Myeloid differentiation of human cord blood CD34+ cells during ex vivo expansion using thrombopoietin, flt3-ligand and or granulocyte-colony stimulating factor

We investigated the phenotypic changes of human umbilical cord blood (CB) CD34(+) cells during ex vivo expansion using thrombopoietin (TPO), flt3-ligand (FL), and/or granulocyte-colony stimulating factor (G-CSF). During ex vivo expansion of CD34(+) cells isolated from human CB for up to 5 weeks, surface expression of molecules on the cultured cells including CD64 (Fc gamma RI), CD32 (Fc gamma RII), CD16 (Fc gamma RIII), CD11b (MAC-1) and CD18 (beta(2)-integrin) was analysed by flow cytometry along with simultaneous measurement of apoptosis by 7-aminoactinomycin D staining method. CD64, CD32, and/or CD18 expressing cells appeared in the cultures both with and without the addition of G-CSF until the tenth day. However, without G-CSF. CD16(+) fractions did not appear and CD11b(+) fractions were not maintained. With G-CSF, the CD16(+) or CD11b(+) fractions appeared only from the second week. These results suggest that G-CSF is necessary for the late stage of myeloid maturation during which CD16 and CD11b are expressed.