Response of ECs to exogenous VEGF-A on OP9.

ES cell–derived VE-cadherin⁺ PECAM-1⁺ECs were induced, purified, and recultured on OP9. After 3 days of incubation, cultured ECs were stained by MoAb for VEGFR-2. (A-B) Round clusters of ECs were formed on OP9 stroma in the absence of exogenous factors. (C-D) Addition of 50 ng/mL exogenous VEGF-A resulted in dispersion of EC clusters. Scale bar, 200 μm. (E) Quantitation of the number of ECs before and after culture with or without addition of exogenous VEGF-A. To examine the recovery of sorted ECs in the presence or absence of exogenous VEGF-A, the number of ECs was calculated before and after culture using flow cytometry. Error bars indicate standard deviation of 3 independent assays.