pallidum Subspecies pallidum Invading the Central Nervous System

The pathogenesis of neurosyphilis remains unclear. A previous study found a noteworthy up-regulation of a disintegrin and metalloproteinase with thrombospondin type 1 motif 5 (ADAMTS5) gene in human brain microvascular endothelial cells cocultured with Treponema pallidum subspecies pallidum (Tp). To investigate the ADAMTS5 role in Tp invading the central nervous system (CNS), we conducted relevant experiments. Our study revealed that Tp caused an increase in human cortical microvascular endothelial cell/D3 (hCMEC/D3) barrier permeability and significantly enhanced ADAMTS5 expression. The heightened permeability of the hCMEC/D3 barrier was effectively mitigated by inhibiting ADAMTS5. During this process, Tp promoted interleukin-1β production, which, in turn, facilitated ADAMTS5 expression. Furthermore, Tp significantly reduced the glycocalyx on the surface of hCMEC/D3 cells, which was also ameliorated by inhibiting ADAMTS5. Additionally, ADAMTS5 and endothelial glycocalyx components notably increased in the cerebrospinal fluid of HIV-negative neurosyphilis patients. This research provided the first demonstration of the ADAMTS5 role in Tp invading the CNS and offered new insight into neurosyphilis pathogenesis.

Conformational changes in the Niemann-Pick type C1 protein NCR1 drive sterol translocation

The membrane protein Niemann-Pick type C1 (NPC1, named NCR1 in yeast) is central to sterol homeostasis in eukaryotes. Saccharomyces cerevisiae NCR1 is localized to the vacuolar membrane, where it is suggested to carry sterols across the protective glycocalyx and deposit them into the vacuolar membrane. However, documentation of a vacuolar glycocalyx in fungi is lacking, and the mechanism for sterol translocation has remained unclear. Here, we provide evidence supporting the presence of a glycocalyx in isolated S. cerevisiae vacuoles and report four cryo-EM structures of NCR1 in two distinct conformations, named tense and relaxed. These two conformations illustrate the movement of sterols through a tunnel formed by the luminal domains, thus bypassing the barrier presented by the glycocalyx. Based on these structures and on comparison with other members of the Resistance-Nodulation-Division (RND) superfamily, we propose a transport model that links changes in the luminal domains with a cycle of protonation and deprotonation within the transmembrane region of the protein. Our model suggests that NPC proteins work by a generalized RND mechanism where the proton motive force drives conformational changes in the transmembrane domains that are allosterically coupled to luminal/extracellular domains to promote sterol transport.

Saphenous vein to the right coronary system from the right thoracic artery or the aorta. Long-term propensity-matched results of 2 groups

OBJECTIVES

Since 2000, we anastomosed the saphenous vein graft to the right coronary artery system using the stump of the right internal thoracic artery as inflow. The long-term results of patients where the right coronary artery was grafted with the right internal thoracic artery or the ascending aorta as saphenous vein inflow has not been reported.

METHODS

From 2000 to 2018, 699 consecutive patients had right internal thoracic artery elongated with saphenous vein (I-graft group, n = 358, 51.2%) or saphenous vein from the aorta (Ao-graft group, n = 341, 48.8%) on right coronary artery system. Inclusion criteria were age ≤75 years, bilateral internal thoracic arteries as a Y graft on the left system (three-vessel disease, n = 603, 86.3%) or as a left internal thoracic artery on left anterior descending and right internal thoracic artery elongated with saphenous vein on the right coronary artery system (two-vessel disease, n = 96, 13.7%), only 1 saphenous vein per patient. Propensity-matching identified 272 patients per group. One-hundred and twenty-two patients underwent coronary computed tomographic angiography to asses grafts patency after a median follow-up of 88 (65-93) months.

