Clin Res Cardiol (2022). https://doi.org/10.1007/s00392-022-02002-5

Transplanted iPSC-derived cardiomyocytes actively contribute to left ventricular function.

T. Stüdemann1, J. Rössinger1, C. Manthey1, B. Geertz1, C. von Bibra1, R. Srikantharajah1, A. Shibamaya1, M. Köhne1, A. Wiehler2, J. S. Wiegert3, T. Eschenhagen1, F. Weinberger1

1Institut für Experimentelle Pharmakologie und Toxikologie, Universitätsklinikum Hamburg Eppendorf, Hamburg; 2Department of Psychiatry, Service Hospitalo-Universitaire, Groupe Hospitalier Universitaire Paris Psychiatrie & Neurosciences, Université de Paris, Paris, FR; 3Zentrum für Molekulare Neurobiologie Hamburg, Universitätsklinikum Hamburg Eppendorf, Hamburg;

Introduction Acute myocardial infarction (AMI) causes a substantial loss of myocardium that is replaced by non-contractile scar tissue. Modern therapy enables an increasing number of patients to survive the AMI. Yet, repeated ischemic events can lead to heart failure. Current pharmacotherapy supports the remaining myocardium but does not solve the underlying cause, the loss of cardiomyocytes. iPSC-cardiomyocyte transplantation aims to regenerate the heart and represents a novel therapeutic option that is evaluated in first clinical trials. However, the mechanism of action is not well understood. Here, we investigated whether transplanted cardiomyocytes actively contribute to heart function. Methods We aimed to address this question using an iPSC-cardiomyocyte line expressing iLMO4 as an optogenetic off-on switch. iLMO4 consists of Gaussia Luciferase M23 (GLucM23), improved chloride-conducting Channelrhodopsin (iChloC), and EYFP. Contractility can be switched off reversibly by photostimulation with 470 nm light. We conducted a guinea pig transplantation study (n=25). A cryoinjury of the left ventricular wall was induced and 20 x 106 iLMO4 (n=14) or wild type (WT; n=11) cardiomyocytes injected into the scar and surrounding area seven days after injury. Cardiac function was evaluated by echocardiography prior to and after cryoinjury. Four weeks after transplantation, a third echocardiography was performed. We then conducted photostimulation with 470 nm and 660 nm while assessing left ventricular pressure development in the ex vivo Langendorff-setting. Finally, the heart was perfused with Coelenterazine, the GLucM23 substrate, to measure cell viability and graft perfusion. Results Fractional area change (FAC) declined from 42±1 to 28±3% (WT) and 32±2% (iLMO4) after cryo injury but was stabilized by cell injection at 31±2% (WT) and 33±3% (iLMO4) four weeks after transplantation. Transplanted iLMO4 cardiomyocytes remuscularized 13±3% of the scar. iLMO4 cardiomyocytes, visualized by EYFP immunostaining, reached into the host myocardium, forming direct graft-host interactions via Connexin 43 and N-cadherin. Photostimulation with 470 nm light led to an instantaneous significant decline in left ventricular pressure in iLMO4 hearts (n=10; baseline: 60.4±3.8 mmHg; during photostimulation:  59.9±3.7 mmHg; ΔLVDP -0.5±0.3 mmHg; relative ΔLVDP between baseline and photostimulation: -0,8%). There was no decline in left ventricular function upon photostimulation after transplantation of WT cardiomyocytes. (n=5; baseline: 59.5±4.2 mmHg; during light application: 59.7±4.2 mmHg; ΔLVDP +0.4±0.1 mmHg; relative ΔLVDP between baseline and photostimulation: +0,8%). Moreover, 660 nm photostimulation did not cause a decline in left ventricular pressure, demonstrating that the effect was wavelength-specific. Left ventricular pressure recovered with slight delay (5 seconds) after the termination of photostimulation. Viable grafted cardiomyocytes were visible by bioluminescence signal in the left ventricular wall. Discussion Here, we provide evidence that transplanted iPSC-cardiomyocytes can actively contribute to left ventricular function, indicating that reconstitution of lost myocardium can serve as a conceptually new strategy to improve heart function.

https://dgk.org/kongress_programme/jt2022/aV1061.html