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The impact of storage at -80°C to cells varies depending on the cell type. Days to months’ storage will affect the post-thawing cell status, including viability, property, or gene expression. A standard 10% DMSO freezing medium is insufficient to protect the pluripotency of cells. Three days of storage at -80 °C might cause a 50% loss of live cells and a 90% loss of Oct-4 expression. If the cryopreservation lasts three months, the damage turns worse. There is still the opportunity to wait for the recovery of pluripotency after thawing. But even 14 days culture after thawing won’t lead to full recovery.
Researchers also make efforts to develop better protocols to improve the long-term cryopreservation at -80 °C. It was reported that 10% Ficoll 70 in the freezing medium might extend the iPSC storage at -80 °C to one year with comparable viability, plating efficiency, and pluripotent phenotype versus LN2 storage. The improvements have also been achieved in red blood cells and peripheral hematopoietic stem cells.
The two papers below may help you to learn more details about this topic.