Publications by authors named "Matthew Amoni"

10 Publications

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Incomplete Assembly of the Dystrophin-Associated Protein Complex in 2D and 3D-Cultured Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

Front Cell Dev Biol 2021 4;9:737840. Epub 2021 Nov 4.

Laboratory of Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium.

Human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CM) are increasingly used to study genetic diseases on a human background. However, the lack of a fully mature adult cardiomyocyte phenotype of hiPSC-CM may be limiting the scope of these studies. Muscular dystrophies and concomitant cardiomyopathies result from mutations in genes encoding proteins of the dystrophin-associated protein complex (DAPC), which is a multi-protein membrane-spanning complex. We examined the expression of DAPC components in hiPSC-CM, which underwent maturation in 2D and 3D culture protocols. The results were compared with human adult cardiac tissue and isolated cardiomyocytes. We found that similarly to adult cardiomyocytes, hiPSC-CM express dystrophin, in line with previous studies on Duchenne's disease. β-dystroglycan was also expressed, but, contrary to findings in adult cardiomyocytes, none of the sarcoglycans nor α-dystroglycan were, despite the presence of their mRNA. In conclusion, despite the robust expression of dystrophin, the absence of several other DAPC protein components cautions for reliance on commonly used protocols for hiPSC-CM maturation for functional assessment of the complete DAPC.
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http://dx.doi.org/10.3389/fcell.2021.737840DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8599983PMC
November 2021

Ventricular Arrhythmias in Ischemic Cardiomyopathy-New Avenues for Mechanism-Guided Treatment.

Cells 2021 10 1;10(10). Epub 2021 Oct 1.

Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, 3000 Leuven, Belgium.

Ischemic heart disease is the most common cause of lethal ventricular arrhythmias and sudden cardiac death (SCD). In patients who are at high risk after myocardial infarction, implantable cardioverter defibrillators are the most effective treatment to reduce incidence of SCD and ablation therapy can be effective for ventricular arrhythmias with identifiable culprit lesions. Yet, these approaches are not always successful and come with a considerable cost, while pharmacological management is often poor and ineffective, and occasionally proarrhythmic. Advances in mechanistic insights of arrhythmias and technological innovation have led to improved interventional approaches that are being evaluated clinically, yet pharmacological advancement has remained behind. We review the mechanistic basis for current management and provide a perspective for gaining new insights that centre on the complex tissue architecture of the arrhythmogenic infarct and border zone with surviving cardiac myocytes as the source of triggers and central players in re-entry circuits. Identification of the arrhythmia critical sites and characterisation of the molecular signature unique to these sites can open avenues for targeted therapy and reduce off-target effects that have hampered systemic pharmacotherapy. Such advances are in line with precision medicine and a patient-tailored therapy.
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http://dx.doi.org/10.3390/cells10102629DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8534043PMC
October 2021

Cardioprotective effect of fingolimod against calcium paradox-induced myocardial injury in the isolated rat heart.

Can J Physiol Pharmacol 2021 Sep 24. Epub 2021 Sep 24.

University of Cape Town, Human Biology, 5.14 Anatomy Building, Observatory, Cape Town, South Africa, 7925;

