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Introdução: A cardiomiopatia hipertrófica (CH) é uma doença genética cardíaca primária, caracterizada por hipertrofia do ventrículo esquerdo, sem dilatação, geralmente assimétrica e predominantemente septal, com prevalência estimada em 1:500. Atualmente já foram descobertos 20 genes associados à doença, mas os genes mais frequentemente relacionados são o da Cadeia Pesada da ?-miosina (MYH7), Proteína C de Ligação da Miosina (MYBPC3) e Troponina T (TNNT2). O diagnóstico molecular dos pacientes é importante e custo-efetivo do ponto de vista de saúde pública, além de recomendado pela Sociedade Europeia de Cardiologia. Entretanto, o custo inicial do exame é muito alto, de forma que estudos tentam reduzir esse custo. Uma das propostas descritas utilizou o RNA extraído de leucócitos para sequenciamento com sucesso para o gene MYBPC3. Este trabalho tem como objetivo testar a metodologia de sequenciamento de RNA em larga escala e testar a aplicabilidade da mesma para os genes MYH7 e TNNT2, estimar as principais mutações envolvidas nos pacientes do estudo e estabelecer correlações entre os diferentes genótipos avaliados e os fenótipos dos grupos familiares portadores da doença. Métodos: Os sujeitos incluídos no estudo são portadores de cardiomiopatia hipertrófica nos quais foi feita uma coleta de sangue para extração de DNA e RNA. Foi utilizada nested PCR para amplificação do cDNA e PCR convencional para amplificação de DNA e posterior sequenciamento em sequenciador automático. As análises estatísticas dos dados clínicos foram realizadas utilizando-se ANOVA para comparação de médias e teste exato de Fisher para comparação de frequências. Resultados: O sequenciamento de RNA se mostrou problemático, com baixa taxa de amplificação, falsos positivos e possíveis falsos negativos, de forma que optou-se por utilizar o sequenciamento de DNA para identificação das alterações. Dos 268 pacientes estudados foi identificada uma mutação em 131 deles (48,8%). Das mutações encontradas, 78 (59,5%) estavam no gene MYH7, 50 (38,2%) no gene MYBPC3 e 3 (2,3%) no gene TNNT2. Foram identificadas 69 mutações diferentes, 24 delas ainda não descritas. Pacientes com mutação identificada possuíam em média idade de diagnóstico e idade atual menores, maior frequência cardíaca média e maior frequência de pacientes com taquicardia ventricular não sustentada quando comparados ao grupo sem mutação identificada. Pacientes com mutação no gene MYH7 possuíam maior tamanho de átrio esquerdo, maior frequência de fibrilação atrial e maior frequência de histórico familiar da doença do que pacientes com mutação em MYBPC3. Conclusões: A técnica sequenciamento de RNA extraído de leucócitos não é adequada para uma rotina de rastreamento em larga escala para CH devido à alta frequência de falsos positivos, possibilidade de falsos negativos e baixa taxa de amplificação, mas o sequenciamento de DNA, embora trabalhoso, se mostrou muito sensível para a análise. A identificação de uma mutação específica ainda não pode ser usada para prognóstico de gravidade da CH, mas as comparações de genótipo e fenótipo mostraram algumas relações interessantes que devem ser melhor avaliadas nos pacientes. Este é o primeiro trabalho a caracterizar a epidemiologia molecular da CH em pacientes brasileiros para os genes MYH7, MYBPC3 e TNNT2 / Introduction: Hypertrophic cardiomyopathy (HC) is a primary genetic cardiac disease characterized by left ventricular hypertrophy without dilation, usually asymmetric and predominantly septal, with an estimated prevalence of 1:500. There are 20 genes associated to the HC, but the ones more often related to the disease are ?-myosin heavy chain (MYH7), myosin binding protein C (MYBPC3) and troponin T (TNNT2). The molecular diagnosis of patients is important and cost-effective from the standpoint of public health, and recommended by the European Society of Cardiology. However, the initial cost of the exam is very high, so several studies are attempting to reduce it. One of the proposals described used the RNA extracted from leukocytes for sequencing successfully to the MYBPC3 gene. The present study aims to test the methodology for large-scale sequencing and test it\'s applicability to the MYH7 and TNNT2 genes, to estimate the main mutations involved in the studied patients and establish correlations between their genotypes and phenotypes. Methods: The subjects included in the study were patients previously diagnosed with hypertrophic cardiomyopathy in whom a blood sample was collected to DNA and RNA extraction. It was used nested PCR for cDNA amplification and conventional PCR for DNA amplification for