Myocardial fibrosis in chronic aortic regurgitation: molecular and cellular responses to volume overload

Left Ventricular Reverse Remodeling after Surgical Aortic Valve Replacement for Aortic Regurgitation-An Explorative Study

BACKGROUND

The timing of treatment for chronic aortic valve regurgitation (AR), especially in asymptomatic patients, is gaining attention since less invasive strategies have become available. The aim of the present study was to evaluate left ventricular reverse remodeling after aortic valve replacement (AVR) for severe AR.

METHODS

Patients (n = 25) who underwent surgical AVR for severe AR with left ventricular ejection fraction (LVEF) less than 55% were included in this study. Preprocedural and follow-up clinical and echocardiographic measurements of LVEF and left ventricular (LV) diameters were retrospectively analyzed.

RESULTS

Mean LVEF increased significantly following surgical AVR (p < 0.0001). LV diameters showed a clear regression (p = 0.0088). Younger patients and those receiving a mechanical valve tended to have less improved LVEF on follow-up than patients over 60 years or the ones who were implanted with a biological prosthesis (p = 0.0239 and p = 0.069, respectively). Gender had no effect on the degree of LVEF improvement (p = 0.4908).

CONCLUSIONS

We demonstrated significant LV reverse remodeling following AVR for AR. However, more data are needed on LV functional and geometrical improvement comparing the different types of valve prostheses to provide an optimal treatment strategy.

Aortic Regurgitation in Bicuspid Aortic Valve: The Role of Multimodality Imaging

The evaluation of aortic regurgitation (AR) in bicuspid valve (BAV) is still a challenge because of the eccentricity of the jet, which may under/overestimate the regurgitation. The commonly used echocardiography parameters (such as vena contracta, pressure half-time, etc.) may not be useful in this kind of patient. A multimodality approach combining echocardiography, cardiac MRI, cardiac CT, and advanced technologies applied to non-invasive cardiac imaging (e.g., 4D flow and strain imaging) may be useful to better quantify regurgitation and to select patients suitable for valve replacement. This review provides an overview of the most recent insights about cardiovascular imaging tools and their utility in BAV evaluation, focusing on chronic regurgitation. We describe the role of multimodality imaging in both diagnosis and risk assessment of this disease, pointing out the advantages and disadvantages of the imaging techniques, aiming to provide a guide to clinicians and cardiovascular imaging specialists in choosing the best imaging tools to use.

Left ventricular reverse remodeling after aortic valve replacement or repair in bicuspid aortic valve with moderate or greater aortic regurgitation

Objective

Bicuspid aortic valve (AV) patients with aortic regurgitation (AR) differ from tricuspid AV patients given younger age, greater left ventricle (LV) compliance, and more prevalent aortic stenosis (AS). Bicuspid AV-specific data to guide timing of AV replacement or repair are lacking.

Methods

Adults with bicuspid AV and moderate or greater AR who underwent aortic valve replacement or repair at our center were studied. The presurgical echocardiogram, and echocardiograms within 3 years postoperatively were evaluated for LV geometry/function, and AV function. Semiquantitative AS/AR assessment was performed in all patients with adequate imaging.

Results

One hundred thirty-five patients (85% men, aged 44.5 ± 15.9 years) were studied (63% pure AR, 37% mixed AS/AR). Following aortic valve replacement or repair, change in LV end-diastolic dimension and change in LV end-diastolic volume were associated with preoperative LV end-diastolic dimension (β = 0.62 Δcm/cm; 95% CI, 0.43-0.73 Δcm/cm; P < .001), and LV end-diastolic volume (β = 0.6 ΔmL/mL; 95% CI, 0.4-0.7 ΔmL/mL; P < .001), respectively, each independent of AR/AS severity (P = not significant). Baseline LV size predicted postoperative normalization (LV end-diastolic dimension: odds ratio, 3.75/cm; 95% CI, 1.61-8.75/cm, LV end-diastolic volume: odds ratio, 1.01/mL; 95% CI, 1.004-1.019/mL, both P values < .01) whereas AR/AS severity did not (P = not significant). Indexed LV end diastolic volume outperformed LV end-diastolic dimension in predicting postoperative LV normalization (area under the curve = 0.74 vs 0.61) with optimal diagnostic cutoffs of 99 mL/m2 and 6.1 cm, respectively. Postoperative indexed LV end diastolic volume dilatation was associated with increased risk of death, transplant/ventricular assist device, ventricular arrhythmia, and reoperation (hazard ratio, 6.1; 95% CI, 1.7-21.5; P < .01).

Conclusions

Remodeling extent following surgery in patients with bicuspid AV and AR relates to preoperative LV size independent of valve disease phenotype or severity. Many patients with LV end-diastolic dimension below current surgical thresholds did not normalize LV size. LV volumetric assessment offered superior diagnostic performance for predicting residual LV dilatation, and postoperative indexed LV end diastolic volume dilatation was associated with adverse prognosis.

Assessing Regurgitation Severity, Adverse Remodeling, and Fibrosis with CMR in Aortic Regurgitation

PURPOSE OF REVIEW

Cardiac magnetic resonance (CMR) is emerging as a valuable imaging modality for the assessment of aortic regurgitation (AR). In this review, we discuss the assessment of AR severity, left ventricular (LV) remodeling, and tissue characterization by CMR while highlighting the latest studies and addressing future research needs.

RECENT FINDINGS

Recent studies have further established CMR-based thresholds of AR severity and LV remodeling that are associated with adverse clinical outcomes, and lower than current guideline criteria. In addition, tissue profiling with late gadolinium enhancement (LGE) and extracellular volume (ECV) quantification can reliably assess adverse myocardial tissue remodeling which is also associated with adverse outcomes. The strengths and reproducibility of CMR in evaluating ventricular volumes, tissue characteristics, and regurgitation severity position it as an excellent modality in evaluating and following AR patients. Advanced CMR techniques for the detection of tissue remodeling have shown significant potential and merit further investigation.

CDC-like kinase 3 deficiency aggravates hypoxia-induced cardiomyocyte apoptosis through AKT signaling pathway

Hypoxia-induced cardiomyocyte apoptosis is one major pathological change of acute myocardial infarction (AMI), but the underlying mechanism remains unexplored. CDC-like kinase 3 (CLK3) plays crucial roles in cell proliferation, migration and invasion, and nucleotide metabolism, however, the role of CLK3 in AMI, especially hypoxia-induced apoptosis, is largely unknown. The expression of CLK3 was elevated in mouse myocardial infarction (MI) models and neonatal rat ventricular myocytes (NRVMs) under hypoxia. Furthermore, CLK3 knockdown significantly promoted apoptosis and inhibited NRVM survival, while CLK3 overexpression promoted NRVM survival and inhibited apoptosis under hypoxic conditions. Mechanistically, CLK3 regulated the phosphorylation status of AKT, a key player in the regulation of apoptosis. Furthermore, overexpression of AKT rescued hypoxia-induced apoptosis in NRVMs caused by CLK3 deficiency. Taken together, CLK3 deficiency promotes hypoxia-induced cardiomyocyte apoptosis through AKT signaling pathway.

Left ventricular ejection fraction: clinical, pathophysiological, and technical limitations

Risk stratification of cardiovascular death and treatment strategies in patients with heart failure (HF), the optimal timing for valve replacement, and the selection of patients for implantable cardioverter defibrillators are based on an echocardiographic calculation of left ventricular ejection fraction (LVEF) in most guidelines. As a marker of systolic function, LVEF has important limitations being affected by loading conditions and cavity geometry, as well as image quality, thus impacting inter- and intra-observer measurement variability. LVEF is a product of shortening of the three components of myocardial fibres: longitudinal, circumferential, and oblique. It is therefore a marker of global ejection performance based on cavity volume changes, rather than directly reflecting myocardial contractile function, hence may be normal even when myofibril's systolic function is impaired. Sub-endocardial longitudinal fibers are the most sensitive layers to ischemia, so when dysfunctional, the circumferential fibers may compensate for it and maintain the overall LVEF. Likewise, in patients with HF, LVEF is used to stratify subgroups, an approach that has prognostic implications but without a direct relationship. HF is a dynamic disease that may worsen or improve over time according to the underlying pathology. Such dynamicity impacts LVEF and its use to guide treatment. The same applies to changes in LVEF following interventional procedures. In this review, we analyze the clinical, pathophysiological, and technical limitations of LVEF across a wide range of cardiovascular pathologies.

Assessment of the Severity of Aortic Regurgitation by Noninvasive Imaging : Non-invasive MMI for AR

PURPOSE OF THE REVIEW

The role of multimodality imaging in the evaluation of patients with aortic regurgitation is summarized in this review.

