Figure 1.

Panel (A) provides an overview of a 70-year-old human comparable to a 2-year-old mouse. The age group in humans displays profound hearing decay, shown as percent (%) of hearing loss (A, in red) follow-on hearing loss of 90-year-old humans. Limited restoration is attempted that has focused on 2-year or mostly younger mice, that is driven by the cost of keeping animals to old age and is providing a lack of decent models. Audiograms (B) and histology (C,D) demonstrated the loss of IHC (C), OHC (D), and the progressive threshold reduction in older people shown with the audiogram (B). Note that people exposed to noise have an additional loss in hair cells (C,D) and show a threshold reduction in the audiogram (B) in the middle age of 50–74 years old. In newborn mice, we demonstrate the phenotype of Atoh1 LacZ in control mice (E) Atoh1LacZ/LacZ null mice (F) is comparable (i.e., a single row of undifferentiated IHCs). Compared to Neurog1 null mice, a shorter cochlea has outliers in the GER area (G). Data were taken from the Jackson lab, WHF, and Fritzsch et al. (2005); Matei et al. (2005); Sheffield and Smith (2019); and Wu et al. (2021). Scale bars: 100 μm (E–G).