There are about 10 classes of cells in the nervous system that generate and control movement in humans. Corticospinal motor axons are a key part. Any therapy to repair nerve damage in spinal cord injuries would likely need to include the corticospinal motor axons, said Jacqueline Bresnahan, an adjunct professor of neurological surgery at the University of California, San Francisco.
"Some regeneration has been shown in prior studies, but not very much," said Bresnahan, who's also chairwoman of the Christopher and Dana Reeve Foundation scientific advisory council. "The importance of this study is they are getting quite a robust response from these cells."
The researchers genetically engineered the corticospinal motor axons in the brains of rats to be more sensitive to brain-derived neurotrophic factor -- natural proteins of the nervous system that stimulate growth of neurons. The cells were re-programmed to produce a receptor for the growth factor.
The genetically engineered cells were delivered to brain lesion sites in the rats. The researchers did not test the functional recovery of the rats, because the animals didn't have a spinal injury.
Still, there are major hurdles to cross before a therapy could be developed that would help people.
The re-grown axons extended into a region of the deep brain but did not extend down the spinal cord, where they would need to go to help people with a spinal cord injury, Tuszynski said.
"The genetic engineering only allowed the growth factor receptor to go part way down the axon. That's what we're working on now -- trying to get the cell to send the receptor down all the way into the spinal cord," he said.
And even if the techniques to regenerate corticospinal cells are perfected, any therapy would pro
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