Micropattern platform promotes extracellular matrix remodeling by human PSC‐derived cardiac fibroblasts and enhances contractility of co‐cultured cardiomyocytes

In native heart tissue, cardiac fibroblasts provide the structural framework of extracellular matrix (ECM) while also influencing the electrical and mechanical properties of cardiomyocytes. Recent advances in the field of stem cell differentiation have led to the availability of human pluripotent stem cell‐derived cardiac fibroblasts (iPSC‐CFs) in addition to cardiomyocytes (iPSC‐CMs). Here we use a novel 2D in vitro micropatterned platform that provides control over ECM geometry and substrate stiffness. When cultured alone on soft micropatterned substrates, iPSC‐CFs are confined to the micropatterned features and remodel the ECM into anisotropic fibers. Similar remodeling and ECM production occurs when cultured with iPSC‐CMs in a co‐culture model. In addition to modifications in the ECM, our results show that iPSC‐CFs influence iPSC‐CM function with accelerated Ca(2+) transient rise‐up time and greater contractile strains in the co‐culture conditions compared to when iPSC‐CMs are cultured alone. These combined observations highlight the important role cardiac fibroblasts play in vivo and the need for co‐culture models like the one presented here to provide more representative in vitro cardiac constructs.