The pulmonary microvascular endothelial cell glycocalyx includes sialic acid important for endothelial barrier function

Abstract

The endothelium forms a semi‐permeable barrier between constituents of the blood and underlying tissue. The endothelial glycocalyx consists of glycoproteins, glycolipids and proteoglycans which coat the cell surface. The carbohydrate network that contributes to the glycocalyx is very complex, and to date, the structure of these complex carbohydrates and their role in endothelial barrier function are unknown. We have begun to probe the molecular identities of endothelial cell surface carbohydrates in a systematic way. Initial studies examined the presence of terminal sialic acid residues. Neuraminidase is an enzyme that cleaves sialic acids from carbohydrate chains. Cultured rat pulmonary microvascular endothelial cells (PMVECs) were treated with neuraminidase from Clostridium perfringe (1 unit) for two hours. Neuraminidase treated cells exhibited loss of cell‐cell adhesion as noted by the formation of interendothelial cell gaps, and in a scratch‐wound assay neuraminidase treated cells were slower to reseal as compared to control. These observations suggest that the PMVEC glycocalyx contains terminal sialic acid residues that play a role in endothelial barrier function. Supported by HL60024.