Stability of beating frequency in cardiac myocytes by their community effect measured by agarose microchamber chip

Development of reliable cell-based assay is important for high-speed, low cost drug screening. However, the conventional method using cells are still unstable and thus are still under trial to make reliable cell models showing the same extent of reliability as tissue/organ models. As heart is one of the most important organs for toxicology in drug screening, the properties of heart cells are examined and reported strenuously. For example, it has been reported that one beating cell can influence the rate of a neighbor with which it makes contact, and that a group of heart cells in culture, beating synchronously with a rapid rhythm, can act as pacemaker for a contiguous cell sheet from earlier tissue culture studies of cardiac myocyte cells [1]. Although these former results predicted that the importance of a rapidly beating region of tissue acts as pacemaker for a slower one and examined how the synchronization process of two isolated beating cardiac myocytes [2] and that the importance of the communication of each cells in the cell-network, the community size effect could not be measured successfully using the conventional cultivation method on the culture dish plate. As means of attaining the spatial arrangement of cardiac myocytes even during cultivation, we have developed a new single-cell based cultivation method and a system using agarose microstructures, based on 1064-nm photo-thermal etching [3-5]. Using this system, we measured the time course of synchronization process of adjacent two beating cardiac myocyte cells connected by 2-μm-width pathways, and found the synchronization of two cells occurred 90 min after their first physical contact [6,7].This paper reports the cell network size effect (community effect) for stabilizing their beating intervals using our on-chip single-cell-based cultivation assay with stepwise modification of micorcultivation chamber structures during cultivation.The schematic drawing of the on-chip single-cell-based cultivation assa