Human Umbilical Cord Blood Hematopoietic Progenitors With High Proliferative and Replating Potential

To characterize the growth of cord blood progenitor cells, single nonadherent, low-density, T-lymphocyte-depleted CD34++’ cells were sorted by flow cytometer with an autoclone device into single wells containing culture medium and cytokines. These cells were evaluated for proliferation and for replating ability of their progeny. This latter effect is used as a measure of self-renewal capacity. Colony formation was assessed in 1 o wells containing various cytokines, alone and in combination, and single colonies deriving after 21 days in semisolid medium were replated into 2O wells in the presence of the combination of purified preparations of recombinant human steel factor (SF, a c-kit ligand), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), interleukin-3 (IL-3). and erythropoietin (Epo). Replating of single colonies was performed also for 3O. 4O. and 5O cultures. In the presence of serum, colony formation was observed in >66% of the wells stimulated with the combination of Epo, SF, GM-CSF, G-CSF, and IL-3, and more than 39% of the colonies formed in these lo wells were