Phase-contrast images and density of capillary-like network formed by endothelial cells after loading of impulsive pressure. Endothelial tube formations were observed before loading (A) and at 1 h (B), 3 h (C), 6 h (D), and 24 h (E) after loading of impulsive pressure with amplitude of 1 MPa. Arrows indicate the disruption of the capillary-like structure. Scale bar is 400 μm. The area ratio of the capillary-like network to phase-contrast images was calculated time-dependently (F).