Colony-forming potential of hESCs and hiPSCs. EBs from hESCs (H1, HES2) and hiPSCs (MSC-iPS1) were harvested at the indicated times during hematopoietic cell commitment and myeloid cell expansion and colony forming potential was measured in methylcellulose cultures. (A) Quantification of the number of erythroid (Ery), macrophage (Mac), and myeloid colonies. Erythroid includes both pure erythroid colonies (> 90%) and mixed erythroid/myeloid colonies (< 10%). The majority of the myeloid colonies are mast cell colonies. Data represent the mean ± SEM of 6 to 8 cultures from 3 independent experiments. Values are presented as a percentage of total colonies, to demonstrate the emergence of macrophage progenitors with time during EB differentiation. We typically observe between 320 and 850 total colonies per 5 × 10⁴ cells at 2 weeks for all 3 cell lines, which increases to 490 to 1475 colonies per 5 × 10⁴ cells by 3 weeks. (B) Representative photographs of typical H1-derived colonies and cells within colonies after cytospin preparations. Images were acquired with a Zeiss Axioskop2 plus microscope using plan-Neofluar objectives and an Axiocam camera.