PORTLAND, OREGON — New research reveals a key insight into the development of cochlear hair cell bundles, found within the inner ear.
Hair bundles are precisely arranged cellular structures deep within the spiral cavity of the inner ear. Together, they convert vibrational energy into electrical signals in the brain that translate into the sensation of hearing. Once they’re lost – whether by loud noise, toxins, disease or aging – they do not naturally regenerate in people and other mammals.
The new research led by scientists at Oregon Health & Science University provides important clues that may help scientists develop new techniques to regenerate hair cells and reverse hearing loss.
Hair Cells: Form and Function
In the study published today in the journal Current Biology, researchers discovered the development of hair bundles occurs in a kind of feedback loop in which form follows function and function drives form.
Using mice, which closely model human hearing, the researchers found stereocilia, roughly 100 of which are assembled into a hair bundle, widened simultaneously with the onset of mechanotransduction – the action of converting mechanical signals in the form of sound into electrical signals measured within the brain. The stereocilia only elongated to their mature lengths after transduction had been established.
Form and function were found to be mutually reinforcing.
Jocelyn Krey, Ph.D.
“We’ve been looking at these as separate pathways,” said lead author Jocelyn Krey, Ph.D., staff scientist in the Oregon Hearing Research Center and the Vollum Institute at OHSU. “But in the course of this research, we observed the change in form occurs at the same time as the conversion of mechanical to electrical signals. So we’re seeing these happen together, and feeding each other in a way we hadn’t seen before.”
Peter Barr-Gillespie, Ph.D.
The researchers discovered when they examined mice lacking transduction or used a compound to block transduction, the animals did not develop the classic staircase-shaped form of mature hair bundles.
Researchers say the study suggests that new techniques to reverse hearing loss should focus on the critical importance of early development.
“In the future, with the rapid development of gene editing tools like CRISPR, we will be able to turn on genes at will. I have no doubt we will be there in 5 or 10 years.”
–Peter Barr-Gillespie, Ph.D., senior author and professor in the OHSU Research Center and senior scientist in the Vollum Institute
Lead study author, Dr. Barr-Gillespie, also serves as OHSU’s chief research officer and executive vice president.
The study was supported by confocal microscopy conducted in the OHSU Advanced Light Microscopy Core through National Institutes of Health grant P30 NS061800; electron microscopy performed at the OHSU Multiscale Microscopy Core; and NIH grants R03 DC014544; R01 DC014720; R01 DC002368 and R01 DC011034.
Source: OHSU
Finally, the cyclic (form and function) is understood after its discovery in aerodynamics way back in 1926. A.C.Kermode gave it meaning in his thesis on aerodynamics.
To explain this further, any acoustic wave form traveling through the medium of air or metal, will send shock waves forward that serves as advance warning in its forward pathway. Hence, the stereocilia ahead of the wave path will spread apart in preparation to capture the sound wave, and based upon the frequency (critical), slowly the cilia will begin its vibrations in heightened form as the distance narrows down for key analysis. Every sound recieved at the stereocilia will then merge its vibration with the cilia itself, and then, and only then, will this transduction take place as a single merged vibration where it is then possible to synapse this and generate an electric potential.
Comprehende Senor?
The distances between the cilia groups is unfortunately too excessive to allow growth of interconnective axons that could have helped create new pathways!
It is what it is!
Please have Dr. Barr-Gillespie contact me for a better understanding of the neuroanatomy of the cilia structures in the cochlea.
Thank you!