In one study, direct injections of stem cells into injured heart muscle helped people with heart failure to breathe better, walk farther, and generally feel better, says Nabil Dib, MD, director of clinical cardiovascular cell therapy at the University of California San Diego.
In a second study, people who got infusions of stem cells within a week of a heart attack had better heart function and fewer potentially life-threatening irregular rhythms than those who didn't get the treatment, says Joshua Hare, MD. Hare is professor of medicine and director of the Interdisciplinary Stem Cell Institute at the University of Miami's Miller School of Medicine.
Stem cells are at an early stage of maturation and therefore have the potential to become many different types of cells, including those in the heart muscle.
Both studies, reported here at the annual meeting of the American College of Cardiology conference, used adult stem cells, not the more controversial embryonic stem cells.
Stem Cells Taken From Bone Marrow
Dib studied 23 people with end-stage heart failure, a condition in which the heart is unable to pump blood properly and keep up with the body's demand. The cause of these patients' heart failure was coronary artery disease.
The participants were the sickest of the sick. They failed to respond to medication and for one reason or another could not be helped by bypass surgery or angioplasty procedures. Many could barely walk across the room without panting.
The researchers extracted stem cells from the thigh muscles of 12 of the participants, grew the cells in a lab, and injected them directly into oxygen-deprived -- or ischemic -- areas of the heart muscle through a catheter. The other 11 participants were given standard drug therapy.
Minimally Invasive Procedure
After six months, patients who had received the stem cell injections had significant improvements in heart function and quality of life, while those who had standard drug therapies worsened.
The stem cell treatment also improved the heart's ability to pump blood and restored blood flow to oxygen-starved heart muscle, he says.
"Their enlarged hearts decreased in dimension, while in the people on drug therapy, the heart continued to get bigger," he says.
Dib says one of the most notable aspects of the stem cell treatment is how minimally invasive it is. "The patient is awake during the procedure and can go home within 24 hours," he says.
And since the stem cells are taken from the patient's own body, there is minimal risk of rejection, Dib says.
Heart Failure Options Needed
If the research pans out in larger studies, "the quality of life and survival of heart failure patients will be improved," Dib says. "This will be a milestone in medicine."
William O'Neill, MD, executive dean for clinical affairs at the Miller School of Medicine at the University of Miami and moderator of a news conference on the findings, says that new options are desperately needed for heart failure.
In the U.S, 2 million people are admitted to the hospital with heart failure each year, and almost 500,000 die.
"I was surprised and encouraged by these results," O'Neill tells WebMD, though much further study is needed.
Dibs says he plans to start a larger study after this year.
Using Stem Cells From Unrelated Donors
For the second study, Hare and colleagues took muscle stem cells from unrelated donors, not the patients themselves.
And rather then being injected right into the heart, the stem cells were infused intravenously into 53 people within 10 days of a heart attack. Another 53 heart attack survivors were given saline injections.
After six months, heart and lung function was significantly better in the people who got the stem cell infusions than in those who got saline shots. "They were also doing better from a clinical point of view," Hare says.
Hare notes that there was a lot of concern in the medical community that using cells from an unrelated donor would cause a rejection reaction. But people who got stem cells actually had fewer side effects than those who got sham injections, he says.
An advantage to using cells from donors is that they could potentially be grown in large quantities in the lab and stored and administered like an off-the-shelf drug, he says.
Hare says that contrary to what the researchers had thought when they started the work, the stem cells do not turn into heart muscle cells.
"Rather, the heart is capable of healing itself," he says. "The stem cells somehow stimulate in a multiprong fashion those processes compromised in a heart attack and improve blood flow to damaged areas."