Researchers at Harvard University have identified what may be a network of lymphatic-like vessels inside the brain that could help remove waste fluid. The finding, made while studying Alzheimer's disease in mice, raises possibilities for understanding neurodegenerative conditions. If confirmed, it could shift how scientists view brain function and diseases like Alzheimer's.
Scientists led by Chongzhao Ran at Harvard University accidentally spotted tube-like structures in brain tissue while investigating beta-amyloid protein in mice models of Alzheimer's-like disease. Beta-amyloid aids neuron function but can form toxic clumps associated with the condition, potentially due to inadequate drainage.
Team member Shiju Gu observed the structures during imaging of brain slices. Further experiments revealed dozens of these formations across various brain areas, including the cortex for thinking and problem-solving, the hippocampus for memory formation, and the hypothalamus for regulating sleep and body temperature. The structures appear to encircle blood vessels and connect to meningeal lymphatic vessels in the brain's outer layer, hinting at a role in waste clearance through the glymphatic and lymphatic systems.
Ran described the discovery as "my most significant in 30 years" and "the dream of a scientist." The team named them nanoscale lymphatic-like vessels, or NLVs, after protein markers for lymphatic vessels stained them, albeit weakly. They also detected similar structures in human brain samples from an individual with Alzheimer's and another without the disease.
However, experts express caution. Per Kristian Eide at Oslo University, not involved in the study, called it potentially "huge" and a "paradigm shift" for neurodegenerative diseases, stroke, traumatic brain injury, and normal brain function—if verified. Yet, Eide noted the faint staining might indicate they are not true lymphatic vessels, as markers can bind to other tissues. Christopher Brown at the University of Southampton suggested the formations could be imaging artefacts, such as fractures from uneven tissue expansion, explaining why prior electron microscopy studies missed them.
The researchers plan to use electron microscopy soon and cited a separate experiment where fluorescently tagged beta-amyloid entered nearby NLVs, supporting a waste-transport function. Ran stated, "I’m 90 per cent sure they are what we think." Confirmation by other groups could advance treatments for Alzheimer's and Parkinson's by improving waste disposal, such as through vessel-dilating drugs.