RESULTS

In the paired samples, there was no difference in the early outcome. Ten-year survival and freedom from death, non-fatal acute myocardial infarction and repeat revascularization were higher in I-graft group: 90.6 [standard error (SE): 2.0] vs 78.2 (SE: 5.3), P = 0.0266, and 85.2 (SE: 2.4) vs 69.9 (SE: 5.3), P = 0.0179. Saphenous vein graft, at a long-time follow-up, showed a higher patency rate (81.6% (SE: 7.0) vs 50.7% (SE: 7.9), P < 0.0001) and a smaller internal lumen diameter (2.7, standard deviation: 0.4 vs 3.4, standard deviation: 0.6 mm, P < 0.0001) when right internal thoracic artery was the inflow.

CONCLUSIONS

Grafting the right coronary artery with saphenous vein may entail higher patency rate and better outcome when the inflow is the right internal thoracic artery than when is the ascending aorta. Prospective randomized data are needed to test this hypothesis.

The impact of vascular endothelial glycocalyx on the pathogenesis and treatment of disseminated intravascular coagulation

Disseminated intravascular coagulation (DIC) is a complex disorder characterized by widespread activation of blood clotting mechanisms throughout the body. Understanding the role of vascular endothelial glycocalyx in the pathogenesis and treatment of DIC is crucial for advancing our knowledge in this field. The vascular endothelial glycocalyx is a gel-like layer that coats the inner surface of blood vessels. It plays a significant role in maintaining vascular integrity, regulating fluid balance, and preventing excessive clotting. In the pathogenesis of DIC, the disruption of the vascular endothelial glycocalyx is a key factor. Pathological conditions trigger the activation of enzymes, including heparanase, hyaluronase, and matrix metalloproteinase. This activation leads to glycocalyx degradation, subsequently exposing endothelial cells to procoagulant stimuli. Additionally, the ANGPTs/Tie-2 signaling pathway plays a role in the imbalance between the synthesis and degradation of VEG, exacerbating endothelial dysfunction and DIC. Understanding the mechanisms behind glycocalyx degradation and its impact on DIC can provide valuable insights for the development of targeted therapies. Preservation of the glycocalyx integrity may help prevent the initiation and propagation of DIC. Strategies such as administration of exogenous glycocalyx components, anticoagulant agents, or Tie-2 antibody agents have shown promising results in experimental models. In conclusion, the vascular endothelial glycocalyx plays a crucial role in the pathogenesis and treatment of DIC. Further research in this field is warranted to unravel the complex interactions between the glycocalyx and DIC, ultimately leading to the development of novel therapies.

Changes in the levels of free sialic acid during ex vivo lung perfusion do not correlate with pulmonary function. Experimental model

BACKGROUND

Ex vivo lung perfusion (EVLP) constitutes a tool with great research potential due to its advantages over in vivo and in vitro models. Despite its important contribution to lung reconditioning, this technique has the disadvantage of incurring high costs and can induce pulmonary endothelial injury through perfusion and ventilation. The pulmonary endothelium is made up of endothelial glycocalyx (EG), a coating of proteoglycans (PG) on the luminal surface. PGs are glycoproteins linked to terminal sialic acids (Sia) that can affect homeostasis with responses leading to edema formation. This study evaluated the effect of two ex vivo perfusion solutions on lung function and endothelial injury.

METHODS

We divided ten landrace swine into two groups and subjected them to EVLP for 120 min: Group I (n = 5) was perfused with Steen® solution, and Group II (n = 5) was perfused with low-potassium dextran-albumin solution. Ventilatory mechanics, histology, gravimetry, and sialic acid concentrations were evaluated.

RESULTS

Both groups showed changes in pulmonary vascular resistance and ventilatory mechanics (p < 0.05, Student's t-test). In addition, the lung injury severity score was better in Group I than in Group II (p < 0.05, Mann-Whitney U); and both groups exhibited a significant increase in Sia concentrations in the perfusate (p < 0.05 t-Student) and Sia immunohistochemical expression.

