Eltrombopag stimulates megakaryopoietic progenitor cells in normal BM-MNC. (A) Total number of Mk colonies in the presence of increasing concentrations of Eltrombopag (n = 3). BM-MNC were seeded in semisolid collagen-based medium containing hrIL-3 and hrIL-6. Cultures were supplemented with either 0, 0.1, 1, 3, or 10 μg/mL Eltrombopag or 100 ng/mL hrTPO. Mk colonies were enumerated after 12 days of culture. (B) Differential colony count of Mk progenitor-derived colonies. Relative number of colonies from most immature bipotent Mk progenitors (□), immature Mk progenitors and precursors (), and mature Mk progenitor cells (■) are shown (see inset for colony morphology). Error bars indicate SD (n = 3). (C) Formation of non-Mk, myeloid colonies is not altered in the presence of Eltrombopag. BM-MNC were seeded in cytokine-supplemented methylcellulose medium. After 12 days of culture, CFU from granulocytic and monocytic progenitor cells (CFU-G, CFU-GM, CFU-M), erythrocytic progenitor cells (BFU-E, CFU-E), and granulocyte/erythrocyte/Mk/monocyte progenitor cells (CFU-EMM) were enumerated. Averages are shown. Error bars indicate SD (n = 3).