Researchers at the University of Sheffield have developed a possible cure for deafness that utilizes human embryonic stem cells, turning them into ear cells.
The researchers found that when they transplanted human embryonic stem cells into deaf gerbils, the gerbils gained an average "functional recovery" of 46%. This recovery took only four weeks from when the cells were first administered.
“We developed a method to drive human embryonic stem cells to produce both hair cells and neurons, or nerve cells, but we only transplanted the neurons," said Dr. Marcelo Rivolta, Reader in sensory stem cell biology at the university and lead on the project. "We then used a technique called auditory brainstem evoked responses (ABR), which measures if the brain can perceive an electrical signal after sound stimulation. The responses of the treated animals were substantially better than those untreated, although the range of improvement was broad. Some subjects did very well, while in others recovery was poor.”
The specific type of deafness that the cells cured, researchers said, is similar to a human condition called auditory neuropathy, which is a deafness that occurs "at the level of the cochlear nerve," and has to do with the connection of the ear's hair cells with the brain. They estimate that 15% of the worldwide population with profound hearing loss have the condition. People can be born with auditory neuropathy, though the researchers said that growing evidence indicates factors such as jaundice at birth and noise exposure later in life can be risk factors.
“We believe this an important step forward," said Rivolta. "We have now a method to produce human cochlear sensory cells that we could use to develop new drugs and treatments, and to study the function of genes. And more importantly, we have the proof-of-concept that human stem cells could be used to repair the damaged ear."
Rivolta did state, however, that more research is needed, including research on the long-term effects of the treatment. He also said that auditory neuropathy patients who do not have hair cells might require a cochlear implant in conjunction with the stem cell treatment.
The study was undertaken with funding from the U.K. Medical Research Council and the U.K. research charity Action on Hearing Loss.
(Image courtesy the University of Sheffield)