Fingolimod (FTY720) inhibits Ca-permeable, Mg-sensitive channels called transient receptor potential melastatin 7 (TRPM7), but its effects on Ca paradox (CP)-induced myocardial damage have not been evaluated. We studied the effect of FTY720 on CP-induced myocardial damage, and used other TRPM7 channel inhibitors nordihydroguaiaretic acid (NDGA) and Mg to test if any effect of FTY720 was via TRPM7 inhibition. Langendorff-perfused Wistar rat hearts were treated with FTY720 or NDGA and subjected to a CP protocol consisting of Ca depletion followed by Ca repletion. Hearts of rats pre-treated with MgSO were also subjected to CP. Hemodynamic parameters were measured using an intraventricular balloon, and myocardial infarct size was quantified using triphenyltetrazolium chloride stain. TRPM7 proteins in ventricular tissue were detected using immunoblot analysis. FTY720, but not NDGA, decreased CP-induced infarct size. Both FTY720 and NDGA minimized the CP-induced elevation of left ventricular end-diastolic pressure, but only FTY720 ultimately improved ventricular developed pressure. Mg pre-treatment had effect neither on CP-induced infarct size, hemodynamic parameters during CP, nor the level TRPM7 protein expression in ventricular tissue. Overall, FTY720 attenuated CP-induced myocardial damage, with potential therapeutic implications on Ca-mediated cardiotoxicity. However, the cardioprotective mechanism of FTY720 seems to be unrelated to TRPM7 channel modulation.
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http://dx.doi.org/10.1139/cjpp-2021-0381DOI Listing
September 2021

Discrete sites of frequent premature ventricular complexes cluster within the infarct border zone and coincide with high frequency of delayed afterdepolarizations under adrenergic stimulation.

Heart Rhythm 2021 Nov 8;18(11):1976-1987. Epub 2021 Aug 8.

Experimental Cardiology, Department of Cardiovascular Sciences, KU Leuven, Leuven, Belgium; Division of Cardiology, University Hospitals Leuven, Leuven, Belgium. Electronic address:

Background: Sympathetic activation in ischemic heart disease can cause lethal arrhythmias. These often are preceded by premature ventricular complexes (PVCs), which at the cellular level could result from delayed afterdepolarizations.

Objective: The purpose of this study was to identify and map vulnerable areas for arrhythmia initiation after myocardial infarction (MI) and to explore the link between PVCs and cellular events.

Methods: Anterior-septal wall MI was induced by 120 minutes of coronary occlusion followed by reperfusion (27 MI and 16 sham pigs). After 4 weeks, EnSite™ electroanatomic mapping combined with imaging was performed to precisely locate PVC sites of origin and subsequently record monophasic action potentials. Cardiomyocytes were isolated from different regions to study regional cellular remodeling. Isoproterenol was used as a surrogate for adrenergic stimulation both in vivo and in cardiomyocytes.

Results: PVCs originated from the MI border zone (BZ) and occurred at discrete areas with clusters of PVCs within the BZ. At these sites, frequent delayed afterdepolarizations and occasional associated spontaneous action potentials translating to a PVC were present. Cardiomyocytes isolated from the MI BZ exhibited more spontaneous action potentials than cardiomyocytes from remote regions. Sensitivity to adrenergic stimulation was increased in MI, in vivo and in cardiomyocytes. In awake, freely moving MI animals, frequent PVCs, ventricular arrhythmia, and sudden cardiac death occurred spontaneously at moderately elevated heart rates.

Conclusion: Post-MI, arrhythmias initiate from discrete vulnerable areas within the BZ, where delayed afterdepolarizations, related to increased adrenergic response of BZ cardiomyocytes, can generate PVCs.
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http://dx.doi.org/10.1016/j.hrthm.2021.07.067DOI Listing
November 2021

Cx43 hemichannel microdomain signaling at the intercalated disc enhances cardiac excitability.

J Clin Invest 2021 04;131(7)

Physiology Group, Department of Basic and Applied Medical Sciences, Ghent University, Ghent, Belgium.

