Research Finds Stem Cells Aid in Spinal Cord Repair

Scientists in California have shown that it is possible to used human neural stem cells to repair spinal cord injury in mice. Debate has surrounded whether stem cells actually helped in spinal cord repair. The new research shows that when the cells were removed, the repairs disappeared.

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And I'm Michele Norris.

There's promising news today for the treatment of spinal cord injuries. Scientists in California have used human stem cells to successfully treat mice with paralysis caused by damage to their spinal cords. As NPR's Joe Palca reports, getting the human cells to work in mice is a critical step in preparing to test them in patients.

JOE PALCA reporting:

The experiment to test the stem cell therapy was fairly straightforward. Scientists started with a special strain of mice that would not reject human cells. Then they intentionally damaged the spinal cords of several dozen of these mice. The damage meant the rodents were no longer able to control their hind legs. Nine days later some of the mice got an injection of human stem cells into their spinal cords. Not stem cells from human embryos, but so-called neural stem cells derived from the nervous system of a human fetus. It didn't take a trained eye to see the improvement.

Ms. AILEEN ANDERSON (University of California-Irvine): It's a pretty clear difference in how well the animals that, you know, didn't have treatment and the animals that got cells are moving.

PALCA: Aileen Anderson of the University of California-Irvine led the research team. Anderson says in the last few years, several teams have reported similar success with a variety of approaches, some using cells and some using chemicals. Anderson says there's a huge debate about what's causing the improvement.

Ms. ANDERSON: Some people would argue in spinal cord injury, for example, there's a lot of damage, and what you want to do is replace cells that are lost, and that makes a lot of sense on the surface of it. But it looks like some stem cells, in particular situations, what they're really doing is providing support.

PALCA: One theory is the improvement is being caused by what scientists call trophic factor.

Ms. ANDERSON: Tropic factor is something that makes cells that are there anyway happier. They need it to survive. They need it to send out processes and grow and make new connections. It's like having food.

PALCA: The implanted cells may be releasing trophic factor, not replacing damaged cells. Another theory is the stem cells may act as a kind of recruiting post, getting healthy cells in the mice to leave their homes and help out to restore the spinal cord damage. Anderson says her team came up with a way to test which hypothesis was correct.

Ms. ANDERSON: We worked a way where we could kill, very selectively and without causing damage to any of the mouse cells, just the human cells. So we remove them from the equation and then ask what happens in terms of the recovery. And in fact, the recovery goes away.

PALCA: Anderson says that means the stem cells themselves are doing something important. She hasn't proven what, but she thinks they are replacing damaged spinal cord neurons. Anderson reports her conclusions in the current issue of The Proceedings of the National Academy of Sciences.

John McDonald has also been working on using stem cells to treat spinal cord injury. McDonald is at the Kennedy Krieger Institute in Baltimore. He says Anderson has taken an important step in showing that stem cells themselves are crucial for improvement.

Mr. JOHN McDONALD (Kennedy Krieger Institute): It still doesn't prove that those cells are responsible, but it's a step further than anyone else has gone.

PALCA: McDonald says Anderson's study is a milestone.

Mr. McDONALD: This is the first time human transplantable cells were used to repair the nervous system and restore function. We're still a long ways away from the other studies that need to be done to transplant those into humans, but these are important first steps.

PALCA: Most scientists believe it will take a combination of therapies to help spinal cord patients recover from their injuries. Stem cells could well be one of those therapies. Joe Palca, NPR News, Washington.

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