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'Patching' a Broken Heart

Researchers hope heart tissue can one day be used to repair heart damage

MONDAY, April 22, 2002 (HealthDayNews) -- A dime-sized piece of heart tissue sitting in a Massachusetts laboratory has no pulse -- unless someone zaps it with electricity. But this "mini-heart" is quite literally a piece of space-age technology, and researchers hope it will lead to a new era in cardiology.

The goal is to create "patches" for the heart, which can't regenerate itself after damage, like that suffered during a heart attack. Vital to the researchers' work is a "bioreactor," a small rotating device invented by NASA to simulate the effects of weightlessness on cells.

"The motivation is to eventually make something function and useful," says Gordana Vunjak-Novakovic, a research scientist who is helping to develop the heart patch at the Massachusetts Institute of Technology.

While scientists have developed artificial hearts, they've had trouble finding ways to properly repair a malfunctioning heart, especially if parts of the organ have died. Heart failure and heart attacks can both kill parts of the heart, and doctors often can only turn to medicine to help a patient cope, says Dr. Jerrold Glassman, a cardiologist at Scripps Mercy Hospital in San Diego.

"When the heart muscle is weak [due to tissue death], the way to treat it is to make the muscle that's there as efficient as possible," he says.

Finding a way to regenerate heart tissue or add new tissue to a heart would be a "huge" development, he says. "Quality of life would go up, there's no question about it."

Vunjak-Novakovic and a fellow researcher, Lisa E. Freed, set out to "reconstruct" a piece of heart muscle that could be used as a patch. The challenge, Vunjak-Novakovic says, was to find a liquid solution that would mimic conditions in the human body for the cells that make up the patch.

They found the perfect home in a bioreactor, a device about the size of a soup can that slowly turns, gently sloshing the solution inside. The liquid brings oxygen to the cells, allowing them to stay alive.

The bioreactor also mimics weightlessness. Without most of gravity's effects, the cells don't sink to the bottom, but instead remain suspended, Vunjak-Novakovic says.

"They like this rotating environment because it has very gentle motion and stimulation. It probably reminds cells of the stimulation they're receiving in a body due to blood circulation," she says.

The bioreactor also provides "scaffolding" that allows the cells to join each other and form tissue, Vunjak-Novakovic says.

"If the conditions are right, the cells will do what they would normally do in a body, fuse and connect and start to talk to each other," she says.

The MIT scientists can actually make the heart tissue contract -- just like during a heartbeat -- when they hit it with a pulse of electricity. That's because the cells have developed connections between themselves that allow for an exchange of electrical signals.

The tiny piece of heart tissue is a first step toward a patch that could be used on an actual heart that has suffered damage. But Vunjak-Novakovic acknowledges that much more work needs to be done. For one thing, the most vital layer of tissue is only 5 to 10 millimeters thick.

"It's pretty good, but very thin," she says. "Our big challenge is to make it thicker, and we are trying to do that by mimicking some of the [tissue-building] mechanisms that you can find in a body."

Thicker tissue would mean a thicker patch, and a better chance at repairing a damaged heart.

What to Do: See what the tiny piece of heart tissue looks like, and watch it beat, at this NASA Web site. To learn more about your risks for heart disease, visit The American Heart Association. And take this heart health test, offered by the Texas Heart Institute.

SOURCES: Gordana Vunjak-Novakovic, Ph.D., principal research scientist, Massachusetts Institute of Technology, Cambridge, and adjunct professor of chemical engineering, Tufts University, Boston; Jerrold Glassman, M.D., cardiologist, Scripps Mercy Hospital, San Diego
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