Source: University of Arizona
Summary: Researchers have discovered that liquefied brain after stroke is toxic and can slowly leak into the remaining healthy portion of the brain and potentially cause harm.
Scientists have known for years that the brain liquefies after a stroke. If cut off from blood and oxygen for a long enough period, a portion of the brain will die, slowly morphing from a hard, rubbery substance into liquid goop. Normally, a scar forms around dying brain tissue after a stroke. This scar, known as a glial scar, creates a barrier around the injured area to protect the remaining brain; it’s formation is critical to the healing process. Researchers from the University of Arizona College of Medicine have discovered that the liquefied, dying brain tissue is toxic and can slowly leak into the remaining healthy portion of the brain, potentially causing harm. The new findings may open the door for developing new treatments to ward off dementia after stroke. They suspect this slow, leaking fluid may be a cause of dementia after stroke. Of the 10 million people who survive a stroke each year, about one-third will develop dementia for unclear reasons. The study findings were published in the journal Neurobiology of Disease.
To better understand this dying fluid, the research team studied mice that had experienced strokes. First, the researchers extracted fluid from the area of liquefaction and tested its toxicity by placing it in a petri dish with living neurons. After 4 hours, more than 50 % of the neurons in the dish had died, compared to neurons that were placed in a dish with regular, healthy brain fluid. Using a high-powered microscope, they imaged the barrier between the healthy and injured portions of the mouse brain. Up close, the glial scar looked like “a fence made of branches twisted tightly together”. If the brain is injured near the hippocampus, the portion of the brain responsible for memory, perhaps this slow leak of toxic fluid causes neurodegeneration, the loss of neurons in the brain, and ultimately, memory problems. The team hopes to verify its results in the future by showing that post-stroke memory problems can be curbed with a drug that makes the glial scar’s barrier more robust.
Asst. Prof. Kristian Doyle said, “Most people probably assume that the brain heals in the same way as other tissues, but it doesn’t; dead brain tissue doesn’t just heal and go away like other bodily injuries. Instead, it liquefies and remains in this liquefactive state for a long time.”
More Information: Jacob C. Zbesko, “Glial scars are permeable to the neurotoxic environment of chronic stroke infarcts”, Neurobiology of Disease (2018). DOI: 10.1016/j.nbd.2018.01.007