New research sheds light on how a breakdown in the brain’s vascular system predates the accumulation of toxic plaques and tangles in the brain that bring about Alzheimer’s disease.
Nearly 50 percent of all dementias, including Alzheimer’s, begins with the breakdown of the smallest blood vessels in the brain and their protective “gatekeeper cells,” according to the study, published in Nature Medicine.
That catastrophe causes a communications failure called small vessel disease. Many people with that disease also have white matter disease, the wearing away of fatty myelin that allows neurons to transfer messages within the brain network. In an animal model, researchers found that brain deterioration associated with dementia may start as early 40 in humans.
For more than 25 years, scientists have known that white matter disease impedes a person’s ability to learn or remember new things, slows thinking and causes people to fall more often due to balance issues. They identified a link between crippled small blood vessels in the brain and white matter disease but didn’t know what started that process until now.
The study explains that pericytes, gatekeeper cells that surround the brain’s smallest blood vessels, play a critical role in white matter health and disease via fibrinogen, a protein that circulates in blood. Fibrinogen develops blood clots so wounds can heal. When gatekeeper cells are compromised, an unhealthy amount of fibrinogen slinks into the brain and causes white matter and brain structures, including axons (nerve fibers) and oligodendrocytes (cells that produces myelin), to die.
In a mouse model, the researchers used an enzyme known to reduce fibrinogen in blood and the brain. White matter volume in the mice returned to 90 percent of their normal state, and white matter connections were back to 80 percent productivity, the study found.
Reprinted from materials provided by USC.