Prevention of exercised induced cardiomyopathy following Pip-PMO treatment in dystrophic mdx mice.

Corinne A Betts,Carolyn A Carr,Thomas C Roberts,Amer F Saleh,Michael J Gait,Caroline Godfrey,Anna M L Coenen-Stass,Suzan M Hammond,Miguel A Varela,Graham Mcclorey,Kieran Clarke,Matthew J A Wood

doi:10.1038/srep08986

Abstract

Duchenne muscular dystrophy (DMD) is a fatal neuromuscular disorder caused by mutations in the Dmd gene. In addition to skeletal muscle wasting, DMD patients develop cardiomyopathy, which significantly contributes to mortality. Antisense oligonucleotides (AOs) are a promising DMD therapy, restoring functional dystrophin protein by exon skipping. However, a major limitation with current AOs is the absence of dystrophin correction in heart. Pip peptide-AOs demonstrate high activity in cardiac muscle. To determine their therapeutic value, dystrophic mdx mice were subject to forced exercise to model the DMD cardiac phenotype. Repeated peptide-AO treatments resulted in high levels of cardiac dystrophin protein, which prevented the exercised induced progression of cardiomyopathy, normalising heart size as well as stabilising other cardiac parameters. Treated mice also exhibited significantly reduced cardiac fibrosis and improved sarcolemmal integrity. This work demonstrates that high levels of cardiac dystrophin restored by Pip peptide-AOs prevents further deterioration of cardiomyopathy and pathology following exercise in dystrophic DMD mice.

Highlights

Duchenne muscular dystrophy (DMD) is a fatal neuromuscular disorder caused by mutations in the Dmd gene
The widely used dystrophic mdx mouse model has a natural mutation in exon 23 of the Dmd gene which generates a premature termination codon
Immunohistochemical staining of the treated mdx hearts revealed widespread and homogenously distributed dystrophin protein restoration (Fig. 1C). This is indicated by the higher magnification inserts showing right ventricle (RV) wall (Fig. 1 C, i), outer left ventricle (LV) wall from apex (Fig. 1 C, ii) to base (Fig. 1 C iv and v) and inner myocardial dystrophin protein restoration (Fig. 1 C, iii)

Summary

Introduction

Duchenne muscular dystrophy (DMD) is a fatal neuromuscular disorder caused by mutations in the Dmd gene. This work demonstrates that high levels of cardiac dystrophin restored by Pip peptide-AOs prevents further deterioration of cardiomyopathy and pathology following exercise in dystrophic DMD mice. Previous studies www.nature.com/scientificreports showed that the hydrophobic region is critical for the delivery to the heart tissue as other arginine-rich peptides with a shorter hydrophobic region failed to achieve this Progressive evolution of this peptide series through structure-activity studies has identified novel peptides with dramatically enhanced cardiac dystrophin restoration[30,31,32]. We sought to determine the benefit on cardiac function and pathology offered by Pip6-PMO conjugates which restore high levels of dystrophin in heart To do this we modelled the treatment of DMD cardiomyopathy by repeat treating dystrophic mdx mice in which a moderate cardiomyopathy was induced by forced exercise over a twelve week period. Our results demonstrate that restoring high levels of dystrophin in heart with Pip6-PMO was sufficient to prevent exercise-induced progression of cardiomyopathy and to improve multiple indices of cardiac pathology

Methods

Results

Conclusion