Deletion of the extracellular matrix glycoprotein ADAMTSL3 increases pro-fibrotic signalling and exacerbates heart failure in mice

Background/Introduction

Cardiac fibrosis is a central pathophysiological process accompanying most cardiac diseases including heart failure, and is a predictor of poor outcomes. The fibrotic process is mediated by activated cardiac fibroblasts (CFBs), so-called myofibroblasts, which produce excessive amounts of type I collagen and other ECM molecules. The ADAMTSL family of glycoproteins is upregulated in the cardiac extracellular matrix (ECM) during heart failure, but their function in the heart is unknown. Some ADAMTSL proteins are suggested to regulate the TGFβ, a major driver of myofibroblast activation and cardiac fibrosis.

Purpose

The purpose of this study was to examine the role of ADAMTSL3 in TGFβ-regulation and heart failure.

Methods

ADAMTSL3 expression was analysed in failing hearts of patients and mice. To study the functional role of ADAMTSL3 in the failing heart, an Adamtsl3 knock-out (L3-KO) mouse was generated, and WT and L3-KO littermates were subjected to experimental heart failure by aortic banding (AB), or sham surgery, for a total of six weeks. The mice were followed with echocardiography and MRI, and the left ventricles (LVs) were harvested one and six weeks after AB or sham surgery, with molecular analyses performed. To elucidate molecular functions of ADAMTSL3 in vitro, we overexpressed ADAMTSL3 in CFBs producing an extensive ECM.

Results

We determined that ADAMTSL3 was produced by CFBs and upregulated in failing hearts of patients and mice. The L3-KO mice had a normal cardiac phenotype at baseline, but upon increased LV afterload developed a dilated cardiomyopathy phenotype with increased LV dilation and reduced systolic function from one week post-AB. Furthermore, high mortality was observed in the L3-KO mice post-AB, with 60% vs. 96% survival of WTs over six weeks. At one week post-AB RNA sequencing of LVs revealed 233 differentially expressed genes in L3-KO vs. WT, with Col1a1 and Postn among the most upregulated, suggesting increased fibrosis and TGFβ signalling. Increased canonical TGFβ signalling was confirmed by increased SMAD2/3 phosphorylation and increased Lox expression in L3-KOs six weeks post-AB. In vitro, ADAMTSL3 overexpression in cultured CFBs resulted in reduced collagen synthesis and reduced expression of COL1A1, LOX, CTGF and POSTN, indicating anti-fibrotic properties. Furthermore, ADAMTSL3 inhibited the expression of ACTA2 and SPP1, reduced α-SMA protein by 25%, and reduced proliferation and CFB contraction, suggesting attenuated TGFβ signalling and inhibited myofibroblast differentiation.

Conclusions

ADAMTSL3 was upregulated in human and mouse heart failure, and served an anti-fibrotic and cardio-protective role in failing mouse hearts. Mechanistically, ADAMTSL3 was produced by CFBs and inhibited myofibroblast differentiation and collagen synthesis through TGFβ in cultured CFBs.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Research Council of Norway

National Early Warning Score 2 provides independent prognostic information in patients hospitalized with heart failure with preserved ejection fraction

Background

Heart failure (HF) hospitalisation is a strong predictor of long-term mortality among HF patients. Current European Society of Cardiology HF guidelines do not include recommendations for post-discharge long-term risk prediction for acute HF, despite several cardiac biomarkers and clinical scoring systems being able to predict long-term prognosis. In Europe, the clinical scoring system National Early Warning Score 2 (NEWS2) is increasingly being used for in-hospital risk prediction, and several recent studies have demonstrated a potential to utilize NEWS2 for long-term risk prediction.

Purpose

To assess the long-term prognostic accuracy of NEWS2 in patients hospitalised with acute HF in comparison to N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin T (hs-cTnT), and their differences in prognostic accuracy for HF subgroups with reduced (HFrEF) and preserved (HFpEF) ejection fraction.

Methods

In the Akershus Cardiac Examination 2 Study, we measured hs-cTnT and NT-proBNP and calculated NEWS2 within 24 hours of admission in patients hospitalised due to acute dyspnea (n=314). Patients with acute HF as adjudicated index diagnosis were included in the current sub-study (n=143). We assessed post-discharge long-term risk of all-cause mortality by receiver operating characteristic (ROC) analysis and Cox regression models.

Results

During median follow-up of 26 (quartile 1–3 8–33) months, 66 patients (46%) died. Patients with poor prognosis had higher NEWS2 (mean 5.9 vs 4.4 points, p=0.004), hs-cTnT concentrations (median 49 vs 27 ng/L, p=0.002), and NT-proBNP concentrations (median 5776 vs 2593 ng/L, p<0.001) compared to patients with favourable prognosis. Stratified by HF subgroups, the area under the ROC curve (ROC AUC) for NEWS2 to predict mortality was superior for HFpEF (ROC AUC 0.79, 95% CI 0.66–0.92) compared to HFrEF (ROC AUC 0.57, 95% CI 0.45–0.69; p=0.012) (Figure). In contrast, prognostic accuracy in HFrEF and HFpEF were comparable for hs-cTnT (ROC AUC 0.64 vs 0.67, p=0.76) and NT-proBNP (ROC AUC 0.72 vs 0.71, p=0.94) (Table). After adjustment for age, sex, body mass index, systolic blood pressure, history of coronary artery disease and estimated glomerular filtration rate, NEWS2 was associated with mortality for HFpEF patients (HR 1.37, 95% CI 1.13–1.66), while no association was found for NEWS2 to predict mortality in HFrEF patients (HR 1.03, 95% CI 0.93–1.15; p for interaction=0.016).

Conclusion(s)

NEWS2 is a superior prognostic marker among patients hospitalised with HFpEF compared to HFrEF and might be a valuable and readily available tool to prognosticate patients at hospital discharge.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research grant from the Norwegian Research Council and internal grants from Akershus University Hospital to Torbjørn Omland and Helge Røsjø.

