Permselectivity of angiogenic microvessels following alteration of the endothelial fiber matrix by oligosaccharides.

The endothelial glycocalyx, which is composed of integral and peripheral glycoconjugates, forms a fibrous matrix that confers macromolecular sieving properties on the microvascular wall. Changes in pore size within the matrix may regulate macromolecular access to the paracellular and/or vesicular transendothelial pathways. We tested the hypothesis that modifications of the endothelial glycocalyx might play a role in the ontogeny of endothelial permselectivity in proliferating microvessels of the chick chorioallantoic membrane (CAM). Accordingly, we evaluated the effects of Dolichos biflorus agglutinin (DBA) or Arachis hypogaea agglutinin (PNA) lectin binding, and N'N'diacetylchitobiose or hydroxyethyl starch polysaccharide (HES) incorporation on CAM endothelial restriction of FITC-dextrans 40 or 150 at Days 4.5 and 5.0 of development. Extravasation of FITC-dextrans was determined by recording their perivascular interstitial intensities. Following DBA, PNA, and N'N'diacetylchitobiose administration, interstitial accumulation of the tracers near first-order pre- and postcapillaries, and surrounding the capillaries, was similar to that of controls at both Days 4.5 and 5.0. At Day 4.5, pretreatment with HES significantly decreased extravasation of FITC-dextran 40. Thus, retention of HES molecules within the glycocalyx might tighten the matrix, and reduce access of dextran 40 to transendothelial pathways across the angiogenic microvessels.