P-604 Underlying molecular mechanisms of Polycystic Ovary Syndrome and Morphology: focusing on the ovary
Authors: Ramírez Martín N , Romeu M , Pellicer N , Martínez J , Buigues A , Peinado I , Pellicer A , Herraiz S 
Published: July 2024

Study question

What mechanisms are involved in the ovarian alterations of Polycystic Ovary Syndrome (PCOS) and Morphology?

Summary answer

PCOS patients associated a distinctive impairment of oxidative phosphorylation and dysregulated complement system in their follicular compartments not found in Polycystic Ovarian Morphology (PCOM) women.

What is known already

PCOS is a major cause of female infertility characterized by aberrant follicular development and hormonal imbalances leading to reproductive symptoms such as anovulation, poor oocyte quality, and hyperandrogenism. Likewise, PCOM is present in 16-25% of women with regular menses, but the clinical relevance of this ovarian phenotype and its correlation with PCOS remains unclear. Therefore, to establish the specific molecular mechanisms underlying the ovarian alterations in PCOS using High-throughput techniques will allow us to provide a better clinical management and a differential diagnosis with PCOM women.

Study design, size, duration

Cross-sectional molecular study including samples from 26 patients undergoing an IVF cycle between 2019-2022 at Hospital La Fe (Valencia, Spain). Eight women were considered PCOS, eleven PCOM and seven were control fertile patients. Granulosa cells (GCs) and follicular fluid (FF) samples were obtained during oocyte retrieval to perform RNA-seq and proteomic analysis, respectively.

Participants/materials, setting, methods

Women with two or more Rotterdam-criteria were considered as PCOS, while PCOM was defined by polycystic ovarian morphology on ultrasound with regular ovulatory cycles. RNA from GCs was obtained and sequenced using NextSeq500-Illumina to identify differentially expressed genes (DEGs) using DESeq2 (R-software). The proteome of FF samples was established by LC-MS/MS and differentially expressed proteins (DEPs) analyzed with limma package. Functional enrichment analysis of DEGs and DEPs (FDR&lt; 0.05) was performed based on KEGG database.

Main results and the role of chance

RNA-seq data revealed clear distinctions between GCs from PCOS and control women, with 526 DEGs. By contrast, the transcriptomes of PCOS and PCOM were more similar, with only 34 DEGs. Notably, oxidative phosphorylation emerged as the most enriched pathway in both comparisons, showing a differential expression in PCOS. Indeed, 6 out of 12 shared DEGs (MT-TP, MT-ND4L, MT-ND2, MT-ATP8, MT-ND4, and MT-ATP6), were mitochondrial genes found upregulated in PCOS vs. PCOM and control samples. These findings suggest that granulosa cells from PCOS present a dysregulation in oxidative phosphorylation, potentially linked to alterations in those genes associated with the mitochondrial electron transport chain.

The proteomic analysis showed 37 DEPs in the FF of PCOS compared with controls, being these DEPs mainly involved in the complement and coagulation cascades, PI3K-AKT pathway, oocyte meiosis and ferroptosis. Furthermore, the PCOS vs. PCOM analysis revealed 42 DEPs, significantly enriched also in complement and coagulation cascades, ferroptosis and glutathione metabolism. Interestingly, fifteen proteins were differentially expressed in both comparisons, with four of them related to the complement system (PROS1, C1S, C1QB and MASP2), suggesting that an alteration in this system at follicular fluid level might be one of the hallmarks of PCOS.

Limitations, reasons for caution

Further experimental studies are required to validate the specific changes identified in our study. Moreover, to establish how these alterations in the follicular compartments affect the oocytes of PCOS patients should also be explored.

Wider implications of the findings

Our study focused on specific mechanisms involved in PCOS ovarian alterations, providing new insights into potential biomarkers for an accurate diagnosis and management of this pathology. Dysregulations in oxidative phosphorylation and complement system might play a crucial role in PCOS multifactorial nature, contributing to impaired folliculogenesis and decreased oocyte quality.

Trial registration number

Not Applicable