Stem cells safely heal damaged hearts
JOHNS HOPKINS (US) — Stem cells can be used safely to repair damaged heart muscle, reducing scar tissue and improving quality of life for patients with chronic heart failure.
Published in the Journal of the American Medical Association, the results were positive whether the stem cells were derived from the patients’ own bone marrow or from someone else’s. For many of the 31 patients, therapy also enhanced the heart’s pumping ability.
This is the first study in heart disease patients to compare the use of autologous stem cells, derived from a patient’s own bone marrow, with allogeneic stem cells, from healthy volunteers. The advantage of allogeneic cells is the potential for an off-the-shelf therapy that could be delivered quickly, without extracting bone marrow from heart failure patients followed by cell processing.
All the study’s patients had longstanding ischemic cardiomyopathy, caused by a heart attack that blocked blood flow to the heart and damaged heart muscle. The condition affects about 70 percent of the 6 million people in the United States who suffer from heart failure.
“The primary focus of our study was to determine the safety of the therapy, specifically within 30 days of the treatment,” says Gary Gerstenblith, professor of medicine at Johns Hopkins University and a co-author. “We found that the treatment was safe and also that many of the patients experienced significant improvement, whether they had received the allogeneic or the autologous stem cells.”
Patients were randomly selected to have either their own stem cells or donated cells injected directly into heart muscle. They were monitored for treatment-associated complications, such as death, heart attack, stroke, hospitalization for worsening heart failure, and dangerous heart arrhythmias. All the patients were still alive 12 months after treatment.
Researchers were especially interested in learning whether the patient’s immune system would recognize the donated stem cells as foreign and mount an immune response to reject them. Only 3.7 percent of the patients receiving donated cells had such a response.
The particular cells used for the therapy, mesenchymal stem cells, are less likely to stimulate an immune response and rejection than most other stem cells. They have the ability to repair muscular tissues and to reduce inflammation.
Patients in the allogeneic and autologous groups were further divided according to the doses of the stem cells they received. Three doses were tested: 20 million cells, 100 million cells, and 200 million cells.
“We generally think the more the better, but in fact, the lowest dose of 20 million cells appeared to be the most effective at improving the heart’s pumping ability as well as reducing the extent of scar tissue,” says co-author Peter Johnston, assistant professor of medicine at Johns Hopkins.
Both types of stem cells reduced scar tissue. Scars can impede normal heart functioning and increase the risk of rhythmic abnormalities. The size of many patients’ hearts became more normal, reversing enlargement that occurs as heart failure worsens.
After stem cell therapy, many patients were able to go farther on a six-minute walking test and reported an improved quality of life.
“In many cases, we observed clinically significant improvement,” says Joshua Hare, director of the Interdisciplinary Stem Cell Institute at the University of Miami Miller School of Medicine and lead author of the study. “Even in patients who had heart attacks several decades before treatment, both donor and recipient stem cells reduced the amount of scarring substantially.”
“The results are very encouraging,” Johnston says, “because our current therapies are aimed at decreasing the heart’s workload and making patients feel better, but none can truly repair the heart or reverse the damage caused by heart attacks.”
The next steps, according to Gerstenblith, are to conduct studies comparing the therapy with a placebo and learn whether repeated doses result in better outcomes, as well as to study the safety and effectiveness of stem cell therapy in patients with other causes of heart failure.
“The findings of our study strongly support ongoing development of allogeneic stem cell therapy for the increasing number of patients with advanced heart failure,” says Gerstenblith.
Source: Johns Hopkins University
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