Lymphatic-like Structures in a Healthy Brain
Siju Gan/Harvard University
Your brain might contain a previously unknown network of blood vessels that assist in the elimination of metabolic waste. If further research substantiates this finding, it could transform our understanding of brain function and lead to novel treatments for conditions like Alzheimer’s disease.
“If this is confirmed, it’s a game-changer,” states Per Christian Eide from the University of Oslo, who was not part of the study. “This could signify a paradigm shift in our grasp of all neurodegenerative disorders, including stroke and traumatic brain injury, as well as our normal brain functions.”
The brain has its mechanisms for self-cleaning, utilizing the glymphatic system—a network of channels surrounding the brain’s blood vessels that integrates with the lymphatic system, which serves as the body’s drainage and filtration system.
Traditional imaging techniques have primarily focused on the protective outer layer of the brain without revealing lymphatic vessels. However, new research from Harvard University may have uncovered a concealed network of blood vessel-like structures akin to lymphatic vessels that connect to the glymphatic system. “This could be the most significant discovery of my three-decade career,” shares Lunn. “It’s a scientist’s ultimate dream.”
Researchers from Siju Gu‘s team at Harvard stumbled upon these structures while investigating beta-amyloid proteins in brain sections from mice exhibiting Alzheimer’s-like symptoms. Beta-amyloid is essential for neuronal function but can aggregate into toxic clumps associated with Alzheimer’s disease, often due to inadequate waste clearance.
Repeating their experiments in both mice with Alzheimer’s-like conditions and those without revealed consistent blood vessel-like structures across every brain region analyzed—highlighting areas like the hippocampus, crucial for memory formation, and the hypothalamus, which regulates sleep and body temperature.
These structures appear to envelope the brain’s blood vessels and meningeal lymphatic vessels, indicating they may play a role in waste removal via the glymphatic and lymphatic systems, according to Lunn.
Moreover, the research team identified similar tube-like formations in post-mortem samples from individuals who succumbed to Alzheimer’s disease, suggesting these structures are also present in asymptomatic individuals, Lunn adds.
The team postulates that these formations could be either a new type of lymphatic vessel lined with beta-amyloid or a protein that evolves into solid fibers relevant to Alzheimer’s pathology. These structures have also been documented in healthy brains.
To investigate further, they utilized protein markers specific to lymphatic vessels on mouse brain slices, resulting in consistent staining of the tubular structures, although not as prominent as recognized lymphatic vessels. Consequently, they coined the term nanoscale lymphatic vessels (NLVs) for these formations and determined they are unlikely to be beta-amyloid.
However, NLV markers may also attach to non-lymphoid tissues, suggesting that the faint staining might imply these NLVs are not traditional lymphatic vessels, as noted by Eide. “This is a completely new type of structure that was previously unknown. The question remains: what exactly are these?”
One theory posits that these formations could be artifacts resulting from the imaging method employed. According to Christopher Brown from the University of Southampton, UK, uneven swelling of tissue samples may introduce cracks that mimic blood vessels.
This could potentially clarify why prior brain imaging research utilizing more dependable methods, like electron microscopy, has not previously identified NLVs, Brown suggests. The research team aims to employ these techniques in the near future; Gu supports this notion, indicating that past studies may have misidentified NLVs as axons, which are long projections from similar-looking neurons.
“We’re approximately 90% confident in our findings,” Lunn confirms, referencing other research conducted by his team demonstrating that fluorescently tagged beta-amyloid in mouse brains appears to infiltrate nearby NLVs, indicating that NLVs may aid in waste fluid transport.
If further validations by other research teams confirm these results, it could enhance comprehension of Alzheimer’s disease and other protein misfolding conditions, such as Parkinson’s disease. For instance, if dilation of blood vessels aids waste clearance, it might pave the way for developing therapeutic drugs for these neurological disorders, Brown concludes.
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Source: www.newscientist.com
