A large clinical trial has shown that infusing mesenchymal stem cells from umbilical cord blood shortly after a first heart attack reduces the risk of developing heart failure by nearly 60 percent over three years. The treatment, administered within three to seven days, also improved heart pumping function compared to standard care. Researchers from Shiraz University in Iran led the study, providing strong evidence for stem cells' regenerative potential.
Heart attacks cause permanent damage to cardiac muscle, often leading to heart failure, where the heart cannot pump sufficient blood. No treatments currently restore function beyond transplants or pumps. Stem cell therapy has been explored as a regenerative option, though prior studies yielded mixed results. A 2020 trial with 375 participants using bone marrow-derived stem cells did not reduce death risk more than standard care, which includes medications for blood pressure, clots, and cholesterol, plus rehabilitation.
In the latest trial, Armin Attar at Shiraz University and colleagues used mesenchymal stem cells, which can become structural cells like cartilage and fat, and release anti-inflammatory molecules to aid regeneration. They sourced cells from umbilical cord blood for quick preparation—unlike patient-derived cells, which take a month to culture—and infused them into 136 patients aged 18 to 65 within three to seven days of their first heart attack. A control group of 260 patients received standard care.
After three years, the stem cell group was 57 percent less likely to develop heart failure and 78 percent less likely to be hospitalized for it. They also showed significant improvements in the heart's blood-pumping ability, indicating tissue regeneration. The therapy did not reduce overall death risk during the study.
"This is a great step forward," says Attar. Hina Chaudhry at the Icahn School of Medicine at Mount Sinai notes the hospitalization reduction's importance, as heart failure leads U.S. hospitalizations. However, 80 percent of participants were men, and all were relatively young; women, who face higher heart failure risk post-attack, and older patients may respond differently, though gender analysis showed no outcome differences.
The results, published in The BMJ (DOI: 10.1136/bmj-2024-083382), strengthen evidence for stem cells in cardiac repair but do not fully heal the heart. "There is no drug, no therapy on this planet that replaces those lost [heart muscle cells]," says Chaudhry, adding that such research advances understanding of heart regeneration.