Cryopreservation of hematopoietic progenitor cells from apheresis at high cell concentrations does not impair the hematopoietic recovery after transplantation

Abstract

The high number of nuclear cells (NCs) from hematopoietic progenitor cells-apheresis (HPC-A) requires cryopreservation in large volumes or at high NC concentrations. The effect of NC concentration during cryopreservation has yet to be examined. In the experimental arm (n = 610, Protocol B), the first HPC-A sample from the patient was cryopreserved in two cryobags and subsequent collections in one cryobag, resulting in high NC concentrations (>100 x 10(6) NCs/mL) in most cases. The effect of NC concentrations at freezing in NC recovery after thawing and engraftment kinetics was analyzed and compared with a group of HPC-A cryopreserved at standard NC concentrations (n = 455, Protocol A). The mean (SD) NC concentration at freezing was 78 (28) x 10(6) per mL (median, 82 x 10(6)/mL; range, 12 x 10(6)-156 x 10(6)/mL) and 183 (108) x 10(6) per mL (median, 156 x 10(6)/mL; range, 16 x 10(6)-678 x 10(6)/mL), for HPC-A cryopreserved according to Protocols A and B, respectively. The NC viabilities of the test vials and HPC-A components after thawing were 88 percent versus 85 percent and 85 percent versus 82 percent, and the cloning efficiency was 49 percent versus 33 percent for Protocols A and B, respectively (p < 0.001). Significant differences were not observed in the recovery of NCs. Days to neutrophil and platelet engraftment were not different between patients transplanted in the standard- (n = 143) or high-cell-concentration group (n = 238). The cryopreservation of HPC-A at higher than standard NC concentrations has no adverse impact on hematopoietic reconstitution after transplantation.