Have you experienced hearing loss? About 14% or 27.7 million adults between the age of 20 and 69 have hearing loss to some degree. Hearing loss is twice as common in men as women.
Many new and emerging treatments are now available to help or even restore hearing. In this article, you will learn about regenerating cochlear hair cells to treat hearing loss.
The Body’s Process for Hearing Sound
Let’s review the body’s normal process for hearing. Sound waves enter the ear through the auditory canal. The soundwave then hits the eardrum causing it to vibrate.
This vibration travel to the three bones, or ossicles, located in the middle ear. The ossicles increase the vibrations. The vibrations are then transmitted to the tiny hair-like cells in the cochlea.
Did you know that humans are born with 30,000 inner ear hair cells in each ear? When a large number of them are damaged, hearing loss results.
The cochlear cells have outer hair cells shaped like a can. The top of the “can” has the hair, or stereocilia, cells. The nucleus resides in the bottom of the “can”.
When the stereocilia bend in response to sound vibration, an electromotile response occurs. This causes the cell to change in length. Thus, with every sound wave, the cell shortens and lengthens.
These changes stimulate the tectoral membrane. The vibrations become amplified in the basilar membrane allowing you to sense sounds.
The auditory nerve fibers also lie with these membranes below the hair cells. Thus, the sound message is then sent from the cochlear hair cells to the auditory nerve.
This nerve carries the sound message to the brain where the information is processed. This allows the individual to interpret the sound.
Causes of Cochlear Hair Dysfunction
To date, experts report that once the cochlear hair cells become damaged, they can’t regenerate on their own.
During embryonic growth, a regulatory protein called, atonal homolog1, is needed for adequate hair cell development. Thus, many studies are now looking at this protein as a tool to stimulate hair cell regeneration.
The thyroid hormone is also essential to the development of the auditory system. It’s thought that the thyroid hormone is carried by the blood to the cochlea. Disruptions of the thyroid transporters can lead to progressive degeneration of cochlear hair cells.
Studies show an association of hearing loss with iodine deficiency, resistance to thyroid hormone, and congenital hypothyroidism. Cochlear hair cells also show damage from acoustic trauma, drug insults, aging, and environmental factor causing deafness.
The thyroid hormone promotes the developmental remodeling of the sensory cells before the onset of hearing. The thyroid hormone also impacts cochlear hair cell survival and function. Therefore, it maintains hearing.
Another cause of hair cell damage is a loud noise. Loud sounds cause large pressure waves in the ear.
The large pressure wave makes the stereocilia to bend too far. This can cause damage or death to the hair cell.
What is Regenerative Medicine?
Regenerative medicine uses growth factors such as cytokines, proteins, and mesenchymal stem cells. The focus is to achieve regenerative health by helping your body heal from within.
The mesenchymal stem cells counteract the swelling which promotes tissue damage. This is the key to regenerative medicine.
Emerging Treatments for Cochlear Hair Cells
Currently, many research studies are looking at treating cochlear hair cell deficits.
They have now located inner ear stem cells. This provides hope that these stem cells can rebuild hair cells and the spiral ganglion neuron. The result would be the re-establishment of hearing.
Studies have attempted to transplant stem cells into the inner ear. Animal studies have demonstrated promising results. Human studies are now in process.
The CGF166 Inner Ear Gene Therapy Research Study
Johns Hopkins is conducting the CGF166 Inner Ear Gene Therapy Research Study. This study focuses on gene therapy for the human inner ear.
Two other institutions are also involved in inner ear gene therapy studies. They include Columbia University and The University of Kansas. These are the first trials in the world to look at gene therapy to regenerate cochlear hair cells.
CDF166 is an investigational drug containing a gene that has produced hair cells during the pre-clinical trial phase.
This study’s goal is the assessment of the safety and tolerance of infusing CGF166 into the inner ear. Second, they will measure the changes in hearing before and after treatment.
Today, the only treatment for deafness due to hair cell death is a cochlear implant. The hope is to find a biologic agent to repair cochlear hair cells.
Frequency Therapeutics Trials
Frequency Therapeutics is conducting trials looking at progenitor cell stimulation. Progenitor cells can change into certain types of cells. They are unable to differentiate into as many different cells as stem cells can.
They normally only divide and develop during the fetal stage. After birth, these progenitor cells remain in the ear, but in a dormant state.
Progenitor Cell Activation, also known as PCA Regeneration, involves a new approach. This technique works to repair damaged cells and restore normal function. PCA Regeneration stimulates small molecules to awaken dormant progenitor cells present in the body.
Frequency Therapeutics has developed a proprietary combination of small-molecular drugs called FX-322. This drug’s purpose is to activate these dormant inner ear progenitor cells. The goal is to create new cochlear hair cells and improve hearing.
Scientists are considering the development of an injection form of FX-322. This would be injected into the middle ear so that it reaches the cochlea. The hope is that it will then begin regenerating the hair cells.
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