Long term cryostorage of UC blood units: ability of the integral segment to confirm both identity and hematopoietic potential

Abstract

With the maturation of UC blood banking, cord blood (CB) units stored for years prior to use in transplantation present a new set of issues in clinical transplantation, including interval improvements in immune typing and confirmation of product identity and viability. A preliminary analysis of the transplants supported by the St Louis Cord Blood Bank, looking for an impact of length of CB storage time and transplant outcome was performed. We evaluated the utility of an integral segment containing an aliquot of cryopreserved product that has been exposed to the same post-processing storage conditions as the unit as a quality control tool for CB banking. Engraftment and survival following unrelated donor UC blood transplant were evaluated based on length of CB product storage at the St Louis Cord Blood Bank. A strategy of routine testing of the contiguous segment for high-resolution HLA typing (also confirming identity) and CFU analysis was tested in 283 consecutive CB searches. Comparison between CB unit and contiguous segment viability and hematopoietic potential was performed on 30 research CB units that had been stored up to 5 years. There was no statistical difference in engraftment or survival following unrelated donor cord blood transplant employing units banked < 1 year or > 3 years. Confirmatory HLA typing, CFU and viability testing was successfully performed from the same segment as part of a strategy for product release evaluation. When comparing the segment with its corresponding CB unit, the total colony-forming units (CFU) measured in the two was similar (P = 0.51, paired t-test). Three research units purposely sabotaged by an overnight thaw and refreeze had no CFU growth, but viability as measured by Trypan was still 68-98%. No deterioration of hematopoietic potential has been detected with storage up to 5 years. The contiguous segment CFU is representative of the product, and thus is a useful tool for quality control and confirmation of product viability. Viability, as measured by Trypan blue dye exclusion may be falsely reassuring.