Did you know you have little tunnels in Brain our set? That’s exactly what a team of medical researchers confirmed in mice and humans in 2018. These are microscopic channels that connect bone marrow to the meninges.
Research shows that they create a direct connection for immune cells to run from the marrow into the brain in the event of brain damage.
Previously, scientists thought that immune cells normally migrated through the bloodstream from other parts of the body in response to brain inflammation following a stroke, injury or brain disorder.
This discovery shows that these cells seem to have known a shortcut long ago.
The tiny tunnels were discovered as a team of researchers set out to investigate whether immune cells would migrate to the brain after a stroke or meningitis from the skull or most of the two bones in the tube. leg (tibia).
The specific immune cells the researchers tracked are neutrophils, or “first responders” of the immune squad. When something goes wrong, this is one of the first cells the body sends to help reduce inflammation.
The team has developed a technique to tag cells with a fluorescent membrane dye, and it acts as a cell tracker. They treated these cells with a dye, then injected them into the bone marrow site in mice. Red-tagged cells were injected into the skull and blue-tagged cells were injected into the tibia.
Once the cells had stabilized, the researchers began to induce acute inflammatory states, including stroke and chemically induced meningitis.
The team found that the skull contributes significantly more neutrophils to the brain in cases of stroke and meningitis than the tibia. But that raises a new question, how are neutrophils distributed?
Matthias Nahrendorf of Harvard Medical School and Massachusetts General Hospital in Boston says: “We started examining the skull very carefully, looking at it from all angles, trying to figure out how the neutrophils reached the brain. Unexpectedly, we discovered small channels that directly connect the medulla to the outer membrane of the brain.”
Using a microscope in a solution-filled chamber to maintain the integrity of the isolated tissue during examination, the team imaged the inner surface of a rat’s skull. There, they found microscopic vascular channels that directly connect the spinal cord to the dura mater, the protective membrane that covers the brain.
Normally, red blood cells flow through these channels from the inside of the skull to the bone marrow. In the case of a stroke, however, they are mobilized to transport neutrophils in the opposite direction, from the medulla to the brain.
But within the scope of the study, this happened in rats. To find out if humans function in a similar way, the researchers collected human skull fragments from the surgeries and conducted detailed imaging.
They also pay attention to the channels there. The diameter of this tunnel is five times larger than that in the rat skull, in both the inner and outer bony layers.
Since the initial findings of these tiny tunnels, the researchers have studied them more closely in mice. In 2021, they confirmed the connection they form with the bone marrow means that the blood cells that make the trip do not originate in the bloodstream but are actually produced directly from the marrow, thereby making them locality and high specificity.
It’s an amazing discovery, because inflammation plays a role in brain disorders and this helps scientists better understand how the brain works. It also helps to understand conditions like multiple sclerosis, in which the immune system attacks the brain.
The original discovery was published in the journal Nature Neuroscience.
Refer to Sciencealert
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