Mouse embryonic stem cells were transformed into key structures of the inner ear by Indiana University scientists. The discovery provides new insights into the sensory organ's developmental process and sets the stage for laboratory models of disease, drug discovery and potential treatments for hearing loss and balance disorders.
A research team led by Eri Hashino, Ph.D., Ruth C. Holton Professor of Otolaryngology at Indiana University School of Medicine, reported that by using a three-dimensional cell culture method, they were able to coax stem cells to develop into inner-ear sensory epithelia -- containing hair cells, supporting cells and neurons -- that detect sound, head movements and gravity. The research was reportedly online Wednesday in the journal Nature
Previous attempts to "grow" inner-ear hair cells in standard cell culture systems have worked poorly in part because necessary cues to develop hair bundles -- a hallmark of sensory hair cells and a structure critically important for detecting auditory or vestibular signals -- are lacking in the flat cell-culture dish. But, Dr. Hashino said, the team determined that the cells needed to be suspended as aggregates in a specialized culture medium, which provided an environment more like that found in the body during early development.
The team mimicked the early development process with a precisely timed use of several small molecules that prompted the stem cells to differentiate, from one stage to the next, into precursors of the inner ear. But the three-dimensional suspension also provided important mechanical cues, such as the tension from the pull of cells on each other, said Karl R. Koehler, B.A., the paper's first author and a graduate student in the medical neuroscience graduate program at the IU School of Medicine.