Distinct hemogenic properties of OP9 cell line. Induction of CD34⁺ expression (A) and CFCs (B) after 7 days of coculture of H1 hES cells on OP9, MS-5, and S17 bone marrow stromal cell lines. Results are mean ± SD of 3 experiments ± SD. (C) Morphology of differentiated hES cell colonies after 4 days of coculture with OP9, MS-5, and S17 cells. Images were captured with an inverted Leica DM1RB microscope (Leica Microsystems, Bannockburn, IL) using 5 × objective with numerical aperture 0.12 and acquired through Spot RT camera and Spot software (Diagnostic Instruments, Sterling Heights, MI).