Gene Therapy Shows Early Promise for Heart Failure
Injecting a protein known to recruit stem cells may help repair damaged heart muscle, researcher says
THURSDAY, Feb. 21, 2013 (HealthDay News) -- When it comes to treating heart failure, the ultimate hope is to develop a therapy that repairs the damaged heart muscle.
Now, an early study hints at a way to do that by harnessing the body's natural capacity for repair.
Heart failure is a chronic, progressive condition where the heart cannot pump blood efficiently enough to meet the body's needs, which leads to problems like fatigue, breathlessness and swelling in the legs and feet. Most often, it arises after a heart attack leaves heart muscle damaged and scarred.
In the new study, researchers were able to use gene therapy to modestly improve symptoms in 17 patients with stage III heart failure -- where the disease is advanced enough that even routine daily tasks become difficult.
What is novel about the tactic, the researchers said, is that the gene therapy is designed to attract the body's own stem cells to the part of the heart muscle that's damaged. The hope is that the stem cells will then get some repair work done.
The findings, published Feb. 21 in the journal Circulation Research, are preliminary, and much more research needs to be done.
"This is a proof-of-concept study," explained lead researcher Dr. Marc Penn, a professor at Northeast Ohio Medical University in Rootstown, and director of research at Summa Cardiovascular Institute in Akron. But Penn and other heart failure experts said they were cautiously optimistic about the therapy's potential for at least some patients.
Stem cells are primitive cells that can develop into different types of body tissue. Adults have the cells in their bone marrow, and they give rise to blood cells. Researchers have also found that individual organs in the body, including the heart, have their own pools of stem cells.
Those stem cells may try to repair damaged tissue, but they are not all that successful, Penn said. So his team sought to give the stem cells a helping hand. They infused patients' heart muscle with three different doses of a drug that carried a gene for SDF-1, a natural protein in the body believed to recruit stem cells to sites of tissue damage.
Lab research has suggested that after a heart attack, SDF-1 activity in the heart goes up -- but only for a short time, Penn said. The goal of the experimental therapy is to enhance SDF-1 and draw more stem cells to where they are needed.
The initial results are promising, Penn said. The approach seemed safe, with no major side effects linked to the treatment. Two of the study patients died within a year, but the deaths were deemed not to be connected to the treatment.
Among the 15 patients who were alive one year later, there were improvements in their symptoms and walking ability.
Those gains, however, were "modest," and need to be viewed with some caution, said Dr. Lee Goldberg, medical director of the Heart Failure and Cardiac Transplant Center at the University of Pennsylvania in Philadelphia.
Goldberg pointed out that early studies like this one are set up primarily to see if a therapy is safe, and to figure out what drug dose to use in larger trials -- not to test effectiveness.
"A major limitation of the study is that there was no placebo group," said Goldberg, who also chairs the American College of Cardiology's Heart Failure and Transplant Council. That means there's no way of knowing whether some study patients were showing a "placebo effect" -- the phenomenon where people feel or even function better simply because they believe they received an effective treatment.
Penn said his team is working on a next-stage trial of 90 patients, which will include a group that receives a placebo.
Another cardiologist agreed that the findings on the therapy's benefits have to be "taken with a grain of salt."
"But I do think this seems feasible, and worth studying further," said Dr. David Friedman, chief of heart failure services at North Shore-LIJ's Plainview Hospital, in Plainview, N.Y.
Researchers have long sought to use stem cells to repair diseased hearts, which has included taking stem cells from heart failure patients' bone marrow and infusing them into the heart.
But this new approach, Friedman said, would avoid the steps of harvesting, culturing and reintroducing stem cells into patients. And, according to Penn, it should also be less costly.
For now, though, Goldberg said, "there are many, many unanswered questions. How durable will these effects be? Are there any unintended side effects in the long term?"
It's also not certain that the gene therapy did, in fact, recruit patients' stem cells to their damaged hearts. The researchers could not measure that directly.
Even with all the uncertainties, Goldberg said it's exciting to see that this approach could be feasible. "I am cautiously optimistic," he said.
One thing everyone agreed on was that the ultimate hope is to develop heart failure therapies that somehow rehabilitate damaged heart muscle. Right now, heart failure treatment involves drugs and lifestyle changes that relieve symptoms and ease the workload on the heart. But the disease does ultimately progress, until patients eventually need implanted devices or, as a last resort, a heart transplant.
Penn is the founder of Juventas Therapeutics Inc., which is developing SDF-1-based therapies for heart failure and other diseases.
Learn more about heart failure from the U.S. National Heart, Lung, and Blood Institute.