LGR5 and SOX2 expressing progenitor cells in the adult and aged human and mouse inner ear have the potential to produce Myosin 7A positive cells in vitro

Hearing loss and deafness as a result of hair cell loss cannot be restored due to the incapacity of spontaneous regeneration of these cells. Compounds that manipulate key signaling pathways can potentially regenerate cochlear hair cells. In order to test different compounds that promote hair cell regeneration in vitro models can be used. Three-dimensional cultures have allowed the expansion and experimentation of human and mouse inner ear organoids. This is mainly performed in the embryonic or the early postnatal developmental stage. However, since the majority of patients with hearing loss are adult, it is crucial to understand the adult inner ear regenerative capacity. Here, we evaluated progenitor cell markers in the adult human and mouse inner ear and the generation, expansion and differentiation of cochlear organoids derived from the adult human and mouse inner ear. Cochlear and vestibular sensory epithelium from adult humans; and from adult and aged mice express the progenitor markers SOX2 and LGR5; and can generate organoids in vitro. By optimizing the culture conditions, organoids derived from the cochlea and vestibular organ from adult human and adult and aged mouse differentiated to Myosin 7A positive cells. This indicates that the adult inner ear has regenerative capacity. These findings are encouraging for future regenerative therapies to cure hair cell-related hearing loss and deafness.