RESEARCH has revealed how the COVID-19 virus infects the placenta, and how this can be prevented. Scientists have shown that COVID-19 infections during pregnancy may lead to adverse outcomes, but little is known about the mechanisms behind the effects of SARS-CoV-2 infection in pregnancy. Researchers found that ACE2, a protein that acts as the doorway for SARS-CoV-2 to enter organs such as the lung, is present in specific placental cells, including syncytiotrophoblasts (ST cells). Importantly, ST cells were susceptible to the virus, an important finding as these placental cells produce the key hormone for maintaining pregnancy (hCG). The study published last week in Nature Cell Biology by Australian researchers, was led by Prof Jose Polo from Monash University and the University of Adelaide and University of Melbourne’s Prof Kanta Subbarao from the Peter Doherty Institute for Infection and Immunity (Doherty Institute). The Australian research team grew placenta tissue in the lab, using a state-of-the-art method developed by Prof Polo and colleagues, where human skin cells are “reprogrammed” into trophoblast stem cells (the cells that help a developing embryo attach to the wall of the uterus, forming part of the placenta). Dr Joseph Chen, a stem cell biologist at Monash University and co-first author of the report, said this discovery explains several clinical reports indicating inflammation of the placenta due to COVID-19. “We observed that SARS-CoV-2 infection led to a significant reduction in the survival and differentiation of ST cells, which in turn resulted in lower production of hCG,” he said. “It suggests that this is how COVID-19 could impact pregnancy, though further investigations are needed.” Virologist at the Doherty Institute and co-first author of the study Dr Jessica Neil said, “our team also discovered that anti-ACE2 antibodies and antiviral drugs were effective in preventing SARS-CoV-2 infection and restoring normal ST differentiation and function”. Subbarao said that this study is a significant advance for the broader understanding of viral infections in pregnancy. “Our study provides valuable insights into the link between SARS-CoV-2 infection and placenta pathology. “This is a game changer as we are now equipped to explore how the early placenta may be affected by other viruses as well,” she said. Polo emphasised the importance of the research in establishing a platform to study early placental cell types. “This study not only helps us to understand what happens when the placenta is infected with the COVID-19 virus during pregnancy, it also means we have established a broader, scalable and tractable platform to study early placental cell types,” he said.