ECIS based wounding and reorganization of cardiomyocytes and fibroblasts in co-cultures

The crosstalk of two major heart cell groups, cardiomyocytes and fibroblasts, relies on direct electromechanical cellular coupling as well as indirect mechanical signal transmission through the surrounding viscoelastic extracellular matrix. Upon injury of cardiac tissue, this communication becomes unbalanced: fibrosis is initiated leading to increased collagen deposition, accompanied by an activation of fibroblasts - the key players of fibrosis. They undergo a reorganization or partial transformation to myofibroblasts during this process, which precedes scar formation within the infarcted heart in vivo. Here, we induce wound formation in an in vitro system as a model for these fibrotic conditions: we assessed the dynamics of wound healing in co-cultures of fibroblasts and myocytes upon targeted wound initiation using Electric Cell Substrate Impedance Sensing (ECIS) under optical control. We discovered distinct wound closure dynamics for mono- and co-cultures of myocytes and fibroblasts and observed a cessation of the contractile behavior for recovering cardiomyocyte cultures. We furthermore identified a change of cellular impedance for recovering fibroblasts and the presence of α-SMA, suggesting a partial transformation into myofibroblasts. This was concomitant with a modulation of connectivity, cell-substrate dynamics and membrane capacitance of all wounded cell cultures. Qualitatively, connexin 43 observation confirmed the ECIS trend found for cell-cell connectivity. Finally, we were able to validate the ECIS based wounding approach against an ECIS based barrier assay - the so-called electric fence. In particular the cell-cell connectivity and thus cell layer integrity dominates the healing dynamics within the two intrinsically different assays.