Orientador: Elaine Minatel / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-24T19:48:05Z (GMT). No. of bitstreams: 1 Moraes_LuisHenriqueRapucci_D.pdf: 3874036 bytes, checksum: 7d72faf59790ed5f085eb2edd9aba075 (MD5) Previous issue date: 2014 / Resumo: Devido ao fato dos camundongos mdx, modelo experimental da distrofia muscular de Duchenne, apresentarem peroxidação lipídica da membrana causada pelo aumento da produção espécies reativas de oxigênio (EROs) no período que antecede o início da degeneração das fibras musculares, sugere-se que o estresse oxidativo pode ser um dos mecanismos primários da degeneração muscular distrófica, ao invés de ser um efeito secundário deste processo. Camundongos mdx tratados com o antioxidante N-acetilcisteína (NAC) apresentaram diminuição da degeneração muscular. De acordo com a literatura a associação de NAC com Deferoxamina (DFX) produz resultado mais efetivo contra o estresse oxidativo do que a administração de NAC isoladamente. Desta forma, o objetivo do presente estudo foi de verificar, através de análises morfológica, celular e bioquímica, se o tratamento in vivo e in vitro com a associação de NAC e DFX diminui a produção das EROs. Para os estudos in vivo foram utilizados camundongos C57BL/10 (grupo controle) e camundongos mdx, com 14 dias de vida pós-natal. Os camundongos mdx e C57BL/10 foram divididos em 4 grupos experimentais: tratados com salina, tratados com NAC+DFX, tratados com DFX e tratados com NAC (150 mg/kg) por 14 dias. Todos os animais foram submetidos à análise de medida de força. Os músculos Esternomastóideo (STN), Diafragma (DIA) e Tibial Anterior (TA) foram retirados e submetidos às técnicas histológicas (HE, azul de Evans e reação de DHE), Western Blotting (TNF-?, NF-?B, MyoD, MAFbx e 4-HNE). Plasma sanguíneo foram utilizadas para determinação de creatina quinase (CK) e de citocinas inflamatórias. Nos experimentos in vitro foram utilizados os músculos do membro pélvico de camundongos C57BL/10 e mdx com 14 dias de vida. As culturas de células musculares foram utilizadas para análises de viabilidade celular (Trypan blue, MTT e vermelho neutro), análise de cálcio e Western Blotting após serem tratadas ou não com NAC e DFX. O tratamento com NAC, DFX e NAC+DFX apresentou efeito benéficos sobre as fibras musculares distróficas, tanto nos experimentos in vivo quanto in vitro, reduzindo a degeneração muscular, a inflamação exacerbada, a peroxidação lipídica e a produção de EROs. Tanto o tratamento isolado dos medicamentos quanto a associação apresentou potencial efeito, entretanto em alguns experimentos a associação mostrou-se mais eficaz contra os danos provocados pela distrofia / Abstract: Due the fact of mdx mice, an experimental model of Duchenne muscular dystrophy, presenting the lipid peroxidation of membrane caused by increased production of reactive oxygen species (ROS) in the period that preced the onset of muscle fibers degeneration, it is suggested that stress oxidative may be one of the primary mechanisms of dystrophic muscle degeneration, rather than a side effect of this process. Mdx mice treated with the antioxidant N-acetylcysteine (NAC) showed a decrease in muscle degeneration. According to the literature the association of NAC with Deferoxamine (DFX) produces more effective results against oxidative stress than NAC alone. Thus, the aim of this study was to verify, through morphological analysis, cellular and biochemistry, if the in vivo and in vitro treatment with the combination of NAC and DFX decreases the ROS production. For in vivo studies were used C57BL/10 mice (control group) and mdx mice, with 14 days postnatal. The mdx and C57BL/10 mice were divided into 4 experimental groups: treated with saline, treated with NAC + DFX, treated with DFX and treated with NAC (150 mg/kg) for 14 days. All animals were subjected to strength measurement analysis. The Sternomastoid (STN), Diaphragm (DIA) and Tibialis anterior (TA) muscles were removed and submitted to histological techniques (HE, Evans blue dye and DHE reaction), Western Blotting (TNF-?, NF-kB, MyoD, MAFbx and 4-HNE). Blood plasma was used for determination of Creatine kinase (CK) and inflammatory cytokines. In the in vitro experiments, the muscles of the pelvic limb of C57BL/10 and mdx mice with 14 days postnatal were used. The muscles culture cells were used for cell viability analysis (Trypan blue, MTT and Neutral red), calcium analysis and Western blotting after being treated or not with NAC and DFX. Treatment with NAC , DFX and NAC + DFX showed benefic effect on dystrophic muscle fibers, both in vivo and in vitro experiments, reducing muscle degeneration, exacerbated inflammation, lipid peroxidation, and ROS production. Either the isolated or the combination treatment of medication showed a potential effect, however in some experiments the combination was more effective against the damage caused by the disease / Doutorado / Anatomia / Doutor em Biologia Celular e Estrutural

