Alterations of beta-adrenergic signaling and cardiac hypertrophy in transgenic mice overexpressing TGF-beta(1)

Hypertension and left ventricular hypertrophy

In the initial stage, left ventricular hypertrophy (LVH) is adaptive, but in time, it transforms to maladaptive LVH which is specific for the development of various phenotypes that cause heart failure, initially with preserved, but later with reduced left ventricular ejection fraction. Pathophysiological mechanisms, which are characteristic for remodeling procedure, are numerous and extremely complex, and should be subjected to further research with the aim of making a comprehensive overview of hypertensive heart disease (HHD) and discovering new options for preventing and treating HHD. The contemporary methods, such as cardiac magnetic resonance (CMR) and computed tomography (CT) provide very accurate morphological and functional information on HHD. The objective of this review article is to summarize the available scientific information in terms of prevalence, pathophysiology, diagnostics, prevention, contemporary therapeutic options, as well as to present potential therapeutic solutions based on the research of pathological mechanisms which are at the core of HHD.

Uncovering the Therapeutic Potential of Lithium Chloride in Type 2 Diabetic Cardiomyopathy: Targeting Tau Hyperphosphorylation and TGF-β Signaling via GSK-3β Inhibition

Diabetic cardiomyopathy (DCM) is a major complication of type 2 diabetes mellitus (T2DM) that leads to significant morbidity and mortality. The alteration in the signaling mechanism in diabetes leading to cardiomyopathy remains unclear. The purpose of this study is to investigate the role of tauopathy in myocardial dysfunction observed in T2DM. In that regard, diabetic Sprague Dawley rats were treated with intraperitoneal injections of lithium chloride (LiCl), inhibiting tau phosphorylation. Cardiac function was evaluated, and molecular markers of myocardial fibrosis and the TGF-β signaling were analyzed. T2DM rats exhibited a decline in ejection fraction and fractional shortening that revealed cardiac function abnormalities and increased myocardial fibrosis. These changes were associated with tau hyperphosphorylation. Treating diabetic rats with LiCl attenuated cardiac fibrosis and improved myocardial function. Inhibition of GSK-3β leads to the suppression of tau phosphorylation, which is associated with a decrease in TGF-β expression and regulation of the pro-inflammatory markers, suggesting that tau hyperphosphorylation is parallelly associated with fibrosis and inflammation in the diabetic heart. Our findings provide evidence of a possible role of tau hyperphosphorylation in the pathogenesis of DCM through the activation of TGF-β and by inducing inflammation. Targeting the inhibition of tau phosphorylation may offer novel therapeutic approaches to reduce DCM burden in T2DM patients.

YAP dysregulation triggers hypertrophy by CCN2 secretion and TGFβ uptake in human pluripotent stem cell-derived cardiomyocytes

Hypertrophy Cardiomyopathy (HCM) is the most prevalent hereditary cardiovascular disease - affecting >1:500 individuals. Advanced forms of HCM clinically present with hypercontractility, hypertrophy and fibrosis. Several single-point mutations in b-myosin heavy chain (MYH7) have been associated with HCM and increased contractility at the organ level. Different MYH7 mutations have resulted in increased, decreased, or unchanged force production at the molecular level. Yet, how these molecular kinetics link to cell and tissue pathogenesis remains unclear. The Hippo Pathway, specifically its effector molecule YAP, has been demonstrated to be reactivated in pathological hypertrophic growth. We hypothesized that changes in force production (intrinsically or extrinsically) directly alter the homeostatic mechano-signaling of the Hippo pathway through changes in stresses on the nucleus. Using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), we asked whether homeostatic mechanical signaling through the canonical growth regulator, YAP, is altered 1) by changes in the biomechanics of HCM mutant cardiomyocytes and 2) by alterations in the mechanical environment. We use genetically edited hiPSC-CM with point mutations in MYH7 associated with HCM, and their matched controls, combined with micropatterned traction force microscopy substrates to confirm the hypercontractile phenotype in MYH7 mutants. We next modulate contractility in healthy and disease hiPSC-CMs by treatment with positive and negative inotropic drugs and demonstrate a correlative relationship between contractility and YAP activity. We further demonstrate the activation of YAP in both HCM mutants and healthy hiPSC-CMs treated with contractility modulators is through enhanced nuclear deformation. We conclude that the overactivation of YAP, possibly initiated and driven by hypercontractility, correlates with excessive CCN2 secretion (connective tissue growth factor), enhancing cardiac fibroblast/myofibroblast transition and production of known hypertrophic signaling molecule TGFβ. Our study suggests YAP being an indirect player in the initiation of hypertrophic growth and fibrosis in HCM. Our results provide new insights into HCM progression and bring forth a testbed for therapeutic options in treating HCM.

The isoproterenol-induced myocardial fibrosis: A biochemical and histological investigation

The isoproterenol (ISO)-induced myocardial fibrosis is considered a reliable and repeatable experimental model characterized by a relatively low mortality rate. Although is well-known that ISO stimulates the β1 adrenergic receptors at the myocardial level, a high degree of heterogeneity emerges around the doses and duration of the treatment generating unclear results. Therefore, we propose to gain insights into the progression of ISO-induced myocardial fibrosis, in order to critically analyze and optimize the experimental model. Male Wistar rats (12-14-week-old) were submitted to subcutaneous injection of ISO, in particular, two doses were selected: the commonly used dose of 5 mg/kg and a lower dose of 1 mg/kg, administered for 3 and 6 days. Biochemical and histological examinations were conducted either immediately after the last administration or after a recovering period of 7 or 14 days from the initial administration. Noteworthy, from our investigation emerged that even the lower dose of ISO was able to induce the maximal biochemical and histological alterations, suggesting that lower doses should be considered to control the progression of the damage more precisely and to identify a prodromic phase in which intervention with pharmacological or nutraceutical tools can be effectively attempted.

Search progress of pyruvate kinase M2 (PKM2) in organ fibrosis

Fibrosis is characterized by abnormal deposition of the extracellular matrix (ECM), leading to organ structural remodeling and loss of function. The principal cellular effector in fibrosis is activated myofibroblasts, which serve as the main source of matrix proteins. Metabolic reprogramming, transitioning from mitochondrial oxidative phosphorylation to aerobic glycolysis, is widely observed in rapidly dividing cells such as tumor cells and activated myofibroblasts and is increasingly recognized as a fundamental pathogenic basis in organ fibrosis. Targeting metabolism represents a promising strategy to mitigate fibrosis. PKM2, a key enzyme in glycolysis, plays a pivotal role in metabolic reprogramming through allosteric regulation, impacting both metabolic and non-metabolic pathways. Therefore, metabolic reprogramming induced by PKM2 activation is involved in the occurrence and development of fibrosis in various organs. A comprehensive understanding of the role of PKM2 in fibrotic diseases is crucial for seeking new anti-fibrotic therapeutic targets. In this context, we summarize PKM2's role in glycolysis, mediating the intricate mechanisms underlying fibrosis in multiple organs, and discuss the potential value of PKM2 inhibitors and allosteric activators in future clinical treatments, aiming to identify novel therapeutic targets for proliferative fibrotic diseases.

Proteomic analysis reveals activation of platelet- and fibrosis-related pathways in hearts of ApoE-/- mice exposed to diesel exhaust particles

Air pollution is an environmental risk factor linked to multiple human diseases including cardiovascular diseases (CVDs). While particulate matter (PM) emitted by diesel exhaust damages multiple organ systems, heart disease is one of the most severe pathologies affected by PM. However, the in vivo effects of diesel exhaust particles (DEP) on the heart and the molecular mechanisms of DEP-induced heart dysfunction have not been investigated. In the current study, we attempted to identify the proteomic signatures of heart fibrosis caused by diesel exhaust particles (DEP) in CVDs-prone apolipoprotein E knockout (ApoE-/-) mice model using tandem mass tag (TMT)-based quantitative proteomic analysis. DEP exposure induced mild heart fibrosis in ApoE-/- mice compared with severe heart fibrosis in ApoE-/- mice that were treated with CVDs-inducing peptide, angiotensin II. TMT-based quantitative proteomic analysis of heart tissues between PBS- and DEP-treated ApoE-/- mice revealed significant upregulation of proteins associated with platelet activation and TGFβ-dependent pathways. Our data suggest that DEP exposure could induce heart fibrosis, potentially via platelet-related pathways and TGFβ induction, causing cardiac fibrosis and dysfunction.

Transforming growth factor-β and bone morphogenetic protein signaling pathways in pathological cardiac hypertrophy

Pathological cardiac hypertrophy (referred to as cardiac hypertrophy) is a maladaptive response of the heart to a variety of pathological stimuli, and cardiac hypertrophy is an independent risk factor for heart failure and sudden death. Currently, the treatments for cardiac hypertrophy are limited to improving symptoms and have little effect. Elucidation of the developmental process of cardiac hypertrophy at the molecular level and the identification of new targets for the treatment of cardiac hypertrophy are crucial. In this review, we summarize the research on multiple active substances related to the pathogenesis of cardiac hypertrophy and the signaling pathways involved and focus on the role of transforming growth factor-β (TGF-β) and bone morphogenetic protein (BMP) signaling in the development of cardiac hypertrophy and the identification of potential targets for molecular intervention. We aim to identify important signaling molecules with clinical value and hope to help promote the precise treatment of cardiac hypertrophy and thus improve patient outcomes.

