Ureteric bud derivatives express angiotensinogen and AT1 receptors.

Inactivation of the renin-angiotensin system interferes with the morphogenesis of the renal medulla. Thus ureteric bud (UB) derivatives may be a target for angiotensin production and action. To begin to test this hypothesis, we examined the cellular expression of angiotensinogen (Ao) and AT(1) receptor proteins during rat metanephrogenesis by immunohistochemistry. In addition, we tested whether UB-derived cells in culture express the Ao and AT(1) proteins. On embryonic day E15, Ao and AT(1) are expressed in the UB branches and stromal mesenchyme. S-shaped bodies, including the vascular cleft, express AT(1) but not Ao. The metanephric mesenchyme and pretubular aggregates are Ao negative and AT(1) negative. Expression of Ao and AT(1) in UB branches and ampullae is also observed on E16. However, UB expression of Ao is transient and is no longer detectable in the developing distal nephron beyond E17. On E17, both Ao and AT(1) are expressed in capillary loop glomeruli and proximal tubules, whereas UB branches express AT(1) only. By E18, the majority of Ao immunoreactivity is clustered in terminally differentiated proximal tubules, whereas AT(1) receptors are expressed in both proximal and distal nephron segments. The specificity of Ao and AT(1) staining was documented by the elimination/attenuation of immunoreactivity after preadsorption of the primary antibodies with their respective antigens. Consistent with the in vivo findings, the AT(1) protein is abundantly expressed in cellular lysates of mouse UB (E11.5) and IMCD3 (adult) cells. Moreover, AT(1) receptors in UB and IMCD3 cells are functional, since angiotensin II treatment elicits the tyrosine phosphorylation of the mitogen-activated protein kinases, ERK1/2. To our knowledge, this is the first demonstration of Ao and AT(1) protein expression in the developing distal nephron. Angiotensin II may have a paracrine role in the ontogeny of the collecting system.

Bradykinin B2 null mice are prone to renal dysplasia: gene-environment interactions in kidney development.

Congenital abnormalities of the kidney and urinary tract are a common cause of end-stage renal disease in children. Host and environment factors are implicated in the pathogenesis of aberrant renal development. However, direct evidence linking gene-environment interactions with congenital renal disease is lacking. We report an animal model of renal dysgenesis that is dependent on a defined genetic defect and specific embryonic stressor. Specifically, mice that are deficient in the bradykinin type 2 receptor gene (B(2)) and salt loaded during embryogenesis acquire an aberrant kidney phenotype and die shortly after birth. In contrast, B(2) mutant mice maintained on normal sodium intake or salt-loaded wild-type mice do not develop kidney abnormalities. The kidney abnormality is evident histologically on embryonic day 16, shortly after the onset of metanephric B(2) gene expression, and consists of distorted renal architecture, foci of tubular dysgenesis, and cyst formation. The dysplastic tubules are of distal nephron origin [Dolichos biflorus agglutinin (DBA)- and aquaporin-2 (AQP2) positive, and angiotensinogen negative]. Neonatal antihypertensive therapy fails to ameliorate the renal abnormalities, arguing against the possibility that the nephropathy is a consequence of early hypertension. Moreover, the nephropathy is intrinsic to the embryo, because B(2) homozygous offspring from heterozygous parents exhibit the same renal phenotype as offspring from homozygous null parents. Further characterization of the renal phenotype revealed an important genetic background effect since the penetrance of the congenital nephropathy is increased substantially upon backcrossing of 129/BL6 B(2) mutants to a uniform C57BL/6J. We conclude that the type 2 bradykinin receptor is required for the maintenance of metanephric structure and epithelial integrity in the presence of fetal stress. This study provides a "proof-of-principle" that defined gene-environment interactions are a cause of congenital renal disease.

Acute tubulointerstitial nephritis after wasp stings.

A 61-year-old Caucasian man presented with acute renal failure after multiple wasp stings. The patient required dialysis support temporarily. Work-up failed to show rhabdomyolysis or hemolysis and a kidney biopsy revealed acute allergic interstitial nephritis. The patient's renal function recovered completely after a short course of steroid therapy. Acute renal failure after wasp stings is typically caused by acute tubular necrosis in the setting of hemolysis or rhabdomyolysis. Compared with previously reported cases of acute renal failure associated with bee stings, our patient is unique in that his renal failure was caused by a hypersensitivity reaction apparently to the wasp venom.

