Abstract 13862: Transplanted Human Embryonic Stem Cell Derived Cardiomyocytes Electromechanically Couple With Host Myocardium in a Guinea Pig Model
Preclinical studies previously showed that human embryonic stem cell derived cardiomyocytes (hESC-CM) can preserve contractile function following transplantation in animal infarct models. However, the mechanisms underlying the functional improvements are unknown, and there is no direct evidence that hESC-CM grafts integrate with host tissue and contract synchronously during systole. Using zinc finger nuclease technology, H7 hESCs were genetically modified to stably express the fluorescent Ca2+ intensity indicator GCaMP3. GCaMP3 consists of a GFP that has been circularly permuted so that the N and C termini are fused and new termini are made in the middle of the protein. Fused to one terminus is calmodulin and the other is a peptide, M13, that calmodulin binds to in the presence of calcium. After in vitro differentiation, hESC-CMs were transplanted into non-injured or cryoinjured guinea pig hearts. We used surface ECG recordings and intravital imaging of the epicardial GCaMP3 signal to determine the relationship between the host cardiac rhythm and graft activation, 2 weeks after transplantation. In the non-injured guinea pig heart, we recorded hESC-CM GCaMP3 signal reliably occurring in synchrony with the sinus rhythm, confirming a successful 1:1 coupling (n= 6 animals). Interestingly, during methacholine-induced atrioventricular block, the hESC-CM can act as an ectopic pacemaker imposing its intrinsic rhythm to the host. When injected in a cryoinjured heart, fluorescent GCaMP3 signals were still detected (n= 6 animals). However, only parts of the graft demonstrated 1:1 graft-host coupling. Other parts of the graft showed rhythmic GCaMP3 signals but at a pace significantly different from the host heart, suggesting that, in the absence of coupling with the host, human cardiomyocyte contract with their own automaticity. For the first time, we demonstrated that 1) hESC-CM can couple with host myocardium in vivo that in a guinea pig model and, 2) the human cardiomyocytes follow their own intrinsic rhythm when graft-host coupling is impaired. These data indicate that hESC-CM likely could couple with human cardiomyocytes in vivo, but structural barriers from the infarct may promote automatic activity.
- © 2011 by American Heart Association, Inc.