WEDNESDAY, Aug. 1, 2001 (HealthDayNews) -- Israeli scientists say they've turned stem cells from human embryos into heart muscle, a feat that eventually could lead to new treatments for heart failure.
"It's a little bit far from clinical application," says Dr. Joseph Itskovitz-Eldor, a stem-cell expert and study co-author. "But this is the first time that it was demonstrated that human embryonic stem cells can actually make or differentiate into cardiac muscle, which is similar to the normal early stage of young cardiac muscle that you can find in the human."Scientists had long thought adult heart cells wouldn't regenerate. However, new research shows heart muscle can make itself anew, though in quantities so small it doesn't make a difference, experts say.
Although heart transplants have been the best hope for patients whose pumps fail, the number of donor organs available doesn't begin to meet demand. However, several recent discoveries could reduce, or even eliminate the need for replacement hearts.
Studies have shown fetal heart cells can help restore function to diseased adult heart tissue. But the controversial source of these cells makes such a therapy impractical. Stem cells derived from embryos outrage religious conservatives since the embryos must be destroyed to harvest the highly versatile tissue, a practice they equate with abortion.
Istkovitz-Eldor helped create the first line of human embryonic stem cells three years ago, and his group used cells from that initial breakthrough for the latest work. The findings appear in the August issue of the Journal of Clinical Investigation.
In the latest experiment, conducted at Technion-Israel Institute of Technology's Rambam Medical Center in Haifa, the researchers grew bunches of stem cells and put them in a culture medium to further encourage their development.
As they grew, roughly 10 percent of the cells gathered in clusters that began to show cardiac properties. They contracted like heart muscle, had similar genes and proteins, had telltale electrical activity and responded to the hormone adrenaline by speeding up, a well-known trait of heart tissue.
"They possess all the characteristics necessary for heart cells," says co-author Dr. Lior Gepstein. "They look like very early cardiac cells, which is good because probably they will have a better chance to regenerate the heart."
The obvious application would be to seed diseased hearts with fresh, healthy cells, Gepstein says. That will require experiments first in animals and then, if successful, in humans. And a number of other hurdles stand in the way.
The current method of producing the cells is inefficient, so new techniques to grow them must be found, Gepstein says. Nor is it clear whether the grafted tissue would take hold, or whether the cells would work in tune with the full heart's beating.
Even if all that fails, the cultured tissue could be extremely useful for scientists hoping to create new drugs to fight heart failure, Gepstein says: "We don't have human tissue to use to test what a drug does to the heart."
Dr. Piero Anversa, a cardiologist at New York Medical College in Valhalla, has shown stem cells derived from adult bone marrow can improve heart function in mice after a heart attack.
Anversa says he has "no intention of utilizing embryonic stem cells, because adult stem cells seem to do the work for the heart." On the other hand, "I have nothing against the use of embryonic stem cells," which may be better for other organs and illnesses, he says.
The American Heart Association has endorsed the use of stem cells, including those derived from human embryos, and supports federal funding for such research. Even so, the association decided to limit its own funding for research to animal stem cells and those pulled from adult human tissue.
"The board and both its scientists and lay members are impressed by the potential benefits that could be derived from stem cell research, and of course, our mission is to reduce death and disease from heart disease and stroke," says Dr. Rose Marie Robertson, a past association president.
An estimated 4.6 million Americans suffer heart failure, many because their cardiac cells are scarred after heart attacks, Robertson says.
"The concept that you could provide them with functional beating heart muscle is certainly exciting," she adds.
What To Do
President George W. Bush is weighing whether to allow government money to fund research on embryonic stem cells, which can be coaxed into becoming virtually any tissue in the body.
To learn more about stem cells, try the National Institutes of Health.
For more on heart disease, check the American Heart Association.