Cx43, a major cardiac connexin, forms precursor hemichannels that accrue at the intercalated disc to assemble as gap junctions. While gap junctions are crucial for electrical conduction in the heart, little is known about the potential roles of hemichannels. Recent evidence suggests that inhibiting Cx43 hemichannel opening with Gap19 has antiarrhythmic effects. Here, we used multiple electrophysiology, imaging, and super-resolution techniques to understand and define the conditions underlying Cx43 hemichannel activation in ventricular cardiomyocytes, their contribution to diastolic Ca2+ release from the sarcoplasmic reticulum, and their impact on electrical stability. We showed that Cx43 hemichannels were activated during diastolic Ca2+ release in single ventricular cardiomyocytes and cardiomyocyte cell pairs from mice and pigs. This activation involved Cx43 hemichannel Ca2+ entry and coupling to Ca2+ release microdomains at the intercalated disc, resulting in enhanced Ca2+ dynamics. Hemichannel opening furthermore contributed to delayed afterdepolarizations and triggered action potentials. In single cardiomyocytes, cardiomyocyte cell pairs, and arterially perfused tissue wedges from failing human hearts, increased hemichannel activity contributed to electrical instability compared with nonfailing rejected donor hearts. We conclude that microdomain coupling between Cx43 hemichannels and Ca2+ release is a potentially novel, targetable mechanism of cardiac arrhythmogenesis in heart failure.
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http://dx.doi.org/10.1172/JCI137752DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8011902PMC
April 2021

Altered adrenergic response in myocytes bordering a chronic myocardial infarction underlies in vivo triggered activity and repolarization instability.

J Physiol 2020 07 11;598(14):2875-2895. Epub 2020 Feb 11.

Experimental Cardiology, University of Leuven, Herestraat 49 box 911, Leuven, Belgium.

Key Points: Ventricular arrhythmias are a major complication after myocardial infarction (MI), associated with sympathetic activation. The structurally heterogeneous peri-infarct zone is a known substrate, but the functional role of the myocytes is less well known. Recordings of monophasic action potentials in vivo reveal that the peri-infarct zone is a source of delayed afterdepolarizations (DADs) and has a high beat-to-beat variability of repolarization (BVR) during adrenergic stimulation (isoproterenol, ISO). Myocytes isolated from the peri-infarct region have more DADs and spontaneous action potentials, with spontaneous Ca release, under ISO. These myocytes also have reduced repolarization reserve and increased BVR. Other properties of post-MI remodelling are present in both peri-infarct and remote myocytes. These data highlight the importance of altered myocyte adrenergic responses in the peri-infarct region as source and substrate of post-MI arrhythmias.

Abstract: Ventricular arrhythmias are a major early complication after myocardial infarction (MI). The heterogeneous peri-infarct zone forms a substrate for re-entry while arrhythmia initiation is often associated with sympathetic activation. We studied the mechanisms triggering these post-MI arrhythmias in vivo and their relation to regional myocyte remodelling. In pigs with chronic MI (6 weeks), in vivo monophasic action potentials were simultaneously recorded in the peri-infarct and remote regions during adrenergic stimulation with isoproterenol (isoprenaline; ISO). Sham animals served as controls. During infusion of ISO in vivo, the incidence of delayed afterdepolarizations (DADs) and beat-to-beat variability of repolarization (BVR) was higher in the peri-infarct than in the remote region. Myocytes isolated from the peri-infarct region, in comparison to myocytes from the remote region, had more DADs, associated with spontaneous Ca release, and a higher incidence of spontaneous action potentials (APs) when exposed to ISO (9.99 ± 4.2 vs. 0.16 ± 0.05 APs/min, p = 0.004); these were suppressed by CaMKII inhibition. Peri-infarct myocytes also had reduced repolarization reserve and increased BVR (26 ± 10 ms vs. 9 ± 7 ms, P < 0.001), correlating with DAD activity. In contrast to these regional distinctions under ISO, alterations in Ca handling at baseline and myocyte hypertrophy were present throughout the left ventricle (LV). Expression of some of the related genes was, however, different between the regions. In conclusion, altered myocyte adrenergic responses in the peri-infarct but not the remote region provide a source of triggered activity in vivo and of repolarization instability amplifying the substrate for re-entry. These findings stimulate further exploration of region-specific therapies targeting myocytes and autonomic modulation.
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http://dx.doi.org/10.1113/JP278839DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7496440PMC
July 2020

R-DECO: an open-source Matlab based graphical user interface for the detection and correction of R-peaks.

