A novel role of follicular fluid exosomal miR-143-5p in polycystic ovary syndrome: targeting RASAL2 to drive granulosa cell proliferation.

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting women of reproductive age, in which abnormal follicular development is a major contributor to ovulatory dysfunction and infertility. Studies have shown that granulosa cell dysfunction underlies this aberrant follicular development. Within the follicular microenvironment, exosomes serve as crucial mediators of intercellular communication. Notably, exosomal non-coding RNAs (ncRNAs) are dysregulated in PCOS and have been implicated in its pathogenesis. Nevertheless, the precise mechanisms by which these exosomal ncRNAs influence abnormal follicular development in PCOS remain to be elucidated.

METHODS

A total of 40 PCOS patients and 45 non-PCOS controls undergoing in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) treatment were included in this study. Exosomes and mural granulosa cells (mGCs) of those patients were isolated from follicular fluid. Cumulus granulosa cells (cGCs) were separated from the cumulus-oocyte complexes (COCs). High-throughput miRNA sequencing were performed to analyze the expression profile of miRNAs in follicular fluid exosomes from 3 PCOS patients and 3 controls, and an additional 37 PCOS and 42 control samples were used for validation. The diagnostic potential of exosomal miR-143-5p for PCOS was evaluated using receiver operating characteristic (ROC) curve analysis, and its correlation with clinical parameters was examined. Quantitative real-time PCR was used to confirm miR-143-5p expression in exosomes and granulosa cells. Functional assays in primary mural GCs (mGCs) and KGN cells investigated the effects of exosomal miR-143-5p on granulosa cell proliferation. Bioinformatic analysis combined with dual-luciferase reporter assays were performed to validate the target gene of miR-143-5p. In vivo, a letrozole-induced PCOS rat model was established to investigate the role of miR-143-5p in the pathogenesis of the disease.

RESULTS

In this study, we identified exosomal miR-143-5p as significantly upregulated in follicular fluid from PCOS patients, in which it correlated with serum AMH levels and demonstrated strong diagnostic potential. Functional experiments in primary mGCs and KGN cells revealed that miR-143-5p promotes GC proliferation. Mechanistically, RASAL2 was identified and validated as a direct target of miR-143-5p. Exosomes derived from miR-143-5p-overexpressing cells enhanced recipient GC proliferation, confirming the role of exosomal mediation. In a letrozole-induced PCOS rat model, inhibition of miR-143-5p increased RASAL2 expression and ameliorated key pathological features, including ovarian weight, cystic follicle formation, and hormonal imbalances.

CONCLUSIONS

These findings reveal a novel exosomal miR-143-5p/RASAL2 pathway driving GC proliferation and ovarian dysfunction in PCOS, highlighting its potential as both a diagnostic biomarker and therapeutic target.