Nerve cells permit brain to regenerate itself

New findings throw light on how the brain heals itself and may change the way we think about treating chronic neuro-degenerative diseases like Parkinson's and Alzheimer's.

Discovery of the brain's capacity to regenerate is very recent. Neural stem cells were first discovered in the brain in the early 1990s, but it took scientists a further 10 years to show that they can regenerate nerve cells in the brain.
"Given that we now know regeneration can occur, we want to understand what drives it and what blocks it, particularly in diseases like Parkinson's and Alzheimer's," said Bryce Vissel, neuroscientist at the Garvan Institute of Medical Research (GIMR), Australia.

"We triggered rapid neuro-degeneration in the brains of mice, and it was immediately followed by a very rapid regenerative response. We wanted to know why this response could occur so effectively after acute neuro-degeneration," he said.
"On further investigation, we found high levels of a molecule known as Activin A whenever regeneration occurred. This was especially interesting because Activin A is released from nerve cells.

"Clearly Activin A was playing an important part in the regenerative process, so we triggered neuro-degeneration and at the same time blocked Activin A. The difference was dramatic.
"Regeneration all but ground to a halt," Vissel said, according to a GIMR release.

"After these initial experiments, we thought that nerve cells may directly drive regeneration by releasing Activin A. We came to realise, however, that the main action of Activin A was to block inflammation in the brain after neuro-degeneration or injury," said Vissel.
These findings were published online in the journal Stem Cells.