Smelly Egg Gas Regulates Embryo Transport

Disruption of hydrogen sulphide signalling in pregnant mice leads to poor embryo transport to the uterus and may be the cause of ectopic pregnancies in humans.

AsianScientist (Jun 12, 2014) – Better known as the gas which causes the characteristic odor of rotten eggs, hydrogen sulphide (H2S) has now been shown to play an important role in regulating contractions of the fallopian tubes. Published in Nature Communications, these findings could help scientists address ectopic pregnancies.

Although hydrogen sulphide gas is toxic and corrosive when inhaled, in small amounts, it is used by the body as a signalling molecule. Hydrogen sulphide is produced from the amino acid L-cysteine in a reaction catalysed by the enzymes cystathionine-γ-lyase (CSE) and cystathionine-β-synthase (CBS), which have been found in both the male and the female reproductive system.

In males, hydrogen sulphide signalling is involved in processes such as erectile function, sperm production and sperm duct muscle relaxation. In females, it has been suggested that hydrogen sulphide plays a role in maintaining the uterus during pregnancy and acts as an oxygen sensor in the placenta. Led by Dr. Li Jingxin, scientists from Shandong University have now shown that CSE and CBS are also found in the lining of the fallopian tubes.

“We wanted to understand the role that hydrogen sulphide signalling was playing in the fallopian tubes,” Li told Asian Scientist Magazine.

The researchers showed that women who had ectopic pregnancies had higher amounts of CSE and CBS in their fallopian tissue, as well as increased hydrogen sulphide production compared to normal pregnancy. They also found that hydrogen sulphide is continuously produced in the fallopian tubes, where it relaxes muscle contraction.

When hydrogen sulphide signalling was chemically disrupted in pregnant mice, transport of the fertilized embryos through the fallopian tubes was delayed, thereby preventing their timely implantation in the uterus. Mice that were genetically deficient in CBS, therefore also lacking hydrogen sulphide signalling, had more embryos retained in the fallopian tubes.

“Our work shows that hydrogen sulphite signalling regulates muscle contractions of the fallopian tubes. Chemical or genetic modification of the hydrogen sulphite pathway results in the retention of fertilized embryos in the fallopian tubes of mice, a condition similar to ectopic pregnancy in humans,” Li said.

This study outlines a new regulatory mechanism for oviductal transport of embryos and early embryonic development. Moving forward, we plan to investigate the plasma levels of hydrogen sulphide in women with ectopic pregnancy. In the future, we hope that hydrogen sulphide can be used as a biomarker to predict ectopic pregnancy.”

The article can be found at: Ning et al. (2014) Dysregulation of Hydrogen Sulphide Metabolism Impairs Oviductal Transport of Embryos.

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Copyright: Asian Scientist Magazine; Photo: Li Jingxin/Shandong University.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Rebecca did her PhD at the National University of Singapore where she studied how macrophages integrate multiple signals from the toll-like receptor system. She was formerly the editor-in-chief of Asian Scientist Magazine.

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