We breathe them in, take them in with food or drink: nanoparticles enter our bodies in a variety of ways. However, the consequences of this are only partially understood. Now a study has revealed how nanoparticles affect unborn babies in the womb, even if they do not reach the embryo’s body. The accumulation of the tiny particles in the placenta is enough to disrupt its function. When exposed to nanoparticles, the organ releases messenger substances that, among other things, impair the formation of blood vessels in the embryo, as the researchers found. They are currently investigating what other indirect consequences there might be.
Whether titanium dioxide, diesel soot or the tiny particles of nanoplastics: many everyday products contain nanoparticles that give the substances color, stabilize them or make them more effective. Nanoparticles are also released through tire abrasion and other wear processes – and thus enter our environment. “We absorb these substances from the environment through our food, cosmetics or the air we breathe,” explains senior author Tina Bürki-Thurnherr from the Swiss Federal Laboratories for Materials Science and Technology Empa. Because of their small size, these nanoparticles can penetrate our organs, tissues and even cells, as studies have shown. They have been detected in intestinal cells, the lungs and the human brain, among other places. There they can cause cell damage and are suspected of promoting diseases such as cancer or Alzheimer’s.
View of the placenta
But what about the effect on particularly sensitive unborn children? Animal experiments raise the suspicion that high prenatal exposure to nanoparticles can affect the development of the embryo; lower birth weight, autism and respiratory diseases are among the possible consequences for the child. But the mechanisms by which this happens are unclear – also because some damage occurs without the nanoparticles being directly detectable in the tissue of the unborn child. “We already know that the placental barrier holds back many nanoparticles or at least delays their transport to the embryo,” explains Bürki. Bürki, lead author Battuja Dugershaw-Kurzerürich and their colleagues have now investigated how the accumulation of nanoparticles at the placental barrier affects the function of this organ, which is so important for fetal nutrition and health.
To do this, the team used fully functional human placentas that were made available after planned Caesarean sections. “Only thanks to human placental tissue can meaningful results on the transport and effect of nanoparticles be determined,” says Bürki. “The structure, metabolism and interlocking of maternal and fetal tissue are unique and species-specific.” For the experiment, the researchers exposed this placental tissue to various doses of titanium dioxide, silicon dioxide and diesel soot and analyzed whether this changed the release of messenger substances and other molecules from the placenta. It turned out that this was indeed the case. “Nanoparticles and diesel soot can cause far-reaching disturbances in the placental secretome, including the deregulation of various hormones, immune-active cytokines and chemokines as well as angiogenic growth factors,” reports the team. These effects were particularly evident in the metal oxide nanoparticles titanium dioxide and silicon dioxide and in placentas from early stages of pregnancy.
(Video: Empa)
Inhibited vessel formation
In a first step, Dugershaw-Kurzerürich and her colleagues tested how this altered messenger substance release affects the developing life using human vascular cells and cell cultures from umbilical cord blood. They exposed these cells to both normal placental secretions and those from the placenta samples contaminated with nanoparticles. The result: the cells that were exposed to the altered messenger substances from the nanoparticle-contaminated samples formed significantly shorter vein sprouts. A similar result was seen in a second test with chicken eggs and the embryos developing in them. Normally, the blood vessels in such eggs grow at a high speed and density and form a dense network of fine blood vessels on the inside of the eggshell. However, when these eggs were exposed to the messenger substance cocktail from the contaminated placentas, this vein network remained holey and coarse-meshed. According to the researchers, this proves that the disruptions in the release of messenger substances in the placenta caused by the nanoparticles also affect the embryos.
“Nanoparticles appear to have an indirect effect on the child in the womb by inhibiting the formation of blood vessels via messenger substances,” explains Bürki. Future analyses will now show what other disorders the nanoparticles can indirectly trigger. “A healthy placenta is of immense importance for the development of the child. Therefore, correct risk assessments of environmental pollution for pregnant women are crucial,” says co-author Thomas Rduch from the Women’s Clinic at the Cantonal Hospital of St. Gallen. It is therefore important to research the effects of nanoparticles on the placenta and thus indirectly on the embryo in more detail.
Source: Battuja Dugershaw-Kurzerürich (ETH Zurich) et al., Advanced Science, doi: 10.1002/advs.202401060