Intraindividual variation of microRNA expression levels in plasma and peripheral blood mononuclear cells and the associations of these levels with the pathogenesis of autoimmune thyroid diseases.

Abstract

microRNAs (miRNAs) circulate in the blood and negatively regulate the expression of mRNAs. Some miRNAs are associated with the development of autoimmune thyroid diseases (AITD); however, there are few reports on the association between miRNA expression and the pathogenesis of AITD or the physiological variations of circulating miRNAs, which are important to examine as biomarkers. We examined the circadian and day-to-day variations in the expression levels of 5 miRNAs (miR-125a, miR-146a, miR-155, let-7e and miR-106a) in plasma and peripheral blood mononuclear cells (PBMC). We also analysed the expression levels of two of these miRNAs (miR-146a and miR-155) in 20 healthy controls, 60 Graves' disease (GD) patients and 50 Hashimoto's disease (HD) patients. For each miRNA, we observed wide intraindividual variation [coefficient of variation value (CV): 70%-100%] compared to measurement error (CV: 20%-40%). In patients with AITD, HD, GD in remission and mild HD, the expression levels of miR-146a in PBMC were increased 296%, 328%, 348% and 464% above the levels in healthy controls, respectively (p=0.0443 and p=0.0273, p=0.0267 and p=0.0052, respectively). In severe HD, the expression level of miR-155 in plasma was increased to 347% of that in healthy controls (p=0.0256). The expression levels of miRNAs in plasma and PBMC showed wide intraindividual variation. In addition, miR-146a may be associated with the development of AITD.