Short-term hyperglycemia increases endothelial glycocalyx permeability and acutely decreases lineal density of capillaries with flowing red blood cells

Low molecular weight fucoidan restores diabetic endothelial glycocalyx by targeting neuraminidase2: A new therapy target in glycocalyx shedding

BACKGROUND AND PURPOSE

Diabetic vascular complication is a leading cause of disability and mortality in diabetes patients. Low molecular weight fucoidan (LMWF) is a promising drug candidate for vascular complications. Glycocalyx injury predates the occurrence of diabetes vascular complications. Protecting glycocalyx from degradation relieves diabetic vascular complications. LMWF has the potential to protect the diabetes endothelial glycocalyx from shedding.

EXPERIMENTAL APPROACH

The protective effect of LMWF on diabetic glycocalyx damage was investigated in db/db mice and Human Umbilical Vein Endothelial Cells (HUVEC) through transmission electron microscopy and WGA labelling. The effect of LMWF on glycocalyx degrading enzymes expression was investigated. Neuraminidase2 (NEU2) overexpression/knockdown was performed in HUVECs to verify the important role of NEU2 in glycocalyx homeostasis. The interaction between NEU2 and LMWF was detected by ELISA and surface plasmon resonance analysis (SPR).

KEY RESULTS

LMWF normalizes blood indexes including insulin, triglyceride, uric acid and reduces diabetes complications adverse events. LMWF alleviates diabetic endothelial glycocalyx damage in db/db mice kidney/aorta and high concentration glucose treated HUVECs. NEU2 is up-regulated in db/db mice and HUVECs with high concentration glucose. Overexpression/knockdown NEU2 results in glycocalyx shedding in HUVEC. Down-regulation and interaction of LMWF with NEU2 is a new therapy target in glycocalyx homeostasis. NEU2 was positively correlated with phosphorylated IR-β.

CONCLUSION AND IMPLICATIONS

NEU2 is an effective target for glycocalyx homeostasis and LMWF is a promising drug to alleviate vascular complications in diabetes by protecting endothelial glycocalyx.

Syndecans and diabetic complications: A narrative review

Syndecan (SDC) is a member of the heparan sulfate proteoglycan (HSPG) family. It appears to play a role in the aetiology of diabetic complications, with decreased levels of SDCs being reported in the kidney, retina, and cardiac muscle in models of diabetes mellitus (DM). The reduced levels of SDCs may play an important role in the development of albuminuria in DM. Some studies have provided the evidence supporting the mechanisms underlying the role of SDCs in DM. However, SDCs and the molecular mechanisms involved are complex and need to be further elucidated. This review focuses on the underlying molecular mechanisms of SDCs that are involved in the development and progression of the complications of DM, which may help in developing new strategies to prevent and treat these complications.

Variations in metabolic enzymes cause differential changes of heparan sulfate and hyaluronan in high glucose treated cells on chip

Glycocalyx dysfunction is believed as the first step in diabetic vascular disease. However, few studies have systematically investigated the influence of HG on the glycocalyx as a whole and its major constituent glycans towards one type of cell. Furthermore, most studies utilized traditional two-dimensional (2D) cultures in vitro, which can't provide the necessary fluid environment for glycocalyx. Here, we utilized vascular glycocalyx on chips to evaluate the changes of glycocalyx and its constituent glycans in HG induced HUVECs. Fluorescence microscopy showed up-regulation of hyaluronan (HA) but down-regulation of heparan sulfate (HS). By analyzing the metabolic enzymes of both glycans, a decrease in the ratio of synthetic/degradative enzymes for HA and an increase in that for HS were demonstrated. Two substrates (UDP-GlcNAc, UDP-GlcA) for the synthesis of both glycans were increased according to omics analysis. Since they were firstly pumped into Golgi apparatus to synthesize HS, less substrates may be left for HA synthesis. Furthermore, the differential changes of HA and HS were confirmed in vessel slides from db/db mice. This study would deepen our understanding of impact of HG on glycocalyx formation and diabetic vascular disease.

Edema and lymphatic clearance: molecular mechanisms and ongoing challenges

Resolution of edema remains a significant clinical challenge. Conditions such as traumatic shock, sepsis, or diabetes often involve microvascular hyperpermeability, which leads to tissue and organ dysfunction. Lymphatic insufficiency due to genetic causes, surgical removal of lymph nodes, or infections, leads to varying degrees of tissue swelling that impair mobility and immune defenses. Treatment options are limited to management of edema as there are no specific therapeutics that have demonstrated significant success for ameliorating microvascular leakage or impaired lymphatic function. This review examines current knowledge about the physiological, cellular, and molecular mechanisms that control microvascular permeability and lymphatic clearance, the respective processes for interstitial fluid formation and removal. Clinical conditions featuring edema, along with potential future directions are discussed.

Influence of the vessel wall geometry on the wall-induced migration of red blood cells

The geometry of the blood vessel wall plays a regulatory role on the motion of red blood cells (RBCs). The overall topography of the vessel wall depends on many features, among which the endothelial lining of the endothelial surface layer (ESL) is an important one. The endothelial lining of vessel walls presents a large surface area for exchanging materials between blood and tissues. The ESL plays a critical role in regulating vascular permeability, hindering leukocyte adhesion as well as inhibiting coagulation during inflammation. Changes in the ESL structure are believed to cause vascular hyperpermeability and entrap immune cells during sepsis, which could significantly alter the vessel wall geometry and disturb interactions between RBCs and the vessel wall, including the wall-induced migration of RBCs and the thickening of a cell-free layer. To investigate the influence of the vessel wall geometry particularly changed by the ESL under various pathological conditions, such as sepsis, on the motion of RBCs, we developed two models to represent the ESL using the immersed boundary method in two dimensions. In particular, we used simulations to study how the lift force and drag force on a RBC near the vessel wall vary with different wall thickness, spatial variation, and permeability associated with changes in the vessel wall geometry. We find that the spatial variation of the wall has a significant effect on the wall-induced migration of the RBC for a high permeability, and that the wall-induced migration is significantly inhibited as the vessel diameter is increased.

Early diabetic kidney disease: Focus on the glycocalyx

The incidence of diabetic kidney disease (DKD) is sharply increasing worldwide. Microalbuminuria is the primary clinical marker used to identify DKD, and its initiating step in diabetes is glomerular endothelial cell dysfunction, particularly glycocalyx impairment. The glycocalyx found on the surface of glomerular endothelial cells, is a dynamic hydrated layer structure composed of pro-teoglycans, glycoproteins, and some adsorbed soluble components. It reinforces the negative charge barrier, transduces the shear stress, and mediates the interaction of blood corpuscles and podocytes with endothelial cells. In the high-glucose environment of diabetes, excessive reactive oxygen species and proinflammatory cytokines can damage the endothelial glycocalyx (EG) both directly and indirectly, which induces the production of microalbuminuria. Further research is required to elucidate the role of the podocyte glycocalyx, which may, together with endothelial cells, form a line of defense against albumin filtration. Interestingly, recent research has confirmed that the negative charge barrier function of the glycocalyx found in the glomerular basement membrane and its repulsion effect on albumin is limited. Therefore, to improve the early diagnosis and treatment of DKD, the potential mechanisms of EG degradation must be analyzed and more responsive and controllable targets must be explored. The content of this review will provide insights for future research.

