Ex vivo expansion of umbilical cord blood hematopoietic progenitor cells by combinations of cytokines.

Ex vivo expansion of hematopoietic progenitor cells in the umbilical cord blood mononuclear cells (CB-MNC) was investigated in liquid culture system with various combinations of cytokines (stem cell factor [SCF], interleukin [IL]-3, IL-6, granulocyte-colony stimulating factor [G-CSF], erythropoietin [EPO], and interferon [INF]-γ). Non-lineage-committed hematopoietic progenitor cells and lineage committed hematopoietic progenitor cells were represented as CD34+CD38− and CD34+CD38+ subpopulations, respectively. Although absolute CD34+CD38− cell numbers decreased even in the presence of multicytokines, the combinations of SCF plus IL-6 and SCF plus IL-3 plus IL-6 plus INF-γ were significantly effective in maintaining CD34+CD38− cells than the other combinations (P < 0.05). After 4 weeks of culture, CD34+CD38− cells disappeared in all combinations of cytokines. Absolute CD34+CD38+ cell numbers increased in the presence of cytokines. Maximal expansion of CD34+CD38+ cells were observed in the combinations of SCF plus IL-3 plus IL-6 plus EPO (19.8 ± 3.3 -fold) and SCF plus IL-3 plus IL-6 plus G-CSF (18.3 ± 2.6). The combination of SCF plus IL-3 plus IL-6 was also effective to expand CD34+CD38+ cells (15.8 ± 3.9). However, the expansion was transient and they decreased to zero within 3 weeks. In the combinations of SCF plus IL-6 and SCF plus IL-3 plus IL-6 plus INF-γ, maximal expansion was inferior to the others but CD34+CD38+ cells were maintained more than 4 weeks. These results suggested that the indication of CBT can be expanded into older children by ex vivo augmentation of CB hematopoietic progenitor cells using multi-cytokines.