Reprogramming of cochlear supporting cells by MYC/NICD co-activation.

Strategies to overcome irreversible cochlear hair cell (HC) damage and loss are of vital importance to develop a treatment for hearing loss. HC regeneration in adult cochlea relies on a two-phase process: 1) Reprogramming mature cochlear (SCs) to regain the properties of their younger selves; 2) Activating Atoh1, a gene responsible for HC fate-determining, in the reprogrammed adult SCs for HC regeneration. We have shown that, by transient co-activation of Myc and NICD (Notch1 intracellular domain), the adult mouse cochlea can be successfully reprogrammed to a relatively younger stage and regain progenitor capacity, with the regeneration of HCs following Atoh1 overexpression in vitro and in vivo. To identify molecules to reprogram mature cochlear SCs, we utilized single-cell RNA sequencing and uncovered the pathways and their target genes underlying MYC/NICD-mediated reprogramming. We used an in-house adult cochlea explant culture system and carried out single-cell RNA sequencing to examine the gene expression profiles of cochlear explants from a transgenic mouse model, rtTa/tet-Myc/-tet-NICD, in response to Dox-induced MYC/NICD co-activation. We have shown that a 4-day treatment by Dox in cultured adult rtTa/tetMyc/-tet-NICD cochleae was sufficient to reprogram adult SCs for HC regeneration. We treated whole adult cochlear explants (rtTa/tet-Myc/-tet-NICD) with Dox in vitro for four days before dissecting sensory epithelium to create cDNA libraries subjected to 10X Genomics pipeline barcoding, library preparation, and sequencing. (Control, sterile water, n=4; and Dox-administered, n=8)