Progression Of Myocardial Fibrosis Research Articles

Abstract 9687: Aldosterone Enhances MR/NADPH Oxidase Physical Association, and Induces Cardiomyocyte Hypertrophy and Cardiac Fibroblast Proliferation via Amplification of IL-18 Signaling

Hyperaldosteronism is associated with inflammation, progressive myocardial hypertrophy, fibrosis and adverse remodeling. Since interleukin (IL)-18 is a hypertrophic and mitogenic inflammatory cytokine, we investigated whether Aldosterone (Aldo)-induced cardiomyocyte (CaM) hypertrophy and cardiac fibroblast (CF) proliferation and migration are IL-18 dependent. Aldo-induced hypertrophy of primary rat CaM was inhibited by the mineralocorticoid receptor (MR) antagonists spiranolactone, and eplerenone. Interestingly, knockdown of IL-18, or its neutralization with IL-18BP or polyclonal anti-rat IgG blunted Aldo’s growth effects. In CaM, Aldo induced IL-18 expression via DPI-inhibitable, Nox2- and Nox4-dependent ROS generation, and NF-κB and AP-1 activation. Knockdown of Nox2, Nox4, p65 or c-Jun inhibited IL-18 and IL-18Rα expression and CaM growth. Further, using GST pull-down assays and co-immunoprecipitation/immunoblotting, we demonstrate for the first time that MR physically associates with Nox2 and Nox4 both in vitro and in vivo under basal conditions, and Aldo enhances their interactions in vivo. In CF, Aldo stimulated DPI-inhibitable, Nox4-dependent ROS generation, IL-18, IL-18Rα, and MMP-9 induction, and IL-18-dependent migration and proliferation. In these cells, MR was found bound to Nox4. Continuous infusion of Aldo into rats resulted in myocardial hypertrophy and fibrosis, DPI-inhibitable ROS generation, MR binding to Nox2 and Nox4, and IL-18, IL-18Rα, and MMP-9 expression in the heart. Co-treatment with spironolactone blunted these effects. Notably, Aldo-induced myocardial hypertrophy and fibrosis were markedly attenuated in IL-18-null mice. These results demonstrate that Aldo amplifies IL-18 signaling in both cell types by inducing IL-18 and its receptor expression. Importantly, Aldo-induced cardiomyocyte hypertrophy and fibroblast proliferation are IL-18 dependent, and may involve the direct interaction of MR with NADPH oxidases. IL-18 is a potential therapeutic target in Aldo-induced myocardial hypertrophy, fibrosis and adverse remodeling.

Inflammatory Dilated Cardiomyopathy in Abcg5-deficient Mice

Dilated cardiomyopathy (DCM) in A/J mice homozygous for the spontaneous thrombocytopenia and cardiomyopathy (trac) mutation results from a single base pair change in the Abcg5 gene. A similar mutation in humans causes sitosterolemia with high plant sterol levels, hypercholesterolemia, and early onset atherosclerosis. Analyses of CD3+ and Mac-3+ cells and stainable collagen in hearts showed inflammation and myocyte degeneration in A/J-trac/trac mice beginning postweaning and progressed to marked dilative and fibrosing cardiomyopathy by 140 days. Transmission electron microscopy (TEM) demonstrated myocyte vacuoles consistent with swollen endoplasmic reticulum (ER). Myocytes with cytoplasmic glycogen and irregular actinomyosin filament bundles formed mature intercalated disks with normal myocytes suggesting myocyte repair. A/J-trac/trac mice fed lifelong phytosterol-free diets did not develop cardiomyopathy. BALB/cByJ-trac/trac mice had lesser inflammatory infiltrates and later onset DCM. BALB/cByJ-trac/trac mice changed from normal to phytosterol-free diets had lesser T cell infiltrates but persistent monocyte infiltrates and equivalent fibrosis to mice on normal diets. B- and T-cell-deficient BALB/cBy-Rag1(null) trac/trac mice fed normal diets did not develop inflammatory infiltrates or DCM. We conclude that the trac/trac mouse has many features of inflammatory DCM and that the reversibility of myocardial T cell infiltration provides a novel model for investigating the progression of myocardial fibrosis.

