Influência da via mTOR no processo de remodelação cardíaca induzida pelo ácido retinóico

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Absence of Interferon-γ–Inducible Gene IGTP Does Not Significantly Alter the Development of Chagasic Cardiomyopathy in Mice Infected with Trypanosoma cruzi (Brazil Strain)

Interferon-γ (IFN-γ) contributes to host resistance during acute infection with Trypanosoma cruzi, the causative agent of Chagas’ disease. Inducibly expressed guanosine triphosphatase (IGTP), a 48-kDa guanosine triphosphatase (GTPase), is a member of a family of GTPase proteins inducibly expressed by IFN-γ. The expression pattern of IGTP suggests that it may mediate IFN-γ–induced responses in a variety of cell types. IGTP has been demonstrated to be important for control of Toxoplasma gondii infection but not for resistance against Listeria monocytogenes. We evaluated the role of IGTP in development of chronic chagasic cardiomyopathy in IGTP null mice and C57X129sv (wild type [WT]) mice infected with the Brazil strain for 6 mo. There was no significant difference in parasitemia or cardiac histopathology between null and WT mice. Right ventricular remodeling was observed in infected IGTP null mice, suggesting that IGTP does not significantly alter the course of T. cruzi infection.

Influência da via mTOR no processo de remodelação cardíaca induzida pelo ácido retinóico

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Remodelamento miocárdico após grandes infartos converte potenciação pós-pausa em decaimento da força em ratos

FUNDAMENTO: A Contração Pós-Repouso (CPR) do músculo cardíaco fornece informações indiretas sobre a manipulação de cálcio intracelular. OBJETIVO: Nosso objetivo foi estudar o comportamento da CPR e seus mecanismos subjacentes em camundongos com infarto do miocárdio. MÉTODOS: Seis semanas após a oclusão coronariana, a contratilidade dos Músculos Papilares (MP) obtidos a partir de camundongos submetidos à cirurgia sham (C, n = 17), com infarto moderado (MMI, n = 10) e grande infarto (LMI, n = 14), foi avaliada após intervalos de repouso de 10 a 60 segundos antes e depois da incubação com cloreto de lítio (Li+) em substituição ao cloreto de sódio ou rianodina (Ry). A expressão proteica de SR Ca(2+)-ATPase (SERCA2), trocador Na+/Ca2+ (NCX), fosfolambam (PLB) e fosfo-Ser (16)-PLB foi analisada por Western blotting. RESULTADOS: Os camundongos MMI apresentaram potenciação de CPR reduzida em comparação aos camundongos C. Em oposição à potenciação normal para camundongos C, foram observadas degradações de força pós-repouso nos músculos de camundongos LMI. Além disso, a Ry bloqueou a degradação ou potenciação de PRC observada em camundongos LMI e C; o Li+ inibiu o NCX e converteu a degradação em potenciação de CPR em camundongos LMI. Embora os camundongos MMI e LMI tenham apresentado diminuição no SERCA2 (72 ± 7% e 47 ± 9% de camundongos controle, respectivamente) e expressão protéica de fosfo-Ser16-PLB (75 ± 5% e 46 ± 11%, respectivamente), a superexpressão do NCX (175 ± 20%) só foi observada nos músculos de camundongos LMI. CONCLUSÃO: Nossos resultados mostraram, pela primeira vez, que a remodelação miocárdica pós-IAM em camundongos pode mudar a potenciação regular para degradação pós-repouso, afetando as proteínas de manipulação de Ca(2+) em miócitos.