posterior sequencing on an automatic sequencer. Statistical analyzes of clinical data were performed using ANOVA to compare means and Fisher\'s exact test for frequencies comparison. Results: The RNA sequencing was problematic with low rate of amplification, false positives and possible false negatives, so was used DNA sequencing to identify the mutations. Of the 268 patients studied a mutation was identified in 131 of them (48.8%). Among the mutations found, 78 (59.5%) were in the MYH7 gene, 50 (38.2%) in the MYBPC3 gene and three (2.3%) in the TNNT2 gene. We have identified 69 different mutations, 24 of them not yet described. Patients with an identified mutation had an average smaller age of diagnosis and current age, higher average cardiac frequency and higher frequency of patients with nonsustained ventricular tachycardia compared to those without an identified mutation. Patients with mutations in the MYH7 gene had larger left atrium size, higher frequency of atrial fibrillation and higher frequency of family history of the disease than patients with a mutation in the MYBPC3 gene. Conclusions: The technique of sequencing RNA extracted from leucocytes is not suitable for large scale routine screening for CH due to the high frequency of false positives, possibility of false negatives and low rate of amplification, but the DNA sequencing, though laborious, was very sensitive to the analysis. Identification of a specific mutation cannot yet be used for prognosis of the disease\'s severity, but comparisons of genotype and phenotype have shown some interesting relationships that should be further evaluated. The presente study is the first one to characterize the molecular epidemiology of hypertrophic cardiomyopathy in Brazilian patients for those three more important genes mentioned above

Introdução: A cardiomiopatia hipertrófica (CH) é uma doença genética cardíaca primária, caracterizada por hipertrofia do ventrículo esquerdo, sem dilatação, geralmente assimétrica e predominantemente septal, com prevalência estimada em 1:500. Atualmente já foram descobertos 20 genes associados à doença, mas os genes mais frequentemente relacionados são o da Cadeia Pesada da ?-miosina (MYH7), Proteína C de Ligação da Miosina (MYBPC3) e Troponina T (TNNT2). O diagnóstico molecular dos pacientes é importante e custo-efetivo do ponto de vista de saúde pública, além de recomendado pela Sociedade Europeia de Cardiologia. Entretanto, o custo inicial do exame é muito alto, de forma que estudos tentam reduzir esse custo. Uma das propostas descritas utilizou o RNA extraído de leucócitos para sequenciamento com sucesso para o gene MYBPC3. Este trabalho tem como objetivo testar a metodologia de sequenciamento de RNA em larga escala e testar a aplicabilidade da mesma para os genes MYH7 e TNNT2, estimar as principais mutações envolvidas nos pacientes do estudo e estabelecer correlações entre os diferentes genótipos avaliados e os fenótipos dos grupos familiares portadores da doença. Métodos: Os sujeitos incluídos no estudo são portadores de cardiomiopatia hipertrófica nos quais foi feita uma coleta de sangue para extração de DNA e RNA. Foi utilizada nested PCR para amplificação do cDNA e PCR convencional para amplificação de DNA e posterior sequenciamento em sequenciador automático. As análises estatísticas dos dados clínicos foram realizadas utilizando-se ANOVA para comparação de médias e teste exato de Fisher para comparação de frequências. Resultados: O sequenciamento de RNA se mostrou problemático, com baixa taxa de amplificação, falsos positivos e possíveis falsos negativos, de forma que optou-se por utilizar o sequenciamento de DNA para identificação das alterações. Dos 268 pacientes estudados foi identificada uma mutação em 131 deles (48,8%). Das mutações encontradas, 78 (59,5%) estavam no gene MYH7, 50 (38,2%) no gene MYBPC3 e 3 (2,3%) no gene TNNT2. Foram identificadas 69 mutações diferentes, 24 delas ainda não descritas. Pacientes com mutação identificada possuíam em média idade de diagnóstico e idade atual menores, maior frequência cardíaca média e maior frequência de pacientes com taquicardia ventricular não sustentada quando comparados ao grupo sem mutação identificada. Pacientes com mutação no gene MYH7 possuíam maior tamanho de átrio esquerdo, maior frequência de fibrilação atrial e maior frequência de histórico familiar da doença do que pacientes com mutação em MYBPC3. Conclusões: A técnica sequenciamento de RNA extraído de leucócitos não é adequada para uma rotina de rastreamento em larga escala para CH devido à alta frequência de falsos positivos, possibilidade de falsos negativos e baixa taxa de amplificação, mas o sequenciamento