Endothelial Dysfunction in Patients Undergoing Cardiac Surgery: A Narrative Review and Clinical Implications

Cardiac surgery is one of the highest-risk procedures, usually involving cardiopulmonary bypass and commonly inducing endothelial injury that contributes to the development of perioperative and postoperative organ dysfunction. Substantial scientific efforts are being made to unravel the complex interaction of biomolecules involved in endothelial dysfunction to find new therapeutic targets and biomarkers and to develop therapeutic strategies to protect and restore the endothelium. This review highlights the current state-of-the-art knowledge on the structure and function of the endothelial glycocalyx and mechanisms of endothelial glycocalyx shedding in cardiac surgery. Particular emphasis is placed on potential strategies to protect and restore the endothelial glycocalyx in cardiac surgery. In addition, we have summarized and elaborated the latest evidence on conventional and potential biomarkers of endothelial dysfunction to provide a comprehensive synthesis of crucial mechanisms of endothelial dysfunction in patients undergoing cardiac surgery, and to highlight their clinical implications.

Microgravity and Lymphatics: Why Space Programs Need Lymphedema Physiology Specialists

Background: The resurgence of space travel in the recent years, both through formally trained astronauts on the International Space Station and the civilian space race to send astrocivilians to Low Earth Orbit and beyond, beckons the need to understand the role of the lymphatic system and role of endothelial glycocalyx when subjected to gravitational alterations. Methods and Results: A comprehensive narrative review of the literature explores a call to action for research and countermeasure development to support the health and well-being of humans subjected to space flight, with particular attention to the role of the lymphatic system and endothelial glycocalyx. Emerging evidence suggests a link between the dysfunction experienced with various physiological processes in microgravity, highlighting the need for more research exploring the role of the lymphatic system in the extremes of gravity and countermeasure development to reduce dysregulation. Conclusion: The synergistic and interdependent relationship of these structures are fundamental to health in space and on Earth.

Developing a transwell millifluidic device for studying blood-brain barrier endothelium

Blood-brain barrier (BBB) endothelial cell (EC) function depends on flow conditions and on supportive cells, like pericytes and astrocytes, which have been shown to be both beneficial and detrimental for brain EC function. Most studies investigating BBB EC function lack physiological relevance, using sub-physiological shear stress magnitudes and/or omitting pericytes and astrocytes. In this study, we developed a millifluidic device compatible with standard transwell inserts to investigate BBB function. In contrast to standard polydimethylsiloxane (PDMS) microfluidic devices, this model allows for easy, reproducible shear stress exposure without common limitations of PDMS devices such as inadequate nutrient diffusion and air bubble formation. In no-flow conditions, we first used the device to examine the impact of primary human pericytes and astrocytes on human brain microvascular EC (HBMEC) barrier integrity. Astrocytes, pericytes, and a 1-to-1 ratio of both cell types increased HBMEC barrier integrity via reduced 3 and 40 kDa fluorescent dextran permeability and increased claudin-5 expression. There were differing levels of low 3 kDa permeability in HBMEC-pericyte, HBMEC-astrocyte, and HBMEC-astrocyte-pericyte co-cultures, while levels of low 40 kDa permeability were consistent across co-cultures. The 3 kDa findings suggest that pericytes provide more barrier support to the BBB model compared to astrocytes, although both supportive cell types are permeability reducers. Incorporation of 24-hour 12 dynes per cm² flow significantly reduced dextran permeability in HBMEC monolayers, but not in the tri-culture model. These results indicate that tri-culture may exert more pronounced impact on overall BBB permeability than flow exposure. In both cases, monolayer and tri-culture, flow exposure interestingly reduced HBMEC expression of both claudin-5 and occludin. ZO-1 expression, and localization at cell-cell junctions increased in the tri-culture but exhibited no apparent change in the HBMEC monolayer. Under flow conditions, we also observed HBMEC alignment in the tri-culture but not in HBMEC monolayers, indicating supportive cells and flow are both essential to observe brain EC alignment in vitro. Collectively, these results support the necessity of physiologically relevant, multicellular BBB models when investigating BBB EC function. Consideration of the roles of shear stress and supportive cells within the BBB is critical for elucidating the physiology of the neurovascular unit.

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

The glycocalyx is a polysaccharide structure that protrudes from the body of a cell. It is primarily conformed of glycoproteins and proteoglycans, which provide communication, electrostatic charge, ionic buffering, permeability, and mechanosensation-mechanotransduction capabilities to cells. In blood vessels, the endothelial glycocalyx that projects into the vascular lumen separates the vascular wall from the circulating blood. Such a physical location allows a number of its components, including sialic acid, glypican-1, heparan sulfate, and hyaluronan, to participate in the mechanosensation-mechanotransduction of blood flow-dependent shear stress, which results in the synthesis of nitric oxide and flow-mediated vasodilation. The endothelial glycocalyx also participates in the regulation of vascular permeability and the modulation of inflammatory responses, including the processes of leukocyte rolling and extravasation. Its structural architecture and negative charge work to prevent macromolecules greater than approximately 70 kDa and cationic molecules from binding and flowing out of the vasculature. This also prevents the extravasation of pathogens such as bacteria and virus, as well as that of tumor cells. Due to its constant exposure to shear and circulating enzymes such as neuraminidase, heparanase, hyaluronidase, and matrix metalloproteinases, the endothelial glycocalyx is in a continuous process of degradation and renovation. A balance favoring degradation is associated with a variety of pathologies including atherosclerosis, hypertension, vascular aging, metastatic cancer, and diabetic vasculopathies. Consequently, ongoing research efforts are focused on deciphering the mechanisms that promote glycocalyx degradation or limit its syntheses, as well as on therapeutic approaches to improve glycocalyx integrity with the goal of reducing vascular disease. © 2022 American Physiological Society. Compr Physiol 12: 1-31, 2022.

Amelioration of endothelial dysfunction by sodium glucose co-transporter 2 inhibitors: pieces of the puzzle explaining their cardiovascular protection

Sodium glucose co‐transporter 2 inhibitors (SGLT‐2is) improve cardiovascular outcomes in both diabetic and non‐diabetic patients. Preclinical studies suggest that SGLT‐2is directly affect endothelial function in a glucose‐independent manner. The effects of SGLT‐2is include decreased oxidative stress and inflammatory reactions in endothelial cells. Furthermore, SGLT2is restore endothelium‐related vasodilation and regulate angiogenesis. The favourable cardiovascular effects of SGLT‐2is could be mediated via a number of pathways: (1) inhibition of the overactive sodium‐hydrogen exchanger; (2) decreased expression of nicotinamide adenine dinucleotide phosphate oxidases; (3) alleviation of mitochondrial injury; (4) suppression of inflammation‐related signalling pathways (e.g., by affecting NF‐κB); (5) modulation of glycolysis; and (6) recovery of impaired NO bioavailability. This review focuses on the most recent progress and existing gaps in preclinical investigations concerning the direct effects of SGLT‐2is on endothelial dysfunction and the mechanisms underlying such effects.

