Cardiac Dilatation Research Articles

Left ventricular response in the transition from hypertrophy to failure recapitulates distinct roles of Akt, β-arrestin-2, and CaMKII in mice with aortic regurgitation.

BackgroundAlthough aortic regurgitation (AR) is a clinically important condition that is becoming increasingly common, few relevant murine models and mechanistic studies exist for this condition. In this study, we attempted to delineate the pathological and molecular changes and address the roles of some potentially relevant molecules in an animal model of surgically induced AR.MethodsAR was induced by puncturing the aortic valve leaflets in C57BL/6J mice under echocardiographic guidance.ResultsAs early as 1 week following AR, the left ventricles (LV) displayed marked impairments in diastolic function and coronary flow reserve (CFR), as well as cardiac hypertrophy and chamber dilatation at both end-systole and end-diastole. LV free wall thickening and cardiomyocyte hypertrophy in LV were observed 2 weeks following of AR while a decline in ejection fraction was not seen until after 4 weeks. Nppa (natriuretic peptide A) and Nppb (natriuretic peptide B) increased over time, in conjunction with prominent Akt activation as well as slight CaMKII (Ca2+/calmodulin-dependent protein kinase II) activation and biphasic changes in β-arrestin-2 expression. Treatment of AR mice with Akt inhibition exacerbated the eccentric hypertrophy, while neither inhibition of CaMKII nor β-arrestin-2 overexpression influenced the response to AR.ConclusionsOur structural, functional, molecular and therapeutic analyses reveal that Akt, but not CaMKII or β-arrestin-2, plays a regulatory role in the development of LV remodeling after AR in Mice. These results may shed important light on therapeutic targets for volume overloaded cardiomyopathy.

Anatomopathological changes in canine distemper seropositive dogs and virus detection in sinoatrial nodes

Canine distemper is a viral disease that affects several systems on dogs, among them, the cardiovascular system. The aim of this study was to identify canine distemper virus (CDV) in the sinoatrial node (SAN) of dogs serologically positive for distemper by Polymerase Chain Reaction preceded by reverse transcription (RT-PCR), and to analyze gross and microscopic changes of distemper in the heart and other tissues. SAN and tissue fragments were collected from 17 serologically positive dead animals, necropsied from October 2015 to December 2016. In the heart, right heart dilatation was observed in 13 dogs (76.47%) and left concentric hypertrophy in two dogs (11.76%). Microscopically, lymphocytic myocarditis was observed in four (23.53%) dogs and 41.18% presented viral inclusion corpuscles of CDV in the bladder epithelium. Only one (5.88%) dog presented a 319 bp target fragment for distemper virus using primers CDV 1 and CDV 2 at the sinoatrial node. In conclusion, CDV can be located in the sinoatrial node of naturally infected dogs, as demonstrated in this study by the RT-PCR technique, reinforcing the hypothesis that CDV is capable of causing inflammatory lesions in the sinoatrial node of this species. Macroscopic and microscopic cardiac changes are frequently observed in dogs with distemper, mainly cardiac dilatation and myocarditis. Viral inclusions of CDV in bladder epithelial cells are an important microscopic finding for the diagnosis of distemper.

Systemic and heart autonomous effects of sphingosine Δ4 desaturase deficiency in lipotoxic cardiac pathophysiology.

ABSTRACTLipotoxic cardiomyopathy (LCM) is characterized by cardiac steatosis, including the accumulation of fatty acids, triglycerides and ceramides. Model systems have shown the inhibition of ceramide biosynthesis to antagonize obesity and improve insulin sensitivity. Sphingosine Δ4 desaturase (encoded by ifc in Drosophila melanogaster) enzymatically converts dihydroceramide into ceramide. Here, we examine ifc mutants to study the effects of desaturase deficiency on cardiac function in Drosophila. Interestingly, ifc mutants exhibited classic hallmarks of LCM: cardiac chamber dilation, contractile defects and loss of fractional shortening. This outcome was phenocopied in global ifc RNAi-mediated knockdown flies. Surprisingly, cardiac-specific ifc knockdown flies exhibited cardiac chamber restriction with no contractile defects, suggesting heart autonomous and systemic roles for ifc activity in cardiac function. Next, we demonstrated that ifc mutants exhibit suppressed Sphingosine kinase 1 (Sk1) expression. Ectopic overexpression of Sk1 was sufficient to prevent cardiac chamber dilation and loss of fractional shortening in ifc mutants. Partial rescue was also observed with cardiac- and fat-body-specific Sk1 overexpression. Finally, we showed that cardiac-specific expression of Drosophila inhibitor of apoptosis (dIAP) also prevented cardiac dysfunction in ifc mutants, suggesting a role for caspase activity in the observed cardiac pathology. Collectively, we show that spatial regulation of sphingosine Δ4 desaturase activity differentially affects cardiac function in heart autonomous and systemic mechanisms through tissue interplay.