de DNA, embora trabalhoso, se mostrou muito sensível para a análise. A identificação de uma mutação específica ainda não pode ser usada para prognóstico de gravidade da CH, mas as comparações de genótipo e fenótipo mostraram algumas relações interessantes que devem ser melhor avaliadas nos pacientes. Este é o primeiro trabalho a caracterizar a epidemiologia molecular da CH em pacientes brasileiros para os genes MYH7, MYBPC3 e TNNT2 / Introduction: Hypertrophic cardiomyopathy (HC) is a primary genetic cardiac disease characterized by left ventricular hypertrophy without dilation, usually asymmetric and predominantly septal, with an estimated prevalence of 1:500. There are 20 genes associated to the HC, but the ones more often related to the disease are ?-myosin heavy chain (MYH7), myosin binding protein C (MYBPC3) and troponin T (TNNT2). The molecular diagnosis of patients is important and cost-effective from the standpoint of public health, and recommended by the European Society of Cardiology. However, the initial cost of the exam is very high, so several studies are attempting to reduce it. One of the proposals described used the RNA extracted from leukocytes for sequencing successfully to the MYBPC3 gene. The present study aims to test the methodology for large-scale sequencing and test it\'s applicability to the MYH7 and TNNT2 genes, to estimate the main mutations involved in the studied patients and establish correlations between their genotypes and phenotypes. Methods: The subjects included in the study were patients previously diagnosed with hypertrophic cardiomyopathy in whom a blood sample was collected to DNA and RNA extraction. It was used nested PCR for cDNA amplification and conventional PCR for DNA amplification for posterior sequencing on an automatic sequencer. Statistical analyzes of clinical data were performed using ANOVA to compare means and Fisher\'s exact test for frequencies comparison. Results: The RNA sequencing was problematic with low rate of amplification, false positives and possible false negatives, so was used DNA sequencing to identify the mutations. Of the 268 patients studied a mutation was identified in 131 of them (48.8%). Among the mutations found, 78 (59.5%) were in the MYH7 gene, 50 (38.2%) in the MYBPC3 gene and three (2.3%) in the TNNT2 gene. We have identified 69 different mutations, 24 of them not yet described. Patients with an identified mutation had an average smaller age of diagnosis and current age, higher average cardiac frequency and higher frequency of patients with nonsustained ventricular tachycardia compared to those without an identified mutation. Patients with mutations in the MYH7 gene had larger left atrium size, higher frequency of atrial fibrillation and higher frequency of family history of the disease than patients with a mutation in the MYBPC3 gene. Conclusions: The technique of sequencing RNA extracted from leucocytes is not suitable for large scale routine screening for CH due to the high frequency of false positives, possibility of false negatives and low rate of amplification, but the DNA sequencing, though laborious, was very sensitive to the analysis. Identification of a specific mutation cannot yet be used for prognosis of the disease\'s severity, but comparisons of genotype and phenotype have shown some interesting relationships that should be further evaluated. The presente study is the first one to characterize the molecular epidemiology of hypertrophic cardiomyopathy in Brazilian patients for those three more important genes mentioned above

Cardiovascular diseases are among the leading causes of death worldwide and particularly in the developed World. The search for new therapeutic approaches for improving the functions of the damaged heart is therefore a critical endeavour. Myocardial infarction, which can lead to heart failure, is associated with irreversible loss of functional cardiomyocytes. The loss of cardiomyocytes poses a major difficulty for treating the damaged heart since terminally differentiated cardiomyocytes have very limited regeneration potential. Currently, the only effective treatment for severe heart failure is heart transplantation but this option is limited by the acute shortage of donor hearts. The high incidence of heart diseases and the scarcity donor hearts underline the urgent need to find alternative therapeutic approaches for treating cardiovascular diseases. Pluripotent embryonic stem (ES) cells can differentiate into functional cardiomyocytes. Therefore the engraftment of ES cell-derived functional cardiomyocytes or cardiac progenitor cells into the damaged heart to regenerate healthy myocardial tissues may