Prior cryopreservation of ex vivo-expanded cord blood cells is not detrimental to engraftment as measured in the NOD-SCID mouse model

Cytokine-mediated expansion has been proposed and successfully used to faci litate engraftment post transplantation. This study examined whether cryopr eservation following expansion has a detrimental effect on the ability of c ells to engraft, using the NOD- SCID mouse model. Cord blood (CB) CD34(+) c ells were incubated for 7 days with stem cell factor (SCF), flt-3 ligand (F L), and megakaryocyte growth and development factor (MGDF). Expanded CD34() cells were transplanted into NOD-SCID mice either fresh or following cryo preservation and thawing. After thawing, recovery of nucleated cells was 94 %, of CD34 cells was 63%, and of day-14 progenitors was 17%. The loss of da y-14 progenitor cells among the thawed expanded cells did not influence the kinetics of human engraftment in the mouse. Bone marrow (BM) of mice trans planted with thawed expanded CD34(+) cells (14 +/- 3.9%) showed significant ly higher levels of human engraftment than mice transplanted with fresh exp anded CD34(+) cells (1.5 +/- 0.5%, p = 0.0064). Thawed expanded CD34(+) cel ls had significantly higher SCID Engrafting Potential (SEP) than freshly ex panded CD34(+) cells (p < 0.001). Results suggest that prior cryopreservati on does not prevent expanded cells engrafting in NOD-SCID mice.