Identification of small extracellular vesicle-linked miRNA specifically derived from intrafollicular cells in women with polycystic ovary syndrome

Research question: This study aimed to identify small extracellular vesicle (sEV)-linked microRNAs (miRNA) specifically derived from intrafollicular cells in women with polycystic ovary syndrome (PCOS) and to investigate their biological functions. Design: A total of 120 women were recruited from September 2017 to October 2018. To investigate miRNA profiles in sEV derived from follicular fluid and serum, 30 women with PCOS and 30 without PCOS were included for a miRNA microarray containing probes interrogating 2549 human miRNA. To study the expression levels of differentially expressed miRNA, sEV in follicular fluid obtained from another 30 PCOS and 30 non-PCOS patients were used for quantitative real-time polymerase chain reaction analysis. Results: A total of 281 sEV-linked miRNA specifically derived from intrafollicular cells were identified, 179 of which were expressed in both the PCOS and non-PCOS groups. Twenty-six of the 179 intrafollicle-specific sEV-linked miRNA were predicted to target 1537 genes. Functional analysis suggested that these genes were involved in pathways related to folliculogenesis, including the MAPK, and PI3K-Akt signalling pathways. Quantitative real-time polymerase chain reaction analysis showed that the expression of seven intrafollicle-specific sEV-linked miRNA was significantly higher in follicular fluid-derived sEV in women with PCOS than in women without it. These miRNA and their corresponding target genes were identified as being involved in the MAPK signalling pathway and oocyte meiosis. Conclusions: The data suggest that the aberrantly expressed miRNA and their target genes might be associated with PCOS, providing novel insights into the molecular mechanisms underlying regulation of folliculogenesis and oocyte maturation in PCOS.