Implantation of exogenous donor cells into the heart (cellular cardiomyoplasty) is an emerging methodology for the treatment of post-ischemic ventricular remodeling. While initial clinical implantations of autologous skeletal myoblasts and bone marrow cells have been promising, the intrinsic potential of these cells to affect electro-mechanical function of surrounding heart tissue has still not been elucidated. Therefore, the main goal of this proposal is to systematically study the ability of different donor cells (i.e. skeletal myoblasts and mesenchymal stem cells, as compared to control cardiac myofibroblasts) to propagate electro-mechanical activity through a host cardiac network in vitro. We hypothesize that: 1) propagation of electrical activity through donor cells depends on their type and stage of differentiation, as well as the presence of not only electrical but also mechanical junctions between the donor-donor and host-donor cell pairs, and 2) electro- mechanical propagation in the donor cell implant can be improved through upregulation of the intercellular communication by specific growth factors. To test these hypotheses we propose to study electrical conduction through donor cells using a geometrically simplified, reproducible one-dimensional setting, i.e. the micropatterned cardiomyocyte strands with inserts made of donor cells. The propagation of cell membrane potentials and intracellular calcium transients in donor cells will be optically mapped in the presence of various differentiation agents and growth factors. Obtained results will be correlated with those from immunohistochemical and molecular analyses. The findings from this proposal are expected to elucidate potential of different donor cells to functionally integrate in the heart. Eventually, the proposed experimental framework will allow us to perform high throughput in vitro analysis of the factors that can improve electromechanical propagation of different donor cells. The final aim is to aid in the development of efficient and safe cell-based approaches for the treatment of regional heart injury due to ischemia, infarction, or congenital defects. [unreadable] [unreadable] [unreadable]