Celloidin embedding and hematoxylin-eosin staining (CE-HE)
After fixation with 4% paraformaldehyde, the wild-type and mutant cochleae were washed in 1% phosphate-buffered saline (PBS) and decalcified in 10% EDTA for approximately 1 month. Following dehydration with graded ethanol and embedding with celloidin, the cochleae were sectioned into 15 μm slices using a frozen microtome CM1900 (Leica, Germany) and stained with hematoxylin-eosin (HE). Finally, the sections were visualized under a Leica DMI3000 microscope (Leica, Germany).