Inhibition of Notch signaling allows for hair cell regeneration in gentamicin damaged cochlea.

<p><b>A–C:</b> Hair cell phenotype in control (A, A'), gentamicin +DMSO (B, B') and gentamicin +DAPT (C, C') treated cultures after a total of 3 DIV. Atoh1/nGFP expression (green) labels hair cell nuclei and myosin VI immuno-staining marks hair cells (Myo6, red). All images shown are from the cochlear mid apical region. <b>A</b>'<b>–C</b>': higher magnification of A–C. Asterisk in B' mark faint nGFP expression in inner phalangeal cells. Scale bar 50 μm. <b>D:</b> Quantification of hair cell density in mid apex, mid base and base of gentamicin + DMSO (grey) and gentamicin +DAPT (red) treated cochlea cultures after 3 DIV. Data expressed as mean ±SEM (n = 3, cochlea explants from 2 independent experiments; ** <i>p-</i>value <0.005; * <i>p-</i>value ≤0.05). <b>E–J:</b> EdU (green) incorporation in control (E, F), gentamicin +DMSO (G, H) and gentamicin +DAPT (I, J) treated cultures. All images shown are from the cochlear mid apical region. <b>E, G, I:</b> Confocal images of hair cell layer. Myosin VI immuno-staining marks hair cells (Myo6, red). <b>F, H, J</b>: Projections of confocal z-stacks, imaging supporting cell layer. Sox2 immuno-staining (blue) marks supporting cells. No EdU positive hair cell (Myo6, red) or EdU positive supporting cell nuclei (Sox2, green) are observed in control (E, F), gentamicin (G, H), or gentamicin +DAPT (I, J) treated cochlea cultures. White arrows in J mark EdU positive cells at the lateral edge of sensory epithelium. Scale bar 50 μm.