Nonstimulated cardiomyoplasty improves hemodynamics in myocardial-infarcted rats

Impact of myocardial infarction on cardiac autonomic function in diabetic rats

AIMS

We evaluated autonomic and hemodynamic parameters and maximal oxygen consumption (VO(2)max) as possible determinants of mortality in streptozotocin (STZ) diabetic rats after myocardial infarction (MI).

METHOD

Male Wistar rats were divided into (n=8 of each): control sham (CS), diabetes sham (DS), MI (I), and diabetes+MI (DI). MI was induced 15 days after STZ induction. VO(2)max was measured at 3 (basal), 30, 60, and 91 days after MI. Hemodynamic and autonomic parameters were evaluated 92 days after MI.

RESULTS

MI area was similar in infarcted groups (~44%). Mortality rate increased in the DI (70%) compared with I (53%) group. Cardiopulmonary baroreflex, sympathetic (48%) and vagal (33%) tonus, low frequency (LF) band (57%), and LF/high frequency (HF) band ratio (53%) were reduced in DI compared with I animals. Furthermore, cardiac output (CO), peripheral vascular resistance (PVR) impairment, and VO(2)max reductions were observed in the DI compared with the I group.

CONCLUSIONS

Our data suggest that the CO and PVR changes as well as VO(2)max reduction were probably associated with additional cardiac autonomic control impairment, and, consequently, increased mortality rate in diabetic rats after a chronic myocardial infarction.

In situ delivery of bone marrow cells and mesenchymal stem cells improves cardiovascular function in hypertensive rats submitted to myocardial infarction

This work aimed to evaluate cardiac morphology/function and histological changes induced by bone marrow cells (BMCs) and cultured mesenchymal stem cells (MSCs) injected at the myocardium of spontaneously hypertensive rats (SHR) submitted to surgical coronary occlusion. Female syngeneic adult SHR, submitted (MI) or not (C) to coronary occlusion, were treated 24 h later with in situ injections of normal medium (NM), or with MSCs (MSC) or BMCs (BM) from male rats. The animals were evaluated after 1 and 30 days by echocardiography, histology of heart sections and PCR for the Y chromosome. Improved ejection fraction and reduced left ventricle infarcted area were observed in MSC rats as compared to the other experimental groups. Treated groups had significantly reduced lesion tissue score, increased capillary density and normal (not-atrophied) myocytes, as compared to NM and C groups. The survival rate was higher in C, NM and MSC groups as compared to MI and BM groups. In situ injection of both MSCs and BMCs resulted in improved cardiac morphology, in a more physiological model of myocardial infarction represented by surgical coronary occlusion of spontaneously hypertensive rats. Only treatment with MSCs, however, ameliorated left ventricle dysfunction, suggesting a positive role of these cells in heart remodeling in infarcted hypertensive subjects.

Systemic delivery of adult stem cells improves cardiac function in spontaneously hypertensive rats

1. Heart regeneration after myocardial infarction (MI) can occur after cell therapy, but the mechanisms, cell types and delivery methods responsible for this improvement are still under investigation. In the present study, we evaluated the impact of systemic delivery of bone marrow cells (BMC) and cultivated mesenchymal stem cells (MSC) on cardiac morphology, function and mortality in spontaneously hypertensive rats (SHR) submitted to coronary occlusion. 2. Female syngeneic adult SHR, submitted or not (control group; C) to MI, were treated with intravenous injection of MSC (MI + MSC) or BMC (MI + BM) from male rats and evaluated after 1, 15 and 30 days by echocardiography. Systolic blood pressure (SBP), functional capacity, histology, mortality rate and polymerase chain reaction for the Y chromosome were also analysed. 3. Myocardial infarction induced a decrease in SBP and BMC, but not MSC, prevented this decrease. An improvement in functional capacity and ejection fraction (38 +/- 4, 39 +/- 3 and 58 +/- 2% for MI, MI + MSC and MI + BM, respectively; P < 0.05), as well as a reduction of the left ventricle infarcted area, were observed in rats from the MI + BM group compared with the other three groups. Treated animals had a significantly reduced lesion tissue score. The mortality rate in the C, MI + BM, MI + MSC and MI groups was 0, 0, 16.7 and 44.4%, respectively (P < 0.05 for the MI + MSC and MI groups compared with the C and MI + BM groups). 4. The results of the present study suggest that systemic administration of BMC can improve left ventricular function, functional capacity and, consequently, reduce mortality in an animal model of MI associated with hypertension. We speculate that the cells transiently home to the myocardium, releasing paracrine factors that recruit host cells to repair the lesion.