Myocardial Fibrosis in Hypertrophic Cardiomyopathy: A Perspective from Fibroblasts

Hypertrophic cardiomyopathy (HCM) is the most common inherited heart disease and the leading cause of sudden cardiac death in young people. Mutations in genes that encode structural proteins of the cardiac sarcomere are the more frequent genetic cause of HCM. The disease is characterized by cardiomyocyte hypertrophy and myocardial fibrosis, which is defined as the excessive deposition of extracellular matrix proteins, mainly collagen I and III, in the myocardium. The development of fibrotic tissue in the heart adversely affects cardiac function. In this review, we discuss the latest evidence on how cardiac fibrosis is promoted, the role of cardiac fibroblasts, their interaction with cardiomyocytes, and their activation via the TGF-β pathway, the primary intracellular signalling pathway regulating extracellular matrix turnover. Finally, we summarize new findings on profibrotic genes as well as genetic and non-genetic factors involved in the pathophysiology of HCM.

Promising Therapeutic Treatments for Cardiac Fibrosis: Herbal Plants and Their Extracts

Cardiac fibrosis is closely associated with multiple heart diseases, which are a prominent health issue in the global world. Neurohormones and cytokines play indispensable roles in cardiac fibrosis. Many signaling pathways participate in cardiac fibrosis as well. Cardiac fibrosis is due to impaired degradation of collagen and impaired fibroblast activation, and collagen accumulation results in increasing heart stiffness and inharmonious activity, leading to structure alterations and finally cardiac function decline. Herbal plants have been applied in traditional medicines for thousands of years. Because of their naturality, they have attracted much attention for use in resisting cardiac fibrosis in recent years. This review sheds light on several extracts from herbal plants, which are promising therapeutics for reversing cardiac fibrosis.

Paricalcitol improved cardiac hypertrophy and fibrosis through upregulation of fibroblast growth factor-23 and downregulation of transforming growth factor-beta in a rat model of isoproterenol-induced cardiomyopathy

Acute cardiomyopathy is a significant global health concern and one of the leading causes of death in developed countries. Prior studies have shown an association between acute cardiomyopathy and low vitamin D levels. Although paricalcitol, a vitamin D receptor (VDR) activator, has demonstrated clinical benefits in patients with advanced kidney disease, its effect on cardiac remodeling in cardiomyopathy is unknown. This study aimed to investigate the relative effects of paricalcitol on cardiomyopathy in rats. Wistar-Kyoto rats were administered vehicle (sham control group) or isoproterenol to induce cardiomyopathy. Rats administered isoproterenol were subsequently treated with paricalcitol (experimental group) or vehicle (isoproterenol group). Picrosirius red and immunofluorescence staining were used to analyze cardiac fibrosis and hypertrophy. Immunohistochemistry staining was used to confirm the molecular mechanisms involved in isoproterenol-induced cardiomyopathy in rats. Injection of paricalcitol could reduce collagen and transforming growth factor-beta 1 (TGF-β1) levels while activating fibroblast growth factor receptor 1 (FGFR1) and fibroblast growth factor-23 (FGF23) without the help of Klotho, thereby reducing myocardial hypertrophy and fibrosis. As a VDR activator, paricalcitol reduces isoproterenol-induced cardiac fibrosis and hypertrophy by reducing the expression of TGF-β1 and enhancing the expression of VDR, FGFR1, and FGF23.

Differential Role of Aldosterone and Transforming Growth Factor Beta-1 in Cardiac Remodeling

Angiotensin II, a major culprit in cardiovascular disease, activates mediators that are also involved in pathological cardiac remodeling. In this context, we aimed at investigating the effects of two of them: aldosterone (Ald) and transforming growth factor beta-1 (TGF-β1) in an in vivo model. Six-week-old male wild-type (WT) and TGF-β1-overexpressing transgenic (TGF-β1-TG) mice were infused with subhypertensive doses of Ald for 2 weeks and/or treated orally with eplerenone from postnatal day 21. Thehearts' ventricles were examined by morphometry, immunoblotting to assess the intracellular signaling pathways and RT qPCR to determine hypertrophy and fibrosis marker genes. The TGF-β1-TG mice spontaneously developed cardiac hypertrophy and interstitial fibrosis and exhibited a higher baseline phosphorylation of p44/42 and p38 kinases, fibronectin and ANP mRNA expression. Ald induced a comparable increase in the ventricular-heart-weight-to-body-weight ratio and cardiomyocyte diameter in both strains, but a less pronounced increase in interstitial fibrosis in the transgenic compared to the WT mice (23.6% vs. 80.9%, p < 0.005). Ald increased the phosphorylation of p44/42 and p38 in the WT but not the TGF-β1-TG mice. While the eplerenone-enriched chow partially prevented Ald-induced cardiac hypertrophy in both genotypes and interstitial fibrosis in the WT controls, it completely protected against additional fibrosis in transgenic mice. Ald appears to induce cardiac hypertrophy independently of TGF-β1, while in the case of fibrosis, the downstream signaling pathways of these two factors probably converge.

An integrative review of nonobvious puzzles of cellular and molecular cardiooncology

Oncologic patients are subjected to four major treatment types: surgery, radiotherapy, chemotherapy, and immunotherapy. All nonsurgical forms of cancer management are known to potentially violate the structural and functional integrity of the cardiovascular system. The prevalence and severity of cardiotoxicity and vascular abnormalities led to the emergence of a clinical subdiscipline, called cardiooncology. This relatively new, but rapidly expanding area of knowledge, primarily focuses on clinical observations linking the adverse effects of cancer therapy with deteriorated quality of life of cancer survivors and their increased morbidity and mortality. Cellular and molecular determinants of these relations are far less understood, mainly because of several unsolved paths and contradicting findings in the literature. In this article, we provide a comprehensive view of the cellular and molecular etiology of cardiooncology. We pay particular attention to various intracellular processes that arise in cardiomyocytes, vascular endothelial cells, and smooth muscle cells treated in experimentally-controlled conditions in vitro and in vivo with ionizing radiation and drugs representing diverse modes of anti-cancer activity.

hKLK alleviates myocardial fibrosis in mice with viral myocarditis

Myocardial fibrosis is the most serious complication of viral myocarditis (VMC). This study aimed to investigate the therapeutic benefits and underlying mechanisms of lentivirus-mediated human tissue kallikrein gene transfer in myocardial fibrosis in VMC mice. We established VMC mouse model via intraperitoneal injection with Coxsackie B3 virus. The effect was then assessed after treatment with vehicle, the empty lentiviral vectors (EZ.null), and the vectors expressing hKLK1 (EZ.hKLK1) via tail vein injection for 30 days, respectively. The results showed that administering EZ.hKLK1 successfully induced hKLK1 overexpression in mouse heart. Compared with EZ.null treatment, EZ.hKLK1 administration significantly reduced the heart/weight ratio, improved cardiac function, and ameliorated myocardial inflammation in VMC mice, suggesting that hKLK1 overexpression alleviates VMC in mice. EZ.hKLK1 administration also significantly abrogated the increased myocardial collagen content, type I/III collagen ratio, TGF-β1 mRNA and protein expression in VMC mice, suggesting that hKLK1 overexpression reduces collagen accumulation and blunts TGF-β1 signaling in the hearts of VMC mice. In conclusion, our results suggest that hKLK1 alleviates myocardial fibrosis in VMC mice, possibly by downregulating TGF-β1 expression.

Effects of Simulated 5-Ion Galactic Cosmic Radiation on Function and Structure of the Mouse Heart

Missions into deep space will expose astronauts to the harsh space environment, and the degenerative tissue effects of space radiation are largely unknown. To assess the risks, in this study, male BALB/c mice were exposed to 500 mGy 5-ion simulated GCR (GCRsim) at the NASA Space Radiation Laboratory. In addition, male and female CD1 mice were exposed to GCRsim and administered a diet containing Transforming Growth Factor-beta (TGF-β)RI kinase (ALK5) inhibitor IPW-5371 as a potential countermeasure. An ultrasound was performed to investigate cardiac function. Cardiac tissue was collected to determine collagen deposition, the density of the capillary network, and the expression of the immune mediator toll-like receptor 4 (TLR4) and immune cell markers CD2, CD4, and CD45. In male BALB/c mice, the only significant effects of GCRsim were an increase in the CD2 and TLR4 markers. In male CD1 mice, GCRsim caused a significant increase in total collagens and a decrease in the expression of TLR4, both of which were mitigated by the TGF-β inhibitor diet. In female CD1 mice, GCRsim caused an increase in the number of capillaries per tissue area in the ventricles, which may be explained by the decrease in the left ventricular mass. However, this increase was not mitigated by TGF-β inhibition. In both male and female CD1 mice, the combination of GCRsim and TGF-β inhibition caused changes in left ventricular immune cell markers that were not seen with GCRsim alone. These data suggest that GCRsim results in minor changes to cardiac tissue in both an inbred and outbred mouse strain. While there were few GCRsim effects to be mitigated, results from the combination of GCRsim and the TGF-β inhibitor do point to a role for TGF-β in maintaining markers of immune cells in the heart after exposure to GCR.

