Rapid freezing of umbilical cord blood in a -80 degrees C freezer

Lee, Jun Ah; Yoo, Keon Hee; Kim, Dong Hyun; Sung, Ki Woong; Jung, Hye Lim; Koo, Hong Hoe; Park, Quehn; Kim, Dae Won

Abstract

BACKGROUND
As the number of umbilical cord blood (UCB) transplants are increasing, well standardized processing of UCB units with high quality is needed. The aim of the study was to elucidate whether freezing of UCB units in a-80 degree (C) freezer is as efficient as in a programmed rate freezer. METHOD: UCBs were collected from normal full-term vaginal deliveries. After volume reduction, UCB units were split into two aliquots and freezed according to two different methods. One is rapid freezing (RF) in a -80 degree (C) freezer, and the other is slow freezing (SF) in a programmed rate freezer. After freezing, UCB cells were preserved in -196 degree (C) liquid nitrogen tank for 1 month. Cell viability, numbers of total nucleated cells (TNC), mononuclear cells (MNC), CD34+ cells, colony forming cells (CFC), long-term culture-initiating cells (LTC-IC) were evaluated before and after cryopreservation.
RESULTS
A total of 10 cases were evaluated. No significant differences in cryopreservation of proliferative potentials were found between two different freezing methods : viability (94% in RF vs 94% in SF), TNC (59% vs 61%), MNC (76% vs 63%), CD34+ cell (66% vs 71%), CFU-GM (79% vs 76%), and LTC-IC (69% vs 72%).
CONCLUSION
This was the first report of umbilical cord blood bank validating the recovery of proliferative potentials after cryopreservation in Korea. Present results were comparable to foreign reports, and good enough for clinical uses. Since freezing of hematopoietic stem cells of UCB in a -80 degree (C) freezer showed similar hematopoietic recoveries to programmed rate freezer, this simple and inexpensive method might be useful for wider application of cord blood transplantation.