6/20/2006
Stem Cells Repair Paralysis in Spinal Injury Rats
Stem cells placed in rat spinal cord can partially restore function provided a drug is given to overcome anti-repair factors intrinsic to the cord and nerves, report researchers led by Douglas Kerr, M.D., Ph.D., at Johns Hopkins University.
As published in the Annals of Neurology, stem cells prompted to become motor neurons could form functioning connections with target muscles. The rats had been given a viral infection that specifically killed their own motor neurons and as a result were paralyzed.
“This research is the first to show that specific electrical circuits in the nervous system can be recreated and may be the first step toward a treatment for patients with ALS,” said Kerr, though he cautions that such a therapy is “many years away.”
The strategy used a two pronged approach. One part was to encourage growth of the nerve fibers toward muscle. This was carried out by providing the helper molecule called glial cell derived neurotrophic factor (GDNF).
The other part of the strategy was to dampen the effect of processes present in the nerve sheaths that deflect growing nerve fibers. One is an enzyme called phosphodiesterase, and the investigators used an existing drug to counter it.
The stem cells were from mice, and the rats were treated with an anti-rejection drug. A few percent of the 60,000 cells injected survived in the animals, and only a small percent of these reach muscle when the dual strategy is followed.
Yet only a few hundred motor units are present in a functioning adult human muscle, and half of these must be lost to impair function. Therefore, the researchers concluded, the replacement they effected may be about half that required for some diseases including ALS.
As measured by grip strength, video analysis, and estimation of functioning connections between nerve and muscle, only the rats given phosphodiesterase inhibitors and transplanted with GDNF producing cells into the target leg nerve showed recovery of some motor function of the limb and evidence that the transplanted stem cells made functional connections to muscle.
The treatment is complex, but the result shows that a stem cell approach can hold promise for recovery from loss of motor neurons, perhaps also for that loss in ALS.
For more information about stem cell approaches to ALS, please click here.
This project was a joint funding effort by The ALS Association and the The Robert Packard Center for ALS Research at Johns Hopkins University.
Click here for the PubMed article.
