Patterns of Living β-Actin Movement in Wounded Human Coronary Artery Endothelial Cells Exposed to Shear Stress

We previously demonstrated that physiologic levels of shear stress enhance endothelial repair. Cell spreading and migration, but not proliferation, were the major mechanisms accounting for the increases in wound closure rate (Albuquerque et al., 2000, Am. J. Physiol. Heart Circ. Physiol. 279, H293–H302). However, the patterns and movements of β-actin filaments responsible for cell motility and translocation in human coronary artery endothelial cells (HCAECs) have not been previously investigated under physiologic flow. HCAECs transfected with β-actin-GFP were cultured on type I collagen-coated coverslips. Confluent cell monolayers were subjected to laminar shear stress of 12 dynes/cm² for 18 h in a parallel-plate flow chamber to attain cellular alignment and then wounded by scraping with a metal spatula and subsequently exposed to a laminar shear stress of 20 dynes/cm² (S-W-sH) or static (S-W-sT) conditions. Time-lapse imaging and deconvolution microscopy was performed during the first 3 h after imposition of S-W-sH or S-W-sT conditions. The spatial and temporal dynamics of β-actin-GFP motility and translocation during wound closure in HCAEC monolayers were analyzed under both conditions. Compared with HCAEC under S-W-sT conditions, our data show that HCAEC under S-W-sH conditions demonstrated greater β-actin-GFP motility, filament and clumping patterns, and filament arcs used during cellular attachment and detachment. These findings demonstrate intriguing patterns of β-actin organization and movement during wound closure in HCAEC exposed to physiological flow.