Viability of mononuclear cells in leukocyte concentrates at the stages of their preparation, freezing, and thawing

Abstract

Aim. To evaluate the viability of mononuclear cells (MNCs) in leukocyte concentrates (LCs) at the stages of their preparation, freezing, and thawing.Materials and methods. The study material included 44 LCs from donors of allogeneic hematopoietic stem cells (HSCs) and 189 autologous LCs from patients with oncohematological disorders. LCs were obtained from donors and patients by leukocytapheresis after mobilization of HSCs. LCs from patients were frozen with dimethyl sulfoxide (DMSO) used as a cryoprotectant at a final concentration of 5% and stored in liquid nitrogen. LCs were thawed before transplantation. A total of 161 LCs were immediately transfused to the recipient after thawing, and 28 LCs were washed from DMSO before transfusion. Flow cytofluorometry was used to determine the percentage of MNC populations that excluded 7-aminoactinomycin D (7-AAD).Results. The viability of peripheral blood MNCs in donors and patients was close to 100%. It was found that leukocytapheresis and cryopreservation with DMSO did not affect the viability of MNCs. The freezing of LCs with DMSO, storage in liquid nitrogen, and thawing resulted in a significant decrease in the content of viable MNCs (p = 0.0025), while no effect of LC storage duration on the viability of MNCs was revealed. Following DMSO removal from LCs, significantly more HSCs remained in a viable state than without washing (94.4 [94.5; 95.2] % vs. 86.7 [67.6; 92.9] %, (p = 0.0051); for other MNC populations, except monocytes, the differences in the viability index were also statistically significant.Conclusion. The viability of MNCs in LCs is recommended to be used as an independent characteristic of the transplant quality. In obtaining LCs and mixing them with the cryoprotectant DMSO, the viability of MNCs does not decrease, while in thawed LCs, it decreases significantly. Thawing of LCs with removal of DMSO allows to achieve the best viability of HSCs and most MNC populations.