Over the years, hearing loss has been a burden of disease globally. About 430 million individuals suffer from hearing loss worldwide. As populations age, these numbers are likely to rise. In hopes of alleviating this problem, recent advancements in science are investigating the regeneration and protection of ear cell components through genetic alteration strategies.
Hearing loss is a condition wherein the transmission of sound from the ear to the brain is disrupted. It has three types — sensorineural, conductive, or mixed.
Harvard scientists have developed a new drug-like cocktail that aims to reverse hearing loss. It works by altering some gene pathways in the inner ear to regenerate hair cells.
The new drug-like cocktail was able to produce functioning hair cells — however, the time frame of the research was not able to determine if these cells can survive long-term.
Further research is needed to investigate its clinical application to humans, specifically, its ability to reverse hearing loss in the elderly and its long-term survivability.
Here, we explore a promising drug-like cocktail that may potentially contribute to reversing hearing loss.
What is hearing loss?
Hearing loss is a condition wherein the transmission of sound from the ear to the brain is disrupted, leading to a partial or complete decrease in one's ability to hear sounds.
Signs and symptoms of hearing loss include:
- Being unresponsive to sounds.
- Mispronouncing words or speech difficulties.
- Trouble hearing and understanding what other people are saying.
- Requesting verbal repetitions from others.
- Watching TV or listening to music at a volume that is louder than necessary.
- Hearing issues while on the phone which make it difficult to follow a conversation.
- Feeling worn out or under pressure from trying to focus while listening.
What is the new drug-like cocktail made of?
Scientists from Harvard Medical School developed a new hearing loss treatment composed of a drug-like cocktail of several compounds. These compounds successfully altered some gene pathways in the inner ear to regenerate ear hair cells in a mouse model.
Damaged ear hair cells contribute to the development of hearing loss. Hence, the scientists developed a cocktail and used it to treat normal adult mice with damaged hair cells.
The cocktail is composed of:
- Small molecule drug-like compounds
- Small interfering RNAs (siRNAs)
They also introduced a functional gene called the Atoh1 into the cocktail-treated inner ear using gene therapy technology. Atoh1 is a gene that, when defective, leads to degeneration of ear hair cells and causes adult hearing loss.
How does it work?
The basis of this new hearing loss treatment lies in the concept of gene therapy. Human gene therapy aims to change an expression of a gene or the biological characteristics of living cells for therapeutic purposes.
Gene therapy can function in a variety of ways, including:
- Swapping out a disease-causing gene for a healthy copy.
- Deactivating a malfunctioning disease-causing gene.
- Adding a new or altered gene to the organism to treat a condition.
The drug-like cocktail works by activating two important pathways — Myc and Notch pathways — and the delivery of Atoh1 gene which are all crucial in the regeneration and protection of new hair cells in the ear, leading to the reversal of certain aspects of hearing loss.
Can the new treatment reverse hearing loss?
With the help of cutting-edge imaging technology and other methods, the researchers confirmed that the new ear hair cells were functional.
However, the time frame of the research was not able to determine if the regenerated hair cell-like cells can survive long-term. Additionally, there is still no evidence of its clinical application in humans — specifically its ability to reverse hearing loss in the elderly. Further research and large-scale clinical trials are needed to establish its long-term safety and efficacy in humans.
Potential risks of the new drug cocktail
The 'cochleostomy' surgical treatment currently used to administer the new drug cocktail may cause substantial harm to the microenvironment of the cochlea in adult ears — including extensive hair cell death near the injection site. Future research could lead to a further increase in hair cell regeneration efficiency without harming the inner ear. This could be achieved by adopting an alternative delivery vehicle with a minimally invasive surgical method or implementing new strategies.
When will the drug cocktail be available?
The drug test was only applied to a mouse model and is not yet applicable to human applications.
Before applying to begin human trials, researchers are continuously studying and improving their therapy technique in larger animal models. They point out that additional study is required to address the restrictions and difficulties associated with treating the inner ear. Scientists are investigating various gene therapy and surgical approaches, including one developed at Mass Eye and Ear in which adeno-associated virus (AAV) — a distinct viral vector — was able to precisely and securely deliver gene therapy to the inner ear through a novel surgical procedure.
How to get involved in this research?
This specific drug cocktail is not yet available to the public but if you want to participate in the drug trials, you can explore its availability in the future or other ongoing research through Mass General Brigham.
Overall, the new drug-like cocktail is promising in reversing hearing loss — however, it is still in its early developments. It works by activating two important pathways needed to produce new hair cells in the ear. It delivers the Atoh1 gene that may counter the degeneration of inner ear hair cells, which are all important in our hearing mechanism. Further development of this novel drug-like cocktail might be a potential treatment for individuals suffering from hearing loss and ultimately improve their quality of life in the future.
At what age does hearing loss begin?
The age at which hearing loss begins occurs most commonly in the age range of 40 to 59 years old. Less commonly, it can occur as early as 6 to 19 years old. Rarely, it can occur among newborns and children aged 1 to 5 years.
Is hearing loss permanent?
Occasionally, hearing loss may be temporary — however, if important ear structures are irreparably harmed, the damage can become permanent. Any ear damage could result in hearing loss. In most cases, damage to the auditory nerve system or inner ear is irreversible or permanent.
How do you fix hearing loss?
Hearing loss can be treated in several ways, including through medical intervention and listening devices like hearing aids. The cause and extent of hearing loss determine the course of treatment. Although there is no cure for age-related hearing loss, hearing aids, and other listening devices can help treat the condition and enhance quality of life.
- Proceedings of the National Academy of Sciences of the United States of America. Reprogramming by drug-like molecules leads to regeneration of cochlear hair cell-like cells in adult mice.
- StatPearls. Hearing loss.
- Centers for Disease Control and Prevention. Types of hearing loss.
- The New England Journal of Medicine. Hearing loss in adults.
- National Institute on Deafness and Other Communication Disorders. Noise-induced hearing loss.
Show all references
- National Institute on Deafness and Other Communication Disorders. Sudden deafness.
- United States Food and Drug Administration. What is gene therapy?
- Mass General Brigham. Participate in research.
- National Institute on Deafness and Other Communication Disorders. Age at which hearing loss begins.
- University of California San Francisco. Hearing loss treatments.