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Laminin protein therapies for zebrafish models of MDC1A and muscle regeneration
thesisposted on 2017-02-24, 01:32 authored by Ehrlich, Ophelia Vincentia
Merosin deficient congenital muscular dystrophy (MDC1A) is a disease that affects laminin protein within skeletal muscle and the peripheral nervous system. Laminin deficiency leads to severe muscle degeneration, fibrosis and premature mortality. The extracellular protein, laminin helps anchor the muscle cell membrane to the extracellular matrix (ECM) through important attachment sites mediated by Integrin-α7β1 and the Dystrophin-associated glycoprotein complex (DGC). Muscle fibre detachment that leads to apoptosis occurs when laminin protein is defective in forming these attachment sites. Studies have suggested that laminin protein could also have a direct effect on the muscle stem cell niche, although it is unknown if these cells are in fact affected in an in vivo MDC1A context. Muscle stem cells are involved in development, growth and regeneration of skeletal muscle and this thesis identifies defective muscle maintenance as a characteristic of laminin deficiency. Researchers are interested in finding and developing a viable therapeutic for this disease and zebrafish disease models provide an invaluable tool on this path. Transgenic systems have shown the importance of laminin-α1 expression in ameliorating the laminin-α2 deficient pathology, and the introduction of free Laminin-111 protein has also been shown to improve dystrophic phenotypes. This thesis examines Laminin-111 protein in a therapeutic context and determines its affect on the muscle stem cell niche in the laminin-α2 deficient zebrafish model. With the advent of readily available biomaterials such as self-assembling hydrogels, wild-type laminin protein can be delivered directly to target tissue and potentially reverse dystrophic phenotypes. This thesis examines the ability of a biomaterial to deliver laminin protein to a localised area and in vitro studies were also performed to test and refine its biocompatibility.These results demonstrate that laminin protein has pro-regenerative qualities. I further explore if a laminin treatment can improve muscle regeneration via stimulating the muscle stem cell population. A laminin biomaterial treatment is examined within an acute injury model. Adult zebrafish skeletal muscle has not been well studied and no standard adult skeletal muscle injury model has been developed. As this is a localised injury it is appropriate to deliver the laminin focally via the previously described biomaterial. These studies explore laminin protein treatments and its effect on muscle stem cell niche in two muscle models, the lama2-/- mutant and an adult muscle injury model, to further characterise laminin proteins potential as a therapy.