Vanillin, a chemical flavoring commonly used in e-cigarettes, may interfere with normal embryonic development in pregnant women who vape, according to research led by UC Riverside.
The findings, published August 12 in human reproductionoffer a possible explanation for previously observed links between vaping, difficulty getting pregnant, and miscarriage.
The study was done in the lab using human embryonic stem cells, which are similar to cells found in human embryos about three weeks into development, rather than in pregnant women. The researchers emphasize that, therefore, their results cannot demonstrate that the same effects occur in women or in developing embryos.
Try a common vaping flavoring
“There is little understanding of how vaping may affect embryo development in pregnant women who use e-cigarettes,” said Prue Talbot, a professor in the graduate division of UCR’s Department of Molecular Cell and Systems Biology, who led the study. “We conducted this study to determine whether vanillin, a flavoring chemical often used in e-cigarettes in high concentrations, could negatively affect the development of young embryos in humans.”
Talbot and his colleagues set out to investigate how chemicals found in vaping aerosols could influence early human development and what types of cellular damage could result.
“We focused on vanillin because it is frequently used in e-cigarette liquids, it is often used in high concentrations, and because we knew that embryonic cells had a channel called TRPV4 on their surfaces that would likely bind to vanillin,” Talbot said.
Talbot and co-author Shabnam Etemadi, a stem cell biologist and computational scientist at UCR, exposed human embryonic stem cells grown in laboratory dishes to various concentrations of vanillin. These included nanomolar (low) concentrations and micromolar (high) concentrations.
The researchers also tested the cells with a TRPV4 antagonist (a substance that inhibits the binding of vanillin to TRPV4), an antibody that blocks TRPV4 activity, and combinations of vanillin with the antagonist or antibody.
Vanillin changed the development of embryonic cells
Embryonic stem cells are pluripotent, meaning they can become virtually any type of cell in the body. During normal embryonic development, they give rise to three main cell types: endoderm, ectoderm and mesoderm.
“We found that micromolar concentrations tended to kill cells,” Talbot said. “The nanomolar concentrations caused the cells to lose pluripotency, which is the ability to develop into all types of cells. Vanillin also caused the stem cells to differentiate into endoderm, rather than ectoderm or mesoderm. Endoderm is an embryonic tissue that gives rise to the lining of the intestine and respiratory tissues. These changes are potentially very serious and could prevent normal development of embryos.”
The team found that blocking TRPV4 with the antagonist prevented vanillin from producing these effects. That result pointed to the TRPV4 channel as the mechanism through which vanillin affected cells.
“Our data predict that nanomolar concentrations of vanillin will reach the embryo in pregnant women who vape,” Talbot said. “At nanomolar concentrations, vanillin binds to a channel called TRPV4 on the surface of embryonic cells, allowing rapid influx of calcium, a signaling molecule. Calcium, in turn, activates downstream events that result in loss of pluripotency and differentiation of embryonic stem cells into endoderm.”
Why early cell development is important
Talbot noted that healthy embryonic development depends on stem cells forming the three primary cell types: endoderm, ectoderm and mesoderm.
If an embryo fails to form ectoderm, the nervous system will not develop, he said. Without mesoderm, many other tissues, including muscle, would also not form properly.
“Women don’t necessarily know the chemicals in vaping products,” Talbot said. “Our findings suggest that doctors should be cautious and advise against vaping during pregnancy, especially if they have trouble conceiving or experience miscarriages. “Regulatory policies are generally based on data derived from adults or adult cells. However, the prenatal stages of development are often the most sensitive to environmental chemicals.”
Researchers say regulators should consider requiring e-cigarette manufacturers to disclose ingredients on product packaging.
“When establishing policies for the use and distribution of e-cigarettes, it would be wise to consider whether and how the products harm the fetus,” Talbot said.
Researchers are testing other vaping chemicals
The team previously studied the menthol flavor in e-cigarettes and found that it contributed to respiratory illnesses in humans.
Researchers are now investigating WS-23, a synthetic cooling chemical frequently used in e-cigarette products. They are also examining how both menthol and WS-23 affect the differentiation of embryonic cells.
The researchers caution that the current study does not estimate the effects of repeated or cumulative exposure to vanillin over days, weeks, months, or years.
“The effect of long-term exposure could be greater,” Talbot said.
The research was supported by grants from the Tobacco-Related Disease Research Program and the California Institute for Regenerative Medicine, along with UCR Yvonne Danielson Graduate and Dissertation Completion Scholarship Awards.
The title of the article is “Nanomolar vanillin, an e-cigarette flavoring, appears to alter pluripotency and promote endodermal differentiation in human embryonic stem cells through activation of TRPV4.”