The origin of an immune cell that plays a critical role in the formation of healthy heart valves has been found, opening the way for new treatments for heart valve disorders, it has been announced.
The study by researchers at the University of California, Los Angeles, USA, builds on previous studies that established the embryonic heart tube produces blood progenitor cells and has concluded that those cells, in turn, generate macrophages.
The new research, led by Dr Atsushi Nakano, a UCLA associate professor of molecular, cell and developmental biology and published in Developmental Cell, also revealed that these heart-derived macrophages consume excess tissue, helping to shape the formation and maintenance of heart valves.
Dr Nakano said new methods for treating valve disorders are urgently needed because there are only two options available: mechanical valves and biological valves.
“Ever since we discovered that the heart tube produces some blood progenitor cells, we have been trying to figure out why,” said Dr Nakano.
The new study involved the researchers removing a heart tube from mice before it began pumping blood and continuing its growth in a lab dish. With no circulating blood to contaminate their sample, the team observed that the heart-derived blood progenitor cells were producing macrophages.
Although previous research has shown that macrophages exist in the heart valves, Dr Nakano’s team is the first to discover that their role is to eat up excess cells to make the valves paper-thin and hyper-efficient.
In testing how essential heart-derived macrophages are to valve formation and remodelling, the researchers blocked their production and found that other macrophages in the body travelled to the heart – but they were not effective at remodelling the valves.
Without the heart-derived macrophages, the heart valves remained thick and unwieldy, said Dr Nakano.
He said he hoped the discovery will pave the way to more permanently solve heart valve conditions.
Developmental Cell 21 February 2019
https://www.cell.com/developmental-cell/fulltext/S1534-5807(19)30049-8
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