Scanning electron microscopy of acellular glomeruli in nephrotic syndrome

Abstract

All cellular elements were extracted from portions of 13 renal biopsies performed for nephrotic syndrome and the acellular glomerular basement membrane (GBM) examined by scanning electron microscopy (SEM). Five biopsy specimens did not contain subepithelial deposits by light microscopy (LM), immunofluorescence (IF), and transmission electron microscopy (TEM). SEM of the acellular GBM showed a uniform slightly granular surface identical to that previously reported for normal human GBM. Eight biopsy specimens contained subepithelial deposits by LM, IF, and TEM. SEM showed complete extraction of deposits and a spectrum of clearly visualized diffuse GBM alterations in response to subepithelial deposits. Shallow pits or indentations of the GBM were noted in two cases stage I MGN which correlated with numerous 'pinholes' visualized by LM in tangential sections of the GBM on silver stain. A complex reticular pattern of GBM elaboration was observed in cases of stage II MGN corresponding to 'spikes' visualized by LM on silver stain. SEM of glomeruli following cell extraction permits the first direct three-dimensional visualization of the GBM alterations occurring in various stages of subepithelial immune complex formation.