In what many are calling a breakthrough, an international team of scientists for the first time has produced human embryonic stem cells genetically matched to specific people diagnosed with diseases. They hope the advance will one day lead to growing replacement tissue to treat specific maladies.
The technique, which involves cloning, will find its most immediate use as a powerful research tool, scientists say. An enormous amount of work remains to be done to determine if embryonic stem cells can be used to treat injuries or illnesses.
While the announcement is being hailed as a major breakthrough, it also will heighten the ethical tension over how far and how fast the science community should be allowed to go in cloning for research and therapeutic purposes.
Still, the importance of the results can't be underestimated, notes Konrad Hochedlinger, a stem-cell scientist at the Whitehead Institute for Biomedical Research in Cambridge, Mass.
"This is a proof of principle for therapeutic cloning," he says, referring to the process of implanting a patient's genetic "blueprint" in a donor's egg to produce patient-specific stem cells for the purpose of finding a cure.
The latest results are likely to recharge and broaden the political and social debate in the US over the ethics of cloning and embryonic stem-cell research. The country is still at odds over whether human cloning should be permitted for research purposes. Moreover, extracting embryonic stem cells destroys the primitive embryos that produce them.
Thus the ethics of using embryonic stem cells for any purpose pits people who are convinced that human life begins at the moment of conception against those who disagree and see moral worth in exploring human embryonic stem cells' potential for understanding human development and the development and treatment of diseases.
Beyond the "should we, shouldn't we" argument, however, lie emerging issues. The new results highlight the need for clear standards regarding ethical treatment of women who donate eggs for the procedure, a need to find common ground on ethical research standards across borders, and a need to be clear with donors and research subjects that an enormous gulf remains between basic science and any potential future therapies.
These issues are likely to echo under the Capitol dome next week. The US House of Representatives is expected to vote on a bipartisan measure that would allow federally funded researchers to use discarded embryos from fertility clinics to develop new stem-cell lines. The bill, which some analysts say is likely to pass, would reverse President Bush's decision in May 2001 to ban this source of stem cells. His decision limited federally funded scientists in the US to a small number of preexisting stem-cell lines for research - a number researchers argue is far too small to yield meaningful advances. The ban has prompted universities and states such as California to set up funding approaches for human embryonic stem-cell research independent of the federal government to allow scientists a freer hand at selecting source material for their work.
Stem cells are produced in the earliest stages of an embryo's development. With the right triggers, this single type of cell transforms itself into any of three broad categories of embryonic cell types. These, in turn, give rise to the more than 200 different cell types in a human body.
The mostly South Korean research team began by extracting DNA from the skin cells of people diagnosed with diseases or injuries for which stem cells have been proposed as potential treatments. The DNA was implanted in eggs donated by women who had given informed consent. The eggs had been cleared of their original DNA. The eggs were fertilized in the lab and allowed to reach the embryonic stage where stem cells emerge.
The results, reported in Friday's edition of the journal Science, appear to clear several hurdles along the path to stem-cell therapies, according to Gerald Schlatten, vice-chairman of research development at the University of Pittsburgh's department of obstetrics, gynecology, and reproductive sciences. The stem cells were not just tailored to the patients genetically; they also were matched in ways that would prevent a patient's immune system from rejecting any tissue the stem cells might be used to generate. In addition, the process is substantially more efficient. Last year, the same team, led by Woo Suk Hwang of Seoul National University, produced the first cloned human stem-cell line last year, but required 242 eggs to do it. This time, they averaged one cell line for every 17 eggs. This increased efficiency, Dr. Schlatten notes, means fewer donors need to undergo the egg-harvesting procedure, which researchers and ethicists say can carry its own physical risks. And because the team used human cells to nourish the stem cells in the petri dish, rather than the usual rabbit cells, the approach could reduce the risk of having animal illnesses "jump" to a patient.
Indeed, the paper published Friday contains enough incremental but important results to have generated another half-dozen Science papers, Schlatten adds.
"This represents a real tour de force," concludes John Gearhart, a professor of medicine at the Johns Hopkins University in Baltimore. "They were able to do all this in less than a year."
But the speed for researchers remains a challenge for policymakers, at least in the US. In a report released Thursday, the Johns Hopkins-affiliated Genetics and Public Policy Center lays out issues surrounding the gridlock.
"Science often advances more quickly than the public and policymakers do," says Kathy Hudson, the center's director. "We're at loggerheads in Congress. We have have state laws that are all over the map. And the international situation is moving very quickly."
Whether this gridlock will end anytime soon remains unclear. "It's too early to tell," she says.