Synapsin 2 regulates NCX1 trafficking and is down-regulated in the failing myocardium, which increases the risk of ventricular arrhythmia and heart failure mortality

Background

Synapsin 2 (Syn2) modulates vesicle transport in the post-synaptic terminal in the brain, and has been linked to sudden unexplained death in epilepsy, but has never previously been studied in the myocardium.

Purpose

Given the association of vesicle transport in the brain and the heart, and the similarity of sudden death in epilepsy and cardiac arrhythmias, we have studied the role of Syn2 in the heart.

Methods

We explored left ventricular (LV) Syn2 levels in various experimental heart failure (HF) models and assessed mortality in Syn2 knock out (KO) mice vs. wild type (WT) littermates after pressure-overload induced by aortic banding. We used confocal imaging and virus transduction to characterize Syn2 localization and co-localization with NCX and Rab proteins. We verified Syn2-NCX interaction by immunoprecipitation, mass spectrometry, and surface resonance experiments. We investigated calcium handling in isolated cardiomyocytes. Susceptibility for ventricular arrhythmias was also tested in Langendorff-perfused hearts.

Results

We found Syn2, but not synapsin 1, to be expressed in the myocardium. LV Syn2 levels were markedly downregulated in the failing myocardium after experimental myocardial infarction or aortic banding. Syn2 KO mice had increased mortality compared to WT littermates following aortic banding, but demonstrated no clear clinical or echocardiographic phenotype, except reduced fractional shortening. Given no clear etiology for increased mortality, we next explored the association between Syn2 and ion-channel vesicle transport, calcium handling and ventricular arrhythmias. By confocal imaging and viral transduction, we found Syn2 to localize in vesicles in HL-1 cells, where Syn2 co-localized with Rab2, Rab3, Rab7 and NCX1. Syn2 was also found to interact with NCX1 as tested by immunoprecipitation, mass spectrometry, and surface resonance experiments. NCX1 levels were downregulated in the membrane fraction in the left ventricle of Syn2 KO mice compared to WT littermates following aortic banding. We observed increased frequency of calcium sparks and waves in isolated Syn2 KO cardiomyocytes compared to controls. We found enhanced susceptibility of Syn2 KO mice for ventricular arrhythmias compared to WT littermates mice during ISO stress testing in explanted hearts. Hearts from Syn2 KO mice also demonstrated more severe ventricular arrhythmias compared to hearts from WT littermates controls.

Conclusions

We report for the first time that Syn2 is expressed in the myocardium and that Syn2 seems to regulate NCX1 transport and localization. We also found markedly reduced LV Syn2 levels in HF individuals and mice that lacked Syn2 more frequent displayed severe ventricular arrhythmias and had increased mortality. Hence, our data suggest that reduced Syn2 in the failing myocardium may lead to increased mortality, possibly linked to altered NCX trafficking and subsequent ventricular arrhythmias.

Funding Acknowledgement

Type of funding sources: None.

Beneficial effects of exercise training on expression of fibrosis-related genes in a mouse model of hypertrophic cardiomyopathy

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): South-Eastern Norway Regional Health Authority (HSØ)

KG Jebsen Cardiac Research Center

Background

The effects of exercise training prior to manifestation of phenotype in hypertrophic cardiomyopathy (HCM) are unknown. In mice carrying the HCM-pathogenic α-MHC R403Q/+ (R403Q) genetic variant, accelerated progression of the HCM phenotype is induced by cyclosporine A (CsA). We used this model to determine if exercise training initiated before phenotype development could limit disease severity.

Methods

R403Q mice were allocated to treadmill exercise training (N=23) or sedentary behavior (N=23) for 6 weeks. For the last three weeks of the 6-week period, all mice received CsA to induce the HCM phenotype. Cardiac imaging (echocardiography or MRI) and exercise testing were performed at the 0, 3 and 6-week time points. After the 6-week exercise protocol, left ventricles were harvested for molecular analyses.

Results

After 6 weeks, exercise trained mice ran 2-fold further during testing than sedentary mice (p<0.0001), and 2-fold further than at baseline (p<0.0001). There was no difference in VO2 max between groups.  Cardiac imaging did not reveal differences in hypertrophy between exercised and sedentary HCM mice. However, we observed a reduction in cardiac expression of key fibrosis-related genes in the exercise group, i.e. Col1a2 to 49 % (p=0.03), Col1a1 to 50 % (p=0.03), Col3a1 to 46 % (p=0.02), Fn1 to 49 % (p=0.01) and Lox to 58 % (p=0.05) of levels in the sedentary group. HPLC did not reveal differences in collagen protein.

Conclusion

Exercise training initiated prior to manifestation of the HCM phenotype in mice results in lowered production of key fibrosis-related genes, including structural collagens. Further analysis is needed to determine the functional consequences of these beneficial changes in gene expression.

Exercise training inhibits left ventricular collagen upregulation in mice with hypertrophic cardiomyopathy

Background

Hypertrophic cardiomyopathy (HCM) is estimated to affect 1:500, and is characterised by otherwise unexplained left ventricular (LV) hypertrophy, cardiomyocyte disarray, fibrosis, diastolic dysfunction, and ventricular arrhythmias. Historically, patients with HCM have been discouraged from participation in high intensity sports and exercise. However, the 2020 Sports Cardiology Guidelines recommend that patients with HCM should receive advice about exercise training (ET) based on individual risk assessment. To learn more about the effects of ET in HCM, we exposed mice carrying an HCM-causative sarcomere mutation (Myh6R403Q/+ (R403Q) mice) to high intensity interval training.

Purpose

To investigate the effect of exercise training on hypertrophic cardiomyopathy in mice.

