Determination of growth factor requirement of EB-PE cells. (A) EB-PE cells grown with VEGF, IGF-1, and Epo were washed and plated at a density of 5 × 10⁴ cells/mL with various growth factors. The number of cells was counted daily for 4 days. Epo was used at 2 U/mL, KL at 10 ng/mL, bFGF at 10 ng/mL, VEGF at 5 ng/mL, and IGF-1 at 10 ng/mL. (B) EB-PE growth in various concentrations of bFGF. Cells grown with bFGF and Epo were washed and replated at 5 × 10⁴ cells/mL in different concentrations of bFGF and Epo. The number of cells were counted daily for 4 days. (C) EB-PE cells grown with bFGF and Epo were washed and replated at 3,000 cells/mL in various combinations of factors. Colonies were counted 5 days after the replating.