Hypertrophied Hearts Research Articles

CRD-733, a Novel PDE9 (Phosphodiesterase 9) Inhibitor, Reverses Pressure Overload-Induced Heart Failure.

Augmentation of NP (natriuretic peptide) receptor and cyclic guanosine monophosphate (cGMP) signaling has emerged as a therapeutic strategy in heart failure (HF). cGMP-specific PDE9 (phosphodiesterase 9) inhibition increases cGMP signaling and attenuates stress-induced hypertrophic heart disease in preclinical studies. A novel cGMP-specific PDE9 inhibitor, CRD-733, is currently being advanced in human clinical studies. Here, we explore the effects of chronic PDE9 inhibition with CRD-733 in the mouse transverse aortic constriction pressure overload HF model. Adult male C57BL/6J mice were subjected to transverse aortic constriction and developed significant left ventricular (LV) hypertrophy after 7 days (P<0.001). Mice then received daily treatment with CRD-733 (600 mg/kg per day; n=10) or vehicle (n=17), alongside sham-operated controls (n=10). CRD-733 treatment reversed existing LV hypertrophy compared with vehicle (P<0.001), significantly improved LV ejection fraction (P=0.009), and attenuated left atrial dilation (P<0.001), as assessed by serial echocardiography. CRD-733 prevented elevations in LV end diastolic pressures (P=0.037) compared with vehicle, while lung weights, a surrogate for pulmonary edema, were reduced to sham levels. Chronic CRD-733 treatment increased plasma cGMP levels compared with vehicle (P<0.001), alongside increased phosphorylation of Ser273 of cardiac myosin binding protein-C, a cGMP-dependent protein kinase I phosphorylation site. The PDE9 inhibitor, CRD-733, improves key hallmarks of HF including LV hypertrophy, LV dysfunction, left atrial dilation, and pulmonary edema after pressure overload in the mouse transverse aortic constriction HF model. Additionally, elevated plasma cGMP may be used as a biomarker of target engagement. These findings support future investigation into the therapeutic potential of CRD-733 in human HF.

Zebrafish Heart as a Model to Elucidate the Mechanisms of Sudden Cardiac Death

The heart of zebrafish has been used as a simple, low-cost model to study development, structure and function of the heart from early to late stages of life. Also, it has been established as a model to study different cardiac pathologies generated through different methods. Cardiac pathologies include from functional disorders such as arrhythmia, to structural disorders such as hypertrophic heart disease; in many of them, genetic and molecular aspects have been associated. Noteworthy, some of these genetic and molecular factors have been invoked as causes of sudden cardiac death in humans. This adverse outcome is common in many cardiovascular pathologies and can occur at any age. Unfortunately, etiology and physiopathology of sudden cardiac death are unclear, so extensive research in this area is required. This mini-review highlight three related points: First, the relevance of sudden cardiac death in humans. Second, advances in knowledge of the development, function and pathologies in the zebrafish heart model. Finally, the possibility of using the zebrafish model for the study of sudden cardiac. For this review, a literature search was performed using the PubMed database and the search engine Google Scholar: the words sudden cardiac death, zebrafish, arrhythmias, cardiomyopathies were combined for this search.

Многофакторный анализ дифференциально-диагностических параметров у больных бронхиальной астмой средней тяжести с пульмогенной артериальной гипертензией и эссенциальной артериальной гипертензией

