Abstract 712: Prevention of Acute Heart Failure in Dystrophin-Deficient Mice by Systemic Administration of Pseudotype rAAV- micro-Dystrophin In Vivo
Background: Duchenne muscular dystrophy (DMD) is a debilitating and fatal disease characterized by both skeletal muscle pathology and cardiomyopathy. DMD results from deletions of the cytoskeletal protein dystrophin (DYS). Due to the challenges of vector-mediated expression the full-length DYS (14 kb cDNA), functional truncations have been designed and shown to be effective in improving skeletal muscle pathology of the mdx mouse, an animal model of DMD. To date, none of these truncated forms have been functionally assessed in cardiac tissue.
Hypothesis: Expression of truncated micro-DYS will reconstitute the components of the dystroglycan complex and improve the functional performance of the myocardium.
Methods/Results: A single intravenous injection of high titer (~1012 vector genomes/mouse) adeno-associated virus (serotype 2/6 AAV)-LacZ resulted in strong and uniform expression of LacZ in the heart 10 days after injection, demonstrating the high efficacy of this approach. Intravenous injection of mdx mice with AAV-micro-DYS (3.7 kb cDNA) resulted in strong and uniform expression of micro-DYS throughout the myocardium 10 weeks following systemic delivery. Furthermore, quantitative Western blotting showed increased levels of dystroglycan complex proteins in treated mice. The cardiac function of micro-DYS treated mice was assessed by pressure-volume catheterization at baseline and during a dobutamine stress test. At baseline conditions the end-diastolic volume of the mdx mouse was significantly smaller compared to controls (20 ± 2 μl (n = 10) vs. 31 ± 3 μl (n = 8); P< 0.05), and was fully corrected by the expression of micro-DYS (31 ± 3 μl (n = 8); P > 0.05 vs. Control). Under stress conditions of a 30 min dobutamine challenge, 40% of mdx mice developed acute heart failure. Most importantly, acute failure was nearly completely blocked in the micro-DYS expressing mdx mice (P < 0.02; n = 8).
Conclusion: A truncated dystrophin when expressed in the hearts of mdx confers protection from stress-induced acute heart failure. Systemic delivery of genes to the myocardium by rAAV2/6 raises the prospect of genetic inventions to redress inherited and acquired cardioavascular disease.