Microscopic embryonic stem cells might hold the answer to afflictions from baldness, wrinkles, and age spots to the most intractable diseases.
Or they might be a medical mirage, a tempting oasis of healing on a horizon that never grows closer.
This fall, as entities ranging from California to the United Nations prepare to make major decisions about the future of stem-cell research, American public opinion has swung strongly in favor of the technology. But just as medical research has created breakthroughs in physical treatments, it has also led doctors - and the public - down blind alleys.
It's not yet clear which path stem-cell research will follow. It is, however, certain that it will spark more political fireworks than any medical technology in at least a quarter century.
"Americans love medical technology," says Robert Blendon, a professor of health policy and management at Harvard University who tracks public attitudes toward medicine. But embryonic stem cells have become linked to the abortion debate - "the single biggest, most contentious issue in American society," he adds. That alone makes the issue unique.
To be sure, those in the field are pretty sure they're onto something exciting. "There's absolutely nothing we've seen so far to suggest that this cannot be done," Dr. Douglas Melton, a leading stem-cell researcher at Harvard University, said at an international conference on stem-cell research in Boston in June.
But others remember a cautionary tale from the mid-1990s: "gene therapy" aimed at replacing, manipulating, or supplementing human genes that were not working with healthy genes.
"When it [gene therapy] was first proposed, it was going to be the way to fix everything," says Josephine Johnston, a bioethicist at the Hastings Center, a nonprofit bioethics research institute in Garrison, N.Y. Advocates announced that treatments based on genetic manipulation would be available no later than the turn of the millennium. But by 2004, not one had reached the market, while many human test subjects had suffered adverse effects. Several died.
For the moment, US public opinion is moving in favor of stem-cell research, especially after pleas from the wife and son of former President Reagan, whose battle with Alzheimer's disease raised the question whether the nascent technology might have provided a cure.
The swing in the polls is a boon for proponents, because major decisions about the technology's future loom. In October, the United Nations General Assembly is expected to vote whether to adopt a ban on all human cloning, backed by the Bush administration. Or it might ban only reproductive cloning and allow so-called therapeutic cloning, which creates stem cells.
On Nov. 2, Californians will vote on a ballot initiative to provide $3 billion in state funds for stem-cell research. Proponents, including billionaire Bill Gates, have contributed more than $10 million to push its passage, suggesting that it will be a boon to the state and lead to breakthroughs that the federal government has refused to underwrite.
Supported by antiabortion advocates, the Bush administration has restricted federal funds for embryonic stem-cell research to a series of stem-cell lines created before Aug. 9, 2001. (Scientists are also studying stem cells from adults and the blood from the umbilical cords of newborns. While showing promise, these may have limited therapeutic abilities.) Fewer than 20 of the original 78 embryonic stem-cell lines have proven useful to scientists, who argue they need access to many, many more to conduct meaningful research.
Opponents of therapeutic cloning, which uses cells from human embryos, say it amounts to murder because the embryos are destroyed in the process.
These embryonic stem cells can grow into all types of cells and tissues found in the body. Scientists say if they learn how to direct their growth, stem cells could be used to combat a host of intractable diseases.
Those who see a bright future for stem cells don't look to gene therapy but to in vitro fertilization (IVF) as a possible model. On July 25, 1978, Louise Brown became the first baby born using the then-controversial technique, in which conception takes place outside the womb. Critics called IVF unnatural, dangerous, and a threat to family life. But in the following quarter century, IVF has become widely used and accepted and now is considered a relatively safe medical procedure.
Ironically, IVF produces excess human embryos that clinics routinely destroy. Yet there has been little public outcry "because that technology is so popular that it would be political suicide to try to close in vitro fertilization clinics," says Arthur Caplan, director of the Center for Bioethics at the University of Pennsylvania in Philadelphia. There may be some 400,000 such embryos in clinics around the world.
The IVF experience suggests that religious and moral opposition to embryonic stem-cell research might fade only after it produces a useful therapy.
However hard it is to gauge the probability of success, many people are already weighing the costs of research against potential benefits. Besides California voters deciding whether to invest in stem cells, venture capitalists are backing a number of biotech firms. The lure of finding a miraculous healing agent makes the investment attractive.
"I can find no example where over the long term we have not moved ahead for research for cures of major diseases," says Dr. Blendon at Harvard. When people are polled about stem cells, he says, if the question mentions that the research might produce cures for well-known diseases, the number of people who say they support it zooms to a strong majority.
The potential for stem cells "is enormous," but there are countless twists and turns left on the path to harnessing them, adds Ann Parson, author of the new book "The Proteus Effect: Stem Cells and Their Promise for Medicine." "The amount of biology that we have to learn to turn that embryonic stem cell into a cell of one's choosing is huge. I personally wonder if it's not going to take one or two life times to see."
"There's a sort of idea in science that if you search long enough and hard enough, you'll find a solution to everything, especially in medicine," bioethicist Johnston says. "But that doesn't always pan out." She sees some parallels between the promise of stem cells and the search for an AIDS vaccine that after two decades remains undiscovered.
• Embryonic stem cells form in the first days after conception and eventually turn into all the cells, tissues, and organs in the human body. Scientists hope to use these in the treatment of a wide range of ailments.
• Adult stem cells - donated by humans - are extracted from bone marrow or umbilical blood and have been used to fight disease for many years.
• By one count, 24 countries have flexible or permissive laws on embryonic stem cells, including China, Russia, Japan, France, and the United Kingdom.
• In November, voters in Switzerland and California will vote on measures to regulate or support such research.
Source: William Hoffman