Objective: to analyze differential diagnostic parameters in patients with moderate bronchial asthma with pulmogenic arterial hypertension with essential arterial hypertension. Material and Methods: 25 patients with moderate bronchial asthma with pulmogenic arterial hypertension (the 1st group) and 25 patients with moderate bronchial asthma with essential arterial hypertension (the 2nd group) were included in the study. Both groups of patients received step therapy (berodual + inhaled glucocorticosteroids). All patients underwent complex ultrasound examination of intracardiac hemodynamics, examination of blood flow in the right ventricle excretory tract. Systemic arterial pressure was measured according to N. S. Korotkov’s method. ECG was studied (24-hour monitoring). Cold test (at -20 °C-40 °C) was performed in both groups of patients, blood gas composition and pulmonary ventilation function indices were studied. Results: As a result of research established reliable differences in the spirographic indices, blood gas composition in patients with moderate bronchial asthma with pulmogenic arterial hypertension (the 1st group), and reliable differences in partial pressure of oxygen and carbon dioxide (p &lt; 0,05). The 1st group of patients has also higher values of PaCO2 and reliably (p &lt; 0,0,5) and lower values of PaO2, SaO2 in comparison with the comparison group of patients with bronchial asthma of average severity with essential arterial hypertension (the 2nd group). Our data have shown, that in the 1st and 2nd group patients systolic-diastolic cardiac function indexes reliably (p &lt; 0,05; p &lt; 0,001) differed from those ones in healthy subjects. At the same time systolic pressure in the pulmonary artery in the 1st group patients was higher than in the 2nd group patients, and left ventricular ejection fraction was significantly different from that in healthy people and was lower in the 1st group patients than in the 2nd group. We have revealed a reliable correlation between systolic blood pressure and Sа02 (r = 0,52, p &lt; 0,05), studied after cold test, which confirmed the hypothesis of the formation of pulmogenic arterial hypertension against the background of hypoxia. More pronounced changes of FEV1, Sа02, systolic blood pressure in group 1 patients were to some extent due to significant cold hyperresponsiveness in this category of patients. Conclusions: the results of our studies have shown that the decrease of FEV1, FEV50, FEV75, PaO2, SaO2, increased systolic pressure in the pulmonary artery, signs of right heart hypertrophy, disturbances of systolic-diastolic heart function were more pronounced in moderate bronchial asthma patients with pulmogenic arterial hypertension than in moderate bronchial asthma patients with essential arterial hypertension. The proportion of patients (in %) with rhythm disturbances, especially sinus tachycardia, extrasystoles were detected significantly more frequently in group 1 patients than in group 2 patients, which was due to a more pronounced disturbance of systolic-diastolic heart function, higher systolic pressure in the pulmonary artery in persons with moderate bronchial asthma with pulmogenic arterial hypertension.

ATF3 expression in cardiomyocytes and myofibroblasts following transverse aortic constriction displays distinct phenotypes.

BackgroundActivating transcription 3 (ATF3) is a member of the basic leucine zipper family of transcription factors. ATF3 is an immediate early gene expressed following various cellular stresses. ATF3 acts through binding to cyclic AMP response elements found in the promoters of key regulatory proteins that determine cell fate. In the heart, multiple cardiac stresses result in chronic ATF3 expression. Transgenic mice with ATF3 expression in cardiomyocytes clearly demonstrate that ATF3 serves a leading role in heart hypertrophy, cardiac fibrosis, cardiac dysfunction and death. In contrast, the use of ATF3 whole body knockout mice resulted non-conclusive results. The heart is composed of various cell types such as cardiomyocytes, fibroblasts, endothelial and immune cells. The question that we addressed in this study is whether ablation of ATF3 in unique cell types in the heart results in diverse cardiac phenotypes.MethodsATF3-flox mice were crossed with αMHC and Postn specific promoters directing CRE expression and thus ATF3 ablation in cardiomyocytes and myofibroblast cells. Mice were challenged with transverse aortic constriction (TAC) for eight weeks and heart function, ventricle weight, hypertrophic markers, fibrosis markers and ATF3 expression were assessed by qRT-PCR.ResultsThe results of the study show that ATF3 deletion in cardiomyocytes followed by TAC resulted in reduced heart growth and dampened fibrosis response while ATF3 ablation in myofibroblasts displayed a reduced hypertrophic gene program.ConclusionsTAC-operation results in increased ATF3 expression in both myofibroblasts and cardiomyocytes that promotes a hypertrophic program and fibrotic cardiac growth, respectively.

Magnesium Supplementation Attenuates Pulmonary Hypertension via Regulation of Magnesium Transporters.

Pulmonary hypertension (PH) is characterized by profound vascular remodeling and altered Ca2+ homeostasis in pulmonary arterial smooth muscle cells (PASMCs). Magnesium ion (Mg2+), a natural Ca2+ antagonist and a cofactor for numerous enzymes, is crucial for regulating diverse cellular functions, but its roles in PH remains unclear. Here, we examined the roles of Mg2+ and its transporters in PH development. Chronic hypoxia and monocrotaline induced significant PH in adult male rats. It was associated with a reduction of [Mg2+]i in PASMCs, a significant increase in gene expressions of Cnnm2, Hip14, Hip14l, Magt1, Mmgt1, Mrs2, Nipa1, Nipa2, Slc41a1, Slc41a2 and Trpm7; upregulation of SLC41A1, SLC41A2, CNNM2, and TRPM7 proteins; and downregulation of SLC41A3 mRNA and protein. Mg2+ supplement attenuated pulmonary arterial pressure, right heart hypertrophy, and medial wall thickening of pulmonary arteries, and reversed the changes in the expression of Mg2+ transporters. Incubation of PASMCs with a high concentration of Mg2+ markedly inhibited PASMC proliferation and migration, and increased apoptosis, whereas a low level of Mg2+ produced the opposite effects. siRNA targeting Slc41a1/2, Cnnm2, and Trpm7 attenuated PASMC proliferation and migration, but promoted apoptosis; and Slc41a3 overexpression also caused similar effects. Moreover, siRNA targeting Slc41a1 or high [Mg2+] incubation inhibited hypoxia-induced upregulation and nuclear translocation of NFATc3 in PASMCs. The results, for the first time, provide the supportive evidence that Mg2+ transporters participate in the development of PH by modulating PASMC proliferation, migration, and apoptosis; and Mg2+ supplementation attenuates PH through regulation of Mg2+ transporters involving the NFATc3 signaling pathway.

