Effects of sample processing and storage on the integrity of cell-free miRNAs in maternal plasma.

Background: Cell-free fetal miRNAs have been identified as potential biomarkers for fetal abnormalities and/or placental function. Factors affecting the stability of cell-free fetal miRNA samples (type of collection tube and time interval between sampling and analysis) have not previously been reported.

Methods: Blood from pregnant women (n = 12, 18 ± 4 weeks' gestation) was collected into two types of tube (EDTA and RNA BCT) and was stored at different temperatures for up to 72 h. Expression of seven apparently placental specific miRNAs was then measured to compare the effects of sampling and storage. These miRNAs were also assessed in non-pregnant women (n = 9).

Results: The quantity of miRNA extracted was not affected by time or tube. Three miRNAs (miR-518b, miR-525 and miR-526a*) were measureable only in pregnant women, but miR-518b was not always present. Detailed study of the two pregnancy specific miRNAs showed no effect of tube type at 4 h. However, variability in miRNA level was observed with increased time and was significant for one miRNA in the BCT tube at >48 h (p < 0.005).

Conclusion: Some cffmiRNAs are placental specific, and these samples are stable when analyzed within 48 h of collection in either tube type. © 2017 John Wiley & Sons, Ltd.