Orientador: Maria Julia Marques / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-19T19:42:06Z (GMT). No. of bitstreams: 1 Machado_RafaelVentura_D.pdf: 18399994 bytes, checksum: 2db06c9364e5b215f2cf4f91753c4d19 (MD5) Previous issue date: 2011 / Resumo: Na distrofia muscular de Duchenne e no camundongo mdx a proteína distrofina está ausente ou é expressa de forma não funcional. Com isso, o complexo distrofina-glicoproteínas se desorganiza, a fibra muscular se torna frágil durante os ciclos de contração e relaxamento muscular, as concentrações intracelulares de cálcio e radicais livres se elevam, resultando em necrose da célula. A inflamação mediada por células do sistema imunológico e citocinas pró-inflamatórias, como o TNF-alfa, é um evento importante diretamente relacionado com a progressão da doença. O ácido eicosapentaenóico (EPA) é um ácido graxo poli-insaturado ômega-3 que promove benefícios em doenças inflamatórias em humanos. No presente trabalho analisamos os efeitos do EPA no estágio inicial da distrofinopatia do camundongo mdx. Camundongos mdx com 14 dias de idade receberam 300 mg/kg/dia de EPA por 16 dias. Os grupos controle mdx e C57BL10 receberam óleo mineral. EPA diminuiu a mionecrose, os níveis séricos da enzima creatinoquinase e o TNF-alfa em músculos esqueléticos distróficos. Sugere-se que o EPA tenha utilidade terapêutica nas distrofinopatias / Abstract: In Duchenne muscular dystrophy (DMD) and in the mdx murine model of DMD, lack of dystrophin leads to myonecrosis and cardiorespiratory failure. The intense inflammatory reaction, mediated by immune cells and TNF-alpha, contributes to the progressive myonecrosis. The eicosapentaenoic acid (EPA) is an omega-3 fatty acid that shows beneficial effects in inflammatory diseases. In the present study, we examined the effects of EPA on the early stages of dystrophy in mdx mice. Mdx mice (14 days old) received EPA at 300 mg/kg EPA for 16 days, while the control mdx mice and C57BL10 received vehicle. EPA treatment decreased creatine kinase and TNF-alpha levels and reduced myonecrosis. The present results support further studies with EPA as a potential therapy for dystrophinopathies / Doutorado / Anatomia / Doutor em Biologia Celular e Estrutural

Orientador: Maria Julia Marques / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-20T01:04:16Z (GMT). No. of bitstreams: 1 Mauricio_AdrianaFogagnolo_M.pdf: 1763243 bytes, checksum: bb94a0eae96254b7325735da6a1f32c7 (MD5) Previous issue date: 2012 / Resumo: Na Distrofia Muscular de Duchenne (DMD) e no camundongo mdx, modelo experimental da DMD, a ausência de distrofina promove instabilidade do sarcolema e degeneração muscular progressiva. O processo inflamatório que se instala contribui de forma significativa para a fisiopatologia da doença, sendo que antiinflamatórios esteroides são amplamente utilizados para a terapia da DMD. Entretanto, em decorrência da sua ação pouco efetiva e dos efeitos colaterais outras drogas são investigadas com o objetivo de substituir o uso dos corticoides. Em estudo prévio, demonstramos que o ácido eicosapentaenoico, em uma forma altamente purificada, atenuou a mionecrose em músculos esqueléticos de camundongos mdx durante os estágios iniciais da doença. No presente trabalho, verificamos se diferentes formas de ácidos graxos disponíveis comercialmente para o consumo humano (cápsulas de ômega-3 e sementes de linhaça) também teriam efeito protetor nos músculos distróficos, principalmente nos estágios tardios da doença, em que há comprometimento do músculo cardíaco. Animais mdx jovens (14 dias de idade) receberam ômega-3 diariamente, durante 16 dias, via gavagem. Animais mdx idosos (8 meses de idade) receberam sementes de linhaça durante 5 meses. Animais controle mdx, jovens e idosos, receberam óleo mineral e nenhum complemento alimentar, respectivamente. Nos animais jovens, o ômega-3 melhorou a distrofinopatia, reduzindo