Scientists coax brain cells in mice to regenerate

Tessier-Lavigne and colleagues focused on a different problem -- the chemicals in the body that discourage repairs.

"Even if the nerve cell could regrow, the environment is hostile to regrowth," Tessier-Lavigne said.

He said when an axon in the spinal cord is severed, the cut end sprouts a growth cone.

"It almost looks like a little hand at the end of this cable-like structure," he said.

Tiny sensors on the growth cone pick up chemical signals. In nerves in the periphery of the body such as the finger, signals tell the axon to repair itself. But in the central nervous system, chemical signals repress growth.

Tessier-Lavigne's team found one of those signals -- a protein called PirB -- in the insulating myelin sheath that wraps around each neuron. When they blocked this myelin protein in cell cultures, they got nerve cells to grow.

Tessier-Lavigne said the hope is to use this information to make drugs that allow nerve cells in the brain and spine to repair themselves.

(Editing by Maggie Fox and John O'Callaghan)