transforming-growth-factor-beta and Arrhythmias--Cardiac

Fibrotic diseases are a significant global burden for which there are limited treatment options. The effector cells of fibrosis are activated fibroblasts called myofibroblasts, a highly contractile cell type characterized by the appearance of α-smooth muscle actin stress fibers. The underlying mechanism behind myofibroblast differentiation and persistence has been under much investigation and is known to involve a complex signaling network involving transforming growth factor-β, endothelin-1, angiotensin II, CCN2 (connective tissue growth factor), and platelet-derived growth factor. This review addresses the contribution of these signaling molecules to cardiac fibrosis.

Topics: Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Animals; Anti-Inflammatory Agents; Arrhythmias, Cardiac; Atrophy; Cicatrix; Connective Tissue Growth Factor; Endothelin Receptor Antagonists; Endothelin-1; Fibrosis; Humans; Hypoxia; Models, Cardiovascular; Molecular Targeted Therapy; Myocardium; Myofibroblasts; Platelet-Derived Growth Factor; Pyridones; Rats; Signal Transduction; Transforming Growth Factor beta

The importance of fibrosis in organ pathology and dysfunction appears to be increasingly relevant to a variety of distinct diseases. In particular, a number of different cardiac pathologies seem to be caused by a common fibrotic process. Within the heart, this fibrosis is thought to be partially mediated by transforming growth factor-beta1 (TGF-beta1), a potent stimulator of collagen-producing cardiac fibroblasts. Previously, TGF-beta1 had been implicated solely as a modulator of the myocardial remodelling seen after infarction. However, recent studies indicate that dilated, ischaemic and hypertrophic cardiomyopathies are all associated with raised levels of TGF-beta1. In fact, the pathogenic effects of TGF-beta1 have now been suggested to play a major role in valvular disease and arrhythmia, particularly atrial fibrillation. Thus far, medical therapy targeting TGF-beta1 has shown promise in a multitude of heart diseases. These therapies provide great hope, not only for treatment of symptoms but also for prevention of cardiac pathology as well. As is stated in the introduction, most reviews have focused on the effects of cytokines in remodelling after myocardial infarction. This article attempts to underline the significance of TGF-beta1 not only in the post-ischaemic setting, but also in dilated and hypertrophic cardiomyopathies, valvular diseases and arrhythmias (focusing on atrial fibrillation). It also aims to show that TGF-beta1 is an appropriate target for therapy in a variety of cardiovascular diseases.

Topics: Arrhythmias, Cardiac; Cardiomyopathies; Fibrosis; Heart Diseases; Heart Valve Diseases; Humans; Matrix Metalloproteinases; Myocardium; Transforming Growth Factor beta; Transforming Growth Factor beta1

Arrhythmogenic cardiomyopathy (ACM) is characterized by progressive loss of cardiomyocytes with fibrofatty tissue replacement, systolic dysfunction, and life-threatening arrhythmias. A substantial proportion of ACM is caused by mutations in genes of the desmosomal cell-cell adhesion complex, but the underlying mechanisms are not well understood. In the current study, we investigated the relevance of defective desmosomal adhesion for ACM development and progression.. We mutated the binding site of DSG2 (desmoglein-2), a crucial desmosomal adhesion molecule in cardiomyocytes. This DSG2-W2A mutation abrogates the tryptophan swap, a central interaction mechanism of DSG2 on the basis of structural data. Impaired adhesive function of DSG2-W2A was confirmed by cell-cell dissociation assays and force spectroscopy measurements by atomic force microscopy. The DSG2-W2A knock-in mouse model was analyzed by echocardiography, ECG, and histologic and biomolecular techniques including RNA sequencing and transmission electron and superresolution microscopy. The results were compared with ACM patient samples, and their relevance was confirmed in vivo and in cardiac slice cultures by inhibitor studies applying the small molecule EMD527040 or an inhibitory integrin-αVβ6 antibody.. The DSG2-W2A mutation impaired binding on molecular level and compromised intercellular adhesive function. Mice bearing this mutation develop a severe cardiac phenotype recalling the characteristics of ACM, including cardiac fibrosis, impaired systolic function, and arrhythmia. A comparison of the transcriptome of mutant mice with ACM patient data suggested deregulated integrin-αVβ6 and subsequent transforming growth factor-β signaling as driver of cardiac fibrosis. Blocking integrin-αVβ6 led to reduced expression of profibrotic markers and reduced fibrosis formation in mutant animals in vivo.. We show that disruption of desmosomal adhesion is sufficient to induce a phenotype that fulfils the clinical criteria to establish the diagnosis of ACM, confirming the dysfunctional adhesion hypothesis. Deregulation of integrin-αVβ6 and transforming growth factor-β signaling was identified as a central step toward fibrosis. A pilot in vivo drug test revealed this pathway as a promising target to ameliorate fibrosis. This highlights the value of this model to discern mechanisms of cardiac fibrosis and to identify and test novel treatment options for ACM.

