Engineering highly-aligned three-dimensional (3D) cardiac constructs for enhanced myocardial infarction repair.

Native myocardium exhibits well-organized cellular orientations and highly vascularized architectures, which is important for tissue survival and synchronic contraction activities. Mimicking such structural organizations to engineer functional cardiac constructs is a promising approach to treat myocardial infarction<i>in vivo</i>. Here we propose a novel strategy to engineer highly-aligned three-dimensional (3D) cardiac constructs by co-culturing cardiomyocytes and rat aortic endothelial cells (RAECs) along with native extracellular matrix-derived fibrin within electrohydrodynamic-printed microfibrous architectures. Cell-laden fibrin with a relatively rapid gelation rate enables uniform cellular distribution in 3D and can re-organize to form multidirectionally aligned 3D cardiac bands with similar orientations to the printed microfibers. The resultant 3D cardiac constructs show enhanced cardiomyocyte-specific protein expression, synchronous contraction and low excitation threshold. The addition of RAECs significantly increases the width of cardiac bands and enhances their beating frequency. The engineered 3D cardiac constructs with layer-specific orientations were found to effectively reduce infracted area, enhance neovascularization and eventually realize functional repair of infarcted myocardium<i>in vivo</i>. This exploration provides a promising strategy to engineer 3D cardiac constructs with tissue-specific cellular orientations for the functional repair of infarcted myocardium.