RECENT FINDINGS

The etiology (mechanism) of the aortic regurgitation and the severity of aortic regurgitation and hemodynamic consequences are key in the decision making of patients with severe aortic regurgitation. While echocardiography remains as the leading technique to assess all these parameters, other imaging techniques have become essential for the accurate assessment of aortic regurgitation severity and the timing of aortic intervention. The anatomic suitability of transcatheter aortic valve implantation in inoperable patients with severe aortic regurgitation is usually assessed with computed tomography. Aortic regurgitation is a prevalent disease with various pathophysiological mechanisms that need a personalized treatment. The evaluation of the mechanism and severity of aortic regurgitation can be initially performed with echocardiography. Three-dimensional techniques, including echocardiography, have become very relevant for accurate assessment of the regurgitation severity and its hemodynamic consequences. Assessment of myocardial tissue characteristics with cardiac magnetic resonance is key in the risk stratification of patients and in the timing of aortic intervention. Computed tomography is important in the assessment of aortic dimensions and selection of patients for transcatheter aortic valve implantation.

MicroRNA‑378: An important player in cardiovascular diseases (Review)

Cardiovascular disease (CVD) is a common chronic clinical condition and is the main cause of death in humans worldwide. Understanding the genetic and molecular mechanisms involved in the development of CVD is essential to develop effective prevention strategies and therapeutic measures. An increasing number of CVD‑related genetic studies have been conducted, including those on the potential roles of microRNAs (miRs). These studies have demonstrated that miR‑378 is involved in the pathological processes of CVD, including those of myocardial infarction, heart failure and coronary heart disease. Despite the potential importance of miR‑378 CVD, a comprehensive summary of the related literature is lacking. Thus, the present review aimed to summarize the findings of previous studies on the roles and mechanisms of miR‑378 in a variety of CVDs and provide an up‑to date basis for further r research targeting the prevention and treatment of CVDs.

Sex differences in myocardial remodeling and extracellular volume in aortic regurgitation

Whether sex differences exist in the cardiac remodeling related to aortic regurgitation (AR) is unclear. Cardiac magnetic resonance (CMR) is the current non-invasive reference standard for cardiac remodeling assessment and can evaluate tissue characteristics. This prospective cohort included patients with AR undergoing CMR between 2011 and 2020. We excluded patients with confounding causes of remodeling. We quantified left ventricular (LV) volume, mass, AR severity, replacement fibrosis by late Gadolinium enhancement (LGE), and extracellular expansion by extracellular volume fraction (ECV). We studied 280 patients (109 women), median age 59.5 (47.2, 68.6) years (P for age = 0.25 between sexes). Women had smaller absolute LV volume and mass than men across the spectrum of regurgitation volume (RVol) (P ≤ 0.01). In patients with ≥ moderate AR and with adjustment for body surface area, indexed LV end-diastolic volume and mass were not significantly different between sexes (all P > 0.5) but men had larger indexed LV end systolic volume and lower LV ejection fraction (P ≥ 0.01). Women were more likely to have NYHA class II or greater symptoms than men but underwent surgery at a similar rate. Prevalence and extent of LGE was not significantly different between sexes or across RVol. Increasing RVol was independently associated with increasing ECV in women, but not in men (adjusted P for interaction = 0.03). In conclusion, women had lower LV volumes and mass than men across AR severity  but their ECV increased with higher regurgitant volume, while ECV did not change in men. Indexing to body surface area did not fully correct for the cardiac remodeling differences between men and women. Women were more likely to have symptoms but underwent surgery at a similar rate to men. Further research is needed to determine if differences in ECV would translate to differences in the course of AR and outcomes.

Myocardial Fibrosis in Congenital Heart Disease and the Role of MRI

Progress in the field of congenital heart surgery over the last century can only be described as revolutionary. Recent improvements in patient outcomes have been achieved through refinements in perioperative care. In the current and future eras, the preservation and restoration of myocardial health, beginning with the monitoring of tissue remodeling, will be central to improving cardiac outcomes. Visualization and quantification of fibrotic myocardial remodeling is one of the greatest assets that cardiac MRI brings to the field of cardiology, and its clinical use within the field of congenital heart disease (CHD) has been an area of particular interest in the last few decades. This review summarizes the physical underpinnings of myocardial tissue characterization in CHD, with an emphasis on T1 parametric mapping and late gadolinium enhancement. It describes methods and suggestions for obtaining images, extracting quantitative and qualitative data, and interpreting the results for children and adults with CHD. The tissue characterization observed in different lesions is used to examine the causes and pathomechanisms of fibrotic remodeling in this population. Similarly, the clinical consequences of elevated imaging biomarkers of fibrosis on patient health and outcomes are explored. Keywords: Pediatrics, MR Imaging, Cardiac, Heart, Congenital, Tissue Characterization, Congenital Heart Disease, Cardiac MRI, Parametric Mapping, Fibrosis, Late Gadolinium Enhancement © RSNA, 2023.

Progress on role of ion channels of cardiac fibroblasts in fibrosis

Cardiac fibrosis is defined as excessive deposition of extracellular matrix (ECM) in pathological conditions. Cardiac fibroblasts (CFs) activated by injury or inflammation differentiate into myofibroblasts (MFs) with secretory and contractile functions. In the fibrotic heart, MFs produce ECM which is composed mainly of collagen and is initially involved in maintaining tissue integrity. However, persistent fibrosis disrupts the coordination of excitatory contractile coupling, leading to systolic and diastolic dysfunction, and ultimately heart failure. Numerous studies have demonstrated that both voltage- and non-voltage-gated ion channels alter intracellular ion levels and cellular activity, contributing to myofibroblast proliferation, contraction, and secretory function. However, an effective treatment strategy for myocardial fibrosis has not been established. Therefore, this review describes the progress made in research related to transient receptor potential (TRP) channels, Piezo1, Ca²⁺ release-activated Ca²⁺ (CRAC) channels, voltage-gated Ca²⁺ channels (VGCCs), sodium channels, and potassium channels in myocardial fibroblasts with the aim of providing new ideas for treating myocardial fibrosis.

Proteomic Insights into Cardiac Fibrosis: From Pathophysiological Mechanisms to Therapeutic Opportunities

Cardiac fibrosis is a common pathophysiologic process in nearly all forms of heart disease which refers to excessive deposition of extracellular matrix proteins by cardiac fibroblasts. Activated fibroblasts are the central cellular effectors in cardiac fibrosis, and fibrotic remodelling can cause several cardiac dysfunctions either by reducing the ejection fraction due to a stiffened myocardial matrix, or by impairing electric conductance. Recently, there is a rising focus on the proteomic studies of cardiac fibrosis for pathogenesis elucidation and potential biomarker mining. This paper summarizes the current knowledge of molecular mechanisms underlying cardiac fibrosis, discusses the potential of imaging and circulating biomarkers available to recognize different phenotypes of this lesion, reviews the currently available and potential future therapies that allow individualized management in reversing progressive fibrosis, as well as the recent progress on proteomic studies of cardiac fibrosis. Proteomic approaches using clinical specimens and animal models can provide the ability to track pathological changes and new insights into the mechanisms underlining cardiac fibrosis. Furthermore, spatial and cell-type resolved quantitative proteomic analysis may also serve as a minimally invasive method for diagnosing cardiac fibrosis and allowing for the initiation of prophylactic treatment.

The emerging importance of immunophilins in fibrosis development

Immunophilins are a family of proteins encompassing FK506-binding proteins (FKBPs) and cyclophilins (Cyps). FKBPs and Cyps exert peptidyl-prolyl cis-trans isomerase (PPIase) activity, which facilitates diverse protein folding assembly, or disassembly. In addition, they bind to immunosuppressant medications where FKBPs bind to tacrolimus (FK506) and rapamycin, whereas cyclophilins bind to cyclosporin. Some large immunophilins have domains other than PPIase referred to as tetratricopeptide (TPR) domain, which is involved in heat shock protein 90 (Hsp90) and heat shock protein 70 (Hsp 70) chaperone interaction. The TPR domain confers immunophilins’ pleotropic actions to mediate various physiological and biochemical processes. So far, immunophilins have been implicated to play an important role in pathophysiology of inflammation, cancer and neurodegenerative disorders. However, their importance in the development of fibrosis has not yet been elucidated. In this review we focus on the pivotal functional and mechanistic roles of different immunophilins in fibrosis establishment affecting various organs. The vast majority of the studies reported that cyclophilin A, FKBP12 and FKBP10 likely induce organ fibrosis through the calcineurin or TGF-β pathways. FKBP51 demonstrated a role in myelofibrosis development through calcineurin-dependant pathway, STAT5 or NF-κB pathways. Inhibition of these specific immunophilins has been shown to decrease the extent of fibrosis suggesting that immunophilins could be a novel promising therapeutic target to prevent or reverse fibrosis.

