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Researchers believe that they have found a way to restore hearing in mice models of a genetic type of deafness. The study could mean that a human treatment is on its way, but such a treatment would pose its own share of challenges.

According to the National Institute on Deafness and Other Communication Disorders, Usher syndrome affects hearing and vision. It causes deafness and degenerative blindness, with human sufferers first losing their peripheral vision and gradually becoming entirely blind by their teen years. The syndrome may also cause problems with balance.

According to AFP, the treatment targets the USH1C gene, because the condition is hereditary. The gene, which has previously been linked to the syndrome, controls the production of the harmonin protein. The protein helps build the hair cells that allow humans to hear; however, in people with Usher syndrome, the protein never completes the process.

The researchers, from Louisiana State University Health Sciences Center, the Rosalind Franklin University of Medicine and Science in Chicago and Isis Pharmaceuticals in California, devised a patch that attaches to the mutated gene. This patch allows the body to continue producing the protein, the BBC reports.

The results were encouraging. Mice who were genetically engineered to have Usher syndrome were able to hear at low frequencies, though their hearing degenerated after six months. In addition, they did not suffer from the balance problems that are characteristic of the syndrome.

When the experiment ended, researchers dissected the mice. They found that the mice's cochleas had grown some hair cells.

However, the treatment would pose problems if it was applied to humans. Chiefly, the treatment needed to be administered within 10 to 13 days of birth for it to work in the mice. The problem is that mice pregnancy is much shorter than human pregnancy, meaning that the treatment may need to be administered while the fetus is still in-utero.

Researchers also do not yet know why the treatment needs to be administered so early for it to work. They do not know whether it is traced to early development, suggesting the patch simply cannot make it to the inner ear beyond a certain time frame.

Usher syndrome also is the leading genetic cause of deafness and blindness, occurring in 1 in every 6,000 births. It is particular common among the descendants of French settlers in the Americas.

Counsel and Heal previously reported that researchers had devised a method to regenerate hair cells, which may provide a method to reverse hearing loss.

The study was published in the journal Nature Medicine.