Fig. 2

Histopathology of age-related myopathy in dKO mice. a Representative X-ray analysis of 1-year control and dKO mice. Spines of dKO mice show abnormal rounding (kyphosis). b H&E-stained sections of representative muscle groups from control and dKO animals. Muscles from dKO animals display indicators of disease: central nuclei (open arrow), inflammation (open arrowhead), necrosis (closed arrowhead), hypertrophy (asterisk), and atrophy (closed arrow). c Detection of endomysial fibrosis in control and dKO quadriceps muscles by Masson’s trichrome stain (blue) and Sirius Red stain (red) as indicated. The histogram quantifies the Sirius Red-positive area from control and dKO sections. n = 3 mice per genotype, with each point representing the average Sirius Red-positive area of five randomly selected sections per mouse. Values are means ± SD, *p < 0.05. d Stains for mitochondrial histology as indicated. Gomori trichrome stain for mitochondria (purple) and nuclei (black). Qualitative analysis of complex I enzymatic activity and fiber type distribution by NADH-tetrazolium reductase stain; type I fibers (dark blue) and type II fibers (light blue). Cytochrome oxidase stain for complex IV activity and fiber type distribution; type I fibers (dark brown) and type II fibers (light brown). Arrows indicate focal depletion of mitochondria in dKO myofibers