New York, March 6 (IANS): US researchers devised a cell-based model of the human placenta that could help explain how pathogens that cause birth defects originating from Zika virus cross from mother to the unborn child.

The model can be used to experiment different biological factors to see what might allow an infectious agent to get through the placental barrier to the foetus.

"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 Carolyn Coyne, associate professor at University of Pittsburgh, US.

The researchers cultured a group of human placental cells in a microgravity bioreactor system developed by NASA.

The cells along with blood vessel cells were added to small beads, which then spun around a container filled with cell culture fluid.

The scientists managed to cause the cells to fuse to form syncytiotrophoblasts - resembling the cells lining the outermost layer of human placental tissue.

Next, the researchers tested the functional properties of their model by exposing it to a virus and to Toxoplasma gondi - a parasite that can lead to foetal infection, causing miscarriage, congenital disease and, or disability in later life.

They found that the syncytiotrophoblasts formed in human 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.

The human placenta is unique and unlike that of other mammals. It 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 micro-organisms from an infected mother to the foetus.

Understanding the placenta might lead to ways to prevent foetal damage from the so-called TORCH infections: toxoplasmosis, rubella, cytomegalovirus, herpes and HIV, the researchers concluded in the study published in Science Advances.