Continuum Based Bioelectrical Simulations using Structurally Realistic Gastrointestinal Pacemaker Cell Networks

Cellular and tissue level bioelectrical activity was simulated over structurally realistic 3D interstitial cell of Cajal (ICC) networks reconstructed from confocal images of a wild type (WT) mouse model with a normal ICC distribution and a Spry4 knockout (KO) mouse model with a mild ICC hyperplasia. First, the ICC pixels within the confocal images were segmented. Then, the segmented images were visually inspected and the 3D surface mesh of the ICC tissue network was created from the 90 slices spanning the myenteric plexus ICC network. After two additional concentric meshes (representing the non-ICC and tissue bath regions) surrounding the ICC region were added, a 3D tetrahedral volume mesh containing the three regions was reconstructed. The electrical propagation through the tissue network was simulated using the bidomain continuum model. The results showed that the ICC network of the WT mouse had a smaller volume than the KO mouse (0.008 vs 0.012 mm3). The simulated bioelectrical activity for both mice showed an isotropic propagation from the initial activation region. Mean velocities of 4.2±1.5 and 4.1±1.3 mm/s were reported for the WT and KO mice, respectively. The velocity in the x-direction was higher than the y-direction for the WT mouse with a percent difference of 14.8%. On the other hand, the velocity in the y-direction was higher for the KO mouse with a percent difference of 9.5%. For both cases, there was no propagation in the z-direction as all the solution points along the same z-depth were simultaneously activated.