Fig. 4.

Myocyte beating with microstructures. (a) Myocytes near microstructures have higher spontaneous beating rates (33.0±1.4 BPM) than myocytes in gels without microstructures (16.4±1.1 BPM) (n=5 cultures, >10 samplings per culture). Following addition of 10 μM dobutamine (DOB), myocytes exhibit significant increases in beating rates with microstructures (68.8±2.6 BPM) and in gel alone (39.4±3.3 BPM). 10 mM 2,3-butanedione monoxime (BDM) arrests contraction in both groups. (b, c) Confocal line scans (positions shown in red) are captured for live myocytes, as identified by calcein AM (green) and Hoechst 34580 (blue) staining of cytoplasm and nuclei, respectively. (d, e) Myocytes in conditions with or without microstructure contact show differences in baseline beating rates. White arrowheads mark each recorded beat; note that green and blue signals are artificially overlapped with the collected grayscale channel to help represent cell dimensions. (f, g) Upon addition of DOB, each myocyte shows a similar increase in beating rate. (h, i) Contraction in the same cells is inhibited after switching to media with BDM