Summary: Researchers have discovered a previously unidentified component of brain anatomy that acts both as a protective barrier and as a platform through which immune cells monitor the brain for signs of inflammation and inflammation. infection.
Source: University of Rochester
From the complexity of neural networks to basic biological functions and structures, the human brain only reluctantly reveals its secrets. Advances in neuroimaging and molecular biology have only recently allowed scientists to study the living brain at a level of detail never before achieved, unlocking many of its mysteries.
The latest discovery, described today in the journal Scienceis a previously unknown component of brain anatomy that acts both as a protective barrier and as a platform from which immune cells monitor the brain for infection and inflammation.
The new study comes from the labs of Maiken Nedergaard, co-director of the Center for Translational Neuromedicine at the University of Rochester and the University of Copenhagen and Kjeld Møllgård, MD, professor of neuroanatomy at the University of Copenhagen. Nedergaard and his colleagues transformed our understanding of the fundamental mechanics of the human brain and made important discoveries in the field of neuroscience, including detailing the many critical functions of previously overlooked brain cells called glia and the brain’s unique process of elimination. waste, which the lab called the glymphatic system.
“The discovery of a new anatomical structure that separates and helps control the flow of cerebrospinal fluid (CSF) in and around the brain now offers us a much better appreciation of the sophisticated role the CSF plays not only in transport and removing waste from the brain, but also supporting its immune defenses,” Nedergaard said.
The study focuses on the membranes that envelop the brain, which create a barrier with the rest of the body and keep it bathed in CSF. The traditional understanding of what is collectively called the meningeal layer, a barrier made up of individual layers called the dura, arachnoid, and pia.
The new layer discovered by the research team based in the United States and Denmark further divides the space under the arachnoid layer, the subarachnoid space, into two compartments, separated by the newly described layer, which the researchers call SLYM, an abbreviation of Sbarachnoid LYmphatic type Mkiss. Although much of the research in the article describes the function of SLYM in mice, it also points to its actual presence in the adult human brain.
The SLYM is a type of membrane called the mesothelium, which is known to line other organs in the body, including the lungs and the heart. Mesothelia generally surrounds and protects organs and houses immune cells.
The idea that a similar membrane might exist in the central nervous system was a question first posed by Møllgård, the study’s first author. His research focuses on developmental neurobiology and the barrier systems that protect the brain.
The new membrane is very thin and delicate, and consists of a single or a few cells thick. However, SLYM is an impermeable barrier, and only allows very small molecules to pass; it seems to separate “clean” and “dirty” CSF.
This last observation alludes to the probable role played by SLYM in the glymphatic system, which requires a controlled flow and exchange of CSF, allowing the influx of fresh CSF while removing toxic proteins associated with Alzheimer’s disease and d other neurological diseases of the central nervous system.
This discovery will help researchers better understand the mechanics of the glymphatic system, which was the focus of a recent $13 million grant from the National Institutes of Health’s BRAIN Initiative to the University’s Center for Translational Neuromedicine. of Rochester.
SLYM also appears to be important for brain defenses. The central nervous system maintains its own native population of immune cells, and the integrity of the membrane prevents outside immune cells from entering. Additionally, the SLYM appears to harbor its own population of central nervous system immune cells that use the SLYM for surveillance on the surface of the brain, allowing them to scan cerebrospinal fluid for signs of infection.
The discovery of SLYM opens the door to further study of its role in brain disease. For example, the researchers note that larger and more diverse concentrations of immune cells congregate on the membrane during inflammation and aging. When the membrane ruptured during traumatic brain injury, the resulting disruption of CSF outflow compromised the glymphatic system and allowed non-central nervous system immune cells to enter the brain.
These and similar observations suggest that diseases as diverse as multiple sclerosis, central nervous system infections, and Alzheimer’s disease could be triggered or worsened by abnormalities in SLYM function. They also suggest that delivery of drugs and gene therapies to the brain may be affected by SLYM function, which will need to be considered as new generations of biological therapies are developed.
Additional co-authors include Felix Beinlich, Peter Kusk, Leo Miyakoshi, Christine Delle, Virginia Pla, Natalie Hauglund, Tina Esmail, Martin Rasmussen, Ryszard Gomolka, and Yuki Mori from the Center for Translational Neuromedicine at the University of Copenhagen.
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About this neuroanatomy research news
Author: Press office
Source: University of Rochester
Contact: Press Office – University of Rochester
Picture: Image is credited to University of Copenhagen
Original research: Access closed.
“A mesothelium divides the subarachnoid space into functional compartmentsby Kjeld Møllgård et al. Science
Summary
A mesothelium divides the subarachnoid space into functional compartments
The central nervous system is lined with meninges, known as the dura, arachnoid, and pia mater.
We show the existence of a fourth meningeal layer that compartmentalizes the subarachnoid space in mouse and human brain, termed subarachnoid lymphatic-like membrane (SLYM). SLYM is morpho- and immunophenotypically similar to the mesothelial membrane that lines peripheral organs and body cavities, and it envelops blood vessels and houses immune cells.
Functionally, the close apposition of SLYM with the endothelial mucosa of the meningeal venous sinus allows direct exchange of small solutes between cerebrospinal fluid and venous blood, thus representing the mouse equivalent of arachnoid granules.
Functional characterization of SLYM provides fundamental insights into brain immune barriers and fluid transport.
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