SEM studies of acellular glomerular basement membrane in human diabetic glomerulopathy

Abstract

Previous transmission electron microscopic studies have demonstrated glomerular basement membrane (GBM) thickening and mesangial matrix (MM) expansion in chronic stages of diabetes. It is difficult, however, to achieve an appreciation of GBM surface features and distribution of MM in planar views. In the current study, autopsy human renal cortical tissue from patients with end-stage diabetic nephropathy were minced and rendered acellular with detergents prior to fixation, cryofracture, and preparation for light microscopic (LM), transmission electron microscopic (TEM), and scanning electron microscopic (SEM) observation in an effort to visualize extracellular materials in three dimensions. Our studies demonstrated that although diabetic glomerular changes vary widely within and between individuals, most showed alterations primarily affecting peripheral (epithelial) GBM (with MM increased but diffusely distributed), or they exhibited similar GBM changes but with variable nodular MM expansion leading ultimately to capillary occlusion. Both types showed peripheral GBM thickening and demonstrated external surface irregularities that by SEM appeared as "cauliflower-like" lobulations. In these glomeruli, GBM lamellation or reduplication was common with internal layers frequently thrown into lumenward projections. Glomeruli with diffusely distributed MM generally showed patent capillary channels with little evidence of occlusion. By TEM, highly compact, epithelial GBMs were clearly distinguishable from the electron-lucent MM. In these preparations the matrix was concentrated in relatively small discrete masses sometimes covered by a finely fibrillar material, which extended intermittently onto lumenal surfaces of epithelial GBMs. In more advanced stages of MM involvement, glomeruli typically exhibited smooth-surfaced nodules that were increased at the expense of capillary surface area. By TEM, MM nodules were comprised of a meshwork of very fine (20-A) fibrils surrounding a variety of detergent-resistant structures including collagenous fibrils and non-collagenous 30-nm circular fibrils with 16-nm subunits. By SEM, GBM and MM nodules were not distinguishable and merged to form substantial barriers to capillary blood flow. In those capillary channels remaining patent, inwardly projecting folds and ridges were common GBM features, and frequently thin fenestrated layers, distinctly separate from epithelial GBMs, formed sieve-like linings for the channels. These three-dimensional observations provide unique views of the processes leading to diabetic glomerular occlusion and suggest a potential for this technique in the study of renal BM disease.

Ultrastructural Analyses of Acellular Glomerular Basement Membranes and Mesangial Matrix in a Spontaneously Diabetic Rhesus Monkey

“…1986a. b;Carlson and Surerus, 1986;, Using this technique we have shown that normal monkey acellular GBMs resemble loops of capillary tufts [Carlson and Kenney. 1982;Carl son et al.…”

“…both of which were described in diabetic human kidneys [Osterby et al. 1983;Carlson and Surerus. 1986], Our TEM studies also show' that in the diabetic monkey the expanded centrolobular MM is composed of a fibrillar network which surrounds larger fibrils including striated collagen.…”

“…Similar collagen fibrils were reported in diabetic human MM [Osterby. 1983: Carlson andSurerus. 1986], but whorled or circular fibrils (also identified in humans [Osterby.…”

“…1986], but whorled or circular fibrils (also identified in humans [Osterby. 1983: Carlson andSurerus. 1986]) were not iden tified in the present investigation.…”

Significant glomerular basement membrane thickening in hyperglycemic and normoglycemic diabetic‐prone BB Wistar rats

“…We have previously shown in several species that at the level of LM, detergent treatment completely removed cellular components while glomerular ECM components, including various renal basement membranes, maintain their normal histoarchitectures Hinds, 1981, 1983;Carlson and Kenney, 1982;Carlson and Chatterjee, 1983;Carlson and Surerus, 1986;Marion and Carlson, 1989;Carlson et al, 1997). Likewise in the current study, whole acellular glomeruli from BB/DR, BB/DP h , and BB/ DP n animals at 1 year postonset of diabetes showed normal morphological features and were virtually indistinguishable with only minor increases in MM in BB/DP h kidneys.…”