Ratajska Anna, Czarnowska Elzbieta, Kołodzińska Agnieszka, Kluzek Wojciech, Leśniak Wojciech
Department of Pathological Anatomy, Medical University of Warsaw, Warsaw, Poland.
Anat Rec A Discov Mol Cell Evol Biol. 2006 Mar;288(3):223-32. doi: 10.1002/ar.a.20311.
The earliest vascular structures (blood island-like) in the embryonic heart are clusters of angioblasts and nucleated red blood cells (NRBCs), which differentiate into endothelial cells and erythrocytes, respectively. Our purpose was to define the area and chronology of NRBC appearance in the mouse embryonic heart at the stages before a patency between coronary vessels and peripheral circulation is established (10.5-13.5 dpc). Before and at the onset of vascularization, NBCs were not present within the proepicardium; however, Ter/119+ differentiating erythroblasts and single scattered CD45+ were found in the heart beginning from 10.5 dpc. The Ter/119+ cells were in close apposition to angioblasts (PECAM1+) and were recognized as components of blood island-like structures or vascular vesicles in transmission electron microscope and were located mostly in the subepicardium. Some of the NRBCs were not accompanied by angioblasts and located close to the endocardial endothelium or at the border of the endocardial endothelium or in the subepicardium. These erythroblasts were beginning to assemble with angioblasts. CD34+ NBCs as well as progenitor cells of erythroid lineage were not detected in the heart at these stages of development. The state of differentiation of NRBCs of blood islands was similar/the same as the morphology of circulating blood cells at the respective stages of embryo development. The presence of mature NRBCs in the subendocardial area and lack of progenitor cells of erythroid lineage within the heart indicate that erythroid commitment occurs outside the heart. We suggest that NRBCs enter the heart from the blood stream at 10.5-12 dpc independently from angioblasts.
胚胎心脏中最早的血管结构（血岛样）是成血管细胞和成核红细胞（NRBCs）的簇集，它们分别分化为内皮细胞和红细胞。我们的目的是确定在冠状动脉与外周循环建立通畅之前（胚胎发育第10.5 - 13.5天）小鼠胚胎心脏中NRBC出现的区域和时间顺序。在血管形成之前及开始时，心外膜内不存在NRBC；然而，从胚胎发育第10.5天开始，在心脏中发现了Ter/119 +分化中的成红细胞和单个散在的CD45 +细胞。Ter/119 +细胞与成血管细胞（PECAM1 +）紧密相邻，在透射电子显微镜下被识别为血岛样结构或血管小泡的组成部分，且大多位于心外膜下。一些NRBC没有成血管细胞相伴，位于靠近心内膜内皮处、心内膜内皮边界处或心外膜下。这些成红细胞开始与成血管细胞聚集。在这些发育阶段，心脏中未检测到CD34 + NRBC以及红系祖细胞。血岛中NRBC的分化状态与胚胎发育各阶段循环血细胞的形态相似/相同。心内膜下区域存在成熟的NRBC且心脏内缺乏红系祖细胞表明红系定向分化发生在心脏外。我们认为NRBC在胚胎发育第10.5 - 12天从血流进入心脏，独立于成血管细胞。
