Abstract 521: Endothelial Cell Forward Migration in a Disturbed Wall Shear Stress Environment is Promoted by Rho-Kinase Inhibition

Abstract

Stent deployment to treat coronary artery disease causes damage and loss of endothelial cells (EC). Repair of injured arteries by EC migration is co-ordinated by Rho family GTPases. It is also regulated by wall shear stress (WSS), a mechanical force exerted by flowing blood on the vessel wall, via mechanisms that are poorly understood. It was hypothesised that stent struts may impede repair of injured endothelium by inducing localised disturbances in WSS. To simulate a stented artery in vitro, chamber slides were fabricated with ridges (100 μm high) positioned perpendicularly to the flow direction. Confluent EC monolayers seeded on one side of either ridged or non-ridged (control) chambers were exposed to flowing culture medium (Ibidi® system). Flow patterns were determined by computational fluid dynamic (CFD) modelling and particle velocimetry. Live cell imaging and analysis using ImageJ® software enabled quantification of EC migration velocity and directional persistence (DP). EC on the non-ridged chamber slide were exposed to a uniform WSS of 13 dyn/cm2 and migrated relatively uniformly in parallel with the flow direction (average velocity 1.13 μm/min; DP 0.59). By contrast, CFD and particle velocimetry revealed spatial WSS differences over the ridged chamber, with significant spikes above physiological levels (>70 dyn/cm2) at the corners of the ridges and distinctive flow recirculation zone immediately downstream from ridges (-4 dyn/cm2). While EC were able to migrate over the ridges, cells that reached the recirculation zone displayed non-uniform directionality (DP 0.25) and reduced velocity (0.78 μm/min). Inhibition of the RhoA signalling pathway with ROCK inhibitors promoted EC forward migration within the recirculation zone by elevating DP (0.41) and velocity (1.16 μm/min). It was concluded that disturbed WSS downstream from stent strut-like ridges prevented the forward migration of EC. Inhibition of the RhoA/ROCK signaling pathway promoted EC migration and re-population of these sites. Our data suggest that treatment using a ROCK inhibitor may promote re-endothelialisation of stented arteries.