Cutoff value for hypertrophic heart weight in the Japanese population.

Cardiac hypertrophy is a clinical risk factor for cardiovascular death (CVD) frequently recorded in autopsy reports, but the diagnostic criteria for the condition have not been clearly-established for autopsy. This study aimed to estimate the cutoff value for hypertrophic heart weight that can efficiently assist the postmortem diagnosis of CVD. We analyzed accumulated autopsy data from 3534 individuals aged 0-101years. We found that heart weight increased linearly with a person's age until 20years, after which it remained stable. The mean heart weight in CVD cases was 473g in men and 379g in women. The mean heart weight in non-CVD cases was 385g in men and 320g in women. Receiver operating characteristic curve analysis for CVD assessment revealed that the cutoff value of heart weight was 407g (odds ratio of 4.2) in men and 327g (2.6) in women, and that of heart weight/body height was 2.38g/cm (4.0) in men and 2.15g/cm (2.6) in women, respectively. Overall, heart weight was a more useful predictor of CVD in men than in women. In logistic regression analysis, the predictive power of heart weight for CVD was higher than that of body mass index in both sexes. Thus, the criteria for hypertrophic heart weight are practical and useful for autopsy recordings, and it can be helpful for postmortem diagnosis of CVD. Our report is the first to reveal the cutoff value for hypertrophic heart weight in the Japanese population.

Clinical-instrumental correlations of local elastic properties of the thoracic aorta in patients with coronary atherosclerosis

Introduction . This is part of research with aim of increasing the effectiveness of echocardiography in patients with coronary atherosclerosis by assessing local elastic properties of the thoracic aorta using modern ultrasound technologies. Aim . To analyze correlations between deterioration of local elastic properties of the thoracic aorta, impairment of renal filtration function, severity of left ventricular hypertrophy and ischemic heart disease (IHD) risk factors in patients with coronary atherosclerosis. Materials and methods . From 2016 to 2019, 109 patients aged 39 to 82 years, who were divided into 2 groups according to the results of invasive coronarography, were examined: 64 patients with coronary atherosclerosis and 45 patients without coronary atherosclerosis. Using transthoracic echocardiography, the following were obtained: coefficient of distensibility, compliance coefficient, Peterson’s elasticity modulus, stiffness index of the ascending thoracic aorta. Analysis of correlations between these indices, indicators of IHD risk factors, left ventricular mass index (LVMI), glomerular filtration rate (GFR) was done. Results . Group without coronary atherosclerosis showed negative correlations of compliance coefficient with LVMI (r=–0.421), positive correlations of Peterson’s elasticity modulus and stiffness index with LVMI (r=0.304, r=0.397). Group with coronary atherosclerosis showed negative correlations of the coefficient of distensibility with LVMI (r=–0.331), Peterson’s elasticity modulus and stiffness index with GFR (r=–0.473, r=–0.469). Positive correlations were found between coefficients of compliance and distensibility with GFR (r=0.418, r=0.473), Peterson’s elasticity modulus and the stiffness index with LVMI (r=0.33, r=0.304). Conclusion . Research reveals relationship between the local elastic properties of the thoracic aorta, GFR and severity of LV hypertrophy in patients with coronary atherosclerosis and the effectiveness of echocardiographic technologies in their assessment.

Klotho Deficiency Causes Heart Aging via Impairing the Nrf2-GR Pathway.

Cardiac aging is an important contributing factor for heart failure, which affects a large population but remains poorly understood. The purpose of this study is to investigate whether Klotho plays a role in cardiac aging. Heart function declined in old mice (24 months), as evidenced by decreases in fractional shortening, ejection fraction, and cardiac output. Heart size and weight, cardiomyocyte size, and cardiac fibrosis were increased in old mice, indicating that aging causes cardiac hypertrophy and remodeling. Circulating Klotho levels were dramatically decreased in old mice, which prompted us to investigate whether the Klotho decline may cause heart aging. We found that Klotho gene mutation (KL-/-) largely decreased serum klotho levels and impaired heart function. Interestingly, supplement of exogenous secreted Klotho prevented heart failure, hypertrophy, and remodeling in both old mice and KL (-/-) mice. Secreted Klotho treatment inhibited excessive cardiac oxidative stress, senescence and apoptosis in old mice and KL (-/-) mice. Serum phosphate levels in KL (-/-) mice were kept in the normal range, suggesting that Klotho deficiency-induced heart aging is independent of phosphate metabolism. Mechanistically, Klotho deficiency suppressed GR (glutathione reductase) expression and activity in the heart via inhibition of transcription factor Nrf2 (nuclear factor-erythroid 2 p45-related factor 2). Furthermore, cardiac-specific overexpression of GR prevented excessive oxidative stress, apoptosis, and heart failure in both old and KL (-/-) mice. Klotho deficiency causes cardiac aging via impairing the Nrf2-GR pathway. Supplement of exogenous secreted Klotho represents a promising therapeutic strategy for aging-associated cardiomyopathy and heart failure.

