Date Published: June 12, 2019
Publisher: Public Library of Science
Author(s): Yuta Matsuno, Takuya Kanke, Natsumi Maruyama, Wataru Fujii, Kunihiko Naito, Koji Sugiura, Y-h. Taguchi.
Extracellular vesicles such as exosomes contain several types of transcripts, including mRNAs and micro RNAs (miRNAs), and have emerged as important mediators of cell-to-cell communication. Exosome-like vesicles were identified in the ovarian follicles of several mammalian species. Although the miRNA contents have been extensively characterized, the detailed investigation of their mRNA profiles is lacking. Here, we characterize the mRNA profiles of exosome-like vesicles in ovarian follicles in a pig model. The mRNA contents of the exosome-like vesicles isolated from porcine follicular fluid were analyzed and compared with those from mural granulosa cells (MGCs) using the Illumina HiSeq platform. Bioinformatics studies suggested that the exosomal mRNAs are enriched in those encoding proteins involved in metabolic, phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) -protein kinase B (AKT), and mitogen-activated protein kinase (MAPK) pathways. While the mRNA profile of the exosome-like vesicles resembled that of MGCs, the vesicles contained mRNAs barely detectable in MGCs. Thus, while the majority of the vesicles are likely to be secreted from MGCs, some may originate from other cell types, including theca cells and oocytes, as well as the cells of non-ovarian organs/tissues. Therefore, the mRNA profiles unveiled several novel characteristics of the exosome-like vesicles in ovarian follicles.
Exosomes are lipid bilayer vesicles of around 40–200 nm diameter produced by most cell types . These vesicles contain several bioactive materials such as proteins, lipids, micro RNAs (miRNAs), and mRNAs with properties slightly different from their originating cells [2, 3]. Exosomes mediate cell-to-cell communication by transferring these molecules to target cells, wherein the transferred molecules may affect multiple biological processes [4–6]. Exosomes produced from several organs and tissues are readily detectable in the blood stream and may be considered as potential diagnostic markers of diseases such as cancers [7–9].
In this study, we performed the transcriptome analysis of the exosome-like vesicles in porcine ovarian follicles and focused on mRNA profiles. While the miRNA contents in exosome-like vesicles from ovarian follicles have been examined in detail [10, 16, 44–46], to the best of our knowledge, this is the first report to investigate the mRNA profiles of the exosome-like vesicles in ovarian follicles. The present analysis revealed that these vesicles contain various mRNAs which are enriched in those encoding ribosomal proteins. Moreover, bioinformatics analysis demonstrated that mRNA involved in the biological pathways known to important for normal follicular development were enriched in the exosome-like vesicles. While the majority of the vesicles are likely to be secreted from MGCs, some of these vesicles originated from non-ovarian organs/tissues. Therefore, the present study has unveiled several novel features of exosome-like vesicles in ovarian follicles by focusing on mRNA profiles.