An electron microscopic study of the glomerular alterations of pure-preeclampsia

Abstract

Ultrastructural glomerular lesions of preeclampsia were studied by electron microscopy in 39 biopsy specimens from 36 patients. Postpartum biopsy obtained on day 0 revealed marked narrowing of the capillary lumen due to endothelial cell swelling, massive subendothelial and mesangial deposits containing lipids and fibrillar fibrins, monocyte invasion in the mesangium, and rupture and duplication of the glomerular capillary wall. Duplication of the glomerular capillary wall generally consisted of the glomerular basement membrane (GBM) and a newly formed mesangial matrix associated with mesangial interposition. However, it was occasionally seen as the GBM and a newly formed basement membrane-like material attached to the GBM side of the endothelial cell membrane without interposing mesangial cells. Podocytes contained many protein resorption droplets in which albumin, immunoglobulins, complements and fibrinogen were observed by immunoelectron microscopy. The massive mesangial and subendothelial deposits were reduced in volume 2 weeks after delivery, and endothelial swelling decreased 3 weeks after delivery. Widening of the subendothelial space of the GBM was still apparent 5 weeks after delivery, although no deposits were observed. By 8 weeks, this widening was not evident. Foam cells and an increase in the mesangial matrix were noted 2-6 weeks and 5-8 weeks after delivery, respectively. Focal glomerular sclerosis lesions were detected in 17 cases. This lesion may have resulted from massive subendothelial and mesangial deposits, rupture of the GBM or epithelial detachment.