Wild-Type Mouse Models to Screen Antisense Oligonucleotides for Exon-Skipping Efficacy in Duchenne Muscular Dystrophy

Abstract

A readily available animal model is essential for rapidly identifying effective treatments for Duchenne muscular dystrophy (DMD), a devastating neuromuscular disorder caused by the lack of dystrophin protein, which results from frame-disrupting mutations in the DMD gene. Currently, the mdx mouse is the most commonly used model for antisense oligonucleotide (AO)-mediated exon skipping pre-clinical studies, with a mild phenotype. However, the accessibility of mdx mouse colonies particularly in developing countries can constrain research. Therefore in this study we explore the feasibility of using wild-type mice as models to establish exon-skipping efficiency of various DMD AO chemistries and their conjugates. Four different strains of wild-type mice and six different AO chemistries were investigated intramuscularly and the results indicated that the same exon-skipping efficiency was achieved for all tested AOs as that from mdx mice. Notably, levels of exon-skipping obtained in C57BL6 and C3H and mdx mice were most closely matched, followed by ICR and BALB/C mice. Systemic validation revealed that wild-type mice are less responsive to AO-mediated exon skipping than mdx mice. Our study provides evidence for the first time that wild-type mice can be appropriate models for assessing DMD AO exon-skipping efficiency with similar sensitivity to that of mdx mice and this finding can further accelerate the development of effective DMD AOs.

Renadirsen, a Novel 2′OMeRNA/ENA® Chimera Antisense Oligonucleotide, Induces Robust Exon 45 Skipping for Dystrophin In Vivo

“…Therefore, PMO is not expected to be delivered in terminally differentiated or nonregenerative cells such as cardiomyocytes. Furthermore, in in vivo studies, the systemic administration of PMO in healthy WT mice was not as effective as that in mdx mice under the same dosing regimens [41,42], whereas the systemic administration of renadirsen sodium produced clear exon-skipping activity even in WT mice in our study. Therefore, renadirsen is assumed to have cellular uptake superior to that of PMOs in muscle tissues and cells even under normal conditions.…”

Peptide Nucleic Acid Promotes Systemic Dystrophin Expression and Functional Rescue in Dystrophin-deficient mdx Mice

“… 26 Notably, PNA AOs showed superiority to 2'Ome RNA and comparable activity to phosphorodiamidate morpholino oligomer (PMO) from local intramuscular studies. 27 However, the systemic potential of PNA in restoring dystrophin expression and rescuing the phenotypic pathology of mdx mice remains to be explored, particularly at doses comparable to those of 2'Ome RNA and PMO as reported. 15 , 16 …”

Splice modulating antisense oligonucleotides restore some acid-alpha-glucosidase activity in cells derived from patients with late-onset Pompe disease

“…Accordingly, we propose it may be possible to tread the path set for the first DMD exon skipping study reported by Kinali and colleagues 56 : an intramuscular injection into late-onset Pompe disease patients as a single-blind, placebo-controlled, dose-escalation, proof-of-concept study. Although our study was performed in MyoD induced primary fibroblast cells, uptake of PMO into muscle cells should not be a limitation since intramuscular injection of PMO in healthy mouse strains have shown efficient uptake by muscle cells 57 . From the many lessons learned, we hope that it does not take more than a decade to get a splice switching treatment for GSD II into the clinic.…”