be used to treat damaged hearts. Stem cell-based therapy therefore holds a great potential as a very attractive alternative to heart transplant for treating heart failure and other cardiovascular diseases. A major obstacle to the realisation of stem cell-based therapy is the lack of donor cells and this in turn is due to the fact that, currently, the molecular mechanisms or the regulatory signal transduction mechanisms that are responsible for mediating ES cell differentiation into cardiomyocytes are not well understood. Overcoming this huge scientific challenge is absolutely necessary before the use of stem cell-derived cardiomyocytes to treat the damaged heart can become a reality. Therefore the aim of this thesis was to investigate the signal transduction pathways that are involved in the differentiation of stem cells into cardiomyocytes. The first objective was the establishment and use of cardiomyocyte differentiation models using H9c2 cells and P19 stem cells to accomplish the specific objectives of the thesis. The specific objectives of the thesis were, the investigation of the roles of (i) nitric oxide (ii) protein kinase C (PKC), (iii) p38 mitogen-activated protein kinase (p38 MAPK) (vi) phosphoinositide 3-kinase (PI3K) and (vi) nuclear factor-kappa B (NF-kB) signalling pathways in the differentiation of stem cells to cardiomyocytes and, more importantly, to identify where possible any points of convergence and potential cross-talk between pathways that may be critical for differentiation to occur. P19 cells were routinely cultured in alpha minimal essential medium (α-MEM) supplemented with 100 units/ml penicillin /100 μg/ml streptomycin and 10% foetal bovine serum (FBS). P19 cell differentiation was initiated by culturing the cells in microbiological plates in medium containing 0.8 % DMSO to form embryoid bodies (EB). This was followed by transfer of EBs to cell culture grade dishes after four days. H9c2 cells were cultured in Dulbecco’s Modified Eagle’s medium (DMEM) supplemented with 10% FBS. Differentiation was initiated by incubating the cells in medium containing 1% FBS. In both models, when drugs were employed, they were added to cells for one hour prior to initiating differentiation. Cell monolayers were monitored daily over a period of 12 or 14 days. H9c2 cells were monitored for morphological changes and P19 cells were monitored for beating cardiomyocytes. Lysates were generated in parallel for western blot analysis of changes in cardiac myosin heavy chain (MHC), ventricular myosin chain light chain 1(MLC-1v) or troponin I (cTnI) using specific monoclonal antibodies. H9c2 cells cultured in 1% serum underwent differentiation as shown by the timedependent formation of myotubes, accompanied by a parallel increase in expression of both MHC and MLC-1v. These changes were however not apparent until 4 to 6 days after growth arrest and increased with time, reaching a peak at day 12 to 14. P19 stem cells cultured in DMSO containing medium differentiated as shown by the timedependent appearance of beating cardiomyocytes and this was accompanied by the expression of cTnI. The differentiation of both P19 stem cells and H9c2 into cardiomyocytes was blocked by the PI3K inhibitor LY294002, PKC inhibitor BIM-I and the p38 MAPK inhibitor SB2035800. However when LY294002, BIM-I or SB2035800 were added after the initiation of DMSO-induced P19 stem cell differentiation, each inhibitor failed to block the cell differentiation into beating cardiomyocytes. The NF-kB activation inhibitor, CAPE, blocked H9c2 cell differentiation into cardiomyocytes. Fast nitric oxide releasing donors (SIN-1 and NOC-5) markedly delayed the onset of differentiation of H9c2 cells into cardiomyocytes while slow nitric oxide releasing donors (SNAP and NOC-18) were less effective in delaying the onset of differentiation or long term differentiation of H9c2 cells into cardiomyocytes. Akt (protein kinase B) is the key downstream target of PI3K. Our cross-talk data also showed that PKC inhibition and p38 MAPK inhibition respectively enhanced and reduced the activation of Akt, as determined by the phosphorylation of Akt at serine residue 473. In conclusion, PKC, PI3K, p38 MAPK and NF-kB are relevant for the differentiation of stem cells into cardiomyocytes. Our data also show that the PKC, PI3K and p38 MAPK signalling pathways are activated as very early events during the differentiation of stem cells into cardiomyocytes. Our data also suggest that PKC may negatively regulate Akt activation while p38 MAPK inhibition inhibits Akt activation. Our fast NO releasing donor data suggest that nitric oxide may negatively regulate H9c2 cell differentiation.