Heart failure is one of the leading causes of illness and death worldwide.
It affects millions of people and often develops after a heart attack damages part of the heart muscle. When heart muscle cells die, the body cannot fully replace them.
Instead, the damaged area is replaced with scar tissue. Unlike healthy heart muscle, scar tissue cannot contract and pump blood. As a result, the heart gradually becomes weaker, leaving patients tired, short of breath, and unable to perform normal daily activities.
For people with severe heart failure, treatment options are limited. Medicines can slow the disease, and medical devices can help support the heart, but neither can replace lost heart muscle.
In the most serious cases, patients may need a heart transplant or a mechanical heart pump. Because donor hearts are scarce and major surgery carries risks, researchers have spent decades searching for new ways to repair damaged hearts.
Now, scientists in Germany have reported a major breakthrough. Researchers at the University Medical Center Göttingen and the University Hospital of Schleswig-Holstein have shown for the first time in a clinical trial that laboratory-grown heart muscle tissue can improve the pumping ability of severely damaged hearts.
The findings were published in the New England Journal of Medicine and are part of a larger research program led by the German Center for Cardiovascular Research.
The study included patients with advanced heart failure whose hearts were functioning very poorly despite receiving the best available treatments. One of these patients was Steffen Eyring, who suffered a severe heart attack in 2020.
Although he survived and completed rehabilitation, his heart remained badly damaged. Over time, simple activities became increasingly difficult. Walks that once took 30 minutes became much longer because he needed frequent stops to catch his breath.
Doctors eventually recommended a mechanical heart assist device because his heart was pumping only about 18% to 20% of the blood it should. Instead, Eyring chose to join an experimental study testing a new type of heart repair.
The treatment uses induced pluripotent stem cells, often called iPS cells. These cells are created in the laboratory from ordinary blood cells. Scientists can reprogram them into an early developmental state and then guide them to become different cell types. In this case, researchers transformed them into heart muscle cells and supportive connective tissue cells.
The cells were combined with collagen, a natural protein found throughout the body, to create living heart tissue. Multiple pieces of this tissue were assembled into a patch containing hundreds of millions of living heart cells. The patch was then attached to the outside of the damaged heart through a minimally invasive surgical procedure.
The goal is not to replace the entire heart but to create a new layer of healthy muscle that can support the weakened organ. Researchers hoped that the patch would survive, integrate with surrounding tissue, and help improve the heart’s ability to pump blood.
The results were encouraging. Twenty patients with severe heart failure participated in the Phase I/II clinical trial. Researchers first determined the highest dose that could be safely implanted, which was about 800 million heart cells. They then evaluated the effects in patients who received this dose.
Three months after treatment, imaging studies showed that damaged areas of the heart wall had become thicker. This suggests that the new tissue was helping strengthen regions weakened by previous heart attacks.
Researchers also observed improvements in heart pumping function and quality of life. Some patients reported feeling better and more capable of carrying out daily activities.
Importantly, follow-up data extending for more than four years showed signs that some of these benefits could be sustained over time. While the improvements varied among patients, the findings suggest that repairing damaged heart muscle may be possible.
Researchers describe this as an important proof of concept. For many years, scientists have successfully grown heart cells in laboratories and tested them in animals. Demonstrating safety and potential benefit in human patients represents a major milestone.
The study’s strengths include its careful clinical design and its use of living tissue created from stem cells. However, there are also important limitations. The trial involved only 20 patients and was primarily designed to assess safety.
Larger studies will be needed to confirm whether the treatment consistently improves survival, reduces hospitalizations, or significantly changes the course of heart failure.
Even so, the findings provide hope for a future in which damaged hearts can be repaired rather than simply managed. Researchers are already planning larger studies involving additional hospitals in Germany, Europe, and the United States.
If future trials confirm these results, laboratory-grown heart patches could eventually become a valuable new option for patients with severe heart failure who currently have few alternatives.
The study was published in the New England Journal of Medicine.
Source: University Medical Center Göttingen and University Hospital of Schleswig-Holstein.
