Fig. 1.

Higher seeding density yields higher expression of differentiation marker FLK1 (FLK1 = VEGFR = KDR, VEGF receptor, kinase insert domain receptor). Schematic of staged differentiation of embryonic stem cells (ESCs) into vascular progenitor cells (VPCs) and endothelial cells (ECs) with representative micrographs from A3-ESCs seeded at 10,000 cells/cm². Stage 1 involves the culturing of ESCs on fibronectin in the presence of BMP4 (bone morphogenetic protein 4) and VEGF (vascular endothelial growth factor). At the completion of Stage 1, resulting VPCs are assayed for FLK1 receptor expression by an anti-FLK1 antibody