Mechanical coupling of paired myocytes. (A and B) Representative heat maps indicating peak systolic displacement (A, i), traction stress (A, ii), and vinculin-positive (B, gray) adhesions (arrows) for pairs of mononucleated (DAPI, blue) myocytes. Bar, 10 µm. (C) Schematic diagram indicating force calculations for different locations within cell pairs (i). Representative contraction cycles for each cell within homogeneous (ii) and heterogeneous mES-CM (iii) or miPS-CM (iv) pairs. (D) Duration of the contraction cycle as a function of μtissue type. (E) Peak systolic force in different regions within cell pairs. (F) Percentage cell shortening across homogeneous and heterogeneous cell pairs. Results presented as mean ± SEM (n = 7, 12, 8, 7, and 7 for neonate-neonate, mES-mES, mES-neonate, miPS-miPS, and miPS-neonate, respectively). *, P < 0.05, statistically significant differences from the neonate-neonate case for cellular values; ^†, P < 0.05, statistically significant differences from the neonate-neonate case for junctional values.