Comparison of the effects of angiotensin II receptor antagonist monotherapy and combination therapy with a diuretic on cardiac function in spontaneously hypertensive rats.

Losartan, an angiotensin II receptor blocker (ARB), has been reported to promote sodium excretion and show an enhanced antihypertensive effect when used in combination with hydrochlorothiazide (HCTZ). We investigated the effects of losartan monotherapy and combination therapy together with HCTZ on cardiac function in hypertensive rats using echocardiography. Spontaneously hypertensive rats (n=21) fed on high-salt diet (8% NaCl) for 13weeks were randomly assigned to rats without medication (HS, n=7), those medicated with ARB (ARB, losartan 30mg/kg/day, n=8), and those with ARB and HCTZ (ARB+HCTZ, losartan 30mg/kg/day+HCTZ 10mg/kg/day, n=6). Blood pressure measurements and echocardiography were performed at 13, 17, and 29weeks of age. After the end of the protocol, the proportion of cardiac muscle fibrosis was measured histologically. In the HS group, blood pressure and left ventricular mass/body weight (LV mass/BW) increased, and % fractional shortening (%FS) and early diastolic mitral annular velocity (e') decreased significantly with age. In the ARB group, although blood pressure and %FS were maintained, LV mass/BW increased with age as in the HS group, and e' decreased. In the ARB+HCTZ group, blood pressure decreased and LV mass/BW, %FS, and e' were maintained. The progression of myocardial fibrosis was clearly prevented in rats treated with ARB. ARB was shown to inhibit systolic disorder and myocardial fibrosis in hypertensive rats. Combination therapy proved to be more effective than monotherapy and is also effective in inhibiting diastolic disorders.

Doxycycline ameliorates the dystrophic phenotype of skeletal and cardiac muscles in mdx mice

We examined whether doxycycline, an antibiotic member of the tetracycline family, improves the histopathology and muscle function in mdx mice, the experimental model of DMD. Doxycycline was administered for 36 days (starting on postnatal day 0) and for 9 months (starting at 8 months of age) in drinking water. Histopathological, biochemical (creatine kinase), and functional (forelimb muscle grip strength) parameters were evaluated in limb, diaphragm, and cardiac muscle. Doxycycline significantly minimized the dystrophic phenotype of skeletal and cardiac muscles and improved forelimb muscle strength. The drug protected muscle fibers against myonecrosis and reduced inflammation. Furthermore, it slowed the progression of myocardial fibrosis. This study provides evidence that doxycycline may be a potential therapeutic agent for DMD.

La fibrose dans l’hypertension artérielle : une histoire d’équilibre

Cardiac remodeling is a deleterious consequence of arterial hypertension. This remodeling results in cardiac transcriptomic changes induced by mechanical and hormonal factors (angiotensin II and aldosterone are the most important). The major features of cardiac remodeling are the hypertrophy of cardiomyocytes, interstitial and perivascular fibrosis, and microvascular rarefaction. Inappropriate stimulation of the renin-angiotensin-aldosterone system (RAAS) participates to the development of heart failure. The respective roles of angiotensin II and aldosterone in cardiac remodeling are poorly understood. The development of fibrosis in the heart depends of a balance between profibrotic (TGFβ, CTGF, inflammation) and antifibrotic (BNP, ANP, BMP4 and BMP7) factors. The profibrotic and proinflammatory effects of angiotensin II and aldosterone are very well demonstrated; however, their actions on antifibrotic factors expression are unknown. In order to explore this, we used RenTgKC mice overexpressing renin into the liver, leading to an increased plasma angiotensin II and thus induction of severe hypertension, and AS mice overexpressing aldosterone synthase (AS) in cardiomyocytes which have a doubled intracardiac aldosterone concentration. Male AS mice have a dysfunction of the coronary arteries relaxation without structural and functional changes of the myocardium. Mice derived from a crossing between the RenTgKC and AS strains were used in this work. It is shown that angiotensin II induces the expression of BNP and BMPs which ultimately slows the progression of myocardial fibrosis, and that aldosterone inhibits the expression of these factors and thus worsens the fibrosis.

