Science Topics – 171
In our previous work, we discovered that when cardiac muscle cells are heated to deep body temperature levels, the sarcomeres within the cells enter an oscillatory state of contraction and relaxation, a phenomenon we named "Hyperthermal Sarcomeric Oscillations" (HSOs). Subsequent detailed studies on the oscillatory characteristics of HSOs confirmed that the amplitude and phase of sarcomere vibrations change chaotically. In this study, we compared the wave properties of HSOs in primary cultured rat cardiac muscle cells under constant and varying calcium concentrations. We found that fluctuations in calcium concentration are a key factor causing chaotic instability in the amplitude and phase of sarcomere vibrations. We have named this phenomenon "S4C" (Sarcomere Chaos with Changes in Calcium Concentration). Interestingly, in HSOs affected by calcium concentration fluctuations, while S4C chaotically alters the amplitude and velocity of the vibrations, it maintains a consistent oscillation period. Concurrently, the sarcomere's vibration waveform changes in response to the calcium concentration variations. Thus, we discovered that the biological rhythm of changing calcium concentrations acting on autonomously oscillating sarcomere groups leads to the emergence of a biological characteristic of maintaining a consistent period while being acutely responsive to calcium concentration changes.
Observation of sarcomere chaos induced by changes in calcium concentration in cardiomyocytes., Seine A. Shintani, Biophysics and Physicobiology: 21(1), e210006, 2024.
＜Figure Legends＞
Characteristics of Various Oscillation Dynamics of Sarcomeres in Cardiomyocytes
(A) Time series data of sarcomere oscillations (Cell-SPOCs) when calcium concentration in cardiac myocytes is kept constant. SL1 and SL2 are adjacent sarcomeres.
(B) Lissajous figures of adjacent sarcomeres in A.
(C) Phase relationship between adjacent sarcomeres in A.
(D) Time series data of sarcomere oscillations (HSOs) when the calcium concentration in cardiac myocytes fluctuates due to spontaneous beating.
(E) Lissajous figures of adjacent sarcomeres in D.
(F) Phase relationship between adjacent sarcomeres in D.
(G) Time series changes in the variability of oscillation amplitude of individual sarcomeres in cardiac myocytes before and after heating to manifest HSOs. Heating is performed at the point of the red arrow. Before this point, only spontaneous beating (excitation-contraction coupling) occurs. After this point, the state includes spontaneous beating plus HSOs.
(H) Time series changes in the differences of similar trajectories in sarcomere dynamics during the relaxation phase of spontaneous beating. The vertical axis is logarithmic, and an exponential increase in trajectory differences is observed along the red linear line, indicating the nature of the differences spreading exponentially.
(I) Phase relationship between adjacent sarcomeres during spontaneous beating before heating in G.
Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University