A few upstream bifurcations drive the spatial distribution of red blood cells in model microfluidic networks

The physics of blood flow in small vessel networks is dominated by the interactions between Red Blood Cells (RBCs), plasma and blood vessel walls. The resulting couplings between the microvessel network architecture and the heterogeneous distribution of RBCs at network-scale are still poorly understood. The main goal of this paper is to elucidate how a local effect, such as RBC partitioning at individual bifurcations, interacts with the global structure of the flow field to induce specific preferential locations of RBCs in model microfluidic networks. First, using experimental results, we demonstrate that persistent perturbations to the established hematocrit profile after diverging bifurcations may bias RBC partitioning at the next bifurcations. By performing a sensitivity analysis based upon network models of RBC flow, we show that these perturbations may propagate from bifurcation to bifurcation, leading to an outsized impact of a few crucial upstream bifurcations on the distribution of RBCs at network-scale. Based on measured hematocrit profiles, we further construct a modified RBC partitioning model that accounts for the incomplete relaxation of RBCs at these bifurcations. This model allows us to explain how the flow field results in a single pattern of RBC preferential location in some networks, while it leads to the emergence of two different patterns of RBC preferential location in others. Our findings have important implications in understanding and modeling blood flow in physiological and pathological conditions.

Endothelial Damage in Sepsis: The Importance of Systems Biology

The early diagnosis and appropriate stratification of sepsis continues to be one of the most important challenges in modern medicine. Single isolated biomarkers have not been enough to improve diagnostic and prognostic strategies and to progress toward therapeutic goals. The information generated by the human genome project has allowed a more holistic approach to the problem. The integration of genomics, transcriptomics, proteomics and metabolomics in sepsis has allowed us to progress in the knowledge of new pathways which are pathophysiologically involved in this disease. Thus, we have understood the importance of and complex interaction between the inflammatory response and the endothelium. Understanding the role of important parts of the microcirculation, such as the endothelial glycocalyx and its interaction with the inflammatory response, has provided early recognition elements for clinical practice that allow the rational use of traditional medical interventions in sepsis. This comprehensive approach, which differs from the classical mechanistic approach, uses systems biology to increase the diagnostic and prognostic spectrum of endothelial damage biomarkers in sepsis, and to provide information on new pathways involved in the pathophysiology of the disease. This, in turn, provides tools for perfecting traditional medical interventions, using them at the appropriate times according to the disease's pathophysiological context, while at the same time discovering new and improved therapeutic alternatives. We have the challenge of transferring this ideal scenario to our daily clinical practice to improve our patients' care. The purpose of this article is to provide a general description of the importance of systems biology in integrating the complex interaction between the endothelium and the inflammatory response in sepsis.

Possibility as role of ginseng and ginsenosides on inhibiting the heart disease of COVID-19: A systematic review

Coronavirus has been spreading rapidly around the world since it broke out in China in 2019. Respiratory diseases caused by coronavirus infection cause various diseases ranging from asymptomatic subclinical infections to severe pneumonia and cardiovascular complications, leading to death. In this regard, natural products are being studied to prevent various diseases caused by COVID-19. In current review, we would like to present mechanisms related to the inhibition of heart disease in ginseng and ginsenoside against SARS-CoV-2. In many previous studies, ginseng and ginsenoside are known to have antioxidant, blood flow improvement, improvement of vascular and heart function, blood pressure control, suppression of myocardial infarction and heart failure, and antiarrhythmia. Therefore, ginseng and ginsenoside have a possibility to suppress cardiovascular complications caused by COVID-19. Many of research provide evidence for ginseng and ginsenoside as treatments for the risk of cardiovascular complications. However, in this review, more specific contents on the proposition of the efficacy of ginseng and ginsenoside for COVID-19 should be presented. Therefore, we hope that researches to reduce cardiovascular complications of ginseng and ginsenoside for COVID-19 should be presented to reduce mortality for COVID-19.

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

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

COVID-19 and Acute Coronary Syndromes: From Pathophysiology to Clinical Perspectives

Acute coronary syndromes (ACS) are frequently reported in patients with coronavirus disease 2019 (COVID-19) and may impact patient clinical course and mortality. Although the underlying pathogenesis remains unclear, several potential mechanisms have been hypothesized, including oxygen supply/demand imbalance, direct viral cellular damage, systemic inflammatory response with cytokine-mediated injury, microvascular thrombosis, and endothelial dysfunction. The severe hypoxic state, combined with other conditions frequently reported in COVID-19, namely sepsis, tachyarrhythmias, anemia, hypotension, and shock, can induce a myocardial damage due to the mismatch between oxygen supply and demand and results in type 2 myocardial infarction (MI). In addition, COVID-19 promotes atherosclerotic plaque instability and thrombus formation and may precipitate type 1 MI. Patients with severe disease often show decrease in platelets count, higher levels of d-dimer, ultralarge von Willebrand factor multimers, tissue factor, and prolongation of prothrombin time, which reflects a prothrombotic state. An endothelial dysfunction has been described as a consequence of the direct viral effects and of the hyperinflammatory environment. The expression of tissue factor, von Willebrand factor, thromboxane, and plasminogen activator inhibitor-1 promotes the prothrombotic status. In addition, endothelial cells generate superoxide anions, with enhanced local oxidative stress, and endothelin-1, which affects the vasodilator/vasoconstrictor balance and platelet aggregation. The optimal management of COVID-19 patients is a challenge both for logistic and clinical reasons. A deeper understanding of ACS pathophysiology may yield novel research insights and therapeutic perspectives in higher cardiovascular risk subjects with COVID-19.

A Randomized, Multicenter, Open-Label, Blinded End Point, Phase 2, Feasibility, Efficacy, and Safety Trial of Preoperative Microvascular Protection in Patients Undergoing Major Abdominal Surgery

BACKGROUND

The endothelial glycocalyx, a carbohydrate-rich layer coating all endothelial surfaces, plays a fundamental role in the function of microcirculation. The primary aim of this study was to evaluate the feasibility of using dexamethasone and albumin to protect the endothelial glycocalyx in patients undergoing abdominal surgery. Secondary and exploratory outcomes included efficacy and safety.

METHODS

We conducted a multicenter, open-label, blinded end point, phase 2, randomized trial. Patients undergoing colorectal, pancreas, or liver surgery were recruited and randomized to receive either intravenous dexamethasone (16 mg) and 20% albumin (100 mL) at induction of anesthesia, then 200 mL of 20% albumin with each subsequent 1000 mL of crystalloid administered (dexamethasone and albumin [Dex-Alb] group), or crystalloid fluid only with no dexamethasone (control group). Feasibility end points included patient recruitment and retention, consent rate, and successful study drug administration. The primary efficacy end point was the measurement of plasma syndecan-1 level on postoperative day (POD) 1, and secondary end points were heparan sulfate levels and inflammatory markers measured at 4 perioperative timepoints. Safety end points included errors in administration of the intervention, hyperglycemia, occurrence of postoperative complications, and patient retention.

