Temperature dependence of synchronized beating of cultured neonatal rat heart-cell networks with increasing age measured by multi-electrode arrays

Abstract

Primary cultured cardiomyocytes are attracting interest as a screening base for new drugs. One promising approach for a steady supply of cells is to preserve cardiomyocytes at temperatures below physiological conditions. The aim of this study was to observe the change in activity of cultured heart-cell networks at temperatures lower than physiological conditions to investigate their appropriate preservation conditions. At various temperatures between 38°C and 22°C, we measured the synchronized beating properties of neonatal rat ventricle heart-cells cultured on multi-electrode arrays. Synchronized beating rates decreased with temperature, but this temperature dependence varied according to the length of the culture period. For the heart-cell networks in the earlier stages of culture (1-3 days in culture), the beating rate decreased as the inter-beat interval increased, maintaining a constant rhythm. The propagation velocity of the synchronized field potential was approximately 5.9 cm/s at physiological temperature and decreased weakly with temperature. Conversely, in the later stages of culture (approximately 1 week) the beating rate decreased with temperature as the variability in the inter-beat interval increased, especially below 30°C. The propagation velocity of the synchronized potential signal was approximately 18 cm/s at physiological temperature, which is three times larger than that in early stage. Then the propagation velocity drastically decreased with temperature down to similar range with that in early stage Therefore, we considered that the maturation of a heart-cell network stabilized the synchronized beating rhythm and increased its propagation velocity at physiological conditions, but simultaneously increased the temperature sensitivity of the beating properties of the network. These temperature dependences on the signal-propagation velocity is considered as the functional change of gap junctions during culture. Thus, a mature heart-cell network would be more difficult to preserve at lower temperatures.