Expression of Atoh1, Gfi1, and Pou4f3 in the mature cochlea reprograms non-sensory cells into hair cells

Mechanosensory hair cells of the mature mammalian organ of Corti do not regenerate, and loss of hair cells leads to permanent hearing loss. Although non-mammalian vertebrates are able to regenerate hair cells by the division and transdifferentiation of adjacent supporting cells, many humans with severe hearing loss completely lack hair cells and supporting cells, with the organ of Corti being replaced by a flat epithelium of non-sensory cells To determine if mature non-sensory cells can produce hair cells in vivo, we reprogrammed non-sensory cells of the mature cochlea with three hair cell transcription factors, Gfi1, Atoh1, and Pou4f3. We were able to generate significant numbers of hair cell-like cells in the non-sensory inner and outer sulci of the cochlea after 2 weeks of reprogramming. New hair cells continued to be added to the non-sensory regions of the cochlea over the next seven weeks, and expressed hair cell proteins such as Myosin VIIa, parvalbumin, and prestin and formed stereociliary hair bundles. We confirmed the identity of these cells by high depth single cell RNA-seq. Significantly, cells adjacent to converted hair cells expressed markers of supporting cells, suggesting that transcription factor reprogramming of non-sensory tissue in the adult animal can generate mosaics of sensory cells similar to those seen in the organ of Corti. Generating such sensory mosaics by reprogramming may represent a potential strategy for hearing restoration in humans. FACS sorted adult mouse cochlear cells from control (Fbxo2CreERT2::Rosa26-tdTomato) animals and experimental (Fbxo2CreERT2::Rosa26-tdTomato::Rosa26-GAP) animals based on tdTomato and EpCAM flourescnece.