With each new discovery, stem cell researchers have learned to provide perspective and context to help a hopeful public and those eager to find alternatives to using human embryos to understand the implications of the findings and the questions that remain.

HHMI investigator Sean J. Morrison, director of the University of Michigan Center for Stem Cell Biology, testifies to state and national officials about stem cell research, writes op-eds, and frequently talks with reporters.

Douglas A. Melton, a co-founder of the Harvard Stem Cell Institute, has discussed stem cell policy with President Bush. The HHMI investigator doesn't particularly enjoy policy work, but thinks it is important.

The iPS findings added to the ongoing debates. In his State of the Union Address on January 28, 2008, President Bush noted, “In November, we witnessed a landmark achievement when scientists discovered a way to reprogram adult skin cells to act like embryonic stem cells. This breakthrough has the potential to move us beyond the divisive debates of the past by extending the frontiers of medicine without the destruction of human life.” He urged Congress to pass a ban on cloning, which would preclude the development of stem cell lines created by somatic cell nuclear transfer, the technique Daley used in his mouse work and continues to explore with human cells.

This ban is a long-standing goal of groups opposed to human embryonic stem cell research. They praised the iPS work and used it as a reason to call (again) for a ban on therapeutic cloning.

“These are the same political lobbyists that have been looking for reasons to end this research all along,” says Morrison, who studies the mechanisms involved in adult stem cell renewal and aging. “The positions they've taken in the past were not credible, and the position they're taking on iPS cells is not credible.” He points to earlier claims by several groups that 65 diseases had been treated with adult stem cells. That claim, “has been roundly dismissed.”

“We haven't had a logical debate,” adds Melton, who argues that if stem cell research were truly unethical, “you would never say it's okay as long as you don't use federal funds.”

Both Melton and Morrison are hopeful that scientists may eventually be able to focus only on iPS cells, but they argue that it's too early to close the door on embryonic stem cell research. “Certainly from a patient perspective that would be wrongheaded,” says Melton, whose position is echoed throughout the field.

This caution is based on history. In the early 1990s, researchers thought they were closing in on treatments for genetic diseases when they figured out how to insert working copies of genes directly into patients' cells. “We could get genes to express in bone marrow,” says Daley, but those genes were inserted into cells by using viral vectors much like those involved in creating iPS cells. Because that treatment led to an unanticipated side effect—leukemia—iPS cells are not considered safe for human transplants.

“Some people believe that these are just technical obstacles we will overcome,” says Morrison. “Others believe that the Food and Drug Administration will never approve these lines, even if we improve the technology and eliminate the viruses.” He pauses before making a broader point. “It's worthwhile to bear in mind,” he says, “that we would not have iPS cells except for the ability to study embryonic stem cells. The same people who are now crowing that we don't need embryonic stem cell research tend to forget that we would never have gotten to this point without it.”

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