Degree Type

Dissertation

Date of Award

2014

Degree Name

Doctor of Philosophy

Department

Animal Science

Major

Genetics

First Advisor

Joshua T. Selsby

Abstract

Duchenne muscular dystrophy (DMD) is caused by a mutation in the dystrophin gene leading to the production of a nonfunctional protein and a dystrophin deficiency. Dystrophic muscle becomes progressively more necrotic and fibrotic eventually causing impaired muscle function. Patients are typically diagnosed due to the loss of muscle function indicating advanced disease, therefore successful treatments need to be able to rescue dystrophin-deficient muscle from further decline. It has been demonstrated that Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) over-expression can prevent disease onset in mdx mice, a mouse model for DMD. As a next step, the work presented here evaluated the extent to which PGC-1α over-expression rescued dystrophic muscle during the initial bout of necrosis (three weeks of age) as well as after prolonged disease progression (one year of age). AAV6 was used to deliver the PGC-1α gene to a single hind limb while the contralateral limb was given a control injection. PGC-1α gene transfer improved muscle function and histopathology when delivered during the initial bout of necrosis. Also, beneficial changes in genes involved in dystroglycoprotein complex (DGC) assembly, oxidative metabolism, muscle repair, and autophagy were observed. While PGC-1α gene transfer following prolonged disease rescued some aspects of muscle function the cumulative effects were more modest. To increase the clinical relevance of this work the orally-available PGC-1α pathway activator quercetin was evaluated for its ability to mitigate histopathology in dystrophic skeletal muscle. Using a rescue paradigm prolonged quercetin supplementation led to improved histopathology and increased mitochondrial biogenesis compared to control-fed animals.

Because of a variety of differences between animal models and human patients their usefulness as translational models is limited. To that end dystrophin insufficient pigs were evaluated as a novel translational model. At eight weeks of age dystrophin insufficiency resulted in failure of the DGC to localize to the sarcolemma. This was associated with increased histopathology in a muscle-specific manner. Since pigs are closer in size, physiology, anatomy and genetics to humans and also appear to recapitulate many aspects of dystrophinopathies we believe they will make for a good translational animal model for future therapeutic studies.

Copyright Owner

Katrin Hollinger

Language

en

File Format

application/pdf

File Size

174 pages

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