Abstract
In Pompe disease, the deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA) causes skeletal and cardiac muscle weakness, respiratory failure, and premature death. While enzyme replacement therapy using recombinant human GAA (rhGAA) can significantly improve patient outcomes, detailed disease mechanisms and incomplete therapeutic effects require further studies. Here we report a three-dimensional primary human skeletal muscle (“myobundle”) model of infantile-onset Pompe disease (IOPD) that recapitulates hallmark pathological features including reduced GAA enzyme activity, elevated glycogen content and lysosome abundance, and increased sensitivity of muscle contractile function to metabolic stress. In vitro treatment of IOPD myobundles with rhGAA or adeno-associated virus (AAV)-mediated hGAA expression yields increased GAA activity and robust glycogen clearance, but no improvements in stress-induced functional deficits. We also apply RNA sequencing analysis to the quadriceps of untreated and AAV-treated GAA−/− mice and wild-type controls to establish a Pompe disease-specific transcriptional signature and reveal novel disease pathways. The mouse-derived signature is enriched in the transcriptomic profile of IOPD vs. healthy myobundles and partially reversed by in vitro rhGAA treatment, further confirming the utility of the human myobundle model for studies of Pompe disease and therapy.
Highlights
In Pompe disease, the deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA) causes skeletal and cardiac muscle weakness, respiratory failure, and premature death
Morphological analysis revealed no difference in total, F-actin+, or myomesin+ crosssectional areas (CSA) between healthy and infantile-onset Pompe disease (IOPD) myobundles (Fig. 1i–k), and, along with no difference in sarcomeric α-actinin (SAA) protein expression (Fig. 1l), revealed that IOPD satellite cells retained normal capacity for in vitro expansion, myofiber formation, and muscle differentiation
Consistent with the clinical studies[8,44], these results suggest that recombinant human GAA (rhGAA) therapy yields only a partial rescue of IOPD phenotype in human skeletal muscle, signifying the need for improved treatment modalities
Summary
In Pompe disease, the deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA) causes skeletal and cardiac muscle weakness, respiratory failure, and premature death. We report a three-dimensional primary human skeletal muscle (“myobundle”) model of infantile-onset Pompe disease (IOPD) that recapitulates hallmark pathological features including reduced GAA enzyme activity, elevated glycogen content and lysosome abundance, and increased sensitivity of muscle contractile function to metabolic stress. The current standard of care treatment for Pompe disease, enzyme replace therapy (ERT), consisting of frequent intravenous infusions of recombinant human GAA (rhGAA), reduces muscle glycogen and can improve muscle function and patient quality of life[8,9,10,11]. IOPD myobundles exhibited GAA deficiency, elevated glycogen, and lysosomal enlargement, but displayed functional characteristics similar to those of healthy myobundles
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