Topics: Animals; Arrhythmias, Cardiac; Arrhythmogenic Right Ventricular Dysplasia; Cardiomyopathies; Fibrosis; Integrins; Mice; Myocytes, Cardiac; Transforming Growth Factor beta; Transforming Growth Factors

Diabetes mellitus is a serious metabolic condition associated with a multitude of cardiovascular complications. Moreover, the prevalence of diabetes in heart failure populations is higher than that in control populations. However, the role of cardiomyocyte alterations in type 2 diabetes mellitus (T2DM) has not been well characterized and the underlying mechanisms remain elusive. In this study, two patients who were diagnosed as T2DM were recruited and patient-specific induced pluripotent stem cells (iPSCs) were generated from urine epithelial cells using nonintegrated Sendai virus. The iPSC lines derived from five healthy subjects were used as controls. All iPSCs were differentiated into cardiomyocytes (iPSC-CMs) using the monolayer-based differentiation protocol. T2DM iPSC-CMs exhibited various disease phenotypes, including cellular hypertrophy and lipid accumulation. Moreover, T2DM iPSC-CMs exhibited higher susceptibility to high-glucose/high-lipid challenge than control iPSC-CMs, manifesting an increase in apoptosis. RNA-Sequencing analysis revealed a differential transcriptome profile and abnormal activation of TGFβ signaling pathway in T2DM iPSC-CMs. We went on to show that inhibition of TGFβ significantly rescued the hypertrophic phenotype in T2DM iPSC-CMs. In conclusion, we demonstrate that the iPSC-CM model is able to recapitulate cellular phenotype of T2DM. Our results indicate that iPSC-CMs can therefore serve as a suitable model for investigating molecular mechanisms underlying diabetic cardiomyopathies and for screening therapeutic drugs.

Topics: Apoptosis; Arrhythmias, Cardiac; Biomarkers; Case-Control Studies; Cell Differentiation; Cells, Cultured; Diabetes Mellitus, Type 2; Epithelial Cells; Glucose; Humans; Immunophenotyping; Induced Pluripotent Stem Cells; Lipid Metabolism; Myocytes, Cardiac; Signal Transduction; Transcriptome; Transforming Growth Factor beta

Topics: Animals; Arrhythmias, Cardiac; Calcium Signaling; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Disease Models, Animal; Eplerenone; Female; Fibrosis; Male; Mice; Mice, Inbred C57BL; Mineralocorticoid Receptor Antagonists; Receptors, Mineralocorticoid; Signal Transduction; Smad3 Protein; Transforming Growth Factor beta

Topics: Arrhythmias, Cardiac; Connective Tissue Growth Factor; Fibrosis; Heart Failure; Humans; Myocytes, Cardiac; Transforming Growth Factor beta