Strategie di personalizzazione della terapia di resincronizzazione cardiaca

Solo il 60% dei candidati alla resincronizzazione cardiaca risponde in termini di rimodellamento ventricolare inverso che è il più forte predittore di riduzione della mortalità e delle ospedalizzazioni. Due cause possibili della mancata risposta sono la programmazione del dispositivo e i limiti dell’ approccio transvenoso. Nel corso degli anni di dottorato ho effettuato tre studi per ridurre il numero di non responder. Il primo studio valuta il ritardo interventricolare. Al fine di ottimizzare le risorse e fornire un reale beneficio per il paziente ho ricercato la presenza di predittori di ritardo interventricolare diverso dal simultaneo, impostato nella programmazione di base. L'unico predittore è risultato essere l’ intervallo QRS> 160 ms, quindi ho proposto una flow chart per ottimizzare solo i pazienti che avranno nella programmazione ottimale un intervallo interventricolare non simultaneo. Il secondo lavoro valuta la fissazione attiva del ventricolo sinistro con stent. I dislocamenti, la soglia alta di stimolazione del miocardio e la stimolazione del nervo frenico sono tre problematiche che limitano la stimolazione biventricolare. Abbiamo analizzato più di 200 angiografie per vedere le condizioni anatomiche predisponenti la dislocazione del catetere. Prospetticamente abbiamo deciso di utilizzare uno stent per fissare attivamente il catetere ventricolare sinistro in tutti i pazienti che presentavano le caratteristiche anatomiche favorenti la dislocazione. Non ci sono più state dislocazioni, c’è stata una migliore risposta in termini di rimodellamento ventricolare inverso e non ci sono state modifiche dei parametri elettrici del catetere. Il terzo lavoro ha valutato sicurezza ed efficacia della stimolazione endoventricolare sinistra. Abbiamo impiantato 26 pazienti giudicati non responder alla terapia di resincronizzazione cardiaca. La procedura è risultata sicura, il rischio di complicanze è simile alla stimolazione biventricolare classica, ed efficace nell’arrestare la disfunzione ventricolare sinistra e / o migliorare gli effetti clinici in un follow-up medio.

Transgenic system for conditional induction and rescue of chronic myocardial hibernation provides insights into genomic programs of hibernation

A key energy-saving adaptation to chronic hypoxia that enables cardiomyocytes to withstand severe ischemic insults is hibernation, i.e., a reversible arrest of contractile function. Whereas hibernating cardiomyocytes represent the critical reserve of dysfunctional cells that can be potentially rescued, a lack of a suitable animal model has hampered insights on this medically important condition. We developed a transgenic mouse system for conditional induction of long-term hibernation and a system to rescue hibernating cardiomyocytes at will. Via myocardium-specific induction (and, in turn, deinduction) of a VEGF-sequestering soluble receptor, we show that VEGF is indispensable for adjusting the coronary vasculature to match increased oxygen consumption and exploit this finding to generate a hypoperfused heart. Importantly, ensuing ischemia is tunable to a level at which large cohorts of cardiomyocytes are driven to enter a hibernation mode, without cardiac cell death. Relieving the VEGF blockade even months later resulted in rapid revascularization and full recovery of contractile function. Furthermore, we show that left ventricular remodeling associated with hibernation is also fully reversible. The unique opportunity to uncouple hibernation from other ischemic heart phenotypes (e.g., infarction) was used to determine the genetic program of hibernation; uncovering hypoxia-inducible factor target genes associated with metabolic adjustments and induced expression of several cardioprotective genes. Autophagy, specifically self-digestion of mitochondria, was identified as a key prosurvival mechanism in hibernating cardiomyocytes. This system may lend itself for examining the potential utility of treatments to rescue dysfunctional cardiomyocytes and reverse maladaptive remodeling.

