Extracellular matrix formation after transplantation of human embryonic stem cell-derived cardiomyocytes

Transplantation of human embryonic stem cell-derived cardiomyocytes (hESC-CM) for cardiac regeneration is hampered by the formation of fibrotic tissue around the grafts, preventing electrophysiological coupling. Investigating this process, we found that: (1) beating hESC-CM in vitro are embedded in collagens, laminin and fibronectin, which they bind via appropriate integrins; (2) after transplantation into the mouse heart, hESC-CM continue to secrete collagen IV, XVIII and fibronectin; (3) integrin expression on hESC-CM largely matches the matrix type they encounter or secrete in vivo; (4) co-transplantation of hESC-derived endothelial cells and/or cardiac progenitors with hESC-CM results in the formation of functional capillaries; and (5) transplanted hESC-CM survive and mature in vivo for at least 24 weeks. These results form the basis of future developments aiming to reduce the adverse fibrotic reaction that currently complicates cell-based therapies for cardiac disease, and to provide an additional clue towards successful engraftment of cardiomyocytes by co-transplanting endothelial cells

Characterization of Multiple Ion Channels in Cultured Human Cardiac Fibroblasts

Background: Although fibroblast-to-myocyte electrical coupling is experimentally suggested, electrophysiology of cardiac fibroblasts is not as well established as contractile cardiac myocytes. The present study was therefore designed to characterize ion channels in cultured human cardiac fibroblasts. Methods and Findings: A whole-cell patch voltage clamp technique and RT-PCR were employed to determine ion channels expression and their molecular identities. We found that multiple ion channels were heterogeneously expressed in human cardiac fibroblasts. These include a big conductance Ca2+-activated K+ current (BKCa) in most (88%) human cardiac fibroblasts, a delayed rectifier K+ current (IKDR) and a transient outward K+ current (Ito) in a small population (15 and 14%, respectively) of cells, an inwardly-rectifying K+ current (IKir) in 24% of cells, and a chloride current (ICl) in 7% of cells under isotonic conditions. In addition, two types of voltage-gated Na+ currents (INa) with distinct properties were present in most (61%) human cardiac fibroblasts. One was a slowly inactivated current with a persistent component, sensitive to tetrodotoxin (TTX) inhibition (INa.TTX, IC50 = 7.8 nM), the other was a rapidly inactivated current, relatively resistant to TTX (INa.TTXR, IC50 = 1.8 μM). RT-PCR revealed the molecular identities (mRNAs) of these ion channels in human cardiac fibroblasts, including KCa.1.1 (responsible for BKCa), Kv1.5, Kv1.6 (responsible for IKDR), Kv4.2, Kv4.3 (responsible for Ito), Kir2.1, Kir2.3 (for IKir), Clnc3 (for ICl), NaV1.2, NaV1.3, NaV1.6, NaV1.7 (for INa.TTX), and NaV1.5 (for INa.TTXR). Conclusions: These results provide the first information that multiple ion channels are present in cultured human cardiac fibroblasts, and suggest the potential contribution of these ion channels to fibroblast-myocytes electrical coupling. © 2009 Li et al.published_or_final_versio

Electrophysiological and Structural Remodeling in Heart Failure Modulate Arrhythmogenesis. 1D Simulation Study

