Washington

A new strategy was introduced last week into the stormy debate on whether the US government should support research on human stem cells. A move was made to draw a sharp line between research on the embryonic and adult versions of the pluripotent cells.

There is broad agreement that stem cells could provide a range of valuable replacement parts, from insulin-producing islet cells to treat juvenile diabetes, to neural cells for treating neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS), otherwise known as Lou Gehrig's disease.

But there is disagreement over the funding of stem-cell research. Some scientists and activists say that ethical quandary could be avoided by funding research using adult stem cells, but not embryonic stem cells. But others argue that limiting research to adult cells could prevent the field's therapeutic promise from being fully realized.

The ethical contention exists because deriving stem cells from embryos destroys them. The scientific conflict arises because many researchers think embryonic stem cells could be more useful than their adult counterparts. Embryonic stem cells can potentially become many more types of cells, and may be able to divide for longer than adult stem cells.

Both ethical and scientific reasons for and against federal funding for embryonic stem-cell research were aired at a Senate committee hearing last week that may have been a dress rehearsal for what Arlen Specter (Republican, Pennsylvania) promises to be “a knock-down, drag-out” fight in the Senate.

Specter and Tom Harkin (Democrat, Iowa) are backing a bill that would allow federal funding for both the derivation and use of embryonic stem cells. The bill, which Specter says will reach the Senate within the next month, represents just one battle in a war over stem-cell research. The US National Institutes of Health will soon issue revised guidelines that allow federal funding for the use, but not the derivation, of embryonic stem cells.

Meanwhile, private companies continue to conduct embryonic stem-cell research, unregulated by the government. And non-profit organizations may soon increase their role in both the funding and distribution of stem cells (see below).

At last week's hearing, individuals who could benefit directly from embryonic stem-cell research testified both for and against it. Mary Jane Owen, the executive director of the National Catholic Office for Persons with Disabilities, said she would rather not destroy an embryo to fix her damaged spinal cord. “We have alternatives,” she said.

Reeve: told the committee that stem cells from discarded embryos should be used for research. Credit: AP

But the US actor Christopher Reeve, who was paralysed in an equestrian accident, said scientists should keep all avenues open. Reeve emphasized that excess embryos have long been discarded after in vitro fertilization attempts have ended. “Why has the use of discarded embryos for research suddenly become an issue?” Reeve asked.

Lawrence Goldstein, professor of cellular and molecular medicine at the University of California, emphasized the need to study many kinds of stem cells. Embryonic stem cells cultured by James Thomson at the University of Wisconsin, Madison, differ substantially from embryonic germ cells grown by John Gearhart at Johns Hopkins University, even though Gearhart's cells are only slightly more developed than Thomson's.

Even two different embryonic stem cell lines may behave differently, Goldstein said after the hearing. He added that allowing funding for deriving the cells is important because different extraction and culturing techniques could result in similar-seeming cells acting differently. “We probably need a bunch of different cell lines derived in a bunch of different ways,” he said.

Having a wider variety of cell lines promotes better clinical science, says Jeff Rothstein, a neurology researcher at Johns Hopkins. But he adds that it will be important to fully characterize each cell line.

Rothstein is using stem cells from Gearhart, as well as neural stem cells derived from a fetus, to study cell therapy in ALS mouse models. He will soon examine adult progenitor cells in the same model. “We believe that only a comprehensive approach will be the best initial approach for a disease like ALS,” he says.