Loss-of-function mutations in SCN5A, the gene encoding NaV1.5 channel, have been associated with inherited progressive cardiac conduction disease (PCCD). We have proposed that Scn5a heterozygous knock-out (Scn5a+/-) mice, which are characterized by ventricular fibrotic remodelling with ageing, represent a model for PCCD. Our objectives were to identify the molecular pathway involved in fibrosis development and prevent its activation.. Our study shows that myocardial interstitial fibrosis occurred in Scn5a+/- mice only after 45 weeks of age. Fibrosis was triggered by transforming growth factor β (TGF-β) pathway activation. Younger Scn5a+/- mice were characterized by a higher connexin 43 expression than wild-type (WT) mice. After the age of 45 weeks, connexin 43 expression decreased in both WT and Scn5a+/- mice, although the decrease was larger in Scn5a+/- mice. Chronic inhibition of cardiac sodium current with flecainide (50 mg/kg/day p.o) in WT mice from the age of 6 weeks to the age of 60 weeks did not lead to TGF-β pathway activation and fibrosis. Chronic inhibition of TGF-β receptors with GW788388 (5 mg/kg/day p.o.) in Scn5a+/- mice from the age of 45 weeks to the age of 60 weeks prevented the occurrence of fibrosis. However, current data could not detect reduction in QRS duration with GW788388.. Myocardial fibrosis secondary to a loss of NaV1.5 is triggered by TGF-β signalling pathway. Those events are more likely secondary to the decreased NaV1.5 sarcolemmal expression rather than the decreased Na+ current per se. TGF-β receptor inhibition prevents age-dependent development of ventricular fibrosis in Scn5a+/- mouse.

Topics: Age Factors; Animals; Anti-Arrhythmia Agents; Arrhythmias, Cardiac; Benzamides; Cardiomyopathies; Connexin 43; Disease Models, Animal; Female; Fibrosis; Flecainide; Genetic Predisposition to Disease; Heart Conduction System; Heart Rate; Heart Ventricles; Heterozygote; Kinetics; Male; Membrane Potentials; Mice, 129 Strain; Mice, Knockout; NAV1.5 Voltage-Gated Sodium Channel; Phenotype; Pyrazoles; Receptors, Transforming Growth Factor beta; Signal Transduction; Transforming Growth Factor beta; Ventricular Remodeling; Voltage-Gated Sodium Channel Blockers

Patients with CKD have an increased risk of cardiovascular mortality from arrhythmias and sudden cardiac death. We used a rat model of CKD (Cy/+) to study potential mechanisms of increased ventricular arrhythmias. Rats with CKD showed normal ejection fraction but hypertrophic myocardium. Premature ventricular complexes occurred more frequently in CKD rats than normal rats (42% versus 11%, P=0.18). By optical mapping techniques, action potential duration (APD) at 80% of repolarization was longer in CKD rats (78±4ms) than normal rats (63±3 ms, P<0.05) at a 200-ms pacing cycle length. Calcium transient (CaT) duration was comparable. Pacing cycle length thresholds to induce CaT alternans or APD alternans were longer in CKD rats than normal rats (100±7 versus 80±3 ms and 93±6 versus 76±4 ms for CaT and APD alternans, respectively, P<0.05), suggesting increased vulnerability to ventricular arrhythmia. Ventricular fibrillation was induced in 9 of 12 CKD rats and 2 of 9 normal rats (P<0.05); early afterdepolarization occurred in two CKD rats but not normal rats. The mRNA levels of TGF-β, microRNA-21, and sodium calcium-exchanger type 1 were upregulated, whereas the levels of microRNA-29, L-type calcium channel, sarco/endoplasmic reticulum calcium-ATPase type 2a, Kv1.4, and Kv4.3 were downregulated in CKD rats. Cardiac fibrosis was mild and not different between groups. We conclude that cardiac ion channel and calcium handling are abnormal in CKD rats, leading to increased vulnerability to early afterdepolarization, triggered activity, and ventricular arrhythmias.

