Figure 2

Myofiber branching increases with age in mdx mice. The percentage of regenerated myofibers (A) and branched myofibers (B) in gastrocnemius muscles from mdx mice rapidly increased between 3.5 and 9.5 weeks of age. (C) More than 80% of the regenerated myofibers were branched. (D) The number of branches per regenerated myofiber significantly increased with age in gastrocnemius muscles of mdx mice (χ² = 82.7, df = 3). (E) Phase-contrast image of a branched myofiber from a 16-week-old mdx mouse. Bar = 250 μm. (F) Phase-contrast images of the three branching types studied. Bar = 100 μm. (G) Quantification of branching types in mdx mice at different ages. In (A), (C), (D) and (G), 73 to 287 myofibers were analyzed per age, where 15.5 and 30.5 weeks are the averages of 15- and 16-week-old and 30- and 31-week-old mice, respectively. In (B), each point represents one mouse with 16 to 103 myofibers. The dashed line represents the best fit curve for the percentage of branched myofibers with time. In (A), (C) and (G), data are mean ± SEM (n = 3 or 4 mice for all ages, except n = 2 for 9.5-week-old mice). *P < 0.05.