How to prevent leaky vessels during reperfusion? Just keep that glycocalyx sealant in place!

Myocardial edema is a hallmark of ischemia-reperfusion-related cardiac injury. Ischemia-reperfusion has been shown to result in degradation of the endothelial glycocalyx. The glycocalyx is the gel-like mesh of polysaccharide structures and absorped plasma proteins on the luminal side of the vasculature, and in the past decade has been shown to play an important role in protection of the vessel wall, including its barrier properties. Prevention of glycocalyx loss or restoration of a damaged glycocalyx may be a promising therapeutic target during clinical procedures involving ischemia-reperfusion

Endothelial Surface Layer Degradation by Chronic Hyaluronidase Infusion Induces Proteinuria in Apolipoprotein E-Deficient Mice

Functional studies show that disruption of endothelial surface layer (ESL) is accompanied by enhanced sensitivity of the vasculature towards atherogenic stimuli. However, relevance of ESL disruption as causal mechanism for vascular dysfunction remains to be demonstrated. We examined if loss of ESL through enzymatic degradation would affect vascular barrier properties in an atherogenic model. Eight week old male apolipoprotein E deficient mice on Western-type diet for 10 weeks received continuous active or heat-inactivated hyaluronidase (10 U/hr, i.v.) through an osmotic minipump during 4 weeks. Blood chemistry and anatomic changes in both macrovasculature and kidneys were examined. Infusion with active hyaluronidase resulted in decreased ESL (0.32±0.22 mL) and plasma volume (1.03±0.18 mL) compared to inactivated hyaluronidase (0.52±0.29 mL and 1.28±0.08 mL, p<0.05 respectively).Active hyaluronidase increased proteinuria compared to inactive hyaluronidase (0.27±0.02 vs. 0.15±0.01 µg/µg protein/creatinin, p<0.05) without changes in glomerular morphology or development of tubulo-interstitial inflammation. Atherosclerotic lesions in the aortic branches showed increased matrix production (collagen, 32±5 vs. 18±3%; glycosaminoglycans, 11±5 vs. 0.1±0.01%, active vs. inactive hyaluronidase, p<0.05). ESL degradation in apoE deficient mice contributes to reduced increased urinary protein excretion without significant changes in renal morphology. Second, the induction of compositional changes in atherogenic plaques by hyaluronidase point towards increased plaque vulnerability. These findings support further efforts to evaluate whether ESL restoration is a valuable target to prevent (micro) vascular disease progressio

Vascular Leaking, a Pivotal and Early Pathogenetic Event in Systemic Sclerosis: Should the Door Be Closed?

The early phase of systemic sclerosis (SSc) presents edema as one of the main features: this is clinically evident in the digital swelling (puffy fingers) as well as in the edematous skin infiltration of the early active diffuse subset. Other organs could be affected by this same disease process, such as the lung (with the appearance of ground glass opacities) and the heart (with edematous changes on cardiac magnetic resonance imaging). The genesis of tissue edema is tightly linked to pathological changes in the endothelium: various reports demonstrated the effect of transforming growth factor β, vascular endothelial growth factor and hypoxia-reperfusion damage with reactive oxygen species generation in altering vascular permeability and extravasation, in particular in SSc. This condition has an alteration in the glycocalyx thickness, reducing the protection of the vessel wall and causing non-fibrotic interstitial edema, a marker of vascular leak. Moreover, changes in the junctional adhesion molecule family and other adhesion molecules, such as ICAM and VCAM, are associated with an increased myeloid cells' extravasation in the skin and increased myofibroblasts transformation with further vascular leak and cellular migration. This mini-review examines current knowledge on determinants of vascular leak in SSc, shedding light on the role of vascular protection. This could enhance further studies in the light of drug development for early treatment, suggesting that the control of vascular leakage should be considered in the same way that vasodilation and inflammation reduction, as potential therapeutic targets

Monitoring the Size and Lateral Dynamics of ErbB1 Enriched Membrane Domains through Live Cell Plasmon Coupling Microscopy