Topics: Action Potentials; Animals; Arrhythmias, Cardiac; Calcium; Calcium Signaling; Disease Models, Animal; Echocardiography; Electrophysiology; Fibrosis; Gene Expression Regulation; Heart Rate; Male; MicroRNAs; Myocardium; Rats; Renal Insufficiency, Chronic; RNA, Messenger; Transforming Growth Factor beta; Ventricular Fibrillation

This study sought to assess whether renal sympathetic denervation (RSD) could suppress ventricular substrate remodelling and attenuate heart failure (HF) progression.. Nineteen dogs were randomised into three groups - seven sham-operated controls, six with right ventricular pacing to induce HF, and six with RSD followed eight weeks later by pacing induction of HF. Haemodynamic variables were monitored at baseline and after HF. Levels of ventricular interstitial fibrosis, BNP, Ang II, aldosterone and TGF-β were measured. All the dogs in the HF and HF﹢RSD groups showed increased left and right ventricular diastolic dimensions, but the dogs in the HF﹢RSD group had a higher left ventricular ejection fraction (LVEF) than the HF dogs (0.42±0.05 vs. 0.35±0.04, p<0.01). Compared with the dogs with HF alone, the HF+RSD dogs had lower left ventricular end-diastolic pressure (LVEDP) (3.3±1.6 vs. 25±3.7 mmHg, p<0.01) and less fibrous tissue. The levels of BNP, Ang II, aldosterone and TGF-β expression in ventricular tissue were higher in the HF dogs than in the sham-operated and HF﹢RSD dogs.. RSD suppressed ventricular substrate remodelling induced by long-term rapid ventricular pacing.

Topics: Aldosterone; Angiotensin II; Animals; Arrhythmias, Cardiac; Cardiac Pacing, Artificial; Catheter Ablation; Disease Models, Animal; Disease Progression; Dogs; Female; Fibrosis; Heart Failure; Heart Ventricles; Kidney; Male; Natriuretic Peptide, Brain; Sympathectomy; Time Factors; Transforming Growth Factor beta; Ventricular Function, Left; Ventricular Pressure; Ventricular Remodeling

The pacemaking activity of specialized tissues in the heart and gut results in lifelong rhythmic contractions. Here we describe a new syndrome characterized by Chronic Atrial and Intestinal Dysrhythmia, termed CAID syndrome, in 16 French Canadians and 1 Swede. We show that a single shared homozygous founder mutation in SGOL1, a component of the cohesin complex, causes CAID syndrome. Cultured dermal fibroblasts from affected individuals showed accelerated cell cycle progression, a higher rate of senescence and enhanced activation of TGF-β signaling. Karyotypes showed the typical railroad appearance of a centromeric cohesion defect. Tissues derived from affected individuals displayed pathological changes in both the enteric nervous system and smooth muscle. Morpholino-induced knockdown of sgol1 in zebrafish recapitulated the abnormalities seen in humans with CAID syndrome. Our findings identify CAID syndrome as a novel generalized dysrhythmia, suggesting a new role for SGOL1 and the cohesin complex in mediating the integrity of human cardiac and gut rhythm.

Topics: Abnormalities, Multiple; Animals; Arrhythmias, Cardiac; Cell Cycle; Cell Cycle Proteins; Chromosomal Proteins, Non-Histone; Cohesins; Enteric Nervous System; Fibroblasts; Founder Effect; Gastrointestinal Tract; Gene Knockdown Techniques; Humans; Intestinal Diseases; Karyotyping; Muscle Contraction; Muscle, Smooth, Vascular; Mutation; Quebec; Signal Transduction; Syndrome; Transforming Growth Factor beta; Zebrafish

