A new study has cast light on why some women with endometriosis experience infertility, with scientists saying the finding may lead to new treatment options.
Endometriosis is an inflammatory condition in which cells that usually form the lining of the uterus are present elsewhere, such as the ovaries, fallopian tubes, pelvis and rectum.
Its causes are unclear, but more than one in 10 women of reproductive age are thought to be living with endometriosis. Lena Dunham and Whoopi Goldberg are among the prominent figures who have spoken out about having the condition.
As well as causing chronic pain in some women, endometriosis can lead to other problems including infertility. “Around 10% of women have endometriosis and up to 50% of endometriosis patients have infertility,” said Prof Jae-Wook Jeong, co-author of the research from Michigan State University.
The reasons why only some women experience infertility are unclear. But now experts say they have shed light on what might be causing it, finding that it could be linked to a deficiency of a protein in the womb.
Writing in the journal Science Translational Medicine, scientists in the US and South Korea describe how they studied samples from 21 women with endometriosis and infertility, finding they had lower levels of a molecule called HDAC3 in the lining of the uterus compared with fertile women without endometriosis.
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HDAC3, said Jeong, is a type of molecule that is involved in controlling the levels of proteins that particular genes give rise to.
Further work in baboons and mice showed that when endometriosis was purposefully induced, levels of HDAC3 in the lining of the uterus also dropped.
The team produced mice without the gene necessary to produce HDAC3 in the uterus, and found the animals were sterile – apparently because the lining of the uterus did not undergo the changes expected in preparation for pregnancy, and had problems with the implantation of an embryo.
The animals also had increased levels of certain collagens – fibrous proteins – in the tissues of the uterus, a finding also seen in women with endometriosis. The authors say the collagens appear to hinder changes to the uterus needed for pregnancy.
Further work in human cells suggested HDAC3 acts on a range of genes to affect levels of proteins involved in processes necessary for implantation and preparation of the uterus for pregnancy.
Jeong said it was not yet clear whatwas behind the initial drop in HDAC3, but he said the research hinted at possible therapies to tackle the impact of a deficiency. Measuring HDAC3 levels, he said, might also help steer women with endometriosis to the most suitable fertility treatment.
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Dr Christian Becker, co-director of the Oxford Endometriosis Care Centre, welcomed the study but cautioned that the fertility tests were only carried out in mice, and that in both the mice and baboons endometriosis was induced rather than a spontaneous condition as seen in women.
Prof Andrew Horne from the MRC Centre for Reproductive Health at the University of Edinburgh said that while women with endometriosis could take longer to become pregnant than those without the condition, or be less likely to conceive, it did not mean infertility was a foregone conclusion.
“Endometriosis can be associated with difficulties becoming pregnant, but even women with severe endometriosis can still have a baby naturally,” he said.