Mend a Broken

Let a Few Cells Mend a Broken Heart

By Chris Vaughan
Illustration Philippe Weisbecker

When a person has a heart attack, heart muscle cells that go too long without oxygen die, leaving behind scar tissue — a layer of stiff, bulky cells that hinders the proper contraction of the heart. When the heart muscle, or myocardium, is so severely damaged that the heart can't pump enough blood to sustain the body, there is often little recourse but a heart transplant.

Stanford researcher Mehrdad Rezaee, MD, PhD, and colleagues in the division of cardiovascular medicine are at the forefront of research into an alternative with fewer hurdles and risks than heart transplants: replacing the scar tissue with normal muscle cells from the patient's own body. Rezaee and his team have developed the technique over the last decade and have successfully performed it on pigs. Building on this work, others have begun testing the procedure on human patients.

"The theory is that if you put normal cells in the scarred region, they will help remodel the tissue," explains Rezaee, director of the experimental interventional laboratories at Stanford.

The theory seems to work. Through their animal experiments, the researchers found that when they inject normal muscle cells (they used leg muscle cells) into heart muscle scar tissue, the new cells take up residence, reproduce and interact with healthy myocardial cells. What's more, Rezaee notes, the injected cells often replace the scar tissue as they grow.

While several scientists around the world are working to replace damaged heart muscle cells with other types of cells, Rezaee and his colleagues helped pioneer this technique, known as cell transplantation, having begun the basic research in the late 1990s.

In 1999 they began testing the treatment on pigs, implanting the pigs' own muscle cells into the myocardium through open-heart surgery. Later the team achieved the same result without opening the animal's chest, by implanting cells through a catheter inserted into a leg artery. The team has further reduced the risk of complication by delivering the implanted cells through a cardiac vein rather than an artery.

Though experimental, cell transplantation for hearts shows promise. Researchers in France and the Netherlands have successfully performed the technique on a few human patients. In the United States, 11 cell transplants during coronary artery bypass surgery have been conducted. And within two years, the Stanford team plans to be the first to introduce the implanted cells through a patient's cardiac vein.

Compared with the current treatment — a heart transplant — cell transplantation offers many advantages. Foremost among them is freedom from dependence on donor hearts, which are in perilously short supply. And because the implanted cells come from the patient, anti-rejection drugs aren't needed.

The Stanford researchers are now exploring implants of other cell types, which might yield even better results. "One of the most exciting areas is transplanting bone marrow cells, but we are also looking at transplanting fibroblasts or even genetically engineered cells," Rezaee says. "Eventually, no one may need heart transplants.

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