The study used single-cell RNA
(ribonucleic acid) sequencing of human embryonic stem cell (hESC)-derived
contraction of the heart muscle cells (cardiomyocytes). For example,
intercellular communication was disrupted, cell survival was decreased, and
gene expression patterns were dysregulated.
The research team envisaged that this new
stem cell model will shed light on the effect of nicotine on the developing
human fetus, both at the organ level as well as at the individual cell level.
It is plausible that the new technology could be used for screening drugs and
environmental toxicants that could affect fetal development.
The study, published in Stem Cell Reports
, was led by Dr.
Joseph C. Wu, MD, PhD, Director, Stanford Cardiovascular Institute, Stanford
University School of Medicine, Stanford, California, USA.
Maternal Smoking and Risk of Birth Defects
Maternal smoking during pregnancy poses a high
risk to the developing fetus for developing birth defects and other
. These include miscarriage, stillbirth,
growth-restriction, premature delivery, and low birth weight. These can cause
long-term adverse effects such as cardiovascular, respiratory, metabolic,
endocrine, neurological, and psycho-behavioral complications after birth.
, the primary active
chemical constituent of tobacco smoke, is the main culprit for the increased
risk of birth defects
. Moreover, the recent introduction of new products
such as e-cigarettes has hampered the progress made so far, towards eliminating
tobacco products from the market.
Animal Studies on Nicotine Toxicity and its Limitations
Much work has already been done to investigate the negative effects of nicotine on fetal development
Animal models, especially rodent models, have been used for these experiments.
These animal studies have firmly established that nicotine is detrimental to
fetal development. However, since there are interspecies differences, it is
doubtful whether the animal results could to translatable to humans.
Conventional studies have evaluated nicotine toxicity in
human cells through bulk RNA sequencing. However, these studies failed to shed
any light on what was happening at the single-cell level due to nicotine
toxicity. As a result, there is limited understanding about the effects of
nicotine on human embryonic development at the cellular, sub-cellular and
How Did the New Study Overcome the Limitations?
The limitations of the animal studies were overcome by
utilizing single-cell RNA sequencing technology, which is a highly robust and
powerful tool for sequencing cellular RNA molecules. This sequencing technology
was used to analyze the effects of nicotine exposure for three weeks on the
transcriptomes (total RNA molecules in a cell) of 12,500 cells. These cells
arose from human hESC-derived embryoid bodies, which are 3-dimensional (3D) aggregations
of various types of pluripotent stem cells that are capable of giving rise to
various organs, such as the heart, liver, brain, and other organs.
What Did the New Study Find?
The study findings revealed that nicotine exhibited the
following effects at the cellular and molecular levels:
in cell survival
in size of the embryoid bodies
in formation and differentiation of embryoid bodies
in the levels of reactive oxygen species (ROS) that damage cells
of cell-to-cell communication
of gene expression patterns, which is implicated in the following:
contractility of cardiomyocytes
Plans are already underway to elucidate the underlying
molecular mechanisms of nicotine-induced fetal damage.
In this regard, Wu says: "We
hope this will lead to the discovery of novel biomarkers that can help doctors
better prevent, diagnose, and treat these diseases,"
He adds: "In addition, we plan to utilize our
hESC-derived embryoid body model and single-cell-sequencing technology to
investigate the wider effects of other harmful conditions such as air pollution
on human embryonic development."
The study validated the new technology for evaluating the
effects of drugs and environmental toxicants on human embryonic development.
What still remains to be done is replicate the entire body-physiology during
pregnancy in the hESC-derived embryoid body model.
The study highlights the fact that nicotine in e-cigarettes, nicotine gums,
and other nicotine products could have severe detrimental effects on the
developing human fetus.
With reference to the importance of the study, Wu says: "These results are especially important in
that they provide a scientific basis for educating the public, especially young
women, to keep away from smoking when they are pregnant or considering having a
The study was funded by the National Institutes of Health (NIH),
Bethesda, Maryland, USA.
- Single-Cell RNA Sequencing of Human Embryonic Stem Cell Differentiation Delineates Adverse Effects of Nicotine on Embryonic Development - (https://doi.org/10.1016/j.stemcr.2019.01.022)