Cardiac Fibrosis in Human Transplanted Hearts Is Mainly Driven by Cells of Intracardiac Origin

The aim of our study was to determine the origin of collagen in the progression of myocardial fibrosis in human adult transplanted hearts. Changes in the cardiac interstitial collagen network are thought to contribute to abnormal stiffness and function of the myocardium. The origin of fibrosis-mediating fibroblasts remains incompletely understood, and conflicting data from animal models suggest that they are either derived intracardially or immigrate from extracardiac sources. We studied endomyocardial biopsy specimens from 7 sex-mismatched (female donor heart to a male recipient) heart transplant recipients by a combination of chromogen in situ hybridization using probes specific for Y chromosomes with immunohistochemistry. On the basis of differences in genetic polymorphisms in the type III collagen gene between donor and recipient tissue, we quantitatively determined origin-specific type III collagen gene expression in fibrotic areas containing fibroblasts of putative extracardiac origin. In areas of increased cardiac fibrosis years after heart transplantation, a substantial number of Y chromosome-positive spindle-shaped cells with a fibroblast-like appearance were detected. Many of these cells were identified as macrophages, and measurement of origin-specific type III collagen synthesis identified cells of intracardiac origin as the main source for collagen turnover in human cardiac fibrosis. Our data suggest that, in human myocardium, cardiac fibrosis due to chronic allograft rejection up to 15 years after transplantation or scar formation provoked by mechanical trauma is mainly driven by fibroblasts of intracardiac origin. Antifibrotic treatment strategies, therefore, should target molecular mechanisms that induce fibrillogenesis of cells with intracardiac origin.

β1 Integrin Gene Excision in the Adult Murine Cardiac Myocyte Causes Defective Mechanical and Signaling Responses

How mechanical signals are transmitted in the cardiac myocyte is poorly understood. In this study, we produced a tamoxifen-inducible mouse model in which β1 integrin could be reduced specifically in the adult cardiomyocyte, so that the function of this integrin could be assessed in the postnatal and mechanically stressed heart. The expression of β1 integrin was reduced to 35% of control levels, but function remained normal at baseline. With aortic constriction, the knockout mice survived but had a blunted hypertrophic response. Integrin knockout myocytes, in contrast to controls, showed reduced integrin-linked kinase expression both at baseline and after hemodynamic stress; focal adhesion kinase expression was reduced after stress. Alterations in multiple signaling pathways were detected in the integrin knockout group after acute and chronic hemodynamic stress. Most remarkably, when we challenged the knockout mice with short-term loading, the robust responses of several kinases (extracellular signal-regulated kinase 1/2, p38, and Akt) evident in control mice were essentially abolished in the knockout mice. We also found that reduction of myocyte β1 integrin expression modified adrenergic-mediated signaling through extracellular signal-regulated kinase, p38, and Akt. Reduction of β1 integrin expression in the mature cardiac myocyte leads to a varied response compared with when this protein is reduced during either the embryonic or perinatal period. These results show that β1 integrin expression is required for proper mechanotransductive and adrenergic responses of the adult heart.

Abstract 8831: Micro RNA Could Play Key Roles in Progression of Myocardial Fibrosis in Patients with Heart Failure