Molecular Approaches and Echocardiographic Deformation Imaging in Detecting Myocardial Fibrosis

The pathological remodeling of myocardial tissue is the main cause of heart diseases. Several processes are involved in the onset of heart failure, and the comprehension of the mechanisms underlying the pathological phenotype deserves special attention to find novel procedures to identify the site of injury and develop novel strategies, as well as molecular druggable pathways, to counteract the high degree of morbidity associated with it. Myocardial fibrosis (MF) is recognized as a critical trigger for disruption of heart functionality due to the excessive accumulation of extracellular matrix proteins, in response to an injury. Its diagnosis remains focalized on invasive techniques, such as endomyocardial biopsy (EMB), or may be noninvasively detected by cardiac magnetic resonance imaging (CMRI). The detection of MF by non-canonical markers remains a challenge in clinical practice. During the last two decades, two-dimensional (2D) speckle tracking echocardiography (STE) has emerged as a new non-invasive imaging modality, able to detect myocardial tissue abnormalities without specifying the causes of the underlying histopathological changes. In this review, we highlighted the clinical utility of 2D-STE deformation imaging for tissue characterization, and its main technical limitations and criticisms. Moreover, we focalized on the importance of coupling 2D-STE examination with the molecular approaches in the clinical decision-making processes, in particular when the 2D-STE does not reflect myocardial dysfunction directly. We also attempted to examine the roles of epigenetic markers of MF and hypothesized microRNA-based mechanisms aiming to understand how they match with the clinical utility of echocardiographic deformation imaging for tissue characterization and MF assessment.

The Role of Cardiac Magnetic Resonance in Aortic Stenosis and Regurgitation

Cardiac magnetic resonance (CMR) imaging is a well-set diagnostic technique for assessment of valvular heart diseases and is gaining ground in current clinical practice. It provides high-quality images without the administration of ionizing radiation and occasionally without the need of contrast agents. It offers the unique possibility of a comprehensive stand-alone assessment of the heart including biventricular function, left ventricle remodeling, myocardial fibrosis, and associated valvulopathies. CMR is the recognized reference for the quantification of ventricular volumes, mass, and function. A particular strength is the ability to quantify flow, especially with new techniques which allow accurate measurement of stenosis and regurgitation. Furthermore, tissue mapping enables the visualization and quantification of structural changes in the myocardium. In this way, CMR has the potential to yield important prognostic information predicting those patients who will progress to surgery and impact outcomes. In this review, the fundamentals of CMR in assessment of aortic valve diseases (AVD) are described, together with its strengths and weaknesses. This state-of-the-art review provides an updated overview of CMR potentials in all AVD issues, including valve anatomy, flow quantification, ventricular volumes and function, and tissue characterization.

MicroRNA-24-3p alleviates cardiac fibrosis by suppressing cardiac fibroblasts mitophagy via downregulating PHB2

Cardiac fibrosis is a pathological process of multiple cardiovascular diseases, which may lead to heart failure. Studies have shown that microRNAs (miRNAs) play critical roles in regulating mitophagy and cardiac fibrosis. We found that miR-24-3p expression was significantly downregulated in transverse aortic constriction (TAC) mice and cardiac fibroblasts (CFs) treated with Ang Ⅱ. We also found that, apart from improving cardiac structure and function, forced expression of miR-24-3p not only reduced the levels of collagen and α-SMA but also inhibited proliferation and migration of CFs. Next, our research proved that miR-24-3p suppressed the progression of mitophagy, autophagic flux, and the levels of mitophagy-related proteins in cardiac fibrosis models. Further analysis showed that PHB2 was a direct target of miR-24-3p. Finally, experiments showed that the knockdown of PHB2 reversed Ang Ⅱ-induced fibrosis in CFs. The results of our study suggests that increased expression of miR-24-3p contributes to the reduction of cardiac fibrosis and that it might be targeted therapeutically to alleviate cardiac fibrosis.

Corticotropin releasing hormone receptor 2 antagonist, RQ-00490721, for the prevention of pressure overload-induced cardiac dysfunction

BACKGROUND

G protein-coupled receptors (GPCRs) regulate the pathological and physiological functions of the heart. GPCR antagonists are widely used in the treatment of chronic heart failure. Despite therapeutic advances in the treatments for cardiovascular diseases, heart failure is a major clinical health problem, with significant mortality and morbidity. Corticotropin releasing hormone receptor 2 (CRHR2) is highly expressed in cardiomyocytes, and cardiomyocyte-specific deletion of the genes encoding CRHR2 suppresses pressure overload-induced cardiac dysfunction. This suggests that the negative modulation of CRHR2 may prevent the progression of heart failure. However, there are no systemic drugs against CRHR2.

FINDINGS

We developed a novel, oral, small molecule antagonist of CRHR2, RQ-00490721, to investigate the inhibition of CRHR2 as a potential therapeutic approach for the treatment of heart failure. In vitro, RQ-00490721 decreased CRHR2 agonist-induced 3', 5'-cyclic adenosine monophosphate (cAMP) production. In vivo, RQ-00490721 showed sufficient oral absorption and better distribution to peripheral organs than to the central nervous system. Oral administration of RQ-00490721 inhibited the CRHR2 agonist-induced phosphorylation of cAMP-response element binding protein (CREB) in the heart, which regulates a transcription activator involved in heart failure. RQ-00490721 administration was not found to affect basal heart function in mice but protected them from pressure overload-induced cardiac dysfunction.

INTERPRETATION

Our results suggest that RQ-00490721 is a promising agent for use in the treatment of chronic heart failure.

Low-dose PCB126 exposure disrupts cardiac metabolism and causes hypertrophy and fibrosis in mice

The residue of polychlorinated biphenyls (PCBs) exists throughout the environment and humans are subject to long-term exposure. As such, the potential environmental and health risk caused by low-dose exposure to PCBs has attracted much attention. 3, 3', 4, 4', 5-pentachlorobiphenyl (PCB126), the highest toxicity compound among dioxin-like-PCBs, has been widely used and mass-produced. Cardiotoxicity is PCB126's crucial adverse effect. Maintaining proper metabolism underlies heart health, whereas the impact of PCB126 exposure on cardiac metabolic patterns has yet to be elucidated. In this study, we administered 0.5 and 50 μg/kg bw of PCB126 to adult male mice weekly by gavage for eight weeks. Pathological results showed that low-dose PCB126 exposure induced heart injury. Metabolomic analysis of the heart tissue exposed to low-dose PCB126 identified 59 differential metabolites that were involved in lipid metabolism, amino acid metabolism, and the tricarboxylic acid (TCA) cycle. Typical metabolomic characteristic of cardiac hypertrophy was reflected by accumulation of fatty acids (e.g. palmitic, palmitoleic, and linoleic acid), and disturbance of carbohydrates including D-glucose and intermediates in TCA cycle (fumaric, succinic, and citric acid). Low-dose PCB126 exposure increased glycine and threonine, the amino acids necessary for the productions of collagen and elastin. Besides, PCB126-exposed mice exhibited upregulation of collagen synthesis enzymes and extracellular matrix proteins, indicative of cardiac fibrosis. Moreover, the expression of genes related to TGFβ/PPARγ/MMP-2 signaling pathway was perturbed in the PCB126-treated hearts. Together, our results reveal that low-dose PCB126 exposure disrupts cardiac metabolism correlated with hypertrophy and fibrosis. This study sheds light on the underlying mechanism of PCBs' cardiotoxicity and identifies potential sensitive biomarkers for environmental monitoring.

The Functions of LncRNA H19 in the Heart

Cardiovascular diseases (CVDs) are major causes of morbidity and mortality worldwide. Great effort has been put into exploring early diagnostic biomarkers and innovative therapeutic strategies for preventing CVD progression over the last two decades. Long non-coding RNAs (lncRNAs) have been identified as novel regulators in cardiac development and cardiac pathogenesis. For example, lncRNA H19 (H19), also known as a fetal gene abundant in adult heart and skeletal muscles and evolutionarily conserved in humans and mice, has a regulatory role in aortic aneurysm, myocardial hypertrophy, extracellular matrix reconstitution, and coronary artery diseases. Yet, the exact function of H19 in the heart remains unknown. This review summarises the functions of H19 in the heart and discusses the challenges and possible strategies of H19 research for cardiovascular disease.

Resveratrol against Cardiac Fibrosis: Research Progress in Experimental Animal Models

Cardiac fibrosis is a heterogeneous disease, which is characterized by abundant proliferation of interstitial collagen, disordered arrangement, collagen network reconstruction, increased cardiac stiffness, and decreased systolic and diastolic functions, consequently developing into cardiac insufficiency. With several factors participating in and regulating the occurrence and development of cardiac fibrosis, a complex molecular mechanism underlies the disease. Moreover, cardiac fibrosis is closely related to hypertension, myocardial infarction, viral myocarditis, atherosclerosis, and diabetes, which can lead to serious complications such as heart failure, arrhythmia, and sudden cardiac death, thus seriously threatening human life and health. Resveratrol, with the chemical name 3,5,4'-trihydroxy-trans-stilbene, is a polyphenol abundantly present in grapes and red wine. It is known to prevent the occurrence and development of cardiovascular diseases. In addition, it may resist cardiac fibrosis through a variety of growth factors, cytokines, and several cell signaling pathways, thus exerting a protective effect on the heart.

