Cryopreservation and engraftment potential of peripheral blood stem cells: pediatric experience

Peripheral blood stem cells (PBSC) harvests were performed from children with various types of cancer in our institution. The PBSC was cryopreserved using the simplified method at -80 degrees C with 6% hydroxyethyl starch (HES) and 5% dimethyl sulfoxide (DMSO) without a programmed freezer. To determine the optimum cryo-storage time in this method, 33 samples harvested from 33 patients were investigated. While there was no correlation between the time of cryopreservation and the nucleated cell recovery rates, the CFU-GM recovery rate was negatively correlated with the cryopreservation times (p < 0.01). The CFU-GM recovery rate after 2, 3, and 5 years cryopreservation was 74%, 56%, and 21%, respectively. To date, 22 of the 33 children have subsequently received PBSCT using their cryopreserved cells. The number of infused CFU-GM of PBSCs was 6.9-114.6 (median 20.5) x 10(4)/kg. The cryopreservation time of infused PBSCs was 1-35 (median 4) months. After PBSCT, the absolute neutrophils count (ANC) achieved 500/mm3 between 8-16 (median 10.5) days, and the platelet count achieved 5.0 x 10(4)/mm3 between 13-200 (median 29) days. We have experienced PBSCT using PBSCs after 35 months cryopreservation as the maximum and successful engraftment. It has been clarified in this study that PBSCs could be clinically used successfully after 3 years cryopreservation.