An eight-fold ex vivo expansion of long-term culture-initiating cells from umbilical cord blood in stirred suspension cultures.

Simultaneous ex vivo expansion of different progenitor cell types may be beneficial for cord blood (CB) transplantation, to overcome a potential limitation due to restricted cell numbers. Therefore, 1.5 x 10(6) CD34+ cells isolated from fresh or thawed CB samples were inoculated in a large-scale stirred suspension bioreactor and cultured in the presence of Flt3-L, SCF and IL-3. At days 0, 7, 10, 14, 21 and 28, the spinner cultures were analyzed for viable cells, colony-forming cells (CFC), including erythroid burst-forming unit (BFU-E), granulocyte-macrophage colony-forming unit (CFU-GM) and granulocyte-erythrocyte-megakaryocyte-monocyte colony-forming unit (CFU-GEMM) as well as long-term culture-initiating cells (LTC-IC). Expansion of thawed CD34+ cells resulted in a substantial amplification of total cells (maximal at day 28: 154 +/- 132-fold), CFC (maximal at day 14: 45 +/- 36-fold), CFU-GM (maximal at day 14: 88 +/- 85-fold), CFU-GEMM (maximal at day 7: 4 +/- 2-fold) and of LTC-IC (maximal at day 10: 8 +/- 3-fold). There was no significant difference between fresh and thawed CD34+ cells. These results demonstrate that simultaneously committed progenitors as well as the more immature CFU-GEMM and LTC-IC can be substantially amplified from CD34+-enriched CB samples in large-scale stirred suspension cultures within 7-14 days without exhausting the proliferative potential and, thus, it may be possible to improve CB transplantation by ex vivo generated cells.