ABSTRACT: Potter and Damiano recently assessed the hydrodynamic dimensions of the endothelial glycocalyx in vivo (mouse cremaster muscle venules) and in vitro (human umbilical vein and bovine aorta endothelium cultured in perfused microchannels) using fluorescent microparticle image velocimetry (Circ Res. 2008;102:770-776). Great discrepancy was observed, the glycocalyx presenting a zone of interaction extending approximately 0.52 microm into the vessel lumen in vivo, but only 0.02 to 0.03 microm from cultured cells. In an accompanying editorial, Barakat cautioned that the difference in hydrodynamic interaction did not allow one to conclude that the cultured cells totally lack a physical cell surface layer capable of mechanotransduction (Circ Res. 2008;102:747-748). To stabilize the glycocalyx for electron microscopic investigation, we perfusion-fixed 6 human umbilical veins and confluent and nonconfluent cultures (5 each) of human umbilical vein endothelial cells (HUVECs) with lanthanum/glutaraldehyde solution. Ex vivo, the thickness of glycocalyx of umbilical vein endothelium averaged 878 nm. HUVECs in vitro presented a glycocalyx with a dense-zone thickness of only 29.4 nm, plus sparse filaments reaching out on average to 118 nm, there being no difference between the nonconfluent and confluent cells. Immunohistology demonstrated the presence of heparan sulfates and syndecan-1, main constituents of the glycocalyx, both ex vivo and in vitro. These results support the observed discrepancy between glycocalyx thickness in vivo and in vitro, now for one and the same type of human cell. The presence of heparan sulfates and syndecan-1 also on cultured cells may explain why mechanotransduction phenomena can be observed even with a nonmature glycocalyx.
Circulation Research 06/2009; 104(11):1313-7. · 9.49 Impact Factor
ABSTRACT: Major causes of death after heart transplantation are right ventricular pump failure and, chronically, cardiac allograft vasculopathy. Traditional preservation techniques focus on immediate cardioplegia, without particularly considering vascular demands. Recently, the endothelial surface layer, composed of the endothelial glycocalyx and plasma proteins, was discovered to play a major role in vascular barrier function, edema formation, and leukocyte-to-endothelial interaction. The impact of augmenting a traditional preservation solution with plasma colloid albumin was therefore investigated.
Guinea pig hearts underwent cold ischemic storage for 4 hr using Bretschneider's solution (histidine-tryptophan-ketoglutarate [HTK]) without and with augmentation with 1 g% human albumin. After reperfusion, intracoronary adhesion of polymorphonuclear granulocytes, edema formation, left and right heart performance of pressure-to-volume work, and glycocalyx shedding were assessed.
Intracoronary retention of leukocytes was doubled in the traditional group (36.4+/-6.6%), whereas it remained at basal values after albumin preservation (23.5+/-2.4%; P<0.05). Addition of albumin to HTK significantly decreased edema formation (wet to dry weight ratio 6.9+/-0.1 vs. 7.2+/-0.2; P<0.05). Although left heart performance was comparable, right heart cardiac output was doubled in hearts having received HTK containing albumin versus HTK alone (94+/-14 vs. 50+/-11 mL/min/g; P<0.05). Glycocalyx shedding was significantly reduced when the hearts were stored under albumin protection.
Augmenting HTK with human albumin improves endothelial integrity and heart performance after 4 hr cold ischemia, because of a marked protection of the endothelial glycocalyx. For the prevention of acute and chronic graft failure, the glycocalyx might represent a new target.
Transplantation 04/2009; 87(7):956-65. · 4.00 Impact Factor
The Journal of Physiology 09/2008; 586(Pt 19):4585-6. · 4.72 Impact Factor