An innovative way of imaging the human brain could help to reduce the risk of developing Alzheimer's disease.
Researchers at the University of Southern California in the US used high-resolution imaging of the human brain to show for the first time that the brain’s protective blood barrier becomes leaky with age.
This process begins in the hippocampus, a critical learning and memory centre that is damaged by Alzheimer's.
The study suggests brain scans could be used to detect changes in blood vessels in the hippocampus before they cause irreversible damage.
In the study, which is published in the journal Neuron, contrast-enhanced brain images from 64 human subjects of various ages were examined by the research team, who found early vascular leakage tends to occur in the hippocampus - which normally has the strongest barrier.
When controlling for age, the blood-brain barrier also showed more damage in the hippocampal area among people with dementia than those without the condition.
The scientists also examined brain scans of young people with multiple sclerosis without cognitive impairment and found no difference in barrier integrity in the hippocampus between those of the same age with and without the disease.
Analysis of the subjects' cerebrospinal fluid (CSF) revealed 30 per cent more albumin (a blood protein) was present in those who showed signs of mild dementia compared with age-matched controls, providing more evidence of a leaky blood-brain barrier.
A 115 per cent increase of a protein related to pericyte injury was also observed in the CSF of individuals with dementia. Pericytes are cells that surround blood vessels and help maintain the blood brain barrier; they have been linked to dementia and aging by previous research.
Dr Berislav Zlokovic, the study's principal investigator, said: "To prevent dementias including Alzheimer’s, we may need to come up with ways to reseal the blood-brain barrier and prevent the brain from being flooded with toxic chemicals in the blood.
"Pericytes are the gatekeepers of the blood-brain barrier and may be an important target for prevention of dementia."
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