The bovine dilated cardiomyopathy locus maps to a 1.0-Mb interval on chromosome 18

Cardiomyopathies are myocardial diseases that lead to cardiac dysfunction, heart failure, arrhythmia, and sudden death. In human medicine, cardiomyopathies frequently warrant heart transplantation in children and adults. Bovine dilated cardiomyopathy (BDCMP) is a heart muscle disorder that has been observed during the last 30 years in cattle of Holstein-Friesian origin. In Switzerland BDCMP affects Swiss Fleckvieh and Red Holstein breeds. BDCMP is characterized by a cardiac enlargement with ventricular remodeling and chamber dilatation. The common symptoms in affected animals are subacute subcutaneous edema, congestion of the jugular veins, and tachycardia with gallop rhythm. A cardiomegaly with dilatation and hypertrophy of all heart chambers, myocardial degeneration, and fibrosis are typical postmortem findings. It was shown that all BDCMP cases reported worldwide traced back to a red factor-carrying Holstein-Friesian bull, ABC Reflection Sovereign. An autosomal recessive mode of inheritance was proposed for BDCMP. Recently, the disease locus was mapped to a 6.7-Mb interval MSBDCMP06-BMS2785 on bovine Chr 18 (BTA18). In the present study the BDCMP locus was fine mapped by using a combined strategy of homozygosity mapping and association study. A BAC contig of 2.9 Mb encompassing the crucial interval was constructed to establish the correct marker order on BTA18. We show that the disease locus is located in a gene-rich interval of 1.0 Mb and is flanked by the microsatellite markers DIK3006 and MSBDCMP51.

Elevated cystatin C & heart failure prognosis a systematic review

Renal insufficiency is one of the most common co-morbidities present in heart failure (HF) patients. It has significant impact on mortality and adverse outcomes. Cystatin C has been shown as a promising marker of renal function. A systematic review of all the published studies evaluating the prognostic role of cystatin C in both acute and chronic HF was undertaken. A comprehensive literature search was conducted involving various terms of 'cystatin C' and 'heart failure' in Pubmed medline and Embase libraries using Scopus database. A total of twelve observational studies were selected in this review for detailed assessment. Six studies were performed in acute HF patients and six were performed in chronic HF patients. Cystatin C was used as a continuous variable, as quartiles/tertiles or as a categorical variable in these studies. Different mortality endpoints were reported in these studies. All twelve studies demonstrated a significant association of cystatin C with mortality. This association was found to be independent of other baseline risk factors that are known to impact HF outcomes. In both acute and chronic HF, cystatin C was not only a strong predictor of outcomes but also a better prognostic marker than creatinine and estimated glomerular filtration rate (eGFR). A combination of cystatin C with other biomarkers such as N terminal pro B- type natriuretic peptide (NT-proBNP) or creatinine also improved the risk stratification. The plausible mechanisms are renal dysfunction, inflammation or a direct effect of cystatin C on ventricular remodeling. Either alone or in combination, cystatin C is a better, accurate and a reliable biomarker for HF prognosis. ^

Efeitos da vitamina E associada a nanopartículas lipídicas no remodelamento cardíaco, em ratos infartados

Do ponto de vista clínico, o remodelamento ventricular está associado a um pior prognóstico. Pacientes com remodelamento já diagnosticado, ou com alto risco de desenvolvê-lo, devem ser tratados de forma intensiva, a fim de prevenir, atenuar ou mesmo reverter esse processo. O objetivo do presente estudo foi investigar os efeitos da vitamina E associada a nanopartículas lipídicas no remodelamento cardíaco, em ratos. Medidas ecocardiográficas foram determinadas 24 horas pós infarto e seis semanas após tratamento. Cortes teciduais do coração foram submetidos a coloração com Hematoxilina eosina e Picrosirius red. Duas regiões distintas do ventrículo esquerdo remotas ao infarto foram examinadas: subendocárdica e não subendocárdica. A extensão do infarto, o diâmetro dos miócitos, a fração de variação da área e o índice de expansão do ventrículo esquerdo foram determinados. No ecocardiograma observamos que os grupos infartados apresentaram um aumento no diâmetro diastólico e sistólico, uma diminuição da fração de encurtamento e da fração de variação da área quando comparados ao grupo controle. Na análise morfométrica, foi observado que nos animais infartados houve um aumento do diâmetro dos miócitos, da expansão do ventrículo esquerdo e da fração de volume do colágeno, principalmente na região subendocárdica, quando comparado ao grupo controle. A vitamina E associada a nanopartículas lipídicas, não apresentou efeitos protetores e nem atenuantes no remodelamento cardíaco nesse modelo experimental

