Figure 1

Recombinant IL-15 stimulation of differentiating primary human myoblasts enhances myotube formation and promotes myogenic gene expression. Subconfluent myoblasts were switched to differentiation medium containing the indicated concentrations of IL-15 for 8 d. Media were renewed every 2 d. Myotubes were fixed, immunofluorescence stained for desmin and with DAPI and imaged on an epifluorescence microscope. (a) Representative images at 20x magnification. (b) Myotube thickness data represents the mean ± SEM of 450 total measurements taken at 63x magnification from 90 myotubes per treatment condition (n = 3 biological replicates). **p < 0.01 vs. unstimulated (0 ng/mL) condition by Mann-Whitney U test with post-hoc Holm’s sequential Bonferroni adjustment. (c) Nuclear fusion index data is expressed as mean ± SEM values from 45 images taken at 20x magnification from 3 biological replicates. ***p < 0.001 vs. unstimulated (0 ng/mL) condition by one-way ANOVA with post-hoc Bonferroni correction. (d) Number of myonuclei per myotube is expressed as mean ± SEM values from 15 images taken at 20x magnification from 3 biological replicates. (e) Primary human myoblasts were stimulated with recombinant IL-15 at the indicated concentrations for 8 days. Media were renewed every 2 d. ***p < 0.001 vs.unstimulated condition by one-way ANOVA with post-hoc Bonferroni correction. (f,g) Subconfluent myoblasts were switched to differentiation medium containing the indicated concentrations of IL-15 for 8 d. Media were renewed every 2 d *p < 0.05, ***p < 0.001 vs. unstimulated condition by Mann-Whitney U test with post-hoc Holm’s sequential Bonferroni adjustment. Data expressed as mean ± SEM. 3 technical replicates (each assayed in triplicate) per biological replicate, 3 biological replicates