Megakaryocyte and its progenitor from BM of OSMR^+/+ and OSMR^–/– mice. (A) The sections of femora from OMSR^+/+ and OSMR^–/– mice were stained with hematoxylin and eosin. (A) The number of mature megakaryocytes in 10 fields (original magnification, × 40) of femoral sections was counted. Error bars indicate mean ± SD, n = 3 of each genotype. (B) Megakaryocytic progenitors were assessed by liquid culture of BM. BM nucleated cells (100 000 cells) were incubated in IMDM containing 1% Nutridoma SP and TPO at 25 ng/mL in 96-well plate at 37°C supplemented with 5% CO₂ for 3 days. The number of mature megakaryocytes identified by AchE staining was counted (mean ± SD, n = 7 of each genotype). *P < .05 between wild-type and mutant mice.