Fig. 2

Higher seeding density yields higher expression of differentiation marker FLK1 (FLK1 = VEGFR = KDR, kinase insert domain receptor). The effect of (a) seeding density, (b) vascular endothelial growth factor (VEGF) concentration, and induction time on the percentage of FLK1⁺ vascular progenitor cells (VPCs) generated from embryonic stem cells (ESCs). An induction time of three days combined with a seeding density of 10,000 cells/cm² resulted in high percentages of FLK1⁺ cells regardless of VEGF concentration. c Phase contrast images and flow cytometic cell scanning histograms of FLK1 expression of ESCs induced on 50 ng/mL fibronectin with 20 ng/mL VEGF treatment. Upper panel shows time course following seeding densities of 1,000 cells/cm². Lower panel shows time course following seeding densities of 10,000 cells/cm². By day 3 post induction, the majority of cells seeded at 10,000 cells/cm² exhibit FLK1 receptor expression. In contrast, cells initially seeded at 1,000 cells/cm² exhibit less FLK1 receptor expression and exhibit fewer cell clusters at day 3