Molecular characterization and functional properties of cardiomyocytes derived from human inducible pluripotent stem cells.
Bottom Line: The two iPS clones investigated here were generated through infection of human foreskin fibroblasts (HFF) with retroviruses containing the four human genes: OCT4, Sox2, Klf4 and C-Myc.Our major findings showed that iPS-derived cardiomyocytes: (i) express cardiac specific RNA and proteins; (ii) exhibit negative force-frequency relations and mild (compared to adult) post-rest potentiation; (iii) respond to ryanodine and caffeine, albeit less than adult cardiomyocytes, and express the SR-Ca(2+) handling proteins ryanodine receptor and calsequestrin.Hence, this study demonstrates that in our cardiomyocytes clones differentiated from HFF-derived iPS, the functional properties related to excitation-contraction coupling, resemble in part those of adult cardiomyocytes.
Affiliation: The Sohnis Family Stem Cells Center, Technion - Israel Institute of Technology, Haifa, Israel.Show MeSH
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Mentions: A fundamental property of the adult human myocardium is its ability to increase the contraction force in response to increased rate of stimulation. The phenomenon termed positive force–frequency relations (FFRs), which is related to SR Ca2+ release, is utilized by the heart to increase cardiac output under exercise or stress conditions. To generate FFRs, iPS-CM preparations were stimulated at increasing frequencies (0.5, 0.7, 0.9, 1 and 1.2 Hz), and contraction was measured at each frequency after steady state was attained. Although we used high voltages and long stimulus durations, we were unable to stimulate the EBs above at stimulation rates >1.2–1.5 Hz. As depicted by the representative experiments, both in the iPS-CM clones investigated and in the hESC-CM clone H9.2 investigated, increasing the rate of stimulation caused a decrease in contraction amplitude (Fig. 5A–D). Please note that the discontinuous traces in Fig. 5A–D result from digitalization of the original signal which was sampled at 100 points/sec. In summary, both iPS-CM clones and the hESC-CM clone H9.2 exhibited the same extent of negative FFRs, which was statistically significant (P, 0.05, two-way ANOVA) for all the clones investigated (Fig. 5E).
Affiliation: The Sohnis Family Stem Cells Center, Technion - Israel Institute of Technology, Haifa, Israel.