Effect of dimethyl sulfoxide on post-thaw viability assessment of CD45+ and CD34+ cells of umbilical cord blood and mobilized peripheral blood

Background: The effect of dimethyl sulfoxide (Me2SO) on enumeration of post-thaw CD45(+) and CD34(+) cells of.umbilical cord blood (HPC-C) and mobilized peripheral blood (HPC-A) has not been systematically studied. Methods: Cells from leukapheresis products from multiple myeloma patients and umbilical cord blood cells were suspended in 1, 2, 5, or 10% Me2SO for 20 min at 22 degrees C. Cells suspended in Me2SO were then immediately assessed or assessed following removal of Me2SO. In other samples, cells were suspended in 10% Me2SO, cooled slowly to -60 degrees C, stored at <=-150 degrees C for >= 48 h, then thawed. The thawed cells in 10% Me2SO were diluted to 1, 2, 5, or 10% Me2SO, held for 20 min at 22 degrees C and then immediately assessed or assessed after the removal of Me2SO. CD34(+) cell viability was determined using a single platform flow cytometric absolute CD34(+) cell count technique incorporating 7-AAD. Results: The results indicate that after cryopreservation neither recovery of CD34(+) cells nor viability of CD45(+) and CD34(+) cells from both post-thaw HPC-A and HPC-C were a function of the concentration of Me2SO. Without cryopreservation, when Me2SO is present recovery and viability of HPC-C CD34(+) cells exposed to 10% Me2SO but not CD45(+) cells were significantly decreased. Removing Me2SO by centrifugation significantly decreased the viability and recovery of CD34(+) cells in both HPC-A and HPC-C before and after cryopreservation. Discussion: To reflect the actual number of CD45(+) cells and CD34(+) cells infused into a patient, these results indicate that removal of Me2SO for assessment of CD34(+) cell viability should only be performed if the HPC are infused after washing to remove Me2SO. (c) 2005 Elsevier Inc. All rights reserved.