Actin, aortic smooth muscle
cytoplasm
Development of glomerular endothelial cells, podocytes and mesangial cells in the human fetus and infant.
The process of glomerular development consists of four developmental stages: vesicle (V) stage, S-shaped body (S) stage, capillary loop (C) stage and maturation (M) stage. However, the development of glomerular endothelial, mesangial and epithelial cells in fetal and infant kidneys remains unclear. In order to determine the characteristics of human glomerular development, we investigated the process of glomerular development by staining fetal and infant kidneys for CD31, CD34 and FB21, markers for endothelial cells, alpha-smooth muscle actin (alpha-SMA), a marker for mesangial cells, and nephrin, a marker for podocytes. These series of studies were carried out on kidneys obtained at autopsy from 27 fetuses and 5 infants. The fetuses were divided into the following 5 groups according to gestational age; 13-19, 20-24, 25-29, 30-34 and 35-39 weeks. In each group, glomerular development was classified according to the developmental stage and the staining patterns for CD31, CD34, FB21, alpha-SMA and nephrin. The proportion of V-stage development in 100 glomeruli examined was highest at 13-19 weeks. After 20 weeks, the V-stage proportion decreased gradually, and the proportion of S stage became highest at 20-24 weeks. The C-stage proportion was highest at 25-29 weeks, while the M-stage proportion was highest in infants aged 1-6 months. The staining patterns for CD31, CD34 and FB21 were similar in endothelial cells after 25 weeks of gestation. Staining of alpha-SMA and nephrin was first observed in the S stage. In conclusion, maturation of endothelial cells starts at 25 weeks and is completed by 35 weeks of gestation. Epithelial cells and mesangial cells first appear during the S stage.