Fig. 4

The histopathological analysis of GC muscle at 6–24 weeks of age in WT and mdx mice. A Comparison of histogram for muscle fiber CSA reveals an obvious difference of muscle composition between WT (black, n = 5 or 6) and mdx (red, n = 5 or 6) mice. Analyzed muscle fiber frequencies from all animals are plotted for each given muscle fiber CSA with a 100 μm²-bin. B-D The muscle fibers were classified into three types based on thickness (small: < 500 μm², middle: 500–1500 μm², large: > 1500 μm²) and compared between genotypes at each time point. E The averaged muscle fiber CSA calculated from individual animal values are plotted over time. F The fibrosis area quantified as the SR positive area (%) to total muscle area on the GC transverse section are plotted over time. B-F Data are represented as mean + SEM (n = 5 or 6). Statistical comparisons between WT and mdx mice were performed retroactively from the endpoint at 24 weeks of age until no significant difference was detected (Student’s t-test, ^*p < 0.05, ^**p < 0.01, ^***p < 0.001). GC: gastrocnemius, WT: wild-type, CSA: cross-sectional area, SR: Sirius red, SEM: standard error of the mean