Embryonic Stem (ES) or induced Pluripotent Stem (iPS) cells are important sources for cardiomyocyte generation, targeted for regenerative therapies. Several in vitro protocols are currently utilized for their differentiation, but the value of cell-based approaches remains unclear. Here, we characterized a cardiovascular progenitor population derived during ES differentiation, after selection based on VE-cadherin promoter (Pvec) activity. ESCs were genetically modified with an episomal vector, allowing the expression of puromycin resistance gene, under Pvec activity. Puromycin-surviving cells displayed cardiac and endothelial progenitor cells characteristics. Expansion and self-renewal of this cardiac and endothelial dual-progenitor population (CEDP) were achieved by Wnt/β-catenin pathway activation. CEDPs express early cardiac developmental stage-specific markers but not markers of differentiated cardiomyocytes. Similarly, CEDPs express endothelial markers. However, CEDPs can undergo differentiation predominantly to cTnT+ (~47%) and VE-cadherin+ (~28%) cells. Transplantation of CEDPs in the left heart ventricle of adult rats showed that CEDPs-derived cells survive and differentiate in vivo for at least 14 days after transplantation. A novel, dual-progenitor population was isolated during ESCs differentiation, based on Pvec activity. This lineage can self-renew, permitting its maintenance as a source of cardiovascular progenitor cells and constitutes a useful source for regenerative approaches.

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Experimental studies indicate improved ventricular function after treatment with growth hormone (GH) post-myocardial infarction, but its effect on arrhythmogenesis is unknown. Here, we assessed the medium-term electrophysiologic remodeling after intra-myocardial GH administration in (n = 33) rats. GH was released from an alginate scaffold, injected around the ischemic myocardium after coronary ligation. Two weeks thereafter, ventricular tachyarrhythmias were induced by programmed electrical stimulation. Monophasic action potentials were recorded from the infarct border, coupled with evaluation of electrical conduction and repolarization from a multi-electrode array. The arrhythmia score was lower in GH-treated rats than in alginate-treated rats or controls. The shape and the duration of the action potential at the infarct border were preserved, and repolarization-dispersion was attenuated after GH; moreover, voltage rise was higher and activation delay was shorter. GH normalized also right ventricular parameters. Intra-myocardial GH preserved electrical conduction and repolarization-dispersion at the infarct border and decreased the incidence of induced tachyarrhythmias in rats post-ligation. The long-term antiarrhythmic potential of GH merits further study.

BackgroundCardiac repair strategies are being evaluated for myocardial infarctions, but the safety issues regarding their arrhythmogenic potential remain unresolved. By utilizing the in-vivo rat model, we have examined the medium-term electrophysiologic effects of a biomaterial scaffold that has been cellularized with spheroids of human adipose tissue, derived from mesenchymal stem cells and umbilical vein endothelial cells.MethodsMesenchymal stem cells, which exhibit adequate differentiation capacity, were co-cultured with umbilical vein endothelial cells and were seeded on an alginate based scaffold. After in-vitro characterization, the cellularized scaffold was implanted in (n=15) adult Wistar rats 15 min post ligation of the left coronary artery, with an equal number of animals serving as controls. Two weeks thereafter, monophasic action potentials were recorded and activation-mapping was performed with a multi-electrode array. An arrhythmia score for inducible ventricular tachyarrhythmias was calculated after programmed electrical stimulation.ResultsThe arrhythmia score was comparable between the treated animals and controls. No differences were detected in the local conduction at the infarct border and in the voltage rise in monophasic action potential recordings. Treatment did not affect the duration of local repolarization, but tended to enhance its dispersion.ConclusionsThe fabricated bi-culture cellularized scaffold displayed favorable properties after in-vitro characterization. Medium-term electrophysiologic assessment after implantation in the infarcted rat myocardium revealed low arrhythmogenic potential, but the long-term effects on repolarization dispersion will require further investigation.