Automated washing of long-term cryopreserved peripheral blood stem cells promotes cell viability and preserves CD34+ cell numbers

Peripheral blood stem cell (PBSC) transplantation has become an established treatment option for a range of malignant and inherited diseases. PBSCs are usually cryopreserved in the presence of dimethyl sulfoxide (DMSO) and stored in liquid nitrogen. However, cryopreservation and thawing of PBSCs may affect cell viability, resulting in delayed engraftment and other risks related to low stem cell numbers [1]. DMSO is commonly used at a concentration of 10% during freezing of PBSCs. However, DMSO itself is toxic and lowering doses of DMSO may have a favorable effect on hematopoietic recovery after transplantation [2, 3]. Generally, PBSCs are thawed and infused without removal of DMSO. This has been associated with a wide range of adverse effects (AEs), ranging from minor to severe life-threatening events [4, 5]. Although not all toxic events can be contributed to DMSO, grafts containing lower concentrations of DMSO typically display a reduced incidence of AEs [5, 6]. To decrease AEs and improve graft quality after thawing, it has been suggested to remove DMSO prior to transplantation [4, 7] using different washing systems [8, 9]. Here, we aimed to remove DMSO from long-term cryopreserved PBSCs using an automated, fully closed system and assessed effects on CD34+ stem cells, viability, and colony-forming capacity