Arrhythmia in people living with HIV/AIDS

With improvement in longevity and therapy of HIV; acquired heart diseases are expected to become more and more prevalent. The electric abnormalities in HIV/AIDS are not very rare. These electrical abnormalities in HIV/ AIDS patients may result from the structural heart diseases because of accelerated atherosclerosis, or cardiac dilation as a sequela of myocarditis, or infective endocarditis or pericardial afflictions in HIV. These electrical disorders can present with a history of palpitations, missed beats or even sudden cardiac death. Both tachy- and bradyarrhythmia may be seen in people living with HIV/AIDS.

Cardiovascular system state changes in non-Hodgkin’s lymphoma patients during chemotherapy

Chemotherapy is one of reliable and proven methods of malignant tumor and blood diseases treatment but however the drug side effects (particularly cardiotoxicity) occur. More often cardiovascular complications connect with anthracyclines and related drugs (doxorubicin, daunorubicyn, epirubicyn, idarubicyn, mitoxantron) which usually used at medical scheme because of wide spectrum of action and high effectiveness prescription. Risk of cardiotoxicity formation and existing diseases progression increases according to drug dose, patient’s age, cardiovascular risk factors presence and cardiovascular diseases history. Material and methods . 88 patients with established non-Hodgkin’s lymphoma diagnosis were examined in order to assess cardiovascular system state and pathology nature – 33 patients before chemotherapy and 55 patients in the long-term follow-up period (one year after the start of chemotherapy). Results . It was found that antitumor drugs induced cardiotoxicity may manifest at the beginning of chemotherapy as well as following up period. The cardiac cameras dilation associated with the increase of NTproBNP serum content (N-terminal fragment of natriuretic peptide type B precursor) – the main biomarker of myocardial dysfunction has been revealed by instrumental research.

4968Increased Gao expression underlies cardiac dysfunction and lethal arrhythmias accompanied with abnormal Ca2+ handling

Abstract Background We previously demonstrated that a transcriptional repressor, neuron restrictive silencer factor (NRSF), maintains normal cardiac function and electrical stability. Transgenic mice expressing a dominant-negative mutant of NRSF in their hearts (dnNRSF-Tg) exhibit systolic dysfunction with cardiac dilation and premature death due to lethal arrhythmias like human dilated cardiomyopathy (DCM). Underlining mechanisms remain to be elucidated, however. Purpose We studied underling mechanisms by which NRSF maintains normal cardiac function to identify novel therapeutic targets for heart failure. Methods and results We generated cardiac-specific NRSF knockout mice (NRSFcKO) and confirmed that cardiac phenotypes of NRSFcKO are similar to those of dnNRSF-Tg. cDNA microarray analysis revealed that cardiac gene expression of GNAO1 that encodes Gαo, a member of inhibitory G protein Gαi family, is increased in both dnNRSF-Tg and NRSFcKO ventricles. We confirmed that GNAO1 is a direct target of NRSF through ChIP-seq analysis, reporter assay and electrophoretic mobility shift assay. In dnNRSF-Tg, pharmacological inhibition of Gαo with pertussis toxin improved systolic dysfunction and knockdown of Gαo by crossing with GNAO1 knockout mice improved not only systolic function but also frequency of ventricular arrhythmias and survival rates. Electrophysiological and biochemical analysis in ventricular myocytes obtained from dnNRSF-Tg demonstrated that genetic reduction of Gαo ameliorated abnormalities in Ca2+ handling, which include increased current density in surface sarcolemmal L-type Ca2+ channel, reduced content of sarcoplasmic reticulum Ca2+ and lowered peak of Ca2+ transient. Furthermore, genetic reduction of Gαo attenuated increased phosphorylation levels of CAMKII in dnNRSF-Tg ventricles, which presumably underlies the improvement in Ca2+ handling. In addition, we identified increased Gαo expression in ventricles of heart failure model mice induced by transverse aortic constriction and cardiac troponin T mutant DCM model mice, in both of which, genetic reduction of Gαo ameliorated cardiac dysfunction. Figure 1 Conclusions We found that increased expression of Gαo, induced by attenuation of NRSF-mediated repression, plays a crucial role in the progression of cardiac dysfunction and lethal arrhythmias by evoking Ca2+ handling abnormality. These data demonstrate that Gαo is a potential therapeutic target for heart failure.