Fibroblast Growth Factor 23 Exacerbates Cardiac Fibrosis in Deoxycorticosterone Acetate-Salt Mice With Hypertension

Fibroblast growth factor 23 (FGF23) is associated with cardiovascular disease in patients with chronic kidney disease; however, the mechanisms underlying the effect of FGF23 on cardiac function remain to be investigated. Herein, we studied the effect of continuous intravenous (CIV) FGF23 loading in a deoxycorticosterone acetate (DOCA)-salt mouse model with mild chronic kidney disease and hypertension as well as heart failure with a preserved ejection fraction. Wild-type male mice were randomly allocated to 4 groups: normal control, vehicle-treated DOCA-salt mice, FGF23-treated DOCA-salt mice, and FGF23- and calcitriol-treated DOCA-salt mice. The DOCA-salt mice received the agents via the CIV route for 10 days using an infusion minipump. DOCA-salt mice that received FGF23 showed a marked increase in the serum FGF23 level, and echocardiography in these mice revealed heart failure with a preserved ejection fraction. These mice also showed exacerbation of myocardial fibrosis, concomitant with an inverse and significant correlation with Cyp27b1 expression. Calcitriol treatment attenuated FGF23-induced cardiac fibrosis and improved diastolic function via inhibition of transforming growth factor-β signaling. This effect was independent of the systemic and local levels of FGF23. These results suggest that CIV FGF23 loading exacerbates cardiac fibrosis and that locally abnormal vitamin D metabolism is involved in this mechanism. Calcitriol attenuates this exacerbation by mediating transforming growth factor-β signaling independently of the FGF23 levels.

Insights into bone morphogenetic proteins in cardiovascular diseases

Bone morphogenetic proteins (BMPs) are secretory proteins belonging to the transforming growth factor-β (TGF-β) superfamily. These proteins play important roles in embryogenesis, bone morphogenesis, blood vessel remodeling and the development of various organs. In recent years, as research has progressed, BMPs have been found to be closely related to cardiovascular diseases, especially atherosclerosis, vascular calcification, cardiac remodeling, pulmonary arterial hypertension (PAH) and hereditary hemorrhagic telangiectasia (HHT). In this review, we summarized the potential roles and related mechanisms of the BMP family in the cardiovascular system and focused on atherosclerosis and PAH.

Protective effects of calorie restriction and 17-β estradiol on cardiac hypertrophy in ovariectomized obese rats

Obesity and menopause lead to cardiovascular diseases. Calorie restriction (CR) can modulate estrogen deficiency and obesity-related cardiovascular diseases. The protective effects of CR and estradiol on cardiac hypertrophy in ovariectomized obese rats were explored in this study. The adult female Wistar rats were divided into sham and ovariectomized (OVX) groups that received a high-fat diet (60% HFD) or standard diet (SD) or 30% CR for 16 weeks, and then, 1mg/kg E2 (17-β estradiol) was injected intraperitoneally every 4 days for four weeks in OVX-rats. Hemodynamic parameters were evaluated before and after each diet. Heart tissues were collected for biochemical, histological, and molecular analysis. HFD consumption led to weight gain in sham and OVX rats. In contrast, CR and E2 led to body weight loss in these animals. Also, heart weight (HW), heart weight/body weight (HW/BW) ratio, and left ventricular weight (LVW) were enhanced in OVX rats that received SD and HFD. E2 reduced these indexes in both diet conditions but reduction effects of CR were seen only in HFD groups. HFD and SD feeding increased hemodynamic parameters, ANP (atrial natriuretic peptide) mRNA expression, and TGF-β1(transforming growth factor-beta 1) protein level in the OVX animals, while CR and E2 reduced these factors. Cardiomyocyte diameter and hydroxyproline content were increased in the OVX-HFD groups. Nevertheless, CR and E2 decreased these indicators. The results showed that CR and E2 treatment reduced obesity-induced-cardiac hypertrophy in ovariectomized groups (20% and 24% respectively). CR appears to have almost as reducing effects as estrogen therapy on cardiac hypertrophy. The findings suggest that CR can be considered a therapeutic candidate for postmenopausal cardiovascular disease.

Preclinical models of radiation-induced cardiac toxicity: Potential mechanisms and biomarkers

Radiation therapy (RT) is an important modality in cancer treatment with >50% of cancer patients undergoing RT for curative or palliative intent. In patients with breast, lung, and esophageal cancer, as well as mediastinal malignancies, incidental RT dose to heart or vascular structures has been linked to the development of Radiation-Induced Heart Disease (RIHD) which manifests as ischemic heart disease, cardiomyopathy, cardiac dysfunction, and heart failure. Despite the remarkable progress in the delivery of radiotherapy treatment, off-target cardiac toxicities are unavoidable. One of the best-studied pathological consequences of incidental exposure of the heart to RT is collagen deposition and fibrosis, leading to the development of radiation-induced myocardial fibrosis (RIMF). However, the pathogenesis of RIMF is still largely unknown. Moreover, there are no available clinical approaches to reverse RIMF once it occurs and it continues to impair the quality of life of long-term cancer survivors. Hence, there is an increasing need for more clinically relevant preclinical models to elucidate the molecular and cellular mechanisms involved in the development of RIMF. This review offers an insight into the existing preclinical models to study RIHD and the suggested mechanisms of RIMF, as well as available multi-modality treatments and outcomes. Moreover, we summarize the valuable detection methods of RIHD/RIMF, and the clinical use of sensitive radiographic and circulating biomarkers.

Targeting Myocardial Fibrosis—A Magic Pill in Cardiovascular Medicine?

Fibrosis, characterized by an excessive accumulation of extracellular matrix, has long been seen as an adaptive process that contributes to tissue healing and regeneration. More recently, however, cardiac fibrosis has been shown to be a central element in many cardiovascular diseases (CVDs), contributing to the alteration of cardiac electrical and mechanical functions in a wide range of clinical settings. This paper aims to provide a comprehensive review of cardiac fibrosis, with a focus on the main pathophysiological pathways involved in its onset and progression, its role in various cardiovascular conditions, and on the potential of currently available and emerging therapeutic strategies to counteract the development and/or progression of fibrosis in CVDs. We also emphasize a number of questions that remain to be answered, and we identify hotspots for future research.

Dapagliflozin Attenuates Myocardial Fibrosis by Inhibiting the TGF-β1/Smad Signaling Pathway in a Normoglycemic Rabbit Model of Chronic Heart Failure

Recent studies have shown that sodium-glucose cotransporter-2 (SGLT2) inhibitors play a beneficial role for normoglycemic patients with heart failure (HF). However, the underlying mechanism remains largely unexplored. In the present study, we aimed to investigate the cardioprotective effect of SGLT2 inhibitors in a normoglycemic rabbit model of chronic heart failure (CHF) and its potential mechanism was also explored. A total of 24 male New Zealand white rabbits were randomly divided into the sham group, HF group, perindopril group, and dapagliflozin (DAPA) group. The normoglycemic CHF model was established by aortic constriction for 12 weeks. In the 13th week, DAPA (1 mg/kg/day) or perindopril (0.5 mg/kg/day) was administered by oral gavage daily for 10 weeks. Both the sham group and HF group were given normal saline via gavage. After 10 weeks, the heart structure and function were evaluated by echocardiography and plasma NT-proBNP. Moreover, cardiac fibrosis was analyzed using immunohistochemistry, Masson’s trichrome staining, and Western blotting analysis. The results showed that DAPA improved the myocardial structure and function of normoglycemic CHF rabbits and ameliorated myocardial fibrosis. Further study indicated that DAPA suppressed cardiac fibrosis by inhibiting the transforming growth factor β1 (TGF-β1)/Smad signaling pathway. Collectively, our findings showed that DAPA could ameliorate cardiac fibrosis in normoglycemic CHF rabbits by inhibiting the TGF-β1/Smad signaling pathway.

miR-29b ameliorates atrial fibrosis in rats with atrial fibrillation by targeting TGFβRΙ and inhibiting the activation of Smad-2/3 pathway

OBJECTIVE

Atrial fibrillation (AF) is a major cause of stroke with lifetime risks. microRNAs (miRNAs) are associated with AF attenuation, yet the mechanism remains unknown. This study investigated the functional mechanism of miR-29b in atrial fibrosis in AF.

