title: Development of the Heart Endocardium at an Early Stage of Chick Embryos Evaluated at Light- and Electron-Microscopic Levels.
abstract: Development of the endocardium in the heart of 4 to 4·1/2-day-incubated chick embryos was observed light and electron microscopically, and these results were evaluated by immunohistochemistry for desmin, FLK1 (VEGFR-2) or CD31, and by in situ hybridization assays for flk1-mRNA expression. At this developmental stage, the atrium and the ventricle were already discriminated by formation of the atrio-ventricular junction. The cardiac wall consisted of three layers; the inner endocardium, the middle myocardium, and the outer epicardium. The developing endocardium was seen as a chain of single-layered endocardial cells. Along its inner surface, numerous clusters of blood corpuscles were distributed, which seemed to contain some undifferentiated endocardial cells estimated from their characteristic ultrastructure and histological topography. Several blood corpuscles were in directly contact with the myocardium at the missing portions of the developing endocardial cell-chains. Differentiating endocardial cells individually showed roundish, small and large crescent, or flat in shapes. Such a prominent change of cell shapes appeared to be in parallel with their secretory activity during the transformation from the undifferentiated cells to the endocardial cells. Furthermore, immunohistochemistry for FLK1 or CD31, and in situ hybridization assays for flk1-mRNA labeled the cells composing developing endocardial cell-chains. Though these expressional analyses could not document clearly the transition of precursor cells into endocardial cells, the present study provided for the first time some important information regarding the morphological transition process toward endocardial cells at ultrastructural levels. Anat Rec, 299:1080-1089, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Department of Anatomy, Tissue and Cell Biology, Tsurumi University School of Dental Medicine, Yokohama, Japan.
authors.forename: Yaiko
authors.initials: Y
authors.lastname: Hara
authors.affiliation: Department of Anatomy, Tissue and Cell Biology, Tsurumi University School of Dental Medicine, Yokohama, Japan.|Liver Research Unit, Minophagen Pharmaceutical Co., Ltd., Tokyo, Japan.
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Wake
authors.affiliation: Research Center of Electron Microscopy, School of Dental Medicine, Tsurumi University, Yokohama, Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Inoue
authors.affiliation: Department of Anatomy, Tissue and Cell Biology, Tsurumi University School of Dental Medicine, Yokohama, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Kuroda
authors.affiliation: Department of Anatomy, Tissue and Cell Biology, Tsurumi University School of Dental Medicine, Yokohama, Japan.
authors.forename: Akie
authors.initials: A
authors.lastname: Sato
authors.affiliation: PhenixBio Co., Ltd., Hiroshima, Japan.
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Inamatsu
authors.affiliation: PhenixBio Co., Ltd., Hiroshima, Japan.
authors.forename: Chise
authors.initials: C
authors.lastname: Tateno
authors.affiliation: Department of Anatomy, Tissue and Cell Biology, Tsurumi University School of Dental Medicine, Yokohama, Japan.
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Sato
mesh_terms: D000818:Animals; D002642:Chick Embryo; D004699:Endocardium / Q000196:embryology / Q000648:ultrastructure*; D018507:Gene Expression Regulation, Developmental; D006321:Heart / Q000033:anatomy & histology* / Q000196:embryology*; D007124:Immunoenzyme Techniques; D008854:Microscopy, Electron / Q000379:methods*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism
chemical_list: D040301:Vascular Endothelial Growth Factor Receptor-2
keywords: chick embryo; development; endocardium; heart; vasculogenesis