A new study of rats following minor spinal cord injuries helps explain how physical therapy aids recovery, and recommends rehabilitation programs that specifically target impaired limbs in people who sustain brain and spinal cord injuries.
The researchers were led by Irin Maier and senior researcher Martin Schwab at the University of Zurich and the Swiss Federal Institute of Technology. They studied rats with small surgical injuries in the spinal cord that impaired the use of one forelimb; the rats were dressed in slings to restrict the use of either the injured or uninjured limb. After three weeks, researchers removed the slings and put the rats through their paces on an elevated horizontal ladder.
There was a noticeable difference between rats. Those that relied on their impaired limb - because their unimpaired limb had been restricted - demonstrated complete functional recovery. However, rats that had not worn slings and those that wore slings on their injured limb performed poorly; they had trouble grasping and negotiating the horizontal rungs of the ladder.
In all of the rats, healthy nerve fibers, or axons, grew into injured sections of the spinal cord. However, rats that depended on their injured limb displayed the most nerve growth. These nerve fibers also formed more synapses in rats relying on their injured limb, suggesting that forced use of a limb encourages healthy nerve cells to form new connections, perhaps and rewiring damaged spinal cord circuits that are vital for movement. (If any of this reminds of the regimen that the late Christopher Reeves was promoting, this research was supported by the Swiss National Science Foundation and the Christopher and Dana Reeve Foundation.)
Using gene chip technology, the researchers also discovered that the forced use of a limb acts as an on/off switch for genes involved in nerve fiber growth and spinal cord synapse formation. Finding out which genes are involved in recovery from spinal cord injuries may assist researchers in developing new drug treatments.
The findings were published in the Sept. 17 issue of The Journal of Neuroscience.