How to heal a broken (or weakened) heart

A myocardial infarction, most commonly referred to as a heart attack, occurs when blood supply to the heart is blocked. For those who survive, permanent tissue damage is likely; during the blockage cells are literally starved to death, and do not grow back, leaving the heart forever weakened.

If only there was a way to heal a broken heart, instead of having to get an entirely new one, or undergoing a tricky bypass graft.

Enter the cardiac patch, which is essentially a tissue transplant instead of a full-on heart transplant. Using immature heart cells in newborn rats, researchers have found a way to repair the weakened, incomplete hearts of older rats.

Though still in development, the cardiac patch is inching its way closer to human clinical trials, especially after today's publication of research led by Smadar Cohen at the Ben-Gurion University of the Negev in the Proceedings of the National Academy of Sciences.

Here's how the patch works: A biodegradable "scaffold" is seeded with young heart cells and, over the course of two days, exposed to growth-promoting chemicals in a lab. The concoction is then transplanted into a rat's abdomen, where in the course of a week it develops a network of blood vessels and muscle fibers. (Oh, to have young tissue again.) The patch is then grafted onto the rat's heart, where, within a month, it is completely integrated into the heart, actually synchronizing its beat with that of the surrounding tissue.

"Using the body as a bioreactor to engineer cardiac tissue with stable and functional blood vessel networks represents a significant improvement in cardiac patch performance over ex vivo (outside the body) methods currently used for patch production."

Similar cardiac patches have been tested in animals, but with only limited success. In humans, these patches would probably be seeded with cells derived from stem cells, and are being developed to work with livers and bladders as well. The biggest problem with the patch, according to the researchers, is that multiple surgery on older patients--precisely the population where heart attacks are most common--is generally risky.

Separately, researchers from the Southern Arizona Veterans Administration recently put rat heart cells on a piece of synthetic mesh and watched it start beating, within a matter of days, on its own. NPR's Science Friday posted a cool video of the results:

Brings new meaning to Woody Allen's famous line of defense: "The heart wants what it wants."