Cytokine mediated expansion of human umbilical cord blood CD34+ cells: comparison of the use of partially purified and pure CD34+ target cells

To determine the optimal cell population for cytokine mediated expansion, we compared the use of Magnetic Cell Sorting (MACS) system enriched CD34+ human umbilical cord blood (HUCB) cells with that of MACS enriched, flow purified CD34+ HUCB cells. Both MACS enriched CD34+ cells and MACS enriched, flow purified CD34+ cells (mean starting purity of CD34+ SC 51.27 +/- 7.6% and 96.36 +/- 1.34% respectively n = 6) were incubated for seven days with Interleukin-1 (IL-1)+IL-3+Stem Cell Factor (SCF) and showed a fold increase in the number of nucleated cells (10.02 +/- 2.6 and 18.23 +/- 4.73 respectively) and a reduction in the percentage of CD34+ cells (5.55 +/- 1.23% and 12.21 +/- 3.29% respectively). An increase in the absolute numbers of CD34+ cells (4.8 x 10(4) +/- 2.3 x 10(4)) was observed with MACS enriched CD34+ cells as compared to no change (1.3 x 10(5) +/- 8.8 x 10(4)) with MACS enriched, flow purified CD34+ cells. An increase in IL-3+GM-CSF+SCF responsive colony forming unit (CFU) (1.7 x 10(4) +/- 9.4 x 10(3) and 1.6 x 10(5) +/- 7.7 x 10(4) respectively) was also observed as compared with input values (1.5 x 10(4) +/- 1 x 10(4) and 2.3 x 10(4) +/- 8.9 x 10(3) respectively). We conclude that MACS enriched, flow sorted CD34+ HUCB cells have greater cytokine mediated expansion potential as measured by progenitor expansion, than MACS enriched CD34+ HUCB cells.