Fig. 4.

Small interfering RNA (siRNA) studies of hypoxia-inducible factor-α (HIFα). A: light microscope images (top) and fluorescence microscope images (bottom; phalloidin in green, nuclei in blue) of 3D collagen culture of HUVECs transfected with siRNA of luciferase, HIF1α, and HIF2α after 48 h (scale bars, 100 μm). B: tube length, thickness, and area coverage of untreated cells, DPI-treated cells, and HIF1α- and HIF2α-silenced cells. *P < 0.05, **P < 0.01, ***P < 0.001. C: viability of HUVECs at multiple time points as a comparison of luciferase-transfected cells to HIF1α and HIF2α siRNA-treated cells.