d7EB cells were fractionated using fluorescein-activated cell sorting (FACS) for ACE and kinase insert domain receptor (KDR) expression. The isolated fractions were subcultured on fibronectin-coated plates in the presence of endothelial cell basal medium and 20 ng/ml of stem cell factor, 20 ng/ml of thrombopoietin, 20 ng/ml of Fmsrelated tyrosine kinase-3 ligand, 25 ng/ml each of granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, IL-6, and IL-3, and 1 U/ml of human erythropoietin.