Is there an expiration date for a cord blood unit in storage

With improving expertise and supportive care, cord blood (CB) transplants are now associated with outcomes comparable to unrelated and sibling donor transplants.1 There is a need to increase the size and diversity of international CB inventories and to retain cryopreserved CB units for as long as safely possible. There are in vitro data supporting >90% recovery of hematopoietic progenitor cells from frozen CB cells stored for up to 12 years,2 and data showing that progenitor cell recoveries from short-term freeze samples ranging from 2 to 8 weeks are comparable to those cryopreserved for 10–15 years.3,4 Broxmeyer et al.5 reported adequate recovery (80–100%) of granulocyte–macrophage and multi-potential hematopoietic progenitors from functional CB units cryopreserved for up to 23.5 years as well as recovery of viable progenitor cells from CBs frozen for 15 years, which were able to generate CD45+ human cell engraftment when infused into sublethally irradiated NOD-SCID mice and were comparable to that reported with fresh CB.6 Despite this in vitro evidence, transplant physicians still remain concerned about the possible loss of integrity of frozen CB units associated with longer durations of storage.7 In one report, the incidence of bag breaks over a 6.5-year period was 3.5%, where 75% of the breaches occurred in units that had been cryopreserved for >2 years.7 Therefore, it is important to determine whether prolonged time of cryopreservation and storage may adversely affect clinical transplant outcomes, and with the new US Food and Drug Administration licensing regulations for CB units this question has become even more relevant: ‘is there an expiration date for CB unit in storage?’.