Effect of MVs on primary CD34⁺ cell differentiation and colony formation. (A) CD34⁺ cells were purified from blood cord samples and incubated with either medium (control), or 5 μg/mL MVs generated from act D-treated (MV^Hh–) or PHA/PMA/act D-treated (MV^Hh+) CEM T cells, in the absence or in the presence of cyclopamine (cycl, 15 μM). After 6 days of exposure to MVs, cells were triple-stained and sorted on different fractions according to CD34, CD41, and CD42 expression analyzed by flow cytometry.³²  Three experiments yielding similar results were performed, values are expressed as mean ± SEM (bars). **P < .01, ***P < .001, significantly different from MV^Hh–-treated cells. (B) CD34⁺ cells were obtained as previously described and then incubated with either medium (control), or 5 μg/mL MV^Hh– or MV^Hh+, in the absence or in the presence of cyclopamine. Polyploidization of CD34⁺ cells was measured by flow cytometry. (C) CFU-GM and BFU-E colony formation from peripheral blood CD34⁺ cells. CD34⁺ cells were plated in methylcellulose in the presence of a combination of SCF, IL-6, IL-3, and erythropoietin (Epo) for 12 days. Colonies were scored under an inverted microscope. All results are expressed per 500 CD34⁺ cells.