Cardiac fibrosis and curcumin: a novel perspective on this natural medicine

BACKGROUND

According to WHO statistics, cardiovascular disease are the leading causes of death in the world. One of the main factors which is causing heart failure, systolic and diastolic dysfunction, and arrythmias is a condition named cardiac fibrosis. This condition is defined by the accumulation of fibroblast-produced ECM in myocardium layer of the heart.

OBJECTIVE

Accordingly, the current review aims to depict the role of curcumin in the regulation of different signaling pathways that are involved in cardiac fibrosis.

RESULTS

A great number of cellular and molecular mechanisms such as oxidative stress, inflammation, and mechanical stress are acknowledged to be involved in cardiac fibrosis. Despite the available therapeutic procedures which are designed to target these mechanisms in order to prevent cardiac fibrosis, still, effective therapeutic methods are needed. Curcumin is a natural Chinese medicine which currently has been declared to have therapeutic properties such as anti-oxidant and immunomodulatory activities. In this review, we have gathered several experimental studies in order to represent diverse impacts of this turmeric derivative on pathogenic factors of cardiac fibrosis.

CONCLUSION

Curcumin might open new avenues in the field of cardiovascular treatment.

E2F transcription factor 1 (E2F1) promotes the transforming growth factor TGF-β1 induced human cardiac fibroblasts differentiation through promoting the transcription of CCNE2 gene

The differentiation of cardiac fibroblast to myofibroblast is the key process of cardiac fibrosis. In the study, we aimed to determine the function of E2F Transcription Factor 1 (E2F1) in human cardiac fibroblasts (HCFs) differentiation, search for its downstream genes and elucidate the function of them in HCFs differentiation. As a result, we found that E2F1 was up-regulated in TGF-β1-induced HCFs differentiation. Silencing the expression of E2F1 by siRNA in HCFs, we found that the expression of differentiation-related genes (Collagen-1, α-Smooth muscle actin, and Fibronectin-1) was significantly suppressed, combining with proliferation and migration assay, we determined that HCFs differentiation was decreased. Luciferase report assay and immunoprecipitation proved that the oncogene CCNE2 was a direct target gene of E2F1, overexpression of CCNE2 was found in differentiated HCFs, silencing the expression of CCNE2 by siRNA decreased HCFs differentiation. Our research suggested that E2F1 and its downstream target gene CCNE2 play a vital role in TGF-β1-induced HCFs differentiation, thus E2F1 and CCNE2 may be a potential therapeutic target for cardiac fibrosis.

Regional Replacement and Diffuse Interstitial Fibrosis in Aortic Regurgitation: Prognostic Implications From Cardiac Magnetic Resonance

OBJECTIVES

This study used cardiac magnetic resonance (CMR) to assess left ventricular (LV) remodeling in chronic aortic regurgitation (AR) to identify both forms of myocardial fibrosis and examine its association with clinical outcomes.

BACKGROUND

Chronic AR leads to LV remodeling, which is associated with 2 forms of myocardial fibrosis: regional replacement fibrosis that is directly imaged by late gadolinium enhancement (LGE) CMR; and diffuse interstitial fibrosis, which can be inferred by T1 mapping techniques.

METHODS

Patients with chronic AR who were undergoing contrast CMR with T1 mapping for valve assessment from 2011 to 2018 were enrolled. Patients with a confounding etiology of myocardial fibrosis were excluded. In addition to quantification of AR severity and LV volumetrics, LGE and T1 mapping pre- and post-contrast were performed to measure extracellular volume (ECV) and indexed ECV (iECV). Patients were followed up longitudinally to assess for the composite event of death and the need for aortic valve replacement.

RESULTS

A total of 177 patients with isolated chronic AR were included (66% males, median age 58 years [47.0 years-68.0 years]) with a median follow up of 2.5 years (1.07 years-3.56 years). The iECV significantly increased with AR severity (P < 0.001), whereas ECV and replacement fibrosis did not (P = NS). On multivariate analysis, iECV remained associated with the composite event (P = 0.01). On Kaplan-Meier analysis stratified by AR regurgitant fraction (RF) and iECV, patients with AR RF severity ≥30% and iECV ≥24 mL/m² demonstrated the highest event rate.

CONCLUSIONS

Among CMR biomarkers of fibrosis, iECV was more closely associated than replacement fibrosis or ECV with survival free of aortic valve replacement.

Embryonic Stem Cell-Derived Exosomes Attenuate Transverse Aortic Constriction Induced Heart Failure by Increasing Angiogenesis

Background: Although there are concerns regarding their clinical use, embryonic stem cells (ESCs) hold a great promise for cardiac repair. Exosomes deriving from ESCs constitute a promising alternative for heart restoration. However, their effects in hypertension-induced heart failure are still unknown.

Objective and Methods: To investigate the effects of ESCs-derived exosomes on hypertension-induced heart failure and the underlying mechanisms, sustained transverse aortic constriction (TAC) was performed on 8-week-old C57BL/6 male mice. After 1 months, ESCs-derived exosomes were isolated and injected intravenously once a week for 6 weeks. Echocardiography, wheat germ agglutinin (WGA), Masson staining, immunohistochemistry, and tube formation assays were all involved in our study.

Results: Proteomics analyses revealed that ESC-derived exosomes contain FGF2 protein. Tube formation induced by these exosomes could be inhibited by FGF2R siRNA interference. ESCs-derived exosomes evidently attenuated TAC-induced heart failure, improving cardiac function and promoting myocardial angiogenesis which can be attenuated by selective FGF2 inhibitor AZD4547.

Conclusions: ESC-derived exosomes attenuate TAC-induced heart failure mostly by promoting myocardial angiogenesis. FGF2 signaling plays a vital role in the myocardial angiogenesis induced by ESC-derived exosomes.

The association between RGS4 and choline in cardiac fibrosis

Background

Myocardial fibrosis is caused by the adverse and powerful remodeling of the heart secondary to the death of cardiomyocytes after myocardial infarction. Regulators of G protein Signaling (RGS) 4 is involved in cardiac diseases through regulating G protein-coupled receptors (GPCRs).

Methods

Cardiac fibrosis models were established through cardiac fibroblasts (CFs) treatment with transforming growth factor (TGF)-β1 in vitro and mice subjected to myocardial infarction in vivo. The mRNA expression of RGS4, collagen I/III and α-SMA detected by qRT-PCR. Protein level of RGS4, collagen I, CTGF and α-SMA detected by Western blot. The ejection fraction (EF%) and fractional shortening (FS%) of mice were measured by echocardiography. Collagen deposition of mice was tested by Masson staining.

Results

The expression of RGS4 increased in CFs treatment with TGF-β1 and in MI mice. The model of cardiac fibrosis detected by qRT-PCR and Western blot. It was demonstrated that inhibition of RGS4 expression improved cardiac fibrosis by transfection with small interfering RNA in CFs and injection with lentivirus shRNA in mice. The protective effect of choline against cardiac fibrosis was counteracted by overexpression of RGS4 in vitro and in vivo. Moreover, choline inhibited the protein level of TGF-β1, p-Smad2/3, p-p38 and p-ERK1/2 in CFs treated with TGF-β1, which were restored by RGS4 overexpression.

Conclusion

This study demonstrated that RGS4 promoted cardiac fibrosis and attenuated the anti-cardiac fibrosis of choline. RGS4 may weaken anti-cardiac fibrosis of choline through TGF-β1/Smad and MAPK signaling pathways.

Prognostic significance of myocardial fibrosis and CMR characteristics in bicuspid aortic valve with moderate and severe aortic insufficiency

OBJECTIVES

This study attempted to evaluate the characteristics and prognostic value of myocardial fibrosis (MF) in aortic insufficiency (AI) patients with bicuspid aortic valve (BAV) or tricuspid aortic valve (TAV) by cardiac magnetic resonance (CMR).

METHODS

A total of 314 adults with CMR-diagnosed AI were retrospectively retrieved. Of them, 166 patients with moderate or severe AI were included and divided into two groups: BAV group (N = 46) and a TAV group (N = 120). The presence and characteristics of MF were assessed with CMR. The patients were followed for adverse clinical events. The prognostic capability of the parameters was assessed using Cox regression model.

RESULTS

LV fibrosis was more common in the BAV group than in the TAV group (65.2% vs. 45.0%; p = 0.020). There was a strong association between BAV and MF even after adjusting for clinical and imaging variables (odds ratio: 3.57; p = 0.031). Kaplan-Meier analysis showed a higher rate of clinical adverse events in AI+BAV patients with MF during a median follow-up of 4.7 years. Multivariate Cox regression analysis showed that late gadolinium enhancement (LGE) was an independent predictor of clinical adverse outcome.

