Cardiomyocyte Mechanical Properties Assessment

Mechanical properties of cardiomyocytes were assessed using the SoftEdge MyoCam system (IonOptix Corporation, Milton, MA, USA) as previously described [18 (link)]. In brief, cardiomyocytes were placed in a chamber equipped on platforms of an inverted microscope and incubated at 25°C with a buffer containing 131 mM NaCl, 4 mM KCl, 1 mM CaCl₂, 1 mM MgCl₂, 10 mM glucose, and 10 mM HEPES, at pH 7.4. The cells were stimulated with a suprathreshold voltage at a frequency of 0.5 Hz, for a 3 ms duration, which provokes muscle contractions (FHC Inc, Brunswick, NE, USA). The myocyte was visualized on a computer monitor using an IonOptix MyoCam camera. The corresponding SoftEdge software was applied to monitor the changes in cell length during shortening and re-lengthening. Cell shortening and re-lengthening were assessed using the following indices: peak shortening (PS), maximal velocities of cell shortening and re-lengthening (±dL/dt), time-to-PS (TPS), and time-to-90% re-lengthening (TR90).