B. Murienne - Master Project Thesis - Infoscience - EPFL

Figure 22. Activation map for cardiomyocytes cultured on a new micropatterned silicone membrane.
The activation pattern shown in Figure 22 is the one expected. The cardiomyocytes are connected
all together, allowing the propagation of the activation from one side of the monolayer to the
other. The block present in the middle of the imaged area is due to a membrane defect, leading
the absence of cardiomyocytes or to a bad connection between them in this particular area.
Membranes with 10 + 5 + 5 µm microgrooves were thus used for all further experiments.
4.4 Cardiomyocyte pacing
In order to pace these confluent monolayers of cardiomyocytes, electrodes, shown in
Figure 23, and a pacing protocol, described in the Materials and methods section, were designed.
Pacing the cardiomyocytes at a defined frequency is of great importance to be able to compare the
results obtained from different monolayers. In fact, cell spontaneous beating rate varies from one
monolayer to the other and influences the shape of the action potentials and thus the APD and
repolarization values.
Figure 23. Pacing electrodes.
Figures 24 and 25 show the cardiomyocyte optical action potentials in black, as well as the pacing
stimulus in red from the same non-paced (top signal) and then paced (bottom signal) monolayer
area. In Figure 24, the cells were stimulated at a basic cycle length of 500 ms whereas in Figure
25, the cells were paced at a cycle length of 300 ms.
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