CONCLUSION

MF is more common in AI with BAV than with TAV and is a predictor of clinical adverse events.

KEY POINTS

• The presence and extent of late gadolinium enhancement of left ventricular were more common and severer in the bicuspid aortic valve group than in the tricuspid aortic valve group in aortic insufficiency patients. • Bicuspid aortic valve was an independent factor for myocardial fibrosis in aortic insufficiency patients. • Late gadolinium enhancement could be used as an independent predictor of adverse clinical events in this population.

The Potential of Hydrogen Sulfide Donors in Treating Cardiovascular Diseases

Hydrogen sulfide (H2S) has long been considered as a toxic gas, but as research progressed, the idea has been updated and it has now been shown to have potent protective effects at reasonable concentrations. H2S is an endogenous gas signaling molecule in mammals and is produced by specific enzymes in different cell types. An increasing number of studies indicate that H2S plays an important role in cardiovascular homeostasis, and in most cases, H2S has been reported to be downregulated in cardiovascular diseases (CVDs). Similarly, in preclinical studies, H2S has been shown to prevent CVDs and improve heart function after heart failure. Recently, many H2S donors have been synthesized and tested in cellular and animal models. Moreover, numerous molecular mechanisms have been proposed to demonstrate the effects of these donors. In this review, we will provide an update on the role of H2S in cardiovascular activities and its involvement in pathological states, with a special focus on the roles of exogenous H2S in cardiac protection.

Pre- and postoperative left atrial and ventricular volumetric and deformation analyses in severe aortic regurgitation

Background

The impact of volume overload due to aortic regurgitation (AR) on systolic and diastolic left ventricular (LV) indices and left atrial remodeling is unclear. We assessed the structural and functional effects of severe AR on LV and left atrium before and after aortic valve replacement.

Methods

Patients with severe AR scheduled for aortic valve replacement (n = 65) underwent two- and three-dimensional echocardiography, including left atrial strain imaging, before and 1 year after surgery. A control group was selected, and comprised patients undergoing surgery for thoracic aortic aneurysm without aortic valve replacement (n = 20). Logistic regression analysis was used to assess predictors of impaired left ventricular functional and structural recovery, defined as a composite variable of diastolic dysfunction grade ≥ 2, EF < 50%, or left ventricular end-diastolic volume index above the gender-specific normal range.

Results

Diastolic dysfunction was present in 32% of patients with AR at baseline. Diastolic LV function indices and left atrial strain improved, and both left atrial and LV volumes decreased in the AR group following aortic valve replacement. Preoperative left atrial strain during the conduit phase added to left ventricular end-systolic volume index for the prediction of impaired LV functional and structural recovery after aortic valve replacement (model p < 0.001, accuracy 70%; addition of left atrial strain during the conduit phase to end-systolic volume index p = 0.006).

Conclusions

One-third of patients with severe AR had signs of diastolic dysfunction. Aortic valve surgery reduced LV and left atrial volumes and improved diastolic indices. Left atrial strain during the conduit phase added to the well-established left ventricular end-diastolic dimension for the prediction of impaired left ventricular functional and structural recovery at follow-up. However, long-term follow-up studies with hard endpoints are needed to assess the value of left atrial strain as predictor of myocardial recovery in aortic regurgitation.

Qingda granule attenuates cardiac fibrosis via suppression of the TGF-β1/Smad2/3 signaling pathway in vitro and in vivo

Cardiac fibrosis plays an important role in hypertension-related contractile dysfunction and heart failure. Qingda granule (QDG), derived from the Qingxuan Jiangya decoction, has been used clinically for more than 60 years to treat hypertension. However, the effect of QDG on hypertensive cardiac fibrosis remains largely unknown. The objective of this study was to investigate the effect of QDG on cardiac fibrosis and explore the underlying mechanism in vivo and in vitro. For in vivo experiments, 30 male spontaneously hypertensive rats were randomly divided into groups that received no QDG or one of three doses (0.45, 0.9 or 1.8 g/kg/day). Positive-control animals received valsartan (VAL, 7.2 mg/kg/day). Treatments were administered by gavage for 10 weeks. All three doses of QDG and VAL led to significantly lower blood pressure than in SHR animals. Besides, all three doses of QDG and VAL attenuated pathological changes in SHR animals. However, only intermediate, high concentrations of QDG and VAL led to significantly lower left ventricle ejection fraction and left ventricle fractional shortening than in SHR animals. Therefore, the minimum and effective QDG dose (intermediate concentration of QDG) was selected for subsequent animal experiments in this study. Our results showed that intermediate concentration of QDG also significantly mitigated the increases in levels of α-smooth muscle actin (α-SMA), proliferating cell nuclear antigen (PCNA), collagen III, transforming growth factor-β1 (TGF-β1) and in the ratio of phospho-Smad2/3 to total Smad2/3 protein in cardiac tissue, based on immunohistochemistry, Western blotting, and Masson staining. For in vitro experiments, primary cardiac fibroblasts were stimulated with 100 nM angiotensin II in the presence or absence of QDG. And we tested different concentrations of QDG (3.125, 6.25, 12.5, 25, 50 μg/mL) in the cell viability experiment. Our results showed that 3.125, 6.25 and 12.5 μg/mL of QDG treatment for 24 h didn't affect the cell viability of cardiac fibroblasts. Consistently, QDG at 6.25 or 12.5 μg/mL significantly reduced cell viability and down-regulated α-SMA in primary cardiac fibroblasts were stimulated with 100 nM angiotensin II. Therefore, QDG at 12.5 μg/mL was chosen for the following cell experiment. Our results showed that QDG at 12.5 μg/mL alleviated the increase of PCNA, collagen Ⅲ, TGF-β1 expression, and the ratio of phospho-Smad2/3 to total Smad2/3 protein. Our studies in vitro and in vivo suggest that QDG reduces blood pressure and cardiac fibrosis as well as protecting cardiac function, and that it exerts these effects in part by suppressing TGF-β1/Smad2/3 signaling.

Reduced left ventricular contractility, increased diastolic operant stiffness and high energetic expenditure in patients with severe aortic regurgitation without indication for surgery

OBJECTIVES

Recent mortality studies showed worse prognosis in patients (ARNS) with severe aortic regurgitation and preserved ejection fraction (EF) not fulfilling the criteria of current guidelines for surgery. The aim of our study was to analyse left ventricular (LV) systolic and diastolic function and mechanical energetics to find haemodynamic explanations for the reduced prognosis of these patients and to seek a new concept for surgery.

METHODS

Global longitudinal strain (GLS) and echo-based single-beat pressure-volume analyses were performed in patients with ARNS (LV end-diastolic diameter <70 mm, EF >50%, GLS > -19% n = 41), with indication for surgery (ARS; n = 19) and in mild hypertensive controls (C; n = 20). Additionally, end-systolic elastance (LV contractility), stroke work and total energy (pressure-volume area) were calculated.

RESULTS

ARNS demonstrated significantly depressed LV contractility versus C: end-systolic elastance (1.58 ± 0.7 vs 2.54 ± 0.8 mmHg/ml; P < 0.001), despite identical EF (EF: 59 ± 6% vs 59 ± 7%). Accordingly, GLS was decreased [-15.7 ± 2.7% (n = 31) vs -21.2 ± 2.4%; P < 0.001], end-diastolic volume (236 ± 90 vs 136 ± 30 ml; P < 0.001) and diastolic operant stiffness were markedly enlarged, as were pressure-volume area and stroke work, indicating waste of energy. The correlation of GLS versus end-systolic elastance was good (r = -0.66; P < 0.001). ARNS and ARS patients demonstrated similar haemodynamic disorders, whereas only GLS was worse in ARS.

CONCLUSIONS

ARNS patients almost matched the ARS patients in their haemodynamic and energetic deterioration, thereby explaining poor prognosis reported in literature. GLS has been shown to be a reliable surrogate for LV contractility, possibly overestimating contractility due to exhausted preload reserve in aortic regurgitation patients. GLS may outperform conventional echo parameters to predict more precisely the timing of surgery.

Myocardial Scar and Mortality in Chronic Aortic Regurgitation

Background

Chronic aortic regurgitation (AR) can be associated with myocardial scarring. It is unknown if scarring in AR is linked to poor outcomes and whether aortic valve replacement impacts this association. We investigated the relationship of myocardial scarring to mortality in chronic AR using cardiac magnetic resonance.

