title: Regulation of proliferation of the fetal myocardium.
abstract: Growth of the myocardium involves the completion of a fixed number of rounds of cell division during the embryonic and fetal stages followed by entry into a postmitotic state and hypertrophy of the postmitotic cardiomyocytes during the later stages of heart growth. It has been suggested that at the time of its determination in the early embryo, the embryonic myocardium is programmed for a fixed and limited number of cell divisions, after which the transition to the postmitotic state occurs autonomously. The proliferative response of cultured myocardium of the fetal chick was explored in four culture settings: monolayer cell culture, collagen lattice culture, organ culture of reaggregated cardiomyocyte tissue (cardiomyocyte spheroid culture), and organ culture of pieces of the ventricle wall. Several growth factors were identified by their ability to stimulate DNA synthesis in cardiomyocytes, identified by the incorporation of 5-bromodeoxyuridine (BrdU). The serine proteases thrombin and trypsin, fibroblast growth factor-2 (FGF-2), transforming growth factor-alpha (TGF-alpha), and insulin-like growth factor-II (IGF-II) all show growth factor activity but only for cardiomyocytes cultured in three-dimensional myocardial tissue, and not for cardiomyocytes maintained in monolayer cell culture. Thus, during its proliferation phase, the growth of the fetal myocardium is not controlled solely by internal, cell-autonomous programs, but is subject to external regulation by a family of peptide growth factors. The unconventional setting of three-dimensional culture of the myocardium is required to demonstrate its responsiveness to growth factor challenge.
authors.affiliation: Department of Molecular and Cellular Biology, University of California, Davis, California 95616, USA.
authors.forename: M T
authors.initials: MT
authors.lastname: Armstrong
authors.forename: D Y
authors.initials: DY
authors.lastname: Lee
authors.forename: P B
authors.initials: PB
authors.lastname: Armstrong
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002642:Chick Embryo; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000196:embryology*; D006706:Homeostasis; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology; D008246:Lysophospholipids / Q000494:pharmacology; D009024:Morphogenesis; D009206:Myocardium / Q000166:cytology*; D009924:Organ Culture Techniques; D010446:Peptide Fragments / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology; D016211:Transforming Growth Factor alpha / Q000494:pharmacology
chemical_list: D008246:Lysophospholipids; D010446:Peptide Fragments; D010982:Platelet-Derived Growth Factor; D016211:Transforming Growth Factor alpha; D016222:Fibroblast Growth Factor 2; C086309:thrombin receptor peptide SFLLRNP; D007335:Insulin-Like Growth Factor II; D013917:Thrombin