Glomerular endothelial cells form diaphragms during development and pathologic conditions.

Unlike most fenestrated capillary endothelial cells, adult glomerular endothelial cells (GEnC) are generally thought to lack diaphragms at their fenestrae, but this remains controversial. In this study, morphologic and immunocytochemical analyses demonstrated that, except for a small fraction, GEnC of adult rats lacked diaphragmed fenestrae, which contain the transmembrane glycoprotein PV-1. In contrast, the GEnC in embryonic rats exhibited diaphragmed fenestrae and expressed PV-1 protein. The luminal surface of the fenestral diaphragm possesses a high density of anionic sites, thereby compensating for the functional immaturity of the embryonic glomerular filtration barrier. In addition, GEnC with diaphragmed fenestrae and PV-1 expression were significantly increased in adult rats with Thy-1.1 nephritis, presumably reflecting a process of restorative remodeling of the glomerular capillary tuft after injury; therefore, the reappearance of PV-1 expression and diaphragmed fenestrae may serve as a marker of glomerular capillary remodeling.