Methods and Results

We enrolled patients with moderate or greater AR between 2009 and 2019 and performed a blinded assessment of left ventricle remodeling, AR severity, and presence and extent of myocardial scarring by late gadolinium enhancement. The primary outcome was all‐cause mortality. We followed 392 patients (median age 62 [interquartile range, 51–71] years), and 78.1% were men, and 25.8% had bicuspid valves. Median aortic valve regurgitant volume was 39 mL (interquartile range, 30–60). Myocardial scar was present in 131 (33.4%) patients. Aortic valve replacement was performed in 165 (49.1%) patients. During follow‐up, up to 10.8 years (median 32.3 months [interquartile range, 9.8–69.5]), 51 patients (13%) died. Presence of myocardial scar (hazard ratio [HR], 3.62; 95% CI, 2.06–6.36; P<0.001), infarction scar (HR, 4.94; 95% CI, 2.58–9.48; P<0.001), and noninfarction scar (HR, 2.75; 95% CI, 1.39–5.44; P<0.004) were associated with mortality. In multivariable analysis, the presence of scar remained independently associated with death (HR, 2.53; 95% CI, 1.15–5.57; P=0.02). Among patients with myocardial scar, aortic valve replacement was independently associated with a lower risk of mortality (HR, 0.34; 95% CI, 0.12–0.97; P=0.03), even after adjustment for confounders.

Conclusions

In aortic regurgitation, myocardial scar is independently associated with a 2.5‐fold increase risk in mortality. Aortic valve replacement was associated with a reduction in risk of mortality in patients with scarring.

Cardiac fibrosis

Myocardial fibrosis, the expansion of the cardiac interstitium through deposition of extracellular matrix proteins, is a common pathophysiologic companion of many different myocardial conditions. Fibrosis may reflect activation of reparative or maladaptive processes. Activated fibroblasts and myofibroblasts are the central cellular effectors in cardiac fibrosis, serving as the main source of matrix proteins. Immune cells, vascular cells and cardiomyocytes may also acquire a fibrogenic phenotype under conditions of stress, activating fibroblast populations. Fibrogenic growth factors (such as transforming growth factor-β and platelet-derived growth factors), cytokines [including tumour necrosis factor-α, interleukin (IL)-1, IL-6, IL-10, and IL-4], and neurohumoral pathways trigger fibrogenic signalling cascades through binding to surface receptors, and activation of downstream signalling cascades. In addition, matricellular macromolecules are deposited in the remodelling myocardium and regulate matrix assembly, while modulating signal transduction cascades and protease or growth factor activity. Cardiac fibroblasts can also sense mechanical stress through mechanosensitive receptors, ion channels and integrins, activating intracellular fibrogenic cascades that contribute to fibrosis in response to pressure overload. Although subpopulations of fibroblast-like cells may exert important protective actions in both reparative and interstitial/perivascular fibrosis, ultimately fibrotic changes perturb systolic and diastolic function, and may play an important role in the pathogenesis of arrhythmias. This review article discusses the molecular mechanisms involved in the pathogenesis of cardiac fibrosis in various myocardial diseases, including myocardial infarction, heart failure with reduced or preserved ejection fraction, genetic cardiomyopathies, and diabetic heart disease. Development of fibrosis-targeting therapies for patients with myocardial diseases will require not only understanding of the functional pluralism of cardiac fibroblasts and dissection of the molecular basis for fibrotic remodelling, but also appreciation of the pathophysiologic heterogeneity of fibrosis-associated myocardial disease.

Lab-on-a-Chip for Cardiovascular Physiology and Pathology

Lab-on-a-chip technologies have allowed researchers to acquire a flexible, yet relatively inexpensive testbed to study one of the leading causes of death worldwide, cardiovascular disease. Cardiovascular diseases, such as peripheral artery disease, arteriosclerosis, and aortic stenosis, for example, have all been studied by lab-on-a-chip technologies. These technologies allow for the integration of mammalian cells into functional structures that mimic vital organs with geometries comparable to those found in vivo. For this review, we focus on microdevices that have been developed to study cardiovascular physiology and pathology. With these technologies, researchers can better understand the electrical-biomechanical properties unique to cardiomyocytes and better stimulate and understand the influence of blood flow on the human vasculature. Such studies have helped increase our understanding of many cardiovascular diseases in general; as such, we present here a review of the current state of the field and potential for the future.

Cardiac Magnetic Resonance in Valvular Heart Disease: Assessment of Severity and Myocardial Remodeling

Cardiac magnetic resonance (CMR) has emerged as the gold standard in assessing ventricular mass, volume, and systolic function. Due to these and other strengths, CMR has increasingly been used to study valvular heart disease (VHD) and resultant cardiac remodeling. By using CMR to assess flow, limitations in echocardiographic assessment of VHD can be overcome, particularly in regurgitant lesions. The following article reviews the current role of CMR imaging in studying disease severity and myocardial remodeling in patients with VHD.

Imaging tools for assessment of myocardial fibrosis in humans: the need for greater detail

Myocardial fibrosis is recognized as a key pathological process in the development of cardiac disease and a target for future therapeutics. Despite this recognition, the assessment of fibrosis is not a part of routine clinical practice. This is primarily due to the difficulties in obtaining an accurate assessment of fibrosis non-invasively. Moreover, there is a clear discrepancy between the understandings of myocardial fibrosis clinically where fibrosis is predominately studied with comparatively low-resolution medical imaging technologies like MRI compared with the basic science laboratories where fibrosis can be visualized invasively with high resolution using molecularly specific fluorescence microscopes at the microscopic and nanoscopic scales. In this article, we will first review current medical imaging technologies for assessing fibrosis including echo and MRI. We will then highlight the need for greater microscopic and nanoscopic analysis of human tissue and how this can be addressed through greater utilization of human tissue available through endomyocardial biopsies and cardiac surgeries. We will then describe the relatively new field of molecular imaging that promises to translate research findings to the clinical practice by non-invasively monitoring the molecular signature of fibrosis in patients.

Therapeutic angiogenesis with exosomal microRNAs: an effectual approach for the treatment of myocardial ischemia

Therapeutic angiogenesis presents a potential approach for treating ischemic heart diseases especially in patients who are not appropriate candidates for traditional approaches of revascularization. This approach acts through inducing the neovascularization or maturation of pre-existing collateral vessels into functional arteries to bypass the blocked arteries and restore perfusion to ischemic myocardium. Successful stimulation of local angiogenesis can be established by the cross talk between stem cells, endothelial cells, and cardiomyocytes, which is mainly mediated by paracrine communication accompanied by secreted exosomes. Exosomes are extracellular vesicles carrying a complex of signaling molecules, such as microRNAs (miRs) that can modulate the function of recipient cells. Such particles have been indicated to exert cardioprotective role through providing signaling cues for angiogenesis, an effect ascribed mainly to their miRs content. Exosomal miRs-mediated therapeutic angiogenesis has been under drastic preclinical and clinical studies. In the current review, it was aimed to summarize pro-angiogenic exosomal miRs released by various cell types mediating angiogenesis, including stem cells, endothelial cells, and cardiomyocytes, which appear to exert a therapeutic effect on the myocardial ischemia. In brief, secreted exosomal miRs including miR-210, miR-23a-3p, miR-424, let-7f, miR-30b, miR-30c, miR-126, miR-21, miR-132, miR-130a-3p, miR-214, miR-378, miR-126, miR-133, and let-7b-5p could protect against myocardial ischemia through inducing cardiac angiogenesis and vascular regeneration resulting in the increase blood flow to ischemic myocardium.

Causes, Diagnosis, Risk Stratification and Treatment of Bicuspid Aortic Valve Disease: An Updated Review

The most common congenital heart disease is the bicuspid aortic valve. Understanding the pathophysiology and the altered hemodynamics is a key component for the diagnosis, risk stratification and treatment. Among others, aortic valve stenosis is the most common complication. Treatment strategies vary depending on the severity of the disease, particularly the dilation of the aorta playing a major role. Together with valve replacement, transcatheter aortic valve implantation is now considered as an alternative option with good results. With this review we would like to discuss the causes, diagnostic methods, risk stratification and treatment strategies of the bicuspid aortic valve.

Heat shock transcription factor 1 regulates exercise-induced myocardial angiogenesis after pressure overload via HIF-1α/VEGF pathway

Exercise training is believed to have a positive effect on cardiac hypertrophy after hypertension. However, its mechanism is still not fully understood. Herein, our findings suggest that heat shock transcription factor 1 (HSF1) improves exercise‐initiated myocardial angiogenesis after pressure overload. A sustained narrowing of the diagonal aorta (TAC) and moderately‐ intense exercise training protocol were imposed on HSF1 heterozygote (KO) and their littermate wild‐type (WT) male mice. After two months, the cardiac function was assessed using the adaptive responses to exercise training, or TAC, or both of them such as catheterization and echocardiography. The HE stains assessed the area of myocyte cross‐sectional. The Western blot and real‐time PCR measured the levels of expression for heat shock factor 1 (HSF1), vascular endothelial growth factor (VEGF) and hypoxia inducible factor‐1 alpha (HIF‐1α) in cardiac tissues. The anti‐CD31 antibody immunohistochemical staining was done to examine how exercise training influenced cardiac ontogeny. The outcome illustrated that exercise training significantly improved the cardiac ontogeny in TAC mice, which was convoyed by elevated levels of expression for VEGF and HIF‐1α and preserved the heart microvascular density. More importantly, HSF1 deficiency impaired these effects induced by exercise training in TAC mice. In conclusion, exercise training encourages cardiac ontogeny by means of HSF1 activation and successive HIF‐1α/VEGF up‐regulation in endothelial cells during continued pressure overload.

