Researchers in the journal Nature Medicine report that they have successfully directed stem cell-derived neurons to regenerate lost tissue in damaged corticospinal tracts of rats, resulting in functional benefit.

The researchers grafted multipotent neural progenitor cells into sites of spinal cord injury in rats. The stem cells were directed to specifically develop as a spinal cord, and they did so robustly, forming functional synapses that improved forelimb movements in the rats. The feat upends an existing belief that corticospinal neurons lacked internal mechanisms needed for regeneration.

Corticospinal regeneration requires grafts to be driven toward caudalized (spinal cord), rather than rostralized, fates. Fully mature caudalized neural grafts also support corticospinal regeneration. Moreover, corticospinal axons can emerge from neural grafts and regenerate beyond the lesion, a process that is potentially related to the attenuation of the glial scar. Rat corticospinal axons also regenerate into human donor grafts of caudal spinal cord identity. 

Previous studies have reported functional recovery in rats following various therapies for spinal cord injury, but none had involved regeneration of corticospinal axons. In humans, the corticospinal tract extends from the cerebral cortex in the upper brain down into the spinal cord.

Nonetheless, the road to testing and treatment in people remains long and uncertain.

"There is more work to do prior to moving to humans," author said. We must establish long-term safety and long-term functional benefit in animals. We must devise methods for transferring this technology to humans in larger animal models. And we must identify the best type of human neural stem cell to bring to the clinic."

http://ucsdnews.ucsd.edu/pressrelease/stem_cells_used_to_successfully_regenerate_damage_in_corticospinal_injury