5/6 nephrectomy as a validated rat model mimicking human warfarin-related nephropathy.

BACKGROUND/AIMS: We previously reported that patients with chronic kidney disease (CKD) receiving warfarin therapy and whose international normalized ratio increases to >3.0 may develop acute kidney injury (AKI) as a result of glomerular hemorrhage and formation of obstructive red blood cell (RBC) casts. We named this condition warfarin-related nephropathy (WRN). We also previously reported that acute excessive anticoagulation with brodifacoum (superwarfarin) induces AKI in 5/6 nephrectomy (5/6NE) rats. Limitations of the brodifacoum model precluded a careful assessment of dose-response relationships. METHODS: Warfarin treatment was used in 5/6NE. RESULTS: Herein we report that warfarin treatment of 5/6NE rats resulted in a dose-dependent increase in serum creatinine (SC). The increase in SC following warfarin treatment was greater at 3 and 19 weeks after the ablative surgery, than that observed 8 weeks after the ablative surgery. The SC increase was correlated with the prothrombin time increase. Morphologically, 5/6NE, but not control rats, had acute tubular injury with RBC and RBC casts in the tubules. Treatment with vitamin K prevented SC increase and morphologic changes in the kidney associated with warfarin treatment. A single episode of WRN did not affect the progression of CKD in 5/6NE. CONCLUSION: (1) The 5/6NE model of CKD is an appropriate animal model to study the pathogenesis of WRN. (2) The pharmacokinetics of warfarin is better suited to the study of WRN than that of brodifacoum. (3) The more advanced stages of 5/6NE are more susceptible to WRN than the earlier stages. (4) Vitamin K treatment prevents WRN.

Discrepancies in glomerular and tubulointerstitial/vascular immune complex IgG subclasses in lupus nephritis.

BACKGROUND AND OBJECTIVES: Lupus nephritis is characterized by glomerular and extraglomerular immune complex deposition in the kidney. It is unclear whether the same circulating immune complexes deposit in the glomeruli and in extraglomerular structures, or whether they are pathogenetically different. Differences in the IgG subclass composition may point towards different pathways in the formation of glomerular and extraglomerular immune complexes. Therefore we investigated IgG subclass distribution in the immune complex deposits at these anatomic sites. DESIGN: A total of 84 biopsies diagnosed as lupus nephritis and classified according to the International Society of Nephrology/Renal Pathology Society (ISN/RPS) 2003 classification, were examined by direct immunofluorescence staining for IgG subclasses. The IgG subclass composition in the glomerular, tubular basement membrane (TBM) and vascular wall deposits was compared. We also correlated the presence/absence of interstitial inflammation and IgG subclasses in the TBM and vascular deposits. Lastly, we looked for correlation between staining for IgG subclasses and complement C1q and C3 staining. RESULTS: IgG staining was present in the TBM in 52/84 biopsies, and in the vascular walls in 40/84 biopsies. IgG subclass distribution was discrepant between glomerular and TBM deposits in 36/52 biopsies, and between glomerular and vascular deposits in 27/40 biopsies. Interstitial inflammation did not correlate with the presence of IgG staining or distribution of IgG subclasses in the TBM. Interstitial inflammation was more common in biopsies of African-American patients than Caucasian patients. The IgG subclass staining correlated with C1q staining in all the three compartments. CONCLUSIONS: The antibody composition of the glomerular and extraglomerular immune complex deposits appear to differ from each other. They may not represent the same preformed immune complexes from the circulation. It is likely that their pathogenesis and site of formation are different.

De novo thrombotic microangiopathy in renal allograft biopsies-role of antibody-mediated rejection.

The most common cause of thrombotic microangiopathy (TMA) in renal allografts is thought to be calcineurin inhibitor toxicity. Antibody-mediated rejection (AMR) can also cause TMA, but its true impact on de novo TMA is unknown. In a retrospective review of renal allograft biopsies from January 2003 to December 2008 at our institution, we determined the prevalence of TMA in patients with C4d positive (n = 243) and C4d negative (n = 715) biopsies. Over 90% of patients received cyclosporine in both groups. De novo TMA was seen in 59 (6.1%) patients; most of them (55%) with C4d positive biopsy. Among patients with C4d positive biopsies, 13.6% had TMA, as compared to only 3.6% patients with C4d negative biopsies (p < 0.0001). Incidence of graft loss between C4d positive and C4d negative TMA groups was not significantly different, but 70% of patients with C4d positive TMA who received plasmapheresis had slightly lower graft loss rate. In biopsies with AMR-associated TMA, glomerulitis and peritubular capillaritis were significantly more prominent. AMR is the most common cause of TMA in renal allografts in our patient population. It is important to recognize AMR-related TMA because plasmapheresis treatment may be beneficial.

