PMC

Photomicrographs with Masson's trichrome stain. In the control group, A) the vessel wall is intact (orig. ×5) and B) the integrity of the endothelial cells and subendothelial elastic fibers is preserved (orig. ×40). Note the homogeneity of the muscular fibers. In the study group, C) tissue is detached within the subendothelial layer (orig. ×5), with less intense staining than in the images from the control group; and D) injury to the endothelial layer and subendothelial elastic fibers is evident (orig. ×40). Note the irregularity of the endothelial layer and separation of the subendothelial layers.
EL = endothelial layer; L = lumen; M = muscular fibers; SEL = subendothelial layer

Thrombotic microangiopathy in arterioles of resection specimen (a, b) and prior colonic mucosal biopsies (c, d). a Arterioles in muscularis propria with subendothelial fibrin. b Submucosal arterioles showing marked subendothelial edema with formation of concentric layers of new basement membrane material. c Capillaries/arterioles of deep lamina propria and superficial submucosa with intraluminal fibrin thrombi (arrows). Arteriole with subendothelial edema and new subendothelial basement membrane layer (arrowhead). d Superficial submucosal arteriole with subendothelial fibrin (arrow) and perivascular hemorrhage. (hematoxylin and eosin, original magnification ×400 for a–d)

Disruption of anionic sites in the GBM are manifested as a reduction in PEI labelling. In control mice, the punctuate PEI labelling is distributed in a semi-regular pattern along the subepithelial and subendothelial laminae rarae (A). Agrin mutants (B) show a reduction in the subepithelial labelling only, whereas perlecan mutants (C) show a decrease in the subendothelial layer only. Double mutants (D) show diminished labelling along both the subepithelial and subendothelial aspects. Quantitative analyses (E and F) reveal a significant reduction in subepithelial labelling in agrin mutants and double mutants when compared to littermate controls and perlecan mutants (P < 0.001). A significant reduction in subendothelial labelling was found in perlecan mutants and double mutants when compared to littermate controls and agrin mutants (P < 0.03). Magnification 14 000×; scale bar, 1 μm.

Electron microscopy. a, b Subendothelial deposits in glomeruli. Unique deposits characterized by randomly arranged large fibrils with large central bores and double layer structures are apparent. (c) Cryoprecipitate. Similar structures to the subendothelial deposits in glomeruli are apparent. (Original magnification, a: 4000×, b: 12,000×, c: 8000×)