Quantification of residual dimethylsulfoxide after washing cryopreserved stem cells and thawing tissue grafts.

Dimethylsulfoxide (DMSO) is a cryoprotective substance often used to allow long term storage of stem cells or tissue grafts. However, a high frequency of adverse events is associated with the infusion of thawed cells. These events are in part due to DMSO, leading many cell therapy facilities to introduce a washing step before the delivery of the grafts. The lack of method for evaluating the residual quantities of this substance in the reinfused cells led us to develop a technique, based on capillary zone electrophoresis for assaying DMSO. The cryoprotectant was measured in 55 hematopoietic stem cell grafts, 6 parathyroids and 5 blood vessels immediately after thawing and after washing or bathing in a saline solution. The results showed that DMSO reduction in stem cell grafts reached more than 90% after the washing procedure. Furthermore, this study has shown that 2 washing steps significantly improved DMSO elimination as compared to 1 washing step. For parathyroids and blood vessels, bathing the tissues after thawing in a saline solution allowed more than 95% DMSO reduction. This study demonstrated that the technique of DMSO measurement used here, is simple and feasible on complex matrices such as protein samples after dilution. It is an appropriate method for residual quantification of the cryoprotectant before graft.