Lineage-tracing and translatomic analysis of damage-inducible mitotic cochlear progenitors identifies candidate genes regulating regeneration

Abstract

Cochlear supporting cells (SCs) are glia-like cells critical for hearing function. In the neonatal cochlea, the greater epithelial ridge (GER) is a mitotically quiescent and transient organ, which has been shown to nonmitotically regenerate SCs. Here, we ablated Lgr5+ SCs using Lgr5-DTR mice and found mitotic regeneration of SCs by GER cells in vivo. With lineage tracing, we show that the GER houses progenitor cells that robustly divide and migrate into the organ of Corti to replenish ablated SCs. Regenerated SCs display coordinated calcium transients, markers of the SC subtype inner phalangeal cells, and survive in the mature cochlea. Via RiboTag, RNA-sequencing, and gene clustering algorithms, we reveal 11 distinct gene clusters comprising markers of the quiescent and damaged GER, and damage-responsive genes driving cell migration and mitotic regeneration. Together, our study characterizes GER cells as mitotic progenitors with regenerative potential and unveils their quiescent and damaged translatomes.

Development and transdifferentiation into inner hair cells require Tbx2

“…It is known that those SCs in GER regions are plastic and can replenish themselves after damage at neonatal, but not adult cochleae 28,39 . In agreement with normal Tbx2 in the SCs, further ectopic Tbx2 cannot convert IBCs/IPhs into new HCs or new IHCs.…”

“…The non-sensory SCs including IBCs/IPhs that localize in the medial cochlear portion and close to IHCs are plastic and can replenish themselves after damage in neonatal cochleae [ 28 , 38 ]. Determining how functional IHCs can be regenerated from these cochlear non-sensory SCs is a long-term goal in the inner-ear biology field.…”

Tbx2 is essential for cochlear inner hair cell development and regeneration

“…1). It is known that those SCs in GER regions are plastic and can replenish themselves after damage at neonatal, but not adult cochleae 28,39 . In agreement with normal Tbx2 in the SCs, further ectopic Tbx2 cannot convert IBCs/IPhs into new HCs or new IHCs.…”

Single cell RNA sequencing analysis of mouse cochlear supporting cell transcriptomes with activated ERBB2 receptor, a candidate mediator of hearing restoration mechanisms.

“…This contrasts to robust stemlike capacity in isolated cells from the adult utricle 68, 69 , which correlates with limited regeneration potential in that organ 70 . These data may be interpreted to mean that cochlear stem cells, perhaps resident in GER 71 , are lost during maturation. It is also possible that their requirements for survival or for identity maintenance differ.…”