Endothelial Cell Mechanobiology: The role of the glycocalyx in MMP regulation and leukocyte attachment

Leukocyte adhesion to the surface of an inflamed endothelium is an important early event in cardiovascular disease. The glycocalyx is a carbohydrate-rich layer covering the luminal surface of endothelial cells believed to... [ view full abstract ]

Leukocyte adhesion to the surface of an inflamed endothelium is an important early event in cardiovascular disease. The glycocalyx is a carbohydrate-rich layer covering the luminal surface of endothelial cells believed to mediate cell functions such as permeability, cell alignment and migration and mechanotransduction. Due to its unique structure and location, it has also been suggested to play a role in leukocyte adhesion and the inflammatory response associated with atherosclerosis. We performed in vitro three dimensional cell culture modeling in which endothelial cells were exposed to uniform inlet wall shear stress in a variety of geometries. Our results show that enzymatic degradation of the glycocalyx results in a pro-inflammatory endothelial cell phenotype under flow conditions marked by an increase in ICAM-1 protein expression, impaired NF-κB activity, suppressed eNOS expression and an increase in leukocyte adhesion. We identified a role for matrix metalloproteinases in the disruption of the glycocalyx by showing there is a concomitant increase in MMP-2 protein expression and activity under inflammatory conditions. Moreover, our results show that glycocalyx degradation alone can mediate MMP-2 activity. In a curved tube model, we show that the expression of heparan sulfate and Syndecan-1 respond to wall shear stress gradients and this may occur through increased MMP activity. Taken together, our findings provide evidence that the glycocalyx plays a large role in mediating endothelial cell phenotype and that disruption of the glycocalyx in response to different pathologically relevant factors may be an up-stream event in endothelial cell dysfunction and consequential leukocyte adhesion.