Humans have only about 15,000 sound sensitive hair cells in each ear, and unlike birds, fish and amphibians, these cells can’t regenerate themselves once damaged. The damage can be caused by noise, head injury, infectious disease and certain medicines, as these hair cells are sensitive to their environment.
While we can’t regenerate the hair cells, we may be able to prevent the noise and drug induced hearing loss. Researchers at the St. Jude Children’s Hospital have tested over 4,000 drugs for their ability to protect hair cells against cisplatin, a common chemotherapy agent used to treat cancer, that causes irreversible hearing loss in up to 70% of patients. The researchers have focused on finding a drug that can inhibit an enzyme called cyclin-dependent kinase 2 (CDK-2), and have found 10 that seem to work.
The researchers then centered their research on Kenpaullone, one of the tested compounds, and injected it into the ears of a mouse. Kenpaullone, a CDK-2 inhibitor, was successfully able to protect the hair cells in the mouse’s ear from sounds up to 100 decibels. The test results show that Kenpaullone is more effective than any other of the four compounds that are currently being tested in clinical trials to treat hearing loss.