METHODS

The AF rat model was established by a 7-day intravenous injection of Ach-CaCl₂ mixture. AF rats were injected with adeno-associated virus (AAv)-miR-29b and TGFβRΙ overexpression plasmid. AF duration was recorded by electrocardiogram. Atrial fibrosis was observed by Masson staining. Expressions of COL1A1, COL3A1, TGFβRΙ, TGFβΙ, miR-29b and Smad-2/3 pathway-related proteins in atrial tissues were detected by RT-qPCR and Western blot. Binding sites of miR-29b and TGFβRΙ were predicted and their target relationship was verified by dual-luciferase reporter assay.

RESULTS

miR-29b was poorly expressed and expressions of COL1A1, COL3A1, TGFβRΙ, and TGFβ1 were increased in atrial tissues of AF rats. miR-29b overexpression alleviated atrial fibrosis, reduced expressions of COL1A1, COL3A1, and TGFβ1, and shortened AF duration in AF rats. TGFβRΙ was highly expressed in atrial tissues of AF rats. miR-29b targeted TGFβRΙ. TGFβRΙ overexpression overcame the improving effect of miR-29b overexpression on AF. miR-29b overexpression decreased ratios of p-Smad-2/3 and Smad-2/3 and inhibited the Smad-2/3 pathway.

CONCLUSION

miR-29b might mitigate atrial fibrosis in AF rats by targeting TGFβRΙ and inhibiting the Smad-2/3 pathway.

Role of Cardiac Fibroblasts in Cardiac Injury and Repair

PURPOSE OF REVIEW

The pathological remodeling of cardiac tissue after injury or disease leads to scar formation. Our knowledge of the role of nonmyocytes, especially fibroblasts, in cardiac injury and repair continues to increase with technological advances in both experimental and clinical studies. Here, we aim to elaborate on cardiac fibroblasts by describing their origins, dynamic cellular states after injury, and heterogeneity in order to understand their role in cardiac injury and repair.

RECENT FINDINGS

With the improvement in genetic lineage tracing technologies and the capability to profile gene expression at the single-cell level, we are beginning to learn that manipulating a specific population of fibroblasts could mitigate severe cardiac fibrosis and promote cardiac repair after injury. Cardiac fibroblasts play an indispensable role in tissue homeostasis and in repair after injury. Activated fibroblasts or myofibroblasts have time-dependent impacts on cardiac fibrosis. Multiple signaling pathways are involved in modulating fibroblast states, resulting in the alteration of fibrosis. Modulating a specific population of cardiac fibroblasts may provide new opportunities for identifying novel treatment options for cardiac fibrosis.

MiRNA-Regulated Pathways for Hypertrophic Cardiomyopathy: Network-Based Approach to Insight into Pathogenesis

Hypertrophic cardiomyopathy (HCM) is the most common hereditary heart disease. The wide spread of high-throughput sequencing casts doubt on its monogenic nature, suggesting the presence of mechanisms of HCM development independent from mutations in sarcomeric genes. From this point of view, HCM may arise from the interactions of several HCM-associated genes, and from disturbance of regulation of their expression. We developed a bioinformatic workflow to study the involvement of signaling pathways in HCM development through analyzing data on human heart-specific gene expression, miRNA-target gene interactions, and protein-protein interactions, available in open databases. Genes regulated by a pool of miRNAs contributing to human cardiac hypertrophy, namely hsa-miR-1-3p, hsa-miR-19b-3p, hsa-miR-21-5p, hsa-miR-29a-3p, hsa-miR-93-5p, hsa-miR-133a-3p, hsa-miR-155-5p, hsa-miR-199a-3p, hsa-miR-221-3p, hsa-miR-222-3p, hsa-miR-451a, and hsa-miR-497-5p, were considered. As a result, we pinpointed a module of TGFβ-mediated SMAD signaling pathways, enriched by targets of the selected miRNAs, that may contribute to the cardiac remodeling in HCM. We suggest that the developed network-based approach could be useful in providing a more accurate glimpse on pathological processes in the disease pathogenesis.

Antifibrotic Effects of (-)-Epicatechin on High Glucose Stimulated Cardiac Fibroblasts

Cardiac fibrosis is one of the hallmarks of a diabetic cardiomyopathy. When activated, cardiac fibroblasts (CFs) increase the production of extracellular matrix proteins. Transforming growth factor (TGF)-β1 is known to mediate cardiac fibrosis through the SMAD pathway. High glucose (HG = 25 mM) cell culture media can activate CFs using TGF-β1. There is a need to identify effective antifibrotic agents. Studies in animals indicate that treatment with (-)-epicatechin (Epi) appears capable of reducing myocardial fibrosis. Epi binds to G-protein coupled estrogen receptor (GPER) and activates downstream pathways. We evaluated the potential of Epi to mitigate the development of a profibrotic phenotype in HG stimulated CFs. CF primary cultures were isolated from young male rats and were exposed for up to 48 h HG media and treated with vehicle or 1 μM Epi. Relevant profibrotic end points were measured by the use of various biochemical assays. HG exposure of CFs increased TGF-β1 protein levels by ∼15%, fibronectin ∼25%, urea levels ∼60%, proline incorporation ∼70%, and total collagen ∼15%. Epi treatment was able to significantly block HG induced increases in TGF-β1, fibronectin, urea, proline, and total collagen protein levels. GPER levels were reduced by HG and restored in CFs treated with Epi an effect associated with the activation (i.e., phosphorylation) of c-Src. Epi treatment also reverted SMAD levels. Altogether, results demonstrate that CFs cultured in HG acquire a profibrotic phenotype, which is blocked by Epi an effect, likely mediated at least, in part, by GPER effects on the SMAD/TGF-β1 pathway.

Reawakening the Intrinsic Cardiac Regenerative Potential: Molecular Strategies to Boost Dedifferentiation and Proliferation of Endogenous Cardiomyocytes

Despite considerable efforts carried out to develop stem/progenitor cell-based technologies aiming at replacing and restoring the cardiac tissue following severe damages, thus far no strategies based on adult stem cell transplantation have been demonstrated to efficiently generate new cardiac muscle cells. Intriguingly, dedifferentiation, and proliferation of pre-existing cardiomyocytes and not stem cell differentiation represent the preponderant cellular mechanism by which lower vertebrates spontaneously regenerate the injured heart. Mammals can also regenerate their heart up to the early neonatal period, even in this case by activating the proliferation of endogenous cardiomyocytes. However, the mammalian cardiac regenerative potential is dramatically reduced soon after birth, when most cardiomyocytes exit from the cell cycle, undergo further maturation, and continue to grow in size. Although a slow rate of cardiomyocyte turnover has also been documented in adult mammals, both in mice and humans, this is not enough to sustain a robust regenerative process. Nevertheless, these remarkable findings opened the door to a branch of novel regenerative approaches aiming at reactivating the endogenous cardiac regenerative potential by triggering a partial dedifferentiation process and cell cycle re-entry in endogenous cardiomyocytes. Several adaptations from intrauterine to extrauterine life starting at birth and continuing in the immediate neonatal period concur to the loss of the mammalian cardiac regenerative ability. A wide range of systemic and microenvironmental factors or cell-intrinsic molecular players proved to regulate cardiomyocyte proliferation and their manipulation has been explored as a therapeutic strategy to boost cardiac function after injuries. We here review the scientific knowledge gained thus far in this novel and flourishing field of research, elucidating the key biological and molecular mechanisms whose modulation may represent a viable approach for regenerating the human damaged myocardium.

Bone Morphogenetic Protein 7 Gene Delivery Improves Cardiac Structure and Function in a Murine Model of Diabetic Cardiomyopathy

Diabetes is a major contributor to the increasing burden of heart failure prevalence globally, at least in part due to a disease process termed diabetic cardiomyopathy. Diabetic cardiomyopathy is characterised by cardiac structural changes that are caused by chronic exposure to the diabetic milieu. These structural changes are a major cause of left ventricular (LV) wall stiffness and the development of LV dysfunction. In the current study, we investigated the therapeutic potential of a cardiac-targeted bone morphogenetic protein 7 (BMP7) gene therapy, administered once diastolic dysfunction was present, mimicking the timeframe in which clinical management of the cardiomyopathy would likely be desired. Following 18 weeks of untreated diabetes, mice were administered with a single tail-vein injection of recombinant adeno-associated viral vector (AAV), containing the BMP7 gene, or null vector. Our data demonstrated, after 8 weeks of treatment, that rAAV6-BMP7 treatment exerted beneficial effects on LV functional and structural changes. Importantly, diabetes-induced LV dysfunction was significantly attenuated by a single administration of rAAV6-BMP7. This was associated with a reduction in cardiac fibrosis, cardiomyocyte hypertrophy and cardiomyocyte apoptosis. In conclusion, BMP7 gene therapy limited pathological remodelling in the diabetic heart, conferring an improvement in cardiac function. These findings provide insight for the potential development of treatment strategies urgently needed to delay or reverse LV pathological remodelling in the diabetic heart.

