Measuring Cardiomyocyte Contractility and Calcium Handling In Vitro

In vitro measurements of cardiomyocyte contractility and Ca2+ handling have been used as a platform for determining physiological consequence of various genetic manipulations and identifying potential therapeutic targets for the treatment of heart failure. The Myocyte Calcium and Contractility System (IonOptix) offers a simultaneous trace of sarcomere movements and changes of intracellular Ca2+ levels in a single cardiomyocyte. Herein, we describe a modified protocol for the isolation of adult cardiomyocytes from murine hearts and provide a step-by-step description on how to analyze cardiomyocyte Ca2+ transient and contractility data collected using the IonOptix system. In our modified protocol, we recommend a novel cannulation technique which simplifies this difficult method and leads to improved viability of isolated cardiomyocytes. In addition, a comprehensive analysis of intracellular Ca2+ handling, SR Ca2+ load, myofilament Ca2+ sensitivity, and cardiomyocyte contractility is described in order to provide important insights into myocardial mechanics.