New Delhi, Apr 24 (PTI) Damage to the brain’s white matter can trigger features often associated with a neurodegenerative disease, such as inflammation in the grey matter, a new study has suggested.
Researchers, led by those from the UK’s University of Cambridge, said that neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease are thought to be primarily associated with changes to the grey matter, the brain’s outermost layer.
Grey matter, containing the brain’s processing hubs, is linked by an information highway — the white matter.
However, findings published in the journal Nature suggest that treating a neurodegenerative condition should also target damage to the brain’s white matter, the researchers said.
They added that the consequences of white matter damage are not well understood even when it is seen as a defining feature of the autoimmune disease multiple sclerosis, in which the immune system destroys the nerves’ protective layer, the myelin sheath, and in neurodegeneration.
The researchers created a localised damage to myelin — the main component of white matter — in a well-defined brain circuit and followed what happened over time.
They found that small, localised myelin damage triggered a response in a connected, yet remote grey matter region. Neuronal activity fell, microglia — the brain’s immune cells — became activated, and connections between neurons were lost.
However, the changes were not permanent. Regenerating myelin was related with a recovery in neuronal activity and connections between neurons, and the inflammatory response subsided.
The findings also challenge the notion that an inflammation of the grey matter is harmful.
The team found that preventing grey matter inflammation impaired myelin regeneration — the result suggested that the transient response could be part of the repair process itself.
Further, when the team blocked myelin regeneration, the grey matter response did not resolve and instead became chronic — this suggests that a failed myelin regeneration may help drive the persistent low-grade inflammation seen in neurodegenerative disease.
“We found that a focal lesion in white matter is not just a local event. It can trigger a coordinated response in connected grey matter, and that response is not simply damage. It is part of the brain’s attempt to repair itself,” author Ragnhildur Thóra Káradóttir, from the University of Cambridge’s Stem Cell Institute, said.
The authors wrote, “Our findings reveal a form of regenerative plasticity coupling white matter integrity to grey matter function, which may underlie multiple neurodegenerative conditions, and highlight the potential of targeting myelin regeneration to prevent chronic neuroinflammation.”
