Cardiac Extracellular Matrix Remodeling Research Articles

Effect of clenbuterol administration on the healthy murine heart

Clenbuterol has recently been shown to reverse pathologic cardiac remodeling during left ventricular assist device (LVAD) support, leading to restored ventricular function and explantation of LVAD devices. However, others have not been able to support these observations. Our hypothesis is that the beta(2)-adrenergic activity of clenbuterol induces cardiac extracellular matrix (ECM) remodeling, resulting in increased interstitial fibrillar collagen content and altered diastolic function that may account for these conflicting reports. The intent of this study is to characterize the effect of clenbuterol on healthy murine hearts with transthoracic echo and histology. C57BL/6 female mice were administered 2.4 microg/kg/day of clenbuterol in the drinking water for 7 days and analysis conducted on day 8-24 hours after the last dose of clenbuterol. Histological analysis demonstrated an increase in left ventricular ECM collagen content in a control group compared with the clenbuterol group (density 0.32 +/- 0.16 compared to 2.01 +/- 0.30 RD/mm(2)). The ventricular fibrosis was supported by altered diastolic function measured by transthoracic echo where there was a significant increase in isovolumic relaxation time, and left atrial dimension and a decrease in left ventricular free wall tissue Doppler ratios. Our study showed no significant differences in left ventricular ejection fraction, cardiac output, or heart rate between the clenbuterol and control groups. These data suggest that the beta-2 adrenergic activity of clenbuterol increases ECM fibrillar collagen concentrations in normal hearts, resulting in altered diastolic function.

Biglycan Is Required for Adaptive Remodeling After Myocardial Infarction

After myocardial infarction (MI), extensive remodeling of extracellular matrix contributes to scar formation and preservation of hemodynamic function. On the other hand, adverse and excessive extracellular matrix remodeling leads to fibrosis and impaired function. The present study investigates the role of the small leucine-rich proteoglycan biglycan during cardiac extracellular matrix remodeling and cardiac hemodynamics after MI. Experimental MI was induced in wild-type (WT) and bgn(-/0) mice by permanent ligation of the left anterior descending coronary artery. Biglycan expression was strongly increased at 3, 7, and 14 days after MI in WT mice. bgn(-/0) mice showed increased mortality rates after MI as a result of frequent left ventricular (LV) ruptures. Furthermore, tensile strength of the LV derived from bgn(-/0) mice 21 days after MI was reduced as measured ex vivo. Collagen matrix organization was severely impaired in bgn(-/0) mice, as shown by birefringence analysis of Sirius red staining and electron microscopy of collagen fibrils. At 21 days after MI, LV hemodynamic parameters were assessed by pressure-volume measurements in vivo to obtain LV end-diastolic pressure, end-diastolic volume, and end-systolic volume. bgn(-/0) mice were characterized by aggravated LV dilation evidenced by increased LV end-diastolic volume (bgn(-/0), 111+/-4.2 microL versus WT, 96+/-4.4 microL; P<0.05) and LV end-diastolic pressure (bgn(-/0), 24+/-2.7 versus WT, 18+/-1.8 mm Hg; P<0.05) and severely impaired LV function (EF, bgn(-/0), 12+/-2% versus WT, 21+/-4%; P<0.05) 21 days after MI. Biglycan is required for stable collagen matrix formation of infarct scars and for preservation of cardiac hemodynamic function.

T-Lymphocytes Regulate Cardiac Extracellular Matrix Collagen Crosslinking

Background: The composition, orientation, and abundance of cardiac extracellular matrix (ECM) proteins have profound consequences on the myocardial structure and function. Recently it has become apparent that the adaptive immune system plays a critical role in cardiac ECM remodeling. Objective: The hypothesis of this report is that T-lymphocyte affects fibrillar collagen crosslinking through modulation of the enzymatic activities of lysyl oxidase (LOX and LOXL-3) released by the cardiac fibroblast.

