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Figure 7: Biomechanical testing of EMT. (a) EMTs were mounted on a customized mechanical testing station using monofilament nylon sutures at the points indicated by the yellow arrows. (b) Representative contractile force traces of EMT at 0, 5, 10, and 15% strain. (c) Active force-strain relations of culture day 14 MDSC-EMT and iPS-EMT at 0 to 0.15 strain. (d) Active force increased in response to increased strain (* , ** versus baseline, ANOVA). (d) Active force at maximal strain, (15%). (e) Force frequency relationship of EMT. Culture day 14 MDSC-EMT and iPS-EMT electrically field stimulated at rates of 1 to 5 Hz at 100 V and 5 ms duration. EMTs showed decreased active force at increasing pacing rates. (f) Contractile response of EMT to ISP. Culture day 14 MDSC-EMT (blue) and iPS-EMT (red) were treated with 1 μM ISP for 3 minutes and showed increased active force * versus pretreatment. (g) Contractile response of EMT to extracellular calcium. Culture day 14 MDSC-EMT (blue) and iPS-EMT (red) were treated with 2 mM CaCl2 for 3 minutes and showed increased active force. * versus pretreatment. ** versus pretreatment. (h) Representative train stimulation of MDSC-EMT and iPS-EMT.