Background: Heart failure is a final common pathway or descriptor for various cardiac pathologies. It is associated with sudden cardiac death, which is frequently caused by ventricular arrhythmias. Electrophysiological remodeling, intercellular uncoupling, fibrosis and autonomic imbalance have been identified as major arrhythmogenic factors in heart failure etiology and progression. Objective: In this study we investigate in silico the role of electrophysiological and structural heart failure remodeling on the modulation of key elements of the arrhythmogenic substrate, i.e., electrophysiological gradients and abnormal impulse propagation. Methods: Two different mathematical models of the human ventricular action potential were used to formulate models of the failing ventricular myocyte. This provided the basis for simulations of the electrical activity within a transmural ventricular strand. Our main goal was to elucidate the roles of electrophysiological and structural remodeling in setting the stage for malignant life-threatening arrhythmias. Results: Simulation results illustrate how the presence of M cells and heterogeneous electrophysiological remodeling in the human failing ventricle modulate the dispersion of action potential duration and repolarization time. Specifically, selective heterogeneous remodeling of expression levels for the Na+ /Ca2+ exchanger and SERCA pump decrease these heterogeneities. In contrast, fibroblast proliferation and cellular uncoupling both strongly increase repolarization heterogeneities. Conduction velocity and the safety factor for conduction are also reduced by the progressive structural remodeling during heart failure. Conclusion: An extensive literature now establishes that in human ventricle, as heart failure progresses, gradients for repolarization are changed significantly by protein specific electrophysiological remodeling (either homogeneous or heterogeneous). Our simulations illustrate and provide new insights into this. Furthermore, enhanced fibrosis in failing hearts, as well as reduced intercellular coupling, combine to increase electrophysiological gradients and reduce electrical propagation. In combination these changes set the stage for arrhythmias.This work was partially supported by (i) the "VI Plan Nacional de Investigacion Cientifica, Desarrollo e Innovacion Tecnologica" from the Ministerio de Economia y Competitividad of Spain (grant number TIN2012-37546-C03-01) and the European Commission (European Regional Development Funds - ERDF - FEDER), (ii) the Direccion General de Politica Cientifica de la Generalitat Valenciana (grant number GV/2013/119), and (iii) Programa Prometeo (PROMETEO/2012/030) de la Conselleria d'Educacio Formacio I Ocupacio, Generalitat Valenciana. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Gómez García, JF.; Cardona, K.; Romero Pérez, L.; Ferrero De Loma-Osorio, JM.; Trénor Gomis, BA. (2014). Electrophysiological and Structural Remodeling in Heart Failure Modulate Arrhythmogenesis. 1D Simulation Study. PLoS ONE. 9(9). https://doi.org/10.1371/journal.pone.0106602S9

The effect of intravenous ferric carboxymaltose on red cell distribution width: a subanalysis of the FAIR-HF study

<p>Aims: Red cell distribution width (RDW), a measure of variability in red blood cell size, is a novel prognostic marker in chronic heart failure (CHF). Iron deficiency contributes to elevated RDW. In the FAIR-HF trial, i.v. ferric carboxymaltose (FCM) improved the 6 min walk test (6MWT) distance in iron-deficient CHF patients. We studied the effect of FCM on RDW and the relationship between RDW and 6MWT distance.</p> <p>Methods and results: In FAIR-HF, iron-deficient CHF patients were randomized to FCM or placebo in a 2:1 ratio. From the total cohort (n = 459), we included 415 patients in whom RDW values and 6MWT distance were available for baseline and at least one follow-up visit (after 4, 12, and 24 weeks). Baseline RDW was higher in anaemic (haemoglobin <12 g/dL) compared with non-anaemic patients [15.2% (14.0–16.8) vs. 14.2% (13.4–15.4), P < 0.0001, median (interquartile range)]. In multivariate analysis, RDW was significantly associated with transferrin saturation (P < 0.001) and C-reactive protein levels (P = 0.002). Treatment with FCM led to a biphasic response; RDW increased within 4 weeks (+0.54% absolute change from baseline, P = 0.01) but fell to values below the placebo group after 24 weeks (–1.0 %, P = 0.03). The 6MWT distance and RDW were inversely related at baseline (r = –0.30, P < 0.0001). In all patients, the increase in 6MWT distance after 24 weeks was significantly correlated with a decrease in RDW (r= –0.25, P < 0.0001), even after adjustment for changes in haemoglobin.</p> <p>Conclusions: Iron deficiency in CHF is associated with high RDW, even after adjustment for the presence of anaemia. Treatment with i.v. FCM in iron-deficient CHF patients decreases RDW.</p&gt