Methods

R403Q mice were stratified to treadmill exercise (n=11) or sedentary behaviour (n=11). After 3 weeks, we induced HCM by giving CsA in the feed for 3 weeks, while the ET or sedentary behaviour continued for a total of 6 weeks. Each bout of treadmill running consisted of a 10-minute warm up, followed by 5 intervals of 8 minutes at high intensity (90% of VO2 max speed at week 0) and 2 minutes at medium intensity (60% of VO2 max speed at week 0). Every third day of the ET protocol we increased the high and medium intensity running speeds by 0.6 and 0.4 m/min, respectively. We performed echocardiography after 0, 3, and 6 weeks of the 6-week protocol. After completion of the protocol, we recorded lung and whole heart weight, and harvested LVs for molecular analyses.

Results

Confirming the expected HCM phenotype, R403Q mice that received CsA (R403Q SED+CsA) had a 1.3-fold increase in whole heart weight (p<0.0001), 1.5-fold increase in lung weight (p<0.001), and 2.4-fold increase in maximal left ventricular posterior wall (LVPW) thickness measured by echocardiography (p<0.0001) compared to sedentary wild type littermates given CsA (WT SED+CsA). Heart weight, lung weight, and maximum LVPW thickness were also increased 1.5- (p<0.0001), 1.6- (p<0.0001), and 2.0-(p<0.0001) fold, respectively, compared to R403Q not given CsA (R403Q SED-CsA). R403Q ET+CsA mice increased their running distance before exhaustion 2.0-fold compared to baseline (p=0.010), and ran 1.6-fold longer than R403Q SED+CsA (p=0.020). In R403Q ET+CsA mice, LV mRNA expression of Col1a2 was 51% (p=0.021), and Col3a1 49% (p=0.013) of R403Q SED+CsA expression levels. Compared to R403Q SED+CsA mice, exercise training did not affect heart weight, maximum LV posterior wall thickness or lung weight in R403Q ET+CsA mice.

Conclusion

Treadmill ET inhibited upregulation of LV collagen expression in mice with HCM, but did not affect hypertrophy. This could indicate that ET during early development of HCM attenuates development of fibrosis.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): South-Eastern Norway Regional Health Authority (Helse Sør-Øst RHF) and KG Jebsen Cardiac Research Center

Cardiac fibroblasts acquire properties of matrifibrocytes in vitro and in mice with pressure overload-induced congestive heart failure

Introduction

Activation of cardiac fibroblasts (CFB) is a key step in development of fibrosis in the heart. It was recently shown that, in addition to the well-studied myofibroblast (myoFB) phenotype, activated cardiac fibroblasts can adopt a newly defined matrifibrocyte phenotype, characterized by expression of extracellular matrix (ECM) genes associated with bone, cartilage and tendon development. However, it is unknown whether matrifibrocytes exists in the pressure-overloaded fibrotic and failing heart, and whether substrate stiffness drives differentiation.

Hypothesis

Matrifibrocyte differentiation occurs in vitro during culturing of primary cardiac fibroblasts, and in vivo in response to left ventricular pressure overload.

Methods

Left ventricular pressure overload induced by o-ring aortic banding (ORAB) induced cardiac phenotypes of concentric hypertrophic remodelling and congestive heart failure. Primary CFB from adult mice were cultured on plastic or soft polyacrylamide hydrogels (4.5 kPa) for various times. mRNA expression of phenotypic markers were measured by RT-PCR. Presence of smooth muscle α-actin (SMA) fibers was determined by immunocytochemistry.

Results

ECM genes normally expressed in bone and cartilage (COMP, CILP-2, OPG and SCX) were upregulated in hypertrophic left ventricles of mice with congestive heart failure. The myoFB marker acta2 was increased 2 weeks after ORAB, returned to baseline at 4 weeks and increased again at 20 weeks when the left ventricle was dilating and failing, indicating that the myoFB phenotype is not permanent. In vitro, primary CFB upregulated bone/cartilage-associated ECM genes after 12 days of culturing on plastic. Acta2 mRNA and SMA protein levels peaked after 9 days in culture whereafter they declined, indicating a shift in phenotype. Culturing primary CFB on soft (4.5 kPa) hydrogels delayed, but did not prevent, myoFB differentiation while expression of bone/cartilage ECM genes was absent or low, indicating that high stiffness is a driver of the matrifibrocyte phenotype. Blockers of mechanotransduction, SB431542 (TGFβRI inhibitor), Y27623 (ROCK inhibitor) and cyclosporine A (calcineurin inhibitor), completely inhibited myoFB differentiation but upregulated several matrifibrocyte markers, indicating that distinct signaling pathways regulate myoFB and matrifibrocyte differentiation. Removing inhibitors re-induced myofibroblast markers in cells on plastic but not on soft gels consistent with high stiffness promoting myofibroblast differentiation.

Conclusion

Primary cardiac fibroblasts acquire characteristics of matrifibrocytes in vitro when cultured for long time on plastic and in vivo in left ventricles of mice with pressure overload-induced congestive heart failure.

Funding Acknowledgement

Type of funding source: Public grant(s) – EU funding. Main funding source(s): Marie Sklodowska-Curie Individual Fellowship

Circulating secretoneurin concentrations are increased in patients with acute coronary syndrome and provide prognostic information

Background

Secretoneurin (SN) is associated with both myocardial ischemia and cardiomyocyte Ca2+ handling, and circulating SN levels provide incremental prognostic information to established risk indices in patients with acute heart failure, acute respiratory failure, and after cardiac arrest.

Purpose

To determine whether SN concentrations are increased in patients with acute coronary syndrome (ACS), and assess the prognostic value of SN among patients with suspected ACS.

Methods

We included 402 patients hospitalized with chest pain at a teaching hospital and adjudicated all hospitalizations as ACS or non-ACS by two physicians working independently. Blood samples were drawn within 24 h from hospital admission and SN was measured by a novel ELISA assay. Patients were followed for mean 6.2 years and mortality was obtained from the Norwegian Cause of Death Registry.

