[Comparison of cryopreservation methods of umbilical hematopoietic stem/progenitor cells]

To compare the different effects of the programmable cell freezer and the -70 degrees C mechanical freezer in the preservation of the combilical cord blood and to study the effects of magnetic activated cell sorting on cell biologic characters.

After separating the nucleated cells from the umbilical blood by the density gradient separation method, we used cryoprotectant to protect the nucleated cells and preserve them by two methods; one was using the programmable cell freezer to cool the cells and finally putting them to the liquid nitrogen, and the other one was directly preserving the cells in a -70 degrees C mechanical freezer. The cells were thawed after a month and tested for the viability and clonogenic ability. Cell recovery, clonogenic capacity and clonogenic recovery by the two cryopreservation methods were compared. Meanwhile, the CD34+ cells were sorted by the method of magnetic cell sorting from the umbilical cord blood, and the cell purity and recovery after sorting were analyzed by the method of fluorescence-activated cell sorting.

There were no significant differences between the two preserving methods in cell viability, cell recovery, clonogenic capacity, or colony recovery. The purity of the CD34+ cells was 88.3% and the recovery rate was 46.2% after the cell sorting. The cell viability and clonogenic capacity of the CD34+ cells were much higher than those of the CD34- cells.

The umbilical cord blood can be efficiently preserved by the two methods and highly purified CD34+ cells could be obtained by using the method of magnetic cell sorting. The procedure of cell sorting doesn't affect the viability and clonogenic ability. The study provides some evidence for clinical application of preserving the umbilical cord blood and transplanting CD34+ cells.