Outgrowth of erythroid progenitors from neonatal cord blood, human bone marrow, or peripheral blood. (A) CD34+cells isolated from neonatal cord blood were cultured in CFU-E medium complemented with Epo, SCF, IGF-I, and Dex (lower part). Cell density was kept at 1.5 to 3 × 106 cells/mL and total cell numbers were enumerated at the times indicated. At day 14 (arrowhead), immature low-density cells were purified from the mass culture using Percoll 1.072 g/mL and reseeded (top part). This procedure was repeated several times. (B) At day 8 (1), day 12 (2), and day 17 (3) after initiating the culture, cells were cytocentrifuged onto slides and stained with histochemical dyes plus a specific stain for hemoglobin that makes hemoglobinized cells appear dark in this figure.22 Numbers of panels correspond to numbered arrows in (A), indicating the time of aliquot removal. (C and D) Ficoll-purified cells from bone marrow (3 healthy donors) or from peripheral blood (5 untreated, healthy donors) were cultivated as described in the legend to (A) and cumulative cell numbers were calculated. In case of the peripheral blood-derived cells, apoptotic cells and lymphocytes were removed by centrifugation through Percoll 1.072 g/mL at days 4 and 6 of culture.