Results

SN concentrations were higher in patients with ACS (n=161 [40%]) compared to patients with chest pain without ACS (n=241 [60%]): median 32.8 (IQR 27.5–42.8) vs. 28 (24.5–34.0) pmol/L, p<0.001. The C-statistics of SN was 0.66 (95% CI: 0.61–0.71) to separate chest pain patients with ACS from chest pain patients without ACS compared to 0.82 (0.78–0.86) for high-sensitivity cardiac troponin T (hs-cTnT). Patients with ECG changes reflective of acute myocardial ischemia had higher SN concentrations (p=0.005). Sixty-five (16%) patients died during follow-up. Stratifying patients according to SN concentrations separated patients with a poor and favorable prognosis, and patients with SN in the top quartile had 4-fold higher risk of mortality compared to the patients with low SN concentrations (Figure). Higher SN concentrations were also associated with increased risk of mortality in Cox regression models, including in models that adjusted for age, sex, blood pressure, previous myocardial infarction, atrial fibrillation, and heart failure: hazard ratio 1.71 (1.03–2.84), p=0.038. The C-statistics of SN to separate patients with poor prognosis from favorable prognosis was 0.72 (0.65–0.79) and adding SN on top of hs-cTnT improved prognostication as assessed by the integrated discrimination index: 0.05±0.014, p<0.001.

Conclusions

SN concentrations are increased in patients with ACS and provide prognostic information in patients with chest pain.

Figure 1

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): Akershus Unviersity Hospital, CardiNor AS

P3528Circulating microRNA-210 concentrations are increased in patients with acute heart failure and provide prognostic information

Background

MicroRNA (miR)-210 is induced by cellular hypoxia and circulating miR-210 concentrations are associated with clinical outcome in patients with myocardial infarction and aortic stenosis. Whether circulating miR-210 concentrations provide diagnostic and prognostic information in unselected patients with dyspnea is not known.

Purpose

To assess the diagnostic and prognostic value of circulating miR-210 concentrations in patients hospitalised due to acute dyspnea.

Methods

We extracted microRNA from plasma samples obtained on admission from 314 patients hospitalised for acute dyspnea and 10 healthy control subjects. miR-210 concentrations were measured by quantitative polymerase chain reaction and we used miR-425 for normalisation. The merit of circulating miR-210 concentrations to diagnose and provide prognostic information in patients with acute heart failure (HF) was compared to the merit of N-terminal pro-B-type natriuretic peptide (NT-proBNP).

Results

In total, 143 patients (46%) were adjudicated as hospitalised due to acute heart failure (HF) and 84 patients (27%) due to acute exacerbation of chronic obstructive lung disease (AECOPD). All patients and control subjects had miR-210 concentrations within the range of detection (Cq 26–32) and analytical variation was low. miR-210 concentrations correlated with age, NT-proBNP and cardiac troponin T concentrations in the total cohort. Circulating miR-210 concentrations were increased in patients with HF (4.7±3.3 fold increase, p<0.0001) and AECOPD (3.4±1.7 fold increase, p<0.0001) compared to control subjects. Circulating miR-210 concentrations were not different between patient groups and receiver operating characteristics area under the curve (AUC) for miR-210 to diagnose acute HF was 0.50 (95% CI 0.43–0.57) compared to AUC 0.85 (0.81–0.89) for NT-proBNP. During a median 817 days of follow-up, 66 patients (46%) with acute HF died and 35 patients (42%) with AECOPD died. Circulating miR-210 concentrations separated acute HF patients with a poor and favourable outcome (Figure 1; p by the log rank test =0.017). Circulating miR-210 concentrations were also associated with mortality during follow-up in Cox regression model: hazard ratio (HR) for lnRQ of miR-210 was 2.11 (95% CI 1.27–2.50), p=0.004. The association between circulating miR-210 concentrations and outcome was attenuated and no longer significant after adjusting for NT-proBNP concentrations. Circulating miR-210 concentrations did not predict outcome in patients with AECOPD: HR 1.38 (0.65–2.93); p=0.4.

Figure 1

Conclusions

Circulating miR-210 concentrations are increased in patients with acute HF, and provide prognostic information during follow-up. Still, circulating miR-210 concentrations did not diagnose acute HF among unselected patients with dyspnea and the association with outcome was attenuated by NT-proBNP.

Acknowledgement/Funding

Nasjonalforeningen for Folkehelsen

P1544Circulating secretoneurin concentrations provide incremental prognostic information to established risk indices in patients with moderate to severe aortic stenosis

Background

Secretoneurin (SN) concentrations provide important prognostic information in patients with myocardial dysfunction. Whether preoperative SN concentrations improve risk assessment in patients with moderate to severe aortic stenosis (AS) is unknown.

Methods

We included 57 patients with moderate to severe AS referred for presurgical evaluation and recorded all-cause mortality during follow-up. All patients were examined with comprehensive echocardiography, electrocardiogram (ECG), and high-sensitivity cardiac troponin T (hs-TnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) measurements.

Results

Median (quartile 1–3) SN concentration in the AS patients was 141 (121–163) pmol/L. Lower estimated creatinine clearance and use of diuretics, but not standard ECG or echocardiographic indices and cardiac biomarkers, were associated with increasing SN concentrations. In total, 15 patients (26%) died during 3.5 years median follow-up. SN concentrations were higher in non-survivors than survivors: 156 (133–209) vs. 140 (116–155) pmol/L, p=0.007. The optimal cut-off concentration for SN in discriminating long-term mortality was 147 pmol/L (sensitivity 67% [95% CI 38–88%], specificity 74% [58–86%]) and patients with SN concentrations above the optimal cut-off had worse prognosis than patients below the cut-off (Figure; p=0.005 with the log-rank test). Higher SN concentrations were associated with increased risk of mortality after adjustment for clinical risk factors, echocardiographic and ECG variables, hs-TnT and NT-proBNP concentrations, and whether patients were subjected to aortic valvular surgery (n=34): hazard ratio per lnSN 15.13 (95% CI 1.05–219.00); p=0.046. Receiver operating characteristics area under the curve for SN to predict mortality was 0.74 (95% CI 0.60–0.88) compared to 0.73 (0.59–0.87) for hs-TnT and 0.67 (0.51–0.82) for NT-proBNP.

