Assessment of Endothelial Glycocalyx Damage in Dogs: Development of a Novel Method

Presentation Description / Summary: The endothelial glycocalyx is a gel-like matrix lining the luminal surface of endothelial cells throughout the cardiovascular system. The glycocalyx has a number of important roles, including i) regulation of vascular tone, ii) regulation of vascular permeability, iii) shielding endothelial cells from circulating blood cells and iv) regulation of thrombosis and coagulation. Glycocalyx damage therefore results in leakage of macromolecules from the circulation, inflammation, platelet activation and decreased vasodilation in response to shear stress. Causes of endothelial glycocalyx damage include volume overload, sympathoadrenal activation, inflammation, excessive shear stress, shock, ischemia-reperfusion, sepsis and hyperglycemia. Glycocalyx damage has, therefore, been implicated in a wide range of pathophysiological states. However, to date it has proved highly challenging to study in clinical patients, due to its inaccessibility and inherent fragility. Methods reported in veterinary patients have therefore focussed on biomarkers of glycocalyx breakdown (which are not specific for the endothelial glycocalyx) and sidestream dark field imaging (which cannot be performed in conscious animals). Red blood cells (RBCs) are also covered in a layer of glycocalyx, the depth of which is strongly correlated with endothelial glycocalyx depth. RBC glycocalyx depth can, therefore, be measured as an accurate marker of endothelial glycocalyx health. I will describe the patented method we have developed to measure RBC glycocalyx depth, allowing direct assessment of glycocalyx health in conscious dogs for the first time. I will also describe changes in RBC glycocalyx depth in dogs with myxomatous mitral valve disease and its relationship with functional assessments of endothelial function.