(RxWiki News) It's not known what causes the death of brain cells in Alzheimer's disease, but there are plenty of theories. A new explanation suggests it may be caused by an overabundance of blood vessels.
Cell death in the walls of blood vessels and in the brain has more recently been a major focus of Alzheimer's disease research.
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Wilfred Jefferies, a professor of microbiology and immunology in the University of British Columbia's Michael Smith Laboratories, said that when the blood vessels grow, the cells of the vessel walls reproduce by dividing.
He said that in the process of splitting into two new cells, they briefly become round in shape, which undermines the integrity of the barrier between blood and the brain, possibly allowing harmful elements from outside the brain to seep in.
Researchers examined brain tissue from mouse models of Alzheimer's disease, noticing it had nearly twice the density of capillaries as compared to normal mice. They observed similar high concentrations of capillaries in human brain samples from patients who had died of the disease as compared to people who did not have the disease.
Jefferies theorizes that the large quantities of blood vessels are stimulated by amyloid beta, a protein fragment that has become a hallmark of Alzheimer’s disease. He said the blood vessel growth leads to a breakdown of the blood-brain barrier, a tight network of cells that lets oxygen-carrying blood reach brain tissue while blocking harmful substances.
Deterioration of the barrier might allow the depositing of amyloid beta, which accumulates around neurons and eventually kills them. Previous studies considered the barrier leak, but suspected it was caused by the death of blood vessels, not their growth.
Jefferies said there is a parallel with the “wet" form of age-related macular degeneration, in which blood vessels grow behind the retina and then leak blood and fluid, leading to hemorrhaging, swelling, and formation of scar tissue.
He said the next logical step in treating Alzheimer's disease is to search for treatments that target blood vessel growth.
The study was published in journal PLoS One.