a mionecrose e o processo inflamatório no músculo mais afetado, o diafragma. Nos animais idosos, a linhaça resultou em melhora da distrofinopatia no diafragma. Entretanto, a fibrose cardíaca, que caracteriza morfologicamente a cardiomiopatia dos animais idosos mdx, não foi alterada pela linhaça, provavelmente devido a diferenças de metabolismo de ácidos graxos entre os músculos esquelético e cardíaco. Sugere-se que ácidos graxos ômega-3, em formulações disponibilizadas comercialmente para uso humano, são potencialmente úteis para o tratamento das distrofinopatias dos músculos estriados esqueléticos, nos estágios inicial e tardio da doença / Abstract: In Duchenne muscular dystrophy (DMD) and in the mdx mice model of DMD, absence of dystrophin promotes instability of the sarcolemma and progressive muscle degeneration. The inflammatory process contributes significantly to the pathophysiology of the disease. Anti-inflammatory steroids are widely used for DMD therapy. However, due to its ineffective action and their side effects, other drugs are investigated in order to replace the use of corticosteroids. Previously, we have demonstrated that eicosapentaenoic acid in a highly purified form inhibit myonecrosis in skeletal muscles of mdx mice during the early stages of the disease. In the present study, we have verified whether different forms of commercially available fatty acids for human (capsules of omega-3 and flaxseed) would also have a protective effect in dystrophic muscles, especially in the later stages of the disease, when cardiac muscle is also affected. Young mdx mice (14 days old) received omega-3 daily for 16 days via gavage. Older mdx mice (8 months old) received flaxseed for 5 months. mdx control group, young and old, received mineral oil and no food supplement, respectively. In young mice, omega-3 inhibits the dystrophinopathy, reducing myonecrosis and inflammatory process in the most affected muscle, the diaphragm. In aged animals, flaxseed resulted in improvement of dystrophinopathy only in the diaphragm. In the dystrophic heart, flaxseed did not inhibit fibrosis, which is a feature of cardiomyopathy in older mdx mice. Possibly, differences in fatty acid metabolism between skeletal and cardiac muscles may explain these differential results. It is concluded that omega-3 fatty acids commercially available for human use are potentially useful for the treatment of skeletal muscle dystrophinopathy, during early and late stages of the disease / Mestrado / Anatomia / Mestre em Biologia Celular e Estrutural

Orientador: Maria Julia Marques / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-20T07:19:08Z (GMT). No. of bitstreams: 1 Moreira_DrielendeOliveira_M.pdf: 2075338 bytes, checksum: 00bb5917e4f176b73c58453340cb3a5e (MD5) Previous issue date: 2012 / Resumo: A Distrofia muscular de Duchenne (DMD) é uma doença caracterizada pela fraqueza muscular progressiva que leva à insuficiência respiratória e cardíaca, resultando em morte por volta dos 30 anos de idade. No camundongo mdx, modelo experimental da DMD, os músculos diafragma e cardíaco são severamente afetados apresentando fibrose semelhante à observada na patologia humana. O objetivo deste trabalho foi investigar os efeitos do tratamento a longo prazo com suramina, uma droga anti-fibrótica, nos músculos diafragma e cardíaco de camundongos mdx idosos. Camundongos mdx (n=20; 8 meses de idade) receberam injeções intraperitoneais de suramina (60 mg/kg), durante 3 meses. Controles mdx (n=20; 8 meses) e C57BL/10 (n=18; 8 meses) foram injetados com solução salina. Os camundongos da linhagem C57BL/10 expressam distrofina e são utilizados como controle da linhagem mdx. A suramina diminuiu os níveis de CK e atenuou a perda da força muscular. No músculo diafragma, a suramina reduziu a área de fibrose e a mionecrose. No músculo cardíaco, houve redução da fibrose, da inflamação e melhora significativa de parâmetros funcionais cardíacos (amplitude das ondas P, Q, R e S do eletrocardiograma). Sugere-se que a suramina possa ser potencialmente útil nas distrofinopatias, atenuando a miopatia nos músculos mais afetados, o coração e o diafragma, nos estágios tardios da doença / Abstract: Duchenne muscular dystrophy (DMD) is a disease characterized by progressive muscle weakness leading to respiratory and cardiac failure, resulting in death around 30 years of age. In the mdx mice model of DMD, diaphragm and cardiac muscles