A genetic mouse model of severe iron deficiency anemia reveals tissue-specific transcriptional stress responses and cardiac remodeling

Iron is a micronutrient fundamental for life. Iron homeostasis in mammals requires sustained postnatal intestinal iron absorption that maintains intracellular iron concentrations for central and systemic metabolism as well as for erythropoiesis and oxygen transport. More than 1 billion people worldwide suffer from iron deficiency anemia (IDA), a state of systemic iron insufficiency that limits the production of red blood cells and leads to tissue hypoxia and intracellular iron stress. Despite this tremendous public health concern, very few genetic models of IDA are available to study its progression. Here we developed and characterized a novel genetic mouse model of IDA. We found that tamoxifen-inducible deletion of the mammalian iron exporter ferroportin exclusively in intestinal epithelial cells leads to loss of intestinal iron absorption. Ferroportin ablation yielded a robust phenotype of progressive IDA that develops in as little as 3 months following disruption of intestinal iron absorption. We noted that, at end-stage IDA, tissue-specific transcriptional stress responses occur in which the heart shows little to no hypoxic and iron stress compared with other peripheral organs. However, morphometric and echocardiographic analysis revealed massive cardiac hypertrophy and chamber dilation, albeit with increased cardiac output at very low basal heart rates. We propose that our intestine-specific ferroportin knockout mouse model of end-stage IDA could be used in future studies to investigate IDA progression and cell-specific responses to hypoxic and iron stress.

P6295Methotrexate reduces cardiac remodeling and improves left ventricle function in rats with Takotsubo cardiomyopathy

Abstract Introduction Takotsubo cardiomyopathy (TC) is characterized by cardiac disfunction and left ventricle (LV) remodeling caused, mainly, by physical or emotional stress. Previously, we have shown in atherosclerotic rabbits that methotrexate (MTX), an anti-inflammatory chemotherapeutic agent, is capable of reducing the inflammatory process and atherosclerotic lesions. Purpose To investigate the effect of MTX treatment in rats with TC. Methods TC was induced in Wistar rats with 2 injections of isoproterenol (85mg/kg) with a 24h interval. Animals were allocated in 3 experimental groups: CT: animals induced and treated with saline; TK: animal induced with isoproterenol and treated with saline; TK-MTX: animals induced with isoproterenol and treated with MTX (1mg/kg). Animals were treated every week for 4 weeks. After the treatment, echocardiography, morphometry and molecular analysis (Western blot) of the LV were performed. Results TK and TK-MTX groups did not show cardiac dilation or LV intraventricular septum and posterior wall thickening. However, compared to TK, the treatment with MTX improved both LV systolic and diastolic function. In addition, the treatment diminished myocytes diameter and subendocardial and interstitial fibrosis of the LV. Protein expression of pro-apoptotic factors (caspase 3 and BAX), pro-inflammatory cytokine TNF-α, metalloproteinase 2, transforming growth factor beta, collagen I and III and hypoxia-inducible factor 2 alfa were all decreased. Vascular endothelial growth factor (VEGF) and adenosine A1 receptor showed increased protein expression in TK-MTX group when compared to CT and TK. There was correlation of myocardial fibrosis (r2=-0.57), myocytes diameter (r2=-0.78) and VEGF expression (r2=0.58) with LV systolic disfunction. Also, myocardial fibrosis (r2=0.57) and VEGF expression (r2=-0.68) correlated with diastolic disfunction in the LV. Animals treated with MTX did not present any toxicity. Conclusion Treatment with MTX diminished apoptosis, the expression of TNF-α and metalloproteinases, cardiac hypertrophy and myocardial fibrosis. Besides that, the treatment increased angiogenesis and strongly improved cardiac function of the LV. MTX, possibly through an increase in the production of intracellular adenosine, could be considered as a feasible treatment for TC. Acknowledgement/Funding FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo)

Cardiomyocyte d-dopachrome tautomerase protects against heart failure.

