Sialic acids regulate microvessel permeability, revealed by novel in vivo studies of endothelial glycocalyx structure and function

Abstract

Key points We have developed novel techniques for paired, direct, real‐time in vivo quantification of endothelial glycocalyx structure and associated microvessel permeability.Commonly used imaging and analysis techniques yield measurements of endothelial glycocalyx depth that vary by over an order of magnitude within the same vessel.The anatomical distance between maximal glycocalyx label and maximal endothelial cell plasma membrane label provides the most sensitive and reliable measure of endothelial glycocalyx depth.Sialic acid residues of the endothelial glycocalyx regulate glycocalyx structure and microvessel permeability to both water and albumin. AbstractThe endothelial glycocalyx forms a continuous coat over the luminal surface of all vessels, and regulates multiple vascular functions. The contribution of individual components of the endothelial glycocalyx to one critical vascular function, microvascular permeability, remains unclear. We developed novel, real‐time, paired methodologies to study the contribution of sialic acids within the endothelial glycocalyx to the structural and functional permeability properties of the same microvessel in vivo. Single perfused rat mesenteric microvessels were perfused with fluorescent endothelial cell membrane and glycocalyx labels, and imaged with confocal microscopy. A broad range of glycocalyx depth measurements (0.17–3.02 μm) were obtained with different labels, imaging techniques and analysis methods. The distance between peak cell membrane and peak glycocalyx label provided the most reliable measure of endothelial glycocalyx anatomy, correlating with paired, numerically smaller values of endothelial glycocalyx depth (0.078 ± 0.016 μm) from electron micrographs of the same portion of the same vessel. Disruption of sialic acid residues within the endothelial glycocalyx using neuraminidase perfusion decreased endothelial glycocalyx depth and increased apparent solute permeability to albumin in the same vessels in a time‐dependent manner, with changes in all three true vessel wall permeability coefficients (hydraulic conductivity, reflection coefficient and diffusive solute permeability). These novel technologies expand the range of techniques that permit direct studies of the structure of the endothelial glycocalyx and dependent microvascular functions in vivo, and demonstrate that sialic acid residues within the endothelial glycocalyx are critical regulators of microvascular permeability to both water and albumin.

Endothelial glycocalyx restoration by growth factors in diabetic nephropathy

“…Notably, restoration of eGlx depth in these vessels recovered hydraulic conductivity. Similarly, we demonstrated that neuraminidase removed eGlx in perfused, single cannulated, frog mesenteric vessels, resulting in increased albumin permeability [17]. Vascular leakage and oedema are important concerns post-surgery with those experiencing perioperative ischemia (e.g.…”

Modulation of Intestinal Epithelial Glycocalyx Development by Human Milk Oligosaccharides and Non‐Digestible Carbohydrates

“…HS and HA are the major components of glycosaminoglycan in the glycocalyx . Both of them can regulate mechanotransduction and maintain gut barrier integrity . Interestingly, just like with HS also HA in the glycocalyx was increased by 3‐FL and not by 2′‐FL after 1 day of stimulation.…”

Blocking matrix metalloproteinase-mediated syndecan-4 shedding restores the endothelial glycocalyx and glomerular filtration barrier function in early diabetic kidney disease

“…Marasmium oreades agglutinin (MOA) lectin bound specifically to the endothelial glycocalyx, on the luminal surface of the GEC (determined using the membrane label R18) ( Figure 1ei). We have applied our peak-to-peak measurement technique, previously used in vivo, 39,40 for the first time on fixed kidney tissue ( Figure 1eii). Peak-to-peak measurement of MOA labeling, an index of glycocalyx thickness, demonstrated a 1.5-fold reduction in endothelial glycocalyx thickness in diabetes that is consistent with the reduction in endothelial glycocalyx depth observed by electron microscopy (Figure 1eiii).…”

“…Endothelial glycocalyx depth: peak-to-peak analysis The peak-to-peak assessment was carried out as previously described. 39,40 A line (white arrow in Figure 1ei) was drawn from the inside to the outside of the capillary loop crossing the glycocalyx first followed by the R18 endothelial membrane. The line is drawn perpendicular to the endothelial glycocalyx and the cell membrane label to get the maximum consistent depth of the glycocalyx.…”