Figure 3

Extensive myofiber branching occurs in regenerating wild-type muscles, regardless of the injury method used. (A) No significant differences occurred in the percentage of regenerated myofibers at 3 or 16 weeks after injury induced by either cardiotoxin (C or CTX) or barium chloride (B or BaCl₂) in adult wild-type gastrocnemius muscles. (B) The percentage of branched, regenerated myofibers was similar, regardless of the method used to induce injury, and did not change significantly with time after injury. (C) Injury did not significantly increase myofiber branching in nonregenerated myofibers. UN, Uninjured muscles. (D) The majority of branched, regenerated myofibers contained one branch. The number of branches per regenerated myofiber significantly differed between the two myotoxins at 3 weeks (χ² = 10.4, df = 3), but not at 16 weeks, after injury (χ² = 4.6, df = 3). The average number of branches per regenerated myofiber varied between 1.4 and 2 for all injuries and time points (CTX at 3 weeks = 2.0 ± 0.2, CTX at 16 weeks = 1.5 ± 0.1, BaCl₂ at 3 weeks = 1.5 ± 0.1 and BaCl₂ at 16 weeks = 1.4 ± 0.1). (E) Quantification of branching types at 3 and 16 weeks after injury (n = 252 to 645 myofibers isolated per injury method and time point). Data are mean ± SEM, with three to six injured mice and nine uninjured mice. *P < 0.05.