Pathology - Theses
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ItemCharacterization and therapeutic treatment in a transgenic mouse model of Amyotrophic Lateral Sclerosis( 2010)Amyotrophic Lateral Sclerosis (ALS) is a devastating adult–onset fatal neurodegenerative disorder that is characterized by loss of cortical and spinal motor neurons. This results in the clinical characteristics of muscle wasting and spasticity leading to paralysis and eventually death through respiratory failure within a period of 2-5 years from symptom onset. The aetiology of ALS is poorly understood and the neurodegenerative processes involved in ALS progression are diverse and complicated. Mutations in the superoxide dismutase (SOD1) gene are associated with a subset of familial ALS cases. There is considerable evidence implicating oxidative stress as a central mechanism in motor neuron death. However, the exact mechanism by which mutant SOD1 leads to motor neuron death has not been defined. Recent studies have shown that mutations in TDP-43 are linked to motor neuron degeneration in ALS, thus implicating TDP-43 as a new key player in ALS pathogenesis. How TDP-43 and SOD1 interact in ALS is not understood. ALS animal models have been developed to investigate the ALS disease processes. Overexpression of mutant SOD1 in mice has been found to imitate most of the disease phenotype observed in ALS patients. However this model has an aggressive phenotype which may complicate comparisons with slower progressing human ALS. The studies described in this thesis were designed to characterize a low copy transgenic SOD1G93A (TgSOD1G93A) mouse model by examining its behavioral aspects and protein markers associated with ALS. These mice may potentially provide a more appropriate model of human ALS. After characterization, we examined the efficacy of a novel potential therapeutic metallo-complex (bis(thiosemicarbazone-copper complex) (btsc) against disease progression in the TgSOD1G93A low copy mice. Treated mice were analyzed for behavioral, biochemical and immunohistochemical changes. TgSOD1G93A low copy mice were first characterized at different stages of their disease progression. Onset of TgSOD1G93A low copy mice disease symptoms was identified by significant body weight loss at 182 ± 2.3 days, followed by motor impairment at 205 ± 2.0 days and end stage disease at 263 ± 2.9 days. Significant motor neuron loss was apparent at 160 days through histochemical analysis of mouse lumbar spinal cord. Protein carbonyl (oxidative stress marker) levels were observed to be significantly elevated from symptom onset at 200 days. In addition, astrocytes and microglia activation were apparent throughout the 200 and 270 (end stage) day old spinal cord. After characterization of the low copy TgSOD1G93A model, animals were treated with potentially therapeutic CuII (btsc) metallo-complexes, (CuII(atsm) and CuII(gtsm)). CuII(atsm) treatment significantly extended survival, delayed disease onset and slowed disease progression in the TgSOD1G93A low copy mice. These therapeutic effects were associated with an increase in motor neuron survival at 200 and 230 days and a significant reduction in oxidative stress levels observed in both 230 day and end stage mouse spinal cord. In addition, astrogliosis was significantly attenuated. CuII(gtsm) treatment showed marginal improvement in survival in a small group of TgSOD1G93A low copy mice. Pathological changes to TDP-43 was examined at different disease progression stages in the TgSOD1G93A low copy and compared to end stage TgSOD1G93A high copy mice. In cytoplasmic fractions of spinal cord, high levels of phosphorylated full length TDP-43 and C-terminal fragment levels were present from pre-symptomatic (130 days) to end stage day old TgSOD1G93A low copy mice but absent in the end stage TgSOD1G93A high copy mice. Further evidence of altered TDP-43 homeostasis was reflected in positive cytoplasmic TDP-43 staining observed in symptomatic (200 day) and end stage TgSOD1G93A low copy mice. These results are consistent with published literature which reported that TDP-43 undergoes cleavage and phosphorylation, resulting in motor neuron death. Therefore, we examined the effects of CuII(atsm) treatment in the TgSOD1G93A low copy mice and observed decreased phosphorylated TDP-43. In conclusion, this thesis has characterized the TgSOD1G93A low copy mouse and demonstrated that a potential therapeutic compound for treatment of ALS, CuII(atsm), has robust protective effects. CuII(atsm) substantially increased animal survival and inhibited oxidative stress and TDP-43 pathological processing in the TgSOD1G93A low copy mice. These studies have important implications for the development of novel therapeutic approaches to treat ALS.