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. 2023 Dec 2;27(1):108632. doi: 10.1016/j.isci.2023.108632

Figure 2.

Figure 2

Free wheel running reduces skeletal muscle fibrosis in FLExDUX4 male mice and alters fiber type composition

(A) Sample images of Masson’s trichrome staining in the triceps brachii from all groups. Blue staining indicates presence of fibrous connective tissue. Scale bar: 100 μm.

(B) Percentage (of total area) of triceps brachii fibrosis in each group. “∗” denotes FLExDUX4 male control > WT control male and female mice, WT male Ex mice, and FLExDUX4 male and female Ex mice (∗ p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001) (n = 44, n = 6 WT M Con, n = 6 WT M Ex, n = 5 WT F Con, n = 6 WT F Ex, n = 6 FLExDUX4 M Con, n = 5 FLExDUX4 M Ex, n = 5 FLExDUX4 F Con, n = 5 FLExDUX4 F Ex, three-way ANOVA).

(C) Sample immunofluorescence (laminin = green, nuclei = blue) images of myofibers from the triceps brachii of all groups. Scale bar: 100 μm.

(D and E) Distribution of fibers according to minimal feret diameter (um) in all male mice (D) and female mice (E) from all groups (n = 50, n = 5 WT M Con, n = 7 WT M Ex, n = 6 WT F Con, n = 6 WT F Ex, n = 8 FLExDUX4 M Con, n = 6 FLExDUX4 M Ex, n = 4 FLExDUX4 F Con, n = 7 FLExDUX4 F Ex, three-way ANOVA).

(F) Average minimal feret diameter for male and female, control and exercise groups (three-way ANOVA). “∗” denotes mean diameter is lower in trained vs. control mice across groups (main effect of training status, p < 0.01). “‡” denotes female diameter < male diameter across groups (main effect of sex, p < 0.01). Mean ± SEM are plotted for all charts.

(G) Immunofluorescence staining of skeletal muscle fiber types in the triceps brachii using antibodies targeting MyHC-I (blue), MyHC-IIa (green), MyHC-IIx (red), and MyHC-IIb (unstained). Representative images are presented for each study group. Scale bar: 50 μm.

(H) Quantification of the proportion of each fiber type in each study group (n = 32 mice, 4 per group, mean of 4396 ± 1048 fibers per section, three-way ANOVA). “∗” denotes significantly different than corresponding male untrained control. “§” denotes female mice have significantly greater proportions of type IIb fibers (p < 0.05). “#” denotes main effect of training status, with trained mice demonstrating a significant reduction in type IIb fibers vs. untrained mice (p < 0.05). “Δ” denotes training × genotype interaction (p < 0.05). WT mice show a significant decline in type IIx fibers with training, whereas FLExDUX4 mice show an increase in type IIx fibers with training (p < 0.05).