title: Dedifferentiation and proliferation of mammalian cardiomyocytes.
abstract: BACKGROUND
  It has long been thought that mammalian cardiomyocytes are terminally-differentiated and unable to proliferate. However, myocytes in more primitive animals such as zebrafish are able to dedifferentiate and proliferate to regenerate amputated cardiac muscle.
  
  
  RESULTS
  Here we test the hypothesis that mature mammalian cardiomyocytes retain substantial cellular plasticity, including the ability to dedifferentiate, proliferate, and acquire progenitor cell phenotypes. Two complementary methods were used: 1) cardiomyocyte purification from rat hearts, and 2) genetic fate mapping in cardiac explants from bi-transgenic mice. Cardiomyocytes isolated from rodent hearts were purified by multiple centrifugation and Percoll gradient separation steps, and the purity verified by immunostaining and RT-PCR. Within days in culture, purified cardiomyocytes lost their characteristic electrophysiological properties and striations, flattened and began to divide, as confirmed by proliferation markers and BrdU incorporation. Many dedifferentiated cardiomyocytes went on to express the stem cell antigen c-kit, and the early cardiac transcription factors GATA4 and Nkx2.5. Underlying these changes, inhibitory cell cycle molecules were suppressed in myocyte-derived cells (MDCs), while microRNAs known to orchestrate proliferation and pluripotency increased dramatically. Some, but not all, MDCs self-organized into spheres and re-differentiated into myocytes and endothelial cells in vitro. Cell fate tracking of cardiomyocytes from 4-OH-Tamoxifen-treated double-transgenic MerCreMer/ZEG mouse hearts revealed that green fluorescent protein (GFP) continues to be expressed in dedifferentiated cardiomyocytes, two-thirds of which were also c-kit(+).
  
  
  CONCLUSIONS
  Contradicting the prevailing view that they are terminally-differentiated, postnatal mammalian cardiomyocytes are instead capable of substantial plasticity. Dedifferentiation of myocytes facilitates proliferation and confers a degree of stemness, including the expression of c-kit and the capacity for multipotency.
authors.affiliation: Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California, United States of America.
authors.forename: Yiqiang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Tao-Sheng
authors.initials: TS
authors.lastname: Li
authors.forename: Shuo-Tsan
authors.initials: ST
authors.lastname: Lee
authors.forename: Kolja A
authors.initials: KA
authors.lastname: Wawrowsky
authors.forename: Ke
authors.initials: K
authors.lastname: Cheng
authors.forename: Giselle
authors.initials: G
authors.lastname: Galang
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Malliaras
authors.forename: M Roselle
authors.initials: MR
authors.lastname: Abraham
authors.forename: Charles
authors.initials: C
authors.lastname: Wang
authors.forename: Eduardo
authors.initials: E
authors.lastname: Marbán
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D050991:GATA4 Transcription Factor / Q000235:genetics / Q000378:metabolism; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000378:metabolism; D051381:Rats; D011921:Rats, Inbred WKY; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D050991:GATA4 Transcription Factor; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C484469:Nkx2-5 protein, mouse; C524161:Nkx2-5 protein, rat; D014157:Transcription Factors