which carry a mutation in the dystrophin 
gene and therefore serve as a genetic model of Duchenne’s muscular dystrophy. For example, mdx mice lacking myostatin were found not only to be stronger and more muscular than their mdx counterparts with normal myostatin, but also to have reduced fibrosis and fat deposition, suggesting sustained muscle regeneration. Furthermore, injection of neutralizing monoclonal antibodies directed against myostatin into either wildtype or mdx mice increases muscle mass and specific force, suggesting that myostatin plays an important role in regulating muscle growth in adult animals. Astragalus polysaccharide Magic-F1 is a molecule with a potential clinical application as it can induce muscle hypertrophy by both down-regulating myostatin and directly activating MyoD, Myf5 and several anti-apoptotic pathways. Interestingly, no side effects have been observed in skeletal muscles following electroenhanced Magic-F1 DNA transfer or in transgenic mice expressing the Magic-F1 under the control of a muscle-specific promoter. Our data showing the inability of Magic-F1 to induce the ERK pathway together with an inhibitory interference with HGFinduced ERK activation are particular relevant to a potential therapeutic use of this engineered factor. In fact, several tissues other than myocytes and satellite cells express the Met receptor, including epithelial cells of kidney, liver, lung, skin, breast and the whole gastrointestinal tract, as well as neurons, endothelial cells and hematopoietic precursors. Furthermore, Met overexpression is a very frequent event in human cancer. This raises the concern that stimulating the proliferation of Met-expressing cells may lead to tumor formation or progression. In this regard, the lack of any mitogenic activity makes Magic-F1 a potentially safe cytokine for cell therapy. Because of its potent and selective effect on myoblast survival and differentiation, Magic-F1 promoted muscular hypertrophy in all mouse models analyzed. This biological activity, revealed by in vitro experiments, was extensively confirmed by the analysis of muscles treated by electro-enhanced DNA transfer or derived from transgenic mice 21927650 expressing Magic-F1 under the control of a muscle-specific promoter. Interestingly, a statistically significant increase of myofiber cross-sectional areas was observed in the tibialis anterior muscles but not in slow-twitch soleus muscles. This can be attributed to the specificity of the promoter, active in fast Magic-F1 partially rescues the dystrophic phenotype of alpha-sarcoglycan knock-out mice The therapeutic potential of Magic-F1 was tested in alphasarcoglycan knock-out mice, which represent an established animal model of muscular dystrophy. Due to their genetic defect, these mice display persistent degeneration and regeneration areas in skeletal muscles. To achieve Magic-F1 expression in these mice, we undertook two different approaches. Firstly, we crossed Magic-F1 transgenic mice with a-SG knock-out animals, thus generating a-SG knock-out mice expressing Magic-F1 in their muscles. Secondly, we engineered an adenoviral vector expressing Magic-F1 and administered it by intramuscular injection to 45 dayold a-SG knock-out female mice under immunosuppressive conditions. Morphological analysis of the 12484537 tibialis anterior of aSG knock-out/Magic-F1 transgenic mice revealed significant muscular hypertrophy compared to a-SG knock-out controls, which persisted until at least 6 months of age. Consisted with this,