Lack of Contribution of p66shc to Pressure Overload-Induced Right Heart Hypertrophy.

The leading cause of death in pulmonary arterial hypertension (PAH) is right ventricular (RV) failure (RVF). Reactive oxygen species (ROS) have been suggested to play a role in the development of RV hypertrophy (RVH) and the transition to RVF. The hydrogen peroxide-generating protein p66shc has been associated with left ventricular (LV) hypertrophy but its role in RVH is unclear. The purpose of this study was to determine whether genetic deletion of p66shc affects the development and/or progression of RVH and RVF in the pulmonary artery banding (PAB) model of RV pressure overload. The impact of p66shc on mitochondrial ROS formation, RV cardiomyocyte function, as well as on RV morphology and function were studied three weeks after PAB or sham operation. PAB in wild type mice did not affect mitochondrial ROS production or RV cardiomyocyte function, but induced RVH and impaired cardiac function. Genetic deletion of p66shc did also not alter basal mitochondrial ROS production or RV cardiomyocyte function, but impaired RV cardiomyocyte shortening was observed following PAB. The development of RVH and RVF following PAB was not affected by p66shc deletion. Thus, our data suggest that p66shc-derived ROS are not involved in the development and progression of RVH or RVF in PAH.

Mir15a/mir16-1 cluster and its novel targeting molecules negatively regulate cardiac hypertrophy.

In response to pathological stimuli, the heart develops ventricular hypertrophy that progressively decompensates and leads to heart failure. miRNAs are increasingly recognized as pathogenic factors, clinically relevant biomarkers, and potential therapeutic targets. We identified that mir15a/mir16‐1 cluster was negatively correlated with hypertrophic severity in patients with hypertrophic cardiomyopathy. The mir15a/mir16‐1 expression was enriched in cardiomyocytes (CMs), decreased in hypertrophic human hearts, and decreased in mouse hearts after transverse aortic constriction (TAC). CM‐specific mir15a/mir16‐1 knockout promoted cardiac hypertrophy and dysfunction after TAC. CCAAT/enhancer binding protein (C/EBP)β was responsible for the downregulation of mir15a/mir16‐1 cluster transcription. Mechanistically, mir15a/mir16‐1 cluster attenuated the insulin/IGF1 signal transduction cascade by inhibiting multiple targets, including INSR, IGF‐1R, AKT3, and serum/glucocorticoid regulated kinase 1 (SGK1). Pro‐hypertrophic response induced by mir15a/mir16‐1 inhibition was abolished by knockdown of insulin receptor (INSR), insulin like growth factor 1 receptor (IGF1R), AKT3, or SGK1. In vivo systemic delivery of mir15a/mir16‐1 by nanoparticles inhibited the hypertrophic phenotype induced by TAC. Importantly, decreased serum mir15a/mir16‐1 levels predicted the occurrence of left ventricular hypertrophy in a cohort of patients with hypertension. Therefore, mir15a/mir16‐1 cluster is a promising therapeutic target and biomarker for cardiac hypertrophy.

Research Progress on the Interaction Between Autophagy and Energy Homeostasis in Cardiac Remodeling.

Cardiac remodeling is a common pathological process in various heart diseases, such as cardiac hypertrophy, diabetes-associated cardiomyopathy and ischemic heart diseases. The inhibition of cardiac remodeling has been suggested to be a potential strategy for preventing heart failure. However, the mechanisms involved in cardiac remodeling are quite complicated. Recent studies have reported a close correlation between autophagy and energy homeostasis in cardiac remodeling associated with various heart diseases. In this review, we summarize the roles of autophagy and energy homeostasis in cardiac remodeling and discuss the relationship between these two processes in different conditions to identify potential targets and strategies for treating cardiac remodeling by regulating autophagy.

