| The endothelial glycocalyx (EG) is a highly hydrated, complex extracellular macromolecular, gel-like structure on the apical surface of blood endothelial cells. It acts as a mediator between the blood and the endothelium and is degraded in cases of vascular disease such as diabetes and atherosclerosis. Microparticle image velocimetry (mu-PIV) is used to determine the hydrodynamically relevant thickness of the EG under a variety of experimental conditions, both in vivo and in vitro.;The effect of hyaluronidase, heparinase and TNF-alpha on the EG was tested in post-capillary venules with a broad range of diameters (-20-100 mum). All treatments reduced the thickness of the EG from ∼0.5 microm to ∼0 microm.;As the degradation of the EG is part of the natural process of vascular injury and inflammation, it is important to address the mechanisms of recovery as well as degradation. To fully examine the recovery time course of the EG after degradation in vivo, the thickness of the EG was monitored the same day the glycocalyx was degraded and one, three, five and seven days after wild type mice received one of three treatments that degrade the EG. It was found that, for all treatments, approximately one week was required for the EG to restore its native thickness.;In addition to in vivo studies, micro-PIV was used to interrogate the surface glycocalyx on endothelial cells (ECs) cultured in vitro, as previous studies have revealed large discrepancies in the behavior of ECs compared with endothelium in vivo. Results revealed that when cultured under standard conditions, endothelial cells grown in vitro do not possess an EG that is functionally equivalent to that found in vivo, as no EG was detectable on the cultured cells. Neither increasing the culture time nor adding free oxygen radical scavengers to the culture media enabled EC to produce a detectable EG in vitro.;In light of these results, current endothelial culture models are inadequate for modeling healthy endothelium. Future in vitro studies will need to address this shortcoming before the EC culture model can shed light on microvascular processes that are determined or influenced by cell surface chemistry. |
