Female Sex Hormone Necessary but not Enough to Cause Endometriosis

Estrogen, that is known to be associated with endometriosis is not enough to cause the disease according to new research.

Key Points

Highlight:

• Estrogen is necessary but not enough to induce endometriosis.

Importance:

• This finding can help scientists better understand factors causing endometriosis and develop better treatments for the disease in the future.

What's done here:

• Using a mouse model, scientists transplanted endometrial tissue into the lining of the abdominal cavity, they then treated the animals with estrogen or not.
• They followed the newly transplanted tissue aiming at assessing the direct role of estrogen in the initial implantation and growth of endometrium in ectopic locations leading to endometriosis.
• Three group of mice composed of control (where the tissues from donor animals directly injected into recipients), donors were treated with estrogen prior to injection in to untreated control recipients or both recipients and donors were treated with estrogen were investigated.
• Effect of estrogen treatment on estrogen receptors in endometrium, or establishment of endometriosis lesions in terms of numbers and distribution at different time points were examined. 

Key results:

They’ve seen that in animals treated with estrogen the implantation rate of endometrial tissue was higher. However, the transplanted tissue died off within two weeks irrespective of estrogen treatment.

Limitations:

The results are based on experiments conducted on an animal model only and may not be the same in humans.

Lay Summary

Estrogen, the primary female sex hormone may be necessary but is not enough to induce endometriosis, found a study published in the Journal of Bioscience.  

This finding is important because it can help scientists better understand factors that cause endometriosis and design new approaches to treat it. 

It is known that estrogen is one of the factors that cause endometriosis. In order to better understand the role of this hormone in the development of the disease, researchers at the National Institute for Research in Reproductive Health, in Mumbai, India transplanted the tissue lining the inside of the womb known as the endometrium from one group of mice into the peritoneum, the membrane forming the lining of the abdominal cavity, of another group of mice. The endometrium was labeled fluorescent green in order to allow the scientists to differentiate it from the tissues of the receiving animals. The researchers did this in the presence and absence of the female sex hormone estrogen. 

They found that the rate of implantation of the endometrium was higher when estrogen was given to both the host and the donor animals. However, the lesion regressed within 14 days of treatment showing that this effect was not sustained.   

In both the animals that were treated with estrogen and those that were not, lesions were mostly established in the fat tissue of the peritoneum. However, these lesions did not have the typical features of the endometriosis such as the presence of glands, even after estrogen treatment. Importantly, the implanted tissue died off irrespective of whether or not the animals were treated with estrogen. 

The authors concluded that estrogen promotes the implantation of endometrial tissue but this tissue fails to grow even in the presence of high estrogen levels. “We propose that estrogen is necessary but not sufficient to sustain endometriosis,” they wrote.

Research Source: https://www.ncbi.nlm.nih.gov/pubmed/28569249