ESC Working Group on Myocardial Function Position Paper: how to study the right ventricle in experimental models

The right ventricle has become an increasing focus in cardiovascular research. In this position paper, we give a brief overview of the specific pathophysiological features of the right ventricle, with particular emphasis on functional and molecular modifications as well as therapeutic strategies in chronic overload, highlighting the differences from the left ventricle. Importantly, we put together recommendations on promising topics of research in the field, experimental study design, and functional evaluation of the right ventricle in experimental models, from non-invasive methodologies to haemodynamic evaluation and ex vivo set-ups.

Phorbol ester, but not ischemic preconditioning, activates protein kinase D in the rat heart

The signal transduction pathways that mediate the cardioprotective effects of ischemic preconditioning remain unclear. Here we have determined the role of a novel kinase, protein kinase D (PKD), in mediating preconditioning in the rat heart. Isolated rat hearts (n=6/group) were subjected to either: (i) 36 min aerobic perfusion (control); (ii) 20 min aerobic perfusion plus 3 min no-flow ischemia, 3 min reperfusion, 5 min no-flow ischemia, 5 min reperfusion (ischemic preconditioning); (iii) 20 min aerobic perfusion plus 200 nmol/l phorbol 12-myristate 13-acetate (PMA) given as a substitute for ischemic preconditioning. The left ventricle then was excised, homogenized and PKD immunoprecipitated from the homogenate. Activity of the purified kinase was determined following bincubation with [γ32P]-ATP±syntide-2, a substrate for PKD. Significant PKD autophosphorylation and syntide-2 phosphorylation occurred in PMA-treated hearts, but not in control or preconditioned hearts. Additional studies confirmed that recovery of LVDP was greater and initiation of ischemic contracture and time-to-peak contracture were less, in ischemic preconditioned hearts compared with controls (P<0.05). Our results suggest that the early events that mediate ischemic preconditioning in the rat heart occur via a PKD-independent mechanism.

Probiotic administration attenuates myocardial hypertrophy and heart failure following myocardial infarction in the rat

Background—Probiotics are extensively used to promote gastrointestinal health and emerging evidence suggests that their beneficial properties can extend beyond the local environment of the gut. Here, we determined whether oral probiotic administration can alter the progression of post-infarction heart failure. Methods and Results—Rats were subjected to six weeks of sustained coronary artery occlusion and administered the probiotic Lactobacillus rhamnosus GR-1 or placebo in the drinking water ad libitum. Culture and 16s rRNA sequencing showed no evidence of GR-1 colonization or a significant shift in the composition of the cecal microbiome. However, animals administered GR-1 exhibited a significant attenuation of left ventricular hypertrophy based on tissue weight assessment as well as gene expression of atrial natriuretic peptide. Moreover, these animals demonstrated improved hemodynamic parameters reflecting both improved systolic and diastolic left ventricular function. Serial echocardiography revealed significantly improved left ventricular parameters throughout the six week follow-up period including a marked preservation of left ventricular ejection fraction as well as fractional shortening. Beneficial effects of GR-1 were still evident in those animals in which GR-1 was withdrawn at four weeks suggesting persistence of the GR-1 effects following cessation of therapy. Investigation of mechanisms showed a significant increase in the leptin to adiponectin plasma concentration ratio in rats subjected to coronary ligation which was abrogated by GR-1. Metabonomic analysis showed differences between sham control and coronary artery ligated hearts particularly with respect to preservation of myocardial taurine levels. Conclusions—The study suggests that probiotics offer promise as a potential therapy for the attenuation of heart failure.

ms1, a novel stress-responsive, muscle-specific gene that is up-regulated in the early stages of pressure overload-induced left ventricular hypertrophy

We have identified and characterised a cDNA encoding a novel gene, designated myocyte stress 1 (ms1), that is up-regulated within 1 h in the left ventricle following the application of pressure overload by aortic banding in the rat. The deduced ms1 protein of 317 amino acids contains several putative functional motifs, including a region that is evolutionarily conserved. Distribution analysis indicates that rat ms1 mRNA expression is predominantly expressed in striated muscle and progressively increases in the left ventricle from embryo to adulthood. These findings suggest that rust may be important in striated muscle biology and the development of pressure-induced left ventricular hypertrophy. (C) 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