Conclusions

SN concentrations seem to reflect additional pathophysiology to established risk indices and improve risk assessment in patients with moderate to severe AS.

Bone turnover markers are differentially affected by pre-analytical handling

Given that bone turnover markers are often shipped to central laboratories, it is essential to be aware of factors that will affect stability. We have evaluated how sample type, time before separation of blood samples, and time between separation and analysis affect the stability of four bone turnover markers.

INTRODUCTION

Bone turnover markers are often shipped to central laboratories for analysis, which require knowledge of the stability of the markers of interest in different sample materials. The aim of the current study was to evaluate how time before separation of blood samples and time between separation and analysis affect the stability of four bone turnover markers in serum and plasma samples.

METHODS

Serum, EDTA, and Lithium heparin (LiHep) plasma samples from seven osteoporosis patients and three healthy controls were collected and stored at room temperature for up to 72 h before separation and analysis. After separation, samples were stored at room temperature for up to 72 h and re-analyzed. The bone turnover markers N-terminal pro-collagen type 1 extension pro-peptide (P1NP), bone-specific alkaline phosphatase (BAP), C-terminal teleopeptide cross links of collagen type 1 (CTX), and osteocalcin (OC) were analyzed using the automated iSYS IDS platform.

RESULTS

P1NP and BAP were stable in both plasma and serum for 72 h before centrifugation. CTX levels were higher in EDTA plasma at all time points compared to LiHep plasma and serum. The use of EDTA plasma prolonged the stability of CTX as compared to LiHep plasma and serum. Osteocalcin showed high tendency to degrade in all sample types and concentrations were significantly lower after 24 h of storage.

CONCLUSIONS

For the bone turnover markers P1NP and BAP, the use of both plasma and serum is recommended. Samples for CTX analysis should be taken as EDTA plasma. Samples for osteocalcin analysis can be taken in either type of plasma or serum, but should be analyzed within 3 h or preserved at - 18 °C.

Cardiomyocyte substructure reverts to an immature phenotype during heart failure

Key points

As reactivation of the fetal gene program has been implicated in pathological remodelling during heart failure (HF), we examined whether cardiomyocyte subcellular structure and function revert to an immature phenotype during this disease.

Surface and internal membrane structures appeared gradually during development, and returned to a juvenile state during HF. Similarly, dyadic junctions between the cell membrane and sarcoplasmic reticulum were progressively ‘packed’ with L‐type Ca²⁺ channels and ryanodine receptors during development, and ‘unpacked’ during HF.

Despite similarities in subcellular structure, dyads were observed to be functional from early developmental stages, but exhibited an impaired ability to release Ca²⁺ in failing cardiomyocytes.

Thus, while immature and failing cardiomyocytes share similarities in subcellular structure, these do not fully account for the marked impairment of Ca²⁺ homeostasis observed in HF.

Abstract

Reactivation of the fetal gene programme has been implicated as a driver of pathological cardiac remodelling. Here we examined whether pathological remodelling of cardiomyocyte substructure and function during heart failure (HF) reflects a reversion to an immature phenotype. Using scanning electron microscopy, we observed that Z‐grooves and t‐tubule openings at the cell surface appeared gradually during cardiac development, and disappeared during HF. Confocal and super‐resolution imaging within the cell interior revealed similar structural parallels; disorganization of t‐tubules in failing cells was strikingly reminiscent of the late stages of postnatal development, with fewer transverse elements and a high proportion of longitudinal tubules. Ryanodine receptors (RyRs) were observed to be laid down in advance of developing t‐tubules and similarly ‘orphaned’ in HF, although RyR distribution along Z‐lines was relatively sparse. Indeed, nanoscale imaging revealed coordinated packing of L‐type Ca²⁺ channels and RyRs into dyadic junctions during development, and orderly unpacking during HF. These findings support a ‘last in, first out’ paradigm, as the latest stages of dyadic structural development are reversed during disease. Paired imaging of t‐tubules and Ca²⁺ showed that the disorganized arrangement of dyads in immature and failing cells promoted desynchronized and slowed Ca²⁺ release in these two states. However, while developing cells exhibited efficient triggering of Ca²⁺ release at newly formed dyads, dyadic function was impaired in failing cells despite similar organization of Ca²⁺ handling proteins. Thus, pathologically deficient Ca²⁺ homeostasis during HF is only partly linked to the re‐emergence of immature subcellular structure, and additionally reflects lost dyadic functionality.

As reactivation of the fetal gene program has been implicated in pathological remodelling during heart failure (HF), we examined whether cardiomyocyte subcellular structure and function revert to an immature phenotype during this disease.

Surface and internal membrane structures appeared gradually during development, and returned to a juvenile state during HF. Similarly, dyadic junctions between the cell membrane and sarcoplasmic reticulum were progressively ‘packed’ with L‐type Ca²⁺ channels and ryanodine receptors during development, and ‘unpacked’ during HF.

Despite similarities in subcellular structure, dyads were observed to be functional from early developmental stages, but exhibited an impaired ability to release Ca²⁺ in failing cardiomyocytes.

Thus, while immature and failing cardiomyocytes share similarities in subcellular structure, these do not fully account for the marked impairment of Ca²⁺ homeostasis observed in HF.