Hypoxia-induced epigenetic modifications are associated with cardiac tissue fibrosis and the development of a myofibroblast-like phenotype

Ischemia caused by coronary artery disease and myocardial infarction leads to aberrant ventricular remodeling and cardiac fibrosis. This occurs partly through accumulation of gene expression changes in resident fibroblasts, resulting in an overactive fibrotic phenotype. Long-term adaptation to a hypoxic insult is likely to require significant modification of chromatin structure in order to maintain the fibrotic phenotype. Epigenetic changes may play an important role in modulating hypoxia-induced fibrosis within the heart. Therefore, the aim of the study was to investigate the potential pro-fibrotic impact of hypoxia on cardiac fibroblasts and determine whether alterations in DNA methylation could play a role in this process. This study found that within human cardiac tissue, the degree of hypoxia was associated with increased expression of collagen 1 and alpha-smooth muscle actin (ASMA). In addition, human cardiac fibroblast cells exposed to prolonged 1% hypoxia resulted in a pro-fibrotic state. These hypoxia-induced pro-fibrotic changes were associated with global DNA hypermethylation and increased expression of the DNA methyltransferase (DNMT) enzymes DNMT1 and DNMT3B. Expression of these methylating enzymes was shown to be regulated by hypoxia-inducible factor (HIF)-1α. Using siRNA to block DNMT3B expression significantly reduced collagen 1 and ASMA expression. In addition, application of the DNMT inhibitor 5-aza-2'-deoxycytidine suppressed the pro-fibrotic effects of TGFβ. Epigenetic modifications and changes in the epigenetic machinery identified in cardiac fibroblasts during prolonged hypoxia may contribute to the pro-fibrotic nature of the ischemic milieu. Targeting up-regulated expression of DNMTs in ischemic heart disease may prove to be a valuable therapeutic approach.

Can emerging biomarkers of myocardial remodelling identify asymptomatic hypertensive patients at risk for diastolic dysfunction and diastolic heart failure?

AIMS: Hypertension is one of the main drivers of the heart failure (HF) epidemic. The aims of this study were to profile fibro-inflammatory biomarkers across stages of the hypertensive heart disease (HHD) spectrum and to examine whether particular biochemical profiles in asymptomatic patients identify a higher risk of evolution to HF.

METHODS AND RESULTS: This was a cross-sectional observational study involving a population of 275 stable hypertensive patients divided into two different cohorts: Group 1, asymptomatic hypertension (AH) (n= 94); Group 2, HF with preserved ejection fraction (n= 181). Asymptomatic hypertension patients were further subdivided according to left atrial volume index ≥34 mL/m(2) (n= 30) and <34 mL/m(2) (n= 64). Study assays involved inflammatory markers [interleukin 6 (IL6), interleukin 8 (IL8), monocyte chemoattractant protein 1 (MCP1), and tumour necrosis factor α], collagen 1 and 3 metabolic markers [carboxy-terminal propeptide of collagen 1, amino-terminal propeptide of collagen 1, amino-terminal propeptide of collagen 3 (PIIINP), and carboxy-terminal telopeptide of collagen 1 (CITP)], extra-cellular matrix turnover markers [matrix metalloproteinase 2 (MMP2), matrix metalloproteinase 9 (MMP9), and tissue inhibitor of metalloproteinase 1 (TIMP1)], and the brain natriuretic peptide. Data were adjusted for age, sex, systolic blood pressure, and creatinine. Heart failure with preserved ejection fraction was associated with an increased inflammatory signal (IL6, IL8, and MCP1), an increased fibrotic signal (PIIINP and CITP), and an increased matrix turnover signal (MMP2 and MMP9). Alterations in MMP and TIMP enzymes were found to be significant indicators of greater degrees of asymptomatic left ventricular diastolic dysfunction.