Acute humoral rejection of renal allografts in CCR5(-/-) recipients.

Increasing detection of acute humoral rejection (AHR) of renal allografts has generated the need for appropriate animal models to investigate underlying mechanisms. Murine recipients lacking the chemokine receptor CCR5 reject cardiac allografts with marked C3d deposition in the parenchymal capillaries and high serum donor-reactive antibody titers, features consistent with AHR. The rejection of MHC-mismatched renal allografts from A/J (H-2(a)) donors by B6.CCR5(-/-) (H-2(b)) recipients was investigated. A/J renal allografts survived longer than 100 days in wild-type C57BL/6 recipients with normal blood creatinine levels (28 +/- 7 micromol/L). All CCR5(-/-) recipients rejected renal allografts within 21 days posttransplant (mean 13.3 +/- 4 days) with elevated creatinine (90 +/- 31 micromol/L). The rejected allografts had neutrophil and macrophage margination and diffuse C3d deposition in peritubular capillaries, interstitial hemorrhage and edema, and glomerular fibrin deposition. Circulating donor-reactive antibody titers were 40-fold higher in B6.CCR5(-/-) versus wild-type recipients. Depletion of recipient CD8 T cells did not circumvent rejection of the renal allografts by CCR5-deficient recipients. In contrast, microMT(-/-)/CCR5(-/-) recipients, incapable of producing antibody, did not reject most renal allografts. Collectively, these results indicate the rapid rejection of renal allografts in CCR5(-/-) recipients with many histopathologic features observed during AHR of human renal allografts.

DPC4 gene in various tumor types.

We recently identified a novel tumor-suppressor gene, DPC4, at chromosome 18q21.1 and found that both alleles of DPC4 were inactivated in nearly one-half of the pancreatic carcinomas. Here, we analyzed 338 tumors, originating from 12 distinct anatomic sites, for alterations in the DPC4 gene. Sixty-four specimens were selected for the presence of the allelic loss of 18q and were further analyzed for DPC4 sequence alterations. An alteration of the DPC4 gene sequence was identified in one of eight breast carcinomas and one of eight ovarian carcinomas. These results indicate that whereas DPC4 inactivation is prevalent in pancreatic carcinoma (48%), it is distinctly uncommon (< 10%) in the other tumor types examined. The tissue restriction of alterations in DPC4, as in many other tumor-suppressor genes, emphasizes the complexity of rate-limiting checkpoints in human tumorigenesis.

Meconium-induced umbilical cord vascular necrosis and ulceration: a potential link between the placenta and poor pregnancy outcome.

The literature lacks epidemiologic study of pregnancy outcome with light-microscopic meconium-related lesions. We recently described previously unreported meconium-induced necrosis of placental and umbilical cord vessels and hypothesized that the lesions represent preceding vasocontraction and fetal hypoperfusion. Preliminary experiments then confirmed that meconium produces vasocontraction in isolated umbilical venous tissue. In the present study, we examined whether clinically meaningful abnormalities occur with these vascular signs of remote fetal meconium discharge. In a light-microscopic review of 1100 meconium-stained placentas, we found ten with meconium-induced vascular necrosis. In six of these ten cases, fetal distress necessitated cesarean delivery. Seven newborns had Apgar scores of 3 or less at 1 minute, and each of the seven cases tested had umbilical arterial pH less than 7.19. Because seven of the ten infants were born after December 1, 1989, clinical follow-up was limited. One died, another has neurodevelopmental deficiency, and a third has experienced enlargement of head circumference from the 50th percentile at birth to the 95th percentile at 10 months of age. Two placentas had umbilical cord ulceration, a lesion that has rarely been reported in the literature. We conclude that meconium-induced vascular necrosis seems to be a meaningful, detrimental lesion.

Outcome of renal transplantation in fibrillary glomerulonephritis.

Fibrillary glomerulonephritis (FGN) is a rare but progressive glomerular disease usually with end-stage renal disease (ESRD) developing within months or few years following the diagnosis. Little is known about the outcome of renal transplantation in patients with ESRD due to FGN. We report four patients with FGN who received renal allografts. Two patients developed recurrent FGN in their grafts. One patient was diagnosed to have recurrent FGN 9 years post-transplant, and lost his graft 4 years thereafter. Another patient had recurrent disease 2 years post-transplant but has stable graft function after 7 years. One patient died with normal renal allograft function 7 years following transplantation. The fourth patient has chronic transplant nephropathy 34 months post-transplant without evidence of recurrent FGN. A literature review revealed 10 additional patients who received 11 renal allografts due to ESRD caused by FGN. Four of these 10 patients had biopsy-proven recurrence (one patient in two subsequent grafts), but this caused graft loss only in 2 patients 56 months and 7 years post-transplant, respectively. The earliest recurrence was diagnosed 2 years post-transplant. We conclude that although the recurrence rate of FGN in renal transplants is high (around 50%), the recurrent disease has a relatively benign course and prolonged graft survival is possible.

