New Insights on Infertility and Low Success Rates of Assisted Reproduction in Women with Endometriosis

The immune microenvironment of the fluid surrounding immature eggs might be the culprit.

Key Points

Highlights:

• The immune microenvironment of the follicular fluid is altered in women with endometriosis.
• This may explain, at least in part, the rather low success rates in "in vitro fertilization (IVF)" among women with the disease.

Importance:

• This knowledge may help to develop new strategies to improve IVF outcomes in women with endometriosis. 

What's done here:

• Researchers measured the concentrations of 38 different cytokines in the follicular fluid and blood of women with and without endometriosis.

Key results:

• The levels of IL-4, IL-13, IL-3, and IL-1α were significantly higher in the follicular fluid of women with endometriosis. 
• The levels of IFN-γ, IL-17A, macrophage-derived chemokine and macrophage inflammatory protein-1α were decreased.
• Some changes were more marked with the severity of endometriosis. 

Limitations:

Researchers did not use laparoscopy to prove that women in the control group did not have endometriosis and at least some of them could in theory also have the disease, which may be the cause of their infertility.

Lay Summary

The fluid surrounding immature eggs waiting to mature and be fertilized by a sperm to lead to pregnancy is different in women with endometriosis compared to those without, according to a study published in Molecular Biology Reports. This could explain, at least in part, the low success rate of assisted reproductive techniques for couples in which the woman has endometriosis. 

The difference is at the level of cytokines, which are signaling molecules that different cells of the immune system use to communicate with each other. This finding is in agreement with endometriosis being a disorder of the immune system. 

The information brought to light in this study can help to develop new strategies to improve the outcomes of assisted reproductive techniques in patients with endometriosis.

It was already known that some cytokines, as well as other cell signaling molecules, are increased in the peritoneal fluid and blood of women with endometriosis. The peritoneal fluid is the liquid that is made in the abdominal cavity that lubricates the tissues and organs in the abdomen. An increase in cytokines usually suggests inflammation. 

In the present study, researchers at Zhejiang University in China analyzed the levels of different cytokines in the follicular fluid and blood of women undergoing in vitro fertilization (IVF). The follicular fluid is the fluid that fills the ovarian follicle that contains an immature egg. Once matured inside the ovarian follicle, the egg is released during ovulation and is ready to be fertilized by a sperm cell. 

The aim of the researchers was to identify factors related to endometriosis and to better understand the mechanisms underlying the disease. They measured the concentrations of 38 different cytokines in the follicular fluid and blood of 49 women undergoing IVF. Twenty of the women had severe endometriosis while 29 did not have the disease. 

They found that the levels of cytokines such as interleukins (IL) including IL-4, IL-13, IL-3, and IL-1α were significantly increased in the follicular fluid of women with endometriosis. On the other hand, levels of cytokines including IFN-γ, IL-17A, macrophage-derived chemokine, and macrophage inflammatory protein-1α were decreased compared to women without endometriosis.

The cytokines in the follicular fluid interact with each other to form a complex regulatory network that is important for the survival, maturation, and quality of egg cells. The composition of the follicular fluid, therefore, has a big impact on the outcome of assisted reproductive techniques such as IVF. 

These findings may help explain the low IVF success rates observed among women with endometriosis. The finding also provides a theoretical basis for the development of new strategies to improve IVF outcome in patients with endometriosis.

Research Source: https://www.ncbi.nlm.nih.gov/pubmed/31529342