Low EPO environment enhances myeloid differentiation of UCB CD34⁺cells in vitro and in vivo. (A) Experimental design of in vitro experiment in which human UCB CD34⁺ cells migrate toward SDF-1 gradient in the presence of murine BM. The migrated human UCB and murine BM cells are collected and plated for CFU assay. (B) Number of migrated human UCB CD34⁺ cells in the presence or absence of EPO. (C) Images of types of CFU formed after plating migrated human UCB CD34⁺ cells and murine BM. Bright field images were taken at room temperature using an Olympus IX71 inverted microscope and Olympus DP71 camera. DP controller was used for software acquisition and Adobe Photoshop was used for image processing (scale bar represents 200 µm). (D) Genomic DNA polymerase chain reaction of 3 types of colonies appeared in methylcellulose medium confirming their human origin. (E) Relative percentage of total colonies formed in the presence of EPO compared with control conditions in the absence of EPO normalized to 100%. (F) Relative percentage of CFU-G/M and BFU-E colonies formed in the presence of EPO compared with control conditions in the absence of EPO normalized to 100%. (G) HBO, as an inducer of low EPO environment, effects on differentiation of transplanted UCB CD34⁺ cells. BM-isolated mononuclear cells from HBO (n = 3, done in duplicate) and non-HBO mice (n = 3, done in duplicate) 1 week after UCB CD34⁺ cell infusion were plated and counted. Ratio of BFU-E to total CFU and CFU-G/M to total CFU and in HBO and control mice. The asterisk (*) indicates statistical significance.