This paper explores, through both mathematical modeling and experimental data, how the passive elastic properties of myofibrils mediate mechanical information transfer between neighboring sarcomeres via the actomyosin motor system.
By incorporating two forms of lateral mechanical balance—
the inverse correlation between sarcomere length (SL) and lattice spacing (LS), and
tension continuity across Z‑discs—
the authors reproduced the propagation of spontaneous oscillatory contraction (SPOC), a phenomenon that conventional one‑dimensional models could not explain. Specifically, when one sarcomere relaxes and lengthens rapidly, its transverse contraction immediately increases the longitudinal load on the adjacent sarcomere, triggering probabilistic reverse power strokes of myosin.
Simulations using a chain of many half‑sarcomeres showed that adjusting passive elasticity could replicate both the SPOC waveforms observed in rabbit skeletal muscle and the high‑frequency vibrations (60–80 Hz) of asynchronous insect flight muscle. Strengthening passive lateral elasticity dramatically improved oscillation synchrony, suggesting that specific elastic proteins—such as titin, projectin, and flightin—may contribute to physiological function by “rigidifying” the lattice array.
In cardiac muscle, the same lateral mechanical communication may explain why rapid relaxation occurs before intracellular Ca²⁺ has fully declined. The findings therefore provide insights into diastolic dysfunction at high heart rates and into cardiomyopathies arising from mutations in elastic proteins.
Article information & citation
Takumi Washio, Seine A Shintani, Hideo Higuchi, Seiryo Sugiura, Toshiaki Hisada. Effect of myofibril passive elastic properties on the mechanical communication between motor proteins on adjacent sarcomeres. Scientific Reports 9, 9355 (2019).