Did you know you have small tunnels in your head? No one else did either until recently. A team of medical researchers confirmed in mice and humans that tiny channels that connect skull bone marrow to the lining of the brain.
They may provide a way for immune cells to get to the brain in the event of damage.
Previously, scientists thought immune cells were transported from other parts of the body to deal with brain inflammation after a stroke, injury, or brain disorder.
The discovery suggests that these cells have had a way of shortening their lives.
When a team of researchers set out to learn if immune cells came from the skull or the larger of the two bones in the shin, they discovered tiny tunnels.
The immune squad's specific immune cells were the neutrophils. These are the first cells the body sends to the site when something goes wrong.
The team was able to tag cells with fluorescent dyes that act as cell trackers. They injected the cells into the bone marrow of mice. The cells were injected into the skull and the tibia.
Herrison et al. are from Nature Neuroscience.
The researchers created several models of acute inflammation after the cells had settled in.
In the event of a stroke, the skull contributed more neutrophils to the brain than the tibia. How were the neutrophils being delivered?
We started examining the skull very carefully, looking at it from all angles, trying to figure out how neutrophils are getting to the brain.
We discovered tiny channels that connected the marrow to the brain.
Herrison et al. are from Nature Neuroscience.
The team used organ-bath microscopy, which uses a chamber full of solution to maintain the integrity of the isolated tissue while it is being examined. The skull marrow and the dura are connected by veins.
Normally, red blood cells flow from the interior of the skull to the bone marrow, but in the case of stroke, they were mobilized to transport neutrophils in the opposite direction from the marrow to the brain.
This was in mice. To find out if humans have the same skull, the researchers obtained pieces of it from surgery.
Five times larger in diameter than the channels in the mouse skulls, the channels in the inner and outer layers of bone were also noticed.
Since the original discovery of these tiny tunnels, researchers have studied them more closely in mice and have confirmed that the blood cells taking the trip aren't derived from the bloodstream but from nearby marrow.
It is an amazing discovery, because inflammation plays a role in many brain disorders, and this could help scientists understand more about the mechanisms at play. The immune system attacks the brain in multiplesclerosis.
The journal Nature Neuroscience published the original discovery.
The first version of this article was published in August.
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