Comparing the effects of chemical Ca2+ dyes and R-GECO on contractility and Ca2+ transients in adult and human iPSC cardiomyocytes

• DOI: 10.1016/j.yjmcc.2023.04.008
• Publication Date: 2023-04-29T19:55:17Z
• Authors: Paul Robinson; Alexander J. Sparrow; Yiangos Psaras; Violetta Steeples; Jillian N. Simon; Connor N. Broyles; Yu-Fen Chang; Frances A. Brook; Ying-Jie Wang; Andrew Blease; Xiaoyu Zhang; Yama A. Abassi; Michael A. Geeves; Christopher N. To...; Hugh Watkins; Charles Redwood; Matthew J. Daniels
• Keywords: 0303 health sciences; Swine; Guinea Pigs; Induced Pluripotent Stem Cells; Myocardial Contraction; Article; 3. Good health; Mice; 03 medical and health sciences; Animals; Humans; Calcium; Myocytes, Cardiac; Coloring Agents

We compared commonly used BAPTA-derived chemical Ca2+ dyes (fura2, Fluo-4, and Rhod-2) with a newer genetically encoded indicator (R-GECO) in single cell models of the heart. We assessed their performance and effects on cardiomyocyte contractility, determining fluorescent signal-to-noise ratios and sarcomere shortening in primary ventricular myocytes from adult mouse and guinea pig, and in human iPSC-derived cardiomyocytes. Chemical Ca2+ dyes displayed dose-dependent contractile impairment in all cell types, and we observed a negative correlation between contraction and fluorescence signal-to-noise ratio, particularly for fura2 and Fluo-4. R-GECO had no effect on sarcomere shortening. BAPTA-based dyes, but not R-GECO, inhibited in vitro acto-myosin ATPase activity. The presence of fura2 accentuated or diminished changes in contractility and Ca2+ handling caused by small molecule modulators of contractility and intracellular ionic homeostasis (mavacamten, levosimendan, and flecainide), but this was not observed when using R-GECO in adult guinea pig left ventricular cardiomyocytes. Ca2+ handling studies are necessary for cardiotoxicity assessments of small molecules intended for clinical use. Caution should be exercised when interpreting small molecule studies assessing contractile effects and Ca2+ transients derived from BAPTA-like chemical Ca2+ dyes in cellular assays, a common platform for cardiac toxicology testing and mechanistic investigation of cardiac disease physiology and treatment.