Modulation of Cardiac Arrhythmogenesis by Epicardial Adipose Tissue: JACC State-of-the-Art Review

Obesity is a significant risk factor for arrhythmic cardiovascular death. Interactions between epicardial adipose tissue (EAT) and myocytes are thought to play a key role in the development of arrhythmias. In this review, the authors investigate the influence of EAT on arrhythmogenesis. First, they summarize electrocardiographic evidence showing the association between increased EAT volume and atrial and ventricular conduction delay. Second, they detail the structural cross talk between EAT and the heart and its arrhythmogenicity. Adipose tissue infiltration within the myocardium constitutes an anatomical obstacle to cardiac excitation. It causes activation delay and increases the risk of arrhythmias. Intercellular electrical coupling between cardiomyocytes and EAT can further slow conduction and increase the risk of block, favoring re-entry and arrhythmias. Finally, EAT secretes multiple substances that influence cardiomyocyte electrophysiology either by modulating ion currents and electrical coupling or by stimulating fibrosis. Thus, structural and paracrine cross talk between EAT and cardiomyocytes facilitates arrhythmias.

PKM2 promotes angiotensin-II-induced cardiac remodelling by activating TGF-β/Smad2/3 and Jak2/Stat3 pathways through oxidative stress

Hypertensive cardiac remodelling is a common cause of heart failure. However, the molecular mechanisms regulating cardiac remodelling remain unclear. Pyruvate kinase isozyme type M2 (PKM2) is a key regulator of the processes of glycolysis and oxidative phosphorylation, but the roles in cardiac remodelling remain unknown. In the present study, we found that PKM2 was enhanced in angiotensin II (Ang II)-treated cardiac fibroblasts and hypertensive mouse hearts. Suppression of PKM2 by shikonin alleviated cardiomyocyte hypertrophy and fibrosis in Ang-II-induced cardiac remodelling in vivo. Furthermore, inhibition of PKM2 markedly attenuated the function of cardiac fibroblasts including proliferation, migration and collagen synthesis in vitro. Mechanistically, suppression of PKM2 inhibited cardiac remodelling by suppressing TGF-β/Smad2/3, Jak2/Stat3 signalling pathways and oxidative stress. Together, this study suggests that PKM2 is an aggravator in Ang-II-mediated cardiac remodelling. The negative modulation of PKM2 may provide a promising therapeutic approach for hypertensive cardiac remodelling.

Selective Inhibition of NLRP3 Inflammasome Reverses Pressure Overload-Induced Pathological Cardiac Remodeling by Attenuating Hypertrophy, Fibrosis, and Inflammation

Activation of the NLRP3 inflammasome promotes pathological cardiac remodeling induced by pressure overload. However, the therapeutic effects of NLRP3 inhibition after cardiac remodeling remain unknown. The present study aimed to investigate whether the selective NLRP3 inhibitor, MCC950, could reverse transverse aortic constriction (TAC)-induced cardiac remodeling. Mice were divided into four groups based on the treatment given: sham, sham + MCC950, TAC, and TAC + MCC950. MCC950 (10 mg/kg, intraperitoneal injection, once per day) was administered from two weeks after TAC or sham surgery for four weeks. Echocardiography, histological analysis, RT-PCR, and Western blotting were performed to explore the function of MCC950 after TAC. We found that MCC950 reversed cardiac dysfunction after TAC. MCC950 attenuated cardiac hypertrophy by down-regulating calcineurin expression and inhibiting MAPK activation. Further, it also alleviated cardiac fibrosis post-TAC by inhibiting the TGF-β/Smad4 pathway, and reduced cardiac inflammation and macrophage infiltration post-TAC, including both M1 and M2 macrophages. Taken together, MCC950 can attenuate cardiac remodeling due to pressure overload by inhibiting hypertrophy, fibrosis, and inflammation. Our study provides a basis for the clinical application of NLRP3 inhibitors in the treatment of non-ischemic heart failure.

Excess TGF-β1 Drives Cardiac Mesenchymal Stromal Cells to a Pro-Fibrotic Commitment in Arrhythmogenic Cardiomyopathy

Arrhythmogenic Cardiomyopathy (ACM) is characterized by the replacement of the myocardium with fibrotic or fibro-fatty tissue and inflammatory infiltrates in the heart. To date, while ACM adipogenesis is a well-investigated differentiation program, ACM-related fibrosis remains a scientific gap of knowledge. In this study, we analyze the fibrotic process occurring during ACM pathogenesis focusing on the role of cardiac mesenchymal stromal cells (C-MSC) as a source of myofibroblasts. We performed the ex vivo studies on plasma and right ventricular endomyocardial bioptic samples collected from ACM patients and healthy control donors (HC). In vitro studies were performed on C-MSC isolated from endomyocardial biopsies of both groups. Our results revealed that circulating TGF-β1 levels are significantly higher in the ACM cohort than in HC. Accordingly, fibrotic markers are increased in ACM patient-derived cardiac biopsies compared to HC ones. This difference is not evident in isolated C-MSC. Nevertheless, ACM C-MSC are more responsive than HC ones to TGF-β1 treatment, in terms of pro-fibrotic differentiation and higher activation of the SMAD2/3 signaling pathway. These results provide the novel evidence that C-MSC are a source of myofibroblasts and participate in ACM fibrotic remodeling, being highly responsive to ACM-characteristic excess TGF-β1.

Fibrosis after Myocardial Infarction: An Overview on Cellular Processes, Molecular Pathways, Clinical Evaluation and Prognostic Value

The ischemic injury caused by myocardial infarction activates a complex healing process wherein a powerful inflammatory response and a reparative phase follow and balance each other. An intricate network of mediators finely orchestrate a large variety of cellular subtypes throughout molecular signaling pathways that determine the intensity and duration of each phase. At the end of this process, the necrotic tissue is replaced with a fibrotic scar whose quality strictly depends on the delicate balance resulting from the interaction between multiple actors involved in fibrogenesis. An inflammatory or reparative dysregulation, both in term of excess and deficiency, may cause ventricular dysfunction and life-threatening arrhythmias that heavily affect clinical outcome. This review discusses cellular process and molecular signaling pathways that determine fibrosis and the imaging technique that can characterize the clinical impact of this process in-vivo.

Glucose-dependent insulinotropic polypeptide inhibits cardiac hypertrophy and fibrosis in diabetic mice via suppression of TGF-β2

Diabetic cardiomyopathy is associated with an increased risk for heart failure and death in patients with diabetes. We investigated here whether and how GIP attenuated cardiac hypertrophy and fibrosis in diabetic mice with obesity. Diabetic db/db mice at 7 weeks old were infused with vehicle or GIP (50 nmol/kg/day) for 6 weeks, and hearts were collected for histological and RT-PCR analyzes. Cardiomyocytes isolated from neonatal mice were incubated with or without 300 nM [D-Ala2]-GIP, 30 mM glucose, or 100 μg/mL advanced glycation end products (AGEs) for RT-PCR and lucigenin assays. Compared with non-diabetic mice, diabetic mice exhibited larger left ventricle wall thickness and cardiomyocyte sizes and more fibrotic areas in association with up-regulation of myosin heavy chain β (β-Mhc) and transforming growth factor-beta2 (Tgf-β2) mRNA levels, all of which were inhibited by GIP infusion. High glucose increased NADPH oxidase-driven superoxide generation and up-regulated β-Mhc, Tgf-β2, and receptor for AGEs mRNA levels in cardiomyocytes, and augmented the AGE-induced β-Mhc gene expression. [D-Ala2]-GIP attenuated all of the deleterious effects of high glucose and/or AGEs on cardiomyocytes. Our present findings suggest that GIP could inhibit cardiac hypertrophy and fibrosis in diabetic mice via suppression of TGF-β2.

Celecoxib alleviates pathological cardiac hypertrophy and fibrosis via M1-like macrophage infiltration in neonatal mice

Cardiac hypertrophy is an adaptive response to all forms of heart disease, including hypertension, myocardial infarction, and cardiomyopathy. Cyclooxygenase-2 (COX-2) overexpression results in inflammatory response, cardiac cell apoptosis, and hypertrophy in adult heart after injury. However, immune response-mediated cardiac hypertrophy and fibrosis have not been well documented in injured neonatal heart. This study showed that cardiac hypertrophy and fibrosis are significantly attenuated in celecoxib (a selective COX-2 inhibitor)-treated P8 ICR mice after cryoinjury. Molecular and cellular profiling of immune response shows that celecoxib inhibits the production of cytokines and the expression of adhesion molecular genes, increases the recruitment of M1-like macrophage at wound site, and alleviates cardiac hypertrophy and fibrosis. Furthermore, celecoxib administration improves cardiac function at 4 weeks after injury. These results demonstrate that COX-2 inhibition promotes the recruitment of M1-like macrophages during early wound healing, which may contribute to the suppression of cardiac hypertrophy and fibrosis after injury.

