An international study found that healthy mice injected with tau protein went on to develop Alzheimer's.
The findings show that tangles of tau protein have contagious properties and may be similar to prions, which are associated with infectious brain diseases such as human Creutzfeldt-Jakob disease.
What is the research?
The findings are based on studies performed in mice. Healthy mice were injected with extracts from the brains of mice that had a genetic mutation which caused them to produce tau protein.
Staining techniques were used to investigate the brain changes in the mice and to examine what was happening to the tau proteins.
The healthy mice developed a build up of tau tangles in the brain at six, 12 and 15 months after the injection.
However, there was no sign of neurodegeneration in the mice 15 months after the injection.
What do the researchers say?
Lead researcher Dr Michel Goedert, from the Medical Research Council's laboratory of molecular biology in Cambridge, said: 'This research in mice does not show that tau pathology is contagious or that it can spread easily from mouse to mouse.
'It suggests that tangles of proteins that build up in the brain to cause symptoms could have some contagious properties within brain tissue, but not between mice that have not been injected with tissue from another mouse, and certainly not between people.'
Dr Goedert added that the findings open up new avenues in dementia research which could explain how abnormal tau spreads in the brain. 'We can also investigate how diseases caused by tau aggregates and prions are similar,' he added.
What do other researchers say?
Dr Susanne Sorensen, head of research at the Alzheimer's Society, said: 'The research was carried out using two different genetic mouse lines and we will need a lot more research before we understand the implications of these observations.
'There is still so much we do not understand about the changes in tau that lead to tangle formation in humans and, eventually, widespread brain cell death.'
- Tau protein has been found to have contagious properties that allow it to spread in the brain.
- Drugs that target the spread of tau tangles could slow the progression of Alzheimer's disease.