RESULTS

Seventy-two patients were randomized. All feasibility end points were achievable. There were no statistically significant differences observed in median (interquartile range) syndecan-1 levels on POD 1 (39 ng·mL-1 [20-97] in the Dex-Alb group versus 41 ng·mL-1 [19-84] in the control group; difference in medians -2.1, 95% confidence interval [CI], -13 to 8.6; P = .69). The Dex-Alb group had lower POD 1 heparan sulfate levels (319 ng·mL-1 [161-717] in the Dex-Alb group versus 1422 [670-2430] ng·mL-1 in the control group; difference in medians -1085, 95% CI, -1779 to -391) and C-reactive protein (CRP) levels on POD 1 (48 [29-77] mg·L-1 in the Dex-Alb group versus 85 mg·L-1 [49-133] in the control group; difference in medians -48, 95% CI, -75 to -21). Fewer patients had one or more postoperative complication in the Dex-Alb group than in the control group (6 [17%] vs 18 patients [50%]; odds ratio = 0.2, 95% CI, 0.06-0.6).

CONCLUSIONS

Intravenous dexamethasone and albumin administration was feasible but did not reduce syndecan-1 on POD 1 in patients undergoing abdominal surgery. Given the clinically important CIs observed between the groups for heparan sulfate, CRP, and postoperative complications, a larger trial assessing the associations between dexamethasone and albumin administration and these outcomes is warranted.

The Clinical Presentation of Puumala Hantavirus Induced Hemorrhagic Fever with Renal Syndrome Is Related to Plasma Glucose Concentration

Puumala hantavirus (PUUV) causes a hemorrhagic fever with renal syndrome characterized by thrombocytopenia, increased capillary leakage, and acute kidney injury (AKI). As glucosuria at hospital admission predicts the severity of PUUV infection, we explored how plasma glucose concentration associates with disease severity. Plasma glucose values were measured during hospital care in 185 patients with PUUV infection. They were divided into two groups according to maximum plasma glucose concentration: P-Gluc < 7.8 mmol/L (n = 134) and P-Gluc ≥ 7.8 mmol/L (n = 51). The determinants of disease severity were analyzed across groups. Patients with P-Gluc ≥7.8 mmol/L had higher hematocrit (0.46 vs. 0.43; p < 0.001) and lower plasma albumin concentration (24 vs. 29 g/L; p < 0.001) than patients with P-Gluc < 7.8 mmol/L. They presented with higher prevalence of pulmonary infiltrations and pleural effusion in chest radiograph, higher prevalence of shock and greater weight change during hospitalization. Patients with P-Gluc ≥ 7.8 mmol/L were characterized by lower platelet count (50 vs. 66 × 10⁹/L; p = 0.001), more severe AKI (plasma creatinine 272 vs. 151 µmol/L; p = 0.001), and longer hospital treatment (8 vs. 6 days; p < 0.001) than patients with P-Gluc < 7.8 mmol/L. Plasma glucose level is associated with the severity of capillary leakage, thrombocytopenia, inflammation, and AKI in patients with acute PUUV infection.

Blood Biomarkers Predict Cardiac Workload Using Machine Learning

Introduction

Rate pressure product (the product of heart rate and systolic blood pressure) is a measure of cardiac workload. Resting rate pressure product (rRPP) varies from one individual to the next, but its biochemical/cellular phenotype remains unknown. This study determined the degree to which an individual's biochemical/cellular profile as characterized by a standard blood panel is predictive of rRPP, as well the importance of each blood biomarker in this prediction.

Methods

We included data from 55,730 participants in this study with complete rRPP measurements and concurrently collected blood panel information from the Health Management Centre at the Affiliated Hospital of Hangzhou Normal University. We used the XGBoost machine learning algorithm to train a tree-based model and then assessed its accuracy on an independent portion of the dataset and then compared its performance against a standard linear regression technique. We further determined the predictive importance of each feature in the blood panel.

Results

We found a fair positive correlation (Pearson r) of 0.377 (95% CI: 0.375-0.378) between observed rRPP and rRPP predicted from blood biomarkers. By comparison, the performance for standard linear regression was 0.352 (95% CI: 0.351-0.354). The top three predictors in this model were glucose concentration, total protein concentration, and neutrophil count. Discussion/

Conclusion

Blood biomarkers predict resting RPP when modeled in combination with one another; such models are valuable for studying the complex interrelations between resting cardiac workload and one's biochemical/cellular phenotype.

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.

Glycosylated hemoglobin as a predictor of mortality in severe pneumonia by COVID-19

OBJECTIVE

Determine whether the levels of glycated hemoglobin (HbA1c) measured on admission to the intensive care unit (ICU) are associated with mortality in patients with severe SARS-CoV-2 pneumonia with invasive mechanical ventilation.

DESIGN

Cohort study, retrospective, observational. A single center.

PLACE

ICU of a second-level care hospital.

PATIENTS

Severe SARS-CoV-2 pneumonia confirmed with IMV since admission to the ICU.

INTERVENTIONS

none.

RESULTS

A total of 56 patients with severe pneumonia, confirmed with SARS-CoV-2, all with IMV. The group with HbA1c <6.5% included 32 (57.14%) patients and the group with HbA1c ≥6.5% included 24 (42.86%) patients and the mortality rate in ICU was 43.8% and 70.8%, respectively, with p = 0.04. Predictors of mortality at 28 days in ICU were DHL >500 U/L, OR 3.65 (95% CI 1.18-11.29), HbA1c ≥6.5%, OR 3.12 (95% CI 1.01-9.6), SAH, OR 3.12 (95% CI 1.01-9.5), use of vasopressor, OR 0.2 (95% CI 0.05-0.73), diabetes was not statistically significant.

CONCLUSION

The 28-day probability of survival in patients with severe SARS-CoV-2 pneumonia with IMV in the ICU is lower when the HbA1c level is ≥6.5% on admission.

Elevated plasma levels of syndecan-1 and soluble thrombomodulin predict adverse outcomes in thrombotic thrombocytopenic purpura

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a potentially fatal blood disorder resulting from acquired deficiency of plasma ADAMTS13 activity. Despite recent advances in early diagnosis and novel therapeutics, the mortality rate of acute iTTP remains as high as 10% to 20%. Moreover, a reliable clinical and laboratory parameter that predicts disease severity and outcomes is lacking. We show in the present study that plasma levels of syndecan-1 (Sdc-1) and soluble thrombomodulin (sTM) on admission were dramatically increased in patients with acute iTTP and remained substantially elevated in a subset of patients compared with healthy controls. The elevated admission plasma levels of Sdc-1 and sTM were associated with abnormal Glasgow coma scale scores, low estimated glomerular filtration rates, the need for intensive care, and in-hospital mortality rates. Moreover, a further simultaneous increase in plasma Sdc-1 and sTM levels at the time of clinical response/remission (eg, when normalization of platelet counts and substantial reduction of serum lactate dehydrogenase activity were achieved) was highly predictive of iTTP recurrence. These results demonstrate that endothelial injury, resulting from disseminated microvascular thromboses, is severe and persistent in patients with acute iTTP. Plasma levels of Sdc-1 and sTM on admission and in remission are predictive of in-hospital mortality and recurrence of acute iTTP, respectively. Thus, an incorporation of such novel plasma biomarkers into the risk assessment in acute iTTP may help implement a more vigorous and intensive therapeutic strategy for these patients.

