Single-Cell Transcriptomic Analysis Reveals Mitochondrial Dynamics in Oocytes of Patients With Polycystic Ovary Syndrome.

Lingbin Qi,Qiao Zeng,Zhigang Xue,Boxuan Liu,Xian Chen,Xiaoyu Xu,Qiwei Liu,Lu Wang,Wanqiong Li,Bo Lv,Jinfeng Xue

doi:10.3389/fgene.2020.00396

Abstract

Polycystic ovary syndrome (PCOS), characterized by polycystic ovarian morphology, ovarian follicular maturation arrest, and hormonal disorders, affects numerous women in the reproductive age worldwide. A recent study has found that mitochondria are likely to play an essential role in oocyte quality. However, it is still unclear whether oocyte development failure is associated with mitochondria in patients with PCOS. We analyzed the single-cell RNA sequencing data from the previous study, including data from 14 oocytes from 7 healthy fertile women and 20 oocytes from 9 patients with PCOS at the germinal vesicle (GV) stage, metaphase I (MI) stage, and metaphase II (MII) stage. We revealed the transcriptomic dynamics by weighted gene co-expression network analysis (WGCNA) and investigated the differences between stages using PCA and Deseq2 analyses to identify the differential expression genes (DEGs). Gene ontology (GO) was performed using clusterProfiler R package and Metascape. Our results indicated that specific gene modules were related to different stages of oocyte development using WGCNA. Functional enrichment analysis and gene co-expression network analysis found significant enrichment of the mitochondrial regulation genes at the GV stage. PCA (principal component analysis) and differential gene expression analysis suggested that GV was significantly different from the MI and MII stages between the two groups. Further analysis demonstrated that the upregulated differentially expressed genes at the GV stage of patients with PCOS mainly related to mitochondrial function, such as COX6B1, COX8A, COX4l1, and NDUFB9. Meanwhile, these genes tended to be activated at the MII stage in healthy cells, suggesting that some mitochondrial functions may be prematurely activated at the GV stage of PCOS oocytes, whereas this process occurs at the MII stage in healthy oocytes. Collectively, our study showed that aberrant mitochondrial function at the GV stage may contribute to a decline in oocyte quality of PCOS patients.

Highlights

Polycystic ovary syndrome (PCOS) is a common disorder affecting 5–20% of the women of reproductive age worldwide
Using Gene ontology (GO) enrichment analysis, we found that upregulated genes in germinal vesicle (GV) oocytes of patients with PCOS were highly related to mitochondrial energy metabolism (Figure 4B), while upregulated genes in the healthy samples were relevant to oocyte development (Figure 4C), suggesting the mitochondrial function abnormality is likely to be an important reason which lead to the difference between PCOS and healthy oocytes at GV stage
These results were confirmed using principal component analysis (PCA) and differential gene expression analysis, the transcriptomic profile was significantly different at GV stage suggesting that the differential expression genes (DEGs) at the GV stage are vital during the oocyte development process between women with PCOS and healthy women, and these DEGs are mainly related to mitochondrial functions

Summary

Introduction

Polycystic ovary syndrome (PCOS) is a common disorder affecting 5–20% of the women of reproductive age worldwide. PCOS is mainly characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovarian morphology (PCOM) (Azziz et al, 2016). The treatment strategies for PCOS mainly include medical treatment, ovarian surgery, and in vitro fertilization (IVF) therapy (Child et al, 2001; Harborne et al, 2003; Hendriks et al, 2007; Requena et al, 2008; Witchel et al, 2019). Women diagnosed with PCOS, who undergo IVF treatment, show a high probability for pregnancy and reach the mean level of the pregnancy rate (Nahuis et al, 2011). Besides the high risk of ovarian hyperstimulation syndrome and preeclampsia, oocyte amounts and quality obtained from patients with PCOS undergoing IVF are worse than those from healthy fertile women (Fauser et al, 2004; Ahmadi et al, 2013)

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Conclusion