CONCLUSION: These data define varying fibro-inflammatory profiles throughout different stages of HHD. In particular, the observations on MMP9 and TIMP1 raise the possibility of earlier detection of those at risk of evolution to HF which may help focus effective preventative strategies.

Enhanced engraftment and repairing ability of human adipose-derived stem cells, conveyed by pharmacologically active microcarriers continuously releasing HGF and IGF-1, in healing myocardial infarction in rats

International audience

The Impact of Preexisting Myocardial Remodeling on Ventricular Function Early after Tetralogy of Fallot Repair

Background: Twenty-three patients (median age 23 months) who underwent Fallot`s tetralogy repair were investigated prospectively to detect a possible association between histopathologic myocardial remodeling and echocardiographic findings of systolic or diastolic ventricular dysfunction. Methods: Intraoperatively resected infundibular bands and subendocardial biopsy samples from the right ventricle (RV) and left ventricle were obtained for histopathologic evaluation. Tissue Doppler echocardiographic interrogation of the ventricles was performed before surgery and in the postoperative period. Results: Histopathologic data revealed hypertrophy of the RV cardiomyocytes and increased interstitial collagen in both ventricles. Mean values of RV isovolumic acceleration decreased significantly at the third evaluation compared with the preoperative values (P = .006). RV myocardial fibrosis greater than 8.3% was associated with a probability of altered E` of at least 0.7 (odds ratio = 2.31). Conclusion: Preoperative histologic myocardial remodeling influenced the postoperative RV function in this group of patients with late repair. Further studies are necessary to evaluate the myocardium in younger patients and to define its influence in the long-term follow-up. (J Am Soc Echocardiogr 2010;23:912-8.)

Impact of Atrial Fibrillation Ablation on Left Ventricular Filling Pressure and Left Atrial Remodeling

Background:Left ventricular (LV) diastolic dysfunction is associated with new-onset atrial fibrillation (AF), and the estimation of elevated LV filling pressures by E/e' ratio is related to worse outcomes in patients with AF. However, it is unknown if restoring sinus rhythm reverses this process.Objective:To evaluate the impact of AF ablation on estimated LV filling pressure.Methods:A total of 141 patients underwent radiofrequency (RF) ablation to treat drug-refractory AF. Transthoracic echocardiography was performed 30 days before and 12 months after ablation. LV functional parameters, left atrial volume index (LAVind), and transmitral pulsed and mitral annulus tissue Doppler (e' and E/e') were assessed. Paroxysmal AF was present in 18 patients, persistent AF was present in 102 patients, and long-standing persistent AF in 21 patients. Follow-up included electrocardiographic examination and 24-h Holter monitoring at 3, 6, and 12 months after ablation.Results:One hundred seventeen patients (82.9%) were free of AF during the follow-up (average, 18 ± 5 months). LAVind reduced in the successful group (30.2 mL/m2 ± 10.6 mL/m2 to 22.6 mL/m2 ± 1.1 mL/m2, p < 0.001) compared to the non-successful group (37.7 mL/m2 ± 14.3 mL/m2 to 37.5 mL/m2 ± 14.5 mL/m2, p = ns). Improvement of LV filling pressure assessed by a reduction in the E/e' ratio was observed only after successful ablation (11.5 ± 4.5 vs. 7.1 ± 3.7, p < 0.001) but not in patients with recurrent AF (12.7 ± 4.4 vs. 12 ± 3.3, p = ns). The success rate was lower in the long-standing persistent AF patient group (57% vs. 87%, p = 0.001).Conclusion:Successful AF ablation is associated with LA reverse remodeling and an improvement in LV filling pressure.