Researchers at Northwestern University Feinberg School of Medicine have identified in mice a previously unknown protective mechanism by which the smallest blood vessels remove blood clots and other blockages from the brain. The findings provide insights into mechanisms that may be involved in age-related cognitive decline, Alzheimer's disease and recovery from stroke.
These findings were described in the May 27 issue of Nature by Jaime Grutzendler, M.D., and colleagues. The study was supported by the National Institute on Aging (NIA), part of the National Institutes of Health.
Uninterrupted blood flow is critical for brain function, and the brain has developed various mechanisms to maintain it. Blockages in the smallest blood vessels can be cleared by processes that disintegrate or wash them out. However, not all blockages are cleared completely. Persistent blockage can reduce or stop blood flow, limiting the supply of oxygen and nutrients to the surrounding tissue and nerve cells. This, in turn, can lead to impaired communications between nerve cells and ultimately cell death.
The researchers used a newly developed imaging technique that can view the smallest blood vessels, known as microvessels, in the brains of living mice. They found that two to seven days after a blockage in brain microvessels, the cells lining the blood vessel wall engulf the remaining portion of the blockage, encapsulate it, seal it off from the interior of the blood vessel and finally expel the blocking material outside of the vessel. As a result of this process, blood flow is restored to the affected area. (See graphic below.)
"These are intriguing findings," said NIA Director Richard J. Hodes, M.D. "They open new avenues of basic research that may increase our understanding of how microvessels are maintained in the brain and throughout the body."