P-331 Transcriptomic profiling of ovaries with experimental endometrioma in mice reveals the underlying mechanisms of abnormal oocyte quality and functions in endometrioma-associated infertility
Authors: Tan Z , Sze Wan H , Tao Z , Chi Chiu W 
Published: June 2023

Abstract

Study question
What are the underlying molecular mechanism and significant pathways mediated the endometrioma-associated infertility?

Summary answer
Significantly altered genes that participated in folliculogenesis, fibrosis, oxidative stress and inflammation are pivotal in the pathogenesis of infertility in endometrioma.

What is known already
Endometrioma (OMA) is the most common subtype of endometriosis, of which the endometriotic lesions implant in the ovary. Women with OMA are usually coupled with disrupted folliculogenesis, hampered ovulation, impaired oocyte quality, and undesired fertility outcomes. However, the underlying mechanisms of the disrupted folliculogenesis, hampered ovulation and impaired oocyte quality in OMA-associated infertility are still unclear. Next-generation sequencing (NGS) has been widely applied in whole-genome sequencing, RNA sequencing, and epigenomics. It is a promising technology that may provide full picture of the pathogenesis of infertility associated with OMA.

Study design, size, duration
An experimental mouse model of OMA was established in 4 weeks to study the effects of OMA on fertility outcomes and the underlying mechanism. Eight mice were included in experimental and sham control groups each. Half of the mice were then mated with male compeer and fertility outcomes were assessed after delivery. The other half were euthanized without mating to collect whole ovarian tissues for whole genome bulk RNA sequencing and then immunohistochemistry (IHC) validation.

Participants/materials, setting, methods
Minced uterine tissues from donor mice were inserted into ovarian bursa in recipient mice. After overnight mating, the pregnant mice were confirmed by positive vaginal plug. Live fetuses, abortion rate, and stillbirth were counted after delivery. Ovaries were either dissected to extract total RNA for sequencing, or paraffin-fixed and embedded for IHC, or superovulated to collect oocytes for counting and staining.

Main results and the role of chance
Successful establishment of endometriotic lesions in ovarian tissues was confirmed morphologically and histologically in recipient mice. The pregnancy rate was defined as the ratio of the number of pregnant mice to the total number of mated females. Compared to control group, a significantly decreased pregnancy rate was found in the OMA group. The average number and size of pups in the OMA group was significantly reduced. Meanwhile, abortion and stillbirth rates were significant higher in OMA group. Oocytes isolated from OMA ovaries had lower number than controls. Large proportion of the oocytes had significantly higher abnormal spindle rates, indicating mitotic disruption. A large proportion of the oocytes also had impaired cortical granule migration, indicating affected organelle organization. Furthermore, expression of follicle development markers (i.e. Forkhead box O3, anti-müllerian hormone, follicle-stimulating hormone receptor) were significantly decreased in OMA group. RNA sequencing identified several differentially expressed genes. The Gene Oncology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis demonstrated the dysregulation of signaling pathways associated with folliculogenesis, fibrosis, oxidative stress and inflammation, whichmight trigger OMA and lead to abnormal oocyte quality and functions in endometrioma-associated infertility.

Limitations, reasons for caution
Although ethical issue in human, studies based on this animal model may not reflect the exact situation in human. Moreover, future research is needed to understand the biological functions of differentially expressed pathways in the pathogenesis of OMA-related infertility. Furthermore, the manifestations in individual cells of ovaries are still unclear.

Wider implications of the findings
The results demonstrated that endometrioma remarkably deteriorated fecundity through several potential pathways. The underlying deteriorating effects and mechanisms might help to understand the biological and molecular mechanism and to develop novel therapeutic targets to improve fertility outcomes in women with endometrioma.

Trial registration number
not applicable