New model shows how infections cross from mom to baby

Scientists have devised a cell-based model of the human placenta that could help explain how pathogens that cause birth defects, such as Zika virus, cross from a mother to her unborn child.
The placenta is a complex and poorly understood organ that anchors the developing foetus to the uterus, nourishes the baby, and provides a barrier to the spread of microorganisms from an infected mother to the foetus, researchers said.
"The human placenta is unique and unlike that of other many other placental mammals," said Carolyn Coyne from University of Pittsburgh in US.
"With our new model in the research toolkit, we and other scientists hope to advance our knowledge of the placenta, examine its function, and learn how it can prevent most, but not all, maternal infections from causing problems for the baby," said Coyne.

Researchers cultured a human placental trophoblast cell line in a microgravity bioreactor system developed by NASA.
The trophoblasts along with blood vessel cells were added to small dextran beads that were then spun around in a container filled with cell culture fluid, creating shear stress and rotational forces to better mimic the environment at the maternal-foetal interface than static cell-culture systems.

As a result, the cells fused to form
syncytiotrophoblasts, and thus more closely resemble the primary cells lining the outermost layer of the tree-like or villous structure of the human placental tissue.
Next, researchers tested the functional properties of their model by exposing it to a virus and to Toxoplasma gondii, a parasite found in cat feces that can lead to foetal infection, causing miscarriage, congenital disease and/or disability later in life.

"We found that the syncytiotrophoblasts formed in our system recapitulated the barrier properties of the naturally occurring cells and they resisted infection by a model virus and three genetically different strains of Toxoplasma," said Jon P Boyle from University of Pittsburgh.
"With this model, we can experiment with different biological factors to see what might allow an infectious agent to get through the placental barrier to the foetus," said Boyle.
Understanding the placenta might one day lead to ways to prevent foetal damage from the so-called TORCH infections: toxoplasmosis, rubella, cytomegalovirus, herpes and HIV, researchers said.
The findings were published in the journal Science Advances.