Dual expression of Atoh1 and Ikzf2 promotes transformation of adult cochlear supporting cells into outer hair cells

Abstract

Mammalian cochlear outer hair cells (OHCs) are essential for hearing. Severe hearing impairment follows OHC degeneration. Previous attempts at regenerating new OHCs from cochlear supporting cells (SCs) have been unsuccessful, notably lacking expression of the key OHC motor protein, Prestin. Thus, regeneration of Prestin+ OHCs represents a barrier to restore auditory function in vivo. Here, we reported the successful in vivo conversion of adult mouse cochlear SCs into Prestin+ OHC-like cells through the concurrent induction of two key transcriptional factors known to be necessary for OHC development: Atoh1 and Ikzf2. Single cell RNA sequencing revealed the upregulation of 729 OHC genes and downregulation of 331 SC genes in OHC-like cells. The resulting differentiation status of these OHC-like cells was much more advanced than previously achieved. This study thus established an efficient approach to induce the regeneration of Prestin+ OHCs, paving the way for in vivo cochlear repair via SC transdifferentiation.

Tbx2 is essential for cochlear inner hair cell development and regeneration

“…Furthermore, the reprogramming efficiency by Atoh1 and Tbx2 is 29.5%, which was higher than the 17.8% by Atoh1 alone 18 . Collectively, we proposed that synergistic interactions between Atoh1 and Tbx2 are present during the cell fate conversion process, as the case between Atoh1 and Ikzf2 in our OHC regeneration study 20 , or between Atoh1 and Pou4f3 during the endogenous HC development 38 . However, the puzzle is why the neonatal IBCs/IPhs that express the endogenous Tbx2 cannot become vGlut3+ new IHCs when ectopic Atoh1 is induced 18 .…”

“…Due to the similarity between iOHCs and the endogenous OHCs, we predicted that Ikzf2 protein (also known as Helios), which is a key regulator for OHC development 16,20 , would be expressed in these iOHCs. Due to lack of good commercial Ikzf2 antibody for immunostaining, we constructed a new knockin mouse strain, Ikzf2 *3xV5-P2A-Tdtomato/+ (abbreviated as Ikzf2 V5/+ ) where three V5 tags were fused with Ikzf2 at its C-terminus (Fig.…”

Molecular Pathways Modulating Sensory Hair Cell Regeneration in Adult Mammalian Cochleae: Progress and Perspectives

“…Ikzf2 has recently been shown to be crucial for OHC fate and maturation, as prestin and oncomodulin expression is lost in Ikzf2-mutant mice [ 73 ]; contrarily, overexpression of Ikzf2 in IHCs leads to downregulation of IHC genes and upregulation of OHC genes. Transformation of adult cochlear SCs into prestin-positive OHCs with concurrent stimulation if Athoh1 and Ikzf2 supports the role of Ikzf2 in transdifferentiation [ 93 ]. Hes6 has also been implicated in the differentiation of mammalian HCs [ 94 ].…”

Regeneration of Hair Cells in the Human Vestibular System

“…Moreover, the regenerated hair cells were immature, as demonstrated by immature cilia ( Schlecker et al, 2011 ; Taylor et al, 2018 ; Sayyid et al, 2019 ; Qian et al, 2021 ). Recent studies report some progresses in cochlear hair cell regeneration by manipulating multiple signaling pathways or transcriptional factors ( Walters et al, 2017 ; Lee et al, 2020 ; Menendez et al, 2020 ; Chen et al, 2021 ; Sun et al, 2021 ). In order to improve both the quality and quantity of new vestibular hair cells, regulating multiple factors which can promote the maturation and subtype differentiation of vestibular hair cells may be an important strategy.…”