Fig. 3.

Quantifying contractility in engineered two-dimensional cardiac myocytes and tissues. A: micropillar substrates can be used to quantify contractile forces generated by cardiac myocytes. In this example, Ca²⁺ transients were also measured in engineered tissues on micropillar substrates. hESC-CM, human embryonic stem cell-derived cardiomyocytes. FEM, finite-element modeling. B–D: traction force microscopy and microcontact-printed polyacrylamide hydrogels have been implemented to quantify the combined effects of extracellular matrix elasticity and cell/tissue architecture on peak systolic traction stress generated by single cardiac myocytes (B), cardiac myocyte pairs (C), and multicellular cardiac tissues (D). Scale bars = 10 μm. In B, white denotes α-actinin. In C, red denotes actin, green denotes β-catenin, and blue denotes nuclei. In D, red denotes α-actinin, green denotes actin, and blue denotes nuclei. E: muscular thin film assay entails culturing cardiac myocytes on precut polymer cantilevers (shown here, micromolded gelatin hydrogels), which are released from the substrate at the time of analysis. Stress is calculated based on cantilever deflection. Images were adapted from Ref. 62 with permission from the American Chemical Society (A), Ref. 119 (B), Ref. 118 with permission from the National Academy of Sciences (C), Ref. 11 with permission from the Royal Society of Chemistry (D), and Ref. 116 with permission from Elsevier (E).