Scientists Solve 250-Year-Old Puzzle on Brain Waste Clearance

The breakthrough, published this month in journal Cell, solved a puzzle that has stumped scientists since lymphatic vessels around the brain were first discovered roughly 250 years ago: how does our body clear away the waste? An international team led by Dr Koh Gou-young, a scientist at the Centre for Vascular Research within South Korea’s Institute for Basic Science, identified tiny openings in the tough membrane protecting the brain – dubbed arachnoid fenestrations – through which fluid drains into vessels around the nose and eyes before reaching lymph nodes in the neck.

The human brain constantly produces metabolic waste, which needs to be cleared away by cerebrospinal fluid: the clear, watery liquid that acts as a natural shock absorber and nutrient bath for the brain and spinal cord. When this system slows down, toxic proteins such as amyloid beta – a hallmark of Alzheimer’s disease – can build up, raising the risk of dementia and other neurodegenerative disorders.

To understand exactly how the clearance process works, Koh and his team used 3D imaging and electron microscopy to trace the fluid’s journey in mice genetically engineered so that their lymph nodes glowed. “We have finally clarified the long-standing mystery of how cerebrospinal fluid crosses the arachnoid membrane,” Koh said, referring to the delicate, weblike middle layer of tissue that acts as a protective wrapper for the brain and spinal cord.