title: Automated analysis of contractile force and Ca2+ transients in engineered heart tissue.
abstract: Contraction and relaxation are fundamental aspects of cardiomyocyte functional biology. They reflect the response of the contractile machinery to the systolic increase and diastolic decrease of the cytoplasmic Ca(2+) concentration. The analysis of contractile function and Ca(2+) transients is therefore important to discriminate between myofilament responsiveness and changes in Ca(2+) homeostasis. This article describes an automated technology to perform sequential analysis of contractile force and Ca(2+) transients in up to 11 strip-format, fibrin-based rat, mouse, and human fura-2-loaded engineered heart tissues (EHTs) under perfusion and electrical stimulation. Measurements in EHTs under increasing concentrations of extracellular Ca(2+) and responses to isoprenaline and carbachol demonstrate that EHTs recapitulate basic principles of heart tissue functional biology. Ca(2+) concentration-response curves in rat, mouse, and human EHTs indicated different maximal twitch forces (0.22, 0.05, and 0.08 mN in rat, mouse, and human, respectively; P < 0.001) and different sensitivity to external Ca(2+) (EC50: 0.15, 0.39, and 1.05 mM Ca(2+) in rat, mouse, and human, respectively; P < 0.001) in the three groups. In contrast, no difference in myofilament Ca(2+) sensitivity was detected between skinned rat and human EHTs, suggesting that the difference in sensitivity to external Ca(2+) concentration is due to changes in Ca(2+) handling proteins. Finally, this study confirms that fura-2 has Ca(2+) buffering effects and is thereby changing the force response to extracellular Ca(2+).
authors.affiliation: Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Martinistraße, Hamburg, Germany;
authors.forename: Andrea
authors.initials: A
authors.lastname: Stoehr
authors.forename: Christiane
authors.initials: C
authors.lastname: Neuber
authors.forename: Christina
authors.initials: C
authors.lastname: Baldauf
authors.forename: Ingra
authors.initials: I
authors.lastname: Vollert
authors.forename: Felix W
authors.initials: FW
authors.lastname: Friedrich
authors.forename: Frederik
authors.initials: F
authors.lastname: Flenner
authors.forename: Lucie
authors.initials: L
authors.lastname: Carrier
authors.forename: Alexandra
authors.initials: A
authors.lastname: Eder
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schaaf
authors.forename: Marc N
authors.initials: MN
authors.lastname: Hirt
authors.forename: Bülent
authors.initials: B
authors.lastname: Aksehirlioglu
authors.forename: Carl W
authors.initials: CW
authors.lastname: Tong
authors.forename: Alessandra
authors.initials: A
authors.lastname: Moretti
authors.forename: Thomas
authors.initials: T
authors.lastname: Eschenhagen
authors.forename: Arne
authors.initials: A
authors.lastname: Hansen
mesh_terms: D000818:Animals; D057205:Automation, Laboratory; D020013:Calcium Signaling; D002454:Cell Differentiation; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000166:cytology; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence / Q000295:instrumentation / Q000379:methods*; D009200:Myocardial Contraction; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D051381:Rats; D011917:Rats, Inbred Lew; D017208:Rats, Wistar; D023822:Tissue Engineering / Q000379:methods*
keywords: Ca2+ transient; cardiac tissue engineering; contractile analysis; hiPSC