Cytotoxicity of myeloma light chains in cultured human kidney proximal tubule cells.

We evaluated the effect of eight species of light chains on cultured human kidney proximal tubule cell proliferation. Exposure to light chains for 48 hours caused dose-dependent inhibition in tritium ((3)H)-thymidine incorporation by simian virus 40 immortalized human proximal tubule cells, although the effect was variable among different species of light chains. We studied cytotoxic effects of selected toxic light chains in further detail. Two of these light chains caused significant DNA degradation. A lambda-light chain caused lactate dehydrogenase release from exposed cells at 48 hours, but not at 24 hours. Cytomorphological and electron microscopic examination of cells exposed to light chains for 24 hours showed condensed nuclei, cell detachment, paucity of mitotic activity, and apoptosis, and at 48 hours of exposure, changes consistent with necrosis. Apoptosis assay by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method showed a sixfold increase in the number of apoptotic cells exposed to the same lambda-light chain for 24 hours. Rhodamine-phalloidin staining showed variable but significant disruptions in the actin cytoskeleton. These studies show that some myeloma light chains are toxic to cultured human proximal tubule cells and induce cytoskeletal injury and DNA damage consistent with apoptosis followed by secondary necrosis. Direct proximal tubule cell toxicity may be an important mechanism of renal involvement in multiple myeloma.

X-linked Alport syndrome in females.

Alport syndrome (AS) is in the differential diagnosis of hematuria. Variability in clinical presentation and in the ultrastructural changes of the glomerulus can make the diagnosis of AS a challenge in female patients. The purpose of this report is to present immunostaining for glomerular basement membrane (GBM) expression of alpha5(IV) as an adjunctive diagnostic method. Renal biopsy specimens from eight female patients with clinical presentation suggestive of AS were studied. The patients were between 7 and 36 years of age; six were between 12 and 15 years. Light microscopy and immunohistochemistry using a monoclonal antibody to alpha5(IV) were performed. Controls showed a continuous linear pattern along the GBM in normal kidneys and absence in renal biopsy specimens from male X-linked AS patients. To express the variability of the ultrastructural GBM changes among the patients in the series, we developed a semi-quantitative Alport Index, obtained by quantification of severity and extent of ultrastructural GBM changes. With immunohistochemistry, we showed an interrupted, discontinuous linear pattern for alpha5(IV) in glomeruli from the eight patients in the series, confirming the diagnosis of X-linked AS. The ultrastructural Alport Index varied between 6 and 47, showing the heterogeneity in the severity of the GBM changes, even among the six patients aged between 12 and 15 years. In three of the eight biopsy specimens, the predominant change was thin GBM, and the Alport Index was below 20. Immunohistochemistry for alpha5(IV) in renal biopsy specimens can identify female patients heterozygous for X-linked AS. In this series, the method led to the diagnosis of AS in female patients in whom the predominant ultrastructural change was thin basement membrane.

An 82-year-old woman with carcinomatosis.

An 82-year-old woman with breast carcinoma died with carcinomatosis, confirmed at autopsy. An unexpected finding was the "linitis plastica" aspect of the stomach, resulting from diffuse tumor infiltration. The coexistence of two different primary tumors was ruled out with data obtained by immunohistochemistry and presented at Tulane Pathology Grand Rounds.

Renal biopsy in a child with nephrotic syndrome.

A 6-year-old girl with nephrotic syndrome was treated with prednisone, without response. A renal biopsy was obtained. Following the format used at the Tulane Renal Biopsy Conferences, the clinical presentation, differential diagnosis and clinical discussion in this young patient will be presented first. The second part will include the renal biopsy findings, the final diagnosis and the pathology discussion.

Renal biopsy in a young man with hematuria.

A 24-year-old man was referred for evaluation of microscopic hematuria. Urologic work-up was unremarkable. A renal biopsy was performed.

A young man with acute renal failure.

A 34-year-old man, over a 2-week period, had an increase in serum creatinine from 5.0 mg/dL to 11.0 mg/dL. A renal biopsy was performed.

A 31-year-old woman with lupus erythematosus and fatal multisystem complications.