Downregulation of cyclin-dependent kinase inhibitors p21 and p27 in pressure-overload hypertrophy

We postulated that the cyclin-dependent kinase inhibitors p21 and p27 could regulate the alterations in growth potential of cardiomyocytes during left ventricular hypertrophy (LVH). LVH was induced in adult rat hearts by aortic constriction (AC) and was monitored at days 0, 1, 3, 7, 14, 21, and 42 postoperation. Relative to sham-operated controls (SH), left ventricle (LV) weight-to-body weight ratio in AC increased progressively with time without significant differences in body weight or right ventricle weight-to-body weight ratio. Atrial natriuretic factor mRNA increased significantly in AC to 287% at day 42 compared with SH (P < 0.05), whereas p21 and p27 mRNA expression in AC rats decreased significantly by 58% (P < 0.03) and 40% (P < 0.05) at day 7, respectively. p21 and p27 protein expression decreased significantly from days 3 to 21 in AC versus SH, concomitant with LV adaptive growth. Immunocytochemistry showed p21 and p27 expression in cardiomyocyte nuclei. Thus downregulation of p21 and p27 may modulate the adaptive growth of cardiomyocytes during pressure overload-induced LVH.

Conditional transgenic expression of fibroblast growth factor 9 in the adult mouse heart reduces heart failure mortality after myocardial infarction

BACKGROUND: Fibroblast growth factor 9 (FGF9) is secreted from bone marrow cells, which have been shown to improve systolic function after myocardial infarction (MI) in a clinical trial. FGF9 promotes cardiac vascularization during embryonic development but is only weakly expressed in the adult heart. METHODS AND RESULTS: We used a tetracycline-responsive binary transgene system based on the α-myosin heavy chain promoter to test whether conditional expression of FGF9 in the adult myocardium supports adaptation after MI. In sham-operated mice, transgenic FGF9 stimulated left ventricular hypertrophy with microvessel expansion and preserved systolic and diastolic function. After coronary artery ligation, transgenic FGF9 enhanced hypertrophy of the noninfarcted left ventricular myocardium with increased microvessel density, reduced interstitial fibrosis, attenuated fetal gene expression, and improved systolic function. Heart failure mortality after MI was markedly reduced by transgenic FGF9, whereas rupture rates were not affected. Adenoviral FGF9 gene transfer after MI similarly promoted left ventricular hypertrophy with improved systolic function and reduced heart failure mortality. Mechanistically, FGF9 stimulated proliferation and network formation of endothelial cells but induced no direct hypertrophic effects in neonatal or adult rat cardiomyocytes in vitro. FGF9-stimulated endothelial cell supernatants, however, induced cardiomyocyte hypertrophy via paracrine release of bone morphogenetic protein 6. In accord with this observation, expression of bone morphogenetic protein 6 and phosphorylation of its downstream targets SMAD1/5 were increased in the myocardium of FGF9 transgenic mice. CONCLUSIONS: Conditional expression of FGF9 promotes myocardial vascularization and hypertrophy with enhanced systolic function and reduced heart failure mortality after MI. These observations suggest a previously unrecognized therapeutic potential for FGF9 after MI.

Targeting myocardial remodelling to develop novel therapies for heart failure: a position paper from the Working Group on Myocardial Function of the European Society of Cardiology