The Endothelial Glycocalyx and Organ Preservation-From Physiology to Possible Clinical Implications for Solid Organ Transplantation

The endothelial glycocalyx is a thin layer consisting of proteoglycans, glycoproteins and glycosaminoglycans that lines the luminal side of vascular endothelial cells. It acts as a barrier and contributes to the maintenance of vascular homeostasis and microperfusion. During solid organ transplantation, the endothelial glycocalyx of the graft is damaged as part of Ischemia Reperfusion Injury (IRI), which is associated with impaired organ function. Although several substances are known to mitigate glycocalyx damage, it has not been possible to use these substances during graft storage on ice. Normothermic machine perfusion (NMP) emerges as an alternative technology for organ preservation and allows for organ evaluation, but also offers the possibility to treat and thus improve organ quality during storage. This review highlights the current knowledge on glycocalyx injury during organ transplantation, presents ways to protect the endothelial glycocalyx and discusses potential glycocalyx protection strategies during normothermic machine perfusion.

The neurovascular extracellular matrix in health and disease

The blood-brain barrier (BBB) is a vital interface that supports normal brain functions. Endothelial cells (ECs) are the main component of the BBB and are highly specialized to govern the transfer of substances into brain. The EC lumen is enmeshed with an extracellular matrix (ECM), known as the endothelial glycocalyx layer (EGL). The lumen-facing EGL is primarily comprised of proteoglycans (PGs) and glycosaminoglycans (GAGs), which function as the first line of defense for blood-to-brain transfer of substances. Circulating factors must first penetrate the EGL before interacting with the EC. The abundance and composition of the PG and GAGs can dictate EGL function, and determine which circulating substances communicate with the ECs. The EGL can interact with circulating factors through physio-chemical interactions with the EC. Some disease states reveal a "thinning" of the EGL that may increase EC interactions with components of the systemic circulation and alter BBB function. EGL changes may also contribute to the cognitive complications of systemic diseases, such as sepsis and diabetes. For decades, researchers have measured how genetic and environmental factors influence the peripheral EGL constituents; however, much less is known about the neurovascular EGL. In this mini-review, we introduce components of the EGL and innovative ways to measure their abundance and composition that may contribute to BBB dysfunction.

Pivotal role of endothelial cell autophagy in sepsis

Sepsis is a fatal organ dysfunction resulting from a disordered host response to infection. Endothelial cells (ECs) are usually the primary targets of inflammatory mediators in sepsis; damage to ECs plays a pivotal part in vital organ failure. In recent studies, autophagy was suggested to play a critical role in the ECs injury although the mechanisms by which ECs are injured in sepsis are not well elucidated. Autophagy is a highly conserved catabolic process that includes sequestrating plasma contents and transporting cargo to lysosomes for recycling the vital substrates required for metabolism. This pathway also counteracts microbial invasion to balance and retain homeostasis, especially during sepsis. Increasing evidence indicates that autophagy is closely associated with endothelial function. The role of autophagy in sepsis may or may not be favorable depending upon conditions. In the present review, the current knowledge of autophagy in the process of sepsis and its influence on ECs was evaluated. In addition, the potential of targeting EC autophagy for clinical treatment of sepsis was discussed.

Healthy aging and the blood-brain barrier

The blood-brain barrier (BBB) protects the central nervous system (CNS) from unregulated exposure to the blood and its contents. The BBB also controls the blood-to-brain and brain-to-blood permeation of many substances, resulting in nourishment of the CNS, its homeostatic regulation and communication between the CNS and peripheral tissues. The cells forming the BBB communicate with cells of the brain and in the periphery. This highly regulated interface changes with healthy aging. Here, we review those changes, starting with morphology and disruption. Transporter changes include those for amyloid beta peptide, glucose and drugs. Brain fluid dynamics, pericyte health and basement membrane and glycocalyx compositions are all altered with healthy aging. Carrying the ApoE4 allele leads to an acceleration of most of the BBB's age-related changes. We discuss how alterations in the BBB that occur with healthy aging reflect adaptation to the postreproductive phase of life and may affect vulnerability to age-associated diseases.

Vascular Endothelial Glycocalyx Damage in COVID-19

The new coronavirus disease-2019 (COVID-19), which is spreading around the world and threatening people, is easily infecting a large number of people through airborne droplets; moreover, patients with hypertension, diabetes, obesity, and cardiovascular disease are more likely to experience severe conditions. Vascular endothelial dysfunction has been suggested as a common feature of high-risk patients prone to severe COVID-19, and measurement of vascular endothelial function may be recommended for predicting severe conditions in high-risk patients with COVID-19. However, fragmented vascular endothelial glycocalyx (VEGLX) is elevated in COVID-19 patients, suggesting that it may be useful as a prognostic indicator. Although the relationship between VEGLX and severe acute respiratory syndrome coronavirus 2 infections has not been well studied, some investigations into COVID-19 have clarified the relationship between VEGLX and the mechanism that leads to severe conditions. Clarifying the usefulness of VEGLX assessment as a predictive indicator of the development of severe complications is important as a strategy for confronting pandemics caused by new viruses with a high affinity for the vascular endothelium that may recur in the future.

The Endothelial Glycocalyx as a Key Mediator of Albumin Handling and the Development of Diabetic Nephropathy

The endothelial glycocalyx is a complex mesh of proteoglycans, glycoproteins and other soluble components, which cover the vascular endothelium. It plays an important role in many physiological processes including vascular permeability, transduction of shear stress and interaction of blood cells and other molecules with the vascular wall. Its complex structure makes its precise assessment challenging, and many different visualization techniques have been used with varying results. Diabetes, one of the main disease models where disorders of the glycocalyx are present, causes degradation of the glycocalyx through a variety of molecular pathways and especially through oxidative stress due to the action of reactive oxygen species. As the glycocalyx has been primarily studied in the glomerular endothelium, more evidence points towards a vital role in albumin handling and, consequently, in diabetic nephropathy. Therefore, the maintenance or restoration of the integrity of the glycocalyx seems a promising therapeutic target. In this review, we consider the structural and functional capacities of the endothelial glycocalyx, the available methods for its evaluation, the mechanisms through which diabetes leads to glycocalyx degradation and albuminuria, and possible treatment options targeting the glycocalyx.

Endothelial glycocalyx damage as a systemic inflammatory microvascular endotheliopathy in COVID-19

In atherosclerosis patients, vascular endothelial dysfunction is commonly observed alongside damage of the vascular endothelial glycocalyx, an extracellular matrix bound to and encapsulating the endothelial cells lining the blood vessel wall. Although atherosclerotic risk factors have been reported in severe patients with coronavirus disease 2019 (COVID-19), the exact mechanisms are unclear. The mortality associated with the COVID-19 outbreak is increased by comorbidities, including hypertension, diabetes, obesity, chronic obstructive pulmonary disease (COPD), and cardiovascular disease. Besides, older individuals and smokers have significantly worse outcomes. Interestingly, these comorbidities and risk factors are consistent with the pathophysiology that causes vascular endothelial glycocalyx damage. Moreover, vascular glycocalyx dysfunction causes microvascular leakage, which results in interstitial pulmonary abnormal shadows (multiple patchy shadows with a ground glass inter-pneumonic appearance). This is frequently followed by severe acute respiratory distress syndrome (ARDS), closely related to coagulo-fibrinolytic changes contributing to disseminated intravascular coagulation (DIC) and Kawasaki disease shock syndrome, as well as inducing activation of the coagulation cascade, leading to thromboembolism and multiple organ failure. Notably, SARS-CoV-2, the causative virus of COVID-19, binds to ACE2, which is abundantly present not only in human epithelia of the lung and the small intestine, but also in vascular endothelial cells and arterial smooth muscle cells. Moreover, COVID-19 can induce severe septic shock, and sepsis can easily lead to systemic degradation of the vascular endothelial glycocalyx. In the current review, we propose new concepts and therapeutic goals for COVID-19-related vascular endothelial glycocalyx damage, based on previous vascular endothelial medicine research.