are severely affected in the later stages of the disease, showing intense fibrosis similar to that observed in human pathology. The aim of the present study was to investigate the effects of long-term treatment with suramin, an anti-fibrotic agent, in the diaphragm and cardiac muscles of the mdx mice. Mdx mice (n=20; 8 months of age) received intraperitoneal injections of suramin (60 mg/kg) for 3 months. Mdx controls (n=20; 8 months) and C57BL/10 (n=18; 8 months old) were injected with saline. C57BL/10 mice express dystrophin and are the control strain for the mdx mice. Suramin decreased CK levels and reduced the loss of muscle strength. Suramin reduced fibrosis and myonecrosis in diaphragm. In the cardiac muscle, suramin decreased fibrosis, inflammation and improved cardiac functional parameters (P, Q, R and S waves of the electrocardiogram). It is suggested that suramin may be a potential therapy for distrophinopaties, attenuating the dystrophic phenotype of the most affected cardiac and diaphragm muscles of the mdx mice, during later stages of the disease / Mestrado / Anatomia / Mestre em Biologia Celular e Estrutural

La dystrophie musculaire de Duchenne (DMD) est la conséquence de la perte de la dystrophine, protéine sous membranaire indispensable au maintien mécanique et fonctionnel du sarcolemme. Cette déficience augmenterait les influx cationiques par des microruptures de la membrane ou par la dérégulation de canaux tels que les canaux activés par l'étirement (SACs: Stretch-activated channel). Dans ce travail, les effets d'une stimulation mécanique ont été explorés sur des cardiomyocytes dans le contexte pathologique de la cardiomyopathie dilatée associée à la DMD. L'utilisation de fibres de carbone a permis de réaliser un étirement axial similaire aux conditions physiologiques de remplissage ventriculaire. Dans ces conditions, l'exploration de la topographie membranaire par la microscopie de conductance ionique à balayage n'a montré aucune évolution de la surface ni de lésion du sarcolemmel dans les conditions d'étirement. L'étude s'est donc focalisée sur l'activité de candidats moléculaires des SACs et plus particulièrement ceux appartenant à la famille des TRPs (Transient Receptor Potential) dans le dérèglement de l'homéostasie calcique induite par l'étirement. Les influx cationiques évalués par la technique d'extinction de fluorescence et l'étude de la concentration intracellulaire de Ca2+ ([Ca2+]i) grâce à la sonde Fluo8 montrent une implication des canaux TRPV2 et TRPCs. Les premiers semblent responsables d'une entrée cationique et d'une augmentation de [Ca2+]i importante dans les cardiomyocytes mdx. Les seconds, bien que responsables d'un influx, ne participeraient pas à l'augmentation de [Ca2+]i. Ces résultats révèlent que les canaux TRPV2 pourraient jouer un rôle important dans la dérégulation calcique observée dans les cardiomyocytes déficients en dystrophine. / Duchenne muscular dystrophy (DMD) is the consequence of the loss of dystrophin, a subsarcolemmal protein essential for mechanical and functional maintenances of the sarcolemma. This deficiency could increase cationic influxes by membrane microruptures or by dysregulation of channels such as stretch-activated channels (SACs). In this work, the effects of a mechanical stretch were explored on cardiomyocytes in the pathological context of dilated cardiomyopathy associated with DMD. Using carbon fibers, an homogenous axial stretch was performed to mimic physiological conditions of ventricular filling. In these conditions, exploration of membrane topography using the scanning ion conductance microscopy did not show any surface evolution or sarcolemma disruption in stretch condition. The study was thus focused on activity and identification of molecular candidates for SACs, especially the TRPs (Transient Receptor Potential) channels in the stretch-induced. Ca2+ homeostasis dysregulation. Cationic influxes assessed by Mn2+-quenching and assessment of the intracellular Ca2+ concentration ([Ca2+]i) using fluo-8 fluorescence demonstrated an involvement of TRPV2 and TRPCs channels. The first ones seem to be responsible for cationic entry and [Ca2+]i increase in mdx cardiomyocytes. The latter, though responsible for an influx, do not contribute to [Ca2+]i increase. These findings reveal that TRPV2 channels could play an important role in calcium dysregulation observed in dystrophin-deficient cardiomyocytes.

