Researchers first gave the guinea pigs antibiotics which destroyed their inner-ear hair cells. They then apparently repaired the damage by injecting them with genetically engineered adenoviruses. … The therapy promotes the regrowth of crucial hair cells in the cochlea, the part of the inner ear which registers sound. After treatment, the researchers used sensory electrodes around the animals’ heads to show that the auditory nerves of treated – but not untreated – animals were now registering sound. … The experiment worked beyond expectation. “The recovery of hair cells brought the treated ears to between 50% and 80% of their original hearing thresholds,” says Raphael. Even more surprising, the team found that the hair cells were created from cells lining the scala media which – according to biological orthodoxy – should not be able to turn into other cells.
In the mammalian auditory system, sensory cell loss resulting from aging, ototoxic drugs, infections, overstimulation and other causes is irreversible and leads to permanent sensorineural hearing loss. To restore hearing, it is necessary to generate new functional hair cells. One potential way to regenerate hair cells is to induce a phenotypic transdifferentiation of nonsensory cells that remain in the deaf cochlea. Here we report that Atoh1, a gene also known as Math1 encoding a basic helix-loop-helix transcription factor and key regulator of hair cell development, induces regeneration of hair cells and substantially improves hearing thresholds in the mature deaf inner ear after delivery to nonsensory cells through adenovectors. This is the first demonstration of cellular and functional repair in the organ of Corti of a mature deaf mammal. The data suggest a new therapeutic approach based on expressing crucial developmental genes for cellular and functional restoration in the damaged auditory epithelium and other sensory systems.