‘Breakthrough’ stem-cell patches strengthened a woman’s failing heart

Grafting patches of lab-grown muscle to the surface of the heart could offer a lifeline for people waiting for a transplant

A heart muscle cell. A failing heart can be stabilized with patches of muscle grown from stem cells.Credit: Thomas Deerinck, NCMIR/Science Photo Library

Researchers have shown that patches of muscle grown from stem cells can help to repair a failing heart, in a clinical trial that tested the procedure on a 46-year-old woman.

The woman, who had a heart attack in 2016 and later developed heart failure, had an operation to implant 10 patches of 400 million cells on the surface of her heart. Her condition then remained stable for three months, long enough for her to receive a heart transplant. Scientists who examined her old heart found that the implanted muscle patches had remained in place and formed blood vessels.

The results of the trial, which took place in 2021, were published in Nature on 29 January¹, alongside findings from earlier studies that tested muscle patches containing between 40 million and 200 million cells each in rhesus macaques (Macaca mulatta).

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

“It’s quite a breakthrough,” says Jianyi Zhang, who specializes in bioengineering and using induced pluripotent stem cells (iPSCs) — cells reprogrammed from an adult state to allow them to differentiate into any cell type in the body — for cardiac repair at the University of Alabama at Birmingham.

The treatment is not intended to replace the need for a full transplant, but it can help people with advanced heart failure who are waiting for a heart to become available.

“Less than 1% of the patients in need are heart transplanted,” said study co-author Wolfram-Hubertus Zimmermann, a pharmacologist at University Medical Center Göttingen, during the press briefing. This approach “is offering another treatment to patients that are presently under palliative care”.

The researchers have implanted similar muscle patches into 15 people so far, and hope to recruit more participants.

Patched-up hearts

An estimated 60 million people worldwide are living with heart failure, and more than half of people who enter severe heart failure die within a year. A lack of donors means that there are not enough hearts available for most people who need them, and artificial pumping devices are expensive and require invasive surgery.

For many years, scientists have experimented with implanting or directly injecting stem cells or muscles grown from them into the heart. But these procedures often result in irregular heartbeat, growth of tumours or rejection by the body’s immune system.

Zimmermann and his team engineered iPSCs to grow into heart muscle and connective tissue. They mixed these cells with collagen gel to create patches, and developed a minimally invasive procedure to place them on the surface of the heart. “The graft is basically outside of the heart,” says Zhang.