Defective Tmprss3-Associated Hair Cell Degeneration in Inner Ear Organoids

Abstract

Summary Mutations in the gene encoding the type II transmembrane protease 3 ( TMPRSS3 ) cause human hearing loss, although the underlying mechanisms that result in TMPRSS3 -related hearing loss are still unclear. We combined the use of stem cell-derived inner ear organoids with single-cell RNA sequencing to investigate the role of TMPRSS3. Defective Tmprss3 leads to hair cell apoptosis without altering the development of hair cells and the formation of the mechanotransduction apparatus. Prior to degeneration, Tmprss3 -KO hair cells demonstrate reduced numbers of BK channels and lower expressions of genes encoding calcium ion-binding proteins, suggesting a disruption in intracellular homeostasis. A proteolytically active TMPRSS3 was detected on cell membranes in addition to ER of cells in inner ear organoids. Our in vitro model recapitulated salient features of genetically associated inner ear abnormalities and will serve as a powerful tool for studying inner ear disorders.

Application of Mesenchymal Stem Cell Therapy and Inner Ear Regeneration for Hearing Loss: A Review

“…This result indicated a disruption in intracellular homeostasis. In addition to the endoplasmic reticulum (ER) of cells, a proteolytically active TMPRSS3 was detected in the cell membranes [60].…”

Progress in Modeling and Targeting Inner Ear Disorders with Pluripotent Stem Cells

“…On the other hand, 3D inner ear organoids contain both sensory epithelia (hair cells and supporting cells) and sensory neuron-like cells ( Figure 3 ) ( Jeong et al., 2018 , Koehler et al., 2013 , Koehler et al., 2017 ). Furthermore, several studies have replicated these protocols ( DeJonge et al., 2016 , Schaefer et al., 2018 ) and used the systems for different applications, such as electrophysiological studies and disease modeling ( Liu et al., 2016 , Tang et al., 2019 ). Although further characterization of sensory neuron-like cells is still in need, the inner ear organoid system provides a powerful tool to study peripheral sensory neural networks in the inner ear in vitro .…”

“…Mutations in TMPRSS3 cause congenital or early-onset hearing loss in humans ( Scott et al., 2001 ), yet the functional role of TMPRSS3 in the inner ear is not fully understood. ESC-derived organoids from Tmprss3 Y260X mice show normal hair cell development followed by hair cell degeneration at differentiation day 38 (equivalent to ∼P14 in mouse) ( Tang et al., 2019 ). These observations are comparable with phenotypes observed in Tmprss3 Y260X mice.…”

Membrane-anchored serine proteases as regulators of epithelial function

“…Similarly, mice lacking a functional Tmprss3 protein exhibit severe loss of hearing associated with rapid degeneration of cochlear and vestibular hair cells [80]. Prior to degeneration, loss of Tmprss3 reduced the number of Ca 2+ -activated K + (BK) channels and decreased expression of several intracellular calcium-binding proteins in cultured primary hair cells, and decreased expression of the α subunit of the BK channel and a loss of BK-dependent fast K + conductance within the cochlea of Tmprss3-deficient mice [81,82]. Furthermore, activation of the wildtype, but not the deafness-causing variants of Tmprss3 increases amiloride-sensitive sodium transport in a Xenopus oocyte expression system, indicating that the protease could potentially be involved in activation of inner ear-expressed ENaC [49].…”