Research & Innovation
Most cases of deafness are caused by the dysfunction or death of cells in the cochlea, the snail-shell-shaped structure in the inner ear. The laboratory of Douglas Cotanche, PhD, formerly a researcher in Children's Department of Otolaryngology, was able to grow all the assorted cell types in the cochlea from just one source: neural stem cells.
Neural stem cells were first isolated from mice in 1998 by Evan Snyder, MD, PhD, formerly of Children's Department of Neurology. Cotanche's team implanted the cells deep inside the sound-damaged cochleas of guinea pigs and mice. Six weeks later, the cells had migrated throughout the cochlea and formed satellite cells, spiral ganglion cells and Schwann cells, which make up the cochlea's nervous tissue, as well as the hair cells and supporting cells of the organ of Corti (the actual hearing organ).
The researchers couldn't show complete rebuilding of the cochlea, but they believe that with more time and more stem cells, most of the cochlea could be repopulated. The next step is to implant human neural stem cells in animals and test whether the new cochlear cells connect with the auditory nerve and the brain, and whether they respond to sound stimulation—in other words, whether they restore hearing.
Gene-therapy trial will attempt to restore hearing in deaf mice
In the Journal of Clinical Investigation, a team co-led by Jeffrey Holt, PhD, of the Department of Otolaryngology at Children’s Hospital Boston demonstrated that two related proteins, TMC1 and TMC2, are essential for normal hearing – paving the way for a test of gene therapy to reverse a type of genetic deafness.
“This is the first time anything like this has been done,” says Holt.