Researchers in the U.S. and elsewhere are finding ways to get around the ethical roadblocks to embryonic stem cell research.
And at a forum in Washington this week, experts are discussing some of the most promising strategies.
Congress -- with the backing of a majority of Americans -- passed a bill earlier this year removing the strict limits on federal funding for embryonic stem cell research. That bill would have cleared the way for government-sponsored research on the stem cells plucked from embryos left over at fertility treatments.
But President Bush blocked the measure, citing a belief -- shared by many religious conservatives -- that the government should not promote research that destroys human embryos for the sake of harvesting their stem cells.
However, such research remains a hot topic in Washington and is sure to resurface after Tuesday’s elections.
In the meantime, scientists are busy looking for ways to harvest or create stem cells without harming human embryos or asking women to donate their eggs.
“We don’t need any eggs or embryos at all,” says Shinya Yamanaka, MD, a professor at the Institute for Frontier Medical Sciences in Kyoto, Japan.
Yamanaka describes his lab’s early successes in mice creating stem cells from adult cells. His research involves isolating two dozen chemicals that give embryonic stem cells their ability to grow into nearly any tissue in the body.
That property, called “pleuripotency,” is what makes scientists think stem cells can be coaxed to form new tissues that could help cure Parkinson’s and other diseases.
The Japanese researchers found that four of the chemicals, in the right mixture, transformed connective tissue cells from adult cells into pleuripotent cells Yamanaka says are “indistinguishable” from embryonic stem cells.
Still, significant problems remain.
“I have to point out, the efficiency … is very low,” Yamanaka today told the scientific conference hosted by the Institute of Medicine. Only one in 1,000 attempts to transform adult cells into stem cells was successful.
Also, the cells formed tumors when implanted in mouse tissue -- a significant roadblock to using such cells for human treatments.
Meanwhile, researchers at a Massachusetts biotech firm called Advanced Cell Technologies (ACT) have shown they can extract stem cells from early embryos without killing them. The technique has been used for a decade to perform early genetic testing during fertility treatments.
The extraction takes place when a fertilized embryo is about two-and-a-half days old and consists of just eight cells.
“You are able to pluck out one of those cells just as you would pluck out a grape from a bunch of grapes,” Robert Lanza, ACT’s vice president of research, told the Washington forum.
Lanza’s company showed that an extracted cell can be grown into pleuripotent stem cell line, and that the remaining embryo is just as viable as a normal one -- at least in mice.
This method was promoted by conservatives in Congress who opposed a repeal of the federal limits on embryonic stem cell research.
It also provides a way around the narrow supply of fertility clinic embryos that prospective parents would clear for use in research.
The method is essentially a hedge for Lanza, who favors still-controversial cloning methods to create a supply of stem cells from early embryos.
Last year in the journal Nature, scientists at the Whitehead Institute for Biomedical Research in Cambridge, Mass., published results from an experiment in which they removed a gene in mice that allows an embryo to implant in the mother’s uterus.
Without that gene, any embryos produced through cloning (in this case, mouse cloning) could not implant and hence could not be born.
That created a buzz in religious circles but did not settle the controversy.
Some Catholic authorities, including William Levada, the Archbishop of San Francisco, endorsed the procedure by stating that embryos without the ability to implant in a womb are not “true embryos.”
But some anti-abortion groups, including the American Life League, rejected the method, saying it would “create and then kill human embryos."
The controversy around the procedure is unlikely to end any time soon, Lanza says.
By Todd Zwillich, reviewed By Louise Chang, MD
SOURCES: Shinya Yamanaka, MD, PhD, professor, Institute for Frontier Medical Sciences, Kyoto, Japan. Robert Lanza, MD, vice president, Advanced Cell Technologies.Meissner, A. Nature, Jan. 12, 2006; vol 439: pp 212-215.News release, American Life League.