Virus-Blocking Placental Cells May Stop Infections Outside of Pregnancy
A new study reveals that placental cells may help prevent viruses from crossing from an expectant mother to her baby. Researchers believe these cells can also transfer their unique trait to other kinds of cells.
Researchers said the latest findings, published in the early online version of the Proceedings of the National Academy of Sciences, may provide new insight into the how the placenta works and can be used to help develop new treatments against viral infections during pregnancy.
Co-senior investigator Dr. Yoel Sadovsky, professor of obstetrics, gynecology and reproductive medicine at the Pitt School of Medicine, babies need to be protected from infections of their mothers to develop properly. However, previous studies have not been able definitively to show how the placenta, which was long thought to be just a passive barrier between mother and child, protects the child from infections.
"Our findings reveal some of the complex and elegant mechanisms human placental cells, called trophoblasts, have evolved to keep viruses from infecting cells," Sadovsky said in a news release. "We hope that we can learn from this to devise new therapies against viral infections."
Sadovsky and his team exposed human trophoblast cells to various viruses in the laboratory. Researchers found that unlike non-placental cells, trophoblasts were resistant to viral infection. However, that trait was not because viruses cannot bind or enter the cells. Researchers found that when the medium, or fluid environment, in which the trophoblasts were cultured, was transferred to non-placental cells, such as those that line blood vessels, they also became resistant to viral infection.
However, researchers noted that when the medium was exposed to sonication, which involves exposure to sound waves, viral resistance was no longer transferred to non-placental cells. Further analysis revealed that fragments of genetic material called microRNAs contained within the exosomes, tiny spheres called nanovesicles that are secreted by trophoblasts and are sensitive to sonication, were able to induce autophagy, a mechanism of prolonged cellular recycling and survival. Researchers found that blocking autophagy at least partially restored the cells' vulnerability to viral infections.
"Our results suggest this pathway could be a powerful evolutionary adaptation to protect the fetus and mother from viral invaders," co-senior investigator Carolyn Coyne, Ph.D., associate professor, Department of Microbiology and Molecular Genetics at Pitt School of Medicine concluded. "We might be able to use these microRNAs to reduce the risk of viral infection in other cells outside of pregnancy, or perhaps to treat diseases where enhancing autophagy would be beneficial."