Liver cell rearrangement and apoptosis duirng retardation of fetal hematopoiesis

通过TUNEL方法检查的新生儿肝脏已发现含有垂死的造血细胞，并发现一些肝细胞也呈阳性。关于濒死肝细胞的超微结构特征，两种不同类型的细胞死亡；观察I型和II型。I型细胞死亡的早期特征出现在细胞质中，其特征是粗糙的内质网扩张。II型细胞死亡的特征是异染色质的压实和边沿，形成明显的团块。I型对应于细胞质型变性和非凋亡性死亡，而II型对应于核型细胞死亡或典型凋亡性死亡。I型细胞死亡的发生率远高于II型。用大鼠抗小鼠巨噬细胞单克隆抗体F4/80进行免疫组化染色，可以在光镜下更客观地鉴定巨噬细胞。单位面积f4 /80阳性细胞数从妊娠第11天开始迅速增加，但在出生后第4 ~ 13天显著减少（p<0.01）。在胎儿肝脏中，f4 /80阳性细胞在肝细胞索中被鉴定为造血病灶红母细胞岛的中央巨噬细胞。巨噬细胞含有红细胞挤压核吞噬体和铁阳性包涵体。妊娠第19天，肝细胞中也出现少量f4 /80阳性细胞，但未出现造血细胞。在新生儿肝脏中，也出现少量f4 /80阳性但fe阴性的单核细胞。一些大型巨噬细胞不仅通过经典的细胞凋亡，还通过一种称为“暗细胞形成”的过程发生细胞死亡。出生后早期肝脏中f4 /80阳性但fe阴性的小单核细胞可被认为是肝常驻巨噬细胞的前体。

Neonatal livers examined by the TUNEL method have been found to contain dying hematopoietic cells, and a few hepatocytes have been also found to be positive. Regarding the ultrastructural features of dying hepatocytes, two different types of cell death; types I and II were observed. The early features of type I cell death appeared in the cytoplasm, which was characterized by dilated rough endoplasmic reticulum. Type II cell death was characterized by compaction and margination of heterochromatin resulting in the formation of sharply circumscribed masses. Type I corresponds to cytoplasmic type degeneration and non-apoptotic death, whereas type II corresponds to nuclear type cell death or classical apoptotic death. The incidence of type I cell death was much higher than that of type II.Immunochistochemical staining with rat anti-mouse macrophage monoclonal antibody F4/80 permits a more objective identification of macrophages under light micorscopy. There was a rapid increase in the number of F4/80-positive cells per unit area from 11 days of gestation, but there was a significant decrease between 4 and 13 days after birth(p<0.01). In fetal livers, F4/80-positive cells were identified among hepatic cell cords as central macrophages of erythroblastic islands in the hematopoietic foci. The macrophages contained phagosomes from extruded nuclei of erythroblasts and Fe-positive inclusions. At 19 days of gestation, a few F4/80-positive cells without hematopoietic cells also appeared among hepatocytes. In neonatal livers, a few small F4/80-positive but Fe-negative mononuclear cells also appeared. Some of large macrophages underwent cell death not only through classical apoptosis but also through a process called "dark cell formation." The small F4/80-positive but Fe-negative mononuclear cells in early postnatal livers could be considered as a candidate for a precursor of hepatic resident macrophages.