The failing heart is characterized by complex tissue remodelling involving increased cardiomyocyte death, and impairment of sarcomere function, metabolic activity, endothelial and vascular function, together with increased inflammation and interstitial fibrosis. For years, therapeutic approaches for heart failure (HF) relied on vasodilators and diuretics which relieve cardiac workload and HF symptoms. The introduction in the clinic of drugs interfering with beta-adrenergic and angiotensin signalling have ameliorated survival by interfering with the intimate mechanism of cardiac compensation. Current therapy, though, still has a limited capacity to restore muscle function fully, and the development of novel therapeutic targets is still an important medical need. Recent progress in understanding the molecular basis of myocardial dysfunction in HF is paving the way for development of new treatments capable of restoring muscle function and targeting specific pathological subsets of LV dysfunction. These include potentiating cardiomyocyte contractility, increasing cardiomyocyte survival and adaptive hypertrophy, increasing oxygen and nutrition supply by sustaining vessel formation, and reducing ventricular stiffness by favourable extracellular matrix remodelling. Here, we consider drugs such as omecamtiv mecarbil, nitroxyl donors, cyclosporin A, SERCA2a (sarcoplasmic/endoplasmic Ca(2 +) ATPase 2a), neuregulin, and bromocriptine, all of which are currently in clinical trials as potential HF therapies, and discuss novel molecular targets with potential therapeutic impact that are in the pre-clinical phases of investigation. Finally, we consider conceptual changes in basic science approaches to improve their translation into successful clinical applications.

Lymph heart in chick - somitic origin, development and embryonic oedema

The lymph heart is a sac-like structure on either side of avian tail. In some adult birds, it empties the lymph from the copulatory organ; however, during embryonic development, it is thought to circulate extra-embryonic lymph. Very little is known about the origin, innervation and the cellular changes it undergoes during development. Using immunohistochemistry and gene expression profiling we show that the musculature of the lymph heart is initially composed solely of striated skeletal muscle but later develops an additional layer composed of smooth myofibroblasts. Chick-quail fate-mapping demonstrates that the lymph heart originates from the hypaxial compartments of somites 34-41. The embryonic lymph heart is transiently innervated by somatic motoneurons with no autonomic input. In comparison to body muscles, the lymph heart has different sensitivity to neuromuscular junction blockers (sensitive only to decamethonium). Furthermore, its abundant bungarotoxin-positive acetylcholinesterase receptors are unique as they completely lack specific acetylcholinesterase activity. Several lines of evidence suggest that the lymph heart may possess an intrinsic pacing mechanism. Finally, we assessed the function of the lymph heart during embryogenesis and demonstrate that it is responsible for preventing embryonic oedema in birds, a role previously thought to be played by body skeletal muscle contractions.

What is the function of nail biting: an analog assessment study

Objective: To compare the frequency of nail biting in 4 settings (interventions) designed to elicit the functions of nail biting and to compare the results with a self-report questionnaire about the functions of nail biting. Design: Randomised allocation of participants to order of conditions. Setting: University Psychology Department. Subjects: Forty undergraduates who reported biting their nails. Interventions: Left alone (boredom), solving maths problems (frustration), reprimanded for nail biting (contingent attention), continuous conversation (noncontingent attention). Main Outcome measures: Number of times the undergraduates bit their nails. Results: Nail biting occurred most often in two conditions, boredom and frustration. Conclusion: Nail biting in young adults occurs as a result of boredom or working on difficult problems, which may reflect a particular emotional state. It occurs least often when people are engaged in social interaction or when they are reprimanded for the behavior. (c) 2006 Elsevier Ltd. All rights reserved.

Hemispace differences in the visual perception of size in left hemi-Parkinson's disease

The visual perception of size in different regions of external space was studied in Parkinson's disease (PD). A group of patients with worse left-sided symptoms (LPD) was compared with a group with worse right-sided symptoms (RPD) and with a group of age-matched controls on judgements of the relative height or width of two rectangles presented in different regions of external space. The relevant dimension of one rectangle (the 'standard') was held constant, while that of the other (the 'variable') was varied in a method of constant stimuli. The point of subjective equality (PSE) of rectangle width or height was obtained by probit analysis as the mean of the resulting psychometric function. When the standard was in left space, the PSE of the LPD group occurred when the variable was smaller, and when the standard was in right space, when the variable was larger. Similarly, when the standard rectangle was presented in upper space, and the variable in lower space, the PSE occurred when the variable was smaller, an effect which was similar in both left and right spaces. In all these experiments, the PSEs for both the controls and the RPD group did not differ significantly, and were close to a physical match, and the slopes of the psychometric functions were steeper in the controls than the patients, though not significantly so. The data suggest that objects appear smaller in the left and upper visual spaces in LPD, probably because of right hemisphere impairment. (C) 2002 Elsevier Science Ltd. All rights reserved.

