Engineered tissue mimics natural heart muscle

Scientists have engineered tissue which closely mimics natural heart muscle that beats not only in a lab dish but also when implanted into animals.
When a heart gets damaged, such as during a major heart attack, there is no easy fix. Currently, the best treatment option for patients with major heart damage is an organ transplant.
However, there are far more patients on waitlists for a transplant than there are donated hearts. Even if a patient receives a new heart, complications can arise.
Researchers at the Brigham and Women's Hospital and Harvard Medical School in Boston and the University of Sydney in Australia have combined a novel elastic hydrogel with microscale technologies to create an artificial cardiac tissue that mimics the mechanical and biological properties of the native heart.

"Our hearts are more than just a pile of cells. They're very organised in their architecture," said Ali Khademhosseini, who is at Harvard Medical School.
To tackle the challenge of engineering heart muscle, Khademhosseini and colleagues have been working with natural proteins that form gelatin-like materials called hydrogels.

They are soft and contain a lot of water, like many human tissues.
Khademhosseini's group has found that they can tune these hydrogels to have the chemical, biological, mechanical and electrical properties they want for the regeneration of various tissues in the body.
But there was one way in which the materials didn't resemble human tissue. Like gelatin, early versions of the hydrogels would fall apart, whereas human hearts are elastic.

So, the researchers developed a new family of gels using a stretchy human protein aptly called tropoelastin. That gave the materials much needed resilience and strength.
Making the right hydrogels is only the first step. They serve as the tissue scaffold. On it, the researchers grow actual heart cells. To make sure the cells form the right structure, Khademhosseini's lab uses 3-D printing and microengineering techniques to create patterns in the gels.
These patterns coax the cells to grow the way the researchers want them to. The result is small patches of heart muscle cells neatly lined up that beat in synchrony within the grooves formed on these elastic substrates.

These micropatterned elastic hydrogels can one day be used as cardiac patches. Khademhosseini's group is now moving into tests with large animals.
The study was presented at a meeting of the American Chemical Society (ACS) in Dallas.