Study reported in Developmental Cell and done in mice implicates miR-126.

Researchers at UT Southwestern Medical Center discovered that the development and repair of blood vessels and heart tissue is dependent upon a particular type of miRNA.

Their work focused on miR-126, already associated with blood vessels. The scientists found that miR-126 is located only in endothelial cells.

The team genetically engineered mice to not have miR-126 and found that about 40% died before or just after birth. Those mice showed cardiovascular abnormalities like fragile, leaking blood vessels.

Because the surviving mice appeared normal and lived to adulthood, researchers concluded that miR-126 is important in creating new blood vessels but that once the cardiovascular system is established, the miRNA is not needed to maintain the system.

The surviving mice remained vulnerable, however. After a simulated heart attack, nearly all the mice without miR-126 died within three weeks, while 70% of normal mice survived for at least three weeks.

The researchers also tested the role of miR-126 in the branching of blood vessels using cut sections of mouse aortas in culture. When cultured with growth factors that stimulate branching, aortal sections from normal mice displayed branching of their endothelial cells. Those without the miRNA displayed little branching development.

The study appears in the August 11 issue of Developmental Cell.

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