Tube formation assay
Ninety-six-well plates were precoated with 50 μL liquid Matrigel per well. After incubation at 37°C for 1 hour, HUVESs (1.5 × 104 cells/well), suspended in DMEM medium with PBS, 10 nmol/L thrombin, 25 nmol/L r-hirudin, 50 nmol/L DTIP, 10 nmol/L thrombin + 25 nmol/L r-hirudin and 10 nmol/L thrombin + 50 nmol/L DTIP and were seeded and cultured for 8 hours. Five randomly chosen fields were photographed and counted.