Successful cryopreservation of purified autologous CD34+ cells:: influence of freezing parameters on cell recovery and engraftment

Conventional hematopoietic stem cell cryopreservation methods use a DMSO concentration of 10%. However, cells manipulated ex vivo may require more refined freezing protocols adapted to the specific cell suspension. In this retrospective study, we evaluated the results obtained with CD34(+) cells purified from peripheral blood of 39 patients on the CEPRATE SC System and frozen in 7.5% DMSO with a view to transplantation. The post-freezing recovery of progenitor cells was 89.4 +/- 27.87% for CD34(+) cells, 59.13 +/- 36.93% for CFU-GM, and 53.49 +/- 40.71 for BFU-E, Neither the purity of the suspension nor the nucleated cell density during freezing was predictive of cell recovery. No difference was observed between cells stored in vials and bags. Thirty-seven patients transplanted with the concentrated CD34(+) fraction received 4.46 x 10(6) CD34(+) cells/kg and 33.04 x 10(4) CFU-GM/kg, The median time to granulocyte (>0.5 x 10(9)/l) and platelet (>50 x 10(9)/1) engraftment was 11 and 13 days, respectively. Only cell density and the infused number of CD34(+) cells and CFU-GM were significantly related to hematological recovery. Our data suggest that purified CD34(+) cells can be successfully cryopreserved in 7.5% DMSO and may represent a first step in establishing freezing parameters for selected CD34(+) cells.