Fig. 1: ReWs promoted rapid beating of cells in SOTRs.

a Schematic describing SOTR formation. b Bright-field images of hiPSC-derived cardiomyocytes in the template. The red arrows indicate the edge of cardiac tissues in the template, and the dashed lines indicate the PDMS block and pillar boundaries, respectively. Pillar diameter = 3 mm. Scale bar represents 800 µm. c Quantification of the width of the SOTRs on the indicated culture day (mean ± s.d.; n = 4 biologically independent samples). **P < 0.001 (ANOVA). d Activation map of GCaMP3-positive SOTRs with zero, one, or two ReWs. The red arrows indicate the propagation direction of the action potential. e GCaMP3 fluorescence signal at a fixed position on the ring of SOTRs with zero, one, or two ReWs on day 6. f Beat rates of SOTRs at different culture times (mean ± s.d.; 2 ReWs: n = 10; 1 ReW: n = 12; 0 ReW: n = 8 biologically independent samples). *P < 0.05; **P < 0.001 (ANOVA). g The wave speed of spontaneous beating in SOTRs with zero, one, or two ReWs after 14 days of culture; for ReW groups, the speed was recorded after the ReWs are stopped and the spontaneous beating was recovered (mean ± s.d.; 2 ReWs: n = 4; 1 ReW: n = 4; 0 ReW: n = 6 biologically independent samples). *P < 0.05 (ANOVA). h The percentage of occurrence for different numbers of ReWs on days 6 (n = 204 biologically independent samples) and 14 (n = 186 biologically independent samples), respectively.