Does ovarian endometriosis affect oocyte quality?

Single-cell RNA sequencing of oocyte reveals a differential transcriptomic profile associated with lower quality

Key Points

Highlight:

• Dr. Domínguez from Spain, by using single-cell RNA-sequencing, confirmed that the endometriosis has a global transcriptomic effect on oocytes.

Background:

• According to the various previous studies, the quality of the oocytes seems to be highly affected by the ovarian endometriosis and implantation rate is reduced when in embryos derived from endometriotic ovaries.
• Conflicting evidence, however, shows that there is no significant difference among oocyte and embryo quality and fertilization rates in women with endometriosis or not.
• Recently, RNA sequencing enables the whole transcriptome analysis in a single cell.
• In this study, by utilizing single-cell RNA-sequencing, Dr. Domínguez group tested if the endometriosis affects the quality of oocytes significantly or not.

Key points:

• The oocytes were collected from both healthy women and endometriosis patients, RNA was extracted, and single-cell sequencing was applied.
• The differentially expressed genes were found when endometriosis-affected oocytes were compared to oocytes from healthy donors.
• Based on the functional enrichment analysis, several biological functions were enriched such as steroid metabolism, response to oxidative stress and cell growth regulation.
• Also, mitochondrion, which is an important cellular component in oocyte development, was also significantly enriched.

Conclusions:

• By using the single-cell RNA-sequencing technique, this study confirmed that the endometriosis has a global transcriptomic effect on oocytes.
• Endometriosis significantly affects key biological processes in oocytes, such as steroid metabolism, response to oxidative stress and cell growth regulation.
• However, further studies would be necessary to confirm those results and develop a possible clinical diagnostic method of oocyte quality.

Lay Summary

Endometriosis is a very common gynecological disorder affecting women in their reproductive years. It is reported that patients with endometriosis have reduced implantation and pregnancy rates compared to healthy women. According to the various previous studies, the quality of the oocytes seems to be highly affected by the ovarian endometriosis.

Previous studies showed that the implantation rate was significantly reduced when people received embryos derived from endometriotic ovaries compared to the people received embryos from healthy donors. Interestingly, it is also shown that when oocytes are from healthy women, the implantation rate is similar to those recipients regardless of the presence of endometriosis. It was also claimed that the quality of oocytes from endometriosis-affected ovaries is decreased. The loss of cortical granule and zona pellucida hardening might interfere with the fertilization. Also, those affected oocytes have both a higher percentage of abnormal mitochondria and an overall lower number of mitochondria, affecting oocyte quality and fertilization. These findings indicate that endometriosis might affect oocytes quality significantly. On the other hand, conflicting reports suggest that there is no significant difference among oocyte and embryo quality and fertilization or implantation and pregnancy rates in women with endometriosis.

Authors of the current paper indicate that previous research lack in-depth molecular mechanisms. Global transcriptomics techniques are highly developed in recent years. RNA sequencing enables the whole transcriptome analysis even from single cells. Therefore, in this study, by utilizing single-cell RNA-sequencing, Dr. Domínguez group from Spain have decided to test if the endometriosis affects the quality of oocytes significantly or not. This finding recently published in the journal of “Human Reproduction”.

For the analysis, the oocytes were collected from both healthy women and endometriosis patients. After RNA was extracted, single-cell RNA-sequencing was applied. The differentially expressed genes were found when oocytes from women with endometriosis were compared to oocytes from healthy donors, the top twenty of them include the genes with biological functions affecting as steroid metabolism, oxidative stress, and cell growth regulation. Also, mitochondrion, which is an important cellular component in oocyte development, was also significantly altered.

In summary, the authors found that endometriosis has a global transcriptomic effect on oocytes by using single-cell RNA-sequencing. However, it seems that further studies still would be necessary to confirm those results and develop a possible clinical diagnostic method of oocyte quality.

Research Source: https://www.ncbi.nlm.nih.gov/pubmed/31211846