Abstract 16165: Inorganic Arsenic Induces Sex-Dependent Pathological Cardiac Hypertrophy

Exposure to inorganic arsenic (iAS) through drinking water is well-associated with adverse cardiovascular outcomes, yet the mechanisms through which it induces these effects are not fully understood. Recent epidemiological findings highlight an association between iAS exposure and altered left ventricular geometry in both the presence and absence of hypertension. We therefore tested the hypothesis that iAS exposure has a bimodal impact on cardiac-intrinsic and hemodynamic mechanisms that together induce pathological remodeling of the myocardium. Adult male and female mice were exposed to an environmentally relevant dose of 615 μg/L NaAsO 2 for eight weeks. Males (n=9-10 mice/group) exhibited increased systolic blood pressure (115.1±3.0 vs. 106.0±2.3 mmHg, p=0.0350) via tail cuff photoplethysmography, left ventricular wall thickening (0.98±0.01 vs. 0.88±0.01 mm, p&lt;0.0001) via transthoracic echocardiography, increased heart weight to tibia length (8.56±0.21 vs. 7.15±0.24 mg/mm; n=24 mice/group), and increased plasma atrial natriuretic peptide (47.85±12.0 vs. 15.14±3.73 pg/mL, p=0.0379) via enzyme immunoassay. Myocardial mRNA transcript levels (n=10 hearts/group) of Acta1 (1.36±0.18 vs. 0.73±0.11, p=0.0037), Myh7 (1.53±0.15 vs. 1.04±0.10, p=0.0138), and Nppa (2.40±0.29 vs. 1.02±0.07, p=0.0001) were increased, and Myh6 (0.92±0.17 vs. 1.14±0.23, p=0.0001) was decreased, evidencing pathological hypertrophy in the male heart. Female hearts, however, were largely protected at this eight-week timepoint as similar changes were not detected. Further investigation found that Rcan1 was upregulated (1.47±0.19 vs. 0.97±0.04, p=0.0161; n=10 hearts/group) in male hearts, suggesting that calcineurin-NFAT was activated. Interestingly, iAS was sufficient to activate NFAT (0.82±0.11 vs. 0.46±0.05, p=0.0214; n=8 wells/group) independent of blood pressure via luciferase assay. In conclusion, these results demonstrate for the first time that iAS may cause pathological cardiac hypertrophy not only by increasing hemodynamic load, but also by activating calcineurin-NFAT and inducing fetal gene expression in the male heart, thus providing novel mechanistic insight into the threat of iAS exposure to the cardiovascular system.

Abstract 15465: Upregulation of Mitochondrial Atpase Inhibitory Factor 1 Mediates Increased Glycolysis in Pathological Cardiac Hypertrophy

Background: During the development of heart failure cardiac fuel metabolism switches from predominantly fatty acid oxidation (FAO) to increased reliance on glucose, especially glycolysis. Mechanisms responsible for the switch are poorly understood but appear to be coupled with impaired mitochondrial function. We recently demonstrated that increased glucose metabolism is required for cardiomyocytes growth during pathological remodeling. Hypothesis: Upregulation of mitochondrial ATPase inhibitory factor 1 (ATPIF1) in hypertrophied hearts suppresses ATP synthesis and shifts cardiac metabolism from fatty acid oxidation towards glucose metabolism. Methods and Results: We report that ATPIF1 expression is upregulated in cardiomyocytes and mouse hearts undergoing pathological hypertrophy. Using genetic models of ATPIF1 gain- and loss-of-function in cardiomyocytes and in mouse hearts,we find that upregulation of ATPIF1 in cardiac hypertrophy inhibits ATP synthesis. Furthermore, quantitative analysis of chemical crosslinking by mass spectrometry revealed that increased expression of ATPIF1 promoted the formation of F o F 1 -ATP synthase nonproductive tetramer. Impairment of F o F 1 -ATP synthase function in respiring mitochondria increasedROS generation resulting in transcriptional activation of glycolysis. Cardiac-specific deletion of ATPIF1 in mice prevented the switch to glycolysis in pressure overload induced cardiac hypertrophy. Conclusions: We show that upregulation of ATPIF1 drives glucose metabolism at the expense of energy supply during the pathological growth of cardiomyocytes. Our study proposes a central role of ATP synthase in toggling anabolic and catabolic metabolism during pathological remodeling, illustrating a new concept for metabolic reprogramming of the heart.

Deubiquitinase Ubiquitin-Specific Protease 10 Deficiency Regulates Sirt6 signaling and Exacerbates Cardiac Hypertrophy.

