Duchenne muscular dystrophy, an X-linked recessive neuromuscular disorder due to lack of the protein dystrophin, manifests as progressive muscle degeneration and cardiomyopathy with increased fibrosis. The exact mechanisms involved in fibrosis are unknown, but a cytokine, transforming growth factor-beta (TGF-beta), is a likely mediator. This study tested whether the TGF-beta antagonist, pirfenidone, could reduce cardiac fibrosis. Eight-month-old mdx mice were treated for 7 months with 0.4%, 0.8%, and 1.2% pirfenidone in drinking water; untreated water was given to control mdx and C57 mice. Mice treated with 0.8% and 1.2% pirfendone had lowered cardiac TGF-beta mRNA and improved in vitro cardiac contractility (P < 0.05) to levels consistent with C57 mice, yet without a change in cardiac stiffness or fibrosis. These results show that the TGF-beta antagonist, pirfenidone, can improve cardiac function in mdx mice, potentially providing a new avenue for developing cardiac therapies for patients with Duchenne muscular dystrophy.

The mdx mouse model of muscular dystrophy has a premature stop codon preventing production of dystrophin. This results in a progressive phenotype causing centronucleation of skeletal muscle fibers, muscle weakness, and fibrosis and kyphosis. Antisense oligonucleotides alter RNA splicing to exclude the nonsense mutation, while still maintaining the open reading frame to produce a shorter, but partially functional dystrophin protein that should ameliorate the extent of pathology. The present study investigated the benefits of chronic treatment of mdx mice by once-monthly deep intramuscular injections of antisense oligonucleotides into paraspinal muscles. After 8 mo of treatment, mdx mice had reduced development of kyphosis relative to untreated mdx mice, a benefit that was retained until completion of the study at 18 mo of age (16 mo of treatment). This was accompanied by reduced centronucleation in the latissimus dorsi and intercostals muscles and reduced fibrosis in the diaphragm and latissimus dorsi. These benefits were accompanied by a significant increase in dystrophin production. In conclusion, chronic antisense oligonucleotide treatment provides clear and ongoing benefits to paralumbar skeletal muscle, with associated marked reduction in kyphosis.