That environmental pollutants can breach the placental barrier and affect foetuses is now well established in research. But how exactly does this happen? Finally, there is clarity on this question. Researchers at AIIMS Delhi have mapped the step-by-step biological pathway through which urban air pollution silences a key foetal growth protein, causing lasting harm to babies.
The ICMR-funded study, published in EMBO Molecular Medicine, has reportedly shown, for the first time, in comprehensive molecular detail ,how the fine particular matter from urban air pollution crosses the placenta, triggers a wave of inflammation and shuts down a protein that is essential for growth. This could have consequences right into late childhood.
The pollutants
What kind of urban pollutants cross the placental barrier? Particulate matter PM 2.5 and PM 10 are capable of this, and cause oxidative stress and inflammation, impairing the development of the foetus. Placental dysfunction, and complications including pre-term birth, low birth weight and preeclampsia are all possible outcomes.
“Since we know that pollutants do affect foetuses, our primary goal,” explains Subhradip Kamarkar, professor of biochemistry, AIIMS Delhi, and corresponding author for the paper, “was to examine the pathways that enable the pollutants to cause distress to the placenta and the foetus. While this has been studied before, it has been done in a piecemeal way. We showed the entire pathway.”
He further explains: “Our research reveals that exposure during pregnancy to Urban Particulate Matter activates inflammatory pathways that inhibit IGFBP3 expression, a key protein governing the equilibrium of the placenta and growth of the embryo. This reduction in IGFBP3 impairs critical placental processes, resulting in restricted foetal growth and altered developmental trajectories.”
What the research found
The research focused on both rodents and on delivery records of 994 women from two Indian cities, high-pollution Delhi and low-pollution Deoghar, Jharkhand. In women from Delhi PM2.5 exposure was identified as a significant risk factor for low birth weight. The rate of preeclampsia, a dangerous spike in blood pressure during pregnancy, significantly increases as pollution levels rise.
In the laboratory, among rodents, scientists showed how this happens. Particulate matter impaired the placenta’s ability to invade the uterine wall, form its essential nutrient-exchange layer, and support blood vessel growth. Pollution also triggered severe cellular stress and rewrote the cells’ epigenetic switches, permanently altering which genes are switched on or off, researchers on the study, including senior scientist Ruby Dhar and PhD students Isha Goel, Sunil Singh, said.
In pregnant rats, exposure to New Delhi’s pollution levels caused litter sizes to shrink by up to 25%, placentas to be smaller, and newborns to weigh 34% less at term. Offspring also showed clear neurological harm: impaired motor coordination, heightened anxiety, and stress responses; effects consistent with damage that begins before birth, the paper indicates.
“Crucially, these molecular disruptions have lasting consequences, as prenatally exposed rodents show persistent behavioral deficits after birth,” he says.
What next
Looking at the transgenerational effect, where researchers study the impact on development of motor development skills, IQ, cardio-vascular complications, cancer and metabolic disorders will entail further studies, Dr. Karmakar said.
He suggested that certain risk mitigation strategies such as wearing masks and eating foods rich in antioxidants could provide a buffer to people. “We must remember that risk mitigation in terms of controlling pollution will have to be multi-dimensional. These research findings call for pollution monitoring to be integrated into prenatal care,” Dr. Karmakar explained.
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