Impact of Pycnogenol® on cardiac extracellular matrix remodeling induced by l-NAME administration to old mice

Cardiac remodeling is a determinant of the clinical progression of heart failure and now slowing or reversing remodeling is considered as a potential therapeutic target in heart failure. Pycnogenol has been reported to mediate a number of beneficial effects in the cardiovascular system but its effects on hemodynamic and functional cardiovascular changes following cardiac remodeling have not been elucidated. Therefore, we investigated the influence of Pycnogenol supplementation (30 mg/kg) on left ventricular function and myocardial extracellular matrix composition in old C57BL/6N mice following induction of cardiac remodeling by chronic nitric oxide synthase blockade by NG-nitro-L-arginine methyl ester (L-NAME) administration. L-NAME-treated mice demonstrated dilated cardiomyopathy at compensated state, associated with a significant increase of pro-matrix metalloproteinase (MMP)-9 gene expression and activity, a marked decrease in pro-collagen IIIalpha1 gene expression, and a subsequent reduction in cardiac total and cross-linked collagen content. Upon supplementation with Pycnogenol in L-NAME-exposed mice, cardiac gene expression patterns for pro-MMP-2, -9, and -13, and MMP-9 activity were significantly decreased, associated with a significant increase in cardiac tissue inhibitor of metalloproteinase (TIMP)-4 expression. These findings were coincided with a marked increase in myocardial total and cross-linked collagen content, compared with L-NAME-only-treated mice. Moreover, Pycnogenol treatment was associated with reversal of L-NAME-induced alternations in hemodynamic parameters. These data indicate that Pycnogenol can prevent adverse myocardial remodeling induced by L-NAME, through modulating TIMP and MMPs gene expression, MMPs activity, and further reduction in myocardial collagen degradation rate.

Abstract 589: Activation of Toll-like Receptor Induces Cardiac Remodeling

Introduction: Diastolic heart failure, due to increased ventricular stiffness, is brought about by extracellular matrix (ECM) remodeling. We have previously shown that T-lymphocyte function directly affects cardiac fibroblast function and thereby the ECM composition and diastolic function. Oligodeoxynucleotides (ODN) that selectively stimulate the Toll-like receptor-9 (TLR9) receptor on dendritic cells (DC), induce TH1 immune response. Hypothesis: Selective stimulation of the DC TLR 9 receptor with ODN CPG1668 activates TH1 lymphocytes resulting in ECM remodeling and diastolic dysfunction. Methods: Weight matched C57BL/6J female mice were treated either with PBS (n=8) or with CPG1668 (n=8) at a dose of 50 μg/mouse/week (i.p.) for 4 weeks. After 6 weeks, left ventricular mechanics were determined with pressure-volume loop analysis, ECHO, and ventricular tissue harvested for gene expression, collagen content and crosslinking, and the collagen crosslinking enzymatic activity of lysyl oxidase (LOX). Splenic lymphocytes were harvested for the cytokine determination. Results: CPG1668 administration increased the TH1 cytokine, IFN-γ, from 429±21 to 954±21 (ng/10 6 T-cells), while TH2 cytokine, IL-4, decreased from 614±79 to 51±19 (pg/10 6 T-cells). CPG1668 significantly decreased the end-diastolic volume from 18±1 to 14±1μL (P=0.02), and cardiac output from 6.7±0.6 to 4.9±0.6 mL/min (P=0.05) with no change of ejection fraction 71±3 to 73±4 compared with controls. An increase of ventricular stiffness (β), from 0.16±0.01 to 0.23±0.01 mmHg/μL (P=0.0007), was supported by a decreased E deceleration slope of −8.8±0.6 to −4.1±0.4 (P&lt;0.0001). CPG increased total cardiac collagen two-fold (P=0.0004) and collagen crosslinking by 3-fold (P=0.0007) compared with controls. Correspondingly, CPG administration increased cardiac LOX enzymatic activity by 61% (P=0.02). Real time PCR showed that LOXL3 gene expression increased 9.1-fold (P&lt;0.0001) as well as LOX 1.7-fold (P=0.05) when comparing CPG with controls. Conclusions: This study demonstrates that stimulation of the TH1 lymphocytes via DC TLR 9 receptor induces cardiac ECM remodeling and diastolic dysfunction associated with LOX induced collagen crosslinking.

