Renovascular morphological changes in a rabbit model of hydronephrosis.

Obstructive nephropathy ultimately leads to end-stage renal failure. Renovascular lesions are involved in various nephropathies, and most renal diseases have an ischemic component that underlies the resulting renal fibrosis. The aim of this study was to investigate whether morphological changes occur in the renal vasculature in hydronephrosis and the possible mechanisms involved. A model of complete unilateral ureteral obstruction (CUUO) was used. Experimental animals were divided into five groups: a normal control group (N) and groups of animals at 1st week (O1), 2nd week (O2), 4th week (O4) and 8th week (O8) after CUUO. Blood pressure was measured, renal arterial trees and glomeruli were assessed quantitatively, and renovascular three-dimensional reconstruction was performed on all groups. Glomerular ultrastructural changes were examined by transmission electron microscopy. The results showed that the systolic blood pressure was significantly increased in the obstructed groups (O1, O2, O4 and O8). Three-dimensional reconstruction showed sparse arterial trees in the O8 group, and a tortuous and sometimes ruptured glomerular basement membrane was found in the O4 and O8 groups. Furthermore, epithelial media thickness and media/lumen ratio were increased, lumen diameters were decreased, and the cross-sectional area of the media was unaltered in the segmental renal artery, interlobar artery and afferent arterioles, respectively. In conclusion, renal arterial trees and glomeruli were dramatically altered following CUUO and the changes may be partially ascribed to vascular remodeling. Elucidation of the molecular mechanisms of renovascular morphological alterations will enable the development of potential therapeutic approaches for hydronephrosis.

Clinical significance of the distribution of C4d deposits in different anatomic compartments of the allograft kidney.

Diffuse C4d deposition in peritubular capillaries is a well-recognized marker of antibody-mediated rejection. The significance of staining patterns that are focal or affect non-peritubular capillary compartments is less well defined. Paired frozen section and paraffin-embedded tissue stains were performed in 52 kidney allograft biopsies, and correlated with clinicopathologic parameters. Diffuse peritubular capillary C4d deposits were more often seen in frozen sections (22/52, 43% frozen tissue vs 10/52, 19% paraffin-embedded tissue), whereas focal staining was observed more frequently within paraffin sections (13/52, 25% paraffin-embedded tissue vs 7/52, 14% frozen tissue). In biopsies taken from patients with a history of donor-specific antibodies, diffuse, focal and negative peritubular capillary C4d staining patterns were seen in 11/14 (79%), 1/14 (7%) and 2/14 (14%) of frozen biopsies vs 5/14 (36%), 6/14 (43%) and 3/14 (21%) of paraffin-embedded biopsies. Transplant glomerulopathy score in paraffin-embedded biopsies was higher in specimens with vs without glomerular basement membrane C4d staining (1.5+/-0.8 vs 1.0+/-0.6, P=0.03). Tubular basement membrane staining was present in 4% paraffin-embedded and 48% frozen specimens independent of tubular atrophy. Arteriolar hyalinosis score in paraffin-embedded specimens was higher in biopsies with vs those without arteriolar C4d deposits (1.3+/-0.9 vs 0.9+/-0.8, P=0.04). Arterial staining was unrelated to the degree of intimal thickening. In conclusion, peritubular capillary deposits correlate well with circulating donor-specific antibody. For paraffin-embedded tissue, combining the results of focal and diffuse staining allows a diagnostic sensitivity comparable to diffuse staining in frozen tissue. Finally, C4d deposits preferentially in lesions of chronic transplant glomerulopathy and arteriolar hyalinosis.

Pathogenesis of extra efferent vessel development in diabetic glomeruli.

The development of extra efferent vessels (EEV) is a little-known feature of diabetic glomerulopathy. The only previous large study [Min W, Yamanaka N. Three-dimensional analysis of increased vasculature around the glomerular vascular pole in diabetic nephropathy. Virchows Archiv A Pathol Anat 1993; 423:201-7] known to us found that up to 5 EEV per glomerulus (glom) each drained a separate lobule. Most EEV connected to the second- and third-order branches of the afferent arteriole (AA), and drained into peritubular capillaries. Although not so stated, the illustrations suggested that some EEV could be shunts, and thus detrimental to glom function, and possibly glom health. There was no correlation between the unquantitated presence of increased EEV at the vascular pole (VP) and the severity of the major diabetic glomerular (glom) lesions. The authors opined that efferent arteriole (EA) stenosis by insudative lesions (IL) stimulated the formation of EEV. To confirm and extend these findings, we have repeated the study in 18 diabetic cases with mild to severe, but not end-stage, diffuse and nodular lesions (DL and NL), 8 controls, and the 2 normal traumatic nephrectomy cases. Up to 18 EEV per glom were found in diabetic cases along with occasional EEV in controls. EEV contained muscle and were almost identical to the EA in structure. Nearly all EEV connected with efferent glom capillaries at the VP, where they exited the glom through apparently preexisting gaps in the Bowman's capsule and/or glomerular capillary basement membranes (BCBM/GCBM). The EA exited through a similar gap, so the exit of EEV was accomplished without altering the anatomical relationships between the exiting vessels and the components of the VP thought to be important in the control of glom outflow. The largest number of EEV occurred in long-standing T2DM cases with mild to moderate DL and NL. Complete photographic glom reconstructions revealed numerous anastomoses among efferent glom capillaries in normal and diabetic gloms with mild to moderate DL and NL. No disproportionately dilated EEV were seen. The findings just cited confirm that EEV are common and surprisingly numerous in diabetic gloms. They suggest that EEV formation served to preserve glom function, and that EEV could neither shunt nor restrict glom outflow locally. In our opinion, the formation of EEV represents a significant, possibly hemodynamically induced, remodeling of the glom that should be added to the list of changes that occur in diabetes. It is hypothesized that EEV develop because of increased glom inflow, and that the latter may be attributable to AA muscle damage that impairs its contractile ability.