Spatio-temporal dynamics of networks of heart cells in culture

Spontaneous activity of cultured rat ventricular heart cells is studied as a function of cell density and ambient temperature. Three complementary methods are used: calcium fluorescence microscopy (monitoring intracellular free Ca2+ concentrations), real-time motion detection and electrophysiology. Statistical features of beating activity in single cells, small groups of cells and large monolayered networks are characterized and compared. At relatively high temperatures, a gradual transition from stochastic activity at the level of a single cell to regular synchronized beating in large, dense networks is found. Lowering the temperature results in a gradual loss of synchronization and the emergence of spatio-temporal dynamics, expressed by bursts of activity and contractions on many length and time scales.