Developmental changes in spontaneous beating rhythm of cardiac myocytes cultured in vitro by molecular diffusion culture method

To understand the detailed mechanisms of arrhythmia and methods of its treatment, it is necessary to elucidate the mechanisms of formation and breakdown of cardiac beating at a microscopic level by using appropriate in vitro models of cardiac beating. We developed a method for medium‐exchange‐free culture of rat cardiac myocytes, and carried out long‐term recording of the electrical activity of cardiac myocytes from postnatal rats by means of a microelectrode array (MEA) and our new culture method. Figures 6(a) to 6(f) show a series of properties of spontaneous beating (mean beating interval, standard deviation, and coefficient of variation) of cardiac myocytes cultured by a conventional culture method with alternate‐day medium exchange [(a) to (c)] and the newly developed “molecular diffusion culture” method [(d) to (f)]. As shown in these figures, the difference in the beating property between individual cultures that is found in conventional cultures [(a) to (c)] is dramatically reduced in the molecular diffusion cultures [(d) to (f)]. These results also indicate that there is a transient period when the mean beating interval, the standard deviation, and the coefficient of variation all increase transiently before the formation of a stable rhythmic fast beat. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(7): 35–42, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/ecj.10244