Immunization with plasmids encoding M2 acetylcholine muscarinic receptor epitopes impairs cardiac function in mice and induces autophagy in the myocardium

Autoantibodies against the M2 subtype of muscarinic acetylcholine receptors with functional activities have been found in the sera of patients with dilated cardiomyopathy (DCM), and the second extracellular loop has been established as the predominant epitope. However, it has been shown that the third intracellular loop is recognized by Chagas disease patients with severe cardiac dysfunction. In this work, BALB/c mice were immunized with plasmids encoding these two epitopes, and a control group received the empty plasmid (pcDNA3 vector). Serum from these DNA-immunized animals had elevated and persistent titres of antibodies against respective antigens. Heart echocardiography indicated diminished left ventricular wall thickness and reduced ejection fraction for both epitope-immunized groups, and ergospirometry tests showed a significant decrease in the exercise time and oxygen consumption. Transfer of serum from these immunized mice into naïve recipients induced the same alterations in cardiac structure and function. Furthermore, electron microscopy analysis of donor-immunized animals revealed several ultrastructural alterations suggestive of autophagy and mitophagy, suggesting novel roles for these autoantibodies. Overall, greater functional and structural impairment was observed in the donor and recipient epitope groups, implicating the third intracellular loop epitope in the pathological effects for the first-time. Therefore, the corresponding peptides could be useful for autoimmune DCM diagnosis and targeted therapy

Cellular cardiomyoplasty in large myocardial infarction: Can the beneficial effect be enhanced by ACE‐inhibitor therapy?

Background: Cellular cardiomyoplasty with bone marrow derived stromal (MSC) and mononuclear (BMNC) cells has been shown to improve performance of infarcted hearts. We performed a comparative study with MSC and BMNC and tested the hypothesis that captopril treatment could enhance the beneficial effect of cell therapy in large myocardial infarctions. Methods Male syngeneic Wistar rats underwent experimental infarction and were randomized to receive 1–3×106 MSC, 108 BMNC or vehicle (BSS group). Two additional groups were treated with captopril and received 1–3×106 MSC (Cap.MSC) or vehicle (Cap). Results: The ejection fraction (EF%) of MSC and BMNC‐treated rats was higher than in the BSS rats, eight weeks after transplantation (33.0±4.0, 34.0±2.0 and 20.0±2.0% respectively, P<0.01). Both captopril‐treated groups improved EF% similarly. But only captopril plus MSC treatment almost restored cardiac function to control levels, 8 weeks after injection (60.50±5.40% vs. 41.00±4.50% in Cap.MSC and Cap respectively, P<0.05). Many DAPI‐labelled cells were found in the scar tissue of the left ventricle only in the Cap.MSC group. Conclusions: Cell transplantation with both MSC and BMNC produced a similar stabilisation of heart function, but the success of the cell engraftment and the recovery of cardiac performance were dependent on concomitant treatment with captopril

Time course of echocardiographic and electrocardiographic parameters in myocardial infarct in rats

In animal models the evaluation of myocardial infarct size in vivo and its relation to the actual lesion found post mortem is still a challenge. The purpose of the current study was to address if the conventional electrocardiogram (ECG) and/or echocardiogram (ECHO) could be used to adequately predict the size of the infarct in rats. Wistar rats were infarcted by left coronary ligation and then ECG, ECHO and histopathology were performed at 1, 7 and 28 days after surgery. Correlation between infarct size by histology and Q wave amplitude in lead L1 was only found when ECGs were performed one day post-surgery. Left ventricular diastolic and systolic dimensions correlated with infarct size by ECHO on day 7 post-infarction. On days 7 and 28 post-infarction, ejection indexes estimated by M-mode also correlated with infarct size. In summary we show that conventional ECG and ECHO methods can be used to estimate infarct size in rats. Our data suggest that the 7-day interval is actually the most accurate for estimation of infarct size by ECHO.<br>Nos modelos animais a medida do tamanho do infarto do miocárdio "in vivo" e sua relação com o tamanho da lesão encontrada no exame "pos-mortem" ainda é um desafio. A finalidade do presente estudo é verificar se um eletro (ECG) e ecocardiograma (ECO) rotineiros poderiam ser utilizados para predizer a extensão do infarto em ratos. Ratos Wistar foram infartados pela ligadura cirúrgica da artéria coronária descendente anterior e exames eletro, ecocardiográficos e histopatológicos foram realizados 1, 7 e 28 dias pós-infarto. Foi encontrada correlação entre o tamanho do infarto medido pela histopatologia e a amplitude da onda Q em D1 apenas nos ECGs realizados no primeiro dia após a cirurgia. Os diâmetros da cavidade ventricular esquerda medidos em sístole e em diástole pelo ECO correlacionaram-se com o tamanho do infarto no sétimo dia pós-infarto. Ainda mais, no sétimo e vigésimo oitavo dias pós-cirurgia, os índices sistólicos estimados pelo Modo M também se correlacionaram com o tamanho do infarto. Em resumo, nós mostramos que um ECG e ECO convencionais são capazes de estimar a extensão do infarto do miocárdio em ratos. Nossos dados sugerem que o tempo mais adequado para estimar o tamanho do infarto pelo ECO é 7 dias pós-cirurgia