Although tumor necrosis factor-α (TNF-α) levels are increased in patients with atrial fibrillation (AF), its role in the pathogenesis of AF is unclear. We investigated whether direct delivery of TNF-α could induce atrial fibrosis.. TNF-α (4 μg/kg) was injected into the tail vein of 20 male Swiss albino mice (TNF group) and saline into 20 control mice (CON group). The dose was carefully chosen to avoid any significant decrease in left ventricular (LV) function. Animals were killed after 16 weeks and their atria examined for fibrosis. We found increased atrial fibrosis in the TNF group compared with the CON group [372.8±21.5 arbitrary units (a.u.) vs. 56.9±6.5 a.u., respectively, mean±SEM; P<0.0001] and decreased connexin-40 immunofluorescence [7.5±0.4 a.u vs. 40.4±1.9 a.u, respectively; P<0.0001]. Transforming growth factor-β [TGF-β: 95.6±1.8 a.u vs. 29.4±5.8 a.u; P<0.001], α-smooth muscle actin (α-SMA: 97.9±13.0 a.u vs. 50.1±18.5 a.u; P<0.05] and matrix metalloproteinase 2 (MMP-2)/GAPDH levels [157.3±26.4 a.u vs. 105.8±13.3 a.u; P<0.05] were also increased in the TNF group.. TNF-α is involved in the pathogenesis of atrial fibrosis and altered connexin-40 expression in mice through the TGF-β signaling pathway, activation of myofibroblasts and increased secretion of MMPs. Collectively, these changes may contribute to the arrhythmogenic substrate and development of AF. 

Topics: Actins; Animals; Arrhythmias, Cardiac; Atrial Function; Connexin 43; Connexins; Down-Regulation; Fibrosis; Fluorescent Antibody Technique; Gap Junction alpha-5 Protein; Heart Atria; Injections, Intravenous; Male; Matrix Metalloproteinase 2; Mice; Myofibroblasts; Signal Transduction; Smad3 Protein; Time Factors; Transforming Growth Factor beta; Tumor Necrosis Factor-alpha

Transforming growth factor-beta (TGF-beta) family members, including TGF-betas, activins, and bone morphogenetic proteins, exert diverse biological activities in cell proliferation, differentiation, apoptosis, embryonic development, and many other processes. These effects are largely mediated by Smad proteins. Smad7 is a negative regulator for the signaling of TGF-beta family members. Dysregulation of Smad7 is associated with pathogenesis of a variety of human diseases. However, the in vivo physiological roles of Smad7 have not been elucidated due to the lack of a mouse model with significant loss of Smad7 function. Here we report generation and initial characterization of Smad7 mutant mice with targeted deletion of the indispensable MH2 domain. The majority of Smad7 mutant mice died in utero due to multiple defects in cardiovascular development, including ventricular septal defect and non-compaction, as well as outflow tract malformation. The surviving adult Smad7 mutant mice had impaired cardiac functions and severe arrhythmia. Further analyses suggest that Smad2/3 phosphorylation was elevated in atrioventricular cushion in the heart of Smad7 mutant mice, accompanied by increased apoptosis in this region. Taken together, these observations pinpoint an important role of Smad7 in the development and function of the mouse heart in vivo.

Topics: Amino Acid Sequence; Animals; Arrhythmias, Cardiac; Heart; Heart Defects, Congenital; Humans; Mice; Mice, Mutant Strains; Phosphorylation; Protein Structure, Tertiary; Sequence Deletion; Smad2 Protein; Smad3 Protein; Smad7 Protein; Transforming Growth Factor beta

Insulin-like growth factor-1 (IGF-1), transforming growth factor beta (TGFbeta) and cyclins are thought to play a role in myocardial hypertrophic response to insults. We investigated these signaling pathways in canine models of ischemic or overpacing-induced cardiomyopathy.. Echocardiographic recordings and myocardial sampling for measurements of gene expressions of IGF-1, its receptor (IGF-1R), TGFbeta and of cyclins A, B, D1, D2, D3 and E, were obtained in 8 dogs with a healed myocardial infarction, 8 dogs after 7 weeks of overpacing and in 7 healthy control dogs.. Ischemic cardiomyopathy was characterized by moderate left ventricular systolic dysfunction and eccentric hypertrophy, with increased expressions of IGF-1, IGF-1R and cyclins B, D1, D3 and E. Tachycardiomyopathy was characterized by severe left ventricular systolic dysfunction and dilation with no identifiable hypertrophic response. In the latter model, only IGF-1 was overexpressed while IGF-1R, cyclins B, D1, D3 and E stayed unchanged as compared to controls. The expressions of TGFbeta, cyclins A and D2 were comparable in the 3 groups. The expression of IGF-1R was correlated with the thickness of the interventricular septum, in systole and diastole, and to cyclins B, D1, D3 and E expression.. These results agree with the notion that IGF-1/IGF-1R and cyclins are involved in the hypertrophic response observed in cardiomyopathies.