Role of T Lymphocytes in Hypertension-Induced Cardiac Extracellular Matrix Remodeling

Cardiac remodeling in response to pressure overload involves reorganization of the myocytes and extracellular matrix (ECM). Neurohormonal pathways have been described as effector pathways in left ventricular ECM reorganization in response to pressure overload; we now are assessing the role of the T lymphocyte in this process. Mice with defined differences in T-lymphocyte function (C57BL/6 SCID, C57BL/6 WT, and BALB/c) were treated with 50 mg/L of N(G)-nitro-l-arginine methyl ester in their drinking water for 30 days. The immune function of C57BL/6 WT mice was T-helper type 1 (TH1), BALB/c was TH2, and C57BL/6 SCID was null. The arterial blood pressure increased by 30% in all of the strains of mice. However, ventricular stiffness significantly decreased in the C57 SCID, significantly increased in the BALB/c, and did not change in the C57 WT. The characterization of matrix metalloproteinase induction and activation on day 30 was associated with T-lymphocyte function. The total cardiac fibrillar collagen, percentage of fibrillar collagen cross-linking, and the activity of the cross-linking enzyme lysyl oxidase-like-3 (LOXL-3) significantly decreased in the C57 SCID, significantly increased in the BALB/c, and did not change in the C57 WT. This study revealed that the LOXL-3 pathway, namely, gene expression, enzymatic activities, and LOXL-3-mediated collagen cross-linking, was associated with ventricular stiffness and incongruence with lymphocyte function. These data support the concept that the T lymphocytes may play a fundamental regulatory role in cardiac ECM composition through modulation of collagen synthesis, degradation, and cross-linking.

Impact of T Lymphocytes on Cardiac Remodeling in Hypertension

In their intriguing article appearing in this issue of Hypertension , Yu et al1 provide evidence for a role of T lymphocytes in modulating cardiac matrix remodeling resulting from hypertension. The investigators compared the impact of comparable N G-nitro-l-arginine methyl ester (l-NAME)-induced hypertension on cardiac function and matrix composition among 3 strains of mice with widely different T-lymphocyte profiles. They found increased ventricular stiffness, accompanied by enhanced collagen deposition and cross-linking in the strain of mice that were Th2 dominant (BALB/c). In contrast, in mice that were T- (and B-) lymphocyte deficient (C57BL/6 SCID), hypertension resulted in a diminution of collagen content and cross-linking that was generally associated with heart dilation. No changes in ventricular stiffness or collagen were observed in mice that were Th1 dominant (C57BL/6 WT). Because these different responses of the heart to hypertension were observed under pre-existing dissimilar and extreme immune backgrounds, an obvious question is what impact, if any, T lymphocytes have on hypertension-associated cardiac remodeling in more common scenarios. Will it turn out that the well-established neurohormonal input into cardiac remodeling is actually an immunoneurohormal system or only that the neurohormonal component of remodeling is susceptible to modulation by extreme immune conditions? Other than this broad question, several specific questions come to mind from the work of Yu et al.1 First, how relevant is the use of l-NAME to induce hypertension and cardiac remodeling? Chronic pressure overload of the heart in animal models typically induces changes in the heart that include both increased extracellular matrix deposition and so-called compensatory left ventricular hypertrophy because of enlargement of individual …

Role of T-Lymphocytes in Wall Stress Induced Cardiac Extracellular Matrix Remodeling