Numerical computation of an analytic singular value decomposition of a matrix valued function

This paper extends the singular value decomposition to a path of matricesE(t). An analytic singular value decomposition of a path of matricesE(t) is an analytic path of factorizationsE(t)=X(t)S(t)Y(t) T whereX(t) andY(t) are orthogonal andS(t) is diagonal. To maintain differentiability the diagonal entries ofS(t) are allowed to be either positive or negative and to appear in any order. This paper investigates existence and uniqueness of analytic SVD's and develops an algorithm for computing them. We show that a real analytic pathE(t) always admits a real analytic SVD, a full-rank, smooth pathE(t) with distinct singular values admits a smooth SVD. We derive a differential equation for the left factor, develop Euler-like and extrapolated Euler-like numerical methods for approximating an analytic SVD and prove that the Euler-like method converges.

Lipoma preferred partner is a mechanosensitive protein regulated by nitric oxide in the heart

Adaptor proteins play an important role in signaling pathways by providing a platform on which many other proteins can interact. Malfunction or mislocalization of these proteins may play a role in the development of disease. Lipoma preferred partner (LPP) is a nucleocytoplasmic shuttling adaptor protein. Previous work shows that LPP plays a role in the function of smooth muscle cells and in atherosclerosis. In this study we wanted to determine whether LPP has a role in the myocardium. LPP expression increased by 56% in hearts from pressure overload aortic-banded rats (p < 0.05 n = 4), but not after myocardial infarction, suggesting hemodynamic load regulates its expression. In vitro, LPP expression was 87% higher in cardiac fibroblasts than myocytes (p < 0.05 n = 3). LPP expression was downregulated in the absence of the actin cytoskeleton but not when microtubules were disassembled. We mechanically stretched cardiac fibroblasts using the Flexcell 4000 for 48 h (1 Hz, 5% maximum strain), which decreased total LPP total expression and membrane localization in subcellular fractions (p < 0.05, n = 5). However, L-NAME, an inhibitor of nitric oxide synthase (NOS), significantly upregulated LPP expression. These findings suggest that LPP is regulated by a complex interplay between NO and mechanical cues and may play a role in heart failure induced by increased hemodynamic load.

Characterisation of the intracellular-glutamate decarboxylase system (GAD): analysis of its function, transcription and role in the acid resistance of various strains of Listeria monocytogenes

The glutamate decarboxylase (GAD) system is important for the acid resistance of Listeria monocytogenes. We previously showed that under acidic conditions, glutamate (Glt)/γ-aminobutyrate (GABA) antiport is impaired in minimal media but not in rich ones, like brain heart infusion. Here we demonstrate that this behavior is more complex and it is subject to strain and medium variation. Despite the impaired Glt/GABA antiport, cells accumulate intracellular GABA (GABA(i)) as a standard response against acid in any medium, and this occurs in all strains tested. Since these systems can occur independently of one another, we refer to them as the extracellular (GAD(e)) and intracellular (GAD(i)) systems. We show here that GAD(i) contributes to acid resistance since in a ΔgadD1D2 mutant, reduced GABA(i) accumulation coincided with a 3.2-log-unit reduction in survival at pH 3.0 compared to that of wild-type strain LO28. Among 20 different strains, the GAD(i) system was found to remove 23.11% ± 18.87% of the protons removed by the overall GAD system. Furthermore, the GAD(i) system is activated at milder pH values (4.5 to 5.0) than the GAD(e) system (pH 4.0 to 4.5), suggesting that GAD(i) is the more responsive of the two and the first line of defense against acid. Through functional genomics, we found a major role for GadD2 in the function of GAD(i), while that of GadD1 was minor. Furthermore, the transcription of the gad genes in three common reference strains (10403S, LO28, and EGD-e) during an acid challenge correlated well with their relative acid sensitivity. No transcriptional upregulation of the gadT2D2 operon, which is the most important component of the GAD system, was observed, while gadD3 transcription was the highest among all gad genes in all strains. In this study, we present a revised model for the function of the GAD system and highlight the important role of GAD(i) in the acid resistance of L. monocytogenes.