The mechanisms contributing to heart failure remain incompletely understood. d-dopachrome tautomerase (DDT) is a member of the macrophage migration inhibitory factor family of cytokines and is highly expressed in cardiomyocytes. This study examined the role of cardiomyocyte DDT in the setting of heart failure. Patients with advanced heart failure undergoing transplantation demonstrated decreased cardiac DDT expression. To understand the effect of loss of cardiac DDT in experimental heart failure, cardiomyocyte-specific DDT-KO (DDT-cKO) and littermate control mice underwent surgical transverse aortic constriction (TAC) to induce cardiac pressure overload. DDT-cKO mice developed more rapid cardiac contractile dysfunction, greater cardiac dilatation, and pulmonary edema after TAC. Cardiomyocytes from DDT-cKO mice after TAC had impaired contractility, calcium transients, and reduced expression of the sarcoplasmic reticulum calcium ATPase. The DDT-cKO hearts also exhibited diminished angiogenesis with reduced capillary density and lower VEGF-A expression after TAC. In pharmacological studies, recombinant DDT (rDDT) activated endothelial cell ERK1/2 and Akt signaling and had proangiogenic effects in vitro. The DDT-cKO hearts also demonstrated more interstitial fibrosis with enhanced collagen and connective tissue growth factor expression after TAC. In cardiac fibroblasts, rDDT had an antifibrotic action by inhibiting TGF-β-induced Smad-2 activation. Thus, endogenous cardiomyocyte DDT has pleiotropic actions that are protective against heart failure.

Cardiovascular Magnetic Resonance Imaging Evidence of Edema in Chronic Chagasic Cardiomyopathy

The persistence of inflammatory processes in the myocardium in varying degrees of chronic Chagas heart disease has been poorly investigated. We hypothesized that edema could occur in patients with chronic chagasic cardiomyopathy and corresponds to the persistence of inflammatory processes in the myocardium. Eighty-two Chagas disease (CD) seropositive patients (64.6% females; age = 58.9 ± 9.9) without ischemic heart disease or conditions that cause myocardial fibrosis and dilation were considered. Late gadolinium enhancement (LGE) and T2-weighted magnetic resonance imaging of edema were obtained and represented using a 17-segment model. Patients were divided into three clinical groups according to the left ventricular (LV) ejection fraction (EF) as G1 (EF > 60%; n=37), G2 (35% > EF < 60%; n=33), and G3 (EF < 35%; n=12). Comparisons were performed by the Fisher or ANOVA tests. Bonferroni post hoc, Spearman correlation, and multiple correspondence analyses were also performed. Edema was observed in 8 (9.8%) patients; 2 (5.4%) of G1, 4 (12.1%) of G2, and 2 (16.7%) of G3. It was observed at the basal inferolateral segment in 7 (87.5%) cases. LGE was observed in 48 (58.5%) patients; 16 (43.2%) of G1, 21 (63.6%) of G2, and 11 (91.7%) of G3 (p < 0.05). It was observed in the basal inferior/inferolateral/anterolateral segments in 35 (72.9%) patients and in the apical anterior/inferior/lateral and apex segments in 21 (43.7%), with midwall (85.4%; n=41), subendocardial (56.3%; n=27), subepicardial (54.2%; n=26), transmural (31.2%; n=15), and RV (1.2%; n=1) distribution. Subendocardial lesions were observed only in patients with LVEF < 35%. There was no involvement of the mid-inferolateral/anterolateral segments with an LVEF > 35% (p < 0.05). Deteriorations of the LV and RV systolic functions were positively correlated (rs=0.69; p < 0.05) without evidence of LGE in the RV. Edema can be found in patients with chagasic cardiomyopathy in the chronic stage. In later stages of cardiac dilation with low LVEF, the LGE pattern involves subendocardium and mid locations. Deteriorations of RV and LV are positively correlated without evidence of fibrosis in the RV.

Abstract P2003: Loss of Trpa1 in Mice Leads to Age-Related Dilated Cardiomyopathy

