Science Creates a Living Bandage for Broken Hearts
'Cardiac patch' and other advances are on the horizon, researchers say
FRIDAY, Jan. 20, 2006 (HealthDay News) -- Hybrid cars are grabbing headlines, but how about "hybrid hearts"?
Merging artificially engineered products with a patient's own heart to stop or reverse cardiac damage could be the wave of the future, researchers say.
One such innovation, the "cardiac patch," is just that: A piece of living, beating cardiac tissue, grown in the lab in just a few days and applied to hearts wounded by prior heart attack or chronic disease.
"We joke that this is really 'a patch for a broken heart,'" said Gordana Vunjak-Novakovic, professor of biomedical engineering at Columbia University Medical Center in New York City, and co-director of the Tissue Engineering Resource Center at the National Institutes of Health in Bethesda, Md.
She described the new technology at a special "Hybrid Technologies" symposium held Thursday in New York City, part of the Second International Conference on Cell Therapy for Cardiovascular Diseases.
Hearts affected by heart attack or congestive heart failure develop large areas of scar tissue that is essentially non-functioning. In the most serious cases, drugs are of little help, and demand for heart transplants far outstrip the supply of donor hearts.
"So, we are trying here to make heart tissue," Vunjak-Novakovic explained. The process mimics that seen in nature, with scientists replicating the cardiac environment inside a special tissue-growing chamber called a bioreactor.
Everything has to be right: Cardiac cells must grow at a very high density but also be well-oxygenated, just as they are in the developing heart. And those cells must also be artificially electrically stimulated, since it is electric pulses that keep hearts beating.
So far, the Columbia lab has achieved real success: Vunjak-Novakovic presented video of thumbnail-sized cardiac patches rhythmically twitching just as real heart muscle does.
But the patches have not yet made their way into humans, and they may not do so for many years, Vunjak-Novakovic said.
"The real challenge is that you have to place the patch upon the heart in a way that it integrates into the heart," she said. "You don't want it to just sit there as a separate entity. It needs to connect electrically so that it syncs up with signals coming from the cells, so everything works together." Getting the patch's blood vessels to merge with those of the host heart will be another challenge, she added.
But animal trials tackling those issues are already under way, the Columbia researcher said. Someday, perhaps a decade from now, human trials might begin. And in the more distant future, the cardiac patch -- grown either from the patient or delivered "off the shelf" -- might become a routine part of cardiac care, she said.
Materials called "biopolymers" are another innovation in the cardiac-repair pipeline, according to Dr. Randall Lee, an assistant professor of medicine in the department of cardiology at the University of California, San Francisco School of Medicine.
Speaking at the meeting, he explained that these synthetic materials, with names like "alginate," "fibrin glue" and "matrigel," are injected into damaged cardiac tissue to form a kind of sticky scaffolding. In the same way that a shipwreck gives rise to a coral reef, biopolymers help gather together cells responsible for repairing and rebuilding tissue.
Biopolymers might prove especially useful for stem cell therapy, which shows great promise but has so far been disappointing when it comes to cardiovascular repair, he said.
"It may be that stem cell therapy does work -- but you're just not getting enough of the cells to stay in the area," Lee said. "You might inject 100 cells, and maybe only five stay there."
But fibrin glue, the biopolymer Lee's lab uses, comes equipped with special chemical binding sites. "These are anchors that a cell can grab on to so they stay there," he said.
In studies presented at the meeting, Lee noted that use of fibrin glue greatly increased the number of myoblasts -- progenitor heart muscle cells -- in cardiac tissue, and also boosted the formation of blood vessels. The biopolymer is gradually absorbed into tissue by about two weeks, essentially disappearing once its job is done, he said.
Lee believes second-generation biopolymers are also on the horizon, materials that will actively recruit natural, heart-healing cells and growth factors to cardiac tissue sites in need of repair.
"It's recruiting the body's own cells," he said. "That could then facilitate the whole process of regeneration."
To learn more about how the heart works, head to the American Heart Association.