Implications Enzymatic Degradation of the Endothelial Glycocalyx on the Microvascular Hemodynamics and the Arteriolar Red Cell Free Layer of the Rat Cremaster Muscle

Abstract

The endothelial glycocalyx is a complex network of glycoproteins, proteoglycans, and glycosaminoglycans; it lines the vascular endothelial cells facing the lumen of blood vessels forming the endothelial glycocalyx layer (EGL). This study aims to investigate the microvascular hemodynamics implications of the EGL by quantifying changes in blood flow hydrodynamics post-enzymatic degradation of the glycocalyx layer. High-speed intravital microscopy videos of small arteries (around 35 μm) of the rat cremaster muscle were recorded at various time points after enzymatic degradation of the EGL. The thickness of the cell free layer (CFL), blood flow velocity profiles, and volumetric flow rates were quantified. Hydrodynamic effects of the presence of the EGL were observed in the differences between the thickness of CFL in microvessels with an intact EGL and glass tubes of similar diameters. Maximal changes in the thickness of CFL were observed 40 min post-enzymatic degradation of the EGL. Analysis of the frequency distribution of the thickness of CFL allows for estimation of the thickness of the endothelial surface layer (ESL), the plasma layer, and the glycocalyx. Peak flow, maximum velocity, and mean velocity were found to statistically increase by 24, 27, and 25%, respectively, after enzymatic degradation of the glycocalyx. The change in peak-to-peak maximum velocity and mean velocity were found to statistically increase by 39 and 32%, respectively, after 40 min post-enzymatic degradation of the EGL. The bluntness of blood flow velocity profiles was found to be reduced post-degradation of the EGL, as the exclusion volume occupied by the EGL increased the effective volume impermeable to RBCs in microvessels. This study presents the effects of the EGL on microvascular hemodynamics. Enzymatic degradation of the EGL resulted in a decrease in the thickness of CFL, an increase in blood velocity, blood flow, and decrease of the bluntness of the blood flow velocity profile in small arterioles. In summary, the EGL functions as a molecular sieve to solute transport and as a lubrication layer to protect the endothelium from red blood cell (RBC) motion near the vessel wall, determining wall shear stress.

Biophysical and biomolecular interactions of malaria-infected erythrocytes in engineered human capillaries

“…To understand how the altered deformability of P. falciparum-IRBCs contributes to microcirculatory obstruction, the mechanics of RBC flow have been modeled in vitro using narrow glass tubes or wedge-shaped, rigid PDMS (polydimethylsiloxane)-based microfluidic devices (19)(20)(21)(22)(23)(24). While these approaches have demonstrated geometric thresholds for mechanical trapping of IRBCs (20,25), they do not account for either the lubricating properties of the endothelial glycocalyx or the adhesive contributions of endothelial cells (26,27). Conversely, flowbased, endothelial monolayer models have investigated the role of different host receptors in parasite cytoadhesion (28)(29)(30), yet they are unable to capture the geometric constraints that govern IRBC flow through narrow capillary constrictions or the flow rate transitions encountered as cells traverse different-size microvessels.…”

Glycocalyx-Mediated Vascular Dissemination of Circulating Tumor Cells

“…RESULTS AND DISCUSSION 39 40 We employed a well-established methodology developed by our group to quantify the extravasation 41 efficiency of TCs in the MVNs 30 . MVNs were formed in microfluidic devices using primary human 42 umbilical vein ECs (HUVEC) and normal human lung fibroblasts (nHLF) from pooled donors. Over 43 seven days, the ECs self-assembled into perfusable, interconnected vascular networks.…”

Resuscitation After Hemorrhagic Shock in the Microcirculation: Targeting Optimal Oxygen Delivery in the Design of Artificial Blood Substitutes

“…An improved understanding of the fundamental role of the CFL in the microcirculation has contributed to assessing how the circulation responds to small (±10%) changes in Hct and blood viscosity (61). A novel methodology to measure the CFL width (62)(63)(64) has been recently developed. This technique is based on high-speed video recording (up to 30,000 frames/second) and a thresholding algorithm that converts the interface between blood and plasma into a black and white image, defining the stochastic surface of the RBC column and identifying the location of the plasma/vessel wall interface.…”

“…CFL thickness is an important feature of blood flow in the microcirculation and is proportional to the shear stress and the thickness of the endothelial glycocalyx. Hemorrhage alters glycocalyx structure and function, and changes in the CFL thickness can reflect glycocalyx shedding (64).…”