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Cryoinjury successfully induces cardiac hypertrophy and fibrosis in P8 ICR mice

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COX-2 inhibition alleviates cardiac hypertrophy and fibrosis after cryoinjury

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MCP-1 significantly increases in COX-2 inhibition

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COX-2 inhibition improves cardiac repair in P8 ICR mice by recruiting M1-like macrophages

Diverse origins and activation of fibroblasts in cardiac fibrosis

Cardiac fibroblasts (cFBs) have emerged as a heterogenous cell population. Fibroblasts are considered the main cell source for synthesis of the extracellular matrix (ECM) and as such a dysregulation in cFB function, activity, or viability can lead to disrupted ECM structure or fibrosis. Fibrosis can be initiated in response to different injuries and stimuli, and can be reparative (beneficial) or reactive (damaging). FBs need to be activated to myofibroblasts (MyoFBs) which have augmented capacity in synthesizing ECM proteins, causing fibrosis. In addition to the resident FBs in the myocardium, a number of other cells (pericytes, fibrocytes, mesenchymal, and hematopoietic cells) can transform into MyoFBs, further driving the fibrotic response. Multiple molecules including hormones, cytokines, and growth factors stimulate this process leading to generation of activated MyoFBs. Contribution of different cell types to cFBs and MyoFBs can result in an exponential increase in the number of MyoFBs and an accelerated pro-fibrotic response. Given the diversity of the cell sources, and the array of interconnected signalling pathways that lead to formation of MyoFBs and subsequently fibrosis, identifying a single target to limit the fibrotic response in the myocardium has been challenging. This review article will delineate the importance and relevance of fibroblast heterogeneity in mediating fibrosis in different models of heart failure and will highlight important signalling pathways implicated in myofibroblast activation.

Celiprolol Treatment in Patients with Vascular Ehlers-Danlos Syndrome

OBJECTIVE

Vascular Ehlers-Danlos syndrome (vEDS) is a rare monogenetic disease caused by pathogenic variants in procollagen 3A1. Arterial rupture is the most serious clinical manifestation. A randomised controlled trial, the Beta-Blockers in Ehlers-Danlos Syndrome Treatment (BBEST) trial, reported a significant protective effect of the beta blocker celiprolol. The aim was to study the outcome of celiprolol treatment in a cohort of Swedish patients with vEDS.

METHODS

Uppsala is a national referral centre for patients with vEDS. They are assessed by vascular surgeons, angiologists, and clinical geneticists. Family history, previous and future clinical events, medication, and side effects are registered. Celiprolol was administered twice daily and titrated up to a maximum dose of 400 mg daily. Logistic regression was used to analyse predictors of vascular events.

RESULTS

Forty patients with pathogenic sequence variants in COL3A1 were offered treatment with celiprolol in the period 2011-2019. The median follow up was 22 months (range 1-98 months); total follow up was 106 patient years. In two patients, uptitration of the dose is ongoing. Of the remaining 38, 26 (65%) patients reached the target dose of 400 mg daily. Dose uptitration was unsuccessful in six patients because of side effects; one died before reaching the maximum dose, and five terminated the treatment. Five major vascular events occurred; four were fatal (ruptured ascending aorta; aortic rupture after type B dissection; ruptured cerebral aneurysm; and ruptured pulmonary artery). One bled from a branch of the internal iliac artery, which was successfully coiled endovascularly. The annual risk of a major vascular event was 4.7% (n = 5/106), similar to the treatment arm of the BBEST trial (5%) and lower than in the control arm of the same trial (12%). No significant predictor of vascular events was identified.

CONCLUSION

Treatment with celiprolol is tolerated in most patients with vEDS. Despite fatal vascular events, these observations suggest that celiprolol may have a protective effect in vEDS.

Biphasic changes in TGF-β1 signaling drive NSAID-induced multi-organ damage

The clinical utility of non-steroidal anti-inflammatory drugs (NSAIDs), used extensively worldwide, is limited by adverse cardiac events resulting from chronic drug exposure. Here, we provide evidence identifying transforming growth factor β (TGF-β1), released from multiple tissues, as a critical driver of NSAID-induced multi-organ damage. Biphasic changes in TGF-β1 levels in liver and heart were accompanied by ROS generation, cell death, fibrotic remodeling, compromised cardiac contractility and elevated liver enzymes. Pharmacological inhibition of TGF-βRI signaling markedly improved heart and liver function and increased overall survival of animals exposed to multiple NSAIDs, effects likely mediated by reductions in NOX-dependent ROS generation. Notably, the beneficial impact of TGF-βRI blockade was confined to a critical window wherein consecutive, but not concurrent, inhibitor administration improved cardiac and hepatic endpoints. Remarkably, in addition to ameliorating indomethacin-mediated myofilament disruptions, cardiac TGF-βRI knockdown lead to drastic reductions in TGF-β1 production accompanied by lessening in intestinal lesioning underscoring the importance of endocrine TGF-β1 signaling in NSAID-driven tissue injury. Indeed, gastric ulceration was associated with a higher incidence of cardiac complications in a human cohort underscoring the critical importance of circulation-facilitated peripheral organ system interconnectedness in efforts seeking to mitigate the toxic side effects of chronic NSAID use.

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.

ADAMTS16 activates latent TGF-β, accentuating fibrosis and dysfunction of the pressure-overloaded heart

AIMS

Cardiac fibrosis is a major cause of heart failure (HF), and mediated by the differentiation of cardiac fibroblasts into myofibroblasts. However, limited tools are available to block cardiac fibrosis. ADAMTS16 is a member of the ADAMTS superfamily of extracellular protease enzymes involved in extracellular matrix (ECM) degradation and remodelling. In this study, we aimed to establish ADAMTS16 as a key regulator of cardiac fibrosis.

METHODS AND RESULTS

Western blot and qRT-PCR analyses demonstrated that ADAMTS16 was significantly up-regulated in mice with transverse aortic constriction (TAC) associated with left ventricular hypertrophy and HF, which was correlated with increased expression of Mmp2, Mmp9, Col1a1, and Col3a1. Overexpression of ADAMTS16 accelerated the AngII-induced activation of cardiac fibroblasts into myofibroblasts. Protein structural analysis and co-immunoprecipitation revealed that ADAMTS16 interacted with the latency-associated peptide (LAP)-transforming growth factor (TGF)-β via a RRFR motif. Overexpression of ADAMTS16 induced the activation of TGF-β in cardiac fibroblasts; however, the effects were blocked by a mutation of the RRFR motif to IIFI, knockdown of Adamts16 expression, or a TGF-β-neutralizing antibody (ΝAb). The RRFR tetrapeptide, but not control IIFI peptide, blocked the interaction between ADAMTS16 and LAP-TGF-β, and accelerated the activation of TGF-β in cardiac fibroblasts. In TAC mice, the RRFR tetrapeptide aggravated cardiac fibrosis and hypertrophy by up-regulation of ECM proteins, activation of TGF-β, and increased SMAD2/SMAD3 signalling, however, the effects were blocked by TGF-β-NAb.

CONCLUSION

ADAMTS16 promotes cardiac fibrosis, cardiac hypertrophy, and HF by facilitating cardiac fibroblasts activation via interacting with and activating LAP-TGF-β signalling. The RRFR motif of ADAMTS16 disrupts the interaction between ADAMTS16 and LAP-TGF-β, activates TGF-β, and aggravated cardiac fibrosis and hypertrophy. This study identifies a novel regulator of TGF-β signalling and cardiac fibrosis, and provides a new target for the development of therapeutic treatment of cardiac fibrosis and HF.

Inflammatory responses mediate brain-heart interaction after ischemic stroke in adult mice

Stroke induces cardiac dysfunction which increases post stroke mortality and morbidity particularly in aging population. Here, we investigated the effects of inflammatory responses as underlying mediators of cardiac dysfunction after stroke in adult mice. Adult (eight-to-nine months) male C57BL/6 mice were subjected to photothrombotic stroke. To test whether immunoresponse to stroke leads to cardiac dysfunction, splenectomy was performed with stroke. Immunohistochemistry, flow cytometry, PCR, ELISA and echocardiography were performed. We found marginal cardiac dysfunction at acute phase and significant cardiac dysfunction at chronic phase of stroke as indicated by significant decrease of left ventricular ejection fraction (LVEF) and shortening fraction (LVSF). Stroke significantly increases macrophage infiltration into the heart and increases IL-1β, IL-6, MCP-1, TGF-β and macrophage-associated inflammatory cytokine levels in the heart as well as induces cardiac-fibrosis and hypertrophy. Splenectomy with stroke significantly reduces macrophage infiltration into heart, decreases inflammatory factor expression in the heart, decreases cardiac hypertrophy and fibrosis, as well as significantly improves cardiac function compared to non-splenectomized adult stroke mice. Therefore, cerebral ischemic stroke in adult mice induces chronic cardiac dysfunction and secondary immune response may contribute to post stroke cardiac dysfunction.

