Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Anatomy and Cell Biology

Collaborative Specialization

Musculoskeletal Health Research

Supervisor

Hoffman, Lisa

Abstract

Duchenne muscular dystrophy (DMD) is the most common inherited pediatric muscle dystrophy. It is characterized by muscle degeneration, resulting in fibrosis that is a significant impediment to both endogenous muscle repair and any potential regenerative strategy. At present, there are few therapies that specifically address fibrosis and microenvironment improvement, but one possibility rests in targeting the Wilms’ tumour 1 (Wt1) protein. Wt1 is a zinc finger transcription factor, recently shown to be expressed in fibrotic conditions such as Dupuytren’s disease and pulmonary fibrosis. This thesis examines the expression pattern of Wt1 in several mouse models of DMD, through both histological quantification of Wt1 protein, and quantification of Wt1 isoform mRNA. Additionally, fibrosis is quantified through Masson’s trichrome staining of collagen. An increased proportion of Wt1 immunoreactive nuclei was found in the diaphragm and gastrocnemius of DMD disease models prior to and during early fibrosis, but returned to basal levels during late fibrosis. These results suggest that nuclear Wt1 immunoreactivity may precede college deposition, and that it should be investigated further in the future.

Summary for Lay Audience

Duchenne muscular dystrophy (DMD) is a severe muscle disorder affecting children. DMD has no cure, and most patients with the disease are expected to only live to their mid-twenties. The most recognizable symptoms of DMD are muscle weakness and muscle loss. DMD is a genetic condition, caused by a mutation in the gene that normally produces dystrophin protein. Genes make proteins by first making RNA, which can then be read by cells to assemble the protein. Dystrophin is an important protein for maintaining the structure of muscle cells. Mutations in the gene which produces dystrophin can make the dystrophin it produces not function properly. When the function of dystrophin is reduced, muscle cells become more likely to die. Over time, this increased muscle cell death causes scarring inside of muscles, preventing muscles from functioning properly. This scarring acts as a barrier, preventing both normal muscle repair and treatments to increase muscle function. Presently, there are few treatments that specifically target this scarring, but one possibility rests in targeting the Wilms' Tumor 1 (Wt1) protein. Wt1 is a protein which can alter the production of other proteins. It was originally found in cancer, but it has recently been shown to be expressed in some diseases where scarring occurs, such as Dupuytren’s disease. This indicates its production might occur when scarring occurs. This thesis examines the patterns of Wt1 production in several mouse models of DMD. This is done by, in these models, staining Wt1 protein and looking at it under a microscope, and also examining how much RNA of Wt1 is made. Additionally, scarring is examined by staining the scar tissue and examining it under a microscope. The percent of cell nuclei which had Wt1 inside of them was found to be increased prior to, and during, scarring, but decreased back down to normal levels after scarring had taken place. These results suggest that an increased presence of Wt1 in the nucleus may take place before scarring, and that it should be investigated further.

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