Migration assay by using modified Boyden's chamber: ECs were trypsinized and seeded on the upper chamber of Boyden's chamber, which is a twochamber system separated by a collagen coated 8-μm pore size polycarbonate membranes. Lower well was filled with DMEM. The chambers were then incubated at 37°C, 5% CO2 for 3 h. Cells were migrated across the membrane and stuck to the lower part of the membrane. After the incubation, the polycarbonate membrane was fixed and stained with propidium iodide, a fluorescent nuclear probe. Cell number was counted before and after experiments to quantify the proliferation status of the loaded cells in Boyden's chamber. * P < 0.05 compared to only SNP treated cells.