Purpose: MicroRNAs (miRNAs) are recently discovered, posttranscriptional regulators of gene expression. Roles of miRNAs in the development of heart failure are largely unknown. Myocardial fibrosis had been fully demonstrated to be involved in pathogenesis of heart failure. However, the molecular mechanisms that underlie myocardial fibrosis remain incompletely understood. We hypothesized that miRNAs might play key roles in the pathogenesis of myocardial fibrosis in patients with heart failure, resulting in progression of heart failure. Methods: This study comprised of 22 patients with idiopathic dilated cardiomyopathy (DCM). We first performed a genome-wide miRNA expression profiling for a total of 650 miRNAs using endomyocardial biopsy specimens obtained from 8 patients. We used the median value of collagen volume fraction (CVF) in endomyocardial biopsy specimens as cutoff to divide these 8 patients into 2 groups. From this screening study, we selected 7 miRNAs related to myocardial fibrosis. We then performed real-time PCR in endomyocardial biopsy specimens from remaining 14 patients with DCM to quantify these 7 miRNAs expressions. Results: In the first screening study, 7 miRNAs were differentially expressed significantly (p < 0.01) in 4 patients with severe myocardial fibrosis compared with 4 patients with less severe myocardial fibrosis (CVF: 4.4 ± 0.9 vs. 2.3 ± 0.3 %, respectively). The real-time PCR in endomyocardial biopsy specimens from remaining 14 patients with DCM revealed that expressions of miRNA-1, miRNA-23, miRNA-210, and miRNA-624 were significantly reduced in 7 patients with severe fibrosis compared with 7 with less severe fibrosis (CVF: 5.8 ± 1.3 vs. 2.0 ± 1.0 %, respectively). Conclusion: We demonstrated that 4 specific miRNAs could play key roles in myocardial fibrosis in patients with DCM. These findings could provide insight into a key conundrum that pervades pathogenesis of heart failure.

Abstract 16834: Cardiac and Circulating Levels of MicroRNA-21 Reflect Myocardial Fibrosis in Aortic Stenosis Patients

Background: Aberrant expression of microRNAs (miRNA) has been recently associated with various cardiovascular pathophysiological conditions and circulating miRNAs are emerging as promising biomarkers. MiR-21 overexpression has been related to cardiac fibrotic responses to biomechanical stress. The aim of this study was to investigate the clinical value of miR-21, cardiac and plasmatic, as biomarker for pathological myocardial fibrosis progression secondary to pressure overload. Methods: In LV biopsies from 17 controls and 39 patients with aortic stenosis (AS), we quantified the expression levels of miR-21 normalized to U6B (qRT-PCR) and determined their relationship with mean transvalvular gradients (continuous wave Doppler) and with myocardial expression of remodeling-related genes (qRT-PCR). Total RNA was isolated from plasma using TRIzol. Spiked-in C. elegans -miR-39 was used as control. Reverse transcription was performed using miR-21 and cel-miR-39 specific primers. qRT-PCR was performed with Taqman assays. miR-21 levels were normalized to cel-miR-39. Results: Myocardial expression levels of miR-21 were significantly higher in AS patients compared with controls (Control: 115±14 vs AS: 189±26; p<0.05) and correlated directly with the mean transvalvular gradient (R=0.51**). A direct relationship between the myocardial expression levels of miR-21 and the mRNA levels of TGF-β1 (R=0.42, p<0.05), its effectors [SMAD4 (R= 0.44; p<0.05) and TAK1 (R=0.41, p<0.05)] and fibrosis-related target genes [collagen I (R=0.47; p<0.01), collagen III (R=0.58; p<0.001) and fibronectin (R=0.61; p<0.05)] was also observed. Plasma levels of miR-21 were up-regulated in AS patients (Control: 15.0±7.5 vs AS: 182.4±97.8; p<0.05) and correlated directly with the myocardial expressions of SMAD4 (R= 0.57; p<0.01), TAK1 (R=0.51, p<0.01), collagen I (R=0.50; p<0.01) and fibronectin (R=0.41; p<0.05). Conclusions: These results support the emerging role of miR-21 as a regulator of the fibrotic process developed in response to pressure overload in AS patients. Our data underscore the value of circulating miR-21 as biomarker of fibrosis with potential prognostic value.

