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A recent study from Columbia University Medical Center suggests that Alzheimer's disease first develops in one region of the brain and then jumps to other regions that are connected neuroanatomically, to eventually spread across the entire brain. The abnormal protein tau, a vital component of the neurofibrillary tangles in the brains of Alzheimer's patients, was found spreading from one neuron to another in the study. The findings disprove previous beliefs that Alzheimer's develops in independent regions of the brains at different times.

Karen Duff, professor of pathology at CUMC, said the study's results open up new avenues for research into methods of halting the progression of Alzheimer's disease and other neurological conditions.

“Earlier research, including functional MRI studies in humans, have also supported this pattern of spread,” said Scott Small, MD, study co-author and professor of neurology in the Sergievsky Center and in the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain at CUMC. “But these various findings do not definitively show that Alzheimer’s spreads directly from one brain region to another.”

Therefore, researchers developed a novel transgenic mouse with the abnormal human tau protein gene expressed in the entorhinal cortex of the brain. Over a 22 month period, the brains of the mice were analyzed, allowing researchers to map out the spread of the abnormal tau protein.

As the mice aged, researchers discovered the human tau protein spread along a linked anatomical pathway from the entorhinal cortex to the hippocampus to the neocortex. The pattern of the spread mirrored the earliest stages of human Alzheimer's disease as it slowly affects more regions of the brain.

In addition, researchers also found evidence of abnormal tau protein moving between neurons across synapses, the junction where the cells communicate with each other. The findings suggest one way to treat Alzheimer's disease would be to catch it early through brain scans or other techniques, similar to cancer treatment. If the disease is detected early, doctors could, theoretically, halt the progression of the disease with treatment. That stage of the process has yet to be discovered.

The researchers hypothesize treatment for Alzheimer's disease could target tau protein in its extracellular phase, while it is moving from cell to cell.

"If we can find the mechanism by which tau spreads from one cell to another, we could potentially stop it from jumping across the synapses - perhaps using some type of immunotherapy," Duff said. "This would prevent the disease from spreading to other regions of the brain, which is associated with more severe dementia."

According to the Alzhiemer's Association, the disease is the most common form of dementia and is characterized by the accumulation of amyloid-beta protein placque and fibrous tangles of abnormal tau protein in neurons. As the disease progresses, the placque build up and tangles start to spread to different regions of the brain, greatly affecting cognition.