Dose-dependent restoration of dystrophin expression in cardiac muscle of dystrophic mice by systemically delivered morpholino.
ABSTRACT We have earlier shown that antisense morpholino oligomers are able to restore dystrophin expression by systemic delivery in body-wide skeletal muscles of dystrophic mdx mice. However, the levels of dystrophin expression vary considerably and, more importantly, no dystrophin expression has been achieved in cardiac muscle. In this study, we investigate the efficiency of morpholino-induced exon skipping in cardiomyoblasts and myocytes in vitro, and in cardiac muscle in vivo by dose escalation. We showed that morpholino induces targeted exon skipping equally effectively in both skeletal muscle myoblasts and cardiomyoblasts. Effective exon skipping was achieved in cardiomyocytes in culture. In the mdx mice, morpholino rescues dystrophin expression dose dependently in both skeletal and cardiac muscles. Therapeutic levels of dystrophin were achieved in cardiac muscle albeit at higher doses than in skeletal muscles. Up to 50 and 30% normal levels of dystrophin were induced by single systemic delivery of 3 g kg(-1) of morpholino in skeletal and cardiac muscles, respectively. High doses of morpholino treatment reduced the serum levels of creatine kinase without clear toxicity. These findings suggest that effective rescue of dystrophin in cardiac muscles can be achieved by morpholino for the treatment of Duchenne muscular dystrophy.
- SourceAvailable from: Akinori Nakamura
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ABSTRACT: Antisense therapy with both chemistries of phosphorodiamidate morpholino oligomers (PMOs) and 2'-O-methyl phosphorothioate has demonstrated the capability to induce dystrophin expression in Duchenne muscular dystrophy (DMD) patients in phase II-III clinical trials with benefit in muscle functions. However, potential of the therapy for DMD at different stages of the disease progression is not understood. In this study, we examined the effect of peptide-conjugated PMO (PPMO)-mediated exon skipping on disease progression of utrophin-dystrophin-deficient mice (dko) of four age groups (21-29, 30-39, 40-49 and 50+ days), representing diseases from early stage to advanced stage with severe kyphosis. Biweekly intravenous (i.v.) administration of the PPMO restored the dystrophin expression in nearly 100% skeletal muscle fibers in all age groups. This was associated with the restoration of dystrophin-associated proteins including functional glycosylated dystroglycan and neuronal nitric synthase. However, therapeutic outcomes clearly depended on severity of the disease at the time the treatment started. The PPMO treatment alleviated the disease pathology and significantly prolonged the life span of the mice receiving treatment at younger age with mild phenotype. However, restoration of high levels of dystrophin expression failed to prevent disease progression to the mice receiving treatment when disease was already at advanced stage. The results could be critical for design of clinical trials with antisense therapy to DMD.Gene Therapy advance online publication, 19 June 2014; doi:10.1038/gt.2014.53.Gene Therapy 06/2014; · 4.20 Impact Factor
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ABSTRACT: Antisense-mediated exon skipping, which can restore the reading frame, is a most promising therapeutic approach for Duchenne muscular dystrophy. Remaining challenges include the limited applicability to patients and unclear function of truncated dystrophin proteins. Multiexon skipping targeting exons 45-55 at the mutation hotspot of the dystrophin gene could overcome both of these challenges. Previously, we described the feasibility of exons 45-55 skipping with a cocktail of Vivo-Morpholinos in vivo; however, the long-term efficacy and safety of Vivo-Morpholinos remains to be determined. In this study, we examined the efficacy and toxicity of exons 45-55 skipping by intravenous injections of 6 mg/kg 10-Vivo-Morpholino cocktail (0.6 mg/kg each vPMO) every 2 weeks for 18 weeks to dystrophic exon-52 knockout (mdx52) mice. Systemic skipping of the entire exons 45-55 region was induced, and the Western blot analysis exhibited the restoration of 5-27% of normal levels of dystrophin protein in skeletal muscles, accompanied by improvements in histopathology and muscle strength. No obvious immune response and renal and hepatic toxicity were detected at the end-point of the treatment. We demonstrate our new regimen with the 10-Vivo-Morpholino cocktail is effective and safe for long-term repeated systemic administration in the dystrophic mouse model.Mol Ther Nucleic Acids; 02/2015