Many Analysts, One Data Set: Making Transparent How Variations in Analytic Choices Affect Results

Twenty-nine teams involving 61 analysts used the same data set to address the same research question: whether soccer referees are more likely to give red cards to dark-skin-toned players than to light-skin-toned players. Analytic approaches varied widely across the teams, and the estimated effect sizes ranged from 0.89 to 2.93 ( Mdn = 1.31) in odds-ratio units. Twenty teams (69%) found a statistically significant positive effect, and 9 teams (31%) did not observe a significant relationship. Overall, the 29 different analyses used 21 unique combinations of covariates. Neither analysts’ prior beliefs about the effect of interest nor their level of expertise readily explained the variation in the outcomes of the analyses. Peer ratings of the quality of the analyses also did not account for the variability. These findings suggest that significant variation in the results of analyses of complex data may be difficult to avoid, even by experts with honest intentions. Crowdsourcing data analysis, a strategy in which numerous research teams are recruited to simultaneously investigate the same research question, makes transparent how defensible, yet subjective, analytic choices influence research results.

Overexpression of integrin α11 induces cardiac fibrosis in mice

AIM

To understand the role of the collagen-binding integrin α11 in vivo, we have used a classical approach of creating a mouse strain overexpressing integrin α11. A transgenic mouse strain overexpressing α11 in muscle tissues was analysed in the current study with special reference to the heart tissue.

METHODS

We generated and phenotyped integrin α11 transgenic (TG) mice by echocardiography, magnetic resonance imaging and histology. Wild-type (WT) mice were subjected to aortic banding (AB) and the expression of integrin α11 was measured in flow cytometry-sorted cardiomyocytes and non-myocytes.

RESULTS

TG mice developed left ventricular concentric hypertrophy by 6 months, with increased collagen deposition and reactivation of mRNA encoding foetal genes associated with cardiovascular pathological remodelling compared to WT mice. Masson's trichrome staining revealed interstitial fibrosis, confirmed additionally by magnetic resonance imaging and was found to be most prominent in the cardiac septum of TG but not WT mice. TG hearts expressed increased levels of transforming growth factor-β2 and transforming growth factor-β3 and upregulated smooth muscle actin. Macrophage infiltration coincided with increased NF-κB signalling in TG but not WT hearts. Integrin α11 expression was increased in both cardiomyocytes and non-myocyte cells from WT AB hearts compared to sham-operated animals.

CONCLUSION

We report for the first time that overexpression of integrin α11 induces cardiac fibrosis and left ventricular hypertrophy. This is a result of changes in intracellular hypertrophic signalling and secretion of soluble factors that increase collagen production in the heart.

Seasonal variation in accumulation of persistent organic pollutants in an Arctic marine benthic food web

The aim of the present study was to investigate seasonal variation in persistent organic pollutant (POP) concentrations, as well as food-web biomagnification, in an Arctic, benthic marine community. Macrozoobenthos, demersal fish and common eiders were collected both inside and outside of Kongsfjorden, Svalbard, during May, July and October 2007. The samples were analysed for a selection of legacy chlorinated POPs. Overall, low levels of POPs were measured in all samples. Although POP levels and accumulation patterns showed some seasonal variation, the magnitude and direction of change was not consistent among species. Overall, seasonality in bioaccumulation in benthic biota was less pronounced than in the pelagic system in Kongsfjorden. In addition, the results indicate that δ(15)N is not a good predictor for POP-levels in benthic food chains. Other factors, such as feeding strategy (omnivory, necrophagy versus herbivory), degree of contact with the sediment, and a high dependence on particulate organic matter (POM), with low POP-levels and high δ(15)N-values (due to bacterial isotope enrichment), seem to govern the uptake of the different POPs and result in loads deviating from what would be expected consulting the trophic position alone.

Current status, between-year comparisons and maternal transfer of organohalogenated compounds (OHCs) in Arctic char (Salvelinus alpinus) from Bjørnøya, Svalbard (Norway)

High levels of organohalogenated compounds (OHCs) have been found in Arctic char from Lake Ellasjøen at Bjørnøya (Svalbard, Norway) compared to char from other arctic lakes. The first aim of the study was to investigate the OHC status, contaminant profile, and partitioning of OHCs between muscle and ovary tissue in spawning female char from the high-polluted Lake Ellasjøen and the low-polluted Lake Laksvatn. The second aim was to investigate if OHC levels in muscle tissue have changed over time. Between-lake comparisons show that the muscle levels (lipid weight) of hexachlorobenzene (HCB), chlordanes (∑CHLs), mirex, dichlorodiphenyltrichloroethanes (∑DDTs) and polychlorinated biphenyls (∑PCBs) were up to 36 times higher in char from Ellasjøen than in Laksvatn, and confirm that the char from Ellasjøen are still heavily exposed compared to char from neighboring lake. A higher proportion of persistent OHCs were found in Ellasjøen compared to Laksvatn, while the proportion of the less persistent OHCs was highest in Laksvatn. A between-year comparison of OHC levels (i.e., HCB, DDTs, PCBs) in female and male char shows higher levels of HCB in female char from Ellasjøen in 2009/2012 compared to in 1999/2001. No other between-year differences in OHC levels were found. Due to small study groups, findings associated with between-year differences in OHC levels should be interpreted with caution. OHCs accumulate in the lipid rich ovaries of spawning females, resulting in up to six times higher levels of OHCs in ovaries compared to in muscle (wet weight). The toxic equivalent (TEQ)-value for the dioxin-like PCBs (PCB-105 and -118) in ovaries of the Ellasjøen char exceeded levels associated with increased egg mortality in rainbow trout (Oncorhynchus mykiss). Hence, we suggest that future studies should focus on the reproductive health and performance abilities of the high-exposed population of char inhabiting Lake Ellasjøen.

