Doctors may soon be able to rejuvenate weakly
pumping hearts by creating brand-new muscle and blood vessels
fashioned from cells scavenged elsewhere in patients’ bodies, new
The idea is to repair the hearts of victims of congestive heart failure, a condition that afflicts nearly 5 million people in the United States, by recreating heart tissue damaged by heart attacks and the wear and tear of aging.
Several new reports on this approach were presented Sunday at the annual scientific meeting of the American Heart Association. Although most of the research is still being done in animals, French researchers described one attempt to patch a man’s heart using muscle gathered from his thigh.
Exciting New Science
“This is incredibly exciting new science,” commented Dr. Rose Marie Robertson of Vanderbilt University, the association’s president.
Heart failure occurs when damage to the heart muscle weakens the organ’s power to pump blood forcefully enough. Although medicines can help, many victims suffer crippling shortness of breath, lack of stamina and swelling of the legs.
In the French case, first made public last month, doctors treated a 72-year-old man with severe heart failure resulting from a heart attack, which left his main pumping chamber scarred and disabled.
Under local anesthesia, they removed a bit of muscle from his thigh, then grew it in the lab to create millions of contracting cells called skeletal myoblasts. On June 15, they transplanted 800 million of these cells with a needle into and around the heart scar.
Dr. Philippe Menasche of Bichat Hospital in Paris said the man has improved dramatically, and the new tissue in his heart is contracting rhythmically. However, the man also received a coronary bypass operation, so doctors cannot be sure how much of his change is due to the transplant.
“We repopulated the dead scar with living cells,” Menasche said. “These are encouraging results, but we have to be very, very, very cautious.”
The French doctors hope to repeat the experiment on eight more patients over the next year.
Two other approaches have been tried only in lab animals, but doctors say they could offer one important advantage: The new tissue will be real heart material, not transplanted skeletal muscle as the French used.
Dr. Ray C.J. Chiu of McGill University in Montreal reported on the use of immature bone marrow tissue called marrow stromal cells. These have the ability to transform into many different body parts, including nerves and liver as well as heart.
His team injected marrow stromal cells in the hearts of 22 genetically identical rats. Chiu said the new tissue quickly began to work with the original heart cells, beating in unison.
Growing New Blood Vessels
“They were hard to distinguish,” he said.
In Boston, Dr. Jeffrey Isner from St. Elizabeth’s Hospital used a similar approach to help hearts grow new blood vessels. Arteries are constructed from tissue called endothelial cells. Immature versions of these cells circulate in the bloodstream.
Using rats, the Boston researchers gathered these immature endothelial cells, grew them in test tubes to make millions of copies and then injected them into the areas of damaged heart muscle. The animals’ hearts grew new blood vessels and appeared to work better than hearts without the treatment.
None of these approaches use embryonic stem cells, which some oppose on ethical grounds. Another advantage is that they use tissue taken from the patient’s own body, so there is no risk of rejection or need for drugs to suppress immune system defenses.
However, none of these treatments is likely to be as simple as it seems. For instance, Chiu cautioned that the marrow stromal cells tend to develop like the tissue they are placed next to. So in a damaged heart, they could form new scar tissue.
Chiu said it may be possible to nudge cells with drugs to develop into particular cell types, such as contracting muscle cells, despite being implanted next to scar material.