Translational studies of GAA deficiency in bioengineered human muscle

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Glycogen storage disease type II (Pompe disease) is a fatal degenerative disease caused by the deficiency of acid-alpha glucosidase (GAA) or acid maltase. This disease is characterized by progressive myopathy resulting from the accumulation of lysosomal glycogen in skeletal and cardiac muscle cells. Enzyme replacement therapy (ERT) with recombinant human GAA is the only FDA-approved treatment for Pompe disease, which despite being beneficial, is highly expensive and inefficient, requiring enzyme doses 100-fold greater than those used for other lysosomal disorders. Furthermore, the ability of ERT to correct important aspects of the disease including autophagy, glycogen accumulation, and low exercise capacity, remains questionable. Therefore, the need for the development of alternative or adjuvant therapies to ERT is obvious, and although the mouse GAA knockout (GAA-KO) model is often utilized for this purpose, the differences in size and physiology of mice and humans and less severe disease phenotype in mice limit the translational utility of these studies. Human cells isolated from patients' muscle biopsies offer an alternative system to study muscle disease in vitro, however, no methods exist to generate functional contractile muscle fibers starting from human muscle cells. In this project we for the first time describe engineering of contractile, electrically responsive human muscle tissues ("bioartificial muscle") made of primary myogenic cells obtained using standard muscle biopsies from normal individuals and Pompe disease patients. We propose to utilize these 3D cell cultures as a predictive in vitro screen for candidate drug and gene therapeutics for human muscle disease. By combining bioengineering and clinical expertise of the two principal investigators, we will carry out a set of translational in vitro and in vivo studies in order to screen and validate alternative and adjuvant drug and gene therapies for Pompe disease. In particular, we will: 1) Optimize functional properties of healthy and Pompe disease human bioartifical muscle tissues and systematically characterize their molecular, metabolic and functional properties, 2) Mechanistically study novel candidate drug and AAV therapies for Pompe disease using GAA-KO mice, and 3) Screen the efficacy of these candidate approaches in vitro using engineered human Pompe disease muscle and further validate the most promising therapies in vivo using a novel humanized mouse model of Pompe disease. In the future, the experimental framework established in this project will allow us to undertake similar translational studies to aid treatment of other skeletal and cardiac muscle disorders.