New Cells For Ailing Hearts
N E W O R L E A N S, Nov. 13, 2000 -- 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
research suggests.
The idea is to repair the hearts of victims of congestive heartfailure, a condition that afflicts nearly 5 million people in theUnited States, by recreating heart tissue damaged by heart attacksand the wear and tear of aging.
Several new reports on this approach were presented Sunday atthe 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 heartusing muscle gathered from his thigh.
Exciting New Science
“This is incredibly exciting new science,” commented Dr. RoseMarie Robertson of Vanderbilt University, the association’spresident.
Heart failure occurs when damage to the heart muscle weakens theorgan’s power to pump blood forcefully enough. Although medicinescan help, many victims suffer crippling shortness of breath, lackof stamina and swelling of the legs.
In the French case, first made public last month, doctorstreated a 72-year-old man with severe heart failure resulting froma heart attack, which left his main pumping chamber scarred anddisabled.
Under local anesthesia, they removed a bit of muscle from histhigh, then grew it in the lab to create millions of contractingcells called skeletal myoblasts. On June 15, they transplanted 800million of these cells with a needle into and around the heartscar.
Dr. Philippe Menasche of Bichat Hospital in Paris said the manhas improved dramatically, and the new tissue in his heart iscontracting rhythmically. However, the man also received a coronarybypass operation, so doctors cannot be sure how much of his changeis due to the transplant.
Encouraging Results
“We repopulated the dead scar with living cells,” Menaschesaid. “These are encouraging results, but we have to be very,very, very cautious.”
The French doctors hope to repeat the experiment on eight morepatients over the next year.
Two other approaches have been tried only in lab animals, butdoctors say they could offer one important advantage: The newtissue will be real heart material, not transplanted skeletalmuscle as the French used.
Dr. Ray C.J. Chiu of McGill University in Montreal reported onthe 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 22genetically identical rats. Chiu said the new tissue quickly beganto 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 useda similar approach to help hearts grow new blood vessels. Arteriesare constructed from tissue called endothelial cells. Immatureversions of these cells circulate in the bloodstream.
Using rats, the Boston researchers gathered these immatureendothelial cells, grew them in test tubes to make millions ofcopies and then injected them into the areas of damaged heartmuscle. The animals’ hearts grew new blood vessels and appeared towork better than hearts without the treatment.
None of these approaches use embryonic stem cells, which someoppose on ethical grounds. Another advantage is that they usetissue taken from the patient’s own body, so there is no risk ofrejection or need for drugs to suppress immune system defenses.
However, none of these treatments is likely to be as simple asit seems. For instance, Chiu cautioned that the marrow stromalcells tend to develop like the tissue they are placed next to. Soin a damaged heart, they could form new scar tissue.
Chiu said it may be possible to nudge cells with drugs todevelop into particular cell types, such as contracting musclecells, despite being implanted next to scar material.