Scientists at the University of Southern California (USC) and Harvard University have come up with a new way to repair cells deep inside the ear. They have found a new drug delivery method that can make it easier for a drug to zero in on damaged nerves and cells inside the ear. The findings have been discussed in a paper published on April 4 in the international journal Bioconjugate Chemistry.
This discovery can help millions of people with hearing loss. Damage to the inside of an ear can lead to “hidden hearing loss”, which refers to difficulty in hearing whispers and soft sounds, especially in noisy places.
“What’s new here is we figured out how to deliver a drug into the inner ear so it actually stays put and does what it’s supposed to do, and that’s novel,” Charles E. McKenna, a corresponding author for the study and a chemistry professor at USC Dornsife College of Letters, Arts and Sciences, says in a statement.
“Inside this part of the ear, there’s fluid constantly flowing that would sweep away dissolved drugs, but our approach addresses this problem. This is a first for hearing loss and the ear. It’s also important because it may be adaptable for other drugs that need to be applied within the inner ear,” he says.
The drug-delivery method targets the cochlea, a snail-like structure in the inner ear where sensitive cells convey sound to the brain. Over time, hair-like sensory cells and bundles of neurons that transmit their vibrations break down, as do ribbon-like synapses, which connect the cells.
The scientists came up with the molecule by combining 7,8-dihydroxyflavone, which mimics a protein critical for development and function of the nervous system, and bisphosphonate, a type of drug that sticks to bones. The researchers say the pairing of the two delivered the novel solution as neurons responded to the molecule, regenerating synapses in mouse ear tissue that led to repair of the hair cells and neurons, which are essential to hearing.
“We’re not saying it’s a cure for hearing loss,” McKenna says. “It’s a new approach that’s extremely promising and offers a lot of hope.”
The method has yet to be tested on living animals or humans. The research has only been conducted on animal tissues in a petri dish. McKenna says that since the technique works in the laboratory, the findings provide “strong preliminary evidence” that it can work in living creatures as well.
The next phase of the research involves living animals and hearing loss cases.