Human Cardiac Fibroblast Number and Activation State Modulate Electromechanical Function of hiPSC-Cardiomyocytes in Engineered Myocardium

Figure 7

Contractile alternans appear independently of early or late-passage hCFs but have a higher force threshold in early-passage tissues. (a) Percent of tissues with alternans. (b) The onset of alternans was measured as the pacing frequency at which alternans amplitude reached ≥5% of the total force amplitude. (c) Pacing frequency of alternans onset plotted as a function of maximum capture rate (MCR; for (c) only). (d) Amplitude of alternans was measured during field stimulation of increasing frequency and represented as percentage of full-force contractile amplitude. (e) Example raw trace of Ca²⁺ amplitude by Rhod-2 fluorescence during 2 Hz stimulation. Red and blue markers denote local maxima and minima, respectively. (f) Alternans in Ca²⁺ amplitude as a function of pacing frequency. independent experiments; the number of tissues per measurement is indicated on respective bars. C: control cardiomyocyte-only tissues; p4: 5% p4 hCF-added tissues; p9: 5% p9 hCF-added tissues. and ; data are represented as .