Injected 'Hydrogel' May Help Repair Failing Hearts

Testing in pigs shows it serves as platform for growth of healthy tissue; human trials are planned

HealthDay SHARE

By Carina Storrs
HealthDay Reporter

WEDNESDAY, Feb. 20 (HealthDay News) -- An injected "hydrogel" could someday become a nonsurgical means of repairing damaged cardiac tissue in patients with heart failure, a new study shows.

The material used is based on pig heart tissue. It has proven effective when tested in pigs with failing hearts, and may be a step closer to being an option for patients.

Researchers at the University of California, San Diego, demonstrated that they could inject the hydrogel into the hearts of pigs two weeks after a heart attack and prevent the loss of cardiac muscle and other changes that can eventually lead to heart failure.

"After a heart attack, not only do cells die but the natural scaffold where the cells sit gets degraded and cleared," explained lead researcher Karen Christman, an assistant professor of bioengineering at University of California, San Diego.

"We think the hydrogel provides a temporary physical scaffold that allows the body's own surviving heart cells to repopulate that area, and allows new blood vessels and stem cells to come in, and the net result is we get more cardiac muscle in that region," she said.

So far, the research suggests that the pig-derived hydrogel could be well tolerated by other species. The researchers also injected the material into rat hearts and did not see the type of inflammation that indicates the body is rejecting the material.

This immune tolerance is probably due to the fact that the researchers wash away all the cells from the pig hearts, so that all that is left in the hydrogel are proteins and sugars, Christman explained. Once the proteins are injected into the heart, they self-assemble into a "tangled mess of fibers" that becomes the scaffold, she said.

If the hydrogel makes it to market, it would not be the first pig-derived clinical product. According to Christman, more than one million people have been implanted with material made from pig small intestine to treat injured arteries, repair bladder tissue, tendons and ligaments.

She and her colleagues are planning to begin testing the pig heart hydrogel in people who have had a heart attack, starting in the second half of 2013.

For the treatment, doctors would deliver the hydrogel via a catheter running from an artery in the groin up to the damaged part of the heart, similar to how the material was administered in pigs, Christman said.

Another type of hydrogel that is made from seaweed was shown to have benefit in pigs and is currently being tested in a clinical trial for its safety and effectiveness in people who are at risk for heart failure.

More than 900,000 Americans have a heart attack every year, according to the U.S. Centers for Disease Control and Prevention. Heart attacks can increase the risk of heart failure, which occurs when the heart can't pump enough blood, and is marked by shortness of breath, coughing and fatigue. Approximately 5.7 million people in the United States have heart failure.

"When you have a heart attack, those heart cells die and turn into scar tissue, and over time the heart enlarges and becomes less efficient," which can lead to heart failure, said Dr. Jay Traverse, an associate professor of medicine at University of Minnesota Minneapolis Heart Institute.

Medications, such as ACE inhibitors and beta blockers, or tiny mesh stents to open up the artery can help prevent heart failure in a lot of people, he said. "But still a lot of people go on to develop heart failure, so the drugs are not enough," he explained.

"The two main areas that look promising are using stem cells and the use of these biomaterials that [Christman's] paper addresses," Traverse said.

A number of researchers, including Traverse, are studying the effects of injecting stem cells via a catheter into patients' hearts after a heart attack in the hope of spurring regrowth of cardiac muscle and preventing heart failure. The stem cells come from the heart or bone marrow of the patient or a donor.

The results have been mixed, with some studies reporting improvements in measures of heart pumping efficiency whereas others have not found differences in heart function.