By 2050, one in 10 individuals are expected to live with some form of hearing loss. Of the hundreds of millions of cases of hearing loss affecting individuals worldwide, genetic hearing loss is often the most difficult to treat.
While hearing aids and cochlear implants offer limited relief, no available treatment can reverse or prevent this group of genetic conditions, prompting scientists to evaluate gene therapies for alternative solutions.
Among the various approaches being explored, adeno-associated virus (AAV) vectors have shown to be the most promising. The AAV vectors, previously, restored hearing in neonatal animals with genetic defects.
In the study, published in the journal Molecular Therapy, the vectors demonstrated their ability to restore hearing in fully mature or aged animal models. This proof-of-concept is necessary before testing the intervention in humans with genetic hearing loss.
For the study, the researchers from Massachusetts Eye and Ear hospital in the US developed a mature mouse model with a mutation equivalent to a defective TMPRSS3 human gene, which typically results in progressive hearing loss.
They observed robust hearing in the aged mice upon injecting the animals with an AAV carrying a healthy human TMPRSS3 gene.
“Our findings suggest that a virally mediated gene therapy, either by itself or in combination with a cochlear implant, could potentially treat genetic hearing loss,” said corresponding author Zheng Yi Chen, an investigator in the Eaton-Peabody Laboratories at Mass Eye and Ear.
“This was also the first study that has rescued (restored) hearing in ageing mice, which points to the feasibility of treating DFNB8 (a type of genetic hearing loss) patients with DFNB8 even at an advanced age. The study also establishes the feasibility of other gene therapies in the aged population.”