Discovery of the Brain’s Lymphatic System
Given all the advances in brain mapping, it’s only normal for us to think that we know everything there is to know about the basic anatomy and functioning of the brain.
That’s precisely what makes this brain discovery a remarkable one. Quite the opposite of what is taught in medical schools, the brain too is surrounded by the lymphatic system. A 3D video shows scans of a 47 years old woman’s brain, where lymphatic vessels are shown in green. Like the neck, limbs, and other parts of our body, our brain also possesses a network of lymphatic vessels.
In October last year, the researchers made this discovery from the NIH’s National Institute of Neurological Disorders and Stroke (NINDS), the National Cancer Institute (NCI), and the University of Virginia, Charlottesville. The research was funded by:
- NIH’s NINDS
- National Institute of Aging (NIA)
- National Multiple Sclerosis Society
- Conrad N. Hilton Foundation
- Lymphatic Education and Research Network.
We will begin by giving you a clear idea about what a lymphatic system is? Then we shall proceed towards what caused the brain lymphatic system discovery? You must be also be wondering what kept us from these facts? And what even is discovery without some implications, right? So, we’ll be discussing some of the major suggestions made by this breakthrough of brain lymphatic system discovery and how this can benefit us.
What is the Lymphatic System?
The lymphatic system forms a part of the vascular system. It is made up of a vast network of lymph vessels. It plays a crucial in the body’s immune. They carry a clear fluid called lymph in them. Dead cells from most of the organs in our body leave through the lymphatic system.
The lymphatic system carries lymph to the 600 to 700 lymph nodes throughout our body and organs to fight infections. Thus, it functions as a highway to circulate immune cells and deliver wastes to the bloodstream.
The function of the Lymphatic System
- Removal of interstitial fluid from tissues
- Fat absorption
- Transportation of white blood cells
- Transportation of dendritic cells
Some may ask, how and what is the most effective way to cleanse my lymphatic system? We highly recommend a herbal lymphatic cleanse and perform the cleanse for 6 to 12 months continuously.
Causes of the discovery
The brain gets rid of its waste and fights infection was a mystery until October last year. The brain lymphatic system was discovered in the brain’s leathery outer coating called the “dura” of mice using a high-powered microscope.
Thus began the search for lymphatic vessels in primate brains.
To look for lymphatic vessels in the primate brain.
The researchers led by Dr. Daniel S. Reich injected the brains of 5 healthy human volunteers and three marmoset monkeys with a gadolinium-based magnetic dye called “gadobutrol” to visualize blood and lymph vessels. The molecules of gadobutrol are small enough to pass through blood vessels into lymphatic vessels but not small enough to leak through the blood-brain barrier into the rest of the brain.
They then scanned the brains using numerous MRI techniques. The standard MRI technique gave away nothing new. The technique that led to the discovery is black-blood imaging, which hides blood vessels.
They found smaller but equally brightly lit lines along the blood vessels of both humans and monkeys. These lines were the lymph vessels—these vessels measured 1 mm in diameter.
They injected the subjects with a second dye that can adhere to the blood vessels to be even sure. It was found that the second dye never leaked out of them or into the lymphatic vessels under study. Staining the vessels under investigation in postmortem brains further confirmed that the stained structures were indeed lymph vessels and not blood vessels.
The lymphatic system is common to all mammalian brains.
Why wasn’t it discovered sooner?
Lack of evidence
Some had suggested lymph vessels surrounding the brain, but without facts and data to support their views. There have been mentions of the imagination of lymphatics in the brain in prehistoric literature.
Paolo Mascagni, an anatomist, built full-body models of the lymphatic system two centuries ago. There the lymphatic system extended to the brain. However, the idea was dismissed as an error. The Lancet in 2003 published: “Mascagni was probably so impressed with the lymphatic system that he saw lymph vessels even where they did not exist – in the brain.”
Lack of proper infrastructure
Lymph vessels aren’t visible in standard microscopic images and MRI scans besides much larger blood vessels. They might have escaped detection probably because they’re inside a thick membrane of the brain, called the dura mater, which is thick leather consistency. Also, specifically for lymphatic vessels, markers were figured out only recently. And, the tough, leathery dura mater doesn’t stain easily.
The lack of other ideas with evidence to support them led the scientists to believe that the brain removed waste through the cerebral spinal fluid (CSF). The Cerebrospinal fluid is a clear fluid in which the brain and spinal cord are bathed. According to scientists, the wastes get absorbed directly into the blood through small structures called arachnoid granulations from the cerebrospinal fluid.
In 2015, independent groups in Finland and the United States of America reported that an active lymphatic system exists in the dura mater of the brain.
The old idea regarding wastes being removed by the cerebral spinal fluid changed once vessels carrying lymphatic fluid were discovered in the brains of mice using the high-powered microscope in Virginia. This led them to think: What if the findings in mice hold true for humans too?
Working of the brain’s lymphatic system
However, Reich and the group’s research did not decipher how this newly discovered system works. Costantino Iadecola of Weill Cornell Medical College, New York, said that it’s yet to be found out if the lymphatic vessels in the brain take in fluid and other solutes from the brain parenchyma as the mouse vessels do.
