"Until now, these cells have had no clear function," said Cheng. "We used several techniques to define their behavior in cell culture dishes, as well as in mice. I hope these findings will lead to new areas of research to better understand how our ears develop and perhaps new ways to stimulate the regeneration of sensory cells in the cochlea."
Cheng recently received a grant from the California Institute for Regenerative Medicine to study the limited regeneration of the same sensory hair cells that occur in a different region of the inner ear called the vestibular system, which helps us balance. Lessons learned there may also translate into aid for patients with hearing loss.
Although regeneration of sensory hair cells does not happen naturally, recent research has suggested that the mammalian ear may harbor a sub-population of presumably inactive progenitor cells. The research team led by Cheng and Nusse used a strain of laboratory mice that allowed the scientists to track the activation of a cell-signaling pathway driven by a protein called Wnt. The Wnt pathway has previously been shown to be involved in many developmental functions, and it drives the renewal and proliferation of many types of stem cells.
"We wanted to investigate the Wnt pathway because of its tremendous influence in the development and regeneration of many other organs," said Cheng.
The researchers found that tympanic border cells, or TBCs, which form a thin layer under the sensory epithelium, are actively dividing in mice during the first three weeks after birth (the time corresponding to about the first trimester of human development, during which the ability to hear is established) and give rise to at least a subset of sensory and non-sensory cells in the ear.
|Contact: Krista Conger|
Stanford University Medical Center