BackgroundCardiac hypertrophy (CH) is a physiological response that compensates for blood pressure overload. Under pathological conditions, hypertrophy can progress to heart failure as a consequence of the disorganized growth of cardiomyocytes and cardiac tissue. USP10 (ubiquitin‐specific protease 10) is a member of the ubiquitin‐specific protease family of cysteine proteases, which are involved in viral infection, oxidative stress, lipid drop formation, and heat shock. However, the role of USP10 in CH remains largely unclear. Here, we investigated the roles of USP10 in CH.Methods and ResultsCardiac‐specific USP10 knockout (USP10‐CKO) mice and USP10‐transgenic (USP10‐TG) mice were used to examined the role of USP10 in CH following aortic banding. The specific functions of USP10 were further examined in isolated cardiomyocytes. USP10 expression was increased in murine hypertrophic hearts following aortic banding and in isolated cardiomyocytes in response to hypertrophic agonist. Mice deficient in USP10 in the heart exhibited exaggerated cardiac hypertrophy and fibrosis following pressure overload stress, which resulted in worsening of cardiac contractile function. In contrast, cardiac overexpression of USP10 protected against pressure overload‐induced maladaptive CH. Mechanistically, we demonstrated that USP10 activation and interaction with Sirt6 in response to angiotensin II led to a marked increase in the ubiquitination of Sirt6 and resulted in Akt signaling downregulation and attenuation of cardiomyocyte hypertrophy. Accordingly, inactivation of USP10 reduced Sirt6 abundance and stability and diminished Sirt6‐induced downstream signaling in cardiomyocytes.ConclusionsUSP10 functions as a Sirt6 deubiquitinase that induces cardiac myocyte hypertrophy and triggers maladaptive CH.

X-ray diffraction and second harmonic imaging reveal new insights into structural alterations caused by pressure-overload in murine hearts

We demonstrate a label-free imaging approach to study cardiac remodeling of fibrotic and hypertrophic hearts, bridging scales from the whole organ down to the molecular level. To this end, we have used mice subjected to transverse aortic constriction and imaged adjacent cardiac tissue sections by microfocus X-ray diffraction and second harmonic generation (SHG) imaging. In this way, the acto-myosin structure was probed in a spatially resolved manner for entire heart sections. From the recorded diffraction data, spatial maps of diffraction intensity, anisotropy and orientation were obtained, and fully automated analysis depicted the acto-myosin filament spacing and direction. X-ray diffraction presented an overview of entire heart sections and revealed that in regions of severe cardiac remodeling the muscle mass is partly replaced by connective tissue and the acto-myosin lattice spacing is increased at these regions. SHG imaging revealed sub-cellular structure of cardiac tissue and complemented the findings from X-ray diffraction by revealing micro-level distortion of myofibrils, immune cell infiltration at regions of cardiac remodeling and the development of fibrosis down to the scale of a single collagen fibril. Overall, our results show that both X-ray diffraction and SHG imaging can be used for label-free and high-resolution visualization of cardiac remodeling and fibrosis progression at different stages in a cardiac pressure-overload mouse model that cannot be achieved by conventional histology.

Inhibition of the water channel aquaporin-1 prevents myocardial remodeling by blocking the transmembrane transport of hydrogen peroxide

Abstract Background Pathological remodeling of the myocardium has long been known to involve oxidant signaling, but so far, strategies using systemic anti-oxidants have generally failed to prevent it. Aquaporins are a family of transmembrane water channels with thirteen isoforms currently known. Some isoforms have been implicated in oxidant signaling. AQP1 is the most abundant aquaporin in cardiovascular tissues but its specific role in cardiac remodeling remains unknown. Purpose We tested the role of AQP1 as a key regulator of oxidant-mediated cardiac remodeling amenable to targeted pharmacological therapy. Methods We used mice with genetic deletion of Aqp1 (and wild-type littermate), as well as primary isolates from the same mice and human iPSC/Engineered Heart Tissue to test the role of AQP1 in pro-hypertrophic signaling. Human cardiac myocyte-specific (PCM1+) expression of AQP's and genes involved in hypertrophic remodeling was studied by RNAseq and bioinformatic GO pathway analysis. Results RNA sequencing from human cardiac myocytes revealed that the archetypal AQP1 is a major isoform. AQP1 expression correlates with the severity of hypertrophic remodeling in patients with aortic stenosis. The AQP1 channel was detected at the plasma membrane of human and mouse cardiac myocytes from hypertrophic hearts, where it colocalizes with the NADPH oxidase-2 (NOX2) and caveolin-3. We show that hydrogen peroxide (H2O2), produced extracellularly, is necessary for the hypertrophic response of isolated cardiac myocytes and that AQP1 facilitates the transmembrane transport of H2O2 through its water pore, resulting in activation of oxidant-sensitive kinases in cardiac myocytes. Structural analysis of the amino acid residues lining the water pore of AQP1 supports its permeation by H2O2. Deletion of Aqp1 or selective blockade of AQP1 intra-subunit pore (with Bacopaside II) inhibits H2O2 transport in mouse and human cells and rescues the myocyte hypertrophy in human induced pluripotent stem cell-derived engineered heart muscle. This protective effect is due to loss of transmembrane transport of H2O2, but not water, through the intra-subunit pore of AQP1. Treatment of mice with clinically-approved Bacopaside extract (CDRI08) inhibitor of AQP1 attenuates cardiac hypertrophy and fibrosis. Conclusion We provide the first demonstration that AQP1 functions as an aqua-peroxiporin in primary rodent and human cardiac parenchymal cells. We show that cardiac hypertrophy is mediated by the transmembrane transport of H2O2 through the AQP1 water channel. Our studies open the way to complement the therapeutic armamentarium with specific blockers of AQP1 for the prevention of adverse remodeling in many cardiovascular diseases leading to heart failure. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): FRS-FNRS, Welbio

