INSULIN-LIKE GROWTH-FACTOR-I (IGF-1) HAS A COSTIMULATORY EFFECT ON PROLIFERATION OF COMMITTED PROGENITORS DERIVED FROM HUMAN UMBILICAL-CORDCD34(+) CELLS

The effects of insulin-like growth factor-1 (IGF-1) on highly enriched human umbilical cord CD34(+) cells were investigated in vitro. CD34() cells were cultured in serum-free medium containing stem cell factor (SCF), GM-CSF, and interleukin-3 (IL-3), Culture of CD34(+) cells for one week in the presence of these cytokines resulted in a dose-depend ent increase in total cell number. Addition of G-CSF together with SCF +IL-3+GM-CSF increased the proliferation of myelopoietic cells as dete rmined by the number of cells expressing the myelomonocytic marker CD6 4 and the granulocytic marker CD15 without significantly altering the number of CD34(+) cells in the cultures. In the presence of G-CSF, IGF -1 induced a dose dependent increase in the total cell number and a mo derate but significant increase in the percentages of CD15(+), CD64(+) cells with sustained CD34(+) cell proliferation. We conclude that IGF -1 can enhance the in vitro proliferation of committed progenitor cell s derived from umbilical cord CD34(+) cells.