Figure 5.

Computational model. (A) Endogenous cardiac MFB currents were modeled by adjusting the current conductances in the Sachse et al. fibroblast model³⁴ to match the current–voltage relationship found by Salvarani et al.¹³ for TGF-β1-treated MFBs. The dashed lines show the contributions of individual currents. (B) The ChR2 channel model (g_ChR2, E_ChR2) from Williams et al.³³ was added to endogenous MFB currents (I_MFB in figure, I_MFB,endo in equations). MFBs were electrically connected (G_MFB-CM) to neonatal rat cardiomyocytes (CMs) as modeled by Korhonen et al.¹⁷ which were connected to each other (G_CM-CM) to form a 30-cell, 1.5 mm 1-D cable. MFBs were only connected to each other (G_MFB-MFB = G_CM-CM) in Supplementary Fig. 5, otherwise G_MFB-MFB = 0. Dashed lines show outer boundaries of CMs (red) and MFBs (green). Formulas for variables and values for parameters are listed in Supplementary Tables 2–4.