Fig. 1

Longitudinal MRI/MRS measurements of muscle T2, leg muscle size, and muscle fat fraction in WT and mdx mice. A T2 maps from one WT mouse (left) and one mdx mouse (right) at 6–18 weeks of age. Areas with high T2 values were consistently observed in both legs of the mdx mice at all ages. Green arrows indicate that the region with a high T2 becomes normal at a later time point, whereas yellow arrows indicate that the initially normal T2 region has a high T2 at a later time point. The yellow circle in the bottom-left image shows the ROI definition for the T2 analysis in each slice. A: anterior, M: medial. B-E Time course of muscle T2 (B), muscle fat fraction (C), leg muscle size (D), and body weight (E) in WT (black circle, n = 8) and mdx (red square, n = 8) mice. Data are represented as mean ± SEM. Statistical comparisons between WT and mdx mice were performed retroactively from the endpoint at 18 weeks of age until no significant differences were observed (Student’s t-test, ^*p < 0.05, ^**p < 0.01, ^***p < 0.001). MRI: magnetic resonance imaging, MRS: magnetic resonance spectroscopy, T2: the transverse relaxation time constant, WT: wild-type, ROI: regions of interest