Effects of rapamycin on the proliferation, differentiation, and maturation of MKs. (A) Cell counts (± SD) in rapamycin (50nM) vs DMSO-treated (control) cultures of CB-MKs and PB-MKs. Rapamycin, added to the cultures starting on day 0, significantly reduced the cell counts in both CB-MK and PB-MK cultures, although the effect was somewhat more pronounced on CB-MKs. *P < .05; **P < .01. (B) Ploidy levels of rapamycin-treated versus control CB-MKs and PB-MKs as measured by flow cytometry. (C) Percentage of CD42b⁺ cells in rapamycin vs DMSO-treated CB-MKs and PB-MKs shown globally and classified by ploidy level. Bars represent the means ± SEM of 3 independent experiments. *P < .05. (D) Flow cytometric measurements of the MFI of CD42b staining among CB-MKs and PB-MKs cultured in the presence of rapamycin or DMSO classified by ploidy level. A representative result of 3 independent experiments is shown.