Role of T-Lymphocytes in Wall Stress Induced Cardiac Extracellular Matrix Remodeling

Effects of cytokine treatment on angiotensin II type 1A receptor transcription and splicing in rat cardiac fibroblasts

Angiotensin II (ANG II) plays important roles in cardiac extracellular matrix remodeling via its type 1A (AT(1A)) receptor. The cytokines tumor necrosis factor-alpha and interleukin-1beta (IL-1beta) were shown previously to upregulate AT(1A) receptor mRNA and protein, thereby increasing the profibrotic response to ANG II in cardiac fibroblasts. The present experiments implicate increased nuclear factor-kappaB (NF-kappaB)-dependent transcription and also, to a lesser extent, altered mRNA splicing in the mechanism of receptor upregulation. Cytokine stimulation was found to increase AT(1A) heterogeneous nuclear RNA levels, which strongly suggests that mRNA upregulation occurs transcriptionally. The transcription factor NF-kappaB was previously deemed necessary for cytokine-induced AT(1A) receptor mRNA upregulation. Computer analysis of upstream DNA sequences revealed putative NF-kappaB elements at -365 and -2540 bp. Both isolated elements were shown to bind NF-kappaB (using gel-shift assays) and to transactivate a minimal promoter (using reporter assays), although the element at -365 bp appeared stronger. Three splice variants of AT(1A) receptor mRNA that have different 5' untranslated regions were detected in rat tissues, namely, exons 1-2-3 (predominant), 1-2-3+6, and 1-3. Cytokine treatment of fibroblasts upregulated all splice variants, but exon 1-3 increased more than the others. This differential upregulation, albeit of modest magnitude, was statistically significant with IL-1beta treatment. Exon 2 contains an inhibitory minicistron and a predicted inhibitory hairpin structure. Luciferase reporter assays indicated that each splice variant translates at a different efficiency, with exon 1-2-3+6 (both minicistron and hairpin) < exon 1-2-3 (minicistron only) < exon 1-3 (neither minicistron or hairpin). These results provide evidence that cytokines increase AT(1) protein levels by altering both transcription and splicing.

Exposure of cardiac fibroblasts to the herbicide nitrofen causes altered interactions with the extracellular matrix.

A large proportion of congenital heart defects result from dysmorphogenesis of valvuloseptal precursors, the endocardial cushions. Intrinsic to formation and maturation of these tissues are developmental changes in cell-cell and cell-extracellular matrix interactions. Interactions between cells and the extracellular matrix play critical roles in modulating cellular processes including proliferation, migration, differentiation and even survival. While significant progress is being made in the elucidation of the cellular events involved in valvuloseptal development, little is known regarding how environmental factors may affect this process. Embryonic exposure to the herbicide nitrofen has been shown to result in congenital heart defects associated with altered endocardial cushion formation or maturation. The present studies were performed to begin to address the cellular mechanisms of these nitrofen-induced effects. Heart fibroblasts were isolated and treated with varying doses of nitrofen in vitro. Experiments were performed to determine the effects of this herbicide on important cellular processes including migration, proliferation and apoptosis. These studies illustrated a dose-dependent decrease in collagen gel contraction and proliferation in response to nitrofen. Assays were also performed to determine the effects of nitrofen on fibroblast gene expression. Increased expression of collagen type I and specific integrins were seen following nitrofen exposure. These studies illustrate that nitrofen has direct effects on cardiac fibroblast proliferation and extracellular matrix remodeling, cellular events important in valvuloseptal development.