Orientadores: Maria Júlia Marques, Elaine Minatel / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-27T05:58:01Z (GMT). No. of bitstreams: 1 Perim_VivianePanegassi_M.pdf: 2625016 bytes, checksum: bb4c51a87dbe0dfa88e64cad10dda694 (MD5) Previous issue date: 2015 / Resumo: A Distrofia Muscular de Duchenne (DMD) é uma doença causada pela ausência da proteína distrofina e se caracteriza por degeneração muscular progressiva. A deficiência da distrofina na DMD e nos camundongos mdx, modelo experimental da DMD, promove mionecrose. O processo inflamatório que se instala exacerba a mionecrose e aumenta o estresse oxidativo. O estresse oxidativo tem sido proposto como um fator importante para a progressão da doença. As espécies reativas de oxigênio promovem danos nas fibras distróficas, comprometendo proteínas e lipídios da membrana, gerando grandes quantidades de lipofuscina e 4-HNE, indicadores de estresse oxidativo. Este trabalho tem como objetivo verificar se o ômega-3 diminui o estresse oxidativo em diferentes músculos distróficos (bíceps, diafragma e quadríceps) do camundongo mdx jovem. Observamos que o ômega-3 diminuiu a lipofuscina e o 4-HNE nos músculos estudados. A atividade das enzimas antioxidantes SOD, GPx e GR estava aparentemente diminuída no diafragma distrófico, quando comparado ao diafragma normal. No diafragma, o ômega-3 promoveu aumento discreto da atividade da SOD e da GPx. O músculo quadríceps não apresentou alterações significativas destas enzimas, tanto no mdx controle, quanto no mdx tratado com ômega-3. O ômega-3 promoveu melhora da distrofinopatia (redução da CK, diminuição da inflamação e aumento da regeneração muscular). Concluímos que o ômega-3 diminui o estresse oxidativo (reduz a lipofuscina e o 4-HNE), principalmente no músculo diafragma, provavelmente por este ser mais afetado que o quadríceps. A atividade aparentemente reduzida das enzimas antioxidantes no diafragma do mdx controle pode sugerir menor capacidade de tamponamento das espécies reativas de oxigênio neste músculo. Isto pode contribuir, pelo menos em parte, para o maior estresse oxidativo e maior acometimento do diafragma em relação ao quadríceps. Estes dados sugerem que o ômega-3 possa ter uma ação positiva em melhorar o estresse oxidativo em diferentes músculos distróficos, tornando-o potencialmente útil para a terapia da DMD / Abstract: Duchenne muscle dystrophy (DMD) is a disease caused by the absence of dystrophin characterized by progressive muscle degeneration. In DMD and in the mdx mice model of DMD, the inflammatory process exacerbates myonecrosis and increases oxidative stress. Oxidative stress has been proposed as an important factor in disease progression. Reactive oxygen species promote damage in dystrophic fibers, affecting proteins and lipids of the membrane, generating large amounts of lipofuscin and 4-HNE, markers of oxidative stress. This study aims to determine whether ômega-3 therapy reduces oxidative stress in different dystrophic muscles (biceps, diaphragm and quadriceps) of mdx mouse, at earlier stages of the disease. Ômega-3 decreased lipofuscin and 4-HNE in all the muscles studied. The activity of the antioxidant enzymes SOD, GPx and GR was apparently reduced in mdx diaphragm control as compared to normal mice. In the diaphragm, ômega-3 promoted a slight increase in the activity of SOD and GPx. The quadriceps muscle showed no significant changes in the activity of these enzymes in mdx control, and ômega-3 did not change this profile. Ômega-3 also ammeliorated dystrophinopathy (reduced CK, decreased inflammation and increased muscle regeneration). We conclude that ômega-3 reduces oxidative stress (by decreasing lipofuscin and 4-HNE), mainly in the dystrophic diaphragm, possibly because this muscle is more affected than the quadriceps. The apparent decreased activity of antioxidant enzymes in the mdx diaphragm may suggest a poor capacity of this muscle to buffer the reactive oxygen species. This may contribute, at least in part, to the increased oxidative stress in the diaphragm and to the fact that this muscle will turn out to be the more affected muscle in the mdx. The present results suggest that ômega-3 may have a positive effect in improving oxidative stress in different dystrophic muscles, making it potentially useful for DMD therapy / Mestrado / Biologia Celular / Mestra em Biologia Celular e Estrutural