Reduced visfatin levels in aortic stenosis increase after aortic valve replacement and may contribute to reverse left ventricular remodelling

AIM

Visfatin may play a part in reverse left ventricular remodelling. Using a mouse model of reversible left ventricle pressure overload, we examined if visfatin was altered in the myocardium. Furthermore, we addressed this issue in patients with aortic stenosis (AS) and examined whether visfatin levels are related to reverse remodelling following aortic valve replacement (AVR).

METHODS

Myocardial visfatin was analysed after aortic banding (AB) and debanding (DB) in mice and compared to sham operated animals. Myocardial visfatin was measured in biopsies from patients undergoing AVR and compared to controls. Serum visfatin was measured before and after AVR in patients with AS and correlated with echocardiographic measurments of cardiac morphology and function.

RESULTS

Four weeks after AB, myocardial visfatin protein was reduced by 50% compared to sham. Three days after DB, myocardial protein levels increased significantly. Myocardial visfatin and serum visfatin levels were reduced by 23% and 64%, respectively, in patients with AS compared to controls. Twelve months after AVR, serum visfatin levels increased compared to preoperative values and correlated negatively with degree of left ventricular hypertrophy.

CONCLUSION

Myocardial visfatin and serum visfatin levels are reduced by cardiac pressure overload. Visfatin levels increase after correction of pressure overload and may play a part in postoperative reverse remodelling.

IL-18 neutralization during alveolar hypoxia improves left ventricular diastolic function in mice

AIM

In patients, an association exists between pulmonary diseases and diastolic dysfunction of the left ventricle (LV). We have previously shown that alveolar hypoxia in mice induces LV diastolic dysfunction and that mice exposed to hypoxia have increased levels of circulating interleukin-18 (IL-18), suggesting involvement of IL-18 in development of diastolic dysfunction. IL-18 binding protein (IL-18BP) is a natural inhibitor of IL-18. In this study, we hypothesized that neutralization of IL-18 during alveolar hypoxia would improve LV diastolic function.

METHODS

Mice were exposed to 10% oxygen for 2 weeks while treated with IL-18BP or vehicle. Cardiac function and morphology were measured using echocardiography, intraventricular pressure measurements and magnetic resonance imaging (MRI). For characterization of molecular changes in the heart, both real-time PCR and Western blotting were performed. ELISA technique was used to measure levels of circulating cytokines.

RESULTS

As expected, exposure to hypoxia-induced LV diastolic dysfunction, as shown by prolonged time constant of isovolumic relaxation (τ). Improved relaxation with IL-18BP treatment was demonstrated by a significant reduction towards control τ values. Decreased levels of phosphorylated phospholamban (P-PLB) in hypoxia, but normalization by IL-18BP treatment suggest a role for IL-18 in regulation of calcium-handling proteins in hypoxia-induced diastolic dysfunction. In addition, MRI showed less increase in right ventricular (RV) wall thickness in IL-18BP-treated animals exposed to hypoxia, indicating an effect on RV hypertrophy.

CONCLUSION

Neutralization of IL-18 during alveolar hypoxia improves LV diastolic function and partly prevents RV hypertrophy.

SERCA2 activity is involved in the CNP-mediated functional responses in failing rat myocardium

BACKGROUND AND PURPOSES

Myocardial C-type natriuretic peptide (CNP) levels are increased in heart failure. CNP can induce negative inotropic (NIR) and positive lusitropic responses (LR) in normal hearts, but its effects in failing hearts are not known. We studied the mechanism of CNP-induced NIR and LR in failing hearts and determined whether sarcoplasmatic reticulum Ca(2+) ATPase2 (SERCA2) activity is essential for these responses.

EXPERIMENTAL APPROACH

Contractility, cGMP levels, Ca(2+) transient amplitudes and protein phosphorylation were measured in left ventricular muscle strips or ventricular cardiomyocytes from failing hearts of Wistar rats 6 weeks after myocardial infarction.

KEY RESULTS

CNP increased cGMP levels, evoked a NIR and LR in muscle strips, and caused phospholamban (PLB) Ser(16) and troponin I (TnI) Ser(23/24) phosphorylation in cardiomyocytes. Both the NIR and LR induced by CNP were reduced in the presence of a PKG blocker/cGMP analogue (Rp-8-Br-Pet-cGMPS) and the SERCA inhibitor thapsigargin. CNP increased the amplitude of the Ca(2+) transient and increased SERCA2 activity in cardiomyocytes. The CNP-elicited NIR and LR were not affected by the L-type Ca(2+) channel activator BAY-K8644, but were abolished in the presence of isoprenaline (induces maximal activation of cAMP pathway). This suggests that phosphorylation of PLB and TnI by CNP causes both a NIR and LR. The NIR to CNP in mouse heart was abolished 8 weeks after cardiomyocyte-specific inactivation of the SERCA2 gene.

CONCLUSIONS AND IMPLICATIONS

We conclude that CNP-induced PLB and TnI phosphorylation by PKG in concert mediate both a predictable LR as well as the less expected NIR in failing hearts.

The cardiokine secreted Frizzled-related protein 3, a modulator of Wnt signalling, in clinical and experimental heart failure

OBJECTIVES

Experimental studies have shown involvement of Wnt signalling in heart failure (HF). We hypothesized that secreted frizzled-related protein 3 (sFRP3), a modulator of Wnt signalling, is related to the progression of HF.

DESIGN

Circulating sFRP3 was measured in 153 HF patients and compared with 25 healthy controls. The association of sFRP3 with mortality was evaluated in 1202 patients (GISSI-HF trial). sFRP3 mRNA expression was assessed in failing human and murine left ventricles (LV), and cellular localization was determined after fractioning of myocardial tissue. In vitro studies were carried out in cardiac fibroblasts subjected to cyclic mechanical stretch.

