Exosomal circ_0008285 in follicle fluid regulates the lipid metabolism through the miR-4644/ LDLR axis in polycystic ovary syndrome.

PURPOSE: Exosomal circRNA, as an essential mediator of the follicular microenvironment, has been implicated in the etiological and pathobiological studies of polycystic ovarian syndrome (PCOS). This study aimed to determine abnormal circular RNA (circRNA) expression profiles in follicle fluid (FF) exosomes in patients with PCOS and identify the role of circ_0008285/microRNA (miR)-4644/low-density lipoprotein receptor (LDLR) axis in PCOS.

METHODS: Sixty-seven women undergoing IVF/ICSI, 31 PCOS patients and 36 non-PCOS patients were included in the cohort study. The circRNA expression profiles of FF exosomes in PCOS (n = 3) and control group (n = 3) were compared by RNA sequencing. In an additional cohort (PCOS:28 vs Control:33), the mRNA expression levels of four circRNAs from FF exosomes were further verified by qRT-PCR. Bioinformatic analysis and dual luciferase reporter gene assay verified the relationship between circ_0008285 and miR-4644 and between miR-4644 and LDLR. KGN cells were infected with sh-circ0008285 and transfected with miR-4644 mimic to verify their roles in lipid metabolism.

RESULTS: Four circRNAs showed significantly different expressions. Circ_0044234 was overexpressed in PCOS patients, while circ_0006877, circ_0013167 and circ0008285 were decreased in PCOS. Among four differentially expressed circRNAs, circ0008285 was enriched in lipoprotein particle receptor activity and cholesterol metabolism pathway by GO and KEGG pathway analyses. Luciferase assay confirmed the competing endogenous RNA (ceRNA) network circ_0008285/miR-4644 /LDLR. The intercellular experiments on circ_0008285 and its reduction in KGN cells showed that the consumption of circ_0008285 in exosomes could increase the expression of miR-4644 in recipient cells and inhibit the expression of LDLR, as well as increase free fatty acid secretion.

CONCLUSION: Circ_0008285 can combine with miR-4644 to promote the expression of LDLR and affect the cholesterol metabolism of ovarian granulosa cells in PCOS. Our findings revealed the ceRNA network of circ_0008285 and provided a new path to investigate lipid metabolism abnormalities in PCOS.