# Crosstalk Signaling Between the Epithelial and Non-Epithelial Compartments of the Mouse Inner Ear

## TL;DR

This study explores how different cell types in the mouse inner ear communicate during development, revealing important signaling pathways.

## Contribution

The study provides new insights into epithelial and non-epithelial cell interactions in the developing mouse utricle using single-cell RNA sequencing.

## Key findings

- Mesenchymal cells are the main signal senders in postnatal mouse utricle development.
- Epithelial and mesenchymal cells communicate via TGFβ and pleiotrophin pathways.
- The study reveals dynamic crosstalk between different cell populations in the inner ear.

## Abstract

The otolith organs of the inner ear consist of the utricle and saccule that detect linear acceleration. These organs rely on mechanosensitive hair cells for transduction of signals to the central nervous system. In the murine utricle, about half of the hair cells are born during the first postnatal week. Here, we wanted to explore the role and interaction of the non-epithelial mesenchymal cells with the sensory epithelium and provide a resource for the auditory neurosciences community.

We utilized full-length Smart-seq2 single-cell RNA sequencing at postnatal days 4 and 6 along with a host of computational methods to infer interactions between the epithelial and non-epithelial compartments of the mouse utricle. We validated these findings using a combination of immunohistochemistry and quantitative multiplex in situ hybridization.

We report diverse cell–cell crosstalk among the 12 annotated cell populations (n = 955 cells) in the developing neonatal mouse utricle, including epithelial and non-epithelial cellular signaling. The mesenchymal cells are the dominant signal senders during the postnatal period. Epithelial to mesenchymal signaling, as well as mesenchymal to epithelial signaling, are quantitatively shown through the TGFβ and pleiotrophin pathways.

This study highlights the dynamic process of postnatal vestibular organ development that relies not only on epithelial cells, but also on crosstalk between spatial compartments and among different cell groups. We further provide a data-rich resource for the inner ear community.

The online version contains supplementary material available at 10.1007/s10162-025-00980-7.