'Breakthrough' stem-cell patches stabilized woman's heart as she awaited transplant

A woman with a failing heart has been kept alive with the help of a new "breakthrough" stem-cell technology, scientists report.

The 46-year-old woman had experienced a heart attack in 2016 and subsequently developed severe heart failure, in which the heart cannot pump blood efficiently enough to meet the body's needs. The patient was awaiting a heart transplant when she underwent the experimental stem-cell procedure as part of a clinical trial.

During the surgery, the woman's heart was implanted with tiny patches of heart muscle cells, which had been grown from stem cells in a lab. These 10 patches, each comprised of about 400 million heart cells, kept the woman stable until she could receive a heart transplant three months later, according to a paper published Wednesday (Jan. 29) in the journal Nature.

"We now have, for the first time, a laboratory-grown biological transplant available which has the potential to stabilize and strengthen the heart muscle," study co-author Dr. Ingo Kutschka, a heart surgeon at University Medical Center Göttingen in Germany, said in a press conference, Nature News reported.

Related: In a 1st, baby's heart defect successfully treated with injected stem cells

Unlike many other cell types, such as skin cells, heart muscle cells cannot easily regrow or repair themselves if they are damaged by an insult like a heart attack. Such damage to the heart can lead to heart failure, which affects around 6.7 million adults ages 20 and older in the United States, according to the Centers for Disease Control and Prevention (CDC). Heart failure was listed as a contributing or primary cause of death on more than 450,000 death certificates in the U.S. in 2022, the CDC reported.

Over half of people with severe heart failure die within a year unless they receive a heart transplant, but there are limited donor hearts available, Nature News reported.

To supplement these limited heart transplants, scientists have experimented with transplanting heart muscle cells instead. In the new Nature paper, the researchers describe a method of growing heart tissue from stem cells known as induced pluripotent stem cells (iPSCs). Scientists create these stem cells by gathering normal adult cells and then reprogramming them back into a "pluripotent" state, from which they can develop into almost any cell type in the body.

The scientists encouraged these iPSCs to develop into heart muscle cells and connective tissue in the lab; the researchers then mixed the resulting tissue with collagen to create tiny patches that could be implanted onto the surface of the heart.

"The graft is basically outside of the heart," Dr. Jianyi Zhang, an iPSC bioengineering expert at the University of Alabama at Birmingham who was not involved in this study, told Nature. "It's quite a breakthrough."

The scientists first tested similar patches on rhesus macaque monkeys (Macaca mulatta) with heart failure; the patches tested on monkeys were grown with monkey stem cells. Six months later, several of the monkeys grew thicker heart walls that could pump up to 10% more blood per heartbeat than a group of untreated monkeys.

During the patch procedure, the monkeys were all given immunosuppressant drugs, to prevent their immune systems from rejecting the grafts. Additionally, none of the monkeys developed tumors or irregular heartbeats, which had been a problem in similar studies conducted in the past.

The success of the monkey trial enabled the trial in human volunteers, one of whom was the 46-year-old woman. After the woman underwent her heart transplant, the researchers examined her old heart and saw that the implanted patches had grown minuscule blood vessels, indicating that they were receiving blood and oxygen from the body.

"This is clear now, that you can add muscle to the failing heart, and that we can do that without safety concerns," study co-author Wolfram-Hubertus Zimmermann, a pharmacologist at University Medical Center Göttingen, said in the press conference.

The eventual hope is that this approach will help people stay alive for long enough to receive a donor heart; it's not intended as a complete alternative to transplants.

In an ongoing trial, the scientists have so far implanted the patches in 15 other people. They are also experimenting with more macaques to find a way to minimize the use of immunosuppressant drugs, which help prevent rejection but can leave a patient vulnerable to infection and other health problems.