Intermittent antegrade cardioplegia: isolated heart preservation with the Asporto heart preservation device

Background—A major problem in procurement of donor hearts is the limited time a donor heart remains viable. After cardiectomy, ischemic hypoxia is the main cause of donor heart degradation. The global myocardial ischemia causes a cascade of oxygen radical formation that cumulates in an elevation in hydrogen ions (decrease in pH), irreversible cellular injury, and potential microvascular changes in perfusion. Objective—To determine the changes of prolonged storage times on donor heart microvasculature and the effects of intermittent antegrade perfusion. Materials and Methods—Using porcine hearts flushed with a Ribosol-based cardioplegic solution, we examined how storage time affects microvascular myocardial perfusion by using contrast-enhanced magnetic resonance imaging at a mean (SD) of 6.1 (0.6) hours (n=13) or 15.6 (0.6) hours (n=11) after cardiectomy. Finally, to determine if administration of cardioplegic solution affects pH and microvascular perfusion, isolated hearts (group 1, n=9) given a single antegrade dose, were compared with hearts (group 2, n=8) given intermittent antegrade cardioplegia (150 mL, every 30 min, 150 mL/min) by a heart preservation device. Khuri pH probes in left and right ventricular tissue continuously measured hydrogen ion levels, and perfusion intensity on magnetic resonance images was plotted against time. Results—Myocardial perfusion measured via magnetic resonance imaging at 6.1 hours was significantly greater than at 15.6 hours (67% vs 30%, P= .00008). In group 1 hearts, the mean (SD) for pH at the end of 6 hours decreased to 6.2 (0.2). In group 2, hearts that received intermittent antegrade cardioplegia, pH at the end of 6 hours was higher at 6.7 (0.3) (P=.0005). Magnetic resonance imaging showed no significant differences between the 2 groups in contrast enhancement (group 1, 62%; group 2, 40%) or in the wet/dry weight ratio. Conclusion—Intermittent perfusion maintains a significantly higher myocardial pH than does a conventional single antegrade dose. This difference may translate into an improved quality of donor hearts procured for transplantation, allowing longer distance procurement, tissue matching, improved outcomes for transplant recipients, and ideally a decrease in transplant-related costs.

Separating heart and brain: on the reduction of physiological noise from multichannel functional near-infrared spectroscopy (fNIRS) signals

Objective. Functional near-infrared spectroscopy (fNIRS) is an emerging technique for the in vivo assessment of functional activity of the cerebral cortex as well as in the field of brain–computer interface (BCI) research. A common challenge for the utilization of fNIRS in these areas is a stable and reliable investigation of the spatio-temporal hemodynamic patterns. However, the recorded patterns may be influenced and superimposed by signals generated from physiological processes, resulting in an inaccurate estimation of the cortical activity. Up to now only a few studies have investigated these influences, and still less has been attempted to remove/reduce these influences. The present study aims to gain insights into the reduction of physiological rhythms in hemodynamic signals (oxygenated hemoglobin (oxy-Hb), deoxygenated hemoglobin (deoxy-Hb)). Approach. We introduce the use of three different signal processing approaches (spatial filtering, a common average reference (CAR) method; independent component analysis (ICA); and transfer function (TF) models) to reduce the influence of respiratory and blood pressure (BP) rhythms on the hemodynamic responses. Main results. All approaches produce large reductions in BP and respiration influences on the oxy-Hb signals and, therefore, improve the contrast-to-noise ratio (CNR). In contrast, for deoxy-Hb signals CAR and ICA did not improve the CNR. However, for the TF approach, a CNR-improvement in deoxy-Hb can also be found. Significance. The present study investigates the application of different signal processing approaches to reduce the influences of physiological rhythms on the hemodynamic responses. In addition to the identification of the best signal processing method, we also show the importance of noise reduction in fNIRS data.