Effect of long-term plasma storage on the profile of circulating microRNAs

Aim . To assess the impact of long-term storage of biobanked plasma samples on the profile of circulating small non-coding ribonucleic acids (microRNAs). Material and methods . The study included paired plasma aliquots from 10 patients from the biobank collection of the National Medical Research Center for Therapy and Preventive Medicine. The control group consisted of microRNA samples isolated 1,5 years after plasma collection and then stored in aqueous solution for 3,5 years. In the long-term plasma storage group, microRNA was isolated from a second plasma aliquot after 5 years. All samples were stored at -70 оC. Se­quen­cing was performed for both groups simultaneously on the NextSeq 550 platform (Illumina, USA) using the High Output 1×75 bp protocol. Results. Principal component analysis based on human microRNA gene expression data (ENCODE v47) revealed heterogeneity between the study groups. In the long-term plasma storage group, compared to the control group, a significant decrease in library concentration and size was observed, as well as a more than twofold increase in expression levels for 31 microRNAs. Conclusion. Circulating microRNAs demonstrated higher stability du­ring storage in plasma than in aqueous solution. The obtained results in­di­cate the need to consider the storage time of isolated microRNA, along with other preanalytical factors, to improve the reproducibility of micro­RNA studies.