Published Feb. 27, 2023 3:30 p.m. ET

Cell therapy, involving adult stem cells from bone marrow, has been shown to reduce the risk of heart attack and stroke in severe heart failure patients, according to a new study.

A single administration of adult stem cells directly into an inflamed heart, through a catheter, could result in a long-term 58 per cent reduced risk of heart attack or stroke among heart failure patients with reduced ejection fraction, meaning they have a weakened heart muscle, suggests the study, published Monday in the Journal of the American College of Cardiology.

The study is being called the largest clinical trial of cell therapy to date in patients with heart failure, a serious condition that occurs when the heart can't pump enough blood to meet the body's needs.

"We followed these patients during several years -- three years -- and what we found was that their hearts got stronger. We found a very significant reduction in heart attack and stroke, especially in the patient that we measured in their blood that they had more inflammation going on," said the study's lead author Dr. Emerson Perin, a practicing cardiologist and medical director at The Texas Heart Institute in Houston.

"That effect, it was there across everyone, but for the patient that had inflammation, it was even more significant," Perin said. "And there also is evidence that we had a reduction in cardiovascular deaths."

The therapy involves injecting mesenchymal precursor cells into the heart. These particular stem cells have anti-inflammatory properties, which could improve outcomes in heart failure patients since elevated inflammation is a hallmark feature of chronic heart failure.

More than 6 million adults in the United States have chronic heart failure, and most are treated with drugs that address the symptoms of the condition. The patients included in the new study were all taking medications for heart failure, and the new research suggests that cell therapy can be beneficial when used in conjunction with heart failure drugs.

"You can imagine, we keep everybody going and doing better with the medicine. And now we have a treatment that actually addresses the cause and quiets everything down. So, this line of investigation really has a great future and I can see that, with a confirmatory trial, we can bring this kind of treatment into the mainstream," Perin said.

"We can treat heart failure differently," he said. "We have a new weapon against heart failure and this study really opens the door and leads the way for us to be able to get there."

The new study -- sponsored by Australian biotechnology company Mesoblast -- included 565 heart failure patients with a weakened heart muscle, ages 18 to 80. The patients were screened between 2014 and 2019 and randomly assigned to either receive the cell therapy or a placebo procedure at 51 study sites across North America.

The patients who received the cell therapy were delivered about 150 million stem cells to the heart through a catheter. The cells came from the bone marrow of three healthy young adult donors.

The researchers, from The Texas Heart Institute and other various institutions in the United States, Canada and Australia, then monitored each patient for heart-related events or life-threatening arrhythmias.

Compared with the patients who received a sham procedure, those treated with the stem cell therapy showed a small but statistically significant strengthening of the muscle of the heart's left pumping chamber within a year.

The researchers also found that the cell therapy decreased the risk of heart attack or stroke by 58 per cent overall.

"This is a long-term effect, lasting an average of 30 months. So that's why we're so excited about it," Perin said.

Among patients with high inflammation in their bodies, the combined reduced risk of heart attack or stroke was even greater, at 75 per cent, the researchers found.

"These cells directly address inflammation," Perin said.

"They have little receptors for these inflammatory substances -- some of them are called interleukins, and there's other kinds," he said. "When you put them into an inflamed heart, it activates the cells and the cells go, 'Wow, we need to respond. This house is on fire. We need to put out the fire.' And so they then secrete various anti-inflammatories."

The researchers wrote in their study that their findings should be considered as "hypothesis generating," in that they show this cell therapy concept could work, but clinical trials would be needed to specifically confirm the effects of these stem cells on heart attack, stroke and other events. It is still unclear for how long the effects of the stem cell therapy last beyond 30 months and whether patients will need more stem cell injections in the future.

Overall, there were no major differences between the adverse events reported among the patients who received the cell therapy compared with those in the control group, and the researchers reported no major safety concerns.

"We've made an enormous step to be able to harness the real power of adult stem cells to treating the heart," Perin said. "This trial really is a signal of a new era."

For more than a decade, scientists have been studying potential stem cell therapies for heart failure patients -- but more research is needed to determine whether this treatment approach could reduce the amount of hospitalizations, urgent care events or complications among patients with heart failure.

The new study didn't find that, said cardiologist Dr. Nieca Goldberg, medical director of Atria New York City and clinical associate professor of medicine at NYU Grossman School of Medicine, who was not involved in the latest study.

What the new study did find is that "there may be a population of people that could benefit from the stem cell therapy, particularly people who have inflammation," Goldberg said.

"It's actually an interesting therapy, an interesting thing to consider, once more research substantiates its benefit. Because in heart failure, there's multiple things going on and, particularly for the inflammatory component, this could be an interesting treatment," she said. "It might have some role in heart failure patients with inflammation."

The therapy's effects on heart attack or stroke risks "were positive," Dr. Brett Victor, a cardiologist at the Cardiology Consultants of Philadelphia, who was not involved in the study, said in an email.

"Specifically, patients who received the stem cell therapy were less likely to have a heart attack or stroke over the next 2.5 years, especially among those who were found to have a high degree of systemic inflammation as measured by a laboratory test," Victor said in the email, adding that this represents how heart failure has a significant inflammatory component.

Those "positive signals" likely will be evaluated more in subsequent studies, Victor said.

"Current therapies for heart failure including lifestyle modifications, a growing list of excellent medications, and device therapies will continue to be the standard of care for treatment in the near-term," he said. "I suspect that this trial will continue to move the field forward in studying cardiac cell therapy as we continue to look for ways to not just treat, but actually find a cure for this disease."

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