Mesenchymal stem cells labeled with fluorescence molecules
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People who received an infusion of stem cells shortly after a heart attack were less likely to develop heart failure than those treated with standard care, according to the largest such trial to date. The finding provides some of the strongest evidence yet that stem cells can help the heart repair itself.
After a heart attack, cardiac muscle is permanently damaged and weakened, which often leads to heart failure – when the organ can’t pump enough blood to meet the body’s demands. Currently, there is no treatment short of a transplant or heart pump that can restore cardiac 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 investigating their use after a heart attack have shown mixed results. For instance, a 2020 trial involving 375 people found bone marrow-derived cells, including stem cells that develop into blood cells, failed to lower the risk of death to a greater degree than standard care, such as cardiac rehabilitation programmes and medications to lower blood pressure, reduce blood clots or decrease cholesterol.
Armin Attar at 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 spur surrounding tissues to regenerate.
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. While these stem cells could be taken from participants’ own fat and bone tissue, culturing enough of them for an infusion can take a month, says Attar. Using those from umbilical cord blood allowed the team to administer the treatment much sooner, potentially enhancing the effects, he says. A separate group of 260 people received standard care after their first heart attack.
Three years later, those who underwent stem cell therapy were, on average, 57 per cent less likely to develop heart failure and 78 per cent less likely to be hospitalised for the condition than those receiving standard care. They also saw significant improvements in the heart’s ability to pump blood, suggesting the treatment helps heart tissue regenerate after damage.
“This is a great step forward,” says Attar. While the therapy didn’t reduce the risk of death during the study period, the fact it lowered hospital admissions is still notable, says Hina Chaudhry at the Icahn School of Medicine at Mount Sinai in New York. “Heart failure is the leading cause of hospitalisation in the US,” she says.
However, 80 per cent of the participants were men, making it less clear how the therapy affects women, who are more susceptible to heart failure after a heart attack, Chaudhry says. However, Attar and his team didn’t find outcomes differed by gender in a separate analysis. The study was also limited to younger adults; all of the participants were between 18 and 65 years old. “It would be good to see a breakdown of age groups because younger patients just have more natural regenerative ability, and they recover better from heart damage,” says Chaudhry.
These results are the strongest indication yet that stem cells can help restore cardiac function after a heart attack. But the treatment doesn’t heal the heart entirely. “There is no drug, no therapy on this planet that replaces those lost [heart muscle cells]. And that is what is really going to be a game changer in the field,” says Chaudhry. Still, “all of this research is teaching us more about the regenerative process in the heart and how to get there”, she says.
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