A combined gene and cell therapy approach for restoration of conduction

BACKGROUND Abnormal conduction underlies both brady-arrhythmias and re-entrant tachyarrhythmias. However, no practical way exists for restoring or improving conduction in areas of conduction slowing or block. OBJECTIVE This study sought to test the feasibility of a novel strategy for conduction repair using genetically engineered cells designed to form biological conducting cables. METHODS An in vitro model of conduction block was established using spatially separated, spontaneously contracting, nonsynchronized human embryonic stem cell-derived cardiomyocytes clusters. Immunostaining, dye transfer, intracellular recordings, and multielectrode array (MEA) studies were performed to evaluate the ability of genetically engineered HEK293 cells, expressing the SCN5A-encoded Na+ channel, to couple with cultured cardiomyocytes and to synchronize their electrical activity. RESULTS Connexin-43 immunostaining and calcein dye-transfer experiments confirmed the formation of functional gap junctions between the engineered cells and neighboring cardiomyocytes. MEA and intracellular recordings were performed to assess the ability of the engineered cells to restore conduction in the co-cultures. Synchronization was defined by establishment of fixed local activation time differences between the cardiomyocytes clusters and convergence of their activation cycle lengths. Nontrans-fected control cells were able to induce synchronization between cardiomyocytes clusters separated by distances up to 300 mu m (n = 21). In contrast, the Na+ channel-expressing cells synchronized contractions between clusters separated by up to 1,050 mu m, the longest distance studied (n = 23). Finally, engineered cells expressing the voltage-sensitive K(v)1.3 potassium channel prevented synchronization at any distance. CONCLUSION Genetically engineered cells, transfected to express Na+ channels, can form biological conducting cables bridging and coupling spatially separated cardiomyocytes. This novel cell therapy approach might be useful for the development of therapeutic strategies for both brady-arrhythmias and tachyarrhythmias.