Physiological Characterization of Muscle Strength With Variable Levels of Dystrophin Restoration in MDX Mice Following Local Antisense Therapy

Mol Ther. 2011 Jan;19(1):165-71. doi: 10.1038/mt.2010.213. Epub 2010 Oct 5.

Abstract

Antisense-induced exon skipping can restore the open reading frame, and thus correct the dystrophin deficiency that causes Duchenne muscular dystrophy (DMD), a lethal muscle wasting condition. Successful proof-of-principle in preclinical models has led to human clinical trials. However, it is still not known what percentage of dystrophin-positive fibers and what level of expression is necessary for functional improvement. This study directly address these key questions in the mdx mouse model of DMD. To achieve a significant variation in dystrophin expression, we locally administered into tibialis anterior muscles various doses of a phosphorodiamidate morpholino oligomer (PMO) designed to skip the mutated exon 23 from the mRNA of murine dystrophin. We found a highly significant correlation between the number of dystrophin-positive fibers and resistance to contraction-induced injury, with a minimum of 20% of dystrophin-positive fibers required for meaningful improvement. Furthermore, our results also indicate that a relatively low level of dystrophin expression in muscle fibers may have significant clinical benefits. In contrast, improvements in muscle force were not correlated with either the number of positive fibers or total dystrophin levels, which highlight the need to conduct appropriate functional assessments in preclinical testing using the mdx mouse.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Dystrophin / biosynthesis*
  • Dystrophin / genetics
  • Dystrophin / metabolism
  • Exons
  • Female
  • Genetic Therapy / methods
  • Mice
  • Mice, Inbred mdx
  • Models, Animal
  • Morpholines / metabolism
  • Morpholines / pharmacology*
  • Morpholinos
  • Muscle Contraction
  • Muscle Fibers, Skeletal / metabolism
  • Muscle Strength / drug effects
  • Muscle Strength / genetics
  • Muscle Strength / physiology*
  • Muscular Dystrophy, Duchenne / genetics
  • Muscular Dystrophy, Duchenne / metabolism
  • Muscular Dystrophy, Duchenne / physiopathology*
  • Muscular Dystrophy, Duchenne / therapy*
  • Oligonucleotides, Antisense / genetics
  • Oligonucleotides, Antisense / metabolism
  • Oligonucleotides, Antisense / pharmacology*
  • Open Reading Frames
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / genetics

Substances

  • Dystrophin
  • Morpholines
  • Morpholinos
  • Oligonucleotides, Antisense
  • RNA, Messenger