Got a broken heart? It's pretty likely that you'll soon have it repaired with a process roughly akin to patching a punctured tire.

Researchers at the Brigham and Women's Hospital, the Harvard Medical School Wyss Institute in Boston and the University of Sydney have combined a groundbreaking and elastic hydrogel with microscale technologies and 3D printing to create artificial cardiac tissues which mimic the mechanical and biological properties of the heart muscle.

The researchers use the hydrogels to serve as tissue scaffolding on which they grow actual heart cells. Working in the lab, Dr. Ali Khademhosseini of the Harvard Medical School uses 3D printing to create analogous patterns in the gels which help coax those cells to grow in the correct way.

It's a monumental breakthrough which may ultimately lead to a process capable of repairing the millions of human hearts compromised as a result of massive heart attacks. At this stage, the scientists have – and for the very first time – successfully implanted artificial, beating heart tissues in animals.

As it stands, major heart attack damage can only be repaired by the most invasive and unpredictable method – an organ transplant. That's not an ideal situation as waiting lists are always clogged with applicants for a very few donated hearts.

Though it has been done with much simpler liver and other engineered tissues, creating more complex organ tissues from scratch is a complicated process.

"Our hearts are more than just a pile of cells," says Khademhosseini. "They're very organized in their architecture. The reason we like (hydrogels) is because in many ways, they mimic aspects of our own body's matrix. They're soft and contain a lot of water, like many human tissues."

While researchers found they could "tune" hydrogels to give them roughly the biological, chemical, mechanical and electrical properties necessary to regenerate various tissues, the early versions of tissues made from hydrogels tended to break apart too easily. Human heart tissue is elastic, and it's that elasticity which plays a key role in the contractile ability of heart muscles.

The latest iteration of the gels contains a very flexible human protein, a reactive form of tropoelastin called methacrylated tropoelastin, which can be shaped with ultraviolet light. The design apes the construction of human heart tissue by adding linear patterns to the gel to align heart cells. The tissues even contract synchronously on these elastic substrates in response to electrical stimulation and are capable of handling the levels of resilience and strength needed to create "beating" heart tissue.

Khademhosseini calls the resultant structures with their micro-patterned surfaces "cardiac patches," and they're now being tested on large animals.

Research support for the project came from the National Health and Medical Research Council, the National Science Foundation, the Office of Naval Research, the National Institutes of Health, the CRC for Polymers, Australian Research Council, Australian Defense Health Foundation, and the National Health and Medical Research Council.