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 co ncentration of 10%. However, cells manipulated ex vivo may require more ref ined freezing protocols adapted to the specific cell suspension. In this re trospective study, we evaluated the results obtained with CD34(+) cells pur ified from peripheral blood of 39 patients on the CEPRATE SC System and fro zen 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 susp ension nor the nucleated cell density during freezing was predictive of cel l recovery. No difference was observed between cells stored in vials and ba gs. Thirty-seven patients transplanted with the concentrated CD34(+) fracti on 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) en graftment was 11 and 13 days, respectively. Only cell density and the infus ed number of CD34(+) cells and CFU-GM were significantly related to hematol ogical recovery. Our data suggest that purified CD34(+) cells can be succes sfully cryopreserved in 7.5% DMSO and may represent a first step in establi shing freezing parameters for selected CD34(+) cells.