The Development of Myocardial Fibrosis in Transgenic Mice With Targeted Overexpression of Tumor Necrosis Factor Requires Mast Cell–Fibroblast Interactions

Transgenic mice with cardiac-restricted overexpression of tumor necrosis factor (MHCsTNF mice) develop progressive myocardial fibrosis, diastolic dysfunction, and adverse cardiac remodeling. Insofar as tumor necrosis factor (TNF) does not directly stimulate fibroblast collagen synthesis, we asked whether TNF-induced fibrosis was mediated indirectly through interactions between mast cells and cardiac fibroblasts. Cardiac mast cell number increased 2 to 3 fold (P<0.001) in MHCsTNF mice compared with littermate controls. Outcrossing MHCsTNF mice with mast cell-deficient (c-kit(-/-)) mice showed that the 11-fold increase (P<0.001) in collagen volume fraction in MHCsTNF/c-kit(+/-) mice was abrogated in MHCsTNF/c-kit(-/-) mice, and that the leftward shifted left ventricular pressure-volume curve in the MHCsTNF/c-kit(+/-) mice was normalized in the MHCsTNF/c-kit(-/-) hearts. Furthermore, the increase in transforming growth factor β1 and type I transforming growth factor β receptor messenger RNA levels was significantly (P=0.03, P=0.01, respectively) attenuated in MHCsTNF/c-kit(-/-) when compared with MHCsTNF/c-kit(+/-) mice. Coculture of fibroblasts with mast cells resulted in enhanced α-smooth muscle actin expression, increased proliferation and collagen messenger RNA expression, and increased contraction of 3-dimensional collagen gels in MHCsTNF fibroblasts compared with littermate fibroblasts. The effects of mast cells were abrogated by type I transforming growth factor β receptor antagonist NP-40208. These results suggest that increased mast cell density with resultant mast cell-cardiac fibroblast cross-talk is required for the development of myocardial fibrosis in inflammatory cardiomyopathy. Cardiac fibroblasts exposed to sustained inflammatory signaling exhibit an increased repertoire of profibrotic phenotypic responses in response to mast cell mediators.

Differences in Fabry Cardiomyopathy Between Female and Male Patients: Consequences for Diagnostic Assessment

We hypothesized that Fabry cardiomyopathy in female patients might differ substantially from that in male patients and sought to prove this hypothesis in a large cohort consisting of 104 patients with Fabry disease. Fabry cardiomyopathy in male patients is characterized by left ventricular (LV) hypertrophy, impaired myocardial function, and subsequent progressive myocardial fibrosis. In contrast, the occurrence of these 3 cardiomyopathic hallmarks in female patients remains unknown. In 104 patients (58 females, age 42 ± 16 years; 46 males, age 42 ± 13 years) with genetically proven Fabry disease, LV hypertrophy, regional myocardial deformation and myocardial fibrosis were assessed by standard echocardiography, strain rate imaging, and cardiac magnetic resonance (CMR) imaging-guided late enhancement (LE). In men, end-diastolic left ventricular wall thickness (LVWT) ranged from 6 to 19.5 mm (LV mass CMR 55 to 200 g/m(2)), and LE was never seen with LVWT <12 mm (LV mass <99 g/m(2)). In contrast in female patients, LVWT ranged from 5 to 15.5 mm, LV mass ranged from 39 to 146 g/m(2), and LE was already detectable with an LVWT of 9 mm (LV mass 56 g/m(2)). When LV mass was examined in CMR, LE was detected in 23% of the female patients without hypertrophy (n=9), whereas LE was never seen in male patients with normal LV mass. LE was always associated with low systolic strain rate, but the severity of impairment was independent of LVWT in female patients (lateral strain rate in patients with LV hypertrophy with LE -0.7 ± 0.2 s(-1); patients without LV hypertrophy with LE -0.8 ± 0.2 s(-1); p=0.45). In contrast to male patients, the loss of myocardial function and the development of fibrosis do not necessarily require myocardial hypertrophy in female patients with Fabry disease. Thus, in contrast to actual recommendations, initial cardiac staging and monitoring should be based on LV hypertrophy and on replacement fibrosis in female patients with Fabry disease.