Topics: Animals; Arrhythmias, Cardiac; Cardiac Pacing, Artificial; Cardiomyopathy, Dilated; Cardiomyopathy, Hypertrophic; Cyclins; Disease Models, Animal; Dogs; Echocardiography; Gene Expression Regulation; Insulin-Like Growth Factor I; Myocardial Ischemia; Myocardium; Polymerase Chain Reaction; Receptor, IGF Type 1; Transforming Growth Factor beta; Ventricular Dysfunction, Left

Atrioventricular (AV) nodal ablation for management of atrial fibrillation (AF) is irreversible and requires permanent pacemaker implantation. We hypothesized that as an alternative, implantation of autologous fibroblasts in the perinodal region would focally modify AV nodal conduction and that this modulation would be enhanced by pretreatment with transforming growth factor-beta1 (TGF-beta1), a stimulant of fibroblasts.. Skin biopsies were taken from 12 mongrel dogs, and derived fibroblasts were dissociated and grown in culture for 2 weeks. Multiple injections (0.25 mL) were made through an 8F NOGA catheter along the fast/slow AV nodal pathways as guided by an electroanatomic mapping system. Seven dogs received fibroblasts alone (1x10(6) cells/mL), 7 dogs received TGF-beta1 (5 microg), 4 dogs received fibroblasts and TGF-beta1 (1x10(6) cells/mL+5 microg), and 4 dogs received saline only. AV node function was assessed at baseline and after 4 weeks. Saline (80 mL) with assigned therapy (0.25 mL per injection) was injected into the peri-AV nodal region in each dog. At baseline, the AH interval (66+/-3 ms) and the average RR interval (331+/-17 ms) in pacing-induced AF were similar in each cohort. The increase in AH interval in normal sinus rhythm was longer after fibroblast (23+/-4 versus 5+/-5 ms; P=0.05) and fibroblast plus TGF-beta1 (50+/-5 versus 5+/-5 ms; P<0.001) injections than with saline alone, with similar findings during high right atrium and distal coronary sinus pacing. The AH interval was not significantly increased after TGF-beta1 injections. The AH interval was significantly longer after fibroblast plus TGF-beta1 injections than with either therapy (TGF-beta1 or fibroblasts) alone. The RR interval during AF was increased in dogs that received fibroblasts alone (110+/-36 versus -41+/-34 ms) and to a greater extent with the addition of TGF-beta1 (294+/-108 versus -41+/-34 ms). No AV block was seen in any cohort at 4 weeks. Labeled fibroblasts that expressed vimentin were identified in all dogs that received cell injections at 4 weeks.. AV nodal modification can be achieved with injected fibroblasts without the creation of AV block. The effect on AV node conduction is substantially enhanced by pretreatment of fibroblasts with TGF-beta1. These data have therapeutic potential for the management of rapid ventricular rate during AF without pacemaker implantation.

Topics: Animals; Arrhythmias, Cardiac; Atrioventricular Node; Body Surface Potential Mapping; Cardiac Pacing, Artificial; Cell Transplantation; Dogs; Fibroblasts; Heart Conduction System; Male; Transforming Growth Factor beta; Transforming Growth Factor beta1; Transplantation, Autologous

Topics: Angiotensin II; Animals; Arrhythmias, Cardiac; Atrial Fibrillation; Dogs; Fibrosis; Heart Atria; Heart Failure; Humans; Mice; Mice, Transgenic; Models, Animal; Myocardium; Transforming Growth Factor beta; Transforming Growth Factor beta1; Ventricular Remodeling