RESULTS

(i) Heart failure patients had significantly raised serum sFRP3 levels compared with controls, (ii) during a median follow-up of 47 months, 315 patients died in the GISSI-HF substudy. In univariable Cox regression, tertiles of baseline sFRP3 concentration were significantly associated with all-cause and cardiovascular mortality. After adjustment for demographic and clinical variables, but not for CRP and NT-proBNP, the associations with mortality remained significant for the third tertile (all-cause, HR 1.45, P = 0.011; cardiovascular, HR 1.66, P = 0.003), (iii) sFRP3 mRNA expression was increased in failing human LV, with a decline following LV assist device therapy. LV from post-MI mice showed an increased sFRP3 mRNA level, particularly in cardiac fibroblasts, and (iv) mechanical stretch enhanced sFRP3 expression and release in myocardial fibroblasts.

CONCLUSION

There is an association between increased sFRP3 expression and adverse outcome in HF, suggesting that the failing myocardium itself contributes to an increase in circulating sFRP3.

Impaired left ventricular mechanical and energetic function in mice after cardiomyocyte-specific excision of Serca2

Sarco(endo)plasmic reticulum Ca2+ -ATPase (SERCA)2 transports Ca2+ from the cytosol into the sarcoplasmic reticulum of cardiomyocytes and is essential for maintaining myocardial Ca2+ handling and thus the mechanical function of the heart. SERCA2 is a major ATP consumer in excitation-contraction coupling but is regarded to contribute to energetically efficient Ca2+ handling in the cardiomyocyte. Previous studies using cardiomyocyte-specific SERCA2 knockout (KO) mice have demonstrated that decreased SERCA2 activity reduces the Ca2+ transient amplitude and induces compensatory Ca2+ transport mechanisms that may lead to more inefficient Ca2+ transport. In this study, we examined the relationship between left ventricular (LV) function and myocardial O2 consumption (MVo2) in ex vivo hearts from SERCA2 KO mice to directly measure how SERCA2 elimination influences mechanical and energetic features of the heart. Ex vivo hearts from SERCA2 KO hearts developed mechanical dysfunction at 4 wk and demonstrated virtually no working capacity at 7 wk. In accordance with the reported reduction in Ca2+ transient amplitude in cardiomyocytes from SERCA2 KO mice, work-independent MVo2 was decreased due to a reduced energy cost of excitation-contraction coupling. As these hearts also showed a marked impairment in the efficiency of chemomechanical energy transduction (contractile efficiency, i.e, work-dependent MVo2), hearts from SERCA2 KO mice were found to be mechanically inefficient. This ex vivo evaluation of mechanical and energetic function in hearts from SERCA2 KO mice brings together findings from previous experimental and mathematical modeling-based studies and demonstrates that reduced SERCA2 activity not only leads to mechanical dysfunction but also to energetic dysfunction.

Lack of pro-inflammatory cytokine mobilization predicts poor prognosis in patients with acute heart failure

AIMS

The aim of this study was to gain insight in the inflammatory response in acute heart failure (AHF) by assessing (1) plasma cytokine profiles and (2) prognostic value of circulating cytokines in AHF patients.

METHODS AND RESULTS

Plasma levels of 26 cytokines were quantified by multiplex protein arrays in 36 patients with congestive AHF, characterized by echocardiographic, radiologic, and clinical examinations on admission, during hospitalization and at discharge. Recurrent AHF leading to death or readmission constituted the combined end point, and all patients were followed for 120 days after discharge. Levels of 15 of the measured cytokines were higher in AHF than in healthy subjects (n=22) on admission. Low levels of MCP-1, IL-1β and a low IL-1β/IL-1ra ratio predicted fatal and non-fatal AHF within 120 days. Patients with low circulating levels of IL-1β had lower left ventricular ejection fraction and higher levels of N-terminal pro-B-type natriuretic peptide, while patients with low levels of MCP-1 had higher E/E' and inferior caval vein diameter, than patients with high levels.

CONCLUSION

Immune activation, reflected in increased cytokine levels, is present in AHF patients. Interestingly, failure to increase secretion of IL-1β and MCP-1 during AHF is associated with poor outcome.

SU-D-BRB-05: Small Animal Lung Compliance Imaging: Assessment System for Tissue Sensitivity to Radiation Induced Lung Injury

PURPOSE

Recent clinical trials and animal studies have indicated that the tissue sensitivity to radiation induced lung injury (RILI) may be region- specific. In this study, we propose a new 4D cone beam CT (CBCT) basedcompliance imaging method to measure regional pulmonary function change in precisely irradiated small animal under CBCT guidance on small animal radiation research platform (SARRP) to facilitate our understanding of region-specific tissue sensitivity to RILI.

METHODS

Four Sprague-Dawley rats underwent prospective pressure gated 4D CBCT on SARRP. Three animals were selected as control group which underwent a second 4D CBCT scan. The fourth animal was irradiated in the central lung (24 Gy) using 3 × 3 mm collimating cone 2 months prior to the scan. The specific compliance (Csp) was calculated via the real time pressure measurement from the ventilator and displacement field from 3D B-spline image registration between the end of inhale and end of exhale phases from the 4D CBCT scan. The 3D Csp maps from the control animal group were mapped to the irradiated animal as a Csp functional atlas for statistical analysis. We alsoevaluated the repeatability of the Csp measurement on a voxel-by-voxel basis.

RESULTS

No significant Csp difference is found after two month of radiation between the irradiated rat (0.22±0.05) and the functional atlas (0.21±0.07). The observation is consistent with previous publications. The averaged linear correlation coefficient between the voxel-by-voxel Csp measurements from initial and repeat scans in control group is 0.98.

CONCLUSIONS

We proposed a method that uses 4D CBCT based compliance imaging to measure region-specific tissue sensitivity of RILI. We compared the irradiated animal two months after radiation with the control group. Our study shows an excellent robustness of the proposed method for regional lung tissue specific compliance measurement. This work was supported in part by UVa George Amorino Pilot Grant.