Activated Cardiac Fibroblasts Control Contraction of Human Fibrotic Cardiac Microtissues by a β-Adrenoreceptor-Dependent Mechanism

Cardiac fibrosis represents a serious clinical problem. Development of novel treatment strategies is currently restricted by the lack of the relevant experimental models in a human genetic context. In this study, we fabricated self-aggregating, scaffold-free, 3D cardiac microtissues using human inducible pluripotent stem cell (iPSC)-derived cardiomyocytes and human cardiac fibroblasts. Fibrotic condition was obtained by treatment of cardiac microtissues with profibrotic cytokine transforming growth factor β1 (TGF-β1), preactivation of foetal cardiac fibroblasts with TGF-β1, or by the use of cardiac fibroblasts obtained from heart failure patients. In our model, TGF-β1 effectively induced profibrotic changes in cardiac fibroblasts and in cardiac microtissues. Fibrotic phenotype of cardiac microtissues was inhibited by treatment with TGF-β-receptor type 1 inhibitor SD208 in a dose-dependent manner. We observed that fibrotic cardiac microtissues substantially increased the spontaneous beating rate by shortening the relaxation phase and showed a lower contraction amplitude. Instead, no changes in action potential profile were detected. Furthermore, we demonstrated that contraction of human cardiac microtissues could be modulated by direct electrical stimulation or treatment with the β-adrenergic receptor agonist isoproterenol. However, in the absence of exogenous agonists, the β-adrenoreceptor blocker nadolol decreased beating rate of fibrotic cardiac microtissues by prolonging relaxation time. Thus, our data suggest that in fibrosis, activated cardiac fibroblasts could promote cardiac contraction rate by a direct stimulation of β-adrenoreceptor signalling. In conclusion, a model of fibrotic cardiac microtissues can be used as a high-throughput model for drug testing and to study cellular and molecular mechanisms of cardiac fibrosis.

Human umbilical cord blood cells rescued traumatic brain injury-induced cardiac and neurological deficits

Background

Traumatic brain injury (TBI) evokes neurological deficits and induces cardiac dysfunction. Treatment with human umbilical cord blood cells (HUCBCs) represents a potential therapeutic strategy for TBI-induced neurological deficits. The present study aimed to determine whether HUCBCs could ameliorate the cardiac dysfunction and neurological deficits induced by TBI.

Methods

Adult male C57BL/6J mice were subjected to controlled cortical impact (CCI)-induced TBI and were treated with either HUCBCs (1×10⁶) or phosphate-buffered saline (PBS), via tail vein injections, 3 days after TBI. Neurological and cognitive functions were subsequently evaluated at multiple time points after TBI and cardiac function was assessed by echocardiography 3 and 30 days after TBI. Brain and heart tissues were paraffin-embedded 30 days after TBI. Hematoxylin and eosin (H&E) staining was performed on brain tissue sections to calculate the brain damage volume, and Picro Sirius Red (PSR) staining was performed on heart tissue sections to evaluate myocardial fibrosis. Terminal deoxynucleotide transferase dUTP nick end labeling (TUNEL) staining was employed to assess cell apoptosis 30 days after TBI. Transforming growth factor-beta (TGF-β) and NADPH oxidase-2 (NOX2) levels were assessed to evaluate inflammation and oxidative stress levels 30 days after TBI.

Results

TBI elicited acute and chronic cardiac deficits, identified by decreased left ventricular ejection fraction (LVEF) and fractional shortening (LVFS) values 3 and 30 days after TBI, in addition to neurological and cognitive deficits. TBI mice treated with HUCBCs exhibited enhanced LVEF and FS values 30 days after TBI compared with untreated TBI controls. HUCBC treatment significantly improved neurological and cognitive functions and reduced cardiomyocyte apoptosis, inflammatory response, oxidative stress, and cardiac fibrosis in heart tissues 30 days after TBI.

Conclusions

TBI induced both neurological deficits and cardiac dysfunction in mice, which were ameliorated by HUCBC treatment. The anti-inflammatory activities of HUCBCs may contribute to these observed therapeutic effects.

Fibrosis in Arrhythmogenic Cardiomyopathy: The Phantom Thread in the Fibro-Adipose Tissue

Arrhythmogenic cardiomyopathy (ACM) is an inherited heart disorder, predisposing to malignant ventricular arrhythmias leading to sudden cardiac death, particularly in young and athletic patients. Pathological features include a progressive loss of myocardium with fibrous or fibro-fatty substitution. During the last few decades, different clinical aspects of ACM have been well investigated but still little is known about the molecular mechanisms that underlie ACM pathogenesis, leading to these phenotypes. In about 50% of ACM patients, a genetic mutation, predominantly in genes that encode for desmosomal proteins, has been identified. However, the mutation-associated mechanisms, causing the observed cardiac phenotype are not always clear. Until now, the attention has been principally focused on the study of molecular mechanisms that lead to a prominent myocardium adipose substitution, an uncommon marker for a cardiac disease, thus often recognized as hallmark of ACM. Nonetheless, based on Task Force Criteria for the diagnosis of ACM, cardiomyocytes death associated with fibrous replacement of the ventricular free wall must be considered the main tissue feature in ACM patients. For this reason, it urges to investigate ACM cardiac fibrosis. In this review, we give an overview on the cellular effectors, possible triggers, and molecular mechanisms that could be responsible for the ventricular fibrotic remodeling in ACM patients.

CD133+Exosome Treatment Improves Cardiac Function after Stroke in Type 2 Diabetic Mice

Cardiac complications post-stroke are common, and diabetes exacerbates post-stroke cardiac injury. In this study, we tested whether treatment with exosomes harvested from human umbilical cord blood derived CD133+ cells (CD133+Exo) improves cardiac function in type 2 diabetes mellitus (T2DM) stroke mice. Adult (3-4 m), male, BKS.Cg-m+/+Lepr^db/J (db/db, T2DM) and non-DM (db+) mice were randomized to sham or photothrombotic stroke groups. T2DM-stroke mice were treated with phosphate-buffered saline (PBS) or CD133+Exo (20 μg, i.v.) at 3 days after stroke. T2DM sham and T2DM+CD133+Exo treatment groups were included as controls. Echocardiography was performed, and mice were sacrificed at 28 days after stroke. Cardiomyocyte hypertrophy, myocardial capillary density, interstitial fibrosis, and inflammatory factor expression were measured in the heart. MicroRNA-126 expression and its target gene expression were measured in the heart. T2DM mice exhibit significant cardiac deficits such as decreased left ventricular ejection fraction (LVEF) and shortening fraction (LVSF), increased left ventricular diastolic dimension (LVDD), and reduced heart rate compared to non-DM mice. Stroke in non-DM and T2DM mice significantly decreases LVEF compared to non-DM and T2DM-sham, respectively. Cardiac dysfunction is worse in T2DM-stroke mice compared to non-DM-stroke mice. CD133+Exo treatment of T2DM-stroke mice significantly improves cardiac function identified by increased LVEF and decreased LVDD compared to PBS treated T2DM-stroke mice. In addition, CD133+Exo treatment significantly decreases body weight and blood glucose but does not decrease lesion volume in T2DM-stroke mice. CD133+Exo treatment of T2DM mice significantly decreases body weight and blood glucose but does not improve cardiac function. CD133+Exo treatment in T2DM-stroke mice significantly decreases myocardial cross-sectional area, interstitial fibrosis, transforming growth factor beta (TGF-β), numbers of M1 macrophages, and oxidative stress markers 4-HNE (4-hydroxynonenal) and NADPH oxidase 2 (NOX2) in heart tissue. CD133+Exo treatment increases myocardial capillary density in T2DM-stroke mice as well as upregulates endothelial cell capillary tube formation in vitro. MiR-126 is highly expressed in CD133+Exo compared to exosomes derived from endothelial cells. Compared to PBS treatment, CD133+Exo treatment significantly increases miR-126 expression in the heart and decreases its target gene expression such as Sprouty-related, EVH1 domain-containing protein 1 (Spred-1), vascular cell adhesion protein (VCAM), and monocyte chemoattractant protein 1 (MCP1) in the heart of T2DM-stroke mice. CD133+Exo treatment significantly improves cardiac function in T2DM-stroke mice. The cardio-protective effects of CD133+Exo in T2DM-stroke mice may be attributed at least in part to increasing miR-126 expression and decreasing its target protein expression in the heart, increased myocardial capillary density and decreased cardiac inflammatory factor expression.

