title: Mechanical Stress Conditioning and Electrical Stimulation Promote Contractility and Force Maturation of Induced Pluripotent Stem Cell-Derived Human Cardiac Tissue.
abstract: BACKGROUND
  Tissue engineering enables the generation of functional human cardiac tissue with cells derived in vitro in combination with biocompatible materials. Human-induced pluripotent stem cell-derived cardiomyocytes provide a cell source for cardiac tissue engineering; however, their immaturity limits their potential applications. Here we sought to study the effect of mechanical conditioning and electric pacing on the maturation of human-induced pluripotent stem cell-derived cardiac tissues.
  
  
  METHODS
  Cardiomyocytes derived from human-induced pluripotent stem cells were used to generate collagen-based bioengineered human cardiac tissue. Engineered tissue constructs were subjected to different mechanical stress and electric pacing conditions.
  
  
  RESULTS
  The engineered human myocardium exhibits Frank-Starling-type force-length relationships. After 2 weeks of static stress conditioning, the engineered myocardium demonstrated increases in contractility (0.63±0.10 mN/mm2vs 0.055±0.009 mN/mm2for no stress), tensile stiffness, construct alignment, and cell size. Stress conditioning also increased SERCA2 (Sarco/Endoplasmic Reticulum Calcium ATPase 2) expression, which correlated with a less negative force-frequency relationship. When electric pacing was combined with static stress conditioning, the tissues showed an additional increase in force production (1.34±0.19 mN/mm2), with no change in construct alignment or cell size, suggesting maturation of excitation-contraction coupling. Supporting this notion, we found expression of RYR2 (Ryanodine Receptor 2) and SERCA2 further increased by combined static stress and electric stimulation.
  
  
  CONCLUSIONS
  These studies demonstrate that electric pacing and mechanical stimulation promote maturation of the structural, mechanical, and force generation properties of human-induced pluripotent stem cell-derived cardiac tissues.
authors.affiliation: From Department of Bioengineering (J.-L.R, M.V.R., M.R., C.E.M.), Program in Molecular and Cellular Biology (N.L.T.), Department of Pathology (N.L.T., M.R., V.M., L.P., H.R., C.E.M.), and Department of Medicine/Cardiology (C.E.M.), Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle.
authors.forename: Jia-Ling
authors.initials: JL
authors.lastname: Ruan
authors.affiliation: From Department of Bioengineering (J.-L.R, M.V.R., M.R., C.E.M.), Program in Molecular and Cellular Biology (N.L.T.), Department of Pathology (N.L.T., M.R., V.M., L.P., H.R., C.E.M.), and Department of Medicine/Cardiology (C.E.M.), Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle.
authors.forename: Nathaniel L
authors.initials: NL
authors.lastname: Tulloch
authors.affiliation: From Department of Bioengineering (J.-L.R, M.V.R., M.R., C.E.M.), Program in Molecular and Cellular Biology (N.L.T.), Department of Pathology (N.L.T., M.R., V.M., L.P., H.R., C.E.M.), and Department of Medicine/Cardiology (C.E.M.), Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle.
authors.forename: Maria V
authors.initials: MV
authors.lastname: Razumova
authors.affiliation: From Department of Bioengineering (J.-L.R, M.V.R., M.R., C.E.M.), Program in Molecular and Cellular Biology (N.L.T.), Department of Pathology (N.L.T., M.R., V.M., L.P., H.R., C.E.M.), and Department of Medicine/Cardiology (C.E.M.), Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle.
authors.forename: Mark
authors.initials: M
authors.lastname: Saiget
authors.affiliation: From Department of Bioengineering (J.-L.R, M.V.R., M.R., C.E.M.), Program in Molecular and Cellular Biology (N.L.T.), Department of Pathology (N.L.T., M.R., V.M., L.P., H.R., C.E.M.), and Department of Medicine/Cardiology (C.E.M.), Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle.
authors.forename: Veronica
authors.initials: V
authors.lastname: Muskheli
authors.affiliation: From Department of Bioengineering (J.-L.R, M.V.R., M.R., C.E.M.), Program in Molecular and Cellular Biology (N.L.T.), Department of Pathology (N.L.T., M.R., V.M., L.P., H.R., C.E.M.), and Department of Medicine/Cardiology (C.E.M.), Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle.
authors.forename: Lil
authors.initials: L
authors.lastname: Pabon
authors.affiliation: From Department of Bioengineering (J.-L.R, M.V.R., M.R., C.E.M.), Program in Molecular and Cellular Biology (N.L.T.), Department of Pathology (N.L.T., M.R., V.M., L.P., H.R., C.E.M.), and Department of Medicine/Cardiology (C.E.M.), Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle.
authors.forename: Hans
authors.initials: H
authors.lastname: Reinecke
authors.affiliation: From Department of Bioengineering (J.-L.R, M.V.R., M.R., C.E.M.), Program in Molecular and Cellular Biology (N.L.T.), Department of Pathology (N.L.T., M.R., V.M., L.P., H.R., C.E.M.), and Department of Medicine/Cardiology (C.E.M.), Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle. murry@uw.edu mregnier@uw.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Regnier
authors.affiliation: From Department of Bioengineering (J.-L.R, M.V.R., M.R., C.E.M.), Program in Molecular and Cellular Biology (N.L.T.), Department of Pathology (N.L.T., M.R., V.M., L.P., H.R., C.E.M.), and Department of Medicine/Cardiology (C.E.M.), Center for Cardiovascular Biology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle. murry@uw.edu mregnier@uw.edu.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Murry
mesh_terms: D000818:Animals; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000502:physiology*; D013314:Stress, Mechanical; D023822:Tissue Engineering / Q000379:methods*
keywords: cardiomyocyte hypertrophy; electrical stimulation; human myocardium; stem cell; stress; tissue engineering