Small RNA Transcriptomes of Two Types of Exosomes in Human Whole Salivadetermined by Next Generation Sequencing

Small non-coding RNAs, such as microRNAs (miRNAs), are involved in diverse processes, includingorgan development and tissue differentiation. Exosomes are small membrane vesicles (30–100 nm in diameter)produced by numerous cells. Recently, exosomes have been shown to contain miRNAs. However, thesmall RNAs contained in exosomes are not fully characterized. In a previous study, we found at least twotypes of salivary exosome that are different in size and have different proteomes. Studies of salivary exosomalsmall RNAs are limited to miRNAs. In this study, we examined small RNA transcriptomes using next generationsequencing technology to elucidate a full transcriptome set of small RNAs expressed in the two typesof salivary exosomes and in whole saliva (WS). Many types of small RNA, such as miRNA, piwi-interactingRNA (piRNA), small nucleolar RNA (snoRNA) and other small RNAs are contained in salivary exosomesand WS. Among these small RNAs we identified novel miRNA candidates.