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

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

Innate immunity as a target for acute cardioprotection

Acute obstruction of a coronary artery causes myocardial ischaemia and if prolonged, may result in an ST-segment elevation myocardial infarction (STEMI). First-line treatment involves rapid reperfusion. However, a highly dynamic and co-ordinated inflammatory response is rapidly mounted to repair and remove the injured cells which, paradoxically, can further exacerbate myocardial injury. Furthermore, although cardiac remodelling may initially preserve some function to the heart, it can lead over time to adverse remodelling and eventually heart failure. Since the size of the infarct corresponds to the subsequent risk of developing heart failure, it is important to find ways to limit initial infarct development. In this review, we focus on the role of the innate immune system in the acute response to ischaemia-reperfusion (IR) and specifically its contribution to cell death and myocardial infarction. Numerous danger-associated molecular patterns are released from dying cells in the myocardium, which can stimulate pattern recognition receptors including toll like receptors and NOD-like receptors (NLRs) in resident cardiac and immune cells. Activation of the NLRP3 inflammasome, caspase 1, and pyroptosis may ensue, particularly when the myocardium has been previously aggravated by the presence of comorbidities. Evidence will be discussed that suggests agents targeting innate immunity may be a promising means of protecting the hearts of STEMI patients against acute IR injury. However, the dosing and timing of such agents should be carefully determined because innate immunity pathways may also be involved in cardioprotection. This article is part of a Cardiovascular Research Spotlight Issue entitled 'Cardioprotection Beyond the Cardiomyocyte', and emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Paternal deficiency of complement component C1q leads to a preeclampsia-like pregnancy in wild-type female mice and vascular adaptations postpartum

Preeclampsia is a spontaneously occurring, pregnancy-specific syndrome that is clinically diagnosed by new onset hypertension and proteinuria. Epidemiological evidence describes an association between a history of preeclampsia and increased risk for cardiovascular disease in later life; however, the mechanism(s) driving this relationship are unclear. Our study aims to leverage a novel preeclampsia-like mouse model, the C1q^-/- model, to help elucidate the acute and persistent vascular changes during and following a preeclampsia-like pregnancy. Female C57BL/6J mice were mated to C1q^-/- male mice to model a preeclampsia-like pregnancy ("PE-like"), and the maternal cardiovascular phenotype (blood pressure, renal function, systemic glycocalyx, and ex vivo vascular function) was assessed in late pregnancy and postpartum at 6 and 10 mo of age. Uncomplicated, normotensive pregnancies (female C57BL/6J bred to male C57BL/6J mice) served as age-matched controls. In pregnancy, PE-like dams exhibited increased systolic and diastolic pressure during mid- and late gestation, renal dysfunction, fetal growth restriction, and reduced placental efficiency. Ex vivo wire myography studies of mesenteric arteries revealed severe pregnancy-specific endothelial-dependent and -independent vascular dysfunction. At 3 and 7 mo postpartum (6 and 10 mo old, respectively), hypertension resolved in PE-like dams, whereas mild vascular dysfunction persisted at 3 mo postpartum. In conclusion, the female C57BL/6J-by-male C57BL/6J C1q^-/- model recapitulates many aspects of the human preeclampsia syndrome in a low-risk, wild-type female mouse. The pregnancy-specific phenotype results in systemic maternal endothelial-dependent and -independent vascular dysfunction that persists postpartum.

Endothelial glycocalyx restoration by growth factors in diabetic nephropathy

The endothelial glycocalyx (eGlx) constitutes the first barrier to protein in all blood vessels. This is particularly noteworthy in the renal glomerulus, an ultrafiltration barrier. Leakage of protein, such as albumin, across glomerular capillaries results in albumin in the urine (albuminuria). This is a hall mark of kidney disease and can reflect loss of blood vessel integrity in microvascular beds elsewhere. We discuss evidence demonstrating that targeted damage to the glomerular eGlx results in increased glomerular albumin permeability. EGlx is lost in diabetes and experimental models demonstrate loss from glomerular endothelial cells. Vascular endothelial growth factor (VEGF)A is upregulated in early diabetes, which is associated with albuminuria. Treatment with paracrine growth factors such as VEGFC, VEGF165b and angiopoietin-1 can modify VEGFA signalling, rescue albumin permeability and restore glomerular eGlx in models of diabetes. Manipulation of VEGF receptor 2 signalling, or a common eGlx biosynthesis pathway by these growth factors, may protect and restore the eGlx layer. This would help to direct future therapeutics in diabetic nephropathy.

Loss of Endothelial Glycocalyx Hyaluronan Impairs Endothelial Stability and Adaptive Vascular Remodeling After Arterial Ischemia

We recently reported that loss of hyaluronan (HA) from the endothelial glycocalyx leads to loss of vessel stability in specific microcirculatory vascular beds. Here we hypothesized that such derangements in the glycocalyx may also impair the adaptive response to vascular ischemia. Endothelial specific conditional hyaluronan synthase 2-KO (Has2-cKO) mice revealed reduced endothelial HA expression and lower hindlimb perfusion at baseline compared to control mice. After a single ligation of the common femoral artery in these mice, we observed dysregulated angiogenesis in the gastrocnemius muscle which did not restore capillary perfusion. Mechanistically, decreased endothelial binding of the pericyte-derived molecule angiopoietin1 (Ang1) could be observed in the Has2-cKO mouse. In vitro angiogenesis assays with an endothelial cell-pericyte coculture confirmed such disturbed Ang1-TIE2 signaling resulting in excessive angiogenesis upon loss of HA. These data could be of relevance to diabetes patients, where we confirm loss of endothelial HA in the microcirculation of muscle tissue, indicating that this may contribute to the known disturbed adaptation to ischemia in these patients. In summary, loss of endothelial HA results in impaired microvascular perfusion and endothelial stability in ischemic gastrocnemius muscle. Endothelial HA is a potential target to improve angiogenic therapy in diabetic patients with critical limb ischemia.

Endothelial Glycocalyx and the Peritoneal Barrier

Recent advances in the study of the microcirculation have demonstrated the critical role of the endothelial glycocalyx in transcapillary transport from the plasma to the tissue interstitium. Since the capillary wall represents the initial resistance to solute transfer from the plasma through the tissue to the dialysate, the glycocalyx is potentially of major importance to peritoneal dialysis. Inadvertently removed in early histological studies, this thin, delicate layer of glycosaminoglycans and proteoglycans is now recognized as a primary barrier in transendothelial solute and water transport. Subperitoneal endothelia are exposed to inflammation, angiogenesis, and hyperglycemia, which have been shown to affect the layer by increasing permeability. This entity permits new hypotheses concerning the factors that influence the transport characteristics of peritoneal dialysis patients and provides new avenues of basic research into the fundamental mechanisms of alteration of the peritoneal barrier.

