Effect of Mechanical Environment of Focal Adhesions on Remodeling of Endothelial Cells Subjected to Cyclic Stretching Using Microsubstrates

Abstract

Endothelial cells (ECs) adapt to mechanical environments such as cyclic stretching by altering their morphology and cytoskeletal structure. The detailed mechanism underlying EC remodeling in response to cyclic stretching, however, remains unclear. To understand the contribution of strain in contact area between focal adhesions (FAs) and the substrate to morphological and cytoskeletal changes in cells, we applied cyclic stretching to ECs using a microsubstrate with arrays of micropillars on which cells were selectively stretched between FAs but FA-substrate contact area were hardly stretched. Bovine aortic ECs were seeded on a silicone elastomer micropillar substrate in a silicone chamber. ECs were then subjected to 20% stretching at 0.5 Hz for up to 6 h using a stretching apparatus. Cells stretched on a flat substrate were also observed. Under static conditions, no significant difference was seen in EC morphology between flat and micropillar substrates. After exposure to cyclic stretching for 3 h, ECs on both flat and micropillar substrates were aligned perpendicular to the direction of stretching. Stress fibers were oriented about 60° to the direction of stretching on the flat substrate, while stress fibers were not aligned in any direction for the micropillar substrate. After 6 h of stretching, stress fibers on the micropillar substrate were oriented approximately 90° to the direction of stretching. These results suggest that strain in contact area between FAs and the substrate may have an impact on reorientation rates of stress fibers in ECs in response to cyclic stretching.