Hematopoietic repopulating ability of CD34⁺ progenitor cells ex vivo expanded with different cytokine combinations

Ex-vivo expansion technologies were developed for application of hematopoietic stem cells (HSCs) derived from cord blood (CB). The cytokine combination was essential to expand HSCs ex vivo and maintain the function of expanded HSCs. However the optimal cytokine combination was not determined. In this study, two combinations of cytokines were applied in ex-vivo expansion of HSCs to investigate the effect on the hematopoietic repopulating ability of expanded HSCs. CB CD34(+) cells were expanded with SCF + TPO + FL (STF) or SCF + TPO + FL + IL-3 + IL-6 (STF36) for 7 days and got 30.3 ± 6.4 and 39.8 ± 7.3 folds of total cells, respectively. The cells cultured by both STF and STF36 could engraft and repopulate in non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice effectively; however, the STF group achieved higher level of engraftment. These result demonstrated that the cytokine combination of STF36 favored the expansion of cells, while the cytokine combination of STF facilitated the engraftment and multi-lineage repopulating in vivo. These findings may have important implications for the cell therapy.