CLONOGENIC CAPACITY AND EX-VIVO EXPANSION POTENTIAL OF UMBILICAL-CORDBLOOD PROGENITOR CELLS ARE NOT IMPAIRED BY CRYOPRESERVATION

Umbilical cord blood (UCB) progenitor cells have been demonstrated to possess significant advantages over bone marrow (BM), in terms of prol iferative capacity and immunologic reactivity. Therefore, UCB has been recently considered an attractive potential alternative to BM as a so urce of hematopoietic progenitor cells for clinical applications. Sinc e several programs throughout the world are currently evaluating the f easibility of large-scale UCB banking for unrelated transplants, it wa s the aim of this study to evaluate whether cryopreservation procedure s might heavily impair the clonogenic capacity, the feasibility of CD3 4(+) selection and the ex vivo expansion potential of UCB progenitor c ells. UCB samples were collected and cryopreserved as unseparated (n = 21) or mononuclear (MNC) cells (n = 15) within 12 h from delivery, an d evaluated for viability, immunophenotype, cell and progenitor number s after a minimum stay in liquid nitrogen of 6 months (range 6-14 mont hs). Viability was always > 97% and no statistically significant diffe rence was detected by flow cytometric analysis. Clonogenic recovery fr om unseparated cells was 80-87% for HPP-CFC, CFU-GEMM, BFU-E and CFU-G M, and from MNC cells ranged from 82 to 91% for LTC-IC, CFU-GEMM,, BFU -E and CFU-GM. CD34(+) selection (n = 8) was performed on fresh and cr yopreserved MNC cells using the MiniMACS immunomagnetic separation dev ice, showing no difference in yield (68 +/- 7% vs 57 +/- 4%, P less th an or equal to 0.4) or in purity (89 +/- 2% vs 81 +/- 6%, less than or equal to 0.4), for fresh in comparison to cryopreserved MNC cells. Af ter 14 days of liquid culture in the presence of different combination s of SCP, IL-3, IL-6 and G-CSF no statistically significant difference was detected in CFC fold-expansion for fresh or cryopreserved MNC cel ls and for CD34(+) cells, either selected and cultured from fresh or c ryopreserved MNC cells. In conclusion we can state that UCB is a poten tial source of primitive progenitor cells that can be cryopreserved un manipulated or after physical separation without major losses in clono genic capacity and immunophenotypic composition. Moreover, CD34(+) sel ection from cryopreserved MNC cells is feasible and ex vivo expansion is not impaired. These results have important implications in the larg e scale UCB banking, in view of the potential applications of ex vivo expanded hematopoietic progenitor cells for the engraftment of adult p atients.