CYTOKINE EFFECT ON EX-VIVO EXPANSION OF HEMATOPOIETIC STEM-CELLS FROMDIFFERENT HUMAN SOURCES

Human pluripotential stem cells (PSC) are currently the target for tra nsplantation attempts and genetic manipulation. We have therefore inve stigated the frequency and the expansion potential of PSC's in differe nt types of blood samples. CD 34(+) cells were thus obtained from huma n bone marrow (BM), as well as from peripheral blood (PB) and cord blo od (CB) samples. After immune-magnetic separation the highest yields o f CD 34(+) cells were from BM (1.08-2.25%) and CB (0.42-1.32%) while P B samples gave much lower values. Suspension cultures of PSC's from th e three sources were then set up, in the presence of combinations of h aemopoietic growth factors. A remarkable amplification of the nucleate d cell pool was observed reaching a maximum between 10 and 15 days of culture; earliest and maximum expansion (up to 220-fold) was achieved when Erythropoietin (Epo) was added to the culture medium, but this re sulted in reduction of colony-forming cells and differentiation into e rythroid progenitors. Clonogenic tests for BFU-E's derived colonies sh owed a peak value at 5 days of liquid culture. Further studies are adv isable to establish the best cytokine combination for a valuable ex vi vo expansion, coupled with preservation of stem cell properties.