Stem cells from the placenta can travel to injured tissues in the mother's heart during pregnancy and create new cardiac cells, according to a new study.

Researchers at Mount Sinai Medical Center (MSMC; New York, NY, USA) induced heart attacks in pregnant mice and then checked to see if the fetal cells had transferred to the mother. To make the fetal cells easy to spot, they were genetically tagged with green fluorescent protein (GFP). The researchers found that the fetal cells selectively and specifically migrated to the injured zone of the maternal hearts, and not to noninjured organs within the same mouse. Two weeks after the animal's induced heart attack, fetal cells comprised 2% of the maternal heart; furthermore, the fetus-derived cells differentiated into heart muscle cells and cells that form blood vessels or the endothelial lining of blood vessels and other organs.

The cells could similarly differentiate when isolated from the mother's heart and grown in Petri dishes, even forming beating cardiac cells in culture. About 40% of the fetal cells that incorporated into the mothers' hearts expressed Cdx2, a marker of trophoblast stem cells, which form when embryonic stem cells develop; though embryonic stem cells lead to all the cell types in fetus, trophoblast stem cells give rise to the placenta.

The researchers are now conducting lineage-tracing experiments to confirm the precise origin of the cells. The nonexpressing cells (60%) could still be from the placenta, and may have switched off Cdx2 or other early progenitor markers and differentiated into cardiac cell types. The study was presented at the American Heart Association (AHA) Scientific Sessions 2011, held during November 2011 in Orlando (FL, USA).

“If we can confirm that trophoblast stem cells are directly involved in mediating cardiac repair in the injury state, then we may just have found that elusive cell type, other than the embryonic stem cell, that can truly become a beating heart muscle cell,” said senior author and study presenter cardiologist Hina Chaudhry, MD. “You could bank placentas and isolate stem cells and potentially use them in other individuals and not just for peripartum cardiomyopathy, but for a broad spectrum of heart diseases.”

The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. The placenta functions as a fetomaternal organ with two components: the fetal placenta (Chorion frondosum), which develops from the same sperm and egg cells that form the fetus, and the maternal placenta (Decidua basalis), which develops from the maternal uterine tissue.

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