Electrical integration, maturation and proarrhythmic risk of induced pluripotent stem cell-derived cardiomyocytes after transplantation in infarcted mouse hearts

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State-of-the-art therapy of myocardial infarction does not result in regeneration of lost myocardium. Cell therapy using pluripotent stem cell-derived cardiomyocytes is regarded as promising strategy to overcome this hurdle. A potential arrhythmic risk is an important safety concern against cardiac cell therapy. Previous studies provided conflicting results on pro- or antiarrhythmic effects of transplantated cells of different origin, but did not include induced pluripotent stem cell-derived cardiomyocytes (iPSCM), which are regarded as one of the most promising cell types. The aim of this project is to investigate cell persistence, functional integration, maturation and arrhythmic potential of iPSCM after transplantation in infarcted mouse hearts. Murine iPSCM expressing enhanced green fluorescent protein and a puromycin resistance under control of the alpha-myosin heavy chain promoter will be injected into adult mouse hearts after induction of myocardial infarction by coronary artery ligation. iPSCM at different developmental stages will be compared regarding efficacy and safety. Another experimental group will be clusters of iPSCM and mesenchymal stem cells, since there is evidence of a higher persistence of the graft as compared with pure iPSCM. Saline will be injected in control animals. 6 days, 6 weeks and 3 months after transplantation, programmed stimulation will be applied by a right ventricular electrophysiological catheter. External ECG recordings will reveal number and duration of induced ventricular fibrillation episodes. Simultaneously, in vivo multi electrode array recordings of the left ventricle will be performed to display excitation spread. Afterwards, hearts will be resected and viable ventricular tissue slices (150 µm thick) will be prepared to enable in vitro multi electrode array measurements of field potentials as well as action potential recordings with glass microelectrodes in transplanted iPSCM and surrounding host cardiomyocytes. These experiments will provide information on electrical integration and maturation of transplanted cells. Preliminary experiments have already demonstrated the feasibility of the planned project.The expected results will reveal, if iPSCM are suitable for application in cardiac cell therapy based on their quality of electrical integration and arrhythmic potential. The four electrophysiological methods implemented in the project allow a direct correlation of single cell integration and maturation with the arrhythmic risk on tissue and organ levels, since all measurements are performed with the same preparations. This will enable a thorough evaluation of mechanisms of arrhythmogenesis, which will be an important step towards a higher efficacy and safety of cardiac cell therapy.