Electrically communicating three‐dimensional cardiac tissue mimic fabricated by layered cultured cardiomyocyte sheets

Recent progress in stem cell biology is likely to provide implantable sources of human cardiomyocytes in the near future. This possibility has encouraged cardiac tissue engineering. To construct heart-like tissue, we have exploited the capabilities of novel cell culture surfaces grafted with a temperature-responsive polymer, poly(N-isopropylacrylamide) (PIPAAm), to produce intact viable monolayer cell sheets simply by reducing culture temperature. Cultured chick embryonic cardiomyocyte sheets detached from PIPAAm-grafted surfaces were layered into tissue-like laminate stacks using hydrophilic support and transfer membranes. The layered cell sheets rapidly adhered to each other, establishing cell-to-cell connections characteristic of heart tissue, including desmosomes and intercalated disks. Bilayer cell sheets pulsed spontaneously and synchronously, altering their characteristic pulsing frequency with applied electric stimulation transmitted across the sheets. These results demonstrate that electrically communicative three-dimensional cardiac constructs can be achieved by stacking monolayer cardiomyocyte sheets. Cardiac tissue engineering based on this technology will facilitate new in vitro heart models and may prove useful for in vivo cardiovascular tissue repair.