Stepwise Induction of Inner Ear Hair Cells From Mouse Embryonic Fibroblasts via Mesenchymal- to-Epithelial Transition and Formation of Otic Epithelial Cells

Abstract

Although embryonic stem cells or induced pluripotent stem cells are able to differentiate into inner ear hair cells (HCs), they have drawbacks limiting their clinical application, including a potential risk of tumourigenicity. Direct reprogramming of fibroblasts to inner ear HCs could offer an alternative solution to this problem. Here, we present a stepwise guidance protocol to induce mouse embryonic fibroblasts to differentiate into inner ear HC-like cells (HCLs) via mesenchymal-to-epithelial transition and then acquisition of otic sensory epithelial cell traits by overexpression of three key transcription factors. These induced HCLs express multiple HC-specific proteins, display protrusions reminiscent of ciliary bundle structures, respond to voltage stimulation, form functional mechanotransduction channels, and exhibit a transcriptional profile of HC signature. Together, our work provides a new method to produce functional HCLs in vitro, which may have important implications for studies of HC development, drug discovery, and cell replacement therapy for hearing loss.

Modelling inner ear development and disease using pluripotent stem cells – a pathway to new therapeutic strategies

“…LGR5 + supporting cells from neonatal and adult mice and an adult human, and cochlear greater epithelial ridge ( Box 1 ) cells from neonatal mice have been used to produce organoids that generate hair cell-like and supporting cell-like cells without the induction of other cell types ( Kubota et al, 2021 ; McLean et al, 2017 ). Similar results have been achieved using mouse embryonic fibroblasts, in which direct overexpression of otic lineage genes, including the transcription factors Sox2 and Six1 , and the transcriptional co-activator Eya1 , generated sensory epithelial progenitors and subsequent hair cell-like cells ( Yang et al, 2021 ).…”

Stem cells as potential therapeutics for hearing loss

“…Direct reprogramming of fibroblasts into HCLs of the inner ear could be a viable alternative. Mouse Embryonic Fibroblasts can be differentiated into HCLs via mesenchymal-to-epithelial transition, followed by increased the expression of three important transcription factors, Sox2, Eya1 and Six1, to induce ear-sensory epithelial cell characteristics ( Yang et al, 2021 ). Conductive hearing loss is commonly caused by cerumen embolism and chronic otitis media, leading to perforation of the tympanic membrane and erosion of the auditory ossicles due to recurrent infections.…”