La dystrophie musculaire de Duchenne (DMD) entraine une perte progressive de la force musculaire. L'objectif de ce présent travail est d'étudier la sensibilité d'une méthode acoustique échographique (50 MHz) et d'une méthode résonante (25 kHz) aux changements de propriétés des tissus musculaires de souris mdx modèles. Les paramètres mesurés sont l'atténuation ultrasonore pour la méthode échographique et le module complexe de cisaillement pour la méthode résonante. Dans ce manuscrit nous exposons le développement de ces deux méthodes adaptées à l'étude de deux tissus musculaires de souris : le diaphragme et la peau. La méthode échographique a permis de quantifier les changements de propriétés biologiques du diaphragme en fonction du pourcentage de zone non musculaire sur des souris âgées de 3 mois à 24 mois. La méthode résonante, génère un champ de pression dans le tissu induisant un cisaillement dans le tissu. Cette méthode a permis d'estimer des différences de propriétés mécaniques sur le diaphragme et sur la peau entre les tissus sains et tissu pathologiques. Les résultats obtenus autorisent à penser que le développement de la méthode résonante pour des applications in vivo chez l'Homme atteint de DMD est possible. / The muscular dystrophy of Duchenne (DMD) lead a progressive loss of the muscular strength. The objective of this present work is to study the sensibility of an ultrasound acoustic method (50 MHz) and a résonant method (25 kHz) to the changes of properties of muscle tissues of mdx mice models. The mesured parameters are the ultrasound attenuation for the echographic method and the complexe shear modulus for the résonant method.In this manuscript we explain the development of these two methods adapted to the study of two muscular tissues of mouse: the diaphragm and the skin. The ultrasound method allowed to quantify the changes of biological properties of the diaphragm according to the percentage of non muscular area on 3-month-old mice in 24 months. The résonant acoustic method, generates a field pressure in the tissue leading a shearing tissue. This method allowed to estimate différences of mechanical properties on the diaphragm and on the skin between healthy tissues and pathological tissues. We think the obtained results authorize the development of the resonant method for in vivo applications to human touched by DMD.

Duchenne Muscular Dystrophy (DMD) is an X-linked recessive neuromuscular disease characterized by progressive muscle-wasting and loss of mobility. One-third of patients with DMD are also affected by cognitive impairments such as a lower than average IQ and impaired working memory, comorbid with neuropsychiatric disorders such as anxiety and autism-related behaviours. DMD is caused by mutations in the DMD gene resulting in the deletion of the full-length dystrophin protein (Dp427) and, dependent on mutation, other dystrophin isoforms. These isoforms are predominantly found in the brain and deletion may impact on cognition. The most commonly used animal model to study DMD is the mdx mouse which completely lacks Dp427 but no other DMD isoforms. Although the muscle phenotype is well-established, behavioural characterization of the mdx mouse model has been inconclusive. In this thesis I investigated the hippocampal and amygdala cellular and behavioural phenotypes of the mdx mouse. I show that post-natal neural stem-like cell division in the SGZ is altered in the absence of Dp427 resulting in enhanced symmetric division. I show in vitro that primary mdx cultures are fewer and smaller than wild-type, consistent with an increase in symmetrical self-renewal whereas secondary cultures are fewer and larger, consistent with a shift in symmetric division producing transit-amplifying type 2a daughter cells. I next characterized the mdx mouse model using a battery of behavioural tests. Data presented here show that mdx mice do not exhibit an anxious phenotype, do not display autism-related behaviours, and do not display impairments in and spatial learning or memory. However, associative learning, as measured in the fear conditioning paradigm is enhanced in mdx mice. Lastly, I attempted to generate three different brain-specific dystrophin knock-out mouse models to examine role of other dystrophin isoforms. While none of the models were able to deplete dystrophin from brain, given the inverse relationship between Cre-mediated efficiency and the genetic distance of the loxP sites in the fDMDH mouse employed, I do provide important insight into the presence and absence of the muscle-specific enhancers in constructs commonly used to generate brain-specific mouse models. Taken together, this thesis provides converging evidence to indicate that loss of Dp427 impacts on fear associative learning and stem-cell like division in the SGZ but likely does not underlie the non-progressive cognitive impairments affecting one-third of all DMD patients.

