November is Alzheimer’s Awareness Month. In March, we remember those who suffer from Multiple Sclerosis. In April, we wear blue in hopes of discovering the cause – and finding a cure for – autism spectrum disorder. In light of recent research, it may be fitting to celebrate June as a month of hopeful progress for all those who suffer from these and other neurological disorders.
Researchers at the University of Virginia have published new research in the journal Nature that contradicts the virtually universally-held belief among scientists that the brain lacks a discernible connection with the lymphatic system. Antoine Louveau, a postdoctoral fellow at Jonathan Kipnis’s Center for Brain Immunology and Glia (BIG), made the startling discovery: “After noticing vessel-like patterns in the distribution of immune cells on his slides, he tested for lymphatic vessels and there they were. The impossible existed.”
Up to this point, scientists knew that the brain was subject to myriad immune responses, but “the mechanisms governing the entrance and exit of immune cells from the central nervous system remain poorly understood.” Lymphatic vessels have never been seen in any of the countless brain-imaging studies to date – not until Louveau’s innovative method, which involved placing “a mouse’s meninges (the membranes covering the brain) on a single slide so they could be examined as a whole.” So why has it taken so long for such a discovery to be made? Why haven’t other brain-imaging studies ever caught a glimpse of these vessels? Actually, they have been hiding “in plain sight, throughout decades of research, because [they are] very small and tucked behind a major blood vessel.” Louveau explains, “The unique location of these vessels may have impeded their discovery to date, thereby contributing to the long-held concept of the absence of lymphatic vasculature in the central nervous system.”
The significance of this discovery is paradigm-shifting (assuming that the results can be replicated by other researchers as well as in human – as opposed to mouse – brains). Kipnis elaborates, “It changes entirely the way we perceive the neuro-immune interaction. We always perceived it before as something esoteric that can’t be studied. But now we can ask mechanistic questions… We believe that for every neurological disease that has an immune component to it, these vessels may play a major role… Hard to imagine that these vessels would not be involved in a [neurological] disease with an immune component.”
The lymphatic system is essentially responsible for flushing our body of contaminants – “it carries lymph… a clear liquid that ferries immune cells and rids the body of toxins and waste.” These new findings have major implications for diseases such as Alzheimer’s. Kipnis explains: “In Alzheimer’s, there are accumulations of big protein chunks in the brain… We think they may be accumulating in the brain because they’re not being efficiently removed by these vessels.” Certainly, we have a very long way to go before such implications can be put to the test. But for those who suffer from neurological disorders, it’s a step in the right direction.
-By Betty Vine