Progression of myocardial fibrosis and functional clinical status in Hypertrophic Cardiomyopathy: a study with cardiac magnetic resonance

In 29 patients with HCM (20 males; mean age 42 ± 19 years) we repeated two cardiac magnetic resonance examinations, using a 1.5 Tesla scanner (GE Healthcare, Milwaukee, USA). We evaluated LV mass and volumes and LVEF by the acquisition of conventional SSFP cine short axis images. DE was detected using T1 GRE IR acquired 10 minutes following contrast injection. Quantification of DE was performed as previously described (1). Results At the first CMR DE was detected in 21 subjects (72%), with an average extent of 8.1 ± 8 % of LV mass. CMR was repeated after an average of 772 ± 300 days. At the second CMR exam DE was found in 28 patients (97%). Among them, 16 subjects showed a significant increase of extent of DE (mean augment of 6.9 ± 5.5%, p< 0.0001). During the time interval between the 2 examination, NYHA class worsened in 10 patients who presented higher increase of DE extent than those with preserved functional status (8.3 ± 6.8 vs 3.4 ± 3.1, p < 0.04). Conclusions From these data we conclude that the progression of fibrosis in HCM is fast. The increase of extent of fibrosis in these patients is related to a worse clinical status. Therefore MRI can be applied as an useful safe tool, for longitudinal follow up evaluation of progression of the disease.

Myocardial T1-mapping for early detection of left ventricular myocardial fibrosis in systemic sclerosis

Background Subclinical primary left ventricular (LV) dysfunction is a complication of systemic sclerosis (SSc) related to progressive diffuse myocardial fibrosis. Myocardial T1-mapping has recently been proposed as a cardiac magnetic resonance (CMR) method to quantify interstitial fibrosis early in the disease course whereas late-gadolinium enhancement (LGE) imaging remains normal. Objective We aimed to evaluate whether myocardial T1-mapping could detect subclinical abnormalities in SSc patients with normal standard parameters of LV function and normal LGE imaging. Methods We prospectively studied 37 patients (52±12 years) presenting with SSc with no history of heart disease, no pulmonary hypertension at rest, a normal LV assessed by conventional echocardiography (normal volumes, ejection fraction and wall motion), and no LGE. SSc patients were compared to16 matched controls healthy volunteers (47±7 years old). T1 quantification was performed using a Modified Look-Locker Inversionrecovery (MOLLI) sequence at 1.5T (Siemens) on a LV short axis before, 5min and 15 min after 0.2 mmol/Kg gadolinium injection. Imaging protocol included also standard Cine-SSFP imaging, and LGE imaging. LV diastolic function (mitral inflow pattern) was further assessed using echocardiography. Results A non significant shorter mean T1 time (ms, mean± SEM) was observed in SSc patients compared to controls both at 5 (357±5 vs. 361±6, p=0.65) and 15 (448±5 vs. 456±5, p=0.34) minutes after gadolinium injection. Echocardiography displayed a LV diastolic dysfunction in 47% of SSc patients and in 25% of controls (p=0.04). The SSc patients with a LV diastolic dysfunction had a shorter 15 minutes post-contrast T1 time (ms) than those with a normal diastolic function (431±7 vs. 464±8, p=0.01).

E0027 Growth differentiation factor 15 induce the proliferation of cardiac fibroblasts in a dose dependent manner

ObjectiveGrowth differentiation factor 15(GDF-15) is a member of Transforming growth factor-β superfamily which is one of the most important profibrotic protein released during Inflammation. It has been suggested that GDF-15...

Vascular Damage as an Underlying Mechanism of Cardiac and Cerebral Toxicity in Irradiated Cancer Patients

