The regulatory interplay between miRNA and DNA methylation orchestrates vital ovarian functions and associated traits in PCOS

Polycystic ovary syndrome (PCOS) is the leading cause of amenorrhea and anovulatory infertility in women of reproductive age. Both gene polymorphisms and tissue-specific epigenetic alterations, which determine gene transcription and translation dynamics in disease-states, strongly influence PCOS development. Particularly, promoter-proximal DNA methylation and microRNA expression changes show strong associations with follicular defects, suggesting post-transcriptional dysregulation of localized gene networks. Our recent methylome study and other studies, posit DNA methylation as a regulator of microRNA expression in PCOS. Here, we identified microRNAs, potentially regulated by DNA methylation, and investigated whether their altered expression influences target gene expression in the PCOS ovary. Using granulosa cell samples of women with PCOS and age-BMI matched controls, we evaluated the transcript levels of 14 microRNAs participating in different ovarian processes and assessed their CpG-DNA methylation levels. For 9 of these microRNAs, which revealed differential methylation consistent with their gene hypomethylation or hypermethylation profiles, we evaluated the expression of their predicted, proteincoding target transcripts. Our data indicated that microRNA hypermethylation and decreased transcription of miR-10b-5p, miR-127-3p, miR-5189, miR-410-3p and miR23a-3p were consistent with the upregulation of PTEN, MMP13, OLR1, TET3 and APAF1 in PCOS. Conversely, microRNA hypomethylation and increased expression of miR-140-5p, miR-182-3p, miR-200b-5p and miR-3687 were consistent with downregulation of FZD6, LRP6, ZEB1 and LDLR. However, these observations need robust validations in larger study cohorts complemented with functional and mechanistic studies. Overall, our study indicates that altered microRNA expression as a consequence of DNA methylation changes, may contribute to metabolic and reproductive dysfunction in PCOS.