Meningeal lymphatic vessels

[3] While it was historically believed that both the brain and meninges were devoid of lymphatic vasculature, recent studies by Antoine Louveau and Jonathan Kipnis at the University of Virginia, submitted in October 2014, and by Aleksanteri Aspelund, Salli Antila and Kari Alitalo at the University of Helsinki submitted in December 2014, identified and described the basic biology of the meningeal lymphatics using a combination of histological, live-imaging, and genetic tools.

[1][2] In general, their work is thought to extend that of the Danish neuroscientist Maiken Nedergaard in identifying the pathway connecting the glymphatic system to the meningeal compartment.

It is hypothesized that they may contribute to autoimmune and inflammatory diseases of the CNS due to their role in connecting the immune and nervous systems.

Louveau et al. noticed an unusual alignment of immune cells along the dural sinus using a meningeal whole-mount technique.

"I was lucky to have a phenomenal post-doctoral fellow in my lab, Dr. Antoine Louveau, who developed a very unique technique of mounting this entire covering as a whole-mount.

The vessels extend along the length of both the superior sagittal and transverse sinuses and directly connects to the deep cervical lymph nodes.

Meningeal lymphatic vessels absorb cerebrospinal fluid and drain into the deep cervical lymph nodes.

[15] Mechanical forces and shear stress generated by lymph flow are also required for later stages of meningeal lymphatic vessel formation and maturation.

[1] Furthermore, tracing the outflow of compounds injected into the brain parenchyma have indicated that meningeal lymphatics function downstream of the glymphatic system.

Genetically engineered mice which lack the meningeal lymphatic vessels demonstrated attenuated clearance of macromolecules from the brain.

[17] The role that the meningeal lymphatics play in diseases of the nervous system is an area of active research, particularly for neurological disorders in which immunity is a fundamental player, such as multiple sclerosis, Alzheimer's disease (AD), amyotrophic lateral sclerosis, Hennekam syndrome, and Prader-Willi syndrome.

[1][2] The discovery of meningeal lymphatic vessels has attracted attention from many sources, and was touted as a scientific breakthrough in lists such as Scientific American's "Top 10 Science Stories of 2015", Science Magazine's "Breakthrough of the Year", Huffington Post's "Eight Fascinating Things We Learned About the Mind in 2015" and the National Institutes of Health's director Francis Collins's year end review.

Meningeal lymphatic vessels run parallel to the dural venous sinuses .
Example of a meningeal whole-mount taken from an adult mouse. [ 12 ] Laying the whole-mount on a glass slide allows for histological analysis of the entire dura, including the superior sagittal and transverse sinuses.
Human meningeal lymphatic vessels using magnetic resonance imaging (MRI) with gadobutrol as constrast agent which in the dura mater leaks out of blood vessels and collects inside lymphatic vessels, that show up as bright white areas on brain scans. [ 13 ] [ 14 ]
Confocal micrograph of meningeal lymphatic vessels and trafficking immune cells. LYVE1 (green), CD3e (red), and DAPI (blue) are shown.