Silent myocardial infarction among young sudden cardiac death victims

Abstract Background Silent myocardial infarctions (SMIs) occur with atypical or no symptoms at all. The burden of SMIs among sudden cardiac death victims have recently been acknowledged. However, the prevalence of previously undetected SMI in young victims remains unclear. Purpose The aim of the present study was to determine the prevalence of autopsy verified SMI in SCD victims under 50 years old without a prior diagnosis of coronary artery disease (CAD). Methods Fingesture study consists of systematically collected consecutive victims of SCD in Northern Finland between years 1998–2017 (n=5,869). According to Finnish law, all unexpected deaths undergo medico-legal autopsy. The autopsies routinely included histological examinations, and a toxicology investigation was carried out if needed. The SMI was defined as focal scar detected by macroscopic evaluation of the dissected ventricles and histologic analysis of the myocardial samples with an absence of a history of previously diagnosed CAD. Pre-mortem clinical history was obtained from medical records, standardized questionnaire to the closest family members of the victims and police reports about the conditions of the death. Results Overall, 10.4% off all SCDs occurred among victims under the age of 50 years (610 victims). Most common underlying cause of SCD among young was CAD (44%). About 90% of the victims had no clinical diagnosis of CAD, however, 34% (78 victims) had previously undetected myocardial scar at autopsy indicating a previous SMI. The mean age of the young SMI victims was 44±4 and they were mostly men (87%). 24% of SCDs occurred during physical activity and 21% had SCD outdoors. The mean heart weight was 466±110 g and 67% had hypertrophied hearts. Three vessel disease was detected in 69% of the victims. Alcohol was detected in 17% of victims in toxicology investigations. Conclusions Previously undetected myocardial infarction is also common among young victims who experienced CAD associated SCD. Three vessel disease and cardiac hypertrophy were common autopsy findings among young SMI victims and about a fourth had SCD during physical activity. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Sigrid Juselius Foundation, Finnish Foundation for Cardiovascular Research

M6A RNA methylation contributes to translational control in heart failure progression

Abstract Background/Introduction Heart failure, characterized by reduced cardiac function and left ventricular dilatation, is a leading cause of hospital admission and mortality. Among increased apoptosis and fibrosis, the progression of heart failure is accompanied by changes in gene expression. There is increasing evidence, that also epigenetic processes such as DNA and histone modifications, long non-coding RNAs and transcription factors orchestrate aberrant gene expression in heart failure. Among these epigenetic processes, N6-methyladenosine (m6A) is the most prevalent modification found in all classes of RNA. Such m6A patterns in for example mRNA can have influence on various mechanisms such as splicing, transport, storage or decay of mRNAs. Due to its reversible and dynamic nature regulated via methyltransferases (mainly the METTL3/METTL14/WTAP-complex) and demethylases (mainly FTO and ALkBH5) it adds a new layer of epigenetic regulation. Purpose Changes in epigenetic processes are important mechanisms in heart failure progression. We aimed to elucidate the potential role of m6A methylation in heart failure development. Methods We analysed m6A methylation in different stages of heart failure progression in mouse and human tissue via methylated RNA immunoprecipitation (meRIP) followed by next generation sequencing (NGS). With polysome fractionation followed by NGS, we studied a potential link between polysomal occupancy and m6a RNA methylation. Results We found that approximately one quarter of all RNA transcripts in healthy mouse and human tissue carry m6A RNA methylation. During progression to heart failure we found that changes in m6A methylation exceed changes in gene expression in both, mouse and human. RNAs with altered m6A levels were mainly linked to metabolic and regulatory pathways, whereas changes in expression represented changes in structural plasticity. Furthermore, we found a link between m6A RNA methylation and altered RNA translation. Interestingly, transcripts with unchanged expression level but a differential change in their methylation level also showed differential polysomal occupancy. We could show a corresponding change in protein level, which points to a potential new mechanism of transcription-independent modulation of translation. The importance of m6A methylation was furthermore confirmed in a cardiomyocyte specific knock-out of the RNA demethylase FTO in mice where it lead to impaired cardiac function compared to control mice. Conclusions We could show that the m6A landscape is altered in heart hypertrophy and heart failure. Methylation changes exceed expression changes in disease progression and lead to changes in protein abundance, which uncovers a new transcription-independent mechanism of translation regulation. Therefore, our data suggest that targeting epitranscriptomic mechansims, such as m6A methylation, might be a an interesting approach for thereapeutic interventions. Funding Acknowledgement Type of funding source: Public grant(s) – EU funding. Main funding source(s): SFB 1002 Modulatory Units in Heart Failure

