Stem cell findings stir science forum

Advances: Repair of paralyzed rats' spinal cords holds promise.

October 25, 2004|By David Kohn | David Kohn,SUN STAFF

SAN DIEGO -- Scientists here said yesterday that they had used human stem cells to repair the damaged spinal cords of paralyzed rats and enable them to walk, an important advance that could result in human trials by 2006.

This was the first time stem cells have been successfully used to treat such spinal cord injuries, and some scientists saw the results as a powerful rebuttal to the Bush administration view that stem cell research is a long way from offering human medical treatments.

The research findings were announced at the annual conference of the Society for Neuroscience. Researchers here also disclosed several other new stem cell discoveries relating to a range of neurological disorders, including brain cancer and Parkinson's disease.

"This is incredibly promising. It shows how quickly the field is moving," said Evan Snyder, director of stem cell research at the Burnham Institute in San Diego. Snyder presented his own work yesterday, showing that stem cells have potential to deliver a lethal blow to a currently untreatable type of brain cancer.

In a similar vein, University of Wisconsin researcher Clive Svendsen said he had successfully used stem cells as a delivery mechanism, in this case for a powerful protective protein that significantly slowed the progression of Parkinson's disease.

But it was the spinal cord work that generated the most excitement and seemed most likely to be tried in humans first. "The degree of recovery we see in these animals is tremendous," said University of California, Irvine neuroscientist Hans Keirstead, who led the research. "This is a very big deal."

Keirstead succeeded in transforming human embryonic stem cells into a cell called an oligodendrocyte. These cells form the fatty substance myelin, which forms a sheath of insulation around nerve cells. Without this insulation, the nerve cells can't transmit messages. After injury, nerves in the spinal cord are often unable to regrow myelin. Even if the nerve cell regenerates, it is useless without myelin.

Keirstead transplanted the human oligodendrocytes into the spinal cords of injured rats. After nine weeks, the animals regained the ability to walk. "It's not perfect -- they're not playing soccer," Keirstead said of the rats. "But they're doing extremely well."

The treatment only worked when the stem cells were implanted soon after the spinal cord injury. In rats injured ten weeks prior to the treatment, the stem cells had no effect. Keirstead suspects that scarring around the nerve cells may block the new myelin from forming properly.

Some researchers were more cautious about Keirstead's results, noting that spinal cord research is littered with examples of seeming breakthroughs that ultimately proved unsuccessful. "The Keirstead study looks encouraging. But animal models don't always translate to humans," said Dennis A. Steindler, a neuroscience professor at the University of Florida.

Stems cells are specialized cells which can be transformed into a wide range of other cells. Some researchers think stem cells can eventually treat or cure a wide range of diseases, supporting or even replacing damaged tissue anywhere in the body.

But because some of the cells are taken from embryos, which must be destroyed during the process, the field has become controversial.

Some critics say that harvesting stem cells from embryos is immoral. In August, 2001, President Bush tried to address these concerns by limiting federal funding of embryonic stem cell research. Only work using stem cells collected before his order is eligible for federal funds. Researchers are not prohibited from using other embryonic stem cell "lines," as they are called, but they cannot use government money in this work.

Many stem cell researchers have decried this limitation, saying it has hampered their work. Stem cells have become a major issue in the presidential race, with Democrat John Kerry promising to lift the restrictions if he is elected. The Bush campaign has countered in part by saying that it's not clear that stem cell research can lead to useful medical treatments.

"We don't even know that stem cell research will provide cures for anything," first lady Laura Bush said in a speech in Pennsylvania this month.

Snyder sharply criticized this stance. "It's a totally misinformed, uneducated opinion," he said. "They don't know what's happening. They're not reading the literature."

Over the past few months, Snyder has been heavily involved in promoting Proposition 71, a California ballot initiative that would set aside more than $3 billion over the next ten years for stem cell science. The California plan is the largest of several being crafted by states and large private institutions to create non-federal sources of funding for the research.

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