Cardiac rupture complicating myocardial infarction

Rupture of the ventricular free wall is a leading cause of death in patients with acute myocardial infarction (MI). There are a number of risk indicators that are associated with cardiac rupture, such as female gender, old age, hypertension, and first MI. Typical symptoms of cardiac rupture are recurrent or persistent chest pain, syncope, and distension of jugular veins. Electrocardiographic signs may include sinus tachycardia, new Q-waves in 2 or more leads, persistent or recurrent ST segment elevation, deviation of expected evolutionary T-wave pattern, and electromechanical dissociation in end-stage cases. Once patients at risk have been identified using clinical symptoms and electrocardiographic signs, a fast and sensitive diagnostic test to confirm cardiac rupture is transthoracic echocardiography (TTE). New insights in the etiology of subacute myocardial rupture suggests that defective cardiac remodeling may predispose the heart for rupture. The matrix metalloproteinase (MMP) system has been shown to play an important role in cardiac extracellular matrix (ECM) remodeling and cardiac rupture. Current therapy of cardiac rupture consists mainly of surgery, and conservative management with hemodynamic monitoring, prolonged bed rest, beta-blockers, and angiotensin-converting enzyme (ACE) inhibitors in selected cases.

Fourier transform infrared evaluation of microscopic scarring in the cardiomyopathic heart: Effect of chronic AT 1 suppression

Our primary aim was to investigate the use of Fourier transform infrared (FTIR) spectromicroscopy as an accurate assay of cardiac extracellular matrix remodeling. Abnormal rearrangement or remodeling of the cardiac extracellular matrix is known to contribute to cardiac dysfunction. The microscopic multifocal necrosis and scarring are modulated by chronic AT 1 receptor blockade in experimental cardiomyopathy; thus, we also wished to rationalize the spectromicroscopic differences among control, untreated cardiomyopathic (CMP), and losartan-treated cardiomyopathic (LOS) hearts according to the pathogenesis of experimental cardiomyopathy. Male UM-X7.1 cardiomyopathic Syrian hamsters at early and late (65 and 200 days) stages of cardiomyopathy were subjected to 4-week losartan (15 mg/kg/day continuous infusion) treatment. Focal collagen microdomain distribution was confirmed spectroscopically by observation of the collagen IR fingerprint in the 1000–1800 cm −1 region. Synchrotron FTIR spectromicroscopic map data were obtained from control (F1-β strain) hamsters, nontreated cardiomyopathic, and losartan-treated CMP animals and imaged with mapping software, according to intensity of collagen fingerprint. Compared to controls, untreated late-stage CMP myocardium was characterized by elevated levels of fibrillar collagens and this was partially normalized with a 4-week losartan treatment. FTIR spectromicroscopy revealed that elevated collagen expression in focal microdomains is present in late-stage cardiomyopathy, and 4-week AT 1 blockade is associated with attenuation of collagen absorption in these lesions.

Integration of concepts: Cardiac extracellular matrix remodeling after myocardial infarction

The cardiac extracellular matrix consists of a three-dimensional structural network of interstitial collagens to which other matrix components are attached. The main physiological functions of this network are to retain tissue integrity and cardiac pump function. Collagen deposition is controlled and can be modulated by hormonal factors, growth factors, cytokines, regulatory proteins and/or hemodynamic factors. Increased collagen deposition is a prerequisite to prevent dilatation of the infarcted area. Excessive accumulation of collagen leads to ventricular diastolic and systolic dysfunction and ultimately contributes to heart failure. An appropriate balance of extracellular matrix synthesis and degradation is required for normal morphogenesis and maintenance of tissue architecture. A disbalance in the extracellular matrix turnover either by decreased matrix synthesis and/or increased degradation leads to less than normal extracellular matrix in the myocardium which in its turn may lead to cardiac dilatation or even rupture. Extracellular matrix degrading enzymes expressed after myocardial infarction belong to the families of serine and matrix metalloproteinases (MMPs) and are secreted as latent proenzymes that have to be activated. It is crucial to keep the activity of these enzymes under tight control by either influencing the synthesis, activation or inhibition by tissue inhibitors of MMPs (TIMPs) or alpha2-macroglobulin. First studies using MMP inhibitors in experimental models of myocardial infarction seem to give attenuation of ventricular geometry but not always improvement of cardiac function. A central role in the activation of MMPs plays the plasminogen-plasmin system. Invasion of inflammatory cells and hitherto the rest of the wound healing cascade is inhibited in plasminogen or uPA deficient mice, most likely by the inhibition of MMP activity. Regulating the balance of extracellular matrix remodeling either by extracellular matrix synthesis or degradation might be one of the possible prevention mechanisms for heart failure. But also regeneration of the vascular and cardiomyocyte network might be potential new treatments for people with heart failure.

