Oral corticosteroids and onset of cardiomyopathy in Duchenne muscular dystrophy

New developments in exon skipping and splice modulation therapies for neuromuscular diseases

INTRODUCTION

Antisense oligonucleotide (AON) therapy is a form of treatment for genetic or infectious diseases using small, synthetic DNA-like molecules called AONs. Recent advances in the development of AONs that show improved stability and increased sequence specificity have led to clinical trials for several neuromuscular diseases. Impressive preclinical and clinical data are published regarding the usage of AONs in exon-skipping and splice modulation strategies to increase dystrophin production in Duchenne muscular dystrophy (DMD) and survival of motor neuron (SMN) production in spinal muscular atrophy (SMA).

AREAS COVERED

In this review, we focus on the current progress and challenges of exon-skipping and splice modulation therapies. In addition, we discuss the recent failure of the Phase III clinical trials of exon 51 skipping (drisapersen) for DMD.

EXPERT OPINION

The main approach of AON therapy in DMD and SMA is to rescue ('knock up' or increase) target proteins through exon skipping or exon inclusion; conversely, most conventional antisense drugs are designed to knock down (inhibit) the target. Encouraging preclinical data using this 'knock up' approach are also reported to rescue dysferlinopathies, including limb-girdle muscular dystrophy type 2B, Miyoshi myopathy, distal myopathy with anterior tibial onset and Fukuyama congenital muscular dystrophy.

Superpulsed low-level laser therapy protects skeletal muscle of mdx mice against damage, inflammation and morphological changes delaying dystrophy progression

AIM

To evaluate the effects of preventive treatment with low-level laser therapy (LLLT) on progression of dystrophy in mdx mice.

METHODS

Ten animals were randomly divided into 2 experimental groups treated with superpulsed LLLT (904 nm, 15 mW, 700 Hz, 1 J) or placebo-LLLT at one point overlying the tibialis anterior muscle (bilaterally) 5 times per week for 14 weeks (from 6th to 20th week of age). Morphological changes, creatine kinase (CK) activity and mRNA gene expression were assessed in animals at 20th week of age.

RESULTS

Animals treated with LLLT showed very few morphological changes in skeletal muscle, with less atrophy and fibrosis than animals treated with placebo-LLLT. CK was significantly lower (p=0.0203) in animals treated with LLLT (864.70 U.l-1, SEM 226.10) than placebo (1708.00 U.l-1, SEM 184.60). mRNA gene expression of inflammatory markers was significantly decreased by treatment with LLLT (p<0.05): TNF-α (placebo-control=0.51 µg/µl [SEM 0.12], - LLLT=0.048 µg/µl [SEM 0.01]), IL-1β (placebo-control=2.292 µg/µl [SEM 0.74], - LLLT=0.12 µg/µl [SEM 0.03]), IL-6 (placebo-control=3.946 µg/µl [SEM 0.98], - LLLT=0.854 µg/µl [SEM 0.33]), IL-10 (placebo-control=1.116 µg/µl [SEM 0.22], - LLLT=0.352 µg/µl [SEM 0.15]), and COX-2 (placebo-control=4.984 µg/µl [SEM 1.18], LLLT=1.470 µg/µl [SEM 0.73]).

CONCLUSION

Irradiation of superpulsed LLLT on successive days five times per week for 14 weeks decreased morphological changes, skeletal muscle damage and inflammation in mdx mice. This indicates that LLLT has potential to decrease progression of Duchenne muscular dystrophy.