Online Extra: A Boost for Broken Hearts?
On June 6, a team of scientists will release results of a study that they believe could usher in a whole new way of treating heart disease. At a meeting for cardiologists, a surgeon from Lenox Hill Hospital in New York will describe what happened when stem cells taken from fetuses were injected into the hearts of 10 patients.
The patients in the study suffer from heart failure, a debilitating and as-yet incurable disease that afflicts 500,000 Americans. The data from the study can't be unveiled quite yet, but Barnett Suskind, CEO of the Institute of Regenerative Medicine in Barbados, believes the results will "compel us to move forward with additional work." Suskind, whose company provided funding for the study, says, "It's absolutely a milestone."
Many more studies will have to be done before this treatment is anywhere near marketable. Still, Suskind's enthusiasm underscores the growing interest in a controversial but therapeutically promising type of stem cell. So-called fetal-derived stem cells, such as those used in the recent heart study, aren't subject to the same restrictions that limit federal funding for research on embryonic stem cells. But because fetal cells are taken from aborted fetuses, they conjure up much of the emotion that has characterized the current debate in Washington. Critics of stem-cell research, in short, oppose any such research that they believe it requires the destruction of human life.
Suskind, an American entrepreneur, started his company in Barbados last year because he feared the political storm surrounding stem cells in the U.S. would make it difficult to do business in his home country. "The government here [in Barbados] has welcomed us," Suskind says. "We can conduct our work with their blessing." Although fetal cells are technically different from embryonic stem cells, "most people use the terms interchangeably, and that could present problems," he points out.
What makes fetal stem cells different from the embryonic variety is age. The former come from fetuses that are about eight weeks old. That means they're more fully developed than embryonic stem cells. Although fetal stem cells are still not fully understood, many scientists believe they might offer advantages that other stem cells don't. Embryonic cells, for example, are complete blank slates, meaning they hold the potential to turn into any type of tissue. But that flexibility is exactly makes them difficult to manipulate.
WHAT'S GOING ON?
On the other end of the spectrum are adult stem cells, which are often taken from bone marrow. These cells are already somewhat programmed, so they can turn into only a more limited variety of tissues.
Fetal stem cells may fall somewhere in between. Early studies suggest they're not quite as flexible as embryonic stem cells, yet they may be somewhat more programmable than adult stem cells. And in heart failure, that quality could be vital. Several studies have been conducted in which adult stem cells have been implanted in patients' damaged hearts. Some patients improve significantly, but others don't, and no one understands why.
Furthermore, researchers aren't quite sure what the adult stem cells turn into once they lodge in the heart. They might be morphing into blood vessels that improve blood flow through damaged tissue. In some studies, the adult stem cells seem to attach to existing heart cells and then strengthen them. But the outstanding questions -- and controversy over just how much these cells actually make patients feel better -- have left some scientists unconvinced that adult stem cells can really offer a cure for heart disease.
"A LOT TO LEARN."
Scientists who have worked on studies with Suskind's institute believe fetal cells might go one step further. "Fetal cells are younger [than adult cells], and these young cells are more powerful," says Federico Benetti, who has conducted studies of both adult and fetal stem cells in Argentina, Uruguay, and Ecuador. Benetti believes the fetal cells may be prompting new heart muscle to grow -- something no heart therapy has come close to achieving. Still, he's careful to add: "We have a lot to learn. This has opened the window to continue investigating."
Suskind says the next step will be to conduct studies that are "a little more rigorous." He can't estimate how long it will take to take to prove the therapy works, but he's confident that if the science succeeds, "the treatment will be mainstreamed very quickly."
Scientists elsewhere are also working to gain a better understanding of exactly what stem cells do once they're implanted in damaged hearts. Researchers at the University of Pittsburgh's McGowen Institute for Regenerative Medicine are especially excited about an upcoming study in which they'll implant adult stem cells in patients waiting for heart transplants. Once these patients receive their transplants, their old hearts will go to McGowen's scientists, who'll slice into the hearts, track down the implanted stem cells, literally, and study them to try to determine how they help repair damaged hearts.
"The only way to know for sure is to start taking hearts out," says McGowen's Dr. Amit Patel. It will be one small but important step in the continuing quest to put stem cells to work in healing hearts -- and to determine exactly which type of cells will prove most useful.
By Arlene Weintraub in New York