The Glymphatic System
It is also unclear how the brain’s lymphatic system works with the human brain’s “glymphatic” drainage system. In the glymphatic drainage system, the astrocytes make the fluid flow throughout the brain parenchyma to get rid of soluble Aß and other metabolic waste products.
The glymphatic system consists of fluids that were discovered in mice and humans. The University of Rochester described the glymphtatic system as the brain’s “waste-clearance system” in 2015. The glymphatic system helps remove waste from the brain and helps fuel it by transporting glucose, amino acids, lipids, and neurotransmitters.
Reich believes that brain parenchyma is rinsed by the glymphatic fluid, which eventually ends up in the dura’s lymphatic channels. His team’s discovery shows just how elaborate the whole system is.
Reich also explained that some waste carries fluid that leaves our skull through tiny pores, mostly atop our noses. Then it is absorbed into the lymphatic system through the nose’s mucous membrane. Then it goes down the lymph nodes of the neck.
A third pathway
The recent discovery indicates that there must be a third pathway through which by-products exit the brain. This pathway consists of the vessel in the dura mater. How the lymph fluids enter these vessels is still a mystery.
Nothing can be concluded before more research on how these systems interact with each other.
Implications of the discovery
Reich and his group hope these results provide newer and deeper insights into numerous neurological disorders. NINDS Director Dr. Walter J. Koroshetz believes that this new revelation could hugely alter how we think the brain and the immune system interact.
Treatment of brain disorders
It is believed that amyloid-beta accumulation in the brain is the main culprit behind neurodegeneration. The recent brain lymphatic system discovery could be vital for contemplating, treating, and preventing disorders of the brain that involve inflammation related to the body’s immune. Examples of such conditions include:
- Multiple-sclerosis (MS)
- Alzheimer’s disease
- Parkinson’s disease
This may perhaps even lead to the treatment of some mental health disorders.
Multiple Sclerosis and Brain’s Lymphatic Vessels
These new facts will now enable researchers to derive even more helpful information. They could compare the functioning of the brain lymphatic system in people with multiple sclerosis and that in healthy people. This can also unravel the causes of Multiple Sclerosis as imagined by Iadecola.
Aging increases the susceptibility to neurological disorders, including Alzheimer’s. Experiments have been performed to see if these newly found facts can improve brain conditions. Researchers applied a compound called Vascular Endothelial Growth Factor C (VEGF-C).
When they treated healthy aged mice with VEGF-C, it was found that the animals’ vessels grew bigger, and that meant the better passage of fluids through them. They also noted improvements in learning and memorizing capabilities. Recent researches suggest that repairing aging-related deterioration in meningeal lymphatic drainage can improve the efficiency of current treatments for Alzheimer’s.
A new approach to treating patients
Because the researchers behind this discovery have freely published and shared their new approach for visualizing the lymphatic vessels in the brain, neuroscientists from all around the world can begin exploring similar questions concerning the patients they study.
Knowledge of waste clearance from the brain
The relation between the brain and the immune system is at the core of understanding how the wastes produced by the central nervous system (CNS) that needs to be gotten rid of are washed away.
How the brain affects diseases?
This discovery should throw light on how the brain circulates white blood cells (WBCs) and how these body processes play a role in triggering diseases. Researchers previously thought that the brain had only a limited immune response. That is because white blood cells that enter the brain exposed to antigens had no pathway to leave.
However, if these cells drain out through the lymphatic channels, they could reach the lymphoid organs and thrive and again return to the brain. This will allow them to trigger a dramatic immune response. Iadecola wondered if this is the trigger behind Multiple Sclerosis, where the immune cells attack white matter.
Understanding of Aging
This may also elaborate on how the different processes in our body affect aging.
Revision of Neuro-Immuno Sciences
The discovery of the Central Nervous System Lymphatic System may require reassessing neuroimmunology’s fundamental principles and assumptions. It could help us understand the correlation between neurodegenerative diseases and the immune system.
Effect of diseases on drainage
It would also be worth finding if the neurological disorders cause any disruption in the lymphatic drainage system.
Lymphatic System Conclusion
Brain Lymphatic System Discovery has widespread implications. In an age where we have advanced mapping procedures, it was quite a pleasant surprise to have had such a breakthrough in the basic anatomy of one of the most vital organs in our body – the brain.
The Brain Lymphatic System will answer how the brain gets rid of its wastes. No Cerebral Spinal Fluid is involved in the waste clearance process of the brain. The Lymphatic System in the brain is continuous with that of the rest of the body. This recent discovery has changed the way we look at degenerative brain disorders.
It’s hoped that the most crucial result of this discovery will be new, more effective therapies for brain disorders like Multiple Sclerosis, Alzheimer’s disease, Parkinson’s disease, and age-related dementia. This discovery may even have implications as far as calling for a reassessment of the basic principles of neuroimmunology.
In this article, we have tried our best to put in place all the facts about this discovery that has been released and shared as of yet. We hope that the article has answered all the questions on your mind. Providing a fun, knowledgeable read for our readers is our foremost priority.