Cure for deafness moves closer to reality

Scientists have moved a step closer to developing a cure for deafness after managing to grow cells fundamental to hearing in mammals.

Sixty to ninety percent of cases of deafness and hearing loss are caused by damage to hair cells in the cochlea. These cells can be damaged by a wide variety of factors including loud noises, genetic defects, drugs, and infections. They are also lost as part of the aging process. Hair cells do not regenerate; therefore damage causes progressive and irreversible hearing loss, and sometimes  deafness.  

John Brigande and colleagues injected embryonic mice with DNA containing several copies of the Atoh1 gene, which codes for a transcription factor called atonal monologue 1 that triggers ear hair cell growth. Four days after the mice were born the researchers examined their hair cells. Results showed that mice injected with the extra copies of the Atoh1 gene had nearly twice as many hair cells as control mice. Furthermore, the engineered hair cells made the same proteins as normal hair cells and they responded normally to sound waves by turning them into electrical signals.

Together, these findings show that Atoh1 replace therapy can produce viable hair cells in mammals. The authors conclude: “We expect that our in utero gene transfer paradigm will enable the design and validation of gene therapies to ameliorate hearing loss in mouse models of human deafness.”

Gubbels SP, Woessner DW, Mitchell JC, Ricci AJ, Brigande JV. Functional auditory hair cells produced in the mammalian cochlea by in utero gene transfer. Nature. 2008 Aug 27. [Epub ahead of print]. doi:10.1038/nature07265.