This suggests that birds maintain a precise program for hair cell regeneration that preserves frequency-specific nerve connections, which is an important aspect of proper functional recovery.
Genetic Reprogramming Converts Nonsensory Cells into Sensory Cells in the Mature Cochlea
We have artificially expressed three key hair cell fate promoting proteins in nonsensory cells of adult mice, and found that a significant number of these cells will convert into cells resembling hair cells. This offers a potential strategy for hair cell regeneration.
A Unique, Fast Synapse in the Inner Ear Keeps Us From Falling
The sensory organs that allow us to walk, dance, and turn our heads without dizziness or loss of balance contain specialized synapses that process signals faster than any other in the human body.
Hearing Involves Highly Distorted Processing of Sound by Sensory Hair Cells
Studying the distortions generated within the inner ear tells us how these signals may influence our perception of sound and also provides insight into the processes that are involved in basic sensory hair cell function.
Specific Group of Cochlear Cells in Mice Demonstrate Regenerative Potential
A surprising finding of this project was that a specific group of cells, called the greater epithelial ridge (GER), contained the majority of cells capable of growing into organoids. This ability can be interpreted as a form of regenerative potential because the GER cells can multiply and generate new sensory hair cells.
Hair Cell Eulogy
People don’t seem to understand the damage they’ll incur
The way that birds’ songs, music, voices, all become a blur -
When the ears are not protected from loud music, shotgun blasts;
The birdsong they heard yesterday may have been their last...
Researchers Discover Key Gene in Cells Associated With Age-Related Hearing Loss
Hearing Restoration Project consortium member Ronna Hertzano, M.D., Ph.D. (2009–10 ERG), an associate professor at the University of Maryland School of Medicine, and colleagues identified a gene, Ikzf2, that acts as a key regulator for outer hair cells whose loss is a major cause of age-related hearing loss. The Ikzf2 gene encodes helios, a transcription factor (a protein that controls the expression of other genes). The mutation of the gene in mice impairs the activity of helios in the mice, leading to an outer hair cell deficit.
As published in Nature in November 2018, the team tested whether the opposite effect could be created—if an abundance of helios could boost the population of outer hair cells. They introduced a virus engineered to overexpress helios into the inner ear hair cells of newborn mice, and found that some mature inner hair cells became more like outer hair cells by exhibiting electromotility, a property limited to outer hair cells. The finding that helios can drive inner hair cells to adopt critical outer hair cell characteristics holds promise for future treatments of age-related hearing loss. —University of Maryland
RNA Injection Restores Hearing in Guinea Pigs
The CEO of Oklahoma’s Hough Ear Institute and a 26-year U.S. Army veteran, Richard Kopke, M.D. (1996 ERG), coauthored a March 2018 paper in Molecular Therapy about the use of small interfering RNAs (siRNAs) to block the activity of the Notch signaling pathway gene Hes1. Hes1 has been shown to itself block supporting cells from converting into hair cells. The team found that a sustained release of siRNAs in mouse cochleae through nanoparticles after deafening resulted in the recovery of some hearing ability, measured using auditory brainstem responses. Compared with the control mice, the injected mice showed less overall hair cell loss and early signs of immature hair cell development, which the authors say may signal hair cell regeneration. —Y.L.