Concussions damage the brain’s lymph system, VEGF-C protein may help fix “faulty pipes”

In a superbly written article for Knowable Magazine, Helen Santoro elaborates on "Emerging research [that] suggests that even mild hits to the head may damage the tiny lymphatic vessels that clear toxic chemicals and cellular debris from the brain." The study that Santoro discusses, by Ashley C. Bolte et al. and published in Nature Communications, found that "mild forms of brain trauma cause severe deficits" in the brain's lymphatic drainage system in mice. This damage was observable within hours, lasting at least one-month post-injury. 

With clear explanations and helpful illustrations, Santoro explains the history of the recent discovery of a lymphatic system for the brain, how it works, and how even sub-concussive hits (in mice) appear to damage this system. The research may explain why repeated concussions, or multiple sub-concussive hits, may cause long-term symptoms and even make a person more prone to neurodegenerative diseases. 

The authors also explored fixing these "faulty pipes." Previous studies have shown that a protein called vascular endothelial growth factor C, or VEGF-C, "increases the diameter of lymphatics tubes," helping them drain. Bolte et al. gave older mice a concussion and then introduced VEGF-C into their brains. These mice had fewer macrophages and microglia than the control group of older mice that did not receive VEGF-C after a concussion.

Macrophages and microglia act to remove "damaged cells and molecular debris and can cause damage if left unchecked," leading the authors to suggest that VEGF-C "fixes the faulty pipes that drain all of the bad things from our brain." This theory has not yet been researched in humans.

See our 9/17/20 newsletter (in the Diagnostics sections) for more information about the original study by Bolte et al.