Biomechanical tests for studying contractility and viscoelastic properties of single cardiac muscle cells

The study of cardiac function is important issue in physiological and biological sciences and has relevant implications for clinical practice. The interpretation of the whole-heart experiments is complicated by multi-cellular interactions. This work is devoted to the development of biomechanical tests for studying force-length and passive viscoelastic properties of intact single cardiac muscle cells using a glue-free carbon fiber technique. The developed tests allow analyzing the passive force-length, total force-length and active force-length relations in a beating cardiomyocyte by applying the step stretch protocol. The protocols also can be used to investigate in detail the viscoelastic hysteresis applying sawtooth stretch and release commands on a resting cell. The tracking of viscoelastic hysteresis allows one to study not only changes in the passive tension amplitude, but also the delay between the micromanipulator movement and the cell response or energy dissipation specifying viscoelastic properties. Thus, the developed biomechanical tests are powerful research tools to study cardiac biomechanics at the cell level.