Abstract 153: Using the Embryonic Heart as an Instructive Template for Cardiac Tissue Engineering

The engineering of highly aligned cardiomyocytes into functional heart muscle remains a primary challenge in cardiac tissue engineering. Researchers have shown that micropatterned topography and chemistry as well as mechanical and electrical gradients are all effective at inducing some degree of alignment. However, which approach works best in terms of electromechanical function of the engineered cardiac muscle is still an active area of research. Because formation of new heart muscle in mammals primarily occurs during cardiogenesis, we asked whether the embryonic heart could be used as an instructive template for the design of more effective cardiac tissue engineering scaffolds. Specifically, we hypothesized that micropatterns of fibronectin based on fibronectin fibril size and architecture in embryonic myocardium could improve cardiomyocyte alignment relative to 20 μm wide, 20 μm spaced fibronectin lines, a control pattern used widely in the literature. To test this, we first imaged the fibronectin matrix in the ventricles of day-5 embryonic chick hearts and imaged this in 3D using a multiphoton microscope. This fibronectin structure was then converted into a photomask for photolithography and subsequent patterning of fibronectin onto cover slips using microcontact printing. Samples with the biomimetic patterns or control patterns were seeded with embryonic chick cardiomyocytes, cultured for 3 days and then stained and imaged to visualize the myofibrils. Image analysis to quantify alignment showed that the ability of the biomimetic pattern to induce cardiomyocyte alignment increased with cell density, suggesting that cell-cell interactions play an important role in the formation of aligned embryonic myocardium. Disruption of the cadherins junctions using blocking antibodies confirmed this conclusion. In the future we will use human induced pluripotent stem cell-derived cardiomyocytes to engineer more clinically-relevant human heart muscle and analyze electromechanical function of the tissues including contractile force and action potential propagation.