Plaque in the brain tissue of someone with Alzheimer's disease.
Credit: U.S. National Institute on Ageing
SYDNEY: Neurobiologists have found they can induce Alzheimer's disease in healthy mice by injecting diseased brain tissue, which means it may have an 'infectious' mechanism similar to prion diseases.
Alzheimer's disease, which is the most common form of dementia, affects more than 200,000 Australians, and is both incurable and fatal. This study may help understand some of the mechanisms involved in Alzheimer's disease, but experts stress that there is no need to worry about catching the disease.
Collections of hard, tangled proteins called plaques are found between nerve cells in nearly all Alzheimer's patients, and are likely responsible for the loss of brain and motor function seen in the disease. These plaques could be induced in healthy mice by injecting diseased brain tissue.
Similar to prions
"The induced [protein build-up] also triggered several degenerative and inflammatory changes commonly observed in the brains of patients with Alzheimer's disease," said Mathias Jucker, from the Hertie Institute of Clinical Brain Research, in Tübingen, Germany, and an author of the study published in Science.
These misfolded proteins have properties similar to prions, the researchers concluded. Prions are tiny, infectious protein particles can cause disease, such as mad cow disease which passes from infected cattle to humans through their meat.
In the study, the researchers removed brain tissue from mice with Alzheimer's-like symptoms, and injected into it into the stomach cavity of healthy mice. Four months later, the previously healthy mice showed symptoms similar to those of Alzheimer's disease and their brains had similarly disease brain tissue.
No problem with infection
The development of the disease in the healthy mice proves that there is a previously unknown mechanism by which the infectious tissue can be moved around the body and pass through the barriers around brain. It remains unclear, however, exactly how the injected material caused the disease.
Jucker said that it also shows that exposure doesn't need to be anywhere near the brain; though the disease developed more slowly when not injected into the brain.
"Juckers team has shown that the material aggregating in brains of Alzheimer's patients is infectious", said Jüergen Götz, an Alzheimer's expert at the Brain & Mind Research Institute, University of Sydney.
"[But] we are neither cannibals nor do prefer Alzheimer's brains over healthy brains as a diet I do not see a problem with infectivity."
Infection and Alzheimer's
This fits with extensive work done by Drs. Ruth Itzhaki and Matthew Wozniak in the UK showing the presence of the DNA of herpes simplex virus that causes fever blisters within the Alzheimer plaques in brains of people who died with the disease. They have also found that infecting mice causes the plaques and tangles associated with Alzheimer's to form.
Dr. Mary Newport, Spring Hill, FL USA