To illuminate the role of the spatial organization of the epidermal growth factor receptor (ErbB1) in signal transduction quantitative information about the receptor topography on the cell surface, ideally on living cells and in real time, are required. We demonstrate that plasmon coupling microscopy (PCM) enables to detect, size, and track individual membrane domains enriched in ErbB1 with high temporal resolution. We used a dendrimer enhanced labeling strategy to label ErbB1 receptors on epidermoid carcinoma cells (A431) with 60 nm Au nanoparticle (NP) immunolabels under physiological conditions at 37°C. The statistical analysis of the spatial NP distribution on the cell surface in the scanning electron microscope (SEM) confirmed a clustering of the NP labels consistent with a heterogeneous distribution of ErbB1 in the plasma membrane. Spectral shifts in the scattering response of clustered NPs facilitated the detection and sizing of individual NP clusters on living cells in solution in an optical microscope. We tracked the lateral diffusion of individual clusters at a frame rate of 200 frames/s while simultaneously monitoring the configurational dynamics of the clusters. Structural information about the NP clusters in their membrane confinements were obtained through analysis of the electromagnetic coupling of the co-confined NP labels through polarization resolved PCM. Our studies show that the ErbB1 receptor is enriched in membrane domains with typical diameters in the range between 60–250 nm. These membrane domains exhibit a slow lateral diffusion with a diffusion coefficient of  = |0.0054±0.0064| µm2/s, which is almost an order of magnitude slower than the mean diffusion coefficient of individual NP tagged ErbB1 receptors under identical conditions

Changes in myocardial fluid filtration are reflected in epicardial lymph pressure

The effect of increased fluid filtration on stopped-flow epicardial lymph pressure (P(lymph)), used as an indicator of myocardial interstitial volume, was investigated in the anesthetized open-chest dog. Histamine infusion resulted in an increased systolic peak in the P(lymph) signal together with an increase in diastolic P(lymph) in four of five animals. During reactive hyperemia, systolic and diastolic P(lymph) increased to 127 +/- 8 and 121 +/- 6.7% (mean +/- SE, n = 6) of control, respectively. Peak P(lymph) was approximately 15 s later than peak coronary blood flow and venous pressure (P(ven)). When P(ven) was transiently elevated to 367 +/- 72 (systolic) and 247 +/- 45% (diastolic) of control, P(lymph) increased to 132 +/- 12 and 120 +/- 5.5% of control. The time of response was similar for P(ven) and P(lymph) (t50 approximately 2 S). The increased systolic and diastolic P(lymph) can be explained by an increase in interstitial and lymph filling. It is concluded that changes in myocardial fluid filtration are reflected in epicardial P(lymph). Furthermore, it seems that cardiac contraction constitutes an important defense mechanism against the formation of myocardial edem

Agonist-induced impairment of glycocalyx exclusion properties: contribution to coronary effects of adenosine

The endothelial glycocalyx is the negatively charged, gel-like mesh residing at the luminal side of the vascular endothelium and forming the interface between the flowing blood and the vessel wall. The vast majority of glycocalyx volume resides in the microcirculation, particularly in the capillaries. Intravital microscopic observations of capillaries in striated muscle preparations illustrate that under resting conditions, the glycocalyx is not accessible for flowing red blood cells and greatly hinders plasma flow in the axial direction, causing a significant reduction in functionally perfused capillary volume. Glycocalyx exclusion properties have been shown to be reduced by adenosine and other vasoactive substances. A diminished exclusion of circulating blood by the glycocalyx may facilitate nutrient exchange since it is associated with an increase in functionally perfused blood volume and surface area in the capillaries. Our recent studies have focused on the effect of adenosine on glycocalyx exclusion in the coronary circulation and demonstrate an important role for this mechanism in the increase in circulating coronary blood volume during administration of this vasodilator. The current review elaborates on the glycocalyx as a blood-excluding intravascular layer and how it can be modulated by various agonists. Further, the potential role of adenosine-induced modulation of glycocalyx exclusion properties in coupling increases in blood flow and circulating blood volume in the coronary circulation is discussed. Finally, we consider how degradation of the glycocalyx may impact on coronary blood volume regulation, thereby providing new opportunities to diagnose glycocalyx damage in the clinical settin

Endothelial glycocalyx: sweet shield of blood vessels

At the time that the term glycocalyx ("sweet husk") was introduced as a description of the extracellular polysaccharide coating on cells (Bennett HS: 1963. Morphological aspects of extracellular polysaccharides. J Hist Cytochem 11:14-23.), early electron microscopic observations had shown that anionic polysaccharides were also presented by the inner surface of blood vessels but the length of these structures was considered to be small and their functional significance was unknown. Research in the past decades in the glycocalyx field has evolved, and recent estimations indicate that the endothelial glycocalyx constitutes a voluminous intravascular compartment that plays an important role in vascular wall homeostasis. Pathologic loss of glycocalyx may be associated with an impaired vascular wall protection throughout the circulatory system, whereas agonist-induced modulation of glycocalyx accessibility for circulating blood may constitute a physiologically relevant mechanism to regulate functionally perfused volume and exchange area at the microvascular level. Both aspects are discussed in the current revie