Self-restoration of cardiac excitation rhythm by anti-arrhythmic ion channel gating.

Homeostatic regulation protects organisms against hazardous physiological changes. However, such regulation is limited in certain organs and associated biological processes. For example, the heart fails to self-restore its normal electrical activity once disturbed, as with sustained arrhythmias.

Optogenetics enables real-time spatiotemporal control over spiral wave dynamics in an excitable cardiac system.

Propagation of non-linear waves is key to the functioning of diverse biological systems. Such waves can organize into spirals, rotating around a core, whose properties determine the overall wave dynamics. Theoretically, manipulation of a spiral wave core should lead to full spatiotemporal control over its dynamics.

Cardiomyogenic differentiation of human adipose-derived mesenchymal stem cells transduced with Tbx20-encoding lentiviral vectors.

Ischemic heart disease often results in myocardial infarction and is the leading cause of mortality and morbidity worldwide. Improvement in the function of infarcted myocardium is a main purpose of cardiac regenerative medicine. One possible way to reach this goal is via stem cell therapy.

Optogenetic manipulation of anatomical re-entry by light-guided generation of a reversible local conduction block.

Aims: Anatomical re-entry is an important mechanism of ventricular tachycardia, characterized by circular electrical propagation in a fixed pathway. It's current investigative and therapeutic approaches are non-biological, rather unspecific (drugs), traumatizing (electrical shocks), or irreversible (ablation). Optogenetics is a new biological technique that allows reversible modulation of electrical function with unmatched spatiotemporal precision using light-gated ion channels.

TECRL, a new life-threatening inherited arrhythmia gene associated with overlapping clinical features of both LQTS and CPVT.

Genetic causes of many familial arrhythmia syndromes remain elusive. In this study, whole-exome sequencing (WES) was carried out on patients from three different families that presented with life-threatening arrhythmias and high risk of sudden cardiac death (SCD). Two French Canadian probands carried identical homozygous rare variant in TECRL gene (p.

Islands of spatially discordant APD alternans underlie arrhythmogenesis by promoting electrotonic dyssynchrony in models of fibrotic rat ventricular myocardium.

Fibrosis and altered gap junctional coupling are key features of ventricular remodelling and are associated with abnormal electrical impulse generation and propagation. Such abnormalities predispose to reentrant electrical activity in the heart. In the absence of tissue heterogeneity, high-frequency impulse generation can also induce dynamic electrical instabilities leading to reentrant arrhythmias.

Allosteric Modulation of Kv11.1 (hERG) Channels Protects Against Drug-Induced Ventricular Arrhythmias.

Background: Ventricular arrhythmias as a result of unintentional blockade of the Kv11.1 (hERG [human ether-à-go-go-related gene]) channel are a major safety concern in drug development. In past years, several highly prescribed drugs have been withdrawn for their ability to cause such proarrhythmia.

Optogenetic Engineering of Atrial Cardiomyocytes.

Optogenetics is emerging in the cardiology field as a new strategy to explore biological functions through the use of light-sensitive proteins and dedicated light sources. For example, this technology allows modification of the electrophysiological properties of cardiac muscle cells with superb spatiotemporal resolution and quantitative control. In this chapter, the optogenetic modification of atrial cardiomyocytes (aCMCs) from 2-day-old Wistar rats using lentiviral vector (LV) technology and the subsequent activation of the light-sensitive proteins (i.

Constitutively Active Acetylcholine-Dependent Potassium Current Increases Atrial Defibrillation Threshold by Favoring Post-Shock Re-Initiation.

Electrical cardioversion (ECV), a mainstay in atrial fibrillation (AF) treatment, is unsuccessful in up to 10-20% of patients. An important aspect of the remodeling process caused by AF is the constitutive activition of the atrium-specific acetylcholine-dependent potassium current (IK,ACh → IK,ACh-c), which is associated with ECV failure. This study investigated the role of IK,ACh-c in ECV failure and setting the atrial defibrillation threshold (aDFT) in optically mapped neonatal rat cardiomyocyte monolayers.

Forced fusion of human ventricular scar cells with cardiomyocytes suppresses arrhythmogenicity in a co-culture model.

Aims: Fibrosis increases arrhythmogenicity in myocardial tissue by causing structural and functional disruptions in the cardiac syncytium. Forced fusion of fibroblastic cells with adjacent cardiomyocytes may theoretically resolve these disruptions. Therefore, the electrophysiological effects of such electrical and structural integration of fibroblastic cells into a cardiac syncytium were studied.

Barriers in contribution of human mesenchymal stem cells to murine muscle regeneration.

Aim: To study regeneration of damaged human and murine muscle implants and the contribution of added xenogeneic mesenchymal stem cells (MSCs).

Methods: Minced human or mouse skeletal muscle tissues were implanted together with human or mouse MSCs subcutaneously on the back of non-obese diabetic/severe combined immunodeficient mice. The muscle tissues (both human and murine) were minced with scalpels into small pieces (< 1 mm(3)) and aliquoted in portions of 200 mm(3).

Human Placenta-Derived Multipotent Cells (hPDMCs) Modulate Cardiac Injury: From Bench to Small and Large Animal Myocardial Ischemia Studies.

