Evaluation of the effect of cryopreservation on ex vivo expansion of hematopoietic progenitors from cord blood

In previous studies, we identified a cytokine cocktail including thrombopoi etin, Flt-3 ligand, interleukin (IL)-6 and IL-11 in serum-free medium, suit able to induce significant and sustained ex vivo expansion of primitive hem atopoietic stem cells (HSCs) from cord blood (CB) for up to 10 weeks. The a im of the present study was to evaluate the effects of cryopreservation on ex vivo expansion of HSCs and their committed progenitors. CD34(+) cells we re purified from CB units, each of which was processed in part as such and in part as cryopreserved and thawed, then expanded for 5 weeks in serum-fre e medium with the cytokine cocktail described above. We determined the numb er of nucleated cells (NC), CD34(+), CD34(+)/38(-)/33(-), CD34(+)/61(+), CD 61(+) cells and the clonogenic potential. After 2 weeks the median fold exp ansion of NC, CD34(+) and CD34(+)/38(-)/33(-) cells was around two log both with fresh and cryopreserved CB and the expansion continued similarly unti l week 5. Our data suggest that this serum free protocol induces similar ex vivo expansion of HSCs and their committed progenitors from both fresh and cryopreserved CB. Our findings can be useful in view of clinical applicati ons, since CB used for transplantation is stored in the cryopreserved state .