Control of initial endothelial spreading by topographic activation of focal adhesion kinase

The time required to re-establish a functioning endothelial cell layer after vascular implant placement is critical to the success of the respective cardiologic or surgical intervention. Topographic modifications of implant surfaces promise to expedite endothelial regeneration by triggering the activation of cellular machineries that facilitate cell spreading. Exploiting nanoimprint lithography techniques on cyclic olefin copolymer foils, we engineered biocompatible submicron- and micro-structured gratings with groove and ridge width of 1 or 5 mu m and groove depth ranging from 0.1 to 2 mu m. Our results reveal that both the onset of endothelial spreading and subsequent texture-guided cell polarization critically depend on the feature size of the underlying topography, yet are independently modulated by the surface texture. Specifically, we demonstrate that on gratings with ridge and groove width of 1 mu m and groove depth of 1 mu m or deeper, the onset of endothelial spreading is 40% faster than on flat substrates, and that the cells align within ten degrees to the gratings. On this topography, we identify two independently regulated phases: acceleration of the onset of spreading supported by the rapid activation of integrin signaling proceeding via Focal Adhesion Kinase, and contact guidance which requires ROCK1/2 and myosin-II dependent cell contractility and focal adhesion maturation.