Hyperthermal sarcomeric oscillations generated in warmed cardiomyocytes control amplitudes with chaotic properties while keeping cycles constant.

In a previous study, we reported that warming primary cultured cardiomyocytes to 38-42 °C puts the intracellular sarcomere into an oscillation state that repeatedly contracts and relaxes in a cycle close to the heartbeat. Interestingly, sarcomere during HSOs had contraction rhythm homeostasis that kept the oscillation cycle constant while changing the oscillation amplitude in response to changes in calcium concentration. We found in this study that sarcomere during HSOs chaotically fluctuates the oscillation amplitude. Sarcomere during HSOs flexibly changes the synchronization state, keeps the oscillation cycle constant, and changes the oscillation amplitude chaotically while changing in response to the change in calcium concentration. It is suggested that the dynamic synchronous state changes and chaotic properties between sarcomere contribute to the smooth change of the developmental tension of the sarcomere population, which depends on the cycle of calcium concentration change rather than the cycle of HSOs. This property is considered to be an important property for sarcomere, which contracts when the calcium concentration is high and then needs to be rapidly relaxed even if some calcium still remains.