Reduced myogenic differentiation capacity of satellite cell-derived myoblasts in male ICR mice compared with male C57BL/6 and BALB/c mice.

Many strains of wild-type laboratory mice have been developed for studies in the life sciences, including skeletal muscle cell biology. Muscle regeneration capacity differs among wild-type mouse strains. However, few studies have focused on whether myogenic stem cells (satellite cells) are directly related to mouse strain-dependent myoregeneration gaps using in vitro culture models. In this study, we selected three major wild-type mouse strains, CD1 (outbred; Jcl:ICR [ICR]), C57BL/6NJcl (inbred; B6), and BALB/cAJcl (inbred; C), which are widely used in laboratory experiments. Initially, we compared myotube fusion capabilities using satellite cell-derived myoblasts. The results showed that cell cultures isolated from male ICR mice could not efficiently form myotubes owing to low expression levels of myogenic regulatory factors (e.g., MyoD, myogenin, myocyte enhancer factor [MEF] 2A, and MEF2C) compared with B6 and C mouse strains. Next, we compared the myofiber-type compositions of muscle tissues and cultured myotubes among male mice from each of the three strains. Although each muscle tissue used for satellite cell isolation similarly expressed fast-twitch myofiber markers in all mouse strains, male ICR-derived myoblasts formed abundant amounts of slow-type myotubes. By contrast, myotubes from male B6 and C mice expressed substantial levels of fast-twitch myofiber markers. We also performed a comparative experiment in female ICR, B6, and C mouse strains, similar to the male mouse experiments. The myogenic differentiation potencies of myoblasts and myofiber-type compositions of myotubes in female mouse strains were similar. Thus, male ICR-derived satellite cells (myoblasts) had low myogenic differentiation potential, which may be associated with the tendency slow-twitch myotube formation.