β-CG prevents loss of spiral ganglion cells.

<p>(A) Representative photomicrographs of spiral ganglion cells in the cochlear basal turns of control (arrow) and βCG-fed mice (white arrow) at 12 months of age (scale bar: 50 μm). Spiral ganglion cells were lost in control mice and preserved in βCG-fed mice. (B) Quantitative analysis revealed that the spiral ganglion cell density was significantly lower in the control than in the βCG-fed mice (<i>n</i> = 4, <i>P</i> < 0.05). (C) Transmission electron microscopy revealed that the numbers of lipofuscin granules in spiral ganglion cells was significantly higher in the control mice (long arrow) than in the βCG-fed mice (scale bar: 5 μm). Moreover, morphological damage such as nuclear invaginations (white arrow) or vacuolation in the myelin sheath (arrowheads) were also observed in control mice but were virtually absent in β-CG-fed WT mice (Fig 5C, right panel).