A University of California, Riverside study reports that cells in the early stages of human development may be more susceptible to infection by SARS-CoV-2, which causes coronavirus disease 2019 (COVID-19), providing new insights into how the virus interacts with developing human tissues and why it is important for pregnancy research.
Researchers Anne Song and Prue Talbot used a “disease in a dish” laboratory model of early human embryonic development to examine how different cell types respond to exposure to man-made SARS-CoV-2-like particles. They found that multiple early embryonic cell types can be infected, but their susceptibilities vary widely. Cells destined to become the ectoderm (the layer that eventually forms the skin and nervous system) were the most vulnerable.
Ectodermal cells are approximately 23 times more susceptible to infection than undifferentiated embryonic stem cells and 6 times more susceptible to infection than mesodermal cells.
Anne Song, lead study author and doctoral student, Department of Molecular, Cellular, and Systems Biology, University of California, Riverside
Mesodermal cells are the intermediate layer of embryonic stem cells that differentiate into essential tissues.
Increased vulnerability appears to be driven by several biological characteristics. The researchers found that ectodermal cells showed increased activity of TMPRSS2, a protein that helps viruses enter cells. Additionally, these cells have a thin protective glycocalyx, making it easier for the virus to bind to the ACE2 receptors on the cell surface, a membrane-bound protein that serves as the SARS-CoV-2 virus’s primary entry point.
“Together, these factors create highly favorable conditions for viral attachment and entry, highlighting how certain early cell types are particularly permissive for infection,” said Talbot, a professor at the school and Song’s supervisor.
Professor Song said the findings highlight the urgent need for clinical research to monitor the long-term neurological and developmental health of infants born to mothers infected with COVID-19 during early pregnancy.
“Our findings highlight the urgent need for clinical research to monitor the neurological and developmental health of infants born to mothers infected with COVID-19 early in pregnancy over time,” she said.
This study was conducted using an experimental model rather than pregnant individuals. Although the results of this study do not prove that embryos are actually infected during pregnancy, they do indicate that, in principle, very early stages of development may be biologically more susceptible to the virus.
The results provide insight into the first weeks of human development (weeks 1 to 4), which are difficult to study directly. Because the ectoderm gives rise to the brain and nervous system, its high sensitivity raises important questions regarding potential developmental risks. If infection occurs at this stage, it may contribute to delayed neurodevelopment and structural abnormalities.
“This study gives us a clearer picture of how SARS-CoV-2 interacts with human cells early in life,” Talbot said. “Further research is needed to understand the real-world implications.”
sauce:
University of California, Riverside
Reference magazines:
Song, A., and Talbot, P. (2026). SARS-CoV-2 pseudoparticles preferentially infect the ectoderm of human fetal tissue. Frontiers of cell and developmental biology. DOI: 10.3389/fcell.2026.1733662. https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2026.1733662/full.
