Serum miRNA Profiling in Asthma

Three miRNAs, viz. miRNA-106a-5p, miRNA-146a-5p and miRNA-19b-3p, were selected for the study based on miRNA profiling in PBMCs isolated from elderly and non-elderly asthma patients and healthy subjects. The profiling results and the outline of the study are briefly presented in the Additional file 1. From the miRNAs whose expression significantly differed in asthmatics and controls in the profiling study, we chose those that had been previously tested in serum and were related to the presence of asthma or its clinical features [15 (link), 20 (link)]. Additionally, although not shown as significant in the profiling results, miRNA-126a-5p was also included in the analysis, as many studies have reported it to have an important role in anti-inflammatory responses [20 (link)].
The miRNA was isolated from the serum using a miRCURY RNA Isolation Kit-Biofluids (Exiqon, Vedbaek, Denmark) according to the manufacturer's protocol. Equal volumes of RNA were used to prepare complementary DNA (cDNA) with the universal cDNA Synthesis Kit (Exiqon). They were used to perform quantitative PCR (StepOne Plus; Applied Biosystems, Foster City, CA, US) with miR-93 as a reference gene. Serum expression levels of miRNA-106a-5p, miRNA-146a-5p, miRNA-19b-3p and miRNA-126a-5p were evaluated with real-time PCR. miRNA expression is presented as 2^−ΔCT.