Quality of functional haematopoietic stem/progenitor cells from cryopreserved human umbilical cord blood

Background and Objectives Transplantation of cryopreserved umbilical cord blood (UCB) can be used to treat a multitude of haematologic and immunological diseases. In this study, we examined the quality of UCB cryopreserved for 2 (group I), 4 (group II) and 6 (group III) years. Methods The following parameters and procedures were used to test individual units of cryopreserved UCB: the number of total nucleated cells (TNC), cell viability, CFU-GM assay, T-cell activation in vitro and haematopoietic stem cell engraftment in NOD/SCID mice in vivo. Results The TNC recovery rates for groups I, II and III were 106.2 +/- 6.17%, 96.69 +/- d 6.39% and 100.38 +/- 5.27%, respectively, and the mean percentages of viable cells after thawing were 86.88%, 86.38% and 87.43%. When TNC were plated at 5 9 10 3, the number of CFU-GM was 13.6 (group I), 13.8 (group II), 14.2 (group III) and 14.7 (fresh UCB). We confirmed that the huCD4(+) and huCD8(+) T cells within cryopreserved UCB are functionally responsive by assessment of activated huCD25(+) cells. Moreover, the percentage of huCD45(+) cells in the bone marrow was 4.32 +/- 1.29% (group I), 4.48 +/- 1.11% (group II), 4.40% +/- 1.12% (group III) and 4.50% +/- 0.66% (fresh UCB), and that in the peripheral blood was 14.69 +/- 3.08% (group I), 15.24 +/- 4.05% (group II), 15.74 +/- 3.43% (group III) and 17.48 +/- 3.74% (fresh UCB) in NOD/SCID mice infused with isolated huCD34(+) cells. Conclusion These results indicated that cryopreserved UCB units efficiently retrieve in functionally competent form and are suitable for transplantation.