PeerJ Comput Sci 2019 21;5:e226. Epub 2019 Oct 21.

STADIUS Center for Dynamical Systems, Signal Processing and Data Analytics, Department of Electrical Engineering (ESAT), KU Leuven, Leuven, Belgium.

Many of the existing electrocardiogram (ECG) toolboxes focus on the derivation of heart rate variability features from RR-intervals. By doing so, they assume correct detection of the QRS-complexes. However, it is highly likely that not all detections are correct. Therefore, it is recommended to visualize the actual R-peak positions in the ECG signal and allow manual adaptations. In this paper we present R-DECO, an easy-to-use graphical user interface (GUI) for the detection and correction of R-peaks. Within R-DECO, the R-peaks are detected by using a detection algorithm which uses an envelope-based procedure. This procedure flattens the ECG and enhances the QRS-complexes. The algorithm obtained an overall sensitivity of 99.60% and positive predictive value of 99.69% on the MIT/BIH arrhythmia database. Additionally, R-DECO includes support for several input data formats for ECG signals, three basic filters, the possibility to load other R-peak locations and intuitive methods to correct ectopic, wrong, or missed heartbeats. All functionalities can be accessed via the GUI and the analysis results can be exported as Matlab or Excel files. The software is publicly available. Through its easy-to-use GUI, R-DECO allows both clinicians and researchers to use all functionalities, without previous knowledge.
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http://dx.doi.org/10.7717/peerj-cs.226DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7924703PMC
October 2019

Myofibroblast modulation of cardiac myocyte structure and function.

Sci Rep 2019 06 20;9(1):8879. Epub 2019 Jun 20.

Department of Cardiovascular Diseases, Division of Experimental Cardiology, KU Leuven, Campus Gasthuisberg O/N1 Box 704, Herestraat 49, Leuven, B-3000, Belgium.

After myocardial infarction, resident fibroblasts (Fb) differentiate towards myofibroblasts (MyoFb), generating the scar tissue and the interstitial fibrosis seen in the adjacent myocardium. Fb and MyoFb have the potential to interact with cardiac myocytes (CMs) but insight into the phenotype-specific role and mode of interaction is still incomplete. Our objectives are to further define the modulation of CMs by MyoFbs compared to Fbs, as well as the role of direct contact through gap junctions vs. soluble mediators, using Fbs and CMs from pig left ventricle. Fbs were treated to maintain an undifferentiated state (SD-208) or to attain full differentiation to MyoFb (TGF-β1). Fbs and MyoFbs were co-cultured with CMs, with the possibility of direct contact or separated by a Thincert membrane. Only in direct co-culture, both Fbs and MyoFbs were able to decrease CM viability after 2 days. Only MyoFbs induced significant distal spreading of CMs in both direct and indirect co-culture. MyoFbs, but not Fbs, readily made connections with CMs in direct co-culture and connexin 43 expression in MyoFb was higher than in Fb. When coupled to CMs, MyoFbs reduced the CM action potential duration and hyperpolarized the CM resting membrane potential. Uncoupling reversed these effects. In conclusion, MyoFbs, but not Fbs, alter the CM structural phenotype. MyoFbs, but not Fbs, are likely to electrically connect to CMs and thereby modulate the CM membrane potential. These data provide further support for an active role of MyoFbs in the arrhythmogenic substrate after cardiac remodelling.
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http://dx.doi.org/10.1038/s41598-019-45078-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6586929PMC
June 2019

Beneficial Effects of Magnesium Treatment on Heart Rate Variability and Cardiac Ventricular Function in Diabetic Rats.

J Cardiovasc Pharmacol Ther 2017 Mar 8;22(2):169-178. Epub 2016 Jul 8.

1 Department of Human Biology, University of Cape Town, Cape Town, South Africa.

Background: Diabetes mellitus induces life-threatening cardiovascular complications such as cardiac autonomic neuropathy and ventricular dysfunction and is associated with hypomagnesemia. In this study, we investigated the short-term effects of magnesium (Mg) treatment on streptozotocin (STZ)-induced diabetic cardiac complications.

