Characteristics of calcium sparks in cardiomyocytes derived from embryonic stem cells.
In embryonic stem (ES) cell-derived cardiomyocytes, spontaneous Ca(2+) sparks representing Ca(2+) release through ryanodine receptor (RyR) channels were characterized and correlated to the expression of RyRs as well as the Ca(2+) load of the sarcoplasmic reticulum (SR). In very early developmental stage (VEDS) cardiac precursor cells, global intracellular Ca(2+) concentration ([Ca(2+)](i)) fluctuations occurred, whereas Ca(2+) sparks and contractions were absent. In early developmental stages (EDS), contractions as well as Ca(2+) sparks were obvious. During the further differentiation to late developmental stage (LDS) cardiomyocytes, a marked increase in the frequency of global [Ca(2+)](i) transients, the amplitude and the frequency of Ca(2+) sparks, as well as the expression of RyRs and the volume of RyR-positive SR, was observed. Furthermore, the caffeine-releasable SR Ca(2+) load was elevated in LDS compared with EDS cardiomyocytes. A high-Ca(2+) solution raised spark frequency as well as amplitude in EDS cardiomyocytes to the levels of LDS cardiomyocytes. The characteristics of Ca(2+) sparks occurring in cardiomyocytes differentiated from ES cells may be governed by the Ca(2+) load of the SR and/or the density of RyRs.
Sauer
H
H
Department of Neurophysiology, University of Cologne, D-50931 Cologne, Germany.
Theben
T
T
Hescheler
J
J
Lindner
M
M
Brandt
M C
MC
Wartenberg
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002454:Cell Differentiation; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology; D004622:Embryo, Mammalian / Q000166:cytology*; D051379:Mice; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology*; D013997:Time Factors
D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium