Ultrasound has been used to stimulate "warrior" brain cells to eat plaque from Alzheimer's disease and restore memories. Researchers used scanning ultrasound in a mouse model to stimulate microglial cells in the brain, which then eroded the plaque – abnormal deposits of protein fragments called amyloid beta.
This plaque is a hallmark of Alzheimer's disease and much research into the disease is currently focused on detecting changes to amyloid in the brain as a diagnostic tool, and understanding how it builds up to find a treatment. Previous studies have shown microglial cells are able to eat amyloid beta, but this ability is either overwhelmed or impaired in Alzheimer's cases.
Scientists at the University of Queensland have now found a way to stimulate the microglial cells to eat the plaque by using scanning ultrasound. Published in the journal Science Translational Medicine, the researchers used focused ultrasound combined with injected microbubbles, which vibrate in response to the ultrasound, to temporarily open the blood-brain barrier.
Alzheimer's treatment has long been problematic because of the blood-brain barrier, which prevents most drugs circulating in the blood stream from reaching the brain. Opening it through ultrasound allowed the scientists to stimulate the cells to clear the plaque.
Findings showed this technique completely cleared the plaque in 75% of the mice without damaging the brain tissue. Mice also showed improved memory, performing better on subsequent memory tests. Analysis showed the microglia had engulfed cellular debris to ingest more amyloid beta plaque.
Study author Gerhard Leinenga told IBTimes UK: "After the treatment microglial cells in the brains of mice were much more effective at eating the Alzheimer's plaques.
"We were somewhat surprised that the ultrasound treatment improved the memory of the mice modelling Alzheimer's disease. We found that levels of amyloid beta were significantly reduced after the ultrasound treatment and we believe that this resulted in the improvements to memory, such that when amyloid beta is removed from the brain that memory improves."
The research, however, is in very early stages and the authors now plan to test the ultrasound method in a sheep model of Alzheimer's disease.
"The human brain is much larger and more complex than a mouse brain, and so far we have only tested the therapy on mice," Leinenga said. "The next step would be to test in an animal with a larger brain and thicker skull and this will require the treatment to be adapted and a new device built.
"This is a potentially new avenue for removing amyloid beta from the brain and treating Alzheimer's disease. There are a number of steps required before it can be applied to humans. Potentially it could be given to human patients as a trial therapy at the end of further testing and adapting the treatment to larger brains."
As well as Alzheimer's, the authors say the approach could offer a potential strategy for treating other diseases involving the irregular build-up of protein in the brain.
"We think this is a very versatile and effective approach to getting drugs and other therapeutic agents across the blood-brain-barrier. Treatment of neurological diseases such as Alzheimer's disease is hampered by the inability of most drugs to cross the blood brain barrier and the ultrasound treatment overcomes this road block to developing therapies targeting the brain."