No Significant Difference between Plasma miRNAs and Plasma-Derived Exosomal miRNAs from Healthy People

BACKGROUND MicroRNAs (miRNAs) are small noncoding RNAs that are involved in many biological regulation processes. Studies have reported that miRNAs are enriched in human plasma and plasma-derived exosome as novel diagnostic biomarkers. The aim of this study was to determine whether the miRNA expression levels are different between plasma and plasma-derived exosome. METHODS We sequenced and quantified the miRNAs in plasma and exosome from healthy blood samples and validated three miRNAs in the two groups of lung cancer samples by qRT-PCR. RESULTS The sequencing results showed that only several of miRNAs were differential, while the qRT-PCR further validated that most of them did not have the consistent differences. However, the levels of two upregulated miRNAs (miR-181b-5p and miR-21-5p) in lung cancer were significantly higher in exosomes than plasma. CONCLUSIONS To the best of our knowledge, this study is the first to compare the expression levels of miRNAs between plasma and exosome in healthy blood samples. Our data suggested that the miRNA levels were similar in the two parts of the healthy people, whereas the two onco-miRNAs were significantly enriched in the exosome of lung cancer patients.