Radiation is an independent risk factor for cardiovascular and cerebrovascular disease in cancer patients. Modern radiotherapy techniques reduce the volume of the heart and major coronary vessels exposed to high doses, but some exposure is often unavoidable. Radiation damage to the myocardium is caused primarily by inflammatory changes in the microvasculature, leading to microthrombi and occlusion of vessels, reduced vascular density, perfusion defects and focal ischemia. This is followed by progressive myocardial cell death and fibrosis. Clinical studies also demonstrate regional perfusion defects in non-symptomatic breast cancer patients after radiotherapy. The incidence and extent of perfusion defects are related to the volume of left ventricle included in the radiation field. Irradiation of endothelial cells lining large vessels also increases expression of inflammatory molecules, leading to adhesion and transmigration of circulating monocytes. In the presence of elevated cholesterol, invading monocytes transform into activated macrophages and form fatty streaks in the intima, thereby initiating the process of atherosclerosis. Experimental studies have shown that radiation predisposes to the formation of inflammatory plaque, which is more likely to rupture and cause a fatal heart attack or stroke. This paper presents a brief overview of the current knowledge on mechanisms for development of radiation-induced cardiovascular and cerebrovascular damage. It does not represent a comprehensive review of the literature, but reference is made to several excellent recent reviews on the topic.

Detection of long-term progression of myocardial fibrosis in Duchenne muscular dystrophy in an affected family: A cardiovascular magnetic resonance study

Background Detection of myocardial fibrosis and left ventricular dysfunction in Duchenne muscular dystrophy (DMD) is the corner stone for further therapeutic studies. Little is known about the ability of cardiac magnetic resonance imaging (CMR) to evaluate progression of myocardial fibrosis. Aim of our study was to provide CMR data in a previously genotyped DMD family and to evaluate whether progression of myocardial fibrosis could be visualized. Methods and results DMD genotypes were available in 14 family members. CMR was performed in 4/5 carrier females, in 2/2 affected males and in one healthy family member with normal genotype. Functional images and late gadolinium enhanced (LGE) images in contiguous short-axis orientation were acquired at baseline and follow-up of 1231 days CMR examination could be repeated in three carrier females, in one affected male and in the healthy subject previously scanned. Mean decrease of left ventricular ejection fraction during the follow-up period was 10.5 ± 11.0%, mean progression of LGE volume 11.7 ± 9.5%. Conclusions Myocardial fibrosis seems to occur prior to global left ventricular dysfunction in DMD diseased males and carrier females. CMR could be used to evaluate progression of myocardial fibrosis and left ventricular function and may thus serve as an important diagnostic tool in the evaluation of therapeutical options in DMD.

Detection of Progressive Cardiac Dysfunction by Serial Evaluation of Circumferential Strain in Patients With Duchenne Muscular Dystrophy

The present study evaluated progressive cardiac dysfunction using serial circumferential strain (epsilon(cc)) measurements in patients with Duchenne muscular dystrophy (DMD). DMD is characterized by progressive cardiac dysfunction and myocardial fibrosis late in the disease process. We hypothesized that serial epsilon(cc) changes could be detected in individual patients with DMD during a time when the left ventricular ejection fraction (EF) changes are insignificant. Cardiac magnetic resonance imaging data from patients with DMD were evaluated. The left ventricular EF was calculated from steady-state free precession cine images and the composite epsilon(cc) measurement from tagged cine images. The serial epsilon(cc) and EF values for each patient were analyzed using the Wilcoxon sign rank test. Data from 51 patients with DMD (2 studies per patient, mean age at the initial study 11.8 +/- 3.5 years, range 7.4 to 25.4) were analyzed, with a mean interval between cardiac magnetic resonance studies of 15.6 +/- 6.0 months (range 6.2 to 28.1). In the interval between studies, the epsilon(cc) had decreased in all patients with DMD. The average decrease was 1.8 +/- 1.3 (p <0.001). However, the EF had decreased in 33 of the 51 patients and had increased in 18 of the 51 patients. On average, the EF decreased by 2.9 +/- 8.57% (p = NS). In conclusion, in patients with DMD, epsilon(cc) abnormalities indicate progression within a relatively short period when the EF changes were not significant. Serial epsilon(cc) measurements might provide reliable monitoring of the progression of DMD-associated cardiac dysfunction before overt heart failure develops, because it is more sensitive than the EF.

