When cochlear cells within the ear are damaged from exposure to high levels of noise, long-term, permanent hearing loss can occur. Because this hearing loss is associated with damaged cells, researchers have reasoned that replacing those cells with stem cells may provide a means for reversing noise-induced hearing loss. A recent study, published in the journal Neurobiological Disorders has shown that the transplant of epithelial stem cells can in fact help with this type of hearing loss.
The stem cells that were used in the study were isolated from the tongue and were shown to have the ability to survive and proliferate outside the body. Once transplanted, they were also shown to survive and to integrate themselves appropriately.
The auditory brainstem response (ABR) threshold test was used before and after transplantation to determine whether the stem cells actually impacted hearing loss level. The ABR test is a neurological test that assesses whether the brainstem responds to auditory clicking sounds. The test was developed in 1971 and is now the most widely used test for evaluating responses to auditory stimuli. The test reveals the threshold at which noise can produce a response, with lower thresholds indicating better auditory functioning.
Compared to before the transplantation, tests performed 4 weeks after transplantation showed that the stem cell transplants were associated with lower ABR thresholds. Thus, not only did the stem cells survive, proliferate, and integrate normally within the ear, but they were also associated with improved auditory abilities.
These results indicate that stem cells are a promising candidate for reversing long-term hearing loss that is caused by noise-induced damage to cells of the inner ear. Further research will help to clarify the best ways these cells may be used to reverse hearing loss and to what extent their application can benefit those who have suffered noise-induced hearing loss. It is also possible that the relevant research will help reveal ways that stem cells can be used to help those who suffer from other types of hearing loss as well.
Sullivan, J.M., Cohen, M.A., Pandit, S.R., Sahota, R.S., Borecki, A.A., & Oleskevich, S. (2011). Effect of epithelial stem cell transplantation on noise-induced hearing loss in adult mice. Neurobiological Disorders. 41(2), 552-559.