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From: NIH news releases and news items [mailto:[log in to unmask]] On
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Sent: Wednesday, May 26, 2010 1:18 PM
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Subject: IN MOUSE STUDY, RESEARCHERS DISCOVER NEW MECHANISM FOR CLEARING
BLOCKAGES FROM SMALLEST BLOOD VESSELS
U.S. Department of Health and Human Services
NATIONAL INSTITUTES OF HEALTH NIH News
National Institute on Aging (NIA) <http://www.nia.nih.gov/>
Embargoed for Release: Wednesday, May 26, 2010, 1 p.m., EDT
CONTACT: Barbara Cire, 301-496-1752, <e-mail: [log in to unmask]>
IN MOUSE STUDY, RESEARCHERS DISCOVER NEW MECHANISM FOR CLEARING BLOCKAGES
FROM SMALLEST BLOOD VESSELS
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.)
The html version of this release contains the following image at:
<http://www.nia.nih.gov/NR/rdonlyres/A065D61D-1D2E-4951-899F-6AD5D1391AFB/14
569/figure2wcredit1.JPG>
"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."
The research team demonstrated that this complex protective mechanism
involves the activity of an enzyme, matrix metalloprotease 2/9, which breaks
down large proteins and is known to play a role in blood vessel development
and in stroke.
The researchers also found that the ability to move the blockage out of the
blood vessel diminished with age. Young mice (age 4 months) were able to
clear blockages more quickly and thoroughly than older mice (age 22 months).
The incomplete removal of blockages in the brains of older mice led to a
prolonged shortage of oxygen to the surrounding nerve cells and damaged the
connections between nerve cells in the vicinity of the obstructed blood
vessels.
"The reduced efficiency of this protective mechanism in the older brain and
its effect on the function of nerve cells in the brain may significantly
contribute to age-related cognitive decline," said Suzana Petanceska, Ph.D.,
of the Neurobiology of Aging Branch in NIA's Division of Neuroscience, which
funded the research. "This may also be part of the mechanism by which
vascular risk factors such as high blood pressure and diabetes increase the
risk of Alzheimer's disease with age."
The NIA leads the federal effort supporting and conducting research on aging
and the medical, social and behavioral issues of older people. For more
information on research and aging, go to <www.nia.nih.gov>.
The National Institutes of Health (NIH) -- The Nation's Medical Research
Agency -- includes 27 Institutes and Centers and is a component of the U.S.
Department of Health and Human Services. It is the primary federal agency
for conducting and supporting basic, clinical and translational medical
research, and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and its programs,
visit <www.nih.gov>.
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<http://www.nih.gov/news/health/may2010/nia-26.htm>.
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