AAVcc47-μDys Gene Therapy Ameliorates Respiratory Pathology in mdx Mouse Model of Duchenne Muscular Dystrophy.

Duchenne muscular dystrophy (DMD) is a progressive X-linked neuromuscular disorder caused by deficiency of dystrophin - a protein essential for muscle integrity. Loss of dystrophin results in global muscle weakness, including in the muscles of respiration. As a result, respiratory failure is a leading cause of morbidity and mortality in patients with DMD. Gene therapy using adeno-associated virus (AAV) is ideal for monogenetic diseases. However, the dystrophin gene is too large to be packaged into AAV; therefore, microdystrophin (μDys) containing important elements of the dystrophin gene is used instead. The U.S. Food and Drug Administration recently approved AAV-μDys for treatment of DMD; however, the impact of this therapy on respiratory function is unknown. Thus, in this study, we evaluated the impact of AAV-μDys on respiratory function in the mdx mouse model of DMD. We utilized a novel vector AAV.cc47 because of affinity for the diaphragm and enhanced cross-species transduction efficiency. The mdx mice received a single dose of AAV.cc47-μDys (1.33 × 10¹⁴ vg/kg) intravenously at 8 weeks and underwent longitudinal respiratory assessment using whole-body plethysmography during normoxia and a respiratory hypoxic-hypercapnic challenge. Terminal evaluation of pulmonary mechanics by forced oscillation was performed at 60 weeks, followed by postmortem analysis. AAV.cc47-μDys-treated mdx mice demonstrated significant but partial improvements in respiratory function and pulmonary mechanics compared to untreated mdx controls. These functional improvements were accompanied by increased dystrophin expression and reduced inflammation and fibrosis in the diaphragm, the major inspiratory muscle. Our findings demonstrate that AAV.cc47-μDys partially improves respiratory function and muscle pathology.