After a heart attack, scar tissue that can’t contract typically replaces dead cardiac muscle, resulting in chronic heart failure—a scourge affecting 12 million people around the world. But regenerating damaged heart tissue has proven challenging, because in order for the heart to beat properly, the muscle must be able to both contract and transmit electrical signals.
Engineers at Duke University say they’ve created an artificial heart muscle that can be used to patch up the damage in patients who have suffered heart attacks. They did it by taking human pluripotent stem cells—the ones that have the ability to transform into any tissue—and growing them outside of the body, according to a press release. They are able to grow the patches to the proper size and infuse them with the beating strength of a normal adult human heart in five weeks.
The Duke team accomplished that feat by experimenting with different combinations of cells, nutrients and growth factors. They discovered that if they rocked the cells to bathe them in nutrients while they grew in culture, they could grow bigger, thicker heart patches.
"This is extremely difficult to do, as the larger the tissue that is grown, the harder it is to maintain the same properties throughout it," said Nenad Bursac, a Duke professor of biomedical engineering, in the release. Getting the patches to behave like adult human hearts was particularly challenging, because achieving those properties “typically take years of normal human development," he added.
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When the Duke engineers tested their invention in rodent models, they observed that the patches survived, formed blood vessels and maintained their function. The research was published in the journal Nature Communications. (For more, see the video below.)
Several techniques for using human cells to regenerate damaged hearts are being explored, including injecting stem cells directly into damaged heart muscle. Over the summer, a team led by Boston University announced it had invented a 3D-printed patch that could promote the growth of healthy blood vessels in patients with ischemia, a condition that can cause heart attacks. And scientists at the University of Toronto are developing a heart patch that can be folded into a syringe and injected into the damaged organ.
The Duke engineers believe that when it comes to creating a truly effective heart patch, size matters, and their invention is large enough to repair the damage typically seen in people who have suffered heart attacks. That said, the patches would need to be thicker than the ones used in their study before they can be tested in people. Their next challenge will be to figure out how to thicken the patches, vascularize them so they receive enough nutrients and oxygen, and integrate them with existing healthy heart muscle.
"Full integration like that is really important, not just to improve the heart's mechanical pumping, but to ensure the smooth spread of electrical waves and minimize the risk of arrhythmias," said lead author Ilia Shadrin, a Duke doctoral student in biomedical engineering, in the release.