Haploinsufficient Rock1+/- and Rock2+/- Mice Are Not Protected from Cardiac Inflammation and Postinflammatory Fibrosis in Experimental Autoimmune Myocarditis

Progressive cardiac fibrosis is a common cause of heart failure. Rho-associated, coiled-coil-containing protein kinases (ROCKs) have been shown to enhance fibrotic processes in the heart and in other organs. In this study, using wild-type, Rock1^+/− and Rock2^+/− haploinsufficient mice and mouse model of experimental autoimmune myocarditis (EAM) we addressed the role of ROCK1 and ROCK2 in development of myocarditis and postinflammatory fibrosis. We found that myocarditis severity was comparable in wild-type, Rock1^+/− and Rock2^+/− mice at day 21 of EAM. During the acute stage of the disease, hearts of Rock1^+/− mice showed unaffected numbers of CD11b⁺CD36⁺ macrophages, CD11b⁺CD36^–Ly6G^hiLy6c^hi neutrophils, CD11b⁺CD36^–Ly6G^–Ly6c^hi inflammatory monocytes, CD11b⁺CD36^–Ly6G^–Ly6c^– monocytes, CD11b⁺SiglecF⁺ eosinophils, CD11b⁺CD11c⁺ inflammatory dendritic cells and type I collagen-producing fibroblasts. Isolated Rock1^+/− cardiac fibroblasts treated with transforming growth factor-beta (TGF-β) showed attenuated Smad2 and extracellular signal-regulated kinase (Erk) phosphorylations that were associated with impaired upregulation of smooth muscle actin alpha (αSMA) protein. In contrast to cardiac fibroblasts, expanded Rock1^+/− heart inflammatory myeloid cells showed unaffected Smad2 activation but enhanced Erk phosphorylation following TGF-β treatment. Rock1^+/− inflammatory cells responded to TGF-β by a reduced transcriptional profibrotic response and failed to upregulate αSMA and fibronectin at the protein levels. Unexpectedly, in the EAM model wild-type, Rock1^+/− and Rock2^+/− mice developed a similar extent of cardiac fibrosis at day 40. In addition, hearts of the wild-type and Rock1^+/− mice showed comparable levels of cardiac vimentin, periostin and αSMA. In conclusion, despite the fact that ROCK1 regulates TGF-β-dependent profibrotic response, neither ROCK1 nor ROCK2 is critically involved in the development of postinflammatory fibrosis in the EAM model.

The association between microRNA-21 and hypertension-induced cardiac remodeling

Hypertension is a major public health problem among the aging population worldwide. It causes cardiac remodeling, including hypertrophy and interstitial fibrosis, which leads to development of hypertensive heart disease (HHD). Although microRNA-21 (miR-21) is associated with fibrogenesis in multiple organs, its contribution to cardiac remodeling in hypertension is poorly understood. Circulating miR-21 level was higher in patients with HHD than that in the control subjects. It also positively correlated with serum myocardial fibrotic markers. MiR-21 expression levels were significantly upregulated in the mice hearts after angiotensin II (Ang II) infusion or transverse aortic constriction (TAC) compared with control mice. Expression level of programmed cell death 4 (PDCD4), a main target of miR-21, was significantly decreased in Ang II infused mice and TAC mice compared with control mice. Expression levels of transcriptional activator protein 1 (AP-1) and transforming growth factor-β1 (TGF-β1), which were downstream targets of PDCD4, were increased in Ang II infused mice and TAC mice compared with control mice. In vitro, mirVana-miR-21-specific inhibitor attenuated Ang II-induced PDCD4 downregulation and contributed to subsequent deactivation of AP-1/TGF-β1 signaling pathway in neonatal rat cardiomyocytes. Thus, suppression of miR-21 prevents hypertrophic stimulation-induced cardiac remodeling by regulating PDCD4, AP-1, and TGF-β1 signaling pathway.

Transcriptome signature of ventricular arrhythmia in dilated cardiomyopathy reveals increased fibrosis and activated TP53

AIMS

One-third of DCM patients experience ventricular tachycardia (VT), but a clear biological basis for this has not been established. The purpose of this study was to identify transcriptome signatures and enriched pathways in the hearts of dilated cardiomyopathy (DCM) patients with VT.

METHODS AND RESULTS

We used RNA-sequencing in explanted heart tissue from 49 samples: 19 DCM patients with VT, 16 DCM patients without VT, and 14 non-failing controls. We compared each DCM cohort to the controls and identified the genes that were differentially expressed in DCM patients with VT but not without VT. Differentially expressed genes were evaluated using pathway analysis, and pathways of interest were investigated by qRT-PCR validation, Western blot, and microscopy. There were 590 genes differentially expressed in DCM patients with VT that are not differentially expressed in patients without VT. These genes were enriched for genes in the TGFß1 and TP53 signaling pathways. Increased fibrosis and activated TP53 signaling was demonstrated in heart tissue of DCM patients with VT.

CONCLUSIONS

Our study supports that distinct biological mechanisms distinguish ventricular arrhythmia in DCM patients.

The Role of Bone Morphogenetic Protein 7 (BMP-7) in Inflammation in Heart Diseases

Bone morphogenetic protein-7 is (BMP-7) is a potent anti-inflammatory growth factor belonging to the Transforming Growth Factor Beta (TGF-β) superfamily. It plays an important role in various biological processes, including embryogenesis, hematopoiesis, neurogenesis and skeletal morphogenesis. BMP-7 stimulates the target cells by binding to specific membrane-bound receptor BMPR 2 and transduces signals through mothers against decapentaplegic (Smads) and mitogen activated protein kinase (MAPK) pathways. To date, rhBMP-7 has been used clinically to induce the differentiation of mesenchymal stem cells bordering the bone fracture site into chondrocytes, osteoclasts, the formation of new bone via calcium deposition and to stimulate the repair of bone fracture. However, its use in cardiovascular diseases, such as atherosclerosis, myocardial infarction, and diabetic cardiomyopathy is currently being explored. More importantly, these cardiovascular diseases are associated with inflammation and infiltrated monocytes where BMP-7 has been demonstrated to be a key player in the differentiation of pro-inflammatory monocytes, or M1 macrophages, into anti-inflammatory M2 macrophages, which reduces developed cardiac dysfunction. Therefore, this review focuses on the molecular mechanisms of BMP-7 treatment in cardiovascular disease and its role as an anti-fibrotic, anti-apoptotic and anti-inflammatory growth factor, which emphasizes its potential therapeutic significance in heart diseases.

Radiotherapy-induced heart disease: a review of the literature

Radiotherapy as one of the four pillars of cancer therapy plays a critical role in the multimodal treatment of thoracic cancers. Due to significant improvements in overall cancer survival, radiotherapy-induced heart disease (RIHD) has become an increasingly recognized adverse reaction which contributes to major radiation-associated toxicities including non-malignant death. This is especially relevant for patients suffering from diseases with excellent prognosis such as breast cancer or Hodgkin’s lymphoma, since RIHD may occur decades after radiotherapy. Preclinical studies have enriched our knowledge of many potential mechanisms by which thoracic radiotherapy induces heart injury. Epidemiological findings in humans reveal that irradiation might increase the risk of cardiac disease at even lower doses than previously assumed. Recent preclinical studies have identified non-invasive methods for evaluation of RIHD. Furthermore, potential options preventing or at least attenuating RIHD have been developed. Ongoing research may enrich our limited knowledge about biological mechanisms of RIHD, identify non-invasive early detection biomarkers and investigate potential treatment options that might attenuate or prevent these unwanted side effects. Here, we present a comprehensive review about the published literature regarding clinical manifestation and pathological alterations in RIHD. Biological mechanisms and treatment options are outlined, and challenges in RIHD treatment are summarized.

Physiologic, Pathologic, and Therapeutic Paracrine Modulation of Cardiac Excitation-Contraction Coupling

Cardiac excitation-contraction coupling (ECC) is the orchestrated process of initial myocyte electrical excitation, which leads to calcium entry, intracellular trafficking, and subsequent sarcomere shortening and myofibrillar contraction. Neurohumoral β-adrenergic signaling is a well-established mediator of ECC; other signaling mechanisms, such as paracrine signaling, have also demonstrated significant impact on ECC but are less well understood. For example, resident heart endothelial cells are well-known physiological paracrine modulators of cardiac myocyte ECC mainly via NO and endothelin-1. Moreover, recent studies have demonstrated other resident noncardiomyocyte heart cells (eg, physiological fibroblasts and pathological myofibroblasts), and even experimental cardiotherapeutic cells (eg, mesenchymal stem cells) are also capable of altering cardiomyocyte ECC through paracrine mechanisms. In this review, we first focus on the paracrine-mediated effects of resident and therapeutic noncardiomyocytes on cardiomyocyte hypertrophy, electrophysiology, and calcium handling, each of which can modulate ECC, and then discuss the current knowledge about key paracrine factors and their underlying mechanisms of action. Next, we provide a case example demonstrating the promise of tissue-engineering approaches to study paracrine effects on tissue-level contractility. More specifically, we present new functional and molecular data on the effects of human adult cardiac fibroblast conditioned media on human engineered cardiac tissue contractility and ion channel gene expression that generally agrees with previous murine studies but also suggests possible species-specific differences. By contrast, paracrine secretions by human dermal fibroblasts had no discernible effect on human engineered cardiac tissue contractile function and gene expression. Finally, we discuss systems biology approaches to help identify key stem cell paracrine mediators of ECC and their associated mechanistic pathways. Such integration of tissue-engineering and systems biology methods shows promise to reveal novel insights into paracrine mediators of ECC and their underlying mechanisms of action, ultimately leading to improved cell-based therapies for patients with heart disease.