Influence of FL on ex vivo expansion of hematopoietic cells from cord blood in long-term liquid cultures.

The use of umbilical cord blood for stem cell transplantation has numerous advantages, but a major deficiency is the rather low cell number available. Therefore, ex vivo expansion were proposed to overcome this limitation. In this paper the effects of flt-3 ligand (FL), stem cell factor (SCF), interleukin(IL)-3, IL-6, granulocyte colony-stimulating factor (G-CSF) and granulocyte- monocyte colony-stimulating factor (GM-CSF) on long-term ex vivo expansion and differentiation of cord blood hematopoietic cells were investigated. In the culture containing FL + SCF + G-CSF + GM-CSF, the total cell expansion ratio reached the maximum (385.30 +/- 163.51-fold) at 28 days, whereas in the culture with FL + SCF + IL-3 + IL-6, CFU-GMs expansion ratio reached a plateau (409.52 +/- 189.50-fold) at 28 days. FL synergized with SCF and other cytokines. In all the conditions investigated, cultures with FL obtained an increase of fold expansion in both total cells and CFU-GMs. The combination of FL + SCF does not benefit the proliferation of the total cells, however, the expansion of CFU-GM was kept at a high level. Apparently, both cytokines maintained the activities of stem/progenitor cells and hampered differentiation. In the presence of G-CSF and GM-CSF, total cells enhanced quickly, and had the most expansion of total cells in comparison with other combinations. However, CFU-GM output peaked at 18 days and subsequently dropped to 0 promptly, suggesting that G-CSF and GM-CSF inspired differentiation.