CD71 surface expression delineates distinct HSC-enriched subsets. (A) Representative FACS profiles showing percentage of CD45RA^loCD71^lo (red square) and CD45RA^loCD71^hi (blue square) subsets in CD34^hi expanded cells and the expression of HSCs markers CD90, EPCR, and ITGA3 in these populations after 7 days culture in presence of UM171 (35 nM). (B) Schematic representation of the experimental design to determine the impact of CD71 levels on HSPC activity in fresh and ex vivo cultured CB cells. (C) Representative FACS profiles showing percentage of CD34⁺CD45RA^lo, CD34⁺CD45RA^hi, and CD90⁺CD71^lo subsets in cultures initiated with total, CD71^lo, and CD71^hi sorted HSCs (CD34⁺CD38^loCD45RA^lo) populations and exposed to DMSO or UM171 (35 nM) for 7 days. (D) Cell lineage distribution in cultures initiated with total, CD71^lo, and CD71^hi sorted HSCs populations and exposed to DMSO or UM171 (35 nM) for 7 days. Bar graph showing total cell fold expansion (E) and absolute count of CD34^hiCD45RA^loCD90⁺EPCR⁺CD71^lo HSC subset (F) in the indicated group. Representative of 3 independent experiments (2-sided Mann-Whitney U test; ∗P < .05, ∗∗P < .01, and ∗∗∗P < .001). See also supplemental Figures 8 and 9.