Functional Properties of Human Embryonic Stem Cell–Derived Cardiomyocytes: Intracellular Ca2+ Handling and the Role of Sarcoplasmic Reticulum in the Contraction

Abstract

Since cardiac transplantation is limited by the small availability of donor organs, regeneration of the diseased myocardium by cell transplantation is an attractive therapeutic modality. To determine the compatibility of human embryonic stem cellderived cardiomyocytes (hESC-CMs) (7 to 55 days old) with the myocardium, we investigated their functional properties regarding intracellular Ca ] i transient and contraction, indicating that at this developmental stage, contraction depends on transsarcolemmal Ca 2؉ influx rather than on sarcoplasmic reticulum Ca 2؉ release. Third, in agreement with the notion that a voltage-dependent Ca 2؉ current is present in hESC-CMs and contributes to the mechanical function, verapamil completely blocked contraction. Fourth, whereas hESC-CMs expressed SERCA2 and NCX at levels comparable to those of the adult porcine myocardium, calsequestrin and phospholamban were not expressed. Our study shows for the first time that functional properties related to intracellular Ca 2؉ handling of hESC-CMs differ markedly from the adult myocardium, probably due to immature sarcoplasmic reticulum capacity. STEM CELLS 2006;24:236 -245

Calcium signaling in human pluripotent stem cells

“…While cells and tissues differentiated from PSCs have been widely used for calcium signaling studies, we found only a limited number of data about such signaling in pluripotent stem cells, and even these data are mainly from mouse cell studies. Calcium signals in hESC-derived cardiomyocytes and neural cell types have been measured in most cases by calcium sensitive dyes: for cardiomyocytes Fura-2/AM [25][26][27][28], Fluo-4/AM [29,30] or dsRed+ [27], while for neural cell types Fluo-3/AM [8,31] Fura-2/AM [8,32] or Oregon green 488 Bapta-1 AM [33] have been applied. In pluripotent cells the application of Fluo-3/AM (mESC- [34], hESC- [8]) or Fluo-4/AM (mESC- [35][36][37], and hESC [12]) has been reported.…”

Differentiation of Human Atrial Myocytes From Endothelial Progenitor Cell-Derived Induced Pluripotent Stem Cells

“…Finally the functional profiling has demonstrated that the Ca+ handling in PSC-CM shows an immature sarcoplasmic reticulum capacity (SR) to store and release calcium ions. Thus, calcium ions enter the cells through the sarcolemma instead of being released by the SR and, ultimately result in slower of excitation-contraction coupling than adult CM [293][294][295]. Early stages of iPSC-CM demonstrate a proliferation rate similar to embryonic or fetal cardiomyocytes which is markedly decreased from the pluripotent state [296][297].…”

Adhesion Proteins, Stem Cells, and Arrhythmogenesis

“…The contractions of ESC-derived myocytes depend on transsarcolemmal calcium influx rather than calcium-induced calcium release from the sarcoplasmic reticulum, which is an expectable outcome given their early developmental stage [89]. Lack of expression of such calcium-handling proteins, as phospholamban and calse-questrin [90], further attests to the immature capacity of the sarcoplasmic reticulum in the ESC. This observation is unsurprisingly similar to that of fetal excitation-contraction coupling; wherein intracellular calcium oscillations, rather than transmembrane ion currents, evoke small membrane depolarizations that have the ability to trigger L-type calcium channeldriven action potentials [91].…”