Effects of long-term cryopreservation on hematopoietic progenitor cells in umbilical cord blood.

There is considerable interest in developing banks of frozen umbilical cord blood cells for transplants but it is uncertain how long frozen cells survive. Our objective was to determine the recovery of frozen umbilical cord blood cells. We quantitated recovery of hematopoietic progenitor cells (CFU-GM, BFU-E, and CFU-GEMM) from frozen umbilical cord blood cells stored for up to 12 years. Decay rates of CFU-GM, BFU-E and CFU-GEMM (d, expressed as percent of viable cells recovered (95% confidence interval) were 0.9930 (0.9889-0.9970), 0.9840 (0.9769-0.9911) and 0.9817 (0.9707-0.9927). Time-dependent recoveries, calculated by the formula d(k), (k = frozen storage interval in years) were >90% at 10 years. We conclude that frozen cord blood cells can be stored safely for prolonged intervals without substantial loss in hematopoietic progenitor cells.