Wed, 01 Jul 1998
By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - Israeli and Swedish scientists said Tuesday they had found a way to heal the spines of paralyzed rats, giving them some movement in their hind legs.
They said injecting activated immune system cells right into the damaged part of the rats' severed spines allowed the cut to heal naturally.
``The results of our experiments are promising. However, for the moment they have only been achieved in rats and much additional research still needs to be done before the new treatment is available to humans,'' Michal Schwartz of the Weizmann Institute in Rehovot, Israel, said in a statement.
Writing in the journal Nature Medicine, Schwartz, a neurobiologist, and a team of colleagues from elsewhere in Israel and the Karolinska Institute in Stockholm, said they were operating on the theory that the immune system is deliberately blocked from entering the spine and brain.
``Lower'' animals such as fish can re-grow damaged nerves and brain cells, but higher mammals cannot. Scientists believe this is because immune cells can damage delicate nerve cells. In longer-lived animals, with more complex brains, this could cause major problems.
Schwartz's team has been working to find out what would happen if the immune system were given a chance to go to work on a damaged spine. They chose to use macrophages, immune cells that not only gobble up intruders like bacteria but which secrete a variety of chemicals that start the healing process.
They cut the rats' spinal cords, paralyzing their back legs. They took macrophages from the same rats, exposed them to damaged nerve tissue in a test tube, then injected the macrophages into the damaged parts of the spine.
This activation process seemed to be important. The experiment did not work if the macrophages were not first ''shown'' nerve tissue.
Some of the 22 rats were also injected with a natural body chemical known as fibroblast growth factor, which has been shown to help spinal injuries recover.
The 22 rats were compared with 47 control rats, which were paralyzed in the same way but not given any treatment.
``According to our criterion, 15 of the treated rats and none of the controls showed recovery,'' they wrote in their report. Adding the growth factor did not seem to make any difference.
They defined recovery as an ability to move the back legs extensively and to put their legs down and stand on them.
To double-check their results, the researchers cut the spines of three of the rats in another place. These rats were again paralyzed.
They examined the spinal cords of some of the rats and saw evidence that nerve fibers had grown across the cuts.
They said theirs was the first treatment to use autologous cells -- cells from the injured animal itself -- as opposed to grafts from an embryo, or growth factors or antibodies from another animal.
Yeda Research & Development Co. Ltd., the technology transfer arm of the Weizmann Institute, has applied for a patent for the new technology.
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