NEW YORK - Alzheimer’s disease seems to spread like an infection from brain cell to brain cell, two new studies find. But instead of viruses or bacteria, what is being spread is a distorted protein known as tau.
The finding answers a longstanding question and has immediate implications for developing treatments, researchers said. And, they said, they suspect that other degenerative brain diseases, like Parkinson’s, may spread in the brain in a similar way.
Researchers have long known that dying, tau-filled cells first emerge in an area of the brain where memories are made and stored. The disease then slowly moves outward to larger areas that involve remembering and reasoning.
But for more than a quarter century they have been unable to decide between two explanations. The spread may mean that the disease is transmitted from neuron to neuron, perhaps along the paths nerve cells use to communicate with one another. Or it could simply mean that some brain areas are more resilient than others and so resist the disease longer.
The studies provide an answer. And they indicate it may be possible to bring a patient’s Alzheimer’s disease to a halt early in its course by preventing cell-to-cell transmission.
The studies, done independently by researchers at Columbia and Harvard universities, involved genetically engineered mice that could make abnormal human tau proteins, but predominantly in the entorhinal cortex, a sliver of tissue behind the ears, toward the middle of the brain, where cells first start dying in Alzheimer’s disease.