Science: a major breakthrough! To reveal the mechanism of brain edema after stroke

January 31, 2020 / BIOON / -- brain edema (cerebellar edema) is a swelling in the brain, which is a serious and potentially fatal complication of stroke In a new study of mice, researchers from medical center of University of Rochester and University of Copenhagen in Denmark found for the first time that the glymphatic system, which is usually related to waste removal, was abnormal during a stroke, resulting in cerebrospinal fluid flooding the brain, causing brain edema and brain cell drowning Relevant research results were published online in the journal Science on January 30, 2020, and the title of the paper is "cererospinal fluid influx drives acute ischemic tissue swelling" The picture is from cc0 public domain Dr Maiken Nedergaard, co-author of the paper and co director of the center for translational neurology at the University of Rochester Medical Center, said: "these findings suggest that the lymphoid system of the brain plays a key role in the acute tissue swelling of the brain after a stroke Understanding this dynamic change driven by electrical activity storms in the brain points the way to developing potential therapeutic strategies that may improve stroke outcomes " The lymphoid system of the brain was first discovered by Nedergaard laboratory in 2012 It is attached to the cerebral blood circulation system and consists of multi-layer tubes, which contain internal blood vessels wrapped by "tubes" that transport cerebrospinal fluid This system pumps cerebrospinal fluid through brain tissue during sleep, washing away toxic proteins and other waste Although brain edema is a well-known consequence of stroke, treatment options are limited, and the severity of brain edema depends on the extent and location of stroke Since the brain is confined to the skull, it has little room for expansion If the swelling is severe, it can push into important structures, such as the brain stem that regulates the cardiovascular and respiratory systems, leading to death In extreme cases, often when it is necessary, surgeons remove a part of the skull to relieve stress in the brain Before the new study, it was thought that the source of brain edema was fluid in the blood The most common form of stroke is ischemic stroke, which occurs when blood vessels in the brain are blocked When nutrients and oxygen are deprived, brain cells are usually damaged and depolarized within minutes of a stroke When these cells release energy and discharge, they trigger adjacent cells, which produces domino effect As a result, the electric wave spreads outward from the stroke site, namely spreading depolarization When this happens, neurons release a lot of potassium ions and neurotransmitters into the brain This leads to the failure and contraction of smooth muscle cells located in the vascular wall, thus cutting off blood flow in a process called spreading ischemia Cerebrospinal fluid then flows into the resulting vacuum, submerging brain tissue and causing brain edema These fragile brain cells are basically submerged in the cerebrospinal fluid, and the brain begins to swell These depolarized waves can persist in the brain for days or even weeks after a stroke, exacerbating the damage Humberto Mestre, PhD student at Nedergaard laboratory, co-author of the paper, said, "when you force each cell that is essentially a battery to release electric charge, it represents the most destructive brain function you can achieve - you can basically discharge the entire brain surface in one breath The double attack of diffusion depolarization and local ischemia causes vasospasm, which leads to completely abnormal contraction, thus creating conditions for CSF to flow into the brain rapidly " The study linked brain regions in mice prone to this post stroke lymphoid system dysfunction to brain edema found in people with ischemic stroke Charting the way for new stroke therapies the results of these studies show that potential new treatment strategies used in combination with existing therapies aim to restore blood flow to the brain quickly after a stroke The study may also have an impact on brain swelling observed in other diseases such as subarachnoid hemorrhage and traumatic brain injury Blocking specific receptors on nerve cells may inhibit or slow down the diffusion depolarization cycle In addition, aquaporin-4, a water channel protein on the surface of astrocytes, regulates the flow of CSF When the researchers conducted stroke experiments in genetically engineered mice lacking aquaporin-4, the flow of cerebrospinal fluid into the brain slowed significantly Aquaporin-4 inhibitors are currently being developed to potentially treat cardiac arrest and other diseases, and may eventually become a candidate drug for stroke "We hope that this new finding will lead to new interventions to reduce the severity of ischemic events and other brain damage that soldiers may suffer," said Dr Matthew Munson, program manager, U.S Army Research Office, who was not involved in the new study (Bio Valley Com) reference: 1 Humberto Mestre et al Cererospinal fluid influxes drives acute ischemical tissue swing Science, 2020, DOI: 10.1126/science.aax7171 2 Brain drops in its own fluid after a stroke https://medicaexpress.com/news/2020-01-brain-fluid.html