In recent years, we have seen numerous advances in treating hearing loss. Because hearing loss may be caused by various factors, including age, noise exposure, and genetics, it is necessary for researchers to find solutions for several different types of hearing loss.
One of the most exciting recent developments in hearing loss treatment is in the field of hereditary hearing loss. Researchers at Case Western Reserve University School of Medicine explored the effects of medications on hereditary hearing loss. They specifically focused on a particular protein that, when there are mutations, disrupts hearing ability. This mutant protein is present in patients with Usher syndrome, which leads to genetic hearing loss.
In order to hear properly, proteins must be able to reach the outer membrane of sensory cells in the inner ear. When there are mutations on these proteins, however, they become trapped within the hair cells. This causes them to become ineffective and unable to survive, which disrupts the patient’s hearing and balance. These important proteins are referred to as protein clarin1.
As part of this study, researchers focused on protein clarin1 in zebrafish. These zebrafish were genetically modified to have human versions of protein clarin1. Some zebrafish were given normal clarin1, while others were given mutant clarin1. Just as in humans, the researchers observed that the zebrafish with the mutant protein displayed signs of disrupted hearing and balance, while those with the normal protein did not.
In fact, because zebrafish larvae are transparent, the researchers were able to closely observe the function of protein clarin1. The mutant clarin1 became trapped in the tubules of the cell membrane. Based on this observation, researchers hypothesized that if the protein were to be freed from the cell membrane, the fish may experience corrected hearing and balance.
To achieve this, researchers tested two drugs: thapsigargin (an anti-cancer drug) and artemisinin (an anti-malarial drug). While both drugs worked to free the trapped protein and allow it to rise in the membrane, artemisinin worked more effectively. In addition to observing the liberation of the protein clarin1, researchers also observed an improvement in the hearing and balance of the fish.
Zebrafish must be able to swim normally in order to survive, and this ability is closely tied to their balance and ability to detect water movement. Both of these essential functions are related to hair cell performance. In zebrafish with the mutant protein that was treated with artemisinin, survival rates improved from 5 percent to 45 percent.
Although this study was completed using zebrafish, the researchers feel hopeful that similar positive results will be seen in humans. Further testing and studies are needed, but they believe this anti-malarial drug may hold the key to treating hereditary hearing loss linked to the mutant protein clarin1. They also believe this same treatment could be successfully used to alleviate vision loss also caused by clarin1 mutations.
If you would like to learn more about this exciting new research and other developments in hearing loss solutions, we welcome you to contact our audiology practice today. We look forward to meeting you!