Researchers Reveal Previously Unknown Tiny Channels Between Our Skull And Brain

[Judi Lynn]

Aliyah Kovner
27 AUG 2018 23:26

Neuroscientists have discovered that the type of white blood cell that serves as a first responder to tissue damage can travel directly from the bone marrow cavities inside our skulls to the outer layer of the membrane surrounding our brains using never before seen microscopic channels. It was previously believed that most of the immune cells tasked with brain maintenance were produced by reservoirs of spongy marrow inside our arm and leg bones, and that they could only be delivered to the meninges by circulating through the bloodstream.

"These findings suggest that immune cells may instead be taking a shortcut to rapidly arrive at areas of inflammation," said Francesca Bosetti, program director at the NIH's National Institute of Neurological Disorders and Stroke (NINDS), which provided funding for the study, in a statement. "Inflammation plays a critical role in many brain disorders and it is possible that the newly described channels may be important in a number of conditions. The discovery of these channels opens up many new avenues of research."

In their revelatory paper, published in Nature Neuroscience, Dr Nahrendorf and his colleagues from Massachusetts General Hospital and Harvard Medical School document how the pathway was first revealed through a series of experiments with fluorescently tagged neutrophils in mice. After marking neutrophils made in the mice’s tibias and skull bones, the authors inflicted brain damage by inducing a stroke or creating brain inflammation. Subsequent advanced imaging scans showed that the neutrophils arriving on the scene were more likely to have come from the skull marrow than that of the tibia, and that the neutrophil supply within the skull bone was much more depleted than that of the tibia and other white blood cell sources.

Interestingly, the team then found that heart tissue injuries from induced heart attacks resulted in similar responses from skull and tibia neutrophils. Taken together, the evidence suggested that skull bone marrow reacts differently to signals from the injured brain than it does to distress from other parts of the body. Yet at this point, they still didn’t understand how the neutrophils got to the dura matter – the outermost layer of the meninges – so quickly.

More:
https://www.iflscience.com/brain/researchers-reveal-previously-unknown-tiny-channels-between-our-skull-and-brain/all/

[Nitram]

1. Fascinating. There is so much we still don't know.

[Judi Lynn]

2. Newfound skull tunnels may speed immune cells' trek to brain injuries

These tiny shortcuts showed up in the bone of mice and humans
BY LAURA SANDERS 7:00AM, AUGUST 31, 2018

Skulls seem solid, but the thick bones are actually riddled with tiny tunnels.

Microscopic channels cut through the skull bones of people and mice, scientists found. In mice, inflammatory immune cells use these previously hidden channels to travel from the bone marrow of the skull to the brain, the team reports August 27 in Nature Neuroscience. It’s not yet known whether immune cells travel these paths through people’s skulls. If so, these tunnels represent a newfound way for immune cells to reach — and possibly inflame — the brain.

Along with other blood cells, immune cells are made in bones including those in the arm, leg, pelvis and skull. Researchers injected tracking dyes into bone marrow in the skull and other bones of mice, marking immune cells called neutrophils that originated in each locale. After a stroke, neutrophils flocked to the brain. Instead of coming equally from all sources of bone marrow, as some scientists had thought, most of these responding cells came from skull marrow, study coauthor Matthias Nahrendorf of Massachusetts General Hospital and Harvard Medical School and colleagues found.

Curious about cells’ journeys from skull marrow to the brain, the researchers used powerful microscopes to look where skull meets brain. Tiny rivulets through the skull bone connected bone marrow inside the skull to the outer covering of the brain. In mice, neutrophils used these channels, which averaged about 22 micrometers across, as shortcuts to reach the brain.

More:
https://www.sciencenews.org/article/skull-tunnels-immune-cells-brain-injuries?tgt=nr