Cryopreserved cord blood mononuclear cells in DMSO are healthy for at least 6 hours after thawing

The impact of cryoprotectant exposure time on post-thaw viability of autologous and allogeneic hematopoietic stem cells and leukocyte subpopulations

Although the use of cryoprotectant dimethyl sulfoxide (DMSO) is the gold standard in cryopreservation of hematopoietic stem cells, it is well known that it has a negative effect on cell viability. The aim of this prospective study was to examine how the length of post-thaw exposure to DMSO affects the cell viability and stability of peripheral blood stem cell (PBSC) samples. Additionally, the effects of donor type and pre-cryopreservation storage time on post-thaw viability during the stability study were evaluated. In 30 autologous and 30 allogeneic PBSC samples viable CD34+, CD14+, CD19+, CD16+/56+, and CD3+ cells were determined immediately after thawing, and one-and three-hours post-thaw. Analysis of the absolute count of viable cells in thawed samples showed a significant difference between all measurement points for CD34+ (p < 0.001), CD14+ (p < 0.001), and CD19+ cells (p < 0.001). No significant differences were observed for post-thaw stability of allogeneic samples analysed between products stored before cryopreservation ≥ 24 hours (N = 20), and those stored < 24 hours (N = 10), except for viable CD3+/CD4+ cells after three hours post-thaw (p = 0.028). In conclusion, DMSO had different effects on leukocyte subpopulations in cryopre-served PBSC samples. The type of donors and the length of storage before cryopreservation did not affect the post-thaw stability of cryopreserved PBSC samples.

Role of flow cytometry in evaluation of the cellular therapy products used in haematopoietic stem cell transplantation

Cellular therapy nowadays includes various products from haematopoietic stem cells (HSC) collected from bone marrow, peripheral blood, and umbilical cord blood to more complex adoptive immune therapy for the treatment of malignant diseases, and gene therapy for inherited immune deficiencies. Broader utilization of cellular therapy requires extensive quality testing of these products that should fulfil the same requirements regarding composition, purity, and potency nevertheless they are manufactured in various centres. Technical improvements of the flow cytometers accompanied by the increased number of available reagents and fluorochromes used to conjugate monoclonal antibodies, enable detailed and precise insight into the function of the immune system and other areas of cell biology, and allows cell evaluation based on size, shape, and morphology or assessment of cell surface markers, as well as cell purity and viability, which greatly contributes to the development and progress of the cell therapy. The aim of this paper is to give an overview of the current use and challenges of flow cytometry analysis in quality assessment of cellular therapy products, with regard to basic principles of determining HSC and leukocyte subpopulation, assessment of cells viability and quality of thawed cryopreserved HSC as well as the importance of validation and quality control of flow cytometry methods according to good laboratory practice.