New Mechanism by Which Alzheimer's Disease Spreads Through the Brain Discovered

A study published in Acta Neuropathologica found the cellular waste-disposal system can spread damaging protein aggregates between neurons in the brain in Alzheimer's disease, reports ScienceDaily . The researchers demonstrated that small membrane-covered droplets called exosomes used by cells to eliminate waste also can transport toxic aggregates of amyloid beta, and in this way spread Alzheimer's to new neurons. "The spread of the disease follows the way in which parts of the brain are anatomically connected," says Linköping University Professor Martin Hallbeck. "It seems reasonable to assume that the disease is spread through the connections in the brain, and there has long been speculation about how this spread takes place at the cellular level." Analysis of cadaveric brain tissue found more amyloid beta in exosomes from brains affected by Alzheimer's than in healthy controls. The team also purified exosomes from the brains from people with Alzheimer's disease, and probed whether they could be absorbed by cells cultured in the lab. "Interestingly, exosomes from people were absorbed by cultured neurons, and subsequently passed on to new cells," Hallbeck says. "The cells that absorbed exosomes that contained amyloid beta became diseased."