An 11-μm-Thick Glycocalyx?

Abstract

The endothelial glycocalyx is composed of glycoproteins, proteoglycans, and glycosaminoglycans within a high-water-content meshwork overlying the endothelial cells lining blood vessels. This structure maintains the integrity of vascular permeability, protects endothelial cells against leukocytes and red blood cells, and regulates vascular flow and function.1,2 The preservation of the thickness of the glycocalyx is now thought to be an important aspect mediating vascular health; hence, a decrease in thickness may play a role in chronic vascular disease.3 Recently, there has been a discussion in the literature regarding the discrepancy of the glycocalyx measurements in vitro and in vivo.4 Most often, researchers have used traditional transmission electron microscopy (TEM) methods to preserve in vitro glycocalyx, resulting in measurements of less than 100 nm.5 By comparison, recent in vivo imaging studies have demonstrated a much thicker glycocalyx of 8.9 μm.6 To improve on the accuracy of in vitro measurement, researchers are now pursuing additional methodologies to better preserve the hydrated native and gel-like state of the glycocalyx. In this month's issue of Arteriosclerosis, Thrombosis, and Vascular Biology , Ebong et al7 present a cryofixation technique termed rapid freezing and freeze substitution (RF/FS) and report on the preservation and measurement of an 11-μm-thick glycocalyx. See accompanying article on page 1908 The cyrotechnique method used by Ebong et al7 is not new, as it was developed back in the 1950s for improved morphological and histochemical preservation of tissues examined by light microscopy.8 Rapid freezing is thought to …