Activation of the transient receptor potential ankyrin 1 (TRPA1) channel, a mechanical and oxidative stress sensor, has been shown to slow down aging process and promote longevity in invertebrate animal models like Caenorhabditis elegans . Although physiologic sensory functions of TRPA1 are conservative across species, the role of TRPA1 in regulation of organ development and function in mammals in the aging process is unknown. The present study tests the hypothesis that TRPA1 ablation leads to cardiac dilation and cardiomyopathy in aging mice. Echocardiography was performed in male 12-week-old (young) and 52-week-old (older) Trpa1 gene knockout ( Trpa1 -/- ) mice and wild-type (WT) littermates on a mixed C57BL/6 x 129 genetic background. Echocardiogram data showed that, compared to young WT littermates, young Trpa1 -/- mice had similar cardiac dimensions and left ventricular function, as demonstrated by left ventricular end-diastolic internal dimension (LVIDd, WT 4.29±0.62 vs. Trpa1 -/- 4.50±0.41 mm, P&gt;0.05), left ventricular ejection fraction (LVEF, a parameter of systolic function, WT 66.73±9.50 vs. Trpa1 -/- 63.39±12.76 %, P&gt;0.05), and E/A ratio (a parameter of diastolic function, WT 1.23±0.03 vs. Trpa1 -/- 1.39±0.14, P&gt;0.05). In contrast, older Trpa1 -/- mice developed dilated cardiomyopathy with dilated left ventricle (LVIDd: WT 4.60±0.16 vs. Trpa1 -/- 5.00±0.37 mm, P&lt;0.05) and impaired left ventricular systolic function (LVEF: WT 58.04±9.27 vs. Trpa1 -/- 41.79±7.19 %, P&lt;0.05) when compared to older WT mice. In addition, older Trpa1 -/- mice had impaired left ventricular myocardial performance index (LV MPI, a parameter of ventricular systolic and diastolic function, WT 0.62±0.15 vs. Trpa1 -/- 0.89±0.18, P&lt;0.05) albeit left ventricular diastolic function was not different between old Trpa1 -/- and WT mice (E/A ratio: WT 1.53±0.22 vs. Trpa1 -/- 1.99±0.92, P&gt;0.05). These results show that genetic knockout of TRPA1 leads to age-related left ventricular dilation and systolic dysfunction. These findings suggest that TRPA1 activation protects against age-related dilated cardiomyopathy.

Lessons learned from testing cardiac channelopathy and cardiomyopathy genes in individuals who died suddenly: A two-year prospective study in a large medical examiner's office with an in-house molecular genetics laboratory and genetic counseling services.

This is a comprehensive review and analysis of 254 cases tested consecutively in the in-house College of American Pathologist-accredited molecular genetics laboratory within the New York City Office of Chief Medical Examiner between October 2015 and February 2018, using a multigene cardiac panel composed of 95 genes associated with cardiac channelopathy and cardiomyopathy. Demographics, autopsy findings, medical history, and postmortem genetic testing results were collected for each case. The majority of decedents were adults (>25years old, 52.7%), followed by infants (<12months, 25.6%), young adults (19-25years old, 11.4%), and children (1-18years old, 10.2%). There were more males (64.2%) than females (35.8%). The racial/ethnic composition of decedents was 40.2% Black, 29.9% Hispanic, 22.4% White, 5.1% Asian/Pacific Islander, and 2.8% mixed/unspecified. Overall, 45.7% of decedents had a negative autopsy, and the remaining had one to four cardiac findings (cardiac hypertrophy, dilation, atherosclerosis, and fatty change). Twenty-seven pathogenic/likely pathogenic variants (P/LP) and 99 variants of uncertain significance (VUS) were identified in 10.6% and 39% of decedents respectively. P/LP and VUS were found in 51 cardiac genes of the total 95 genes, where MYBPC3, TTN (predicted truncating variants), KCNH2, RYR2 and DSP genes had more than two P/LP variants identified. Among the 73 decedents who were suspected of having cardiac arrhythmia or cardiomyopathy, 20.3% had P/LP variants and 47.9% had VUS; among 23 decedents who had hypertensive cardiovascular diseases and 20 decedents with a history of substance use, 13% and 30% had P/LP variants, respectively. There were 26 referrals from medical examiners for genetic counseling and the outcomes are discussed. The study demonstrates characteristics of the diverse population typically seen by medical examiners in an urban center and our results support a broader implementation of molecular testing in sudden death.

