Researchers at the University of Rochester discovered the glymphatic system in rodents over a decade ago. Although previous research has revealed a lymphatic waste clearance system in the human brain, the glymphatic system was not definitively shown in humans.
The glymphatic pathway has been long believed to be involved in sleep dysfunction, traumatic brain injury, and Alzheimer’s disease, a new study has found that some of the ways the glymphatic system influences human health have potential implications for disease.
Recently, researchers from Oregon Health and Science University have proven the glymphatic system also exists in humans.
This glymphatic system depends on glial cells, which support neurons in the central nervous system (CNS). It uses a network of fluid-filled spaces along arteries and veins known as perivascular spaces.
According to previous studies in rats and mice, researchers found that there is cerebrospinal fluid (CSF) that flows from these perivascular spaces into the brain tissue to help soluble by-products from the CNS to be cleared.
The researchers have found a human glymphatic pathway by using specialized brain imaging. In the study, they recruited five patients who were about to undergo neurosurgery to remove brain tumors.
After their surgery, each patient had a specific type of MRI, known as FLAIR (fluid-attenuated inversion recovery) to trace the spread of cerebrospinal fluid into the brain using a gadolinium-based contrast agent.
These scans revealed that the fluid moved along defined pathways through the perivascular spaces, instead of diffusing uniformly through the brain tissue. Unlike standard MRI, the FLAIR MRI technique was also able to reveal the gadolinium tracer in the brain.
According to Erin Yamamoto, a resident in neurological surgery at the OSHU School of Medicine, a well-functioning glymphatic system can efficiently clear wastes, such as amyloid and tau, from brain tissue.
On the other hand, Yamamoto also said that there are still several limitations to the study as it involves patients, which is either how the MRIs were performed or the sample size was small.
However, the findings could open avenues for investigating how these pathways effectively flush the brain of metabolic waste products, which is expected to show factors involved in Alzheimer’s disease.
