What is the optimal timing and solution for the intravenous infusion of thawed cryopreserved mesenchymal stem cells?

Introduction: The viability of mesenchymal stem cells (MSCs) during intravenous infusion can significantly impact treatment efficacy, particularly with thawed cryopreserved MSCs. During infusion, these thawed MSCs are suspended in saline at room temperature, which lacks nutrients and buffering capacity, leading to a gradual decline in cell viability. This study aimed to investigate the survival of thawed MSCs during intravenous infusion and propose an optimal procedure to maximize cell viability. Methods: Human MSCs derived from adipose tissues (ADSCs) and umbilical cords (UCMSCs) were utilized in this study. The MSCs were cryopreserved using a cryoprotectant-free medium (MSCCryosave OTS) at -196°C at a concentration of 107 cells/mL. They were then naturally thawed at room temperature. The 15.107 thawed MSCs in MSCCryosave OTS were suspended in 500 mL Lactated Ringer solution. The bottle was connected to an infusion tube, with the valve opened at a rate of 25 drops/min. Cell viability was assessed every 30 minutes until the bags were depleted. In another experiment, cell viability was evaluated using a phosphate-buffered saline (PBS) solution supplemented with 5% human serum albumin (the solution named CellCarrier). Cell viability was determined using a hemocytometer with trypan blue staining. Results: The results indicated that the cell viability of thawed ADSCs and UCMSCs gradually decreased over time. For ADSCs, the percentage of viable cells decreased from 92.95 ± 1.33% post-thaw (at 0 h) to 80.41 ± 2.02% at 90 minutes of transfusion. For UCMSCs, the percentage decreased from 94.44 ± 1.69% post-thaw (at 0h) to 81.12 ± 2.26% at 90 minutes of transfusion. At the last drop of the bag, the percentage of viable ADSCs and UCMSCs was 48.22 ± 14.08% and 59.39 ± 14.54%, respectively, after approximately 385 minutes of transfusion. Notably, cell viability significantly increased when cells were infused with CellCarrier, remaining above 90% after 385 minutes (90.13 ± 0.24% for UCMSCs and 90.09 ± 0.44% for ADSCs). Conclusion: This study suggests that using Lactated Ringer's solution results in a rapid decline in cell viability. Therefore, reducing the transfusion time is crucial to maintaining cell viability before administration to patients. We recommend keeping the transfusion time under 90 minutes when using Lactated Ringer's or alternatively utilizing CellCarrier solution for infusion.