As we age, the barrier becomes more porous, allowing amyloid-beta to pass more easily to the brain.
If the study findings are true of humans, then the team hopes that they might lead to drugs that do not have to target the brain, which is hard to reach and treat. This means instead of trying to devise treatments and attempts at early detection that focus exclusively on the brain, which is notoriously hard to study, researchers can extend their search to the body's other organs.
Aβ, a protein that can form plaques and smother brain cells, is generated in both brain and peripheral tissues.
It may one day be possible to treat Alzheimer's using techniques similar to kidney dialysis, after research showing that the proteins behind the disease can move from the body to the brain.
Alzheimer's disease is the most common type of dementia, a progressive and irreversible neurological disease which affects multiple brain functions and affects an estimated 850,000 people in the UK.
Their brains were infected with toxic protein that had spread from the genetically modified mice via the animals' shared blood circulation, the scientists believe.
Besides the brain, the protein is also produced in blood platelets, blood vessels and muscles, and its precursor protein is found in several other organs.More news: Conor McGregor defends 'f-t' insult: I support gay marriage
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After remaining attached to their partners for a year, the normal mice developed Alzheimer's disease. Song says the amyloid-beta traveled from the genetically-modified mice to the brains of their normal partners, where it accumulated and began to inflict damage.
Dr. Weihong Song, a UBC psychiatry professor and a Canada Research Chair in Alzheimer's Disease, says his research team focused on the amyloid-β protein, a protein of unclear function which is normally produced everywhere in the body.
"Last year an extensive study involving 1.4 million people who were followed up for many years found no increased risk associated with receiving a transfusion from people with Alzheimer's".
Taking one normal mouse (mice can not naturally get Alzheimer's disease) and one mouse that had been modified to carry the human amyloid-beta gene, they were merged into one for a period of a year.
Other signs of Alzheimer's-like damage included the loss of brain cells, inflammation and microbleeds. According to the results, Souvenaid may help in slowing down or stopping the progression of the very initial onset of Alzheimer's and may prevent it from turning into a full-blown disease.
Electrical signals involved in learning and memory were impaired after just four months.
'The protein can get into the brain from a connected mouse and cause neurodegeneration, ' Professor Song said. This study, asserted Song, shows it can.