Tiny molecule helps control blood-vessel development, UT Southwestern resear...( DALLAS Aug. 12 2008 The developmen...),Health

DALLAS Aug. 12, 2008 The development and repair of heart tissue and blood vessels is intimately tied to a tiny piece of ribonucleic acid (RNA) that is found nowhere else in the body, researchers at UT Southwestern Medical Center have found.

Because of its specificity to the cardiovascular system, this "microRNA" is an attractive potential target for therapeutic treatment, the researchers said.

"Manipulating this microRNA provides a completely new way of addressing cardiovascular disorders," said Dr. Eric Olson, chairman of molecular biology and senior author of a study appearing in today's issue of Developmental Cell.

MicroRNAs are tiny snippets of genetic material, naturally produced by the body, that help fine-tune the production of proteins by DNA. More than 500 have already been identified.

In the current study, the researchers focused on a specific microRNA called miR-126, which was already known to be associated with blood vessels. They found that miR-126 is found only in a class of cells called endothelial cells, which line the inside surfaces of blood vessels.

Endothelial cells control the development of new blood vessels in developing embryos; the repair of injured blood vessels; and the creation of blood vessels to support developing tumors.

The researchers genetically engineered mice to lack miR-126, and found that about 40 percent of them died before or just after birth. These mice showed cardiovascular abnormalities such as fragile, leaking blood vessels.

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

However, the surviving mice were less able to recover from a simulated heart attack. Almost all mice lacking miR-126 died within three weeks, while 70 percent of normal mice su
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