A High Dose of Erythropoietin Induces the Expansion of CD34+CD133+ Cells in Human Umbilical Cord Blood.

Objectives: We compared the responsiveness to the high dose stimulation of human EPO between the transplant grafts in an in vitro culture system to clarify the characteristics of cord blood and to make clear the repopulation characteristics on human hematopoietic stem/progenitor cells.

Methods: Cells (cord blood, bone marrow and peripheral blood stem/progenitor cells) were cultured for six days with G-CSF (100 ng/ml), EPO (10 U/ml), or without additives, and were sorted with antihuman CD133-1 monoclonal antibody. The obtained fractions were further labeled with antihuman CD34 monoclonal antibody and CD133-2 antibody as well as the lineage markers, and their expressions were analyzed. Cells were also assayed with ordinal colony-formation. For the analysis of long-term culture-initiating cells (LTC-ICs), Dexter’s long-term culture method was carried out. The expression of the specific proteins was also analyzed with RT-PCR method.

Results. The ratio of the CD34+ cell count to the total cultured mononuclear cell count was not changed between CB, BM and PBSC. However, the ratio of the CD133+ cell count to the total cultured mononuclear cell count was 1.4-fold that of when CB cells were cultured with a high dose of EPO. No significance was observed for BM and PBSC. The count of CD34+CD133+ cells was 1.9-fold that of when CB was cultured with EPO. Dexter’s long-term culture system demonstrated that CB cultured with EPO contained more LTC-ICs and colony-forming cells with a high proliferation potential than that cultured without additives.

Discussion: These results indicate that the CB has unique characteristics to respond to a high dose of EPO.