Left ventricular septal convexity in differentiating hypertrophic cardiomyopathy from hypertensive heart disease – cardiac MRI study

Abstract Background Subjects with hypertrophic cardiomyopathy (HCM) and hypertensive heart disease (HHD) have left ventricular hypertrophy (LVH). It is a common clinical problem to distinguish HCM from HHD. Septal convexity (SC) into the left ventricle is increased in subjects with hypertrophic cardiomyopathy (HCM)-causing mutations with and without LVH. Purpose Our objective was to study if SC by cardiac magnetic resonance (CMR) differentiates between HCM and HHD. Methods We measured SC in 29 subjects with hypertension and LVH (left ventricular maximal wall thickness (LVMWT) ≥13 mm), in 49 subjects with HCM (LVMWT ≥13 mm) caused by the D175N mutation in the alpha-tropomyosin (TPM1) or the Q1061X mutation in the myosin binding protein C (MYBPC3) genes, and in 20 healthy controls with no LVH. SC into the LV was measured in end-diastolic 4-chamber images as the maximal distance between LV septal endocardial border and a line connecting septal mid-wall points at the level of tricuspid valve insertion and at the level of apical right ventricular insertion on the LV. Results Subjects with HCM had significantly increased septal convexity compared to subjects with HHD both in non-indexed and in BSA-indexed measurements (10.7±4.0 mm vs 4.9±2.7 mm, P&amp;lt;0.001 and 5.5±2.1 mm/m2 vs 2.4±1.3 mm/m2, P&amp;lt;0.001). To differentiate between HCM and HHD, septal convexity cutoff value of 7.85 mm performed best with sensitivity of 77% and specificity of 90%. BSA-indexed SC cutoff value of 3.68 mm differentiated between HCM and HHD with sensitivity of 81% and specificity of 86%. Conclusions CMR derived septal convexity is easily measured and is useful in discriminating between HCM caused by sarcomere mutations versus HHD. Measurement of septal convexity Funding Acknowledgement Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): Finnish Foundation of Cardiovascular Research, the special governmental subsidy for health sciences research of the University Hospital of Kuopio

Spectrum of Cardiac Arrhythmias in children with left ventricular non-compaction

Abstract Left ventricular non-compaction (LVNC) represents a genetically heterogeneous primary cardiomyopathy which occurs in both children and adults, can be isolated or combined with other congenital heart diseases and reveals substantial clinical polymorphism. Isolated LVNC is a rare phenomenon more commonly being a part other cardiovascular phenotypes such as hypertrophic cardiomyopathy, restrictive cardiomyopathy or congenital heart disorders. Clinical features on LVNC include main triade: heart failure, ventricular arrhythmias (VA) and thromboembolism. Purpose The aim of this study was to analyze the clinical characteristics of arrhythmias in children with LVNC. Methods We enrolled 15 patients diagnosed with LVNC. For all patients enrolled the clinical examination included ECG, echocardiography, Holter monitoring, family history and neurological examination. The echocardiographic diagnosis for LVNC was based on the criteria of Stollberger and Jenni. Several patients additionally received MRI. Target sequencing and WES were performed using a targeted panel of 108 cardiomyopathy-associated genes. All patients had a written parental consent form for including in this study. Results The mean age oat presentation was 7.46±4.4 year (from 0.5 to 14 year old). 4 patients had ventricular arrhythmias, which manifested as isolated premature ventricular contractions (PVCs) in two patients; ventricular tachycardia (VT) in two patients, 3 – supraventricular arrhythmias, 2 – WPW syndrome/phenomenon, 5 - atrioventricular block (1 and 2 degrees), atrial fibrillation – 1. Antiarrhythmic therapy received 7 patients (3 with VA; 3 with SVA). In total 21 variants of interest were identified in all 15 patients in 18 different genes. All four patients with variants in ion channel genes had documented supraventricular and ventricular arrhythmias. In 3 out of 5 patients with AV block variants in contractile sarcomeric and related genes were detected. Four patients reached endpoints such as cardiovascular death (2 patients) and heart transplantation (2 patients). Conclusions Arrhythmic manifestations in children with left ventricular non-compaction can vary from conduction disease to SVT and ventricular arrhythmias and these arrhythmias have been associated with prognosis and outcome. Funding Acknowledgement Type of funding source: None