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

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 ± 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 × 10³, 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.