New insights on the importance of skull channels for brain health
Channels allow 'brain water' to exit the brain and be screened by immune
cells in the skull's bone marrow.

Date:
May 2, 2022
Source:
Massachusetts General Hospital
Summary:
Researchers who previously discovered channels in the skull have
found that cerebrospinal fluid can exit the brain through these
channels to reach the skull's bone marrow, which can detect and
respond to infection or injury. Tapping into this process may help
investigators study and treat inflammation-related brain conditions.



FULL STORY ========================================================================== Investigators led by a team at Massachusetts General Hospital (MGH)
that previously discovered tiny channels in the skull have now found that cerebrospinal fluid (also known as "brain water") can exit the brain into
the skull's bone marrow through these channels. The discovery, which
is published in Nature Neuroscience, is important because immune cells
produced in the spongy tissue of the skull's bone marrow can screen the cerebrospinal fluid for signs of infection and other threats to the brain.


==========================================================================
In 2018, a group headed by Matthias Nahrendorf, MD, PhD, an investigator
in MGH's Center for Systems Biology and a professor of radiology at
Harvard Medical School, found that immune cells responding to brain
infection and injury come from bone marrow in the skull, and they pass
through hundreds of tiny, previously unknown channels connecting the
skull's bone marrow to the outer layers of membranes that cover the
brain (called meninges). Before then, it was thought that bone marrow throughout the body reacts to an injury or infection at any location,
but the discovery indicated that skull bone marrow has a special role
due to its proximity to the brain and its connection to the meninges
through channels.

In this latest work, the team -- which was headed by Nahrendorf,
Charles P.

Lin, PhD, leader of the Advanced Microscopy Group at the Center for
Systems Biology at MGH, and Michael A. Moskowitz, MD, a physician
investigator at MGH who was awarded the 2021 Lundbeck Brain Prize -- demonstrated that in addition to allowing immune cells to flow from the
skull's bone marrow to the meninges, the skull channels also allow the cerebrospinal fluid to flow in the opposite direction, out of the brain
and into the skull's bone marrow.

"Now we know that the brain can signal to this hub of immunity -- in other words, cry for help in case things go wrong, such as during infection
and inflammation. Cells in the skull's bone marrow are surveilling the cerebrospinal fluid that exits the brain through the skull channels we discovered earlier," says Nahrendorf. "This likely has huge implications
for conditions like dementia and Alzheimer's disease because these
diseases have an inflammatory component." Nahrendorf and his colleagues, including lead author and MGH research fellow Fadi E. Pulous, PhD, also
found that bacteria that cause meningitis (inflammation in the meninges)
travel through the channels and enter the skull's bone marrow. This
causes cells in the bone marrow to produce more immune cells to combat
the invasion. A better understanding of these processes may lead to new strategies to treat meningitis.

"Our work may also be helpful for studying situations when the immune
response is harmful, such as when skull bone marrow-derived immune
cells damage the brain and surrounding nerves. Understanding what fuels neuro-inflammation is the first step to successfully modulating it,"
says Nahrendorf.

This work was funded in part by US federal funds from the National
Institutes of Health.


========================================================================== Story Source: Materials provided by Massachusetts_General_Hospital. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Pulous, F.E., Cruz-Herna'ndez, J.C., Yang, C. et al. Cerebrospinal
fluid
can exit into the skull bone marrow and instruct cranial
hematopoiesis in mice with bacterial meningitis. Nat Neurosci,
2022 DOI: 10.1038/s41593- 022-01060-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/05/220502120429.htm

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