A novel small animal model of left ventricular tissue engineering.

Complex congenital cardiac anomalies involving ventricular hypoplasia require either staged palliative reconstruction, converting the circulatory system to a single ventricle based pump, or allogeneic transplantation. Tissue engineering offers the potential for complete reconstruction of these defects, but is limited by the inability to model myocardial tissue engineering in a small animal. Our goal was to develop a small animal model for ventricular tissue engineering using rat heterotopic heart transplantation. Donor hearts were explanted after cardioplegic arrest and the left ventricular volume was augmented by the implantation of a biodegradable engineered construct. The heart was then transplanted heterotopically into syngeneic recipients creating either a volume loaded, functioning left ventricle, or a non-functioning left ventricle. Some of the engineered constructs were seeded with multipotent bone marrow-derived mesenchymal progenitor cells before implantation. Animals were evaluated by echocardiography, morphology, histology, and immunohistochemistry after 1 month. A scaffolding constructed from polytetrafluoroethylene, polylactide mesh, and type I and IV collagen hydrogel resulted in minimal intracardiac inflammation without aneurysmal dilatation. Successful transplantation and differentiation of mesenchymal progenitor cells was accomplished using this scaffolding. No ventricular arrhythmias resulted from this surgical manipulation and echocardiography revealed both end systolic and diastolic volume augmentation with ventricular expansion. We have developed an in vivo model of ventricular tissue engineering using heterotopic heart transplantation. Future work will focus on construction of ventricular tissue around pre-fabricated vascular networks in order increase cellular engraftment for ventricular reconstruction.