Figure 4.

Impact of chronic optical pacing (C-OP) on functional maturation of h-iPSC ECTs: (a) Representative patch clamp recording from a D14h-iPSC CM after ECT ChIEF transfection. Blue ticks indicate 470 nm light pulses. (b) Representative stress trace during acute optical pacing of a C-OP ECT. After 3 s of spontaneous beating, we began acute pacing with a 470 nm 3.5 Hz pulsed LED. (c) Mean intrinsic beat rate and maximal capture rate (MCR) for D14 control (n = 13), D14 C-OP (n = 15) and D28 (n = 2) ECTs. Intrinsic beat rate increased after C-OP and MCR increased after C-OP and prolonged culture to D28. (d) Mean RT50 AT 3 Hz acute electrical pacing decreased after C-OP and after prolonged culture to D28. (e) Stress-frequency curves showed a less negative relationship after C-OP or prolonged culture to D28. (f) Pacing rate dependent beat-to-beat hysteresis decreased after C-OP and was absent in D28 ECTs. (g) Mean active stress was similar in D14 control and C-OP ECTs and trended lower in D28 ECTs (p = 0.08 vs D14 control). (h) Mean normalized systolic energy at 3 Hz acute electrical pacing decreased after C-OP and further decreased by D28. Error bars show standard deviations. See (c) for color legend. Results in (c–h) obtained with 5 V acute electrical field pacing.

*p < 0.05, **p < 0.001 vs D14 control, †p < 0.05 vs D28.