Inner Ear Organoids: Recapitulating Inner Ear Development in 3D Culture

Abstract

The inner ear contains sensory epithelia composed of mechanosensitive hair cells, supporting cells, and sensory neurons that work in concert to detect sound and positional information and transmit those signals to the brain. Within the backdrop of embryogenesis, inner ear development follows an intricate pathway of signaling cues and morphological changes, leading to its complex final three-dimensional (3D) structure. Application of various small molecules and recombinant proteins to mouse embryonic stem cells at specific time points in vitro has enabled recapitulation of developmental cues with subsequent formation of inner ear organoids. This has resulted in a model system of inner ear development that is easily derived, manipulated, and analyzed. These organoids contain functional mechanosensitive hair cells, supporting cells, and sensory neurons, which phenocopy functional components of the inner ear responsible for detection of positional information. The potential applications of this system include investigation of inner ear development, disease modeling, drug screening, and therapy development. This chapter highlights the process of in vivo inner ear development, the rationale and process behind inner ear organoid formation, and potential applications and limitations of this in vitro model system.