The effect of intravenous ferric carboxymaltose on red cell distribution width: a subanalysis of the FAIR-HF study

<p>Aims: Red cell distribution width (RDW), a measure of variability in red blood cell size, is a novel prognostic marker in chronic heart failure (CHF). Iron deficiency contributes to elevated RDW. In the FAIR-HF trial, i.v. ferric carboxymaltose (FCM) improved the 6 min walk test (6MWT) distance in iron-deficient CHF patients. We studied the effect of FCM on RDW and the relationship between RDW and 6MWT distance.</p> <p>Methods and results: In FAIR-HF, iron-deficient CHF patients were randomized to FCM or placebo in a 2:1 ratio. From the total cohort (n = 459), we included 415 patients in whom RDW values and 6MWT distance were available for baseline and at least one follow-up visit (after 4, 12, and 24 weeks). Baseline RDW was higher in anaemic (haemoglobin &#60;12 g/dL) compared with non-anaemic patients [15.2% (14.0–16.8) vs. 14.2% (13.4–15.4), P &#60; 0.0001, median (interquartile range)]. In multivariate analysis, RDW was significantly associated with transferrin saturation (P &#60; 0.001) and C-reactive protein levels (P = 0.002). Treatment with FCM led to a biphasic response; RDW increased within 4 weeks (+0.54% absolute change from baseline, P = 0.01) but fell to values below the placebo group after 24 weeks (–1.0 %, P = 0.03). The 6MWT distance and RDW were inversely related at baseline (r = –0.30, P &#60; 0.0001). In all patients, the increase in 6MWT distance after 24 weeks was significantly correlated with a decrease in RDW (r= –0.25, P &#60; 0.0001), even after adjustment for changes in haemoglobin.</p> <p>Conclusions: Iron deficiency in CHF is associated with high RDW, even after adjustment for the presence of anaemia. Treatment with i.v. FCM in iron-deficient CHF patients decreases RDW.</p

Intravenous ferric carboxymaltose in iron-deficient chronic heart failure patients with and without anaemia: a subanalysis of the FAIR-HF trial

Aims: Therapy with i.v. iron in patients with chronic heart failure (CHF) and iron deficiency (ID) improves symptoms, functional capacity, and quality of life. We sought to investigate whether these beneficial outcomes are independent of anaemia. Methods and results: FAIR-HF randomized 459 patients with CHF [NYHA class II or III, LVEF ≤40% (NYHA II) or ≤45% (NYHA III)] and ID to i.v. iron as ferric carboxymaltose (FCM) or placebo in a 2:1 ratio. We analysed the efficacy and safety according to the presence or absence of anaemia (haemoglobin ≤120 g/L) at baseline. Of 459 patients, 232 had anaemia at baseline (51%). The effect of FCM on the primary endpoints of self-reported Patient Global Assessment (PGA) and NYHA class at week 24 was similar in patients with and without anaemia [odds ratio (OR) for improvement, 2.48 vs. 2.60, P = 0.97 for PGA and 1.90 vs. 3.39, P = 0.51 for NYHA). Results were also similar for the secondary endpoints, including PGA and NYHA at weeks 4 and 12, 6 min walk test distance, Kansas City Cardiomyopathy Questionnaire overall score, and European Quality of Life-5 Dimensions Visual Analogue Scale at most time points. Regarding safety, no differences were noticed in the rates of death or first hospitalization between FCM and placebo both in anaemic and in non-anaemic patients. Conclusions: Treatment of ID with FCM in patients with CHF is equally efficacious and shows a similar favourable safety profile irrespective of anaemia. Iron status should be assessed in symptomatic CHF patients both with and without anaemia and treatment of ID should be considered

Mathematical simulations of sphingosine-1-phosphate actions on mammalian ventricular myofibroblasts and myocytes