Idiopathic Myocardial Fibrosis in Captive Chimpanzees (Pan troglodytes)

Cardiovascular disorders and predominantly idiopathic myocardial fibrosis are frequently associated with mortality among zoo-housed chimpanzees (Pan troglodytes). Formalin-fixed whole hearts of deceased chimpanzees housed in zoos (n = 33) and an African sanctuary (n = 2) underwent detailed macroscopic and histopathologic examination using a standardized protocol. Archived histological slides from the hearts of 23 additional African sanctuary-housed chimpanzees were also examined. Myocardial fibrosis (MF) was identified in 30 of 33 (91%) of the zoo-housed chimpanzees but none of the 25 sanctuary-housed chimpanzees. MF was shown to be characterized by both interstitial and replacement fibrosis. Immunophenotyping demonstrated that the fibrotic lesions were accompanied by the increased presence of macrophages, alpha smooth muscle actin-positive myofibroblasts, and a minimal to mild T-cell-dominant leukocyte infiltration. There was no convincing evidence of cardiotropic viral infection or suggestion that diabetes mellitus or vitamin E or selenium deficiency were associated with the presence of the lesion. However, serum vitamin D concentrations among zoo-housed chimpanzees were found to be lower in seasons of low ultraviolet light levels.

Prognostic implications of left ventricular global longitudinal strain in patients with bicuspid aortic valve disease and preserved left ventricular ejection fraction

Aims

In patients with bicuspid aortic valve (BAV) and preserved left ventricular (LV) ejection fraction (EF), the frequency of impaired LV global longitudinal strain (GLS) and its prognostic implications are unknown. The present study evaluated the proportion and prognostic value of impaired LV GLS in patients with BAV and preserved LVEF.

Methods and results

Five hundred and thirteen patients (68% men; mean age 44 ± 18 years) with BAV and preserved LVEF (&gt;50%) were divided into five groups according to the type of BAV dysfunction: (i) normal function BAV, (ii) mild aortic stenosis (AS) or aortic regurgitation (AR), (iii) ≥moderate isolated AS, (iv) ≥moderate isolated AR, and (v) ≥moderate mixed AS and AR. LV systolic dysfunction based on 2D speckle-tracking echocardiography was defined as a cut-off value of LVGLS (−13.6%). The primary outcome was aortic valve intervention or all-cause mortality. The proportion of patients with LVGLS ≤−13.6% was the highest in the normal BAV group (97%) and the lowest in the group with moderate and severe mixed AS and AR (79%). During a median follow-up of 10 years, 210 (41%) patients underwent aortic valve replacement and 17 (3%) died. Patients with preserved LV systolic function (LVGLS ≤ −13.6%) had significantly better event-free survival compared to those with impaired LV systolic function (LVGLS &gt; −13.6%). LVGLS was independently associated with increased risk of events (mainly aortic valve replacement): hazard ratio 1.09; P &lt; 0.001.

Conclusion

Impaired LVGLS in BAV with preserved LVEF is not infrequent and was independently associated with increased risk of events (mainly aortic valve replacement events).

Aortic valvular imaging with cardiovascular magnetic resonance: seeking for comprehensiveness

Cardiovascular magnetic resonance (CMR) has an emerging role in aortic valve disease evaluation, becoming an all-in-one technique. CMR evaluation of the anatomy and flow through the aortic valve has a higher reproducibility than echocardiography. Its unique ability of in vivo myocardial tissue characterization, significantly improves the risk stratification and management of patients. In addition, CMR is equivalent to cardiac CT angiography for trans-aortic valvular implantation and surgical aortic valve replacement planning; on the other hand, its role in the evaluation of ventricular function improving and post-treatment complications is undisputed. This review encompasses the existing literature regarding the role of CMR in aortic valve disease, exploring all the aspects of the disease, from diagnosis to prognosis.

Hypoxia-induced H19/YB-1 cascade modulates cardiac remodeling after infarction

Rationale: Long non-coding RNA (lncRNAs) has been identified as a pivotal novel regulators in cardiac development as well as cardiac pathogenesis. lncRNA H19 is known as a fetal gene but it is exclusively abundant in the heart and skeletal muscles in adulthood, and is evolutionarily conserved in humans and mice. It has been reported to possess a significant correlation with the risk of coronary artery diseases. However, the function of H19 is not well characterized in heart.

Methods: Loss-of-function and gain-of-function mouse models with left anterior descending coronary artery-ligation surgery were utilized to evaluate the functionality of H19 in vivo. For mechanistic studies, hypoxia condition were exerted in in vitro models to mimic cardiac ischemic injury. Chromatin isolation by RNA immunoprecipitation (ChIRP) was performed to reveal the interacting protein of lncRNA H19.

Results: lncRNA H19 was significantly upregulated in the infarct area post-surgery day 4 in mouse model. Ectopic expression of H19 in the mouse heart resulted in severe cardiac dilation and fibrosis. Several extracellular matrix (ECM) genes were significantly upregulated. While genetic ablation of H19 by CRISPR-Cas9 ameliorated post-MI cardiac remodeling with reduced expression in ECM genes. Through chromatin isolation by RNA purification (ChIRP), we identified Y-box-binding protein (YB)-1, a suppressor of Collagen 1A1, as an interacting protein of H19. Furthermore, H19 acted to antagonize YB-1 through direct interaction under hypoxia, which resulted in de-repression of Collagen 1A1 expression and cardiac fibrosis.

Conclusions: Together these results demonstrate that lncRNA H19 and its interacting protein YB-1 are crucial for ECM regulation during cardiac remodeling.

Mechanisms of cardiac collagen deposition in experimental models and human disease

The inappropriate deposition of extracellular matrix within the heart (termed cardiac fibrosis) is associated with nearly all types of heart disease, including ischemic, hypertensive, diabetic, and valvular. This alteration in the composition of the myocardium can physically limit cardiomyocyte contractility and relaxation, impede electrical conductivity, and hamper regional nutrient diffusion. Fibrosis can be grossly divided into 2 types, namely reparative (where collagen deposition replaces damaged myocardium) and reactive (where typically diffuse collagen deposition occurs without myocardial damage). Despite the widespread association of fibrosis with heart disease and general understanding of its negative impact on heart physiology, it is still not clear when collagen deposition becomes pathologic and translates into disease symptoms. In this review, we have summarized the current knowledge of cardiac fibrosis in human patients and experimental animal models, discussing the mechanisms that have been deduced from the latter in relation to the former. Because assessment of the extent of fibrosis is paramount both as a research tool to further understanding and as a clinical tool to assess patients, we have also summarized the current state of noninvasive/minimally invasive detection systems for cardiac fibrosis. Albeit not exhaustive, our aim is to provide an overview of the current understanding of cardiac fibrosis, both clinically and experimentally.

Molecular Imaging of the Heart

Multimodality cardiovascular imaging is routinely used to assess cardiac function, structure, and physiological parameters to facilitate the diagnosis, characterization, and phenotyping of numerous cardiovascular diseases (CVD), as well as allows for risk stratification and guidance in medical therapy decision-making. Although useful, these imaging strategies are unable to assess the underlying cellular and molecular processes that modulate pathophysiological changes. Over the last decade, there have been great advancements in imaging instrumentation and technology that have been paralleled by breakthroughs in probe development and image analysis. These advancements have been merged with discoveries in cellular/molecular cardiovascular biology to burgeon the field of cardiovascular molecular imaging. Cardiovascular molecular imaging aims to noninvasively detect and characterize underlying disease processes to facilitate early diagnosis, improve prognostication, and guide targeted therapy across the continuum of CVD. The most-widely used approaches for preclinical and clinical molecular imaging include radiotracers that allow for high-sensitivity in vivo detection and quantification of molecular processes with single photon emission computed tomography and positron emission tomography. This review will describe multimodality molecular imaging instrumentation along with established and novel molecular imaging targets and probes. We will highlight how molecular imaging has provided valuable insights in determining the underlying fundamental biology of a wide variety of CVDs, including: myocardial infarction, cardiac arrhythmias, and nonischemic and ischemic heart failure with reduced and preserved ejection fraction. In addition, the potential of molecular imaging to assist in the characterization and risk stratification of systemic diseases, such as amyloidosis and sarcoidosis will be discussed. © 2019 American Physiological Society. Compr Physiol 9:477-533, 2019.

