Fig. 1

The skeletal muscle fibrotic area was increased in aged mice, while the SC numbers and sympathetic nerve activity were decreased. A–C SR staining showed that the proportion of the fibrotic area was increased and that the proportion of the myocyte area was decreased in the aged mice (n = 8) (t = 4.89 and 3.77, P < 0.001 and 0.021). D, E Immunofluorescence staining showed that the number of PAX7⁺ nuclei (SCs, red arrow) was decreased significantly in aged mice (n = 8) (t = 5.97, P < 0.001). F, G Immunofluorescence staining showed that the levels of TH and NPY in the sympathetic nerves of the aged mice were significantly lower than those of the young mice (n = 8) (t = 1.54 and 2.07, P = 0.017 and 0.008). H–K Both the intensity of TH and the number of PAX7⁺ nuclei (SCs, white arrow) were decreased significantly in aged mice compared with young mice (n = 8 per group) (t = 2.28 and 2.40, P = 0.039 and 0.031), and the intensity of TH correlated with the number of PAX7⁺ nuclei (r = 0.789, P < 0.001). Independent samples t tests, *P < 0.05; **P < 0.001