Restoration of dystrophin expression and motor function in using exosomes-based non-immunogenic genetic therapy

Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disorder caused by a recessive X-linked genetic mutation in the gene encoding dystrophin. Currently, there is no cure for DMD, and recent efforts have focused on viral-based modes of gene delivery to express truncated forms of dystrophin, or rely on exon skipping strategies to skip the locus of mutation. Here we utilized bioengineered exosomes, 40–100 nm sized extracellular vesicles, to deliver full-length dystrophin mRNA (dmd) to mdx mice allogenically. C57BL/10ScSn-Dmdmdx (mdx) mice (~14–15 weeks old) were randomly divided into prednisolone (PRED, 2 mg/kg BW/day), vehicle (VEH, i.v. injections of 0.9% sterile saline), exosomes only (EXO, i.v. injections of empty exosomes), and exosomes + dmd mRNA (EXO + mRNA, i.v. injections of exosomes containing 150 ng of dmd mRNA) groups. C57BL/10ScSn wild type (WT) mice were also included as control animals. Treatment of mdx mice with exosomes + dmd mRNA rescued the absence of dystrophin protein expression in skeletal muscle (EDL, SOL, TA, diaphragm), and heart as assessed by Western blotting and immunohistochemistry. This occurred in tandem with a complete attenuation in elevated serum creatine kinase levels, muscle hypertrophy, and grip strength deficits. Furthermore, necrosis and % fibers with centralized myonuclei were reduced in EXO + mRNA to levels observed in WT mice. Moreover we treated dermal fibroblasts isolated from control and DMD patients with dmd mRNA only, exosomes only, and exosomes + dmd mRNA. Similar to our in vivo observations, we restored dystrophin protein expression in DMD patients treated with our bioengineered exosomes. Our data clearly establish treatment with non-immunogenic bioengineered exosomes as efficient delivery vehicles for treating diseases of genetic origin such as DMD.