Scanning electron microscopy of the acellular glomerular basement membranes in idiopathic membranous glomerulopathy.

After using a cellular digestion technique to extract cells from the basement membranes of frozen kidney tissue, we employed scanning electron microscopy to examine the acellular glomerular basement membranes (AGBM) from normal kidneys and from kidneys of patients with idiopathic membranous glomerulopathy (MGN). This method revealed, in the AGBM, previously unrecognized three-dimensional patterns of pathologic changes. These patterns correlated with increasing MGN stage as defined by Ehrenreich and Churg. On the epimembranous AGBM surface these patterns were composed of ridge-like trabeculae, irregular plaques, and reticulated crater-like deformities. The endothelial AGBM surfaces were smooth in stages I and II MGN, but in stage III MGN the endothelial surfaces were irregular and perforated. In contrast to lupus-related MGN, where some immune-complex-like material remained after cellular extraction, epimembranous immune-complex-like material in idiopathic MGN was extracted.