HG/CD42b⁺MKs have characteristics of mature MKs. (A) Representative flow plots of CD42b expression on LG (green) and HG (red) MKs at specified time points of the differentiation. (B) Representative flow plots of Annexin V staining (left) and TUNEL staining (right) on day 14 MK cultures. (C) The percentage ± 1 SEM for each MK subpopulation at specified time points of the differentiation are shown of 4 independent studies. (D) Graph quantifying the percentages of MKs in each ploidy class ± 1 SEM of 5 independent studies. (E) Expression of α granule proteins (basic fibroblast growth factor [bFGF], vascular endothelial growth factor [VEGF], PF4, endostatin [Col18A]) and total RNA content of day 14 MKs was determined by intracellular staining and thiazole orange staining, respectively. Graphs quantifying the fold changes in mean fluorescence intensity over isotype/background ± 1 SEM are shown. (F) Day 14 MKs were stimulated with convulxin (500 ng/mL) or PAR-1–activating peptide (50 μM) for 20 minutes at room temperature. Representative flow plots showing percentages of activated (PAC-1⁺) MKs following convulxin stimulation (top). Black dotted line histogram indicates background staining in the absence of stimulation. Graph quantifying the percentages of PAC-1⁺ MKs following convulxin or PAR-1–activating peptide stimulation (bottom) (n = 5). *P < .05, **P < .01, ***P < .005, ****P < .001 for all statistical analyses shown.