Tissue engineering of functional cardiac muscle: molecular, structural, and electrophysiological studies

The primary aim of this study was to relate molecular and structural proper ties of in vitro reconstructed cardiac muscle with its electrophysiological function using an in vitro model system based on neonatal rat cardiac myoc ytes, three-dimensional polymeric scaffolds, and bioreactors. After 1 wk of cultivation, we found that engineered cardiac muscle contained a 120- to 1 60-mum-thick peripheral region with cardiac myocytes that were electrically connected through gap junctions and sustained macroscopically continuous i mpulse propagation over a distance of 5 mm. Molecular, structural, and elec trophysiological properties were found to be interrelated and depended on s pecific model system parameters such as the tissue culture substrate, biore actor, and culture medium. Native tissue and the best experimental group (e ngineered cardiac muscle cultivated using laminin-coated scaffolds, rotatin g bioreactors, and low-serum medium) were comparable with respect to the co nduction velocity of propagated electrical impulses and spatial distributio n of connexin43. Furthermore, the structural and electrophysiological prope rties of the engineered cardiac muscle, such as cellularity, conduction vel ocity, maximum signal amplitude, capture rate, and excitation threshold, we re significantly improved compared with our previous studies.