Krogh’s capillary recruitment hypothesis, 100 years on: Is the opening of previously closed capillaries necessary to ensure muscle oxygenation during exercise?

In 1919, August Krogh published his seminal work on skeletal muscle oxygenation. Krogh’s observations indicated that muscle capillary diameter is actively regulated, rather than a passive result of arterial blood flow regulation. Indeed, combining a mathematical model with the number of ink-filled capillaries he observed in muscle cross sections taken at different workloads, Krogh was able to account for muscle tissue’s remarkably efficient oxygen extraction during exercise in terms of passive diffusion from nearby capillaries. Krogh was awarded the 1920 Nobel Prize for his account of muscle oxygenation. Today, his observations are engrained in the notion of capillary recruitment: the opening of previously closed capillaries. While the binary distinction between “closed” and “open” was key to Krogh’s model argument, he did in fact report a continuum of capillary diameters, degrees of erythrocyte deformation, and perfusion states. Indeed, modern observations question the presence of closed muscle capillaries. We therefore examined whether changes in capillary flow patterns and hematocrit among open capillaries can account for oxygen extraction in muscle across orders-of-magnitude changes in blood flow. Our four-compartment model of oxygen extraction in muscle confirms this notion and provides a framework for quantifying the impact of changes in microvascular function on muscle oxygenation in health and disease. Our results underscore the importance of capillary function for oxygen extraction in muscle tissue as first proposed by Krogh. While Krogh’s model calculations still hold, our model predictions support that capillary recruitment can be viewed in the context of continuous, rather than binary, erythrocyte distributions among capillaries.

NEW & NOTEWORTHY Oxygen extraction in working muscle is extremely efficient in view of single capillaries properties. The underlying mechanisms have been widely debated. Here, we develop a four-compartment model to quantify the influence of each of the hypothesized mechanisms on muscle oxygenation. Our results show that changes in capillary flow pattern and hematocrit can account for the high oxygen extraction observed in working muscle, while capillary recruitment is not required to account for these extraction properties.

Noninvasive sublingual microvascular imaging reveals sex-specific reduction in glycocalyx barrier properties in patients with coronary artery disease

BACKGROUND

Risk factors for coronary artery disease (CAD) have been associated with endothelial dysfunction and degradation of the endothelial glycocalyx. This study was designed to compare sublingual microvascular perfusion and glycocalyx barrier properties in CAD patients and controls using noninvasive side stream darkfield imaging.

METHODS

Imaging of the sublingual microvasculature was performed in 52 case subjects (CAD confirmed by left heart catheterization) and 63 controls (low Framingham risk score). Red blood cell (RBC) filling percentage and functional microvascular density, measures of microvascular perfusion, and perfused boundary region (PBR), an index of glycocalyx barrier function, were measured in microvessels with a diameter ranging from 5-25 µm.

RESULTS

RBC filling percentage was lower in patients with CAD compared to controls (p < .001). Functional microvascular density did not differ between groups. The overall PBR was marginally greater in the CAD group compared to the control group (p = .08). PBR did not differ between male CAD cases and controls (p = .17). However, PBR was greater in females with CAD compared with female controls (p = .04), indicating reduced glycocalyx barrier function. This difference became more pronounced after adjusting for potential confounders.

CONCLUSIONS

Our data suggest that patients with CAD are characterized by a reduction in percentage of time microvessels are occupied by RBCs. In addition, CAD is significantly associated with impaired sublingual microvascular glycocalyx barrier function in women but not men. More research is needed to determine the significance of peripheral microvascular dysfunction in the pathophysiology of CAD, and how this may differ by sex.

Difference in hematocrit and plasma albumin levels as an additional biomarker in the diagnosis of infectious disease

INTRODUCTION

In clinical practice, it has been observed that patients with severe infections show changes to their hematocrit (HCT) and serum albumin (ALB) levels. This study aimed to evaluate whether the difference of HCT and ALB (HCT-ALB) levels can be used as an additional biomarker for fast diagnosis of severe infections.

MATERIAL AND METHODS

This was a retrospective case-control study which included adult patients with severe infections, patients with non-infective conditions and healthy individuals. A total of 7,117 individuals were recruited in Yunnan Province, China, from January 2012 to January 2018, and were divided into three groups: 1,033 patients with severe infections (group 1); 1,081 patients with non-infective conditions (group 2); and 5,003 healthy individuals from the general population (group 3). The potential diagnostic threshold of HCT-ALB for severe infectious patients was determined by the receiver operating characteristic (ROC) curve analysis. Group 3 was used as the reference to draw the ROC curves of the HCT-ALB value in group 1 or group 2.

RESULTS

HCT-ALB values in each group were significantly different. We found that the area under the ROC curve (AUC) of group 1 reached 0.87 (95% CI: 0.86-0.89), whereas the AUC of group 2 was 0.60 (95% CI: 0.58-0.62). To reach a higher specificity of 99.0% (95% CI: 98.8-99.3%, and with sensitivity of 37.5%, 95% CI: 34.5-40.5%), a HCT-ALB value of 10.25 was recommended as the standard for diagnosis of severe infection.

CONCLUSIONS

The HCT-ALB value was increased in patients with infectious disease. The measurement of the HCT-ALB value (> 10.25) might be useful in the fast diagnosis of infectious disease.

Endothelial glycocalyx in acute care surgery - what anaesthesiologists need to know for clinical practice

The endothelial glycocalyx (EG) is the thin sugar-based lining on the apical surface of endothelial cells. It has been linked to the physiological functioning of the microcirculation and has been found to be damaged in critical illness and after acute care surgery. This review aims to describe the role of EG in severely injured patients undergoing surgery, discuss specific situations (e.G. major trauma, hemorrhagic shock, trauma induced coagulopathy) as well as specific interventions commonly applied in these patients (e.g. fluid therapy, transfusion) and specific drugs related to perioperative medicine with regard to their impact on EG.EG in acute care surgery is exposed to damage due to tissue trauma, inflammation, oxidative stress and inadequate fluid therapy. Even though some interventions (transfusion of plasma, human serum albumin, hydrocortisone, sevoflurane) are described as potentially EG protective there is still no specific treatment for EG protection and recovery in clinical medicine.The most important principle to be adopted in routine clinical practice at present is to acknowledge the fragile structure of the EG and avoid further damage which is potentially related to worsened clinical outcome.

Outcomes Associated With Multiple Organ Dysfunction Syndrome in Critically Ill Children With Hyperglycemia

OBJECTIVES

Patterns and outcomes of multiple organ dysfunction syndrome are unknown in critically ill children with hyperglycemia. We aimed to determine whether tight glycemic control to a lower vs. higher range influenced timing, duration, or resolution of multiple organ dysfunction syndrome as well as characterize the clinical outcomes of subgroups of multiple organ dysfunction syndrome in children enrolled in the Heart And Lung Failure-Pediatric INsulin Titration trial.

