Growth and differentiation factor-11 is developmentally regulated in skeletal muscle and inhibits myoblast differentiation

Growth and differentiation factor-11 (GDF-11) is a secreted protein that is closely related to myostatin, a known inhibitor of skeletal muscle development. The role of GDF-11 in regulating skeletal muscle growth remains unclear and the pattern of expression during post-natal growth has not been reported. Therefore, we sought to determine the expression of GDF-11 during post-natal growth and its effect on myoblast proliferation and differentiation. We collected gastrocnemius muscles from male and female mice at 2, 3, 4, 6, 12, 20 and 32 weeks of age (n = 6 per sex and age). In addition, gastrocnemius muscles were collected from male wild-type and myostatin knockout mice at 4, 6, 12 and 20 weeks of age (n = 6 per age and genotype). RNA was extracted and reverse transcribed. Northern analysis identified an expected 4.4 kb mRNA transcript for GDF-11 in gastrocnemius muscles of mice. The concentration of GDF-11 mRNA, as determined by quantitative PCR, was increased in gastrocnemius muscles from 2 to 6 weeks—a period of rapid postnatal muscle growth—and remained higher in male than female mice from 4 to 20 weeks of age (P < 0.05). Interestingly, the mRNA concentration of GDF-11 and its cognate receptors (ActRIIA, ActIIB and Alk5) were increased in gastrocnemius muscles of myostatin knockout compared with wild-type mice (P < 0.05), which may suggest a compensatory mechanism for the lack of myostatin. In support, recombinant GDF-11 inhibited differentiation of C2C12 murine myoblasts and those isolated from myostatin knockout and wild-type mice (P < 0.05). Inhibited differentiation of C2C12 myoblasts was associated with decreased mRNA expression of early and late molecular markers of differentiation (MyoD, myogenin, IGF-II, desmin and MyHC, P < 0.05). Our results suggest that GDF-11 regulates growth of skeletal muscles by inhibiting myoblast differentiation in an autocrine/paracrine manner and, perhaps, also plays a role in regulating sexually dimorphic growth.