Ang-1 induces collective directional endothelial cell migration. (A) Fold increase in migration of BAECs stimulated with Ang-1 (red) and VEGF (blue) compared with nonstimulated cells (CT; black). Wound closure was measured 6 hours after wounding. Results are from 5 independent experiments, and data are represented as mean ± SEM (*P < .05 compared with nonstimulated cells). (B) Percentage of cells single cells after 6 hours of migration. Cells were counted in 3 random fields in 3 different experiments for all treatments, and data are represented as mean ± SEM (*P < .05 compared with nonstimulated cells). (C) Representative images taken from the wound edge at the initiation of imaging (0 hours) and 6 hours after wounding of BAEC monolayers. The migration front was traced to delimit the displacement of cells, and cells that detached from the edge were outlined. Higher magnification view of the boxed region is shown. Scale bar represents 100 μm. (D) Representative vector diagrams (250 μm) of cell trajectories; each line represents the migration path of a single cell plotted from a common origin. (E) Directionality of migration was determined for CT, Ang-1, or VEGF-stimulated BAECs and displayed in rose plot diagrams that represent the frequency and directedness of cells; 0 indicates a migration perpendicular to orientation of the wound. (F) Quantification of the total and net distance of migration. Data are represented as mean ± SEM (*P < .05 compared with nonstimulated cells; †P < .05 compared with Ang-1 stimulation). (G) Persistence of migration was determined from the track of each cell recorded by time-lapse microscopy. For each condition, cells were selected in 3 different fields and tracked for 6 hours. Each column represents the average of at least 108 measurements from 3 independent experiments, and data are represented as mean ± SEM (*P < .05 compared with nonstimulated cells; †P < .05 compared with Ang-1 stimulation).