Upregulated Ribosomal Pathway Impairs Follicle Development in a Polycystic Ovary Syndrome Mouse Model: Findings of Differential Gene Expression Analysis of Oocytes

Background: Polycystic ovary syndrome (PCOS), a common endocrinal disorder, is associated with impaired oocyte development, which leads to infertility. However, the pathogenesis of PCOS has not been completely elucidated. Limited studies have analyzed the pathological characteristics of oocytes in PCOS. This study aimed to analyze the differentially expressed genes (DEGs) and epigenetic changes in the oocytes of the PCOS mouse model to identify the etiological factors.Methods: C57BL/6J female mice were subcutaneously injected with vehicle or 5α-dihydrotestosterone (250 µg/day) on days 16–18 of pregnancy. Female offspring were used as the control or PCOS group. The oocytes were collected from mice aged 7–9 weeks. The DEGs between the control and PCOS groups were analyzed using RNA sequencing (RNA-Seq). Additionally, the DNA methylation status was analyzed using the post-bisulfite adaptor tagging method. The ovarian tissue sections were stained with hematoxylin and eosin to examine the morphological changes. The proteins, Rps21 and Rpl36, were measured using immunostaining.Results: Compared with the control group, the PCOS group exhibited impaired estrous cycle and polycystic ovary-like morphology. RNA-Seq analysis revealed that 90 DEGs were upregulated and 27 DEGs were downregulated in the PCOS mouse model. DNA methylation analysis revealed 30 hypomethylated and 10 hypermethylated regions in the PCOS group. However, the DNA methylation status was not correlated with differential gene expression. The Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that five DEGs (Rps21, Rpl36, Rpl36a, Rpl37a, and Rpl22l1) were enriched in ribosome-related pathways. The immunohistochemical analysis revealed that the expression levels of Rps21 and Rpl36 were significantly upregulated in the PCOS mouse model.Conclusions: These results suggest that differential gene expression in the oocytes of the PCOS mouse model is related to impaired folliculogenesis. These findings improved our understanding of the pathogenesis of PCOS.