Researchers say in a new study published in the eLife scientific review that they found lymphatic vessels in the tough, outer coating of the brain. This finding, according to the researchers, promises a better understanding of the physiology of lymph drainage from the central nervous system and possible deflections in neurological conditions.
Lymphatic vessels are part of the body’s circulatory system. Most of the body is parallel to the blood vessels. They carry lymphs, a colorless liquid containing immune cells and waste, into the lymph nodes.
Blood vessels transfer white blood cells to an organ and the lymphatic system removes the cells and recycles them through the body. The procedure assists the immune system to detect whether an organ is attacked by bacteria or viruses or injured.
In 1816, an Italian anatomist reported that lymph vessels were found on the surface of the brain, but for two centuries, this report was forgotten. Until recently, scientists had found no evidence of a lymphatic system in the brain, leaving some to wonder about how the brain is eliminating its waste, and others to conclude that the brain is an excellent instrument.
Then, in 2015, two studies with mice found evidence of a lymphatic system in the brain of the brain.
“I was totally surprised. At the medical school, we learned that the brain does not have a lymphatic system, “says Dr. Daniel S. Reich, one of the authors of the study. “After these studies, I thought, maybe we could find it in the human brain.”
To search for the vessels, the researchers used MRI to scan the brains of five healthy volunteers injected with gadobutrol, a magnetic dye typically used to visualize diseased blood vessels of the brain, such as multiple sclerosis or the cancer .
Dye molecules are small enough to leak out of the blood vessels in the brain of the brain but are too large to pass through the blood-brain barrier and enter other parts of the brain. At first, when the researchers used the MRI to see blood vessels, the hardened moons shone brightly and could not see any sign of the lymphatic system.
But, when they coordinated the scanner in a different way, the blood vessels disappeared and the scientists saw that the hard moon also contained smaller but almost equally bright spots and lines suspected of being lymph vessels. Subsequent analysis showed that the paint leaked from the blood vessels, ran through the stiff moon and the adjacent lymph vessels.
To examine this, the investigators performed another cycle of scans on two subjects after first infusing a second dye consisting of larger molecules that leak far less than the blood vessels. Unlike the first round of scans, they saw blood vessels in the tough womb, but not lymphatic vessels, no matter how they coordinated the scanner, confirming their suspicions.
They also found evidence for blood and lymphatic vessels during autopsy of human brain tissue. In addition, brain scans and brain autopsy studies from non-human primates confirmed the results observed in humans, indicating that the lymphatic system is a common feature of mammalian brains.