Mathematical modeling has been used to explore the consequences of the actions of sphingosine-1-phosphate (S-1-P) within the ventricular myocardium. Electrophysiological data obtained from rabbit cultured myofibroblasts (Chilton et al. 2007) provided the basis for modifications of our model of electrotonic coupling between ventricular myocytes and fibroblasts (MacCannell et al. 2007). Specifically, an in silico fibroblast/myocyte hybrid model was modified to account for the electrophysiological properties that are characteristic of the myofibroblast (the wound healing phenotype of the fibroblast). In addition, equations describing an S-1-P-induced current that can be activated in the myofibroblast were added. \ud \ud The sets of simulations that constitute this paper demonstrate that S-1-P can cause a significant depolarization of the resting membrane potential in both the myofibroblast and myocyte. When the myocyte to fibroblast coupling ratio is 1:1, this concentration-dependent effect is due to ligand-gated current in the myofibroblast depolrizing the myocyte through heterotypic connexin-mediated intercellular junctions. In addition to changing the resting potential in the myocyte, the S-1-P induced current resulted in significant changes in action potential waveform.\ud \ud A second set of simulations was done for the purpose of exploring the effects of S-1-P on myocytes that have some of the main electrophysiological properties of those from the failing heart. In these computations, the ten Tusscher model of the human ventricular myocyte was modified by reducing parameters as follows: cell capacitance, inward rectifier K+ current, delayed-rectifier K+ currents (IKs and IKr), and transient outward K+ current. In combination, these changes (each of which is associated with heart failure), resulted in prolongation of action potential duration. Simulations of electrotonic coupling between this 'failing' myocyte and myofibroblasts demonstrated that the resting potential and APD in the failing myocyte is more susceptible to modulation by electrotonic influences from S-1-P-stimulated myofibroblasts when a 'failing' electrophysiological phenotype is mimicked.\ud \ud In summary, our simulations draw attention to important effects of S-1-P on the ventricular myocardium even when this paracrine substance actos only on the fibroblast cell population. These cell-specific S-1-P effects alter the myocyte action potential via electrotonic coupling with myocytes. It is apparent that myofibroblasts can have significant effects on myocyte action potentials; and these effects would be expected to be more pronounced in the presence of ligand-gated effects on the myofibroblast. The general setting that we have attempted to replicate with this first order model has some similarities to acute or sterile inflammation in the myocardium wherein S-1-P concentrations in the interstitium are relatively high

Genesis of Atrial Fibrillation Under Different Diffuse Fibrosis Density Related with Atmospheric Pollution. In-Silico Study

Atrial remodeling is a widely acknowledged process that accelerates the susceptibility to and progression of atrial fibrillation. An increasingly recognized structural component is atrial fibrosis. Recent studies have shown that air pollution increases the risk of heart arrhythmias, where the exposure to particulate matter (PM) contributes to the generation of myocardial fibrosis, increasing the cardiovascular risk. The density and patterns of fibrosis (interstitial, compact and diffuse) are relevant in abnormal conduction and vulnerability to cardiac arrhythmias. Taking into account that fibrosis has been widely reported as one of the consequences of PM exposure, in this work, we evaluated the effects of low and high diffuse fibrosis density on conduction velocity and arrhythmic propagation patterns. For this purpose, cellular models of atrial myocyte and fibroblast were implemented in a 3D model of the human atria. Low (6.25%) and high (25%) fibrosis densities were simulated in the left atrium and its effect on conduction velocity and fibrillatory dynamics was evaluated. Results showed a conduction velocity reduction of 71% associated with a high fibrosis density. At low fibrosis density, few reentries were observed. On the other hand, at high fibrosis density, irregular propagation patterns, characterized by multiple wavelets and rotors, were observed. Our results suggest that high diffuse fibrosis density is associated with a significant conduction velocity reduction and with chaotic propagation patterns during atrial fibrillation. © 2020, Springer Nature Switzerland AG