Chronic effect of pneumoperitoneum on renal histology.

BACKGROUND AND OBJECTIVE: Transient intraoperative oliguria is a constant phenomenon during laparoscopic procedures. Laboratory studies have demonstrated that this effect is secondary to a decrease in renal blood flow caused by the pneumoperitoneum. With the advent of laparoscopic harvest of the kidney for renal transplantation, a concern is that increased intra-abdominal pressure may compound the effect of acute cold and warm renal ischemia during transplantation. Acute transient renal ischemia can produce chronic sclerosing histopathologic changes in native kidneys which are similar to those seen in chronic allograft rejection. The effect of positive-pressure abdominal pneumoperitoneum (15 mm Hg) on native kidneys was examined using a rodent model. The effects on renal function and histologic features were also studied. MATERIALS AND METHODS: Twenty-four Harlan Wistar-Furth rats were divided into four groups: controls, 1-hour pneumoperitoneum-91-day survival, 5-hour pneumoperitoneum-91-day survival, and 5-hour pneumoperitoneum-7-day survival. Control animals underwent placement of the Veress needle and anesthesia but no induction of pneumoperitoneum. At the time of sacrifice, blood was sampled for serum creatinine measurement. Both kidneys were harvested for frozen and permanent section and stained using hematoxylin and eosin. Specimens were graded for inflammatory and ischemic/sclerotic changes in the interstitium, tubules, glomeruli, and vasculature by a renal pathologist using a histologic score (0-3). RESULTS: In all groups, at a sacrifice interval of either 1 week or 3 months, there were no statistical differences in the histologic score, serum creatinine concentration, or renal weight. CONCLUSIONS: In a rodent model, no signs of chronic ischemic histologic changes were detected for a period of 3 months after up to 5 hours of pneumoperitoneum. As well, there was no change in the serum creatinine concentration.

Placental cryptococcosis in a mother with systemic lupus erythematosus.

There are many pregnant mothers who have acquired immunodeficiency syndrome or who require immunosuppressive therapy for sundry reasons. Despite this, we have been able to find only one English-language report of placental cryptococcosis. We have had an opportunity to treat a pregnant mother who suffered from cryptococcal meningitis that complicated steroid treatment for lupus erythematosus. At 31 weeks' gestation, fetal distress necessitated delivery by cesarean section. The placenta had focally abundant intervillous and perivillous cryptococcal yeast cells, but there was no chorioamnionitis or villitis. Although there were no clinical or placental signs of transplacental infection, immunohistochemical labeling of villous stromal cells showed a conspicuously increased number of fetal macrophages.

Cell proliferation in the developing human kidney.

In a previous study, utilizing antibodies to proliferating cell nuclear antigen (PCNA), we determined the proliferation index (PI) (percentage of PCNA-positive cells) of intrinsic renal cell populations in the normal adult and pediatric kidney. We have found that the PI in both adult and pediatric kidneys was very low (below 0.5 in all examined cell populations). In our present study, we investigated cell proliferation in the developing human kidney with an antibody to PCNA. Histologically normal kidneys were collected from 25 fetuses (spontaneous abortions and stillborns) ranging from 10 wk of gestation to term. Immature mesenchyme (blastema), immature early tubules, ampulla of ureteric bud, proximal tubules, Tamm-Horsfall protein (THP)-positive tubules, distal tubules, collecting ducts, and glomeruli were evaluated separately. The PI for each cell population was calculated. The PI of immature early tubules remains high (33-43) throughout embryonic life. The PI of blastemal cells is initially similarly high, but gradually decreases starting from the second trimester. The PI of THP-positive tubules, distal tubules, collecting ducts, and glomeruli starts out relatively high (5.9, 8.6, 6.0, and 12.4, respectively) and decreases gradually as term approaches (1.8, 1.3, 1.2, and 1.4, respectively). Interestingly, as soon as proximal tubules become differentiated (appearance of light microscopic features of proximal tubular epithelium with TP lectin positive brush border), their PI becomes very low (below 1) irrespective of the age of the kidney. This is the first quantitative study to show changes of the PI in various renal cell populations during human nephrogenesis. These changes in the PI relate to the stage of differentiation of the developing nephron segments.