Ca2+ signaling in human induced pluripotent stem cell-derived cardiomyocytes (iPS-CM) from normal and catecholaminergic polymorphic ventricular tachycardia (CPVT)-afflicted subjects

• Published in: Cell calcium (Edinburgh) Vol. 54; no. 2; pp. 57 - 70
• Main Authors: Zhang, X.-H., Haviland, S., Wei, H., Šarić, T., Fatima, A., Hescheler, J., Cleemann, L., Morad, M.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.08.2013
• Subjects: adrenergic agonists; Adrenergic Agonists - pharmacology; Adult; adults; Advanced Basic Science; Caffeine - pharmacology; calcium; Calcium - metabolism; Calcium signaling; Calcium Signaling - physiology; cardiomyocytes; Catecholamines - metabolism; Cell Differentiation; Cell Line; Cells, Cultured; CICR gain; CPVT; Humans; In Vitro Techniques; induced pluripotent stem cells; mutants; Mutation in RyR2 gene; Myocytes, Cardiac - drug effects; Myocytes, Cardiac - metabolism; Myocytes, Cardiac - pathology; Patch-Clamp Techniques; phenotype; Pluripotent stem cells; Pluripotent Stem Cells - metabolism; Pluripotent Stem Cells - pathology; point mutation; Point Mutation - genetics; Ryanodine Receptor Calcium Release Channel - genetics; Ryanodine Receptor Calcium Release Channel - metabolism; ryanodine receptors; Tachycardia, Ventricular - metabolism; Tachycardia, Ventricular - pathology; Calcium signaling; CICR gain; CPVT; Pluripotent stem cells; Mutation in RyR2 gene
• ISSN: 0143-4160; 1532-1991; 1532-1991
• DOI: 10.1016/j.ceca.2013.04.004

Derivation of cardiomyocytes from induced pluripotent stem cells (iPS-CMs) allowed us to probe the Ca2+-signaling parameters of human iPS-CMs from healthy- and catecholaminergic polymorphic ventricular tachycardia (CPVT1)-afflicted individuals carrying a novel point mutation p.F2483I in ryanodine receptors (RyR2). iPS-CMs were dissociated on day 30–40 of differentiation and patch-clamped within 3–6 days. Calcium currents (ICa) averaged ∼8pA/pF in control and mutant iPS-CMs. ICa-induced Ca2+-transients in control and mutant cells had bell-shaped voltage-dependence similar to that of ICa, consistent with Ca2+-induced Ca2+-release (CICR) mechanism. The ratio of ICa-activated to caffeine-triggered Ca2+-transients was ∼0.3 in both cell types. Caffeine-induced Ca2+-transients generated significantly smaller Na+–Ca2+ exchanger current (INCX) in mutant cells, reflecting their smaller Ca2+-stores. The gain of CICR was voltage-dependent as in adult cardiomyocytes. Adrenergic agonists enhanced ICa, but differentially altered the CICR gain, diastolic Ca2+, and Ca2+-sparks in mutant cells. The mutant cells, when Ca2+-overloaded, showed longer and wandering Ca2+-sparks that activated adjoining release sites, had larger CICR gain at −30mV yet smaller Ca2+-stores. We conclude that control and mutant iPS-CMs express the adult cardiomyocyte Ca2+-signaling phenotype. RyR2 F2483I mutant myocytes have aberrant unitary Ca2+-signaling, smaller Ca2+-stores, higher CICR gains, and sensitized adrenergic regulation, consistent with functionally altered Ca2+-release profile of CPVT syndrome.