FIG. 2.

Effects of K13/vFLIP transduction on HUVEC proliferation and ECM-dependent cord formation. (A) Proliferation assay. HUVEC transduced with either vector or K13/vFLIP-retrovirus were cultured (96-well plate) overnight without growth factors and then incubated for additional an 48 h in medium alone or medium supplemented with VEGF (25 ng/ml), bFGF (25 ng/ml), or endothelial cell growth supplement (ECGF [Sigma-Aldrich]). Proliferation was measured by [³H]thymidine deoxyribose uptake during the last 16 h of culture. (B) Growth curve. Cells were seeded on gelatin-coated 48-well plates (10,000 cells/well). At each time point, cells were treated with trypsin and counted. Control and K13/vFLIP cells reached 100% confluence on days 4 and 5, respectively. (C) HUVEC (15,000 cells/well) were seeded onto 48-well plates coated with solidified Matrigel (BD Bioscience) and incubated at 37°C overnight. Cord angles were counted under phase-contrast microscopy (original magnification, ×40 [top graph]). Representative images of cord formation by control and K13-expressing HUVEC are shown (bottom panels). The results reflect the means (± SDs) of triplicate counts from three experiments.