Question: Can I store samples in a tissue storage solution?
Answer: Ideally, fresh samples maximize sample quality; however, some samples may need to be preserved for transportation, storage, or added flexibility in the single-cell workflow. Cryopreservation of cell suspensions is a commonly accepted method for long-term storage and transport, but cryopreservation or tissue dissociation may not be feasible at the collection site. Cell storage solutions are an attractive alternative that slows down sample degradation, only requiring 4C storage rather than cryopreservation capabilities.
Cells may be stored in a cell storage solution like in RPMI+10% FBS for a few hours. High cell viability and gene expression were conserved for up to 24hrs in tested cells (293T, 3T3, EL4, Jurkat, PBMCs). After 24hrs, cell viability can start to decrease, which can affect cell-type distribution. A decrease in transcriptomic mapping along with an increase in mitochondrial mapping was also observed. For cell storage >24hrs, cryopreservation of cells is recommended. See: Are there gene expression differences between fresh and frozen-thawed cells?
Tissue should be processed fresh if possible to maintain high cell viability and reduce the stress response. It may be possible to store tissue for a few hours or a few days in tissue storage solutions (MACS TSS, Hypothermosol) or media (RPMI). Storage in Hypothermosol FRS has been demonstrated for lung, spleen, and esophagus in the following publication: scRNA-seq assessment of the human lung, spleen, and esophagus tissue stability after cold preservation.
RNase-rich tissues like the spleen contain many enzymes and show decreased cell viability even at short storage times (24hrs). Usage of a storage solution is not recommended for such tissue types, processing fresh samples or flash-freezing the tissue is recommended to avoid sample degradation.
Best practices when using a sample storage solution:
- Be quick when transferring samples to the storage solution. Avoid having samples exposed for long periods of time
- Make sure sample is fully covered by storage media and no parts are exposed
- Transport on wet ice and minimize storage time as much as possible
- Sample transport time until processing has to be factored into storage time
Products: Single Cell Gene Expression