New classification of geometric patterns considering left ventricular volume in patients with chronic aortic valve regurgitation: Prevalence and association with adverse cardiovascular outcomes

BACKGROUND

Left ventricular (LV) remodeling due to aortic regurgitation (AR) often leads to maladaptive responses. We assessed the prevalence and clinical implications of LV remodeling considering LV volume, mass, and relative wall thickness at the time of AR diagnosis.

METHODS AND RESULTS

Between 2008 and 2017, 370 consecutive patients (mean age 67.3 ± 16.1 years, 56.5% males), with moderate or severe AR, were retrospectively analyzed. LV geometric patterns and clinical outcomes (cardiovascular death, hospitalization for heart failure, or aortic valve replacement) were evaluated. LV dilatation (LV end-diastolic volume >75 mL/m² ) was present in 228 patients (61.6%). Applying the new LV remodeling classification system, 40 (10.8%) patients had normal geometry, 14 (3.8%) concentric remodeling, 43 (11.6%) concentric hypertrophy (LVH), 45 (12.2%) indeterminate LVH, 38 (10.3%) mixed LVH, 93 (25.1%) dilated LVH, 54 (14.6%) eccentric LVH, and 43 (11.6%) eccentric remodeling. During a median follow-up of 3.48 years (25th-75th percentile 0.91-5.57), 97 (26.2%) had the combined endpoint. LV dilation (P < 0.001), LVH (P < 0.001), and LV remodeling patterns were significantly associated with the combined endpoint. After multivariable adjustment for age, EF, aortic stenosis, CAD history, and moderate mitral regurgitation, dilated LVH (HR 7.61, IC 95% 1.82-31.80; P = 0.005) and eccentric LVH (HR 7.91, IC 95% 1.82-34.38; P = 0.006) were associated with adverse outcome compared to eccentric remodeling, that showed the best event-free survival rate.

CONCLUSIONS

In a contemporary cohort of patients with AR, applying the new LV remodeling classification system, only a minority had normal geometry. Dilated LVH and eccentric LVH showed distinct outcome penalty after adjustment for confounders.

Survival after Aortic Valve Replacement for Aortic Regurgitation: Prediction from Preoperative Contractility Measurement

BACKGROUND

Noninvasive measurement of myocardial contractility (end-systolic wall stress-adjusted change in left ventricular ejection fraction from rest to exercise [ΔLVEF - ΔESS]) predicts heart failure, subnormal LVEFrest, and sudden death in asymptomatic patients with chronic severe aortic regurgitation (AR). Here we assess the relation of preoperative ΔLVEF - ΔESS to survival after aortic valve replacement (AVR).

METHODS

Patients who underwent AVR for chronic, isolated, pure severe AR (n = 66) were followed for 13.0 ± 6.4 event-free years. Preoperative ΔLVEF - ΔESS (from combined echocardiographic and radionuclide cineangiographic data) enabled cohort stratification into 3 terciles (-1 to -11% [normal or mild] contractility deficit, -12 to -16% [moderate], and ≤-17% [severe], identical with segregation in our earlier study) to relate preoperative contractility to postoperative survival and to age- and gender-matched US census data.

RESULTS

Since AVR, 22 patients died (average annual risk [AAR] for all-cause mortality for the entire co hort = 3.15%). Preoperative ΔLVEF - ΔESS predicted postoperative survival (p = 0.009, log rank test). By contractility terciles, all-cause AARs were 1.44, 2.58, and 6.40%. Survival was lower than among US census comparators (p < 0.02), but the "mild" tercile was indistinguishable from census data (p = ns). By multivariable Cox regression, survival prediction by pre-AVR ΔLVEF - ΔESS was independent of, and superior to, prediction by age at surgery, gender, preoperative functional class, LVEFrest, LVEFexercise, change in LVEFrest to exercise, and LV diastolic or systolic dimensions (p ≤ 0.01, pre-AVR ΔLVEF - ΔESS vs. other covariates).

CONCLUSION

In severe AR, preoperative contractility predicts post-AVR survival and may be prognostically superior to clinical, geometric and performance descriptors, potentially impacting on patient selection for surgery.

Cardiac fibrosis: Cell biological mechanisms, molecular pathways and therapeutic opportunities

Cardiac fibrosis is a common pathophysiologic companion of most myocardial diseases, and is associated with systolic and diastolic dysfunction, arrhythmogenesis, and adverse outcome. Because the adult mammalian heart has negligible regenerative capacity, death of a large number of cardiomyocytes results in reparative fibrosis, a process that is critical for preservation of the structural integrity of the infarcted ventricle. On the other hand, pathophysiologic stimuli, such as pressure overload, volume overload, metabolic dysfunction, and aging may cause interstitial and perivascular fibrosis in the absence of infarction. Activated myofibroblasts are the main effector cells in cardiac fibrosis; their expansion following myocardial injury is primarily driven through activation of resident interstitial cell populations. Several other cell types, including cardiomyocytes, endothelial cells, pericytes, macrophages, lymphocytes and mast cells may contribute to the fibrotic process, by producing proteases that participate in matrix metabolism, by secreting fibrogenic mediators and matricellular proteins, or by exerting contact-dependent actions on fibroblast phenotype. The mechanisms of induction of fibrogenic signals are dependent on the type of primary myocardial injury. Activation of neurohumoral pathways stimulates fibroblasts both directly, and through effects on immune cell populations. Cytokines and growth factors, such as Tumor Necrosis Factor-α, Interleukin (IL)-1, IL-10, chemokines, members of the Transforming Growth Factor-β family, IL-11, and Platelet-Derived Growth Factors are secreted in the cardiac interstitium and play distinct roles in activating specific aspects of the fibrotic response. Secreted fibrogenic mediators and matricellular proteins bind to cell surface receptors in fibroblasts, such as cytokine receptors, integrins, syndecans and CD44, and transduce intracellular signaling cascades that regulate genes involved in synthesis, processing and metabolism of the extracellular matrix. Endogenous pathways involved in negative regulation of fibrosis are critical for cardiac repair and may protect the myocardium from excessive fibrogenic responses. Due to the reparative nature of many forms of cardiac fibrosis, targeting fibrotic remodeling following myocardial injury poses major challenges. Development of effective therapies will require careful dissection of the cell biological mechanisms, study of the functional consequences of fibrotic changes on the myocardium, and identification of heart failure patient subsets with overactive fibrotic responses.

MicroRNA-378 suppresses myocardial fibrosis through a paracrine mechanism at the early stage of cardiac hypertrophy following mechanical stress

Rationale: Excessive myocardial fibrosis is the main pathological process in the development of cardiac remodeling and heart failure; therefore, it is important to prevent excessive myocardial fibrosis. We determined that microRNA-378 (miR-378) is cardiac-enriched and highly repressed during cardiac remodeling. We therefore proposed that miR-378 has a critical role in regulation of cardiac fibrosis, and examined the effects of miR-378 on cardiac fibrosis after mechanical stress. Methods: Mechanical stress was respectively imposed on mice through a transverse aortic constriction (TAC) procedure and on cardiac fibroblasts by stretching silicon dishes. A chemically modified miR-378 mimic (Agomir) or an inhibitor (Antagomir) was administrated to mice by intravenous injection and to cells by direct addition to the culture medium. MiR-378 knockout mouse was constructed. Cardiac fibroblasts were cultured in the conditioned media from the cardiomyocytes with either miR-378 depletion or treatment with sphingomyelinase inhibitor GW4869. Quantitative real-time polymerase chain reaction analysis of gene and miRNA expression, Western blot analysis, immunochemistry and electron microscopy were performed to elucidate the mechanisms. Results: Mechanical stress induced significant increases in fibrotic responses, including myocardial fibrosis, fibroblast hyperplasia, and protein and gene expression of collagen and matrix metalloproteinases (MMPs) both in vivo and in vitro. All these fibrotic responses were attenuated by treatment with a chemically modified miR-378 mimic (Agomir) but were exaggerated by treatment with an inhibitor (Antagomir). MiR-378 knockout mouse models exhibited aggravated cardiac fibrosis after TAC. Media from the cardiomyocytes with either miR-378 depletion or treatment with sphingomyelinase inhibitor GW4869 enhanced the fibrotic responses of stimulated cardiac fibroblasts, confirming that miR-378 inhibits fibrosis in an extracellular vesicles-dependent secretory manner. Mechanistically, the miR-378-induced anti-fibrotic effects manifested partially through the suppression of p38 MAP kinase phosphorylation by targeting MKK6 in cardiac fibroblasts. Conclusions: miR-378 is secreted from cardiomyocytes following mechanical stress and acts as an inhibitor of excessive cardiac fibrosis through a paracrine mechanism.