Maturation of hESC-derived erythroid cells mimic erythroid development. (A) Expression of CD235a, a mature erythrocyte marker, increases with time; and CD71, an immature RBC marker, shows a decrease in expression over time. (B) Expression of β-globin chain in hESC-derived erythroid cells. Cytospin samples of hESC-derived erythroid cells collected from day17 and day 28 differentiation and maturation cultures were stained with human β-globin chain specific antibody. (C) Progressive maturation of hESC-derived erythroid cells in vitro. Progressive morphologic changes from blast cells to erythroblasts, and eventually matured erythrocytes are accompanied by significant increase of hemoglobin and decrease in size during their in vitro differentiation and maturation. Cells were stained with both Wright-Giemsa and benzidine (A,B: original magnification ×200).