The brain is incredibly complex with an average collection of 100 billions neurons (nerve cells) taking in stimuli from the world and internally (sensory neurons) and determining a response or action (motor neurons). Much of the brain has been explored and labeled with new projects aiming at mapping all of the connections that occur within. A new study however has discovered a new type of cell within the brain that helps to clear out the waste that accumulates. This is waste that is due to normal metabolic activity and it is one of the activities that the brain partakes in particularly during sleep; which is one of the important aspects of sleep.
Scientists from the University of Queensland were able to make this discovery thanks to the use of zebrafish that is beneficial because of 2 reasons; many organs and even cells share similarities to our own and zebrafish can be bred transparent. This transparency allows for cells to be viewed externally of the fish (no cutting required) using advanced light microscopes. The cell has been grouped within the lymphatic system which is the connection between your tissues and blood that allows for the flow of nutrients and waste, and is an important part of your immune system (fighting disease causing organisms).
The reason why it took so long for a cell to be discovered is because no one thought to look. There was an assumption that the brain had no lymphatic system because of the blood-brain barrier. This is a barrier that separates the extracellular fluid of the nervous system (fluid outside of the cells) from the blood that circulates the body. This separation is due to cells forming tight junctions and it is semi-permeable (allows some things to pass but not others); which aids to protect the brain from pathogens. The scientists have discovered that these new cells might be independent and don’t need need lymph vessels to do their job (circulation of the lymphatic system).
The cells are a type of mural cell that aids in maintaining the function and structure of cells, particularly neural stem cells, and play a role in strokes (bleeds in the brain). These particular cells named mato cells in humans, help to clear lipids (fats) from the brain’s circulatory system (blood network) without a lymphatic network. Accumulation of these wastes would normally damage the brain without these cells clearing them out. By assessing how these cells work independently to clear out waste, new mechanisms for the treatment of stroke and types of dementia like Alzheimer’s (approximately 70% of dementia patients) could be revealed. Alzheimer’s is the build up of plaques and deposits (neurofibrillary tangles) which prevents normal brain function. Enhanced clearly of waste using reprogrammed mato cells could delay the onset or even prevent theses diseases from extensively damaging the brain, which is super exciting! This isn’t something that is going to occur anytime soon unfortunately with further research needed but it all could be a matter of time.