Image: Stem cells
John Gibbins  /  Zuma Press file
The scientific community stands firm that embryonic stem cells so far hold out the most hope that one day they might be used to grow replacements for damaged tissue.
updated 1/8/2007 5:57:25 PM ET 2007-01-08T22:57:25

Congress opens a second showdown with President Bush over embryonic stem cells this week, with Democrats now in charge and hoping to push through an expansion of taxpayer-funded research into the controversial cells.

At stake is whether cells that scientists consider the most promising will be the ones most used in the race to develop cures for dozens of diseases.

Complicating that question: There are different types of stem cells. Fetal stem cells found floating in amniotic fluid are the latest to make headlines, a finding cited by foes of the embryonic stem cell legislation that is certain to pass the House on Thursday.

“We don’t have to split the nation on this if we’ve got an alternative,” said Rep. Phil Gingrey, R-Ga., an obstetrician who opposes embryonic stem cell research because culling the cells from 5-day-old embryos destroys them.

“What we hope is that scientists will find ways to unlock the promise of stem cells without having to force people into the choice of claiming a human life in so doing,” White House spokesman Tony Snow said Monday, making clear the president hasn’t changed his stand since vetoing an identical bill to expand embryonic stem cell research just six months ago.

So why try again, when even supporters doubt they can override another veto? Polls show a majority of Americans support embryonic stem cell research, and Democrats say the public demanded action by casting ballots for stem cell supporters in the November election.

Focusing on preliminary “alternatives” like the amniotic stem cells won’t fool that public, added Sen. Tom Harkin, D-Iowa.

“If we truly want to cure and treat diseases that afflict so many people in this country, our nation’s top scientists should be allowed to pursue stem cell research of all kinds, be it embryonic, adult or amniotic,” he said.

The scientific community stands firm that research, not ideology, must determine stem cells’ true promise — and that embryonic stem cells so far are backed by the most promising evidence that one day they might be used to grow replacements for damaged tissue. Examples include new insulin-producing cells for diabetics or new nerve connections to restore movement after spinal injury.

“Let’s let the laboratories worldwide figure out which ones are the best for the task at hand, and that’s discovering treatments and cures for people who need them,” adds bioethicist Christopher Scott, who heads the Stanford Program on Stem Cells and Society.

He is tracking how batches of embryonic stem cells created by U.S. researchers are being shipped abroad, and worries that other countries more aggressively pursuing the field may be first to turn the master cells into cures unavailable to Americans.

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“Will patients have to travel to Australia to get the therapies?” he asks.

Embryonic stem cells are able to morph into any of the more than 220 cell types that make up the human body. They typically are culled from fertility-clinic leftovers otherwise destined to be thrown away. But because the culling kills the embryos, Bush on Aug. 9, 2001, restricted government funding to research using only the embryonic stem cell lines then in existence, groups of stem cells kept alive and propagating in lab dishes.

The problem: There are only about 21 of those lines available for study, most created in ways that preclude use in humans. At least 300 more lines now are available that many scientists insist are better suited for implantation into sick people.

The new legislation wouldn’t fund the creation of stem cell lines and hence any embryo destruction, but it would allow the National Institutes of Health to fund research using those already existing newer stem cell lines.

The federal stalemate hasn’t halted the work: Scientists are using private money to research newer cell lines, and five states are pouring millions into it. Indeed, when the NIH listed eight top advancements in the field for 2006, five of the projects involved privately funded cell lines.

What about other approaches? Embryonic stem cells mature into adult stem cells that make only a certain type of tissue. Scientists one day hope to turn back the clock, turning, say, blood-producing stem cells found in bone marrow into the type that could grow a liver.

A study in Oregon is transplanting stem cells from aborted fetuses into the brains of children with a killer neurologic disease, to see if they might stop the damage.

Fetuses also shed stem cells into the amniotic fluid cushioning them, allowing scientists to cull those cells harmlessly when pregnant women undergo birth-defect tests. Those cells can turn into several tissue types, but don’t yet seem as flexible as embryonic ones.

And scientists are working on ways to cull stem cells from embryos without killing them.

All this work is years away from fruition, specialists caution — and studying one at the expense of another could mean missing breakthroughs. For example, the pancreas doesn’t seem to harbor adult stem cells, said Dr. Leonard Zon, stem cell chief at Children’s Hospital Boston.

“If you want to try to make cells that produce insulin, you have to use embryonic stem cells,” he said. “New ways of making cells that have embryonic stem cell characteristics are very important to pursue, but they shouldn’t inhibit ... the progress already moving forward.”

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