Infarto do miocárdio experimental e aumento do estresse oxidativo em diafragma de ratos

OBJETIVO: Este é um estudo experimental que visa a avaliar o efeito da insuficiência cardíaca no estresse oxidativo em diafragma de ratos. MÉTODOS: O modelo de infarto do miocárdio por ligadura da artéria coronária esquerda foi utilizado para desenvolvimento de insuficiência cardíaca. No 42º dia após a ligadura coronária, os animais foram mortos e tiveram o diafragma retirado e homogeneizado. O estresse oxidativo foi avaliado em homogeneizados de diafragma através de medidas de lipoperoxidação e de ensaios de atividade enzimática antioxidante: catalase, glutationa peroxidase (enzimas que reduzem o peróxido de hidrogênio à água) e superóxido dismutase (enzima antioxidante que reduz o superóxido a peróxido de hidrogênio). RESULTADOS: Os resultados encontrados foram os seguintes: o modelo de ligadura de artéria coronária esquerda foi efetivo em gerar insuficiência cardíaca, com área média de infarto de 39% da área do ventrículo esquerdo; a lipoperoxidação estava 217% aumentada no diafragma dos animais infartados em relação aos controles; a atividade antioxidante da catalase estava reduzida em 77% e a da glutationa peroxidase em 20%, em comparação com o grupo controle; o infarto não alterou a atividade enzimática da superóxido dismutase. CONCLUSÃO: Os resultados sugerem a presença de estresse oxidativo no músculo diafragmático em animais submetidos à ligadura da artéria coronária esquerda.

Passive ventricular constraint

Heart failure (HF) is a progressive degenerative and malignant syndrome with a large number of aetiologies including coronary artery disease, chronic hypertension, exposure to toxins, bacteria and viruses and in a significant percentage of HF patients, the causal mechanism is unclear. The HF trail of morbidity and mortality is well documented and is characterised by step-like periods of relative symptomatic stability, compensation, separated by decompensatory episodes. The homeostatic response to the decline in cardiac function is diverse and involves most organs. There is an increase in resting rate, intra-cardiac hormone production (catecholamines, aldosterone, etc.) and in particular structural changes occur with increased mass and dilatation (dilated cardiomyopathy, DCM). DCM is associated with decreased cardiac output, contractility and energy efficiency and an increase in pro-arrhythmia and conduction defects. Kass et al. (Circulation 91(9) (1995) 2314) first demonstrated in patients who had undergone a dynamic cardio-myoplasty procedure, that, preventing further dilatation in DCM was beneficial and that the improved cardiovascular status was largely independent of muscle stimulation. We hypothesised that this outcome could be achieved by implanting a fabric cardiac support device around both ventricles to the AV junction. Subsequently, it was shown by us and others (Kass et al., 1995) (Cardiovasc. Res. 44(3) (1999) 549); (Ann. Thorac. Surg. 70(4) (2000) 1275) (in different animal models of DCM) that passive ventricular constraint prevented further dilatation, initiated left ventricular volume reduction and reversed the decline in ejection fraction, mitral valve integrity and left ventricular contractility, when compared with untreated controls. Subsequent European and North American clinical trials in patients with DCM of varying aetiologies have shown equal promise and an absence of device related complications (Circulation 104(12 Suppl. 1) (2001) I270); (Ann. Thorac. Cardiovasc. Surg. 7(5) (2001) 278). The mechanisms behind this improvement have yet to be fully clarified however the support generated by the device upon the right and ventricular freewall would lower wall tension. Not only is passive ventricular constraint a very promising treatment modality for heart failure and DCM it should provide a useful research tool for the study of the role of ventricular dilatation in the progression of heart failure.