The TA and DIA muscles were sectioned at 8 μm using a CryoStar NX70 cryostat (Thermo Fisher) and stained with H&E or Sirius red. IgG staining was performed to detect degenerating fibers as previously described (54 (link)). In brief, the cryosections were preincubated with 5% BSA in PBS for 1 h, followed by incubation with Alexa 488-conjugated goat anti-mouse IgG antibody (A-11029, Invitrogen, Carlsbad, CA). Fluorescence images were obtained using a BZ-X810 fluorescence microscope (Keyence).