Preserved in vivo reconstitution ability of PBSCs cryopreserved for a decade at -80 °C.

PBSC products for auto- and allografting can be cryopreserved in liquid nitrogen with controlled-rate freezing until their use. Alternatively, they can be stored at -80 °C in a mechanical chest freezer, but it remains to be clarified whether PBSCs can be stored for the long term. We evaluated viability and functions of PBSCs cryopreserved for more than 10 years with this simplified method. Although recovery rate and viability of CD34(+) cells were significantly decreased, myeloid differentiation potential and in vivo reconstitution and self-renewal potential of CD34(+) cells in a xenogeneic engraftment assay were maintained for more than 10 years. These results indicate that PBSCs can be stored at -80 °C for years. Although accumulation of clinical engraftment data is required to confirm our results, this simplified cryopreservation will thus meet the increasing worldwide demand for PBSC transplantation in a region with limited resources.