Effect of cryopreservation on umbilical blood cells and its mechanism

Objective:To evaluate the effect of cryopreservation on clonogenic ability and apoptosis rate of mono-nuclear cells and CD34+ cells in umbilical blood(UB),and to choose the index to present the freezing injury and optimize the cryopreservation of UB. Methods:The mono-nuclear cells(MNC) and CD34+ cells were separated from UB and frozen.After 30 days,they were thawed in warm water.Clonogenic capacity and clonogenic recovery before and after the cryopreservation was compared.We also used Annexin V–FITC-PI to investigate the apoptosis rate of the cells before and after the cryopreservation of these 2 types of cells. Results:The number of colony forming unit-granulocyte/monocyte(CFU-GMs) was not changed after freezing and thawing in both MNCs and CD34+ cells,while the number of colony forming unit-granulocyte,erythrocyte,monocyte and megakaryocyte(CFU-GEMM) was obviously reduced after freezing in CD34+ cells.The 2 types of cryopreserved cells had certain degree of apoptosis before the cryopreservation.MNC-type cryopreservation increased the cells apoptosis a little,while CD34+-type cryopreservation increased more. Conclusion:The cells have certain degree of apoptosis before the cryopreservation.The freezing and thawing procedure does affect the early stage progenitor cells—CFU-GEMM in the CD34+-type cryopreserved cells in UB.The damage may be induced by the cell apoptosis.