Research Paper Advance Articles

Figure 9. Arg-ii expression and cellular localization in aging skeletal muscles. Arg-ii mRNA levels were analyzed by qRT-PCR in skeletal muscles of wild-type (wt) male (A) and female (C) mice. (B, D) arg-i expression in soleus and tibialis from young and old wt and ko mice in both sexes. A parametric unpaired t-test with Welch’s correction was applied. n = 3–9 mice per group. ^*p < 0.05 between the indicated groups. (E) Representative confocal images of old wt and ko skeletal muscle showing co-localization of Arg-II (green) with CD31 (red, endothelial marker), and with Vimentin (red, fibroblasts marker). (F) Representative confocal images of old wt and ko muscle showing lack of co-localization of Arg-II (green) with F4-80 (red, macrophage marker), and with PAX-7 (red, satellite cells marker). DAPI (blue) stains cell nuclei. Scale bar: 10 µm (Arg-II/CD31); 25 µm (Arg-II/Vimentin); 10 µm (Arg-II/F4/80); 20 µm (Arg-II/PAX-7). Each experiment was repeated with 3 animals. (G) Representative confocal images of PAX-7 (red) in skeletal muscle of young and old wt and arg-ii^-/- mice. Scale bar: 25 µm. (H) Quantification of PAX-7⁺ cells (satellite cells) in skeletal muscle expressed as the percentage of PAX-7⁺/total number of cells in the mm² area. One-way ANOVA test was applied. n = 3 mice per group. ^***p < 0.001 between the indicated groups.