S1P3-mediated cardiac fibrosis in sphingosine kinase 1 transgenic mice involves reactive oxygen species

Sphingosine kinase 1 (SPHK1), its product sphingosine-1-phosphate (S1P), and S1P receptor subtypes have been suggested to play protective roles for cardiomyocytes in animal models of ischaemic preconditioning and cardiac ischaemia/reperfusion injury. To get more insight into roles for SPHK1 in vivo, we have generated SPHK1-transgenic (TG) mice and analysed the cardiac phenotype. SPHK1-TG mice overexpressed SPHK1 in diverse tissues, with a nearly 20-fold increase in enzymatic activity. The TG mice grew normally with normal blood chemistry, cell counts, heart rate, and blood pressure. Unexpectedly, TG mice with high but not low expression levels of SPHK1 developed progressive myocardial degeneration and fibrosis, with upregulation of embryonic genes, elevated RhoA and Rac1 activity, stimulation of Smad3 phosphorylation, and increased levels of oxidative stress markers. Treatment of juvenile TG mice with pitavastatin, an established inhibitor of the Rho family G proteins, or deletion of S1P3, a major myocardial S1P receptor subtype that couples to Rho GTPases and transactivates Smad signalling, both inhibited cardiac fibrosis with concomitant inhibition of SPHK1-dependent Smad-3 phosphorylation. In addition, the anti-oxidant N-2-mercaptopropyonylglycine, which reduces reactive oxygen species (ROS), also inhibited cardiac fibrosis. In in vivo ischaemia/reperfusion injury, the size of myocardial infarct was 30% decreased in SPHK1-TG mice compared with wild-type mice. These results suggest that chronic activation of SPHK1-S1P signalling results in both pathological cardiac remodelling through ROS mediated by S1P3 and favourable cardioprotective effects.

Long‐term therapy with deflazacort decreases myocardial fibrosis in mdx mice

We evaluated the effects of long-term administration of deflazacort (DFZ) on the progression of myocardial fibrosis in mdx mice. Mdx mice (6 months old) were treated with DFZ for 15 months. Myocardial fibrosis (MF) was evaluated by histomorphometric methods, and treated and untreated mdx mice of the same age (21 months) were compared. DFZ significantly decreased MF. We conclude that long-term therapy with DFZ is effective in slowing down the progression of fibrosis in the dystrophin-deficient heart.

Circumferential Strain Analysis Identifies Strata of Cardiomyopathy in Duchenne Muscular Dystrophy: A Cardiac Magnetic Resonance Tagging Study

This study sought to evaluate the natural history of occult cardiac dysfunction in Duchenne muscular dystrophy (DMD).Duchenne muscular dystrophy is characterized by progressive cardiac dysfunction and myocardial fibrosis late in the disease process. We hypothesized that left ventricular myocardial peak circumferential strain (epsilon(cc)) would decrease in DMD before global systolic functional abnormalities regardless of age or ventricular ejection fraction (EF).We evaluated cardiac magnetic resonance image (MRI) data from 70 DMD patients and 16 aged-matched control subjects. Standard imaging data included steady-state free precession short-axis cine stack images, cine myocardial tagged images, and myocardial delayed enhancement (MDE) (an indicator of myocardial fibrosis) sequences. Analysis was performed with QMASS (Medis Medical Imaging Systems, Leiden, the Netherlands) and HARP (Diagnosoft, Palo Alto, California) software. The DMD patient data were subdivided by age (<10 or >10 years), EF (>55% or <55%), and the presence or absence of MDE.The DMD patients with normal EF had reduced epsilon(cc) at an early age (<10 years) compared with control subjects (p < 0.01). The DMD patients age >10 years with normal EF had further decline in epsilon(cc) compared with younger DMD patients (p < 0.01). There was further decline in epsilon(cc) with age in patients with reduced EF (p < 0.01) without MDE. The oldest patients, with both reduced EF and positive MDE, exhibited the lowest epsilon(cc). None of the patients had ventricular hypertrophy.Myocardial strain abnormalities are prevalent in young DMD patients despite normal EF, and these strain values continue to decline with advancing age. Strain analysis in combination with standard MRI and MDE imaging provides a means to stratify DMD cardiomyopathy.