Abstract
AimsStent deployment causes endothelial cells (EC) denudation, which promotes in-stent restenosis and thrombosis. Thus endothelial regrowth in stented arteries is an important therapeutic goal. Stent struts modify local hemodynamics, however the effects of flow perturbation on EC injury and repair are incompletely understood. By studying the effects of stent struts on flow and EC migration, we identified an intervention that promotes endothelial repair in stented arteries.Methods and ResultsIn vitro and in vivo models were developed to monitor endothelialization under flow and the influence of stent struts. A 2D parallel-plate flow chamber with 100 μm ridges arranged perpendicular to the flow was used. Live cell imaging coupled to computational fluid dynamic simulations revealed that EC migrate in the direction of flow upstream from the ridges but subsequently accumulate downstream from ridges at sites of bidirectional flow. The mechanism of EC trapping by bidirectional flow involved reduced migratory polarity associated with altered actin dynamics. Inhibition of Rho-associated protein kinase (ROCK) enhanced endothelialization of ridged surfaces by promoting migratory polarity under bidirectional flow (P < 0.01). To more closely mimic the in vivo situation, we cultured EC on the inner surface of polydimethylsiloxane tubing containing Coroflex Blue stents (65 μm struts) and monitored migration. ROCK inhibition significantly enhanced EC accumulation downstream from struts under flow (P < 0.05). We investigated the effects of ROCK inhibition on re-endothelialization in vivo using a porcine model of EC denudation and stent placement. En face staining and confocal microscopy revealed that inhibition of ROCK using fasudil (30 mg/day via osmotic minipump) significantly increased re-endothelialization of stented carotid arteries (P < 0.05).ConclusionsStent struts delay endothelial repair by generating localized bidirectional flow which traps migrating EC. ROCK inhibitors accelerate endothelial repair of stented arteries by enhancing EC polarity and migration through regions of bidirectional flow.
Highlights
Interventions used routinely to treat arterial disease, including balloon angioplasty and stent implantation, lead to damage and loss of endothelial cells (EC)
To study the influence of stent strut geometries on flow patterns and consequent effects on EC migration, we developed an in vitro flow chamber that contained three ridges that were 100 mm high and 100 mm wide and separated by 400 mm
CFD demonstrated that cell culture medium introduced at a flow rate of 21.6 ml/min would generate flow velocities that were highest through the centre (0.25 m/s) and decreased in magnitude when approaching the top and bottom of the chamber (Figure 1B top)
Summary
Interventions used routinely to treat arterial disease, including balloon angioplasty and stent implantation, lead to damage and loss of endothelial cells (EC). Given the essential role of EC in suppressing inflammation and thrombosis, the restoration of functional vascular endothelium is an important therapeutic goal to avoid the lethal consequences of in-stent restenosis and thrombosis.[1,2] There are several factors that can potentially influence re-endothelialization in stented arteries, one of which is the presence of the stent itself that provides a non-physiological surface for cell adhesion and alters blood flow.[3,4,5] the effect of stent deployment on EC repair remains poorly understood This issue is relevant in the era of drug-eluting stents, which release cytostatic compounds to prevent restenosis. Drug-eluting stents have effectively reduced rates of restenosis, they have been associated with a higher incidence of late and very late thrombosis.[1,2,6] These deleterious effects have been attributed, in part, to the effects of cytostatic compounds on vascular endothelium leading to delayed healing and subsequent exposure of stent struts for thrombus initiation.[6,7,8] There is a need to develop new strategies to accelerate endothelialization of stented arteries and thereby reduce the incidence of late and very late thrombosis
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