Conditional overexpression of neuritin in supporting cells (SCs) mitigates hair cell (HC) damage and induces HC regeneration in the adult mouse cochlea after drug-induced ototoxicity

Hearing loss due to the loss of auditory hair cells is normally irreversible because mammalian hair cells do not regenerate. Using neurotrophic factors to induce the regeneration of hair cells (HCs) from adjacent nonsensory supporting cells (SCs) may be a promising strategy to treat hearing loss. Here, we demonstrate that overexpression of neuritin in SCs could mitigate drug-induced HC damage and directly induce HC regeneration from SCs by inhibiting the Notch signaling pathway. Using neuritin conditional knock-in mice, we found that upregulation of neuritin in SCs results in preserved HCs and partial recovery of hearing, inducing the regeneration of HCs from the transdifferentiation of SCs in ears damaged by kanamycin. Furthermore, neuritin overexpression in SCs downregulates the expression levels of Notch receptor Notch intracellular domain (NICD) and hairy and enhancer of split-1 (HES1) protein, two core components of the Notch signaling pathway. These observations confirmed in vitro that in cultured neonatal mouse cochleae, neuritin overexpression in SCs significantly inhibited gentamicin-induced HC damage and induced regeneration of HCs from the transdifferentiation of SCs, and that these effects were eliminated by adding the Notch ligand Jagged-1. These findings may provide a new avenue to stimulate HC regeneration after HC loss and highlight the therapeutic potential of neuritin for sensorineural hearing loss.