A 31-year-old woman with systemic lupus erythematosus presented with respiratory and renal symptoms followed by abdominal pain and seizure. Clinical diagnoses of lupus pneumonitis, nephritis, vasculitis, and cerebritis were made. The patient had a progressively downhill course with pancytopenia and hemolysis treated with aggressive immunosuppressive therapy and extended plasmapheresis. Lupus pneumonitis leading to diffuse alveolar damage was the immediate cause of death. Diffuse proliferative lupus nephritis was seen in the biopsy, and the autopsy demonstrated thrombotic microangiopathy. Extra-renal complications of lupus and response to therapy are discussed in the format of a Tulane Clinicopathologic Conference.

An 81-year-old woman with an abdominal mass.

An 81-year-old woman was admitted with a large abdominal mass that had grown rapidly over the previous few months. The differential diagnosis, pathology, and treatment of such masses are discussed.

Systemic amyloidosis associated with hepatocellular carcinoma. Case report and literature review.

We describe the case of a male patient with biopsy-proven non-resectable liver adenoma at age 32 who presented 17 years later with hepatocellular carcinoma and nephrotic syndrome. Autopsy demonstrated systemic amyloidosis A. Review of the medical literature disclosed only three previous published cases of liver tumors associated with systemic amyloidosis. The association of non-hematologic neoplasias with systemic amyloidosis is rare and our literature review revealed only three cases of systemic amyloidosis in patients with liver tumors. We present here the case of a patient with apparent transition of liver adenoma to hepatocellular carcinoma with associated systemic amyloidosis.

Alport disease: a review of the diagnostic difficulties.

In patients with familial hematuria, ultrastructural study of the renal biopsy has been the gold standard for the diagnosis of Alport disease, based on characteristic findings of glomerular basement membrane thickening due to reduplication of the lamina densa. But the diagnosis has difficulties as not all biopsies from Alport disease patients have these structural changes. In adult female patients or in children, extensive thinning of the basement membrane can be the major abnormality by electron microscopy. Until the genetic mutation of collagen IV responsible for Alport disease can be demonstrated in all patients, the diagnosis will continue to be a challenge at the clinical and at the ultrastructural levels.

Value of electron microscopy in the diagnosis of childhood nephrotic syndrome.

The value of the ultrastructural study of the renal biopsy was investigated in a series of pediatric patients with nephrotic syndrome. Forty-eight cases of renal biopsies with clinical data were reviewed and divided into diagnostic groups. The contribution of electron microscopy to the final diagnosis was graded as essential-diagnosis could not be reached without it; supportive-it increased the level of confidence in the final diagnosis; and noncontributory. In this series of renal biopsies from 48 children with nephrotic syndrome resistant or nonresponsive to therapy, the most frequent diagnosis was minimal change disease, present in 42% of the patients. The contribution of the electron microscopic study to the final diagnosis was essential in 73% of the series, and was supportive in a further 27%. Therefore, it is concluded that the ultrastructural study was an essential component in the study of the renal biopsy in children with nephrotic syndrome, suggesting that electron microscopy needs to continue to be performed for all these patients.

Apparent progression of acute glomerulonephritis to dense deposit disease.

One week after the diagnosis of meningococcal meningitis, an 8-year-old boy presented with acute renal failure and hypocomplementemia. A renal biopsy showed "postinfectious glomerulonephritis" and acute tubular necrosis. Hematuria, proteinuria, and low complement levels persisted, and 2 years later a follow-up renal biopsy revealed dense deposit disease. The apparent progression of postinfectious glomerulonephritis to dense deposit disease as observed in this patient has not been previously described.

Fetal ontogeny and role of metanephric bradykinin B2 receptors.

Previous studies in rats have shown that blockade of bradykinin B2 receptors (B2R) in combination with a high-salt intake during gestation result in poor postnatal survival and long-term hypertension in the offspring. In this study, we examined the fetal ontogeny of B2R and determined the consequences of gestational B2R blockade and high salt on kidney development. B2R gene expression is induced on embryonic day (E16) of fetal metanephrogenesis and remains sustained until term. The earliest expression of the B2R protein is observed on apical membranes of ureteric bud branches and in capillary loop stage glomeruli. By the end of gestation, B2R becomes restricted to more-differentiated tubules in the deep cortex and medulla. Pairs of rats on normal (0.12 mmol/g) or high (0.84 mmol/g) salt diets were mated at 14 weeks of age. The B2R antagonist, Icatibant (previously known as Hoe-140) (300 nmol/kg per day) or saline (vehicle) was infused intraperitoneally during gestation via osmotