What a Bush Veto Would Mean for Stem Cells

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Feelings run so strong on this issue that opponents have built a practical case to bolster the ethical one. The promise of embryonic stem cells has been oversold, they argue, while actual progress using adult stem cells has been overlooked. Though advocates talk longingly about the 400,000 frozen embryos in fertility clinics, a Rand Corp. study in 2003 found that 86% of them have been designated by patients for their future use or someone else's--there are approximately 100 "snowflake kids," children born from adopted frozen embryos--and only 2.8% for research. Even if that number rose with the release of federal funds, the healthiest embryos are the ones that get implanted, and the act of freezing and thawing embryos may do damage as well. Rand estimated that at best perhaps 275 viable lines would become available. That's 10 times the number now being studied using federal funds, but they would not provide the quality, quantity and genetic diversity that scientists seek.

The good news for all sides is that over the course of this long argument, researchers have learned more about how stem cells work, and the science has outrun the politics. Adult cells, such as those found in bone marrow, were thought to be less valuable than embryonic cells, which are "pluripotent" master cells that can turn into anything from a brain cell to a toenail. But adult cells may be more elastic than scientists thought, and could offer shortcuts to treatment that embryonic cells can't match.

Researchers have discovered that many tissues and organs contain precursor cells that act in many ways like stem cells. The skin, intestines, liver, brain and bone marrow contain these stem cell-- mimicking cells, which could become a reservoir of replacement cells for treating diseases such as leukemias, stroke and some cancers. "Brain stem-cells can make almost all cell types in the brain, and that may be all we need if we want to treat Parkinson's disease or ALS," says Dr. Arnold Kriegstein, who directs the University of California at San Francisco's Institute for Regeneration Medicine. "Embryonic stem cells might not be necessary in those cases." When it comes to treating heart disease, "if you could find a progenitor cell in the adult heart that has the ability to replicate," says Douglas Melton, co-director of the Harvard Stem Cell Institute, "then it's likely easier to start with that cell than begin with an embryonic stem cell, which has too many options."

Cheerleaders for adult stem-cell research point to progress on everything from spinal-cord injuries to diabetes. Scientists at the University of Minnesota have used umbilical-cord-blood stem cells to improve some neurological function; in a paper published last month, Dr. Carlos Lima in Portugal wrote about restoring some motor function and sensation in a few paralyzed patients. At a recent conference of researchers from around the world, a team from Kyoto University in Japan reported success in taking a skin cell, exposing it to four key growth factors and turning it into an embryo-like entity that produced stem cells--all without using an egg. The Kyoto group has submitted its work for publication, after which it will be open to the scrutiny of the scientific community. If successful, it could turn stem-cell science from a tedious, finicky process into a relatively straightforward chemistry project.