Repairing broken hearts with injectable patches

What if a damaged heart could be repaired without surgery to open up the chest cavity? Scientists at the University of Toronto are developing tiny heart patches that they hope will provide a noninvasive way to significantly relieve symptoms in patients with heart failure.

The patches are made of heart tissues that are grown in a lab. One of the patches, which they call AngioChip, comes complete with blood vessels and heart cells that beat. And it’s designed to be injected into the heart with a small needle. The researchers tested their patches in rats and pigs with promising results, which they published in the journal Nature Materials.

"It can't restore the heart back to full health, but if it could be done in a human, we think it would significantly improve quality of life," said co-author Milica Radisic, a professor of biomedical engineering at the University of Toronto, in a press release.

It was no easy feat, though. Radisic and her team used polymer scaffolds to grow 3D slices of human heart tissue. It took years of trial and error to come up with a design that has “shape memory,” meaning if it were folded into a syringe and injected, it would unfold itself into a patch, without requiring additional procedures and without being impeded by natural body chemistry.

Once they mastered that design, they seeded the patches with heart cells, let the cells grow for a few days, and then injected them into the animals. They discovered that the patches unfolded properly. And the heart cells survived the procedure—a notable accomplishment, because cardiac cells are notoriously sensitive. The researchers showed that the technique improved cardiac functions in rats after a heart attack, as the damaged ventricles were able to pump more blood with the patches than without them.

Cardiac conditions such as heart failure are irreversible and traditionally managed with drugs. So scientists around the world have been searching for better, more permanent solutions, many of which involve cell therapy. For example, scientists at the University of Utah School of Medicine have been testing a procedure that involves extracting stem cells from the bone marrow of heart patients and injecting them via catheter into their hearts. Last year, they published results from a phase 2 trial showing a reduction in hospitalizations and deaths in the patients who received the cells.

The University of Toronto team is now collaborating with the Hospital for Sick Children to assess whether the benefits of their injectable patches are sustainable and how stable the patches stay over time. They also hope to test their invention in other organs, including the liver.