Magazine article Science News

Stem Cells Repair Rat Spinal Cord Damage

Magazine article Science News

Stem Cells Repair Rat Spinal Cord Damage

Article excerpt

Among the challenges of medicine, spinal cord injury ranks high. Nerve cells in the spine don't regenerate naturally, and attempts to revive or repair a damaged cord have met with frustration. To bypass this problem, researchers have recently tried animal experiments replacing ruined nerve cells in animals with transplants of fetal cells. This technique has shown promise, but only when experimenters perform the transplant within a few days of an injury.

Researchers at Washington University School of Medicine in St. Louis now report that they have restored leg movement in injured rats by transplanting cells into the injury site 9 days after the rats received a crushing blow to the spine. The scientists used mouse-embryo stem cells modified to ensure they would grow into basic nerve cells and associated cells.

When the spine is severely bruised, some nerve cells die off immediately. A second wave of programmed cell death called apoptosis follows. Most of this carnage occurs within 24 hours, shutting off nerve signals traveling the spine, says study coauthor John W. McDonald, a physician and neuroscientist at Washington University.

The center of the bruised spine fills with fluid, becoming a cyst. Later, scar tissue piles up, preventing recovery. Neurons at the injury site stop functioning, as do their elongated extensions, called axons. Even if a neuron remains intact, it often dies quickly if the trauma has stripped the protective sheath, a fatty protein called myelin, off its axon.

The blunt injury that the researchers used in the rat experiment "stimulates the majority of [traumas] seen in people who have spinal cord injuries," McDonald says. He and his colleagues studied 62 rats whose spines were bruised and that could not support weight on their back legs. Nine days after injury, 28 of the rats each received injections of roughly 1 million embryonic stem cells pretreated with retinoic acid to induce their growth into nervous system cells. …

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