Wnt activation followed by Notch inhibition promotes mitotic hair cell regeneration in the postnatal mouse cochlea

Abstract

Hair cell (HC) loss is the main cause of permanent hearing loss in mammals. Previous studies have reported that in neonatal mice cochleae, Wnt activation promotes supporting cell (SC) proliferation and Notch inhibition promotes the trans-differentiation of SCs into HCs. However, Wnt activation alone fails to regenerate significant amounts of new HCs, Notch inhibition alone regenerates the HCs at the cost of exhausting the SC population, which leads to the death of the newly regenerated HCs. Mitotic HC regeneration might preserve the SC number while regenerating the HCs, which could be a better approach for long-term HC regeneration. We present a two-step gene manipulation, Wnt activation followed by Notch inhibition, to accomplish mitotic regeneration of HCs while partially preserving the SC number. We show that Wnt activation followed by Notch inhibition strongly promotes the mitotic regeneration of new HCs in both normal and neomycin-damaged cochleae while partially preserving the SC number. Lineage tracing shows that the majority of the mitotically regenerated HCs are derived specifically from the Lgr5+ progenitors with or without HC damage. Our findings suggest that the co-regulation of Wnt and Notch signaling might provide a better approach to mitotically regenerate HCs from Lgr5+ progenitor cells.

Knockdown of Foxg1 in supporting cells increases the trans-differentiation of supporting cells into hair cells in the neonatal mouse cochlea

“…It is known that a limited number of HCs can be regenerated in newborn mice from SCs and inner ear progenitor cells, and several studies have shown that many important signaling pathways are involved in HC regeneration, such as Wnt, Notch, and Shh [7,8,[11][12][13][14][80][81][82][83][84]. Many other genes and related pathways have also been shown to play important roles in HC regeneration [85,86], and these pathways might have crosstalk with each other to affect the proliferation and differentiation of SCs and Lgr5+ progenitors [13,14]. Foxg1, one of the FOX protein family members, plays important roles in brain, eye, and ear development [24,35,36,44,45,55,57,60,64,66].…”

“…Recent studies have shown that several signaling pathways play important roles in HC regeneration by inducing the proliferation and differentiation of SCs and Lg5+ progenitors. The up-regulation of canonical Wnt signaling induces the proliferation of sensory precursors in the postnatal mouse cochlea [3,4,[11][12][13][14][15][16][17], while Notch inhibition induces mitotic generation of HCs in the mammalian cochlea via activation of the Wnt pathway [12,14,[18][19][20][21][22][23][24][25]. Also, their effect on differentiation and the generation of HCs is related to important genes such as Atoh1 and Neurog1 [26][27][28][29][30][31][32][33][34].…”

Characterizing Adult cochlear supporting cell transcriptional diversity using single-cell RNA-Seq: Validation in the adult mouse and translational implications for the adult human cochlea

“…These Lgr5-expressing cells in the neonatal cochlea possess a latent potential to proliferate and to convert into hair cells (Cox et al 2014; Stone and Cotanche 2007). This mitotic regeneration has been explored in supporting cells as a potential avenue for hair cell regeneration with Wnt activation and Notch signaling playing roles in supporting cell conversion into hair cells (Ni et al 2016; McGovern et al 2018, 2019). Consistent with these observations, protein interaction analyses suggest potentially relevant interactions between Notch signaling and Wnt signaling pathways and cell cycle control, specifically Cdkn1b (Figure 6G).…”

LIN28B controls the regenerative capacity of neonatal murine auditory supporting cells through activation of mTOR signaling

“…8 A). Inhibition of Notch signaling in combination with Wnt-activation is highly effective in stimulating hair cell production in the neonatal cochlea in vitro and in vivo (22,63). However, the effectiveness of such combined treatment has not yet been tested at later stages.…”

“…In response to hair cell death, cochlear supporting cells in newborn mice have been recently shown to re-enter the cell cycle and produce new hair cells (14,15). The injury-induced regenerative response in the neonatal/ early postnatal cochlea can be greatly enhanced by genetic or pharmacologic inhibition of Notch signaling (16)(17)(18) and/or over-activation of the Wnt/β-catenin signaling (19)(20)(21)(22). However, mice are born deaf and their cochlear hair cells and supporting cells are not functional (mature) until the onset of hearing at P12-P13 (23-25).…”