Cardiovascular disease is the leading cause of death globally, and stem cell therapy remains one of the most promising strategies for regeneration or repair of the damaged heart. We report that human placenta-derived multipotent cells (hPDMCs) can modulate cardiac injury in small and large animal models of myocardial ischemia (MI) and elucidate the mechanisms involved. We found that hPDMCs can undergo in vitro cardiomyogenic differentiation when cocultured with mouse neonatal cardiomyocytes.

Light-induced termination of spiral wave arrhythmias by optogenetic engineering of atrial cardiomyocytes.

Aims: Atrial fibrillation (AF) is the most common cardiac arrhythmia and often involves reentrant electrical activation (e.g. spiral waves).

Development of a lentivirus vector-based assay for non-destructive monitoring of cell fusion activity.

Cell-to-cell fusion can be quantified by endowing acceptor and donor cells with latent reporter genes/proteins and activators of these genes/proteins, respectively. One way to accomplish this goal is by using a bipartite lentivirus vector (LV)-based cell fusion assay system in which the cellular fusion partners are transduced with a flippase-activatable Photinus pyralis luciferase (PpLuc) expression unit (acceptor cells) or with a recombinant gene encoding FLPeNLS+, a nuclear-targeted and molecularly evolved version of flippase (donor cells). Fusion of both cell populations will lead to the FLPe-dependent generation of a functional PpLuc gene.

Hematopoietic microRNA-126 protects against renal ischemia/reperfusion injury by promoting vascular integrity.

Ischemia/reperfusion injury (IRI) is a central phenomenon in kidney transplantation and AKI. Integrity of the renal peritubular capillary network is an important limiting factor in the recovery from IRI. MicroRNA-126 (miR-126) facilitates vascular regeneration by functioning as an angiomiR and by modulating mobilization of hematopoietic stem/progenitor cells.

Interaction between myofibroblasts and stem cells in the fibrotic heart: balancing between deterioration and regeneration.

Signalling between the various cell types in the heart has been investigated for decades. However, relatively little is known about the interplay between the cardiac fibroblasts and myofibroblasts, which help to maintain myocardial tissue structure and function, and resident cardiac or extracardiac stem cells involved in tissue homeostasis and repair. Much of our knowledge about these interactions is derived from experimental animal models, especially those of myocardial infarction and stem cell transplantation.

Insulin-like growth factor promotes cardiac lineage induction in vitro by selective expansion of early mesoderm.

A thorough understanding of the developmental signals that direct pluripotent stem cells (PSCs) toward a cardiac fate is essential for translational applications in disease modeling and therapy. We screened a panel of 44 cytokines/signaling molecules for their ability to enhance Nkx2.5(+) cardiac progenitor cell (CPC) formation during in vitro embryonic stem cell (ESC) differentiation.

Atrium-specific Kir3.x determines inducibility, dynamics, and termination of fibrillation by regulating restitution-driven alternans.

Background: Atrial fibrillation is the most common cardiac arrhythmia. Ventricular proarrhythmia hinders pharmacological atrial fibrillation treatment. Modulation of atrium-specific Kir3.

Generation of Helper Plasmids Encoding Mutant Adeno-associated Virus Type 2 Capsid Proteins with Increased Resistance against Proteasomal Degradation.

Objective(s): Adeno-associated virus type 2 (AAV2) vectors are widely used for both experimental and clinical gene therapy. A recent research has shown that the performance of these vectors can be greatly improved by substitution of specific surface-exposed tyrosine residues with phenylalanines. In this study, a fast and simple method is presented to generate AAV2 vector helper plasmids encoding capsid proteins with single, double or triple Y→F mutations.

Quaking, an RNA-binding protein, is a critical regulator of vascular smooth muscle cell phenotype.

Rationale: RNA-binding proteins are critical post-transcriptional regulators of RNA and can influence pre-mRNA splicing, RNA localization, and stability. The RNA-binding protein Quaking (QKI) is essential for embryonic blood vessel development. However, the role of QKI in the adult vasculature, and in particular in vascular smooth muscle cells (VSMCs), is currently unknown.

Engraftment patterns of human adult mesenchymal stem cells expose electrotonic and paracrine proarrhythmic mechanisms in myocardial cell cultures.

Background: After intramyocardial injection, mesenchymal stem cells (MSCs) may engraft and influence host myocardium. However, engraftment rate and pattern of distribution are difficult to control in vivo, hampering assessment of potential adverse effects. In this study, the role of the engraftment patterns of MSCs on arrhythmicity in controllable in vitro models is investigated.

Development of an AdEasy-based system to produce first- and second-generation adenoviral vectors with tropism for CAR- or CD46-positive cells.

Background: The AdEasy system has acquired preeminence amongst the various methods for producing first-generation, early region 1 (E1)-deleted human adenovirus (HAdV) vectors (AdVs) as a result of the fast and reproducible recovery of full-length AdV genomes via homologous recombination in Escherichia coli.

Methods: From the classical AdEasy system, a new production platform was derived to assemble first- and second-generation [i.e.

Brief report: Misinterpretation of coculture differentiation experiments by unintended labeling of cardiomyocytes through secondary transduction: delusions and solutions.

Cardiomyogenic differentiation of stem cells can be accomplished by coculture with cardiomyocytes (CMCs). To facilitate their identification, stem cells are often labeled through viral transduction with a fluorescent protein. A second marker to distinguish stem cell-derived CMCs from native CMCs is rarely used.