Figure 2.

An hFL-OPG-Fc treatment significantly improved muscle integrity and fiber cross-sectional area (CSA) following cardiotoxin-induced muscle injury

(A) Images of hematoxylin and eosin (H&E)-stained Sol muscle sections from C57BL/10J mice injected with 15 μL of CTX (20 μM) followed by daily injections of either PBS or hFL-OPG-Fc (1 mg/kg/day) for 3 (n = 3–5) and 7 days (n = 6). The area occupied by myofibers was estimated using ImageJ 1.52a. (A and B) Three days after the CTX injection, the hFL-OPG-Fc-treated mice had slightly more myofibers than the PBS-treated mice (33% versus 20% of surface area occupied by myofibers, respectively). Seven days following CTX injection-induced injury, the area occupied by myofibers was significantly higher in Sol muscles from the hFL-OPG-Fc-treated mice than the PBS-treated mice. (C) Data are expressed as the percentage of myofiber area with respect to the total area. The myofiber CSA of Sol muscles at day 7 after the CTX injection was significantly higher in hFL-OPG-Fc-treated mice compared to PBS-treated mice. (D) The variance coefficient of the muscle fiber CSA determined using the minimal Feret’s diameter method showed no difference in muscle fiber heterogenicity between hFL-OPG-Fc-treated and PBS-treated mice at day 7 post-CTX-induced injury. Complementary images of H&E staining of both hFL-OPG-Fc- and PBS-treated mice at 7 days post-CTX-induced injury are presented in Figures S2 and S3, respectively. Blue arrows indicate mature and regenerating myofibers. Black arrows and the hashtag, which indicate degenerating/necrotic myofibers and empty spaces, respectively, were excluded from quantification. Scale bars represent 100 μm. Data are expressed as means ± SEM. ∗p < 0.05 indicates significantly different from PBS-treated mice using the Student’s t test (n = 3–6); ∗∗p < 0.01 indicates statistical differences between day 3 and day 7 for the respective treatment groups.