Avoiding room temperature storage and delayed cryopreservation provide better postthaw potency in hematopoietic progenitor cell grafts

Abstract

Conditions for maintaining hematopoietic progenitor cells (HPCs) before cryopreservation remain controversial. An understanding of the impact of time and temperature during nonfrozen storage can contribute to the maintenance of the quality of products, improving transplantation outcomes. The objective of this study was to determine the influence on cell potency of thawed products from three sources of HPCs after prolonged storage at different temperatures before cryopreservation. Viable cell counts by flow cytometry and colony-forming unit (CFU) recoveries were assessed on cord blood (CB), mobilized peripheral blood stem cell (PBSC), and bone marrow (BM) samples over 72 hours using two different storage conditions, refrigerated (4-8°C) or room temperature (19-22°C). To determine the effects of delayed freezing on progenitor recoveries, paired samples were evaluated before and after cryopreservation. All samples maintained at refrigerated temperatures resulted in higher recoveries than those at room temperature in all variables assessed. Specifically, when assessing for CFU yields after thawing, the impact of time on BM resulted in a significant loss as soon as 24 hours (n = 10, 36.4 ± 28.0%, p = 0.003). This decrease was also observed for PBSCs and CB but at 48 hours of fresh storage (PBSCs n = 11, 32.7 ± 26.2%, p = 0.006; CB n = 10, 39.6 ± 26.4%, p = 0.001). Our data suggest that HPC products are better maintained at refrigerated temperatures before cryopreservation. Delaying cryopreservation should be minimized to avoid significant losses in cell potency.