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.

FB21, a monoclonal antibody that reacts with a sialic-acid-dependent carbohydrate epitope, is a marker for glomerular endothelial cell injury.

BACKGROUND: FB21 is reactive with glomerular endothelial cells and distal tubules of the human kidney and is bound to a sialic-acid-dependent cell-surface antigen. We evaluated FB21 staining in fetal kidneys and kidneys of children and adults with normal kidneys and glomerulonephritis and investigated whether FB21 can be used as a marker for endothelial cell injury. METHODS: This study was performed on 6 children, 10 adults, and 12 fetuses with normal kidneys and 113 patients diagnosed with primary and secondary glomerulonephritis. We evaluated renal staining for FB21 in children with normal kidneys and glomerulonephritis and measured serum E-selectin concentrations in patients with hemolytic uremic syndrome (HUS) and Henoch-Schönlein purpura nephritis (HSPN). RESULTS: (1) FB21 was reactive with endothelial cells of normal kidneys and detected on the surface of endothelial cells by immunoelectron microscopy. (2) FB21 was reactive with endothelial cells in kidneys of fetuses older than 32 weeks. (3) Endothelial cell FB21 staining scores in the first renal biopsy specimens of patients with HUS and HSPN were lower than those in normal kidneys of children and correlated negatively with serum E-selectin concentrations. (4) Endothelial cell FB21 staining of crescentic and sclerotic glomerular lesions in patients with immunoglobulin A nephropathy, membranoproliferative glomerulonephritis, and focal glomerulosclerosis was weaker than that in normal kidneys. CONCLUSION: These results suggest that FB21 can be used as a marker for glomerular endothelial cell injury in various types of glomerulonephritis.