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Scientists have found that rodents’ eyes and brains appear to have incredibly similar drainage systems that are used for self-cleaning, and there is reason to think that this might apply to us, too.
This type of maintenance is necessary to remove cells and waste fluids, and we know that brains use a small network of pipes known as the glyphic system, similar to the lymphatic system that removes waste from the rest of the body.
New tests in mice and rats show that the structures in the back of their eyes, such as the optic nerve and retina, take up one or two pages from the playbook of the glyphatic system. In the absence of standard lymphatic vessels, they channel waste products through a network much like the one the brain uses.
“Like the brain within the cranial vault, the internal structures of the eye are contained within a confined space, requiring strict control of fluid homeostasis,” the researchers write in their article.
“Our analysis provides evidence for the existence of a highly polarized eye clearance system that could have implications for our understanding of eye health and disease.”
One of the key jobs of the brain’s waste removal system is to remove the toxic beta amyloid proteins that have been associated with the development of Alzheimer’s disease.
To see exactly how the eye removes similar debris, the researchers injected fluorescently labeled beta amyloid proteins into the eyes of laboratory mice. Subsequent monitoring showed the displacement of these proteins through specialized channels in the optic nerve, which is responsible for transmitting visual data to the brain.
A few hours after injection, traces of the marked proteins were found much farther, carried from the eye to the lymph nodes within the animal’s neck as part of the typical process of removing garbage from the body. Again, this coincides with the way the brain connects to the rest of the body.
While the brain’s glyphathic system is activated at night, which is why sleep is so important, the ocular version of this cleansing system appears to activate when the iris moves in response to changes in light.
It’s important to note that the new research is based on mice and rats rather than humans, but these animals have eye configurations similar to ours, albeit on a more simplified level. Furthermore, the discovery of the glyphatic system in the human brain was also inspired by experiments on rats, increasing the chances that, once again, this is not just a rodent thing.
In addition to highlighting some interesting similarities between the way the eyes and the brain handle waste, these findings could also help us understand more about eye diseases like glaucoma.
The researchers suggest that damage to the eye’s waste disposal system could be one of the causes behind the disease, where excess fluid is allowed to accumulate. A closer look at this newly discovered network should be able to tell us for sure, and perhaps also hint at more effective treatments.
“This represents only the starting point for future research on the impact of the ocular glyphatic system on the pathogenesis of various eye diseases,” said physician Peter Wostyn of the Psychiatrisch Centrum Sint-Amandus in Belgium, who was not involved in the study. Abby Olena in The scientist.
The research has been published in Medicine Translational Medicine.
