MkMPs promote Mk differentiation of CD34⁺ cells and HPCs. (A) Representative graph of flow cytometry ploidy analysis of cells from various coculture conditions at day 8. (i) CD34⁺ cells were cocultured with or without MkMPs starting at day 0. (ii) HPCs from day 3 culture without (top panel) or with (bottom panel) TPO were cocultured without or with MkMPs, and PMPs from day 3 to day 8. The same fraction of cells from each sample was analyzed. (B-C) At day 0, 60 000 CD34⁺ cells were cocultured with or without (vehicle control) MkMPs in a medium without TPO. The numbers (B) of total cells and Mks with 2N, 4N, and ≥ 8N ploidy were counted at day 8. Some Mks started to form PPTs at day 9 of coculture (C). Scale bar: 20 μm. (D-G) At day 3, 60 000 HPCs from culture with (D,F) or without (E,G) TPO were cultured in TPO-free medium with or without the addition of MkMPs or PMPs. Total cells (F-G) and Mks (D-E) with 2N, 4N, and ≥ 8N ploidy were counted at day 8. Error bars indicate SEM of 3∼4 biological replicates. *P < .01. ns, not significant.