Stem cell combo repairs damaged hearts in rats

When people suffer heart attacks, the resulting damage to their cardiac tissue can’t be repaired, which is why stem-cell treatments that could regenerate that lost tissue have long been considered a holy grail among cardiology researchers. Problem is, transplanted stem cells tend to die within a few days of being implanted in the heart, making them largely ineffective.

Scientists at the University of Cambridge in the United Kingdom and the University of Washington have come up with a potential solution to this problem. It’s a combination of cells derived from human stem cells: heart muscle cells to regenerate the damaged tissue, and epicardial cells from the outer part of the heart wall to help the muscle cells live longer.

In rat models, the combination of cells restored both damaged heart muscle and blood vessel cells. The researchers reported the results in the journal Nature Biotechnology.

RELATED: Mount Sinai researchers isolate placental cells that regenerate damaged hearts in mice

The researchers started by testing the combination of heart cells in 3D models of human heart tissue. They observed that the epicardial cells promoted the growth and maturation of the muscle cells and they improved their ability to contract.

When they simultaneously transplanted epicardial cells and heart muscle cells into rats with damaged hearts, the rate of heart-muscle proliferation doubled over that of muscle cells alone, the team reported. The researchers also observed an improvement in “systolic functioning,” which is the ability of the left ventricle of the heart to contract normally.

A handful of companies are working on stem-cell treatments for heart failure, but their efforts have run into plenty of roadblocks. They include Australia-based Mesoblast, which is testing injections of mesenchymal precursor cells in clinical trials. Results from a phase 2 trial released late last year showed the therapy was unable to free patients from their reliance on left ventricular assist devices (LVADs), but the company said it would continue to pursue it.

Around that time, the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH) paused a high-profile trial combining c-kit+ cells with mesenchymal stem cells from bone marrow in patients with heart failure because of concerns related to safety and efficacy. The worries arose from questions that were raised about journal articles pertaining to related cell therapies, the NHLBI said at the time.

The new study from the University of Cambridge and the University of Washington was partly funded by the British Heart Foundation, which remains committed to studying the potential of stem cells for treating heart disease. The foundation currently supports three regenerative medicine research centers in the U.K. that are pursuing the research, according to a statement.

"When it comes to mending broken hearts, stem cells haven't yet really lived up to their early promise,” said Sir Nilesh Samani, Medical Director at the British Heart Foundation, in a statement. “We hope that this latest research represents the turning of the tide in the use of these remarkable cells."