Mesenchymal stem cells labeled with fluorescence molecules
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People who received a stem cell infusion shortly after a heart attack were less likely to develop heart failure than those treated with standard care, according to the largest trial of its kind to date. This discovery represents some of the strongest evidence yet that stem cells can help the heart repair itself.
After a heart attack, the heart muscle is permanently damaged and weakened, often leading to heart failure, when the organ cannot pump enough blood to meet the body’s demands. Currently, there is no treatment other than a heart transplant or pump that can restore heart function.
As a potential solution, researchers have turned to stem cells, which have the unique ability to transform into other cell types. But previous studies looking at their use after a heart attack have shown mixed results. For example, a 2020 trial involving 375 people found that bone marrow-derived cells, including stem cells that turn into blood cells, failed to reduce the risk of death to a greater extent than standard care, such as cardiac rehabilitation programs and medications to lower blood pressure, reduce blood clots, or lower cholesterol.
Armin Attar of Shiraz University in Iran and his colleagues took a different approach: They used mesenchymal stem cells, which can differentiate into structural cells such as cartilage and fat. These stem cells also release molecules that reduce inflammation and stimulate regeneration of surrounding tissues.
The team collected mesenchymal stem cells from umbilical cord blood and infused them into the hearts of 136 people within three to seven days of their first heart attack. Although these stem cells can be harvested from participants’ fat and bone tissue, growing enough for an infusion can take a month, Attar says. Using those from umbilical cord blood allowed the team to administer the treatment much earlier, which could potentially improve the effects, he says. A separate group of 260 people received standard care after their first heart attack.
Three years later, those who had undergone stem cell therapy were, on average, 57 percent less likely to develop heart failure and 78 percent less likely to be hospitalized for the condition than those receiving standard care. They also saw significant improvements in the heart’s ability to pump blood, suggesting that the treatment helps heart tissue regenerate after damage.
“It’s a big step forward,” says Attar. Although the therapy did not reduce the risk of death during the study period, the fact that it reduced hospital admissions was still remarkable, says Hina Chaudhry of the Icahn School of Medicine at Mount Sinai in New York. “Heart failure is the leading cause of hospitalization in the United States,” she says.
However, 80 percent of participants were men, making it less clear the therapy’s impact on women, who are more likely to suffer heart failure after a heart attack, Chaudhry says. However, Attar and his team did not find results differing by gender in a separate analysis. The study was also limited to young adults; all participants were between 18 and 65 years old. “It would be nice to see a breakdown by age group, because younger patients simply have a more natural regenerative capacity and they recover better from heart damage,” says Chaudhry.
These results provide the best indication yet that stem cells can help restore heart function after a heart attack. But the treatment does not completely cure the heart. “There is no medicine, no therapy on this planet that can replace the people lost. [heart muscle cells]. And that’s what’s really going to be a game-changer in this area,” says Chaudhry. Still, “all of this research is telling us more about the process of heart regeneration and how to achieve it,” she says.
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