Recently, researchers from the University of Rochester and the University of Copenhagen discovered an as yet unidentified layer of tissue in the brain.
The membrane is a few cells thick and would help protect gray matter and white matter of the brain. In addition, scientists believe that it participates in the mediation of exchanges small dissolved substances. These exchanges that would occur between the compartments of the brain. This layer could take part in thewaste disposal of the brain and regulation of immune defenses in the skull.
A fourth membrane protecting the brain?
Kjeld Møllgårda molecular biologist from the University of Copenhagen, and his colleagues called this structure « SLIME ». Which means « Subarachnoid LYmphatic-like Membrane » or literally “subarachnoid lymphatic-like membrane”. With this discovery, we now have a total of four membranes covering our brain.
The team mainly carried out their research on this subject on mice. To do this, she used two-photon microscopy and dissections. However, the group also confirmed the presence of la SLIME in the brain of an adult human.
Scientists discovered SLYM between two other membranes that similarly help protect the brain. The diaphragm splits cerebrospinal fluid (LCR) in two. From what they observed, it would act as a barrier for the molecules of cerebral fluid. More precisely, no molecule larger than three kilodaltons passes through this membrane. So the filter stops all molecules larger than an extremely small protein.
A multifunctional layer of the brain
The the nervous system central has no lymphatic vessels and is considered immunoprivileged. In other words, immune responses are highly controlled. The same goes for our eyes and testicles. Therefore, the team believes that CSF partially completes this immune defense role. Moreover, the discovery of SLYM helped her to see things more clearly.
“The discovery of a new anatomical structure that separates and helps control the flow of cerebrospinal fluid in and around the brain now allows us to better understand the sophisticated role that the CSF plays not only in the transport and elimination of brain waste, but also in supporting its immune defences. »
Maiken Nedergaard, neuroscientist at the University of Rochester
The researchers then suggested that tears of the SLYM would explain symptoms caused by traumatic brain injury. For good reason, these disturbances would give the immune cells of the skull direct access to the brain. However, these cells are not adapted to brain conditions, thus explaining l’inflammation permanente.
Moreover, la SLIME shares molecular markers with the mesothelial membrane which covers the majority of our organs. The researchers therefore believe that this structure acts as a mesothelium for the brain. In addition toenvelop blood vessels and of store immune cellsthis membrane also lubricates organs so that they slide against each other.