Abstract 249: ERBB2 and beta-1-Adrenergic Receptor Cross-talk Underlies Cardiac Dysfunction

ERBB2 is a member of the EGFR growth factor receptor family and a primary target for anti-cancer treatment in patients diagnosed with breast cancer. ERBB2 targeting is known to cause cardiotoxicity, resulting in cardiac dilation while, less is understood about the underlying mechanisms. Studies have shown a direct co-relationship between beta2-adrenergic receptors (β2ARs) and ERBB2 in the cardiac hypertrophy wherein increased ERBB2 expression is associated with elevated β2ARs. Given the key role of β1ARs in cardiac function, we assessed potential cross-talk between ERBB2 and β1ARs. Towards this end, we have used a transgenic mouse model of cardiomyocyte-specific overexpression of microRNA-7 (miR-7 Tg) that abrogates ERBB2 expression in the adult cardiomyocytes and associated with cardiac dilation. Radio-ligand binding in miR-7 Tg hearts showed selective increase in β1AR density with no changes in the β2ARs. In contrast, cardiomyocyte-specific overexpression of ERBB2 results cardiac hypertrophy and is associated with significant increase in β2AR density with no changes in β1ARs. These observations show that ERBB2 expression may differentially regulate β1AR versus β2AR providing a unique role for ERBB2 in cardiac physiology. Further, ERBB2 expression is elevated in an age-dependent manner in C57BL6 mice that may account for hypertrophic response. Consistently, miR-7 Tg mice have age-dependent cardiac dilation consistent with the loss in the ERBB2 expression. To test for such a role, C57BL6 mice were administered vehicle, AG1875 (EGFR inhibitor) or AG825 (ERBB2 inhibitor) for two weeks to assess for changes in cardiac function. Administration of AG825 resulted significant cardiac dysfunction and dilation compared to AG1875 or vehicle controls, conferring the idea that inhibition of ERBB2 and not EGFR that mediates deleterious remodeling. Proteomic analysis showed dramatic differences in the associated proteins following AG825 compared to vehicle or AG1478 and our presentation will elucidate the results on how homeostatic ERBB2 signaling and expression is key for cardiac function and how chemotherapeutic inhibition of ERBB2 underlies deleterious pathways leading to cardiotoxicity.

Abstract 944: Differential Dna Methylation Co-segregates With the Severity of Heart Failure

Heart failure (HF) is a leading cause of morbidity and mortality worldwide. As a potential epigenetic biomarker, DNA methylation differs between healthy and diseased hearts. However, its association according to disease severity has not yet been studied. Here, we sought to investigate how DNA methylation (DNAm) differs across HF disease severity, and study the use of a DNMT methyltransferase inhibitor RG108 on DNAm and its effect on heart function. A fixed dose of Isoprenaline (ISO), or saline control (SAL), administered to a hybrid mouse diversity panel (HMDP) consisting of 85 classical and recombinant inbred mouse strains produced a range of cardiac hypertrophy and/or LV dilatation. Left ventricles were harvested and subjected to genome-wide cardiac DNAm profiling by Reduced Representation Bisulfite Sequencing (RRBS). Unsupervised clustering of the top 1% most variable CpG methylation segregated strains to their genetic origin. Disregarding strain-specific methylation differences, differential methylation between ISO and SAL unexpectedly categorised mice into mild and severe disease responders. In the severe-responder strain BTBRT, the pharmacological DNMT methyltransferase inhibitor, RG108, rescued disease from ISO-response, with accompanying evidence of gene expression recovery. This work establishes the range of cardiac differential DNAm correlating according to disease severity. It displays the involvement of DNA methylation-dependent gene expression changes that turns out to be unique, despite different mouse strain backgrounds. This gives further proof of principle that cardiac DNAm changes represent novel biomarkers for disease stratification and consequent targeted therapy.

Abstract 252: Activated Fibroblast-specific Deletion of RhoA Reduces Cardiac Fibrosis Through Regulation of the Non-canonical p38-MAPK Signaling Pathway

