A new study from UC San Francisco shows how certain cells in the brain may cause aneurysms to weaken and rupture. It helps explain why some aneurysms burst while others do not and could lead to new ways of predicting and possibly preventing strokes.
Brain aneurysms are bulges in blood vessels that can go unnoticed for years. If they rupture, they can cause a severe and often deadly type of stroke. About 1 in 50 Americans has a brain aneurysm, but doctors still struggle to predict which ones are most dangerous.
The new study helps to unpack the biology behind these events by mapping the cells in artery walls and the interactions that weaken them.
"We've made major steps toward solving the mystery of how aneurysms form," said Ethan Winkler , MD, PhD, assistant professor of Neurological Surgery and senior author of the study, which appears June 10 in Nature Neuroscience . "We've identified the cast of characters involved and seen which ones are implicated at different phases of disease."
Aneurysms can be repaired with surgery and other minimally invasive procedures, but treatment decisions are largely based on the size of the aneurysm, its location, and patient-specific risk factors. Aneurysms that are less than 7 millimeters are usually monitored rather than repaired, even though this is not a very reliable way of predicting which ones will burst.
Usually three layers of cells, except ...
Analyzing more than 100,000 individual cells from human aneurysms and healthy brain arteries, the research team identified 19 distinct cell types and determined which genes were active in each. They also mapped how the cells were organized within the vessel wall.
Healthy arteries contain three layers: a thin inner lining, a thick layer of smooth muscle in the middle that allows arteries to expand and contract with each heartbeat, and an outer layer of fibroblasts to provide structure.
