Purification of Flk-1+ cells from iPS cells. A) Flk-1 expression profiles from 3.5 days to 7.5 days of cultivation as determined by flow cytometric analysis. (* p < 0.05 Day4.5 vs Day3.5, 5.5, 6.5 and 7.5). B) FACS analysis of pre and post MACS-sorted Flk-1+ cells at day 4.5. More than 99% of enriched cells were positive for Flk-1. Some of these purified Flk-1+ cells were positive for Nanog-GFP.