Contractile Properties of Early Human Embryonic Stem Cell-Derived Cardiomyocytes: Beta-Adrenergic Stimulation Induces Positive Chronotropy and Lusitropy but Not Inotropy

Abstract

Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) provide the unique opportunity to study the very early development of the human heart. The aim of this study was to investigate the effect of calcium and beta-adrenergic stimulation on the contractile properties of early hESC-CMs. Beating clusters containing hESC-CMs were co-cultured in vitro with noncontractile slices of neonatal murine ventricles. After 5-7 days, when beating clusters had integrated morphologically into the damaged tissue, isometric force measurements were performed during spontaneous beating as well as during electrical field stimulation. Spontaneous beating stopped when extracellular calcium ([Ca²⁺](ec)) was removed or after administration of the Ca²⁺ channel blocker nifedipine. During field stimulation at a constant rate, the developed force increased with incremental concentrations of [Ca²⁺](ec). During spontaneous beating, rising [Ca²⁺](ec) increased beating rate and developed force up to a [Ca²⁺](ec) of 2.5 mM. When [Ca²⁺](ec) was increased further, spontaneous beating rate decreased, whereas the developed force continued to increase. The beta-adrenergic agonist isoproterenol induced a dose-dependent increase of the frequency of spontaneous beating; however, it did not significantly change the developed force during spontaneous contractions or during electrical stimulation at a constant rate. Force developed by early hESC-CMs depends on [Ca²⁺](ec) and on the L-type Ca²⁺ channel. The lack of an inotropic reaction despite a pronounced chronotropic response after beta-adrenergic stimulation most likely indicates immaturity of the sarcoplasmic reticulum. For cell-replacement strategies, further maturation of cardiac cells has to be achieved either in vitro before or in vivo after transplantation.

Identification of cardiovascular lineage descendants at single-cell resolution

“…Although ESC/iPSC-derived CMs may hold significant promise for cell-based therapy and as in vitro platforms for disease pathway and therapeutic drug discovery, their phenotype has been recognized as largely immature (Feinberg et al, 2013;Lieu et al, 2009;Liu et al, 2007;Martinez-Fernandez et al, 2013;Pillekamp et al, 2012;Robertson et al, 2013;Satin et al, 2008;Snir et al, 2003;Yang et al, 2014). Using our single-cell multiplex PCR expression analysis, we compared stage-by-stage the expression of main cardiac sarcomeric genes and transcription factors at distinct stages of development.…”

Ca2+ Channel Activators Reveal Differential L-Type Ca2+ Channel Pharmacology between Native and Stem Cell-Derived Cardiomyocytes

“…Calcium handling has also been reported to differ between stem cellderived cardiomyocytes and native ones. In particular, the force of contraction in response to ␤-adrenergic agonists is reduced in stem cell-derived myocytes (Xi et al, 2010;Pillekamp et al, 2012). Contractile responses to ␤-adrenergic stimulation require functional L-type Ca 2ϩ channels and sarcoplasmic reticulum, and it is believed that the latter is altered in stem cell-derived cardiomyocytes (Xi et al, 2010;Pillekamp et al, 2012).…”

Human pluripotent stem cell-derived cardiomyocyte based models for cardiotoxicity and drug discovery

“…Generating 3D micro ECTs of variable cell compositions, using human-derived cardiac cells, has been demonstrated as discussed. Moreover, varying degrees of hPSC-CM maturation have been demonstrated by means of prolonged culture [26], topographical cues [14], electrical stimulation [14], mechanical stretching [19], and/or chemical manipulation [27], as well as coculture with cardiac fibroblasts [28] and endothelial cells [25]. Yet, there are currently no robust methods of promoting the functional maturation of hPSC-CMs within a short time frame.…”