Objective: Heart failure is a progressive disease characterized by cardiomyocyte (CM) loss, interstitial fibrosis, loss of ventricular compliance and chamber remodeling. Role of cardiac fibroblasts is implicated in the process, but specific molecular mechanisms regulating their function remain unclear. Previously, we showed that in mice, in response to stress, CM-specific deletion of RhoA, a Ras-related small G protein, accelerated cardiac dilation, with significant loss of contractile function, but it also significantly reduced cardiac fibrosis. Therefore, here, we focused on understanding the role of RhoA specifically in myofibroblast transformation and the fibrotic response. Results: We generated mice with activated fibroblast-specific deletion of RhoA using a tamoxifen (TMX) inducible periostin-cre promoter (RhoAfl/fl::PSTN Cre/+). 10-wk-old male RhoAfl/fl::PSTN Cre/+ or control mice were treated with angiotensin-phenylephrine (AngPE) or saline for 4 wk using osmotic minipumps and fed either with TMX or regular diet. Following TMX-AngPE treatment, the RhoAfl/fl::PSTN Cre/+ mice showed significantly decreased cardiac fibrosis, as compared to controls (0.9% vs. 3.2%, respectively). Moreover, while overall cardiac function following AngPE treatment was similar at 4 wk in all groups, hearts from the TMX-RhoAfl/fl::PSTN Cre/+ mice had significantly reduced septal thickness, as compared to controls. Expression of fetal genes, ANF, BNP, and β-MHC, as well as markers of fibrosis, including α-SMA and CTGF, were similarly induced in control and TMX-RhoAfl/fl::PSTN Cre/+ mice. However, TMX-RhoAfl/fl::PSTN Cre/+ mice had reduced expression of TGF-β1, thrombospondin-5 and Col1a2. Finally, RhoA deletion in activated fibroblasts did not affect the canonical TGFβ signaling pathway, as expected; instead, we found TMX-RhoAfl/fl::PSTN Cre/+ hearts had reduced non-canonical p38-MAPK signaling, suggestive of cellular-specific effects of RhoA regulation in the onset of cardiac disease and fibrosis. Conclusions: These data confirm the primacy of the RhoA pathway in the fibrotic response in vivo and identify potential novel downstream targets and possible therapeutic strategies for treatment of cardiac fibrosis and heart failure.

Outbreaks of nutritional cardiomyopathy in pigs in Brazil

ABSTRACT: Dilated cardiomyopathy (DCM) is a condition that affects the myocardium, seldom reported in pigs. The DCM is characterized by ventricular dilation, which results in systolic and secondary diastolic dysfunction and can lead to arrhythmia and fatal congestive heart failure. This study described the clinical, pathological, chemical and toxicological findings of nutritional dilated cardiomyopathy (DCM) in nursery pigs through natural and experimental studies. Naturally occurring cases of DCM in three swine farms were investigated through necropsy (fourteen pigs), microscopic, virological, chemical and toxicological exams for the detection of the etiology. The experimental study was conducted with nine 40 days-old piglets, which were divided into three groups of three piglets each. Group 1 was fed with the suspected diet of the naturally occurring cases, Group 2 with half of the suspected diet and half of a control diet, and Group 3 received only the control diet. Clinical signs were recorded. All pigs were submitted of euthanized, necropsie and collection sample for laboratories exams, after 15 days of experiment onset. At the necropsy, all naturally occurring cases had bilateral cardiac dilatation associated to hepatic enhanced lobular pattern (nutmeg liver) and lungs edema. Microscopically, the heart revealed severe hypertrophy and vacuolization of cardiomyocytes, as well as myofiber disarray. Feed analysis revealed low-quality standard soybean meal. After the suspected feed was replaced, clinically ill pigs recovered, and mortality ceased. At the experimental study, two piglets from Group 1 had cough, dyspnea and diarrhea. At the necropsy, these animals had similar gross and microscopic lesions to the natural cases. The nutritional DCM in pigs may be associated to the diet with low-quality soybean meal, as it was further confirmed through an experimental study.

Expression of Normally Repressed Myosin Heavy Chain 7b in the Mammalian Heart Induces Dilated Cardiomyopathy.

BackgroundIn mammals, muscle contraction is controlled by a family of 10 sarcomeric myosin motors. The expression of one of its members, MYH7b, is regulated by alternative splicing, and while the protein is restricted to specialized muscles such as extraocular muscles or muscle spindles, RNA that cannot encode protein is expressed in most skeletal muscles and in the heart. Remarkably, birds and snakes express MYH7b protein in both heart and skeletal muscles. This observation suggests that in the mammalian heart, the motor activity of MYH7b may only be needed during development since its expression is prevented in adult tissue, possibly because it could promote disease by unbalancing myocardial contractility.Methods and ResultsWe have analyzed MYH7b null mice to determine the potential role of MYH7b during cardiac development and also generated transgenic mice with cardiac myocyte expression of MYH7b protein to measure its impact on cardiomyocyte function and contractility. We found that MYH7b null mice are born at expected Mendelian ratios and do not have a baseline cardiac phenotype as adults. In contrast, transgenic cardiac MYH7b protein expression induced early cardiac dilation in males with significantly increased left ventricular mass in both sexes. Cardiac dilation is progressive, leading to early cardiac dysfunction in males, but later dysfunction in females.ConclusionsThe data presented show that the expression of MYH7b protein in the mammalian heart has been inhibited during the evolution of mammals most likely to prevent the development of a severe cardiomyopathy that is sexually dimorphic.