Remodelling of the cardiac extracellular matrix differs between volume and pressure overloaded ventricles and is specific for each heart valve lesion Cornelia Piper, Dieter Horstkotte, Daniel Akdemir, Joern Rudolf, Heinz-Peter Schultheiss, Matthias Pauschinger. Heart Center North Rhine-Westphalia, Bad Oeynhausen, Germany, University Hospital Benjamin Franklin, Berlin, Germany

Remodelling of the cardiac extracellular matrix differs between volume and pressure overloaded ventricles and is specific for each heart valve lesion Cornelia Piper, Dieter Horstkotte, Daniel Akdemir, Joern Rudolf, Heinz-Peter Schultheiss, Matthias Pauschinger. Heart Center North Rhine-Westphalia, Bad Oeynhausen, Germany, University Hospital Benjamin Franklin, Berlin, Germany

Remodelling of Cardiac Extracellular Matrix duringβ-adrenergic Stimulation: Upregulation of SPARC in the Myocardium of Adult Rats

Our objectives were (i) to evaluate the expression of several genes involved in the remodelling of cardiac extracellular matrix (ECM), with a special interest on SPARC (secreted protein acidic and rich in cysteine) a glycoprotein with anti-adhesive properties, and (ii) to characterise structural changes in the left (LV) and right (RV) ventricles of rats subjected to continuousβ-adrenergic stimulation. The rats were infused for 3 or 7 days with isoproterenol (ISO, 4 mg/kg/day) or vehicle. Hybridisation analysis was done for SPARC, atrial natriuretic peptide (ANP),α2(I) [COL-I] andα1(III) [COL-III] procollagens, TGF-β1and TGF-β3mRNA content. Interstitial and perivascular collagen deposition in both ventricles was measured after specific staining. The mean cross-sectional area of LV cardiomyocytes was evaluated by quantitative histomorphometry. ISO provoked an increase of LV mass, and a progressive enlargement of cardiomyocytes: their cross-sectional area raised from 205±8μm2in vehicle-treated animals to 247±4 and 296±9μm2after 3 or 7 days of ISO infusion, respectively (P<0.001). SPARC messenger abundance increased by more than 50% in LV and RV, a first evidence of its expression in the myocardium of adult rats. Transcripts of ANP, COL-III, TGF-β1and TGF-β3increased in both ventricles. COL-I transcript increased in LV (75 and 116% on days 3 and 7), but not in RV. In LV, collagen accumulated in the interstitium (2.69±0.20v9.23±0.50% of tissue area for vehicle and ISO 7 days groups,P<0.05) and around coronary arteries (1.04±0.11v4.47±0.48% of lumen area for vehicle and ISO 7 days,P<0.05). Cardiac fibrosis was less marked in RV. In conclusion, early expression of SPARC, an anti-adhesive protein, and preferential expression of COL-III, a distensible form of collagen, should increase ECM plasticity and facilitate ventricular remodelling

Ageing and the molecular and structural remodelling of cardiac extracellular matrix during β-adrenergic stimulation

Ageing and the molecular and structural remodelling of cardiac extracellular matrix during β-adrenergic stimulation

Ageing and the Molecular and Structural Remodelling of Cardiac Extracellular Matrix During β-Adrenergic Stimulation

Ageing and the Molecular and Structural Remodelling of Cardiac Extracellular Matrix During β-Adrenergic Stimulation