Susan A. Thompson

Publications (2)5.17 Total impact

• Article: Engraftment of human embryonic stem cell derived cardiomyocytes improves conduction in an arrhythmogenic in vitro model.

  Susan A Thompson, Paul W Burridge, Elizabeth A Lipke, Michael Shamblott, Elias T Zambidis, Leslie Tung
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  ABSTRACT: In this study, we characterized the electrophysiological benefits of engrafting human embryonic stem cell-derived cardiomyocytes (hESC-CMs) in a model of arrhythmogenic cardiac tissue. Using transforming growth factor-β treated monolayers of neonatal rat ventricular cells (NRVCs), which retain several key aspects of the healing infarct such as an excess of contractile myofibroblasts and slowed, heterogeneous conduction, we assessed the ability of hESC-CMs to improve conduction and prevent arrhythmias. Cells from beating embryoid bodies (hESC-CMs) can form functional monolayers which beat spontaneously and can be electrically stimulated, with mean action potential duration of 275 ± 36 ms and conduction velocity (CV) of 10.6 ± 4.2 cm/s (n = 3). These cells, or cells from non-beating embryoid bodies (hEBCs) were added to anisotropic, NRVC monolayers. Immunostaining demonstrated hESC-CM survival and engraftment, and dye transfer assays confirmed functional coupling between hESC-CMs and NRVCs. Conduction velocities significantly increased in anisotropic NRVC monolayers after engraftment of hESC-CMs (13.4 ± 0.9 cm/s, n = 35 vs. 30.1 ± 3.2 cm/s, n = 20 in the longitudinal direction and 4.3 ± 0.3 cm/s vs. 9.3 ± 0.9 cm/s in the transverse direction), but decreased to even lower values after engraftment of non-cardiac hEBCs (to 10.6 ± 1.3 cm/s and 3.1 ± 0.5 cm/s, n = 11, respectively). Furthermore, reentrant wave vulnerability in NRVC monolayers decreased by 20% after engraftment of hESC-CMs, but did not change with engraftment of hEBCs. Finally, the culture of hESC-CMs in transwell inserts, which prevents juxtacrine interactions, or engraftment with connexin43-silenced hESC-CMs provided no functional improvement to NRVC monolayers. These results demonstrate that hESC-CMs can reverse the slowing of conduction velocity, reduce the incidence of reentry, and augment impaired electrical propagation via gap junction coupling to host cardiomyocytes in this arrhythmogenic in vitro model.
  Journal of Molecular and Cellular Cardiology 07/2012; 53(1):15-23. · 5.17 Impact Factor
• Article: Influence of Electromechanical Activity on Cardiac Differentiation of Mouse Embryonic Stem Cells

  Worawan Limpitikul, Nicolas Christoforou, Susan A. Thompson, John D. Gearhart, Leslie Tung, Elizabeth A. Lipke
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  ABSTRACT: During differentiation, mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs) receive electromechanical cues from spontaneous beating. Therefore, promoting electromechanical activity via electrical pacing or suppressing it by drug treatment might affect the cellular functional development. Electrical pacing was applied to confluent monolayers of mESC-CMs during late-stage differentiation (days 16–18). Alternatively, spontaneous contraction was suppressed by (a) blocking ion currents with CsCl (HCN channel), trazodone (T-type Ca2+ channel), or both CsCl and trazodone on days 11–18; or (b) applying blebbistatin (excitation–contraction uncoupler) on days 11–14. Electrophysiological properties and gene expression were examined on day 19 and 18, respectively. Optical mapping revealed no significant difference in conduction velocity (CV) in paced vs. non-paced monolayers, nor were there significant changes in gene expression of connexin-43, Na–Ca exchanger (NCX), or myosin heavy chain (MHC). However, CV variability among differentiation batches and CV heterogeneity within individual monolayers were significantly lower in paced mESC-CMs. Alternatively, while the four drug treatments suppressed contraction with varying degrees (up to complete inhibition), there was no significant difference in CV for any of the treatments compared with controls. Trazodone treatment significantly reduced CV variability as compared to controls, whereas CsCl treatment significantly reduced CV heterogeneity. Distinct changes in gene expression of connexin-43, MHC, HCNl, Cav3.1/3.2 were not observed. Electrical pacing, but not suppression of spontaneous contraction, during late-stage differentiation reduces the intrinsic variability of CV among differentiation batches and across individual monolayers, which can be beneficial in the application of ESCs for myocardial tissue repair. KeywordsElectrical stimulation-Electrophysiology-Cell culture-Optical mapping-Cardiac regeneration
  04/2012; 1(3):179-193.