ABSTRACT
This study evaluated the effect of muscle satellite cells (MSCs) overexpressing myogenin (MyoG) on denervated muscle atrophy. Rat MSCs were isolated and transfected with the MyoG-EGFP plasmid vector GV143. MyoG-transfected MSCs (MTMs) were transplanted into rat gastrocnemius muscles at 1 week after surgical denervation. Controls included injections of untransfected MSCs or the vehicle only. Muscles were harvested and analyzed at 2, 4, and 24 weeks post-transplantation. Immunofluorescence confirmed MyoG overexpression in MTMs. The muscle wet weight ratio was significantly reduced at 2 weeks after MTM injection (67.17±6.79) compared with muscles injected with MSCs (58.83±5.31) or the vehicle (53.00±7.67; t=2.37, P=0.04 and t=3.39, P=0.007, respectively). The muscle fiber cross-sectional area was also larger at 2 weeks after MTM injection (2.63×103±0.39×103) compared with MSC injection (1.99×103±0.58×103) or the vehicle only (1.57×103±0.47×103; t=2.24, P=0.049 and t=4.22, P=0.002, respectively). At 4 and 24 weeks post-injection, the muscle mass and fiber cross-sectional area were similar across all three experimental groups. Immunohistochemistry showed that the MTM group had larger MyoG-positive fibers. The MTM group (3.18±1.13) also had higher expression of MyoG mRNA than other groups (1.41±0.65 and 1.03±0.19) at 2 weeks after injection (t=2.72, P=0.04). Transplanted MTMs delayed short-term atrophy of denervated muscles. This approach can be optimized as a novel stand-alone therapy or as a bridge to surgical re-innervation of damaged muscles.
Subject(s)
Animals , Male , Muscular Atrophy/rehabilitation , Myogenin/metabolism , Cell Transplantation , Muscle, Skeletal/innervation , Satellite Cells, Skeletal Muscle/transplantation , Muscle Denervation/rehabilitation , Organ Size/genetics , Plasmids , Muscular Atrophy/etiology , Transfection , Gene Expression , Fluorescent Antibody Technique , Rats, Sprague-Dawley , Myogenin/genetics , Satellite Cells, Skeletal Muscle/cytology , Real-Time Polymerase Chain ReactionABSTRACT
Estudou-se a filogenia do gene da miogenina, um membro da família MyoD, reguladora da miogênese, que ocorre durante o desenvolvimento embrionário, e sua história evolutiva em espécies domésticas que apresentem seqüências de DNA depositadas no Genbank, comparando-se o índice de substituição de nucleotídeos não-sinônimos pelo índice de substituição sinônima. Valores maiores do que um (1) indicaram que o gene sofreu mudanças que tornaram o organismo mais adaptado ao ambiente. As árvores filogenéticas foram obtidas por máxima verossimilhança, e os índices de substituição sinônima e não-sinônima foram analisadas pelo método de parcimônia. Os resultados indicaram que, provavelmente, o gene sofreu evolução adaptativa no grupo Ruminantia, Bos taurus e Ovis aries, depois que essas espécies divergiram do ancestral comum. Para as outras espécies analisadas, o gene parece ter evoluído de modo conservativo.
The myogenin gene, a member of the MyoD gene family, is a regulator of the myogenesis that takes place during the embryonic development. The objective of this study was to perform a phylogenic analysis of the myogenin gene to study its evolutionary history in the domestic species that have the sequencing data deposited in the Genbank. One common method to detect a gene evolution is made by comparing the ratio of nonsynonymous nucleotide substitution by the ratio of synonymous substitutions. Values greater than one (1) means that the gene has gone through changes that made the organism more adapted to the environment. The phylogenetic trees were obtained by maximum likelihood and the synonymous and nonsynonymous substitution rates were analyzed by the parsimony method. The results point out that probably the gene suffered an adaptive evolution in the Ruminantia group, Bos Taurus and Ovis aries, after these species diverged from their common ancestral. In the other species, the gene seems to be evolved in a conservative way.