The mdx mouse is widely used as a model for Duchenne Muscular Dystrophy, a fatal X-linked disease caused by a deficiency of the sub-sarcolemmal protein, dystrophin. This dissertation reports characterisation of the features of dystrophy in the mdx mouse, including parameters such as electrophysiological and contractile properties of dystrophic cardiac tissue, quantitative evaluation of kyphosis throughout the mdx lifespan, and contractile properties of respiratory and paraspinal muscles. Following these characterisation studies, the efficacy of antisense oligonucleotides (AOs) to induce alternative mRNA splicing in mdx skeletal muscles (diaphragm and paraspinal muscles) was evaluated. The left atria of younger (<6 weeks) and older (>15 months) mdx mice showed consistently lower basal forces and responsiveness to increased calcium, while action potential duration was significantly shorter in young mice (3 weeks) and older mice (9 and 12 months) (P<0.05). Cardiac fibrosis increased with age in mdx atria and ventricles and was elevated in young (6-8 weeks) and old (15 months) mdx compared to control mice (P<0.01). This study provided insights into DMD cardiomyopathy, and suggested that very young or old mdx mice provide the most useful models. Mdx mice show thoracolumbar kyphosis like boys with Duchenne Muscular Dystrophy. A novel radiographic index, the Kyphotic Index (KI), was developed and showed that mdx mice are significantly more kyphotic from 9 months of age, an effect maintained until 17 months (P<0.05). At 17 months, the paraspinal and respiratory muscles (latissimus dorsi, diaphragm and intercostal muscles) are significantly weaker and more fibrotic (P<0.05). Administration of AOs at four sites within the diaphragm at 4 and 5 months of age significantly increased twitch and tetanic forces compared to sham treated mdx (P<0.05). However, no difference in collagen was evident and dystrophin was not detected, possibly due to the low concentration of AO utilised. This study suggested that AOs can provide functional improvement in treated skeletal muscles. Monthly injections with AOs into the paraspinal muscles from 2 months to 18 months of age alleviated kyphosis, without significantly altering twitch and tetanic forces of latissimus dorsi, diaphragm and intercostal muscles. There was evidence of less fibrosis in diaphragm and latissimus dorsi muscles (P<0.05) and reduced central nucleation of the latissimus dorsi and intercostal muscles (P<0.05). Again, dystrophin was not detected by immunoblot. These studies indicate that very young and old mdx mice display previously uncharacterised dystrophic features, and are useful models for testing new therapies such as AOs. Low doses of AOs were shown to be safe and efficacious for long-term use, however there remains a need for testing higher concentrations and improved delivery strategies.

La myopathie de Duchenne se caractérise principalement par une forte dégénérescence musculaire, due à l'absence de la dystrophine. La fonction de la dystrophine et les causes de la dégénérescence musculaire qui survient en son absence ne sont pas connues. <br />J'ai combiné des études chez les modèles animaux Cænorhabditis elegans et souris de cette maladie, afin d'essayer d'élucider les mécanismes de la dégénérescence musculaire.<br />Nous avons montré que le canal potassium SLO-1 et l'homologue de la syntrophine, STN-1, sont fonctionnellement reliés à l‘homologue de la dystrophine de C. elegans, DYS-1. Nous avons entrepris le crible du génome entier de C. elegans à la recherche de gènes supprimant la dégénérescence musculaire. Au cours de ce crible, nous avons montré que la voie de la dégradation protéique ainsi que plusieurs protéines kinases sont impliqués dans la dégénérescence musculaire. En parallèle, j'ai participé à la recherche de molécules actives sur la dégénérescence musculaire de C. elegans, puis chez la souris mdx. Nous avons notamment confirmé chez la souris mdx l'effet bénéfique de l'activation de la voie sérotoninergique.