A77-17 Systemic Aav Gene Therapy to Rescue Respiratory Pathology in a Murine Model of Duchenne Muscular Dystrophy

Introduction

Duchenne muscular dystrophy (DMD) is an X-linked severe neuromuscular disorder caused by a lack of dystrophin which results in progressive muscle degeneration. Eventually, dystrophic muscle changes are seen with repetitive muscle damage leading to loss of ambulation and cardiorespiratory insufficiency. Despite supportive care, cardiorespiratory failure is the leading cause of mortality in patients with DMD. Adeno-associated viral (AAV) gene therapy is an FDA approved therapy for the treatment of DMD. However, the extent to which gene therapy effectively impacts respiratory function remains unclear. This study aims to utilize a systemic injection of AAV carrying a microdystrophin (μDys) to target and treat respiratory pathology in a mouse model of DMD.

Methods

Three groups of mice were studied: mdx mice treated with saline (n = 8), mdx mice treated with AAV-μDys (n = 8) and wild type (WT) control mice treated with saline (n = 8). All groups received systemic injection through tail vein administration. Whole body plethysmography (WBP) at 8 weeks of age and every 2 months until 56 weeks of age to assess respiratory function at baseline during normoxia (FiO2: 0.21; N2 balance) and during respiratory challenge with hypoxia and hypercapnia (FiCO2: 0.07, FiO2: 0.10; N2balance). In addition, forced oscillation technique (FOT) was performed at the end of the study to evaluate respiratory mechanics and tissue-specific parameters. Histologic analysis was performed of the diaphragm, tongue, and tibialis anterior to assess for muscle fiber regeneration, presence of dystrophin and fibrosis.

Results

mdx mice treated with AAV-μDys did not show a significant difference in respiratory parameters during normoxia throughout the study. However, at 48 weeks of age, the AAV-μDys treated mdx mice exhibited increased tidal volume, minute ventilation, peak inspiratory flow, and peak expiratory flow during the respiratory challenge when compared with saline treated mdx mice. FOT at the terminal study point revealed reduced lung stiffness and increased compliance in the treated vs untreated mdx mice. qPCR showed vector genome biodistribution in the diaphragm, and histological analysis revealed positive dystrophin immunohistochemistry staining. Hematoxylin and eosin staining showed decreased cellular infiltration in the diaphragm, and sirius red staining revealed decreased fibrosis in the mdx mice treated with AAV-μDys group when compared with mdx mice treated with saline.

Conclusion

Overall, these data indicate that AAV gene therapy ameliorates restrictive respiratory disease and improves structural diaphragm muscle pathology in mdx mice.

This abstract is funded by: NIH