Effects of maternal immunisation against myostatin on post-natal growth and skeletal muscle mass of offspring in mice

Maternal immunization against myostatin suppresses post-hatch chicken growth

Myostatin (MSTN) is a negative regulator of skeletal muscle growth, thus it was hypothesized that immunization of hens against MSTN would enhance post-hatch growth and muscle mass via suppression of MSTN activity by anti-MSTN IgY in fertilized eggs. This study investigated the effects of immunization of hens against chicken MSTN (chMSTN) or a MSTN fragment (Myo2) on the growth and muscle mass of offspring. In Experiment 1, hens mixed with roosters were divided into two groups and hens in the Control and chMSTN groups were immunized with 0 and 0.5 mg of chMSTN, respectively. In Experiment 2, hens in the chMSTN group were divided into chMSTN and Myo2 groups while the Control group remained the same. The Control and chMSTN groups were immunized in the same way as Experiment 1. The Myo2 group was immunized against MSTN peptide fragment (Myo2) conjugated to KLH. Eggs collected from each group were incubated, and chicks were reared to examine growth and carcass parameters. ELISA showed the production of IgYs against chMSTN and Myo2 and the presence of these antibodies in egg yolk. IgY from the chMSTN and Myo2 groups showed binding affinity to chMSTN, Myo2, and commercial MSTN in Western blot analysis but did not show MSTN-inhibitory capacity in a reporter gene assay. In Experiment 1, no difference was observed in the body weight and carcass parameters of offspring between the Control and chMSTN groups. In Experiment 2, the body weight of chicks from the Myo2 group was significantly lower than that of the Control or chMSTN groups. The dressing percentage and breast muscle mass of the chMSTN and Myo2 groups were significantly lower than those of the Control group, and the breast muscle mass of Myo2 was significantly lower than that of the chMSTN. In summary, in contrast to our hypothesis, maternal immunization of hens did not increase but decreased the body weight and muscle mass of offspring.

Administration of a mutated myostatin propeptide to neonatal mice significantly enhances skeletal muscle growth

Myostatin is a dominant inhibitor of skeletal muscle development and growth. As transgenic over-expression of myostatin propeptide dramatically enhanced muscle mass, we hypothesized that administration of myostatin propeptide will increase muscle growth. In this study, the wild-type form of porcine myostatin propeptide and its mutated form at the cleavage site of metalloproteinases of BMP-1/TLD family were produced from insect cells. In vitro A204 cells reporter assays showed that both wild-type and the mutated propeptides depressed myostatin activity. The recombinant propeptides at four-fold myostatin concentration can effectively block myostatin function during co-incubation with A204 cells. In particular, the mutated propeptide appeared much more effective than wild-type propeptide over a long period during the in vitro co-incubation. Administration of the mutated propeptide to neonatal mice at the age of 11 and 18 days was tested and showed significant increase in growth performance by 11-15% from the age of 25 to 57 days (P < 0.05). The major skeletal muscles of mice that were injected with mutated propeptide were 13.5-24.8% heavier than the control group (P < 0.05) as a result of muscle fiber hypertrophy. In conclusion, administration of the mutated myostatin propeptide during the neonatal period is an effective way for promoting muscle growth.