Effects of SDF-1 on platelet production. CD34⁺ cells were seeded in serum-free liquid culture containing SCF and PEG-rhuMGDF for up to 6 days. After two washes, SDF-1 was added at optimal concentration (500 ng/mL) in a second phase of the culture in the presence of increasing concentrations of PEG-rhuMGDF without any other factor (A) or in presence of an optimal concentration of SCF (25 ng/mL) (B). Conversely, platelet production was tested in the presence of an optimal concentration of PEG-rhuMGDF(10 ng/mL) and increasing concentrations of SCF (C). Six days after SDF-1 addition, platelet production was assessed by flow cytometry after anti-CD41a labeling. Cells from each culture condition without SDF-1 (white bar) and in presence of SDF-1 (black bar) were distributed in the same volume (400 μL), and for each sample the acquisition rate was 1 μL/s for 100 seconds. Data represent the mean for two experiments done in triplicate.