Multimodal measurement of glycocalyx degradation during coronary artery bypass grafting

Abstract

BackgroundGlycocalyx shedding and subsequent endothelial dysfunction occur in many conditions, such as in sepsis, in critical illness, and during major surgery such as in coronary artery bypass grafting (CABG) where it has been shown to associate with organ dysfunction. Hitherto, there is no consensus about the golden standard in measuring glycocalyx properties in humans. The objective of this study was to compare different indices of glycocalyx shedding and dysfunction. To this end, we studied patients undergoing elective CABG surgery, which is a known cause of glycocalyx shedding.Materials and methodsSublingual glycocalyx thickness was measured in 23 patients by: 1) determining the perfused boundary region (PBR)—an inverse measure of glycocalyx thickness—by means of sidestream dark field imaging technique. This is stated double, 2) measuring plasma levels of the glycocalyx shedding products syndecan-1, hyaluronan, and heparan sulfate and 3) measuring plasma markers of impaired glycocalyx function and endothelial activation (Ang-2, Tie-2, E-selectin, and thrombomodulin). Measurements were performed directly after induction, directly after onset of cardiopulmonary bypass (CPB), and directly after cessation of CPB. We assessed changes over time as well as correlations between the various markers.ResultsThe PBR increased from 1.81 ± 0.21 μm after induction of anesthesia to 2.27 ± 0.25 μm (p < 0.0001) directly after CPB was initiated and did not change further during CPB. A similar pattern was seen for syndecan-1, hyaluronan, heparan sulfate, Ang-2, Tie-2, and thrombomodulin. E-selectin levels also increased between induction and the start of CPB and increased further during CPB. The PBR correlated moderately with heparan sulfate, E-selectin, and thrombomodulin and weakly with Syndecan-1, hyaluronan, and Tie-2. Shedding markers syndecan-1 and hyaluronan correlated with all functional markers. Shedding marker heparan sulfate only correlated with Tie-2, thrombomodulin, and E-selectin. Thrombomodulin correlated with all shedding markers.ConclusionOur results show that glycocalyx thinning, illustrated by increased sublingual PBR and increased levels of shedding markers, is paralleled with impaired glycocalyx function and increased endothelial activation in CABG surgery with CPB. As correlations between different markers were limited, no single marker could be identified to represent the glycocalyx in its full complexity.

Classification and Molecular Functions of Heparan Sulfate Proteoglycans and Their Molecular Mechanisms with the Receptor

“…Due to various stimuli and pathological conditions, it peels off, releases into the blood, and then regenerates, a process that repeats repeatedly. As one way to recognize glycocalyx damage, blood concentrations of these released glycocalyx components, including Syndecan-1, HS, and HA, etc., are measured for research purposes [62,63]. On the other hand, visualizing glycocalyx is an extremely difficult task, and even with current technology, it is difficult to directly evaluate glycocalyx structure in vivo.…”

Insights into the Molecular Mechanism of Endothelial Glycocalyx Dysfunction during Heart Surgery

“…EGC shedding following heart surgery is also facilitated by ischemia-reperfusion damage, which releases heparan sulfate and syndecan-1 into the circulation [86][87][88]. Even after off-pump CABG surgery, CPB causes an inflammatory response that increases the shedding of heparan sulfate and syndecan-1 [89].…”

“…Employing commercially available enzymelinked immunosorbent assays or enzyme immunoassay kits facilitate the identification and quantification of numerous bioactive molecules, metabolites, cytokines, and other pertinent parameters released or produced by the endothelium. Notable among the frequently studied biomarkers of EGC are angiopoietin-1 and 2, ICAM-1, VECAM-1, P and E-selectin, chondroitin sulfate, hyaluronan, heparan sulfate, and syndecan-1 [62,87,88,[92][93][94][95][96][97][98][99]. Target peptides or proteins can have their protein expression levels measured using the Western blot method.…”

Glycocalyx–Sodium Interaction in Vascular Endothelium

“…A combination of biochemical and immunological techniques such as ELISA are commonly used in the determination of the concentration of glycocalyx breakdown products [ 154 , 155 ]. The thickness of the glycocalyx may also be determined indirectly by using a side stream dark field imaging technique [ 156 ]. Other techniques such as atomic force microscopy and liquid chromatography with selected reaction monitoring in tandem with mass spectrometry (LC-SRM/MS) have been used to successfully determine the glycocalyx thickness disruption in both in vivo and in vitro assays [ 157 ].…”