Effects of long-term cryopreservation on hematopoietic progenitor cells inumbilical cord blood

There is considerable interest in developing banks of frozen umbilical cord blood cells for transplants but it is uncertain hew long frozen cells surv ive. Our objective was to determine the recovery of frozen umbilical cord b lood 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-12 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-de pendent recoveries, calculated by the formula d(k), (k = frozen storage int erval in years) were >90% at 10 years. We conclude that frozen cord blood c ells can be stored safely for prolonged intervals without substantial loss in hematopoietic progenitor cells.