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

Abstract

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 × 10⁶ CD34⁺ cells/kg and 33.04 × 10⁴ CFU-GM/kg. The median time to granulocyte (>0.5 × 10⁹/l) and platelet (>50 × 10⁹/l) 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.