Fig. 4. VEGF induces the formation of committed blood progenitors. (A) EBs grown for 2.5 days in serum-free culture with 4 ng/ml Bmp4 were stimulated with activin A and bFGF or with activin A, bFGF and VEGF and assayed at days 4, 5 and 6 for the presence of hematopoietic progenitors by colony-forming ability in secondary replating assay. ^*A statistically significant difference (P<0.05) compared with the serum control at the same time point. Data are presented as the mean number of colonies from three dishes. Error bars represent s.e.m. (B) CD41 and CD34 expression was determined by flow cytometric analysis of cells derived from day-6 EBs stimulated as indicated. (C) CD45 and Mac1 expression was determined by flow cytometric analysis of cells derived from EBs stimulated with Bmp4 followed by activin A, bFGF and VEGF. Data are shown for EBs harvested at days 5, 6 and 7. All data shown are representative of at least three experiments.