Hsa_circ_0043532 contributes to PCOS through upregulation of CYP19A1 by acting as a ceRNA for hsa-miR-1270

Polycystic ovarian syndrome (PCOS) accounts for about 75% of anovulatory infertility. The cause of PCOS is not clear. CircRNAs acting as miRNA sponges mediate the post-transcriptional regulation of multiple genes. CYP19A1 is a limiting enzyme in the ovarian steroidogenesis pathway. However, the mechanism of circRNAs regulating granulosa cell (GC) estradiol secretion in PCOS remains to be elucidated.

We identified that circ_0043532/miR-1270/CYP19A1 axis contributes to the aberrant steroidogenesis of GCs from patients with PCOS. This study broadens the spectrum of pathogenic factors of PCOS, and circ_0043532 might be a potential therapeutic target for PCOS.

Bioinformatics was used to predict the potential target miRNAs of circ_0043532 and target genes of miR-1270. Target miRNAs and mRNA expression were verified by qRT-PCR in GCs from 45 women with PCOS and 65 non-PCOS. Western blot, ELISA and dual-luciferase reporter assays were applied to confirm the substrate of miR-1270.

Circ_0043532 and CYP19A1 were significant up-regulation in GCs from patients with PCOS. The predicted target miRNAs of circ_0053432, miR-1270, miR-576-5p, miR-421 and miR-142-5p, were notably decreased in GCs from patients with PCOS. Mechanistic experiments showed that circ_0043532 specifically binds to miR-1270. MiR-1270 was negatively regulated by circ_0043532. Concomitantly, miR-1270 inhibited CYP19A1 expression and estradiol production, which could be reversed by circ_0043532 over-expression.