Nature: Revealing microglia helps protect brain health and cognitive performance

The myelin sheath is the insulating layer
that forms around nerve cells.
Changes in the structure of the myelin sheath and damage to the myelin sheath are thought to contribute to the early stages of dementia, but until now, the mechanisms of these changes have been
poorly understood.

In a new study, researchers from the University of Edinburgh in Scotland have found that immune cells called microglia help maintain the health of the myelin sheath, which is important
for nerve cells in the brain and spinal cord to function optimally.
The discovery could be used to better understand what goes wrong with the brain in dementia and pave the way
for potential future treatments.
The results were published online on December 14, 2022 in the journal Nature under the title "Microglia regulate central nervous system myelin growth and integrity
.
"

In mice without microglia, the authors observed that the myelin sheath underwent the same myelin changes observed in aging and neurodegenerative diseases, which were associated with
cognitive decline 。 The same changes are seen in a rare genetic disorder called ALSP (adult-onset leukoencephalopathy with axonal spheroids and pigmented glia, adult-onset leukoencephalopathy with axonal globular change and pigmented glia), which is characterized by early-onset dementia
.
In ALSP, the decrease in microglia occurs specifically in areas
of the brain with high levels of myelin.

Myelin sheath injury

The authors found that a signaling molecule called TGF-β released by microglia is important
for maintaining the health of the myelin sheath.
Based on this study, they plan to understand how microglia and TGF-β are altered in neurodegenerative diseases such as multiple sclerosis and Alzheimer's disease in the presence of myelin damage and cognitive decline
.

Microglia
are not required for oligodendrocytes to mature and myelination.
Image from Nature, 2022, doi:10.
1038/s41586-022-05534-y
.

Professor Veronique Miron, corresponding author and principal investigator of the UK Dementia Institute at the University of Edinburgh, said: "Our data reveal a surprising protective role
of microglia in maintaining myelin health.
If you have fewer microglia, the myelin sheath will disintegrate and cognitive performance will be affected
.
Our study also suggests that microglia may lose this protective function with aging and dementia, potentially triggering myelin damage and decline
in cognitive function.
”

Lead author Dr Niamh McNamara, a researcher at the University of Edinburgh, said: "We lack treatments that can effectively slow or stop the progression of dementia
.
However, we do know that healthy myelin is needed for healthy cognition, and changes in myelin sheath are associated with
the early stages of cognitive impairment.
A better understanding of what keeps the myelin sheath healthy, and how it is damaged, will bring us one step
closer to developing an effective therapy to stop dementia from occurring in the early stages.
(Biovalley Bioon.
com)

Resources:

Niamh B.
McNamara et al.
 Microglia regulate central nervous system myelin growth and integrity, Nature, 2022, doi:10.
1038/s41586-022-05534-y.