Transmural myocardial repair with engineered heart muscle in a rat model of heterotopic heart transplantation - A proof-of-concept study.

Engineered heart muscle (EHM) can be implanted epicardially to remuscularize the failing heart. In case of a severely scarred ventricle, excision of scar followed by transmural heart wall replacement may be a more desirable application. Accordingly, we tested the hypothesis that allograft (rat) and xenograft (human) EHM can also be administered as transmural heart wall replacement in a heterotopic, volume-loaded heart transplantation model. We first established a novel rat model model to test surgical transmural left heart wall repair. Subsequently and in continuation of our previous allograft studies, we tested outcome after implantation of contractile engineered heart muscle (EHM) and non-contractile engineered connective tissue (ECT) as well as engineered mesenchymal tissue (EMT) allografts as transmural heart wall replacement. Finally, proof-of-concept for the application of human EHM was obtained in an athymic nude rat model. Only in case of EHM implantation, remuscularization of the surgically created transmural defect was observed with palpable graft vascularization. Taken together, feasibility of transmural heart repair using bioengineered myocardial grafts could be demonstrated in a novel rat model of heterotopic heart transplantation.