Body‑Temperature Rise Unveils “Sarcomere Rhythm Homeostasis” (Scientific Reports, 2020)

Cardiac beating is ordinarily synchronized with intracellular Ca²⁺ signals, yet this study shows that simply warming the cells elicits an independent high‑frequency vibration. When neonatal rat cardiomyocytes are rapidly heated to 38–42 °C, each sarcomere not only exhibits the familiar Ca²⁺‑driven oscillation at ~ 1 Hz but also undergoes a hyperthermal sarcomeric oscillation (HSO) at ~ 7 Hz. Remarkably, this high‑frequency component is insensitive to Ca²⁺ concentration, and its period remains constant even though amplitude and contraction/extension times fluctuate greatly. The authors name this property Contraction Rhythm Homeostasis (CRH).

Left panel: Live‑cell image of GFP‑labeled Z‑lines whose lengths were tracked at 500 fps with 4 nm precision, together with the corresponding time‑series analysis.
Upper‑right graph: Two distinct frequency peaks (~ 7.6 Hz and ~ 1.4 Hz) that appear at 41 °C.
Middle power‑spectrum plot: Evidence that the high‑frequency HSO is amplitude‑modulated by the low‑frequency Ca²⁺ oscillation.
Lower schematic: A model of 40 half‑sarcomeres linked in series, incorporating stochastic forward/backward power strokes of myosin; simulations show that cooperative myosin binding “anchors” the period despite slow Ca²⁺ swings, while asynchronous shortening among half‑sarcomeres smooths excess tension and further stabilizes the cycle.