title: Contractility of single cardiomyocytes differentiated from pluripotent stem cells depends on physiological shape and substrate stiffness.
abstract: Single cardiomyocytes contain myofibrils that harbor the sarcomere-based contractile machinery of the myocardium. Cardiomyocytes differentiated from human pluripotent stem cells (hPSC-CMs) have potential as an in vitro model of heart activity. However, their fetal-like misalignment of myofibrils limits their usefulness for modeling contractile activity. We analyzed the effects of cell shape and substrate stiffness on the shortening and movement of labeled sarcomeres and the translation of sarcomere activity to mechanical output (contractility) in live engineered hPSC-CMs. Single hPSC-CMs were cultured on polyacrylamide substrates of physiological stiffness (10 kPa), and Matrigel micropatterns were used to generate physiological shapes (2,000-µm(2) rectangles with length:width aspect ratios of 5:1-7:1) and a mature alignment of myofibrils. Translation of sarcomere shortening to mechanical output was highest in 7:1 hPSC-CMs. Increased substrate stiffness and applied overstretch induced myofibril defects in 7:1 hPSC-CMs and decreased mechanical output. Inhibitors of nonmuscle myosin activity repressed the assembly of myofibrils, showing that subcellular tension drives the improved contractile activity in these engineered hPSC-CMs. Other factors associated with improved contractility were axially directed calcium flow, systematic mitochondrial distribution, more mature electrophysiology, and evidence of transverse-tubule formation. These findings support the potential of these engineered hPSC-CMs as powerful models for studying myocardial contractility at the cellular level.
authors.affiliation: Department of Mechanical Engineering, Stanford University, Stanford, CA 94305; Stanford Cardiovascular Institute, Stanford University, Stanford, CA 94305;
authors.forename: Alexandre J S
authors.initials: AJ
authors.lastname: Ribeiro
authors.affiliation: Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158; Roddenberry Center for Stem Cell Biology and Medicine at Gladstone Institutes, San Francisco, CA 94158;
authors.forename: Yen-Sin
authors.initials: YS
authors.lastname: Ang
authors.affiliation: Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158; Roddenberry Center for Stem Cell Biology and Medicine at Gladstone Institutes, San Francisco, CA 94158;
authors.forename: Ji-Dong
authors.initials: JD
authors.lastname: Fu
authors.affiliation: Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158; Roddenberry Center for Stem Cell Biology and Medicine at Gladstone Institutes, San Francisco, CA 94158;
authors.forename: Renee N
authors.initials: RN
authors.lastname: Rivas
authors.affiliation: Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158; Roddenberry Center for Stem Cell Biology and Medicine at Gladstone Institutes, San Francisco, CA 94158; Institute of Cardiovascular Sciences, University of Manchester, Manchester M13 9PT, United Kingdom;
authors.forename: Tamer M A
authors.initials: TM
authors.lastname: Mohamed
authors.affiliation: Department of Mechanical Engineering, Stanford University, Stanford, CA 94305; Stanford Cardiovascular Institute, Stanford University, Stanford, CA 94305;
authors.forename: Gadryn C
authors.initials: GC
authors.lastname: Higgs
authors.affiliation: Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158; Roddenberry Center for Stem Cell Biology and Medicine at Gladstone Institutes, San Francisco, CA 94158; Department of Pediatrics, University of California, San Francisco, CA 94143; Department of Biochemistry & Biophysics, University of California, San Francisco, CA 94143;
authors.forename: Deepak
authors.initials: D
authors.lastname: Srivastava
authors.affiliation: Department of Mechanical Engineering, Stanford University, Stanford, CA 94305; Stanford Cardiovascular Institute, Stanford University, Stanford, CA 94305; Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305 pruitt@stanford.edu.
authors.forename: Beth L
authors.initials: BL
authors.lastname: Pruitt
mesh_terms: D020013:Calcium Signaling; D002454:Cell Differentiation; D048430:Cell Shape; D002478:Cells, Cultured; D006801:Humans; D008929:Mitochondria, Heart; D008954:Models, Biological; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000378:metabolism*
keywords: cardiomyocyte; contractility; sarcomeres; single cell; stem cell