Enzymatic dissection of the glomerulus.
White rat kidneys were fixed in perfusion, postfixed with 10% glutaraldehyde, and cut into 1-mm slices. The slices were treated with a sequential digestion over 4 days with trypsin, pepsin, and pronase E. This treatment dissolved the glomerular basement membrane and the mesangial matrix. Teasing the slides in buffer released many glomeruli and tubules which were prepared for scanning electron microscopy while attached to gelatine glass cover slips. Four human renal biopsies were similarly treated. The enzymatic removal of the basement membrane permitted viewing of the basilar or capillary slide of loosened podocytes and their processes. The cell body of the podocytes often exhibited a considerable area of contact with the basement membrane. The primary and secondary podocyte processes and foot processes maintained a continuous contact with the basement membrane. Human podocytes, although larger, were similar to the rat. Podocytes from minimal change disease showed severe retraction and flattening of primary and secondary processes and foot processes. Extensive visualization of the basilar surface of the exposed endothelial tubes was possible with this technique. The fenestrated and nonfenestrated portions were revealed including the axial area where the endothelial cells contact the mesangial cells and matrix, which formed an impression on the surface of the endothelium. The mesangial cells and their connecting processes (the mesangial network) were revealed extending from the peripheral lobule to the glomerular hilus where they merged with lacis cells. The mesangial cells exhibited a variety of processes which anchored into the mesangial matrix. At the hilus, these cells assumed a flat, villous, lacy appearance, and these cells encircled the large hilar capillaries. Glomeruli with afferent and efferent arterioles and associated Goormaghtigh (lacis) cells were identified. The transition between mesangial, Goormaghtigh, and smooth muscle cells was observed. These observations provide a unique view of the organization of the rat and human glomerulus and suggest the potential for the use of the present technique in the study of diseased glomeruli.
D000818:Animals; D001160:Arterioles / Q000473:pathology; D004798:Enzymes / Q000378:metabolism; D006801:Humans; D007678:Kidney Glomerulus / Q000033:anatomy & histology* / Q000098:blood supply / Q000648:ultrastructure; D008722:Methods; D008854:Microscopy, Electron; D051381:Rats; D011919:Rats, Inbred Strains
D004798:Enzymes