Formation of cardiac fibers in Matrigel matrix

We report a simple in vitro model of cardiac tissue that mimics three-dimensional (3-D) environment and mechanical load conditions and, as such, may serve as a convenient method to study stem cell engraftment or address developmental questions such as cytoskeleton or inter-calated disk maturation. To create in vitro cardiac fibres we used Matrigel, a commercially available basement membrane preparation. A semisolid pillow from concentrated Matrigel was overlaid with a suspension of rat neonatal cardiomyocytes in a diluted Matrigel solution. This created an environment in which the multicellular fibres continuously contracted against a mechanical load. The described approach allows continuous structural and functional monitoring of 20-300-micron-thick cardiac fibres and provides easy access to epitopes for immunostaining purpose.