Direct reprogramming adult fibroblast into cells with partial inner ear hair cell characteristics through cell activation and signal directed approach.

Loss of inner ear hair cell (HC) is an irreversible process in mammals and is the most common cause of human hearing and balance disorders especially in the elderly. Cell therapy based on highly scalable generation of HC linage and inner ear transplantation is one of the most promising therapeutic approaches for HC impairment. For fibroblast is quite abundant and readily available in human body, it is an ideal endogenous cell source to generate HC lineage for transplantation purpose. In the present study, by using a cell activation and signaling directed method, we demonstrate that adult fibroblast can be direct reprogrammed into a kind of cell which expresses lots of HC markers. At the same time, an intermediate progenitor stage exists during such a lineage conversion and activation of FGF pathway is critical for its formation. Although these reprogrammed cells still lack some of the key features of HC such as mechanosensitive ion channel hence have not acquired the functional properties of HC, the findings reported here raise the possibility of reprogramming endogenous fibroblasts into functional HC for regenerative purpose.