The Associated Press, Junho 1998
NEW YORK (AP) -- Rats with severed spinal cords regained some leg movement after they were treated with their own white blood cells, suggesting a potential new approach for human patients.
The injury paralyzed the hind legs, so that the rats initially dragged them. After treatment, many animals could make their hind legs crawl slowly on the knees, although the legs usually couldn't support the rats' weight.
The degree of recovery is about equal to what has been achieved before with other techniques, said researcher Michal Schwartz of the Weitzmann Institute of Science in Rehovot, Israel. The more interesting thing, she said, is that planting white cells in an injured spine helped it regenerate, much as the cells help heal damage elsewhere in the body.
She stressed that the technique has been tried only in rats, and the recovery is only partial. There is "a long way to go to see whether it works in humans," she said.
She and colleagues reported the findings in the July issue of the journal Nature Medicine.
The approach is promising, said Naomi Kleitman of the University of Miami School of Medicine and the Miami Project to Cure Paralysis.
Still looking for answers
The work is part of a flurry of recent research that shows some recovery with just a small amount of spinal cord regeneration, Kleitman said. Scientists now have to figure out how that happens and whether it can be improved enough to help patients get around, she said.
If so, people would probably be treated with a combination of techniques, she said. Other approaches include building anatomical bridges across injury sites, providing substances to promote regrowth and blocking substances that inhibit regeneration.
Nerve cells through most of the body regenerate if damaged. Nobody knows why spinal nerve cells normally don't. Schwartz believes they don't get enough help from immune-system cells called macrophages, which rush to sites of injury elsewhere in the body, clean up dead cells and debris, and produce substances needed for healing.
So she and colleagues took macrophages from the rats' blood and stimulated their healing behavior by exposing them to segments of rat leg nerves in the laboratory. Then the researchers severed the animals' spinal cords and planted hundreds of thousands of the stimulated macrophages at the injury site and just next to it.
Limited regrowth
The first hints of an effect showed up about two months after the injury, Schwartz said, and 15 of the 22 treated rats had partial recovery. Experiments showed that nerve fibers had grown across the injury site, although it's not known just how much regrowth occurred, she said.
Paul Reier, a professor of neuroscience and neurosurgery at the University of Florida College of Medicine in Gainesville, called the work "a significant piece of the puzzle" of how to treat spinal injury.
He noted that the animals were treated immediately after their spinal cords were cut, so it remains to be seen whether the macrophage treatment could help people who have been paralyzed for a long time.
In addition, most human spinal injuries result from crushing rather than complete severing of the spinal cord, so scientists will have to see if the macrophage treatment would help that situation too, he said.
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