Research Reveals How Pollutants Affect Early Embryo Development

Source: The Francis Crick Institute

Summary: A new research suggests, chemicals released in cigarette smoke, factories and incinerators may interfere with the early stages of embryo development.

Researchers at The Francis Crick Institute investigated the effects of chemicals which activate the aryl hydrocarbon receptor – AhR (a protein; ligand-activated transcription factor) in mouse stem cells and embryos. Generally, this receptor is switched on and off by natural processes in the body, but the production of aryl hydrocarbons by incomplete combustion or industrial processes can keep it switched on. The exposure of pregnant mice to synthetic aryl hydrocarbons affected the development of early embryos. Embryo development problems lead to miscarriage and stillbirth. Till now the molecular mechanism where such chemicals affect the development was not known. The study was published in the journal Stem Cell Reports. 

Early embryo development

Photomicrographs of representative mouse embryos from each genotype and their respective placentae from 3-MC-treated pregnant females. A fully developed and an undeveloped Ahr+/− mouse are shown; all Ahr−/− mice developed normally. Credit: The Francis Crick Institute

Early embryonic development is tightly regulated by a well defined transcriptional program which helps in the controlled expression of differentiation genes at the appropriate time and sustains their pluripotent identity. The researchers analyzed embryonic stem cells and embryos at different developmental stages found that the chemicals, aryl hydrocarbons will affect the fundamental transcription program. AhR plays a significant role in human health. The aryl hydrocarbons found in nature and its synthetic forms (dioxins) which are not metabolized can stay in the human body for a long time causing serious damage. These findings identify a mechanism which allows environmental factors to disturb embryonic development through aryl hydrocarbon receptor signaling.

Dr. Brigitta Stockinger, a senior author said, “We already know that AhR acts as a vital control centre to maintain our immune defences, particularly in our intestines, lungs and skin. This latest study builds on our knowledge and shows that exposure of stem cells to AhR activation, particularly if prolonged and non-physiological, plays a detrimental role in the earliest days of embryo development. We are now looking at the consequences of transient AhR activation by physiological ligands compared with prolonged activation by chemicals that are difficult to metabolise.”

More Information: Manolis Gialitakis et al. “Activation of the Aryl Hydrocarbon Receptor Interferes with Early Embryonic Development”, Stem Cell Reports (2017). DOI: 10.1016/j.stemcr.2017.09.025

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