In vitro tissue engineering of a cardiac graft using a degradable scaffold with an extracellular matrix–like topography

Cardiac tissue engineering has been proposed as a treatment to repair impaired hearts. Bioengineered cardiac grafts are created by combining autologous cell transplantation with a degradable scaffold as a temporary extracellular matrix. Here we present a system for engineered myocardium combining cultured cardiomyocytes and a novel biodegradable scaffold with a unique extracellular matrix–like topography. Cardiomyocytes were harvested from neonatal rats and cultured in vitro on biodegradable electrospun nanofibrous poly(ε-caprolactone) meshes. Between days 5 and 7, the meshes were overlaid to construct 3-dimensional cardiac grafts. On day 14 of in vitro culture, the engineered cardiac grafts were analyzed by means of histology, immunohistochemistry, and scanning electron microscopy. The cultured cardiomyocytes attached well to the meshes, and strong beating was observed throughout the experimental period. The average fiber diameter of the scaffold is about 250 nm, well below the size of an individual cardiomyocyte. Hence the number of cell-cell contacts is maximized. Constructs with up to 5 layers could be formed without any incidence of core ischemia. The individual layers adhered intimately. Morphologic and electrical communication between the layers was established, as verified by means of histology and immunohistochemistry. Synchronized beating was also observed. This report demonstrates the formation of thick cardiac grafts in vitro and the versatility of biodegradable electrospun meshes for cardiac tissue engineering. It is envisioned that cardiac grafts with clinically relevant dimensions can be created by using this approach and combining it with new technologies to induce vascularization.