Vascular 'Microparticles' May Help Spur Disease

A rise in these naturally occurring particles could hurt the heart, study fnds

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FRIDAY, April 7, 2006 (HealthDay News) -- High levels of circulating "microparticles," shed from cells that line the body's blood vessels, may prompt heart valve dysfunction and disease, a U.S. study suggests.

The study from the Medical College of Wisconsin in Milwaukee and Children's Research Institute is the first to provide evidence of this link.

It's normal for low levels of microparticles to be shed into the blood from the endothelium -- the layer of cells that line the blood vessels and some organs. In most cases, this causes no real problem. However, some diseases can trigger a rise in levels of endothelium-derived microparticles circulating in the blood.

In the study, the Wisconsin team examined whether abnormally high levels of circulating endothelial microparticles affect the endothelial cells that line the heart valve leaflets (flaps). These cells are essential for normal function and repair of the heart valve leaflets and often become damaged or dysfunctional in people with valve disease.

The researchers studied endothelial cells from the mitral valve of a heart taken from an infant who had undergone a heart transplant. The cells were exposed to increasing levels of endothelial-derived microparticles. At lower levels -- similar to those found in healthy people -- the microparticles had a positive effect by stimulating the growth of the mitral valve endothelial cells.

However, at higher levels -- comparable to those seen in people with disease -- the endothelial microparticles inhibited the growth of the mitral valve endothelial cells.

Adjusting levels of endothelial-derived microparticles in people with lupus, rheumatoid arthritis, heart inflammation and certain other diseases may help prevent heart valve damage and dysfunction, the researchers theorized.

The findings were expected to be presented this week at the Experimental Biology annual meeting in San Francisco, and to appear in an upcoming issue of Shock.

More information

The American Heart Association has more about heart valves.

SOURCE: Medical College of Wisconsin, Milwaukee, news release, April 4, 2006

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