Peripheral blood mononuclear cells (PBMCs) are used for many biomedical endeavors including therapeutic efforts, clinical trials, and basic research. In the therapeutic arena, they are valuable tools in the development of immunotherapy approaches. They also serve to support diagnostic medicine when used to identify biomarkers of disease.
Collection and storage conditions for PBMCs must promote their viability and utility for the various biomedical uses. Since it is often necessary to cryopreserve PBMCs prior to use, protocols and best practices have been developed to ensure the preservation of PBMC viability after cryopreservation. These practices include the storage of the cells at temperatures below −132 °C, the temperature at or below which all biological activity ceases [called the glass transition temperature of water (GTTW)].
However, there are a number of situations and conditions that often make it impossible to maintain PBMCs at these temperatures. When PBMCs are stored in freezers at or below the indicated temperature, temperature fluctuations can occur simply due to opening and retrieving substances from the freezer. Transportation between labs, clinics, and other facilities also affect storage temperatures. It is, therefore, important to know what effects these conditions may have on the utility and quality (not just viability) of PBMCs.
Scientists conducted research to determine the effects of 14 months of cryopreservation on PBMC gene expression. They measured the expression of genes involved in specific important stress-related cellular pathways. They studied PBMCs stored at -150°C and -80°C and compared the results between these storage conditions and with those of freshly obtained PBMCs. They also determined differences of PBMC viability using Trypan Blue staining and flow cytometry.
In addition to decreases in cell viability, the researchers observed effects on the PBMC transcriptome due to cryopreservation. Cells stored at -150°C had different gene expression patterns than those stored at -80°C. Also, the PBMCs that were stored at these temperatures had gene expression cycles different than those that were freshly collected. Genes were activated or suppressed based on the different storage temperatures. These results serve to identify possible biomarkers of PBMC quality after thawing and further demonstrate the importance of PBMC storage below the GTTW.
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Yang, Jun et al. "The Effects Of Storage Temperature On PBMC Gene Expression". https://bmcimmunol.biomedcentral.com/articles/10.1186/s12865-016-0144-1. N.p., 2017. Web. 26 Jan. 2017.