A simplified method for cryopreservation of peripheral blood stem cells at -80 degrees C without rate-controlled freezing.

A simplified method was established for cryopreservation of peripheral blood stem cells (PBSCs) using hydroxyethyl starch (HES) and dimethylsulfoxide (DMSO) as a cryoprotective agent at -80 degrees C without rate-controlled freezing. The data indicate that a cryoprotective solution consisting of 6% HES and 5% DMSO produced the highest recovery rates for nucleated cells (92.0 +/- 3.5%), CFU-GM (73.8 +/- 4.1%) and BFU-E (82.2 +/- 6.9%), and the highest trypan blue viability (88.4 +/- 3.6%). For long-term cryopreservation of PBSCs, CFU-GM recovery rates remained almost unchanged during 5-18 months; the mean CFU-GM recovery rate after 18 months of cryopreservation was 70 +/- 11%. When large-scale samples of PBSCs in 100-ml freezing bags were cryopreserved for clinical use, cell and CFU-GM recoveries were similar. Using this method, 10 patients with hematological malignancy received PBSC transplants after marrow-ablative chemotherapy. All demonstrated early engraftment; seven are now alive in unmaintained complete remission for 3.5-15 months after PBSC transplant. This simple and inexpensive method will be useful for the wider application of PBSC transplant as a therapeutic alternative in the treatment of malignant diseases.