Our inner ear contains hair cells that are important for hearing and balance. Unfortunately, as in all mammals, one of their features is that the final number of hair cells is reached before we are even born. From then on, loud noise, trauma, infections and aging take their toll, until loss of hair cells impairs hearing and balance.

But a new mouse study from The Rockefeller University in New York, NY, published in the Proceedings of the National Academy of Sciences, could help researchers look at new ways to regrow hair cells and restore lost hearing and balance.

The study took place at Rockefeller, which is headed by senior author and professor A. James Hudspeth, a Howard Hughes Medical Institute investigator. The lab work was performed by first author Dr. Ksenia Gnedeva, a postdoctoral researcher.

By examining mice before and after birth, Dr. Gnedeva discovered two genes that could switch on the process of generating hair cells.

Dr. Gnedeva began by looking for changes in gene expression in an inner ear structure called the utricle – a small sac or bag-like organ that is lined with hair cells and detects motion.

She eventually spotted that two genes that are highly active before birth become silent after birth, and this dramatic reduction in activity coincides with a halt in the development of hair cells in the mice’s utricles.

On further investigation, Dr. Gnedeva found when both genes were switched off in the developing mice, the entire inner ear, not just the utricle, developed abnormally.

And when she turned the genes on in older mice with fully mature hair cells, she found it led to the regeneration of new hair cells inside fully developed utricles. Dr. Gnedeva is now exploring the molecular mechanisms that trigger the proteins and what happens afterward.

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