A group of scientists at Harvard University have recently seen success in restoring hearing in deaf mice. The key: replacing their defective hearing genes with functional ones. This technique, called gene therapy, is an experimental process that involves inserting new genes into cells to improve their function, eliminate a harmful function or, as mentioned above, replace a nonfunctional group of genes (United States National Library of Medicine).
National surveys show that the number of Americans with hearing disabilities has been increasing greatly over the past few decades (American Speech-Language-Hearing Association). The Harvard team focused on a specific gene involved in hearing, TMC1. This gene encodes transmembrane proteins and is “required for the normal function of cochlear hair cells” (National Center for Biotechnology Information). These hair cells are the key sensory receptors that deliver signals of sound to the brain to create a sense of hearing (NCBI). TMC1 defects are common in children born with mutations that render them deaf. The Harvard study is focused on mending these genetic defects so children can hear, even after being born in silence.
Using mice with defective TMC1 genes, the Harvard scientists watched what happened when the mice underwent gene therapy to receive a new and improved TMC1 gene. Although not a perfect fix, the gene therapy did restore some of the hearing in the experimental mice. This is a promising result for the future of restoring hearing, but Jeffrey Holt, co-author of the Harvard study, says the treatment “still needs some tweaks.” Unfortunately, TMC1 is only one of many genes that cause hearing loss when defective. “Each one may need its own customized treatment,” warns Dr. Tobias Moser, an auditory neuroscience professor from the University of Gottingen in Germany who has been following the Harvard study.
Although the gene therapy technique used to restore hearing in deaf mice at Harvard is far from being ready for clinical trials, scientists at the University of Kansas Medical Center have already been working with human patients, using gene therapy to mend damaged hair cells. Funded by Novartis, the scientists at Kansas have been focusing on adults who have lost their hearing over time for various reasons, as opposed to children born with genetic defects impacting their sense of hearing.
Want to know more about gene therapy and how it works? Check out this video:
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