Improving Storage Policy in Korean Public Cord Blood Banks: Comparison of Quality between Long-Term and Short-Term Storage of Cord Blood

Abstract

Background: The decreased use of cord blood units (CBU) due to improvements in haploidentical transplantation is a financial burden for public cord blood banks. Currently, there is no guidance regarding the length of cryopreservation of CBU in Korean public banks. The relative quality of long-term storage CB (LTCB) and short-term storage CB (STCB) needs to be evaluated to establish a storage policy. Methods: Thirty-four and thirty-one units of CB cryopreserved for less than one year and up to 14∼15.5 years, respectively, in the Busan Gyeongnam Public Cord Blood Bank were assessed. The total nucleated cells (TNCs), CD34+ cell counts, and colony-forming units-granulocyte monocyte (CFU-GM) were examined. The cell viabilities were evaluated by Eosin-Y exclusion staining and 7-aminoactinomycin D flow cytometry. The number of stored Korean public CB units from 2000 to 2016 was determined and categorized according to TNCs. Results: The post-thawing viability of the STCBs measured by flow cytometry was consistently higher than that of the LTCBs (TNCs, 62.5% vs 57.3%; MNCs, 93.1% vs 88.9%; CD34+ cells 95.7% vs 94.0%). The CD34+ cell viability was significantly higher in STCB (P=0.03). The CFU-GM after thawing was higher in STCBs (61.5±23.4 vs 49.9±22.8 [0.95 mm 2 ] P=0.05). Of the 48,161 CB units stored until 2016, Dec, 9,493 (19.7%), which were stored until 2006, had been stored for more than 10 years. Conclusion: LTCB with a low number of cells (＜0.7×10 9 cells) should be considered to exclude from storage for therapeutic purposes to improve the storage efficiency.