DESIGN

Planned secondary analysis of the multicenter Heart And Lung Failure-Pediatric INsulin Titration trial.

SETTING

Thirty-five PICUs.

PATIENTS

Critically ill children with hyperglycemia who received the Heart And Lung Failure-Pediatric INsulin Titration protocol from 2012 to 2016.

INTERVENTIONS

Randomization to a lower versus higher glucose target group.

MEASUREMENTS AND MAIN RESULTS

Of 698 patients analyzed, 48 (7%) never developed multiple organ dysfunction syndrome, 549 (79%) had multiple organ dysfunction syndrome without progression, 32 (5%) developed new multiple organ dysfunction syndrome, and 69 (10%) developed progressive multiple organ dysfunction syndrome. Of those whose multiple organ dysfunction syndrome resolved, 192 (34%) experienced recurrent multiple organ dysfunction syndrome. There were no significant differences in the proportion of multiple organ dysfunction syndrome subgroups between Heart And Lung Failure-Pediatric INsulin Titration glucose target groups. However, patients with new or progressive multiple organ dys function syndrome had fewer ICU-free days through day 28 than those without new or progressive multiple organ dysfunction syndrome, and progressive multiple organ dysfunction syndrome patients had fewer ICU-free days than those with new multiple organ dysfunction syndrome: median 25.1 days for never multiple organ dysfunction syndrome, 20.2 days for multiple organ dysfunction syndrome without progression, 18.6 days for new multiple organ dysfunction syndrome, and 0 days for progressive multiple organ dysfunction syndrome (all comparisons p < 0.001). Patients with recurrent multiple organ dysfunction syndrome experienced fewer ICU-free days than those without recurrence (median, 11.2 vs 22.8 d; p < 0.001).

CONCLUSIONS

Tight glycemic control target range was not associated with differences in the proportion of new, progressive, or recurrent multiple organ dysfunction syndrome. New or progressive multiple organ dysfunction syndrome was associated with poor clinical outcomes, and progressive multiple organ dysfunction syndrome was associated with worse outcomes than new multiple organ dysfunction syndrome. In future studies, new multiple organ dysfunction syndrome and progressive multiple organ dysfunction syndrome may need to be considered separately, as they represent distinct subgroups with different, potentially modifiable risk factors. Patients with recurrent multiple organ dysfunction syndrome represent a newly characterized, high-risk group which warrants attention in future research.

Uric acid induced the phenotype transition of vascular endothelial cells via induction of oxidative stress and glycocalyx shedding

Recent data suggested a causative role of uric acid (UA) in the development of renal disease, in which endothelial dysfunction is regarded as the key mechanism. Endothelial-to-mesenchymal transition (EndoMT) and shedding of the glycocalyx are early changes of endothelial dysfunction. We investigated whether UA induced EndoMT in HUVECs and an animal model of hyperuricemia fed with 2% oxonic acid for 4 wk. UA induced EndoMT in HUVECs with a generation of reactive oxygen species via the activation of membranous NADPH oxidase (from 15 min) and mitochondria (from 6 h) along with glycocalyx shedding (from 6 h), which were blocked by probenecid. GM6001, an inhibitor of matrix metalloproteinase, alleviated UA-induced glycocalyx shedding and EndoMT. Antioxidants including N-acetyl cysteine, apocynin, and mitotempo ameliorated EndoMT; however, they did not change glycocalyx shedding in HUVECs. In the kidney of hyperuricemic rats, endothelial staining in peritubular capillaries (PTCs) was substantially decreased with a de novo expression of α-smooth muscle actin in PTCs. Plasma level of syndecan-1 was increased in hyperuricemic rats, which was ameliorated by allopurinol. UA caused a phenotypic transition of endothelial cells via induction of oxidative stress with glycocalyx shedding, which could be one of the mechanisms of UA-induced endothelial dysfunction and kidney disease.-Ko, J., Kang, H.-J., Kim, D.-A., Kim, M.-J., Ryu, E.-S., Lee, S., Ryu, J.-H., Roncal, C., Johnson, R. J., Kang, D.-H. Uric acid induced the phenotype transition of vascular endothelial cells via induction of oxidative stress and glycocalyx shedding.

Edward F. Adolph Distinguished Lecture. Contemporary model of muscle microcirculation: gateway to function and dysfunction

This review strikes at the very heart of how the microcirculation functions to facilitate blood-tissue oxygen, substrate, and metabolite fluxes in skeletal muscle. Contemporary evidence, marshalled from animals and humans using the latest techniques, challenges iconic perspectives that have changed little over the past century. Those perspectives include the following: the presence of contractile or collapsible capillaries in muscle, unitary control by precapillary sphincters, capillary recruitment at the onset of contractions, and the notion of capillary-to-mitochondrial diffusion distances as limiting O₂ delivery. Today a wealth of physiological, morphological, and intravital microscopy evidence presents a completely different picture of microcirculatory control. Specifically, capillary red blood cell (RBC) and plasma flux is controlled primarily at the arteriolar level with most capillaries, in healthy muscle, supporting at least some flow at rest. In healthy skeletal muscle, this permits substrate access (whether carried in RBCs or plasma) to a prodigious total capillary surface area. Pathologies such as heart failure or diabetes decrease access to that exchange surface by reducing the proportion of flowing capillaries at rest and during exercise. Capillary morphology and function vary disparately among tissues. The contemporary model of capillary function explains how, following the onset of exercise, muscle O₂ uptake kinetics can be extremely fast in health but slowed in heart failure and diabetes impairing contractile function and exercise tolerance. It is argued that adoption of this model is fundamental for understanding microvascular function and dysfunction and, as such, to the design and evaluation of effective therapeutic strategies to improve exercise tolerance and decrease morbidity and mortality in disease.

Glycocalyx degradation leads to blood-brain barrier dysfunction and brain edema after asphyxia cardiac arrest in rats

The role of glycocalyx in blood-brain barrier (BBB) integrity and brain damage is poorly understood. Our study aimed to investigate the impacts of endothelial glycocalyx on BBB function in a rat model of cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). Male Sprague-Dawley rats subjected to 8-min asphyxia CA/CPR. Compared to controls, glycocalyx was mildly injured by CA, severely disrupted by hyaluronidase (HAase) with CA, and mitigated by hydrocortisone (HC) with CA. More importantly, the disruption of glycocalyx caused by HAase treatment was associated with higher BBB permeability and aggravated brain edema at 24 h after return of spontaneous circulation, as well as lower survival rate and poorer neurologic outcome at seventh day. Reversely, less degradation of glycocalyx by HC treatment was accompanied by higher seven-day survival rate and better neurologic outcome. Mechanistically, HAase treatment further increased CA/CPR-induced activation of glia cells and expression of inflammatory factors, whereas HC decreased them in the brain cortex and hippocampus. Glycocalyx degradation results in BBB leakage, brain edema, and deteriorates neurologic outcome after asphyxia CA/CPR in rats. Preservation of glycocalyx by HC could improve neurologic outcome and reduce BBB permeability, apparently through reduced gene transcription-protein synthesis and inflammation.

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

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