An unexpected doorway into the ear opens new possibilities for hearing restorationDate: June 28, 2023
Source: University of Rochester Medical Center
Summary: Researchers have developed a new method to deliver drugs into the inner ear. The discovery was possible by harnessing the natural flow of fluids in the brain and employing a little understood backdoor into the cochlea. When combined to deliver a gene therapy that repairs inner ear hair cells, the researchers were able to restore hearing in deaf mice.
"These findings demonstrate that cerebrospinal fluid transport comprises an accessible route for gene delivery to the adult inner ear and may represent an important step towards using gene therapy to restore hearing in humans," said Maiken Nedergaard, MD, DMSc, senior author of the new study, which appears in the journal Science Translational Medicine.
Nedergaard is co-director of the Center for Translational Neuromedicine at University of Rochester and the University of Copenhagen. The study was the product of a collaboration between researchers at the two universities and a group led by Barbara Canlon, Ph.D. in the Laboratory of Experimental Audiology at the Karolinska Institute in Stockholm, Sweden.
The number of people worldwide predicted to have mild to complete hearing loss is expected to grow to around 2.5 billion by mid-century. The primarily cause is the death or loss of function of hair cells found in the cochlea -- which are responsible for relaying sounds to the brain -- due to mutations of critical genes, aging, noise exposure, and other factors.
While hair cells do not naturally regenerated in humans and other mammals, gene therapies have shown promise and in separate studies have successfully repaired the function of hair cells in neo-natal and very young mice. However, as both mice and humans age, the cochlea, already a delicate structure, becomes enclosed in temporal bone. At this point, any effort to reach the cochlea and deliver a gene therapy via surgery risks damaging this sensitive area and altering hearing.
In the new study, the researchers describe a little understood passage into the cochlea called the cochlear aqueduct. While the name conjures images of monumental stone architecture, the cochlear aqueduct is thin boney channel no larger than a single strand of hair. Suspected to play a role in balancing pressure in the ear, new study shows that that the cochlear aqueduct also acts as a conduit between the cerebrospinal fluid found in the inner ear and the rest of the brain.
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Source:
https://www.sciencedaily.com/releases/2023/06/230628201318.htm