Methods: Adult Wistar rats were treated once with STZ (50 mg/kg, intraperitoneally [ip]) or vehicle (citrate) and then daily for 7 days with MgSO (270 mg/kg, ip) or saline. On the eighth day, in vivo tail-pulse plethysmography was recorded for heart rate variability (HRV) analysis, and ex vivo Langendorff-based left ventricular (LV) pressure-volume parameters were measured using an intraventricular balloon. Measurements of plasma lipid and Mg levels as well as blood glucose and cardiac tissue Mg levels were also performed.

Results: Treatment with Mg prevented diabetes-induced alterations in the standard deviation of the averages of normal-to-normal (NN) intervals (SDANN), root mean square differences of successive NN intervals (RMSSD), heart rate, and low-frequency (LF) power-high-frequency (HF) power ratio. In addition, Mg restored orthostatic stress-induced changes in SDANN, RMSSD, and LF-HF ratio in diabetic rats. In isolated hearts, Mg reversed the diabetes-induced decrease in LV end-diastolic elastance and the right shift of end-diastolic equilibrium volume intercept, without altering LV-developed pressure or end-systolic elastance. However, Mg did not prevent the elevation in blood glucose, total cholesterol, and triglycerides or the decrease in high-density lipoprotein cholesterol in diabetes. Plasma- or cardiac tissue Mg was not different among the treatment groups.

Conclusion: These results suggest that Mg treatment may attenuate diabetes-induced reduction in HRV and improve LV diastolic distensibility, without preventing hyperglycemia and dyslipidemia. Thus, Mg may have a modulatory role in the early stages of diabetic cardiovascular complications.
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http://dx.doi.org/10.1177/1074248416653831DOI Listing
March 2017

Cardioprotective and Anti-arrhythmic Effects of Magnesium Pretreatment Against Ischaemia/Reperfusion Injury in Isoprenaline-Induced Hypertrophic Rat Heart.

Cardiovasc Toxicol 2017 01;17(1):49-57

Department of Human Biology, Faculty of Health Sciences, University of Cape Town, Observatory, Cape Town, 7925, South Africa.

The effects of magnesium (Mg) on ischaemic complications of pathological cardiac hypertrophy are unclear. In this study, we investigated effects of Mg pretreatment on ischaemia/reperfusion (I/R) injury in isoprenaline (ISO)-induced hypertrophic hearts. Wistar rats were treated for 7 days with different combinations of ISO (1.25 mg/kg) subcutaneously, MgSO (270 mg/kg) intraperitoneally, or vehicle (saline). On the eighth day, hearts were either subjected to regional I/R during Langendorff perfusion or histologically stained with haematoxylin and eosin and Masson's trichrome. Haemodynamic and electrocardiographic parameters were recorded using the PowerLab data-acquisition system. Infarcts were identified by triphenyltetrazolium chloride staining. Plasma Mg was measured using photometric assays. Mg pretreatment significantly decreased I/R-induced infarct size (p = 0.001) and the overall arrhythmia score (p < 0.001) of I/R-induced ventricular ectopics, ventricular tachycardia, and ventricular fibrillation in hypertrophic hearts, but not non-hypertrophied hearts. Mg also improved post-I/R left ventricular developed pressure in hypertrophic hearts. However, Mg did not reverse the ISO-induced myocyte thickening and interstitial fibrosis or increases in heart weight. Plasma Mg was not different among treatment groups. These results suggest that Mg pretreatment may protect against I/R-induced injury and malignant arrhythmias in hypertrophic hearts, possibly via mechanisms unrelated to long-lasting changes in plasma Mg or prevention of structural changes such as fibrosis.
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http://dx.doi.org/10.1007/s12012-015-9355-6DOI Listing
January 2017
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