Feasibility of Long-Distance Transfer for High Resolution Optical Mapping of Cardiac Tissue Constructs

An increasing number of protocols are used to create engineered heart tissue (EHT) constructs, using different progenitors of cardiac cells with various scaffolds and bioreactors. Different laboratories develop their own EHT protocols, which are in most cases highly specialized and involve methods that do not transfer easily from one lab to another. Likewise, the imaging protocols used to evaluate the functional, structural and molecular properties of EHTs are also highly specialized and can involve equipment and methods that do not transfer well between the labs. As a result, it is often necessary to move EHTs between the location where they are engineered to locations where they are used for physiological testing or advanced imaging. In this work, we establish the feasibility of long-distance overnight shipping of EHTs grown in at Columbia University with electrical stimulation to George Washington University for high resolution optical mapping. The EHTs survived overnight shipping in sealed culture media flasks, as evidenced by robust synchronized contractions upon arrival at the destination institution. Calcium transients were readily recordable upon loading of the constructs with Fluo-4. Waves of electrical activity propagating throughout the constructs were imaged using high quantum efficiency back illuminated CCD camera. Due to perfusion limitations, cardiomyocyte-containing layers of EHT are usually restricted to 100-300 microns and the cell density is significantly lower than in intact myocardium. Therefore it was critical to show that the intensity and fidelity of the signals from EHTs stained with the potentiometric dye RH237 are sufficient to record wave propagation throughout the entire 7 mm-wide EHT with 50 micron spatial resolution. The data confirm the feasibility of collaborative arrangements between tissue engineering centers and other laboratories for high resolution fluorescence imaging.