The extracellular matrix proteoglycan lumican improves survival and counteracts cardiac dilatation and failure in mice subjected to pressure overload

Left ventricular (LV) dilatation is a key step in transition to heart failure (HF) in response to pressure overload. Cardiac extracellular matrix (ECM) contains fibrillar collagens and proteoglycans, important for maintaining tissue integrity. Alterations in collagen production and cross-linking are associated with cardiac LV dilatation and HF. Lumican (LUM) is a collagen binding proteoglycan with increased expression in hearts of patients and mice with HF, however, its role in cardiac function remains poorly understood. To examine the role of LUM in pressure overload induced cardiac remodeling, we subjected LUM knock-out (LUMKO) mice to aortic banding (AB) and treated cultured cardiac fibroblasts (CFB) with LUM. LUMKO mice exhibited increased mortality 1–14 days post-AB. Echocardiography revealed increased LV dilatation, altered hypertrophic remodeling and exacerbated contractile dysfunction in surviving LUMKO 1–10w post-AB. LUMKO hearts showed reduced collagen expression and cross-linking post-AB. Transcriptional profiling of LUMKO hearts by RNA sequencing revealed 714 differentially expressed transcripts, with enrichment of cardiotoxicity, ECM and inflammatory pathways. CFB treated with LUM showed increased mRNAs for markers of myofibroblast differentiation, proliferation and expression of ECM molecules important for fibrosis, including collagens and collagen cross-linking enzyme lysyl oxidase. In conclusion, we report the novel finding that lack of LUM attenuates collagen cross-linking in the pressure-overloaded heart, leading to increased mortality, dilatation and contractile dysfunction in mice.

Indirect Blood Pressure Measurement in Horses: Is There an Influence of Age, Sex, Breed, Bodyweight, and Cardiac Diseases on Pressure Values?

Only few data regarding normal resting blood pressure in horses and the influence of cardiac diseases on arterial blood pressure are available in literature. The purpose of the present study was to investigate the possible influence of age, sex, breed, bodyweight, and cardiac diseases and their severity on blood pressure values measured in horses with cardiac disease and in a control group. For this case-control study, indirect blood pressure measurement was performed in 60 horses with different types of cardiac disease and in 23 healthy horses (control group), by means of an ultrasonic blood-flow technique. According to the echocardiographic findings, horses with cardiac abnormalities have been divided into two groups (with and without cardiac dimensional modifications). Multivariable linear regression analysis evaluated the influence of age, breed, sex, and cardiac diseases and their severity (regressors) on blood pressure. The results showed a significant influence of age on diastolic pressure in healthy horses. Furthermore, a significant influence of the presence of cardiac dilation in horses with cardiac disease on systolic and diastolic pressures was found. Single-regressor linear analysis showed that horses with cardiac dilation are significantly older than both horses without cardiac dimensional changes and those of control group. Further studies are necessary to better investigate the possible influence of the type of cardiac disease on blood pressure.

Relaxin mitigates microvascular damage and inflammation following cardiac ischemia-reperfusion.

Microvascular obstruction (MVO) and leakage (MVL) forms a pivotal part of microvascular damage following cardiac ischemia-reperfusion (IR). We tested the effect of relaxin therapy on MVO and MVL in mice following cardiac IR injury including severity of MVO and MVL, opening capillaries, infarct size, regional inflammation, cardiac function and remodelling, and permeability of cultured endothelial monolayer. Compared to vehicle group, relaxin treatment (50μg/kg) reduced no-reflow area by 38% and the content of Evans blue as a permeability tracer by 56% in jeopardized myocardium (both P < 0.05), effects associated with increased opening capillaries. Relaxin also decreased leukocyte density, gene expression of cytokines, and mitigated IR-induced decrease in protein content of VE-cadherin and relaxin receptor. Infarct size was comparable between the two groups. At 2weeks post-IR, relaxin treatment partially preserved cardiac contractile function and limited chamber dilatation versus untreated controls by echocardiography. Endothelial cell permeability assay demonstrated that relaxin attenuated leakage induced by hypoxia-reoxygenation, H2O2, or cytokines, action that was independent of nitric oxide but associated with the preservation of VE-cadherin. In conclusion, relaxin therapy attenuates IR-induced MVO and MVL and endothelial leakage. This protection was associated with reduced regional inflammatory responses and consequently led to alleviated adverse cardiac remodeling.