CONCLUSIONS

Sia, as a product of EG disruption during EVLP, was found in all samples obtained in the system; however, the changes in its concentration showed no apparent correlation with lung function.

Modulation of lncRNA links endothelial glycocalyx to vascular dysfunction of tyrosine kinase inhibitor

AIMS

Novel cancer therapies leading to increased survivorship of cancer patients have been negated by a concomitant rise in cancer therapies-related cardiovascular toxicities. Sunitinib, a first line multi-receptor tyrosine kinase inhibitor, has been reported to cause vascular dysfunction although the initiating mechanisms contributing to this side effect remain unknown. Long non-coding RNAs (lncRNAs) are emerging regulators of biological processes in endothelial cells (ECs); however, their roles in cancer therapies-related vascular toxicities remain underexplored.

METHODS AND RESULTS

We performed lncRNA expression profiling to identify potential lncRNAs that are dysregulated in human-induced pluripotent stem cell-derived ECs (iPSC-ECs) treated with sunitinib. We show that the lncRNA hyaluronan synthase 2 antisense 1 (HAS2-AS1) is significantly diminished in sunitinib-treated iPSC-ECs. Sunitinib was found to down-regulate HAS2-AS1 by an epigenetic mechanism involving hypermethylation. Depletion of HAS2-AS1 recapitulated sunitinib-induced detrimental effects on iPSC-ECs, whereas CRISPR-mediated activation of HAS2-AS1 reversed sunitinib-induced dysfunction. We confirmed that HAS2-AS1 stabilizes the expression of its sense gene HAS2 via an RNA/mRNA heteroduplex formation. Knockdown of HAS2-AS1 led to reduced synthesis of hyaluronic acid (HA) and up-regulation of ADAMTS5, an enzyme involved in extracellular matrix degradation, resulting in disruption of the endothelial glycocalyx which is critical for ECs. In vivo, sunitinib-treated mice showed reduced coronary flow reserve, accompanied by a reduction in Has2os and degradation of the endothelial glycocalyx. Finally, we identified that treatment with high molecular-weight HA can prevent the deleterious effects of sunitinib both in vitro and in vivo by preserving the endothelial glycocalyx.

CONCLUSIONS

Our findings highlight the importance of lncRNA-mediated regulation of the endothelial glycocalyx as an important determinant of sunitinib-induced vascular toxicity and reveal potential novel therapeutic avenues to attenuate sunitinib-induced vascular dysfunction.

Syndecan-4 is the key proteoglycan involved in mediating sepsis-associated lung injury

Vascular endothelial cell dysfunction involving syndecan (SDC) proteoglycans contributes to acute sepsis-associated lung injury (ALI), but the exact SDC isoform involved is unclear. We aimed to clarify which SDCs are involved in ALI. A relevant gene expression dataset (GSE5883) was analysed for differentially expressed genes (DEGs) between lipopolysaccharide (LPS)-treated and control lung endothelial cells and for SDC isoform expression. Bioinformatic analyses to predict DEG function were conducted using R language, Gene Ontology, and the Kyoto Encyclopedia of Genes and Genomes. SDC2 and SDC4 expression profiles were examined under inflammatory conditions in human lung vascular endothelial cell and mouse sepsis-associated ALI models. Transcription factors regulating SDC2/4 were predicted to indirectly assess SDC involvement in septic inflammation. Of the DEGs, 224 and 102 genes were up- and downregulated, respectively. Functional analysis indicated that DEGs were involved in modulating receptor ligand and signalling receptor activator activities, cytokine receptor binding, responses to LPS and molecules of bacterial origin, regulation of cell adhesion, tumour necrosis factor signalling, and other functions. DEGs were also enriched for cytoplasmic ribonucleoprotein granules, transcription regulator complexes, and membrane raft cellular components. SDC4 gene expression was 4.5-fold higher in the LPS group than in the control group, while SDC2 levels were similar in both groups. SDC4 mRNA and protein expression was markedly upregulated in response to inflammatory injury, and SDC4 downregulation severely exacerbated inflammatory responses in both in vivo and in vitro models. Overall, our data demonstrate that SDC4, rather than SDC2, is involved in LPS-induced sepsis-associated ALI.

Endothelial glycocalyx injury is involved in heatstroke-associated coagulopathy and protected by N-acetylcysteine

Introduction

Damage to endothelial glycocalyx (EGCX) can lead to coagulation disorders in sepsis. Heat stroke (HS) resembles sepsis in many aspects; however, it is unclear whether EGCX injury is involved in its pathophysiology. The purpose of this study was to examine the relationship between the damage of EGCX and the development of coagulation disorders during HS.

Methods

We retrospectively collected 159 HS patients and analyzed coagulation characteristics and prognosis of HS patients with or without disseminated intravascular coagulation (DIC). We also replicated a rat HS model and measured coagulation indexes, pulmonary capillary EGCX injury in HS rats. Finally, we evaluated the effect of the antioxidant N-acetylcysteine (NAC) on HS-initiated EGCX injury and coagulation disorders.

Results

Clinical data showed that HS patients complicated with DIC had a higher risk of death than HS patients without DIC. In a rat HS model, we found that rats subjected to heat stress developed hypercoagulability and platelet activation at the core body temperature of 43°C, just before the onset of HS. At 24 h of HS, the rats showed a consumptive hypo-coagulation state. The pulmonary capillary EGCX started to shed at 0 h of HS and became more severe at 24 h of HS. Importantly, pretreatment with NAC substantially alleviated EGCX damage and reversed the hypo-coagulation state in HS rats. Mechanically, HS initiated reactive oxidative species (ROS) generation, while ROS could directly cause EGCX damage. Critically, NAC protected against EGCX injury by attenuating ROS production in heat-stressed or hydrogen peroxide (H2O2)-stimulated endothelial cells.

Discussion

Our results indicate that the poor prognosis of HS patients correlates with severe coagulation disorders, coagulation abnormalities in HS rats are associated with the damage of EGCX, and NAC improves HS-induced coagulopathy, probably through its protection against EGCX injury by preventing ROS generation.

Applications and continued evolution of glycan imaging mass spectrometry

Glycosylation is an important posttranslational modifier of proteins and lipid conjugates critical for the stability and function of these macromolecules. Particularly important are N-linked glycans attached to asparagine residues in proteins. N-glycans have well-defined roles in protein folding, cellular trafficking and signal transduction, and alterations to them are implicated in a variety of diseases. However, the non-template driven biosynthesis of these N-glycans leads to significant structural diversity, making it challenging to identify the most biologically and clinically relevant species using conventional analyses. Advances in mass spectrometry instrumentation and data acquisition, as well as in enzymatic and chemical sample preparation strategies, have positioned mass spectrometry approaches as powerful analytical tools for the characterization of glycosylation in health and disease. Imaging mass spectrometry expands upon these strategies by capturing the spatial component of a glycan's distribution in-situ, lending additional insight into the organization and function of these molecules. Herein we review the ongoing evolution of glycan imaging mass spectrometry beginning with widely adopted tissue imaging approaches and expanding to other matrices and sample types with potential research and clinical implications. Adaptations of these techniques, along with their applications to various states of disease, are discussed. Collectively, glycan imaging mass spectrometry analyses broaden our understanding of the biological and clinical relevance of N-glycosylation to human disease.

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.

Vaccine-induced immune thrombosis and thrombocytopenia syndrome following adenovirus-vectored severe acute respiratory syndrome coronavirus 2 vaccination: a novel hypothesis regarding mechanisms and implications for future vaccine development

We hypothesize that thrombosis with thrombocytopenia syndrome recently described after administration of adenovirus‐vectored vaccines for severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) occurs as a result of the unique properties of the adenovirus vectors, which can have widespread biodistribution throughout the body. The antigen is delivered to megakaryocyte cells, which act as part of the primary immune system and distribute the antigen within progeny platelets, also a key component of the immune system. The interaction of the antigen induces preformed antiplatelet factor 4 (PF4) antibodies to bind to PF4–heparan sulfate complexes in the absence of exogenous heparin, at sites where the heparan sulfate concentration in the vascular glycocalyx is optimal for complex formation, causing thrombosis and thrombocytopenia as observed clinically. This hypothesis is testable in cell culture and animal models, and potentially in vivo, and if proven correct has significant implications for vaccine development and our understanding of the links between the coagulation and immune systems.

How to Improve the Biocompatibility of Peritoneal Dialysis Solutions (without Jeopardizing the Patient's Health)

Peritoneal dialysis (PD) is an important, if underprescribed, modality for the treatment of patients with end-stage kidney disease. Among the barriers to its wider use are the deleterious effects of currently commercially available glucose-based PD solutions on the morphological integrity and function of the peritoneal membrane due to fibrosis. This is primarily driven by hyperglycaemia due to its effects, through multiple cytokine and transcription factor signalling-and their metabolic sequelae-on the synthesis of collagen and other extracellular membrane components. In this review, we outline these interactions and explore how novel PD solution formulations are aimed at utilizing this knowledge to minimise the complications associated with fibrosis, while maintaining adequate rates of ultrafiltration across the peritoneal membrane and preservation of patient urinary volumes. We discuss the development of a new generation of reduced-glucose PD solutions that employ a variety of osmotically active constituents and highlight the biochemical rationale underlying optimization of oxidative metabolism within the peritoneal membrane. They are aimed at achieving optimal clinical outcomes and improving the whole-body metabolic profile of patients, particularly those who are glucose-intolerant, insulin-resistant, or diabetic, and for whom daily exposure to high doses of glucose is contraindicated.

Change of Hemoglobin Levels in the Early Post-cardiac Arrest Phase Is Associated With Outcome

Background: The post-cardiac arrest (CA) phase is characterized by high fluid requirements, endothelial activation and increased vascular permeability. Erythrocytes are large cells and may not leave circulation despite massive capillary leak. We hypothesized that dynamic changes in hemoglobin concentrations may reflect the degree of vascular permeability and may be associated with neurologic function after CA.

Methods: We included patients ≥18 years, who suffered a non-traumatic CA between 2013 and 2018 from the prospective Vienna Clinical Cardiac Arrest Registry. Patients without return of spontaneous circulation (ROSC), with extracorporeal life support, with any form of bleeding, undergoing surgery, receiving transfusions, without targeted temperature management or with incomplete datasets for multivariable analysis were excluded. The primary outcome was neurologic function at day 30 assessed by the Cerebral Performance Category scale. Differences of hemoglobin concentrations at admission and 12 h after ROSC were calculated and associations with neurologic function were investigated by uni- and multivariable logistic regression.

Results: Two hundred and seventy-five patients were eligible for analysis of which 143 (52%) had poor neurologic function. For every g/dl increase in hemoglobin from admission to 12 h the odds of poor neurologic function increased by 26% (crude OR 1.26, 1.07–1.49, p = 0.006). The effect remained unchanged after adjustment for fluid balance and traditional prognostication markers (adjusted OR 1.27, 1.05–1.54, p = 0.014).

Conclusion: Increasing hemoglobin levels in spite of a positive fluid balance may serve as a surrogate parameter of vascular permeability and are associated with poor neurologic function in the early post-cardiac arrest period.

Low-GDP, pH-neutral solutions preserve peritoneal endothelial glycocalyx during long-term peritoneal dialysis

BACKGROUND

During peritoneal dialysis (PD), solute transport and ultrafiltration are mainly achieved by the peritoneal blood vasculature. Glycocalyx lies on the surface of endothelial cells and plays a role in vascular permeability. Low-glucose degradation product (GDP), pH-neutral PD solutions reportedly offer higher biocompatibility and lead to less peritoneal injury. However, the effects on the vasculature have not been clarified.

METHODS

Peritoneal tissues from 11 patients treated with conventional acidic solutions (acidic group) and 11 patients treated with low-GDP, pH-neutral solutions (neutral group) were examined. Control tissues were acquired from 5 healthy donors of kidney transplants (control group). CD31 and ratio of luminal diameter to vessel diameter (L/V ratio) were evaluated to identify endothelial cells and vasculopathy, respectively. Immunostaining for heparan sulfate (HS) domains and Ulex europaeus agglutinin-1 (UEA-1) binding was performed to assess sulfated glycosaminoglycans and the fucose-containing sugar chain of glycocalyx.

RESULTS

Compared with the acidic group, the neutral group showed higher CD31 positivity. L/V ratio was significantly higher in the neutral group, suggesting less progression of vasculopathy. Both HS expression and UEA-1 binding were higher in the neutral group, whereas HS expression was markedly more preserved than UEA-1 binding in the acidic group. In vessels with low L/V ratio, which were found only in the acidic group, HS expression and UEA-1 binding were diminished, suggesting a loss of glycocalyx.

CONCLUSION

Peritoneal endothelial glycocalyx was more preserved in patients treated with low-GDP, pH-neutral solution. The use of low-GDP, pH-neutral solutions could help to protect peritoneal vascular structures and functions.

Studying the Endothelial Glycocalyx in vitro: What Is Missing?

All human cells are coated by a surface layer of proteoglycans, glycosaminoglycans (GAGs) and plasma proteins, called the glycocalyx. The glycocalyx transmits shear stress to the cytoskeleton of endothelial cells, maintains a selective permeability barrier, and modulates adhesion of blood leukocytes and platelets. Major components of the glycocalyx, including syndecans, heparan sulfate, and hyaluronan, are shed from the endothelial surface layer during conditions including ischaemia and hypoxia, sepsis, atherosclerosis, diabetes, renal disease, and some viral infections. Studying mechanisms of glycocalyx damage in vivo can be challenging due to the complexity of immuno-inflammatory responses which are inextricably involved. Previously, both static as well as perfused in vitro models have studied the glycocalyx, and have reported either imaging data, assessment of barrier function, or interactions of blood components with the endothelial monolayer. To date, no model has simultaneously incorporated all these features at once, however such a model would arguably enhance the study of vasculopathic processes. This review compiles a series of current in vitro models described in the literature that have targeted the glycocalyx layer, their limitations, and potential opportunities for further developments in this field.

Vascular smooth muscle remodeling in health and disease

In blood vessels, vascular smooth muscle cells (VSMCs) generally exist in two major phenotypes: contractile and non-contractile (synthetic). The contractile phenotype is predominant and includes quiescent or differentiated VSMCs, which function as the regulators of blood vessel diameter and blood flow. According to some literature in the field, contractile VSMCs do not switch to the non-contractile phenotype due to the activation of specific transcription factors that are considered as guardians of the contractile phenotype. However, a vast amount of the literature uses the terms remodeling and phenotype switching of contractile VSMCs interchangeably based mainly on studies dealing with atherosclerosis. The use of the terms remodeling and switching to describe changes in phenotype based on morphological criteria can be confusing. The term remodeling was first used to describe morphological changes in the heart and was soon used to describe phenotype changes of contractile VSMCs based on morphological criteria. The latter were introduced in early studies, and new molecular criteria were later added, including changes in gene expression, which could be irreversible. In this review, we will discuss the different views concerning remodeling and possible switching of contractile VSMCs to a non-contractile phenotype. We conclude that only remodeling of contractile VSMCs may take place upon vascular injury and disease.