Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Anatomy and Cell Biology

Supervisor

Dr. Lisa M. Hoffman

Abstract

Duchenne muscular dystrophy (DMD) is a devastating neuromuscular disorder that affects approximately 1 in 5000 males. Vascular-targeted therapy has been proposed as a treatment for DMD to reduce ischemia and enhance endogenous repair. Additionally, a more vascularized environment may enhance regenerative approaches currently under investigation. Vascular endothelial growth factor (VEGF) and angiopoietin-1 (ANG1) are two of the most studied pro-angiogenic factors for this approach. To date, little is known regarding the effect of these pro-angiogenic factors on muscle function and whether they may exacerbate fibrosis in a relevant murine model of DMD. The first aim of this thesis was to determine the murine model that is best suited for assessing vascular therapy. We demonstrate the dystrophin null, utrophin heterozygous mouse (mdx/utrn+/-) develops more collagen deposition at an earlier age than the commonly used mdx mouse and is therefore a superior choice for assessing therapeutic effects on fibrosis. Next, we investigated the effect of exogenous VEGF treatment on fibroblasts derived from severely affected diaphragm and mildly affected gastrocnemius muscles of mdx/utrn+/- mice. VEGF treatment induced differentiation into myofibroblasts in both cell types, suggesting induction of a fibrotic response. The final aim of the thesis was to assess the effect of VEGF alone or in combination with ANG1 on functional perfusion as assessed non-invasively using dynamic contrast-enhanced computed tomography. A combination of VEGF and ANG1, but not VEGF alone, slowed progression of ischemia in the mdx/utrn+/- hind limb. Increased vessel maturation, as assessed histologically, validated the imaging findings. The combination treatment also decreased fibrosis and leukocyte infiltration, consistent with decreased vascular permeability following ANG1 treatment. Overall, the research in this thesis highlights the drawbacks to use of VEGF as a treatment for ischemia associated with DMD and reveals considerations for future use of vascular therapy in murine models of the disease.

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