Multipotency of Flk1+ CD34- progenitors derived from human fetal bone marrow

We report that a cell population derived from human fetal bone marrow, termed Flk1(+)CD34(-) multipotent stem cells, can differentiate not only into osteogenic, adipogenic, and endothelial lineages but also into hepatocyte-like cells and neural and erythroid cells at the single-cell level. We depleted mononuclear cells from fetal bone marrow of CD45(+), GlyA(+), and CD34(+) cells with the use of micromagnetic beads, then cultured them by limiting dilution. Three single colonies were harvested, expanded, and characterized. The clones have been expanded for more than 50 cell doublings, and cell-doubling time was about 30 hours. About 90% cells were in the G(0)/G(1) phase of the cell cycle, and the cells from the single colony maintained Flk1(+) and CD34(-). Because fetal bone marrow-derived Flk1(+) CD34(-)multipotent stem cells have the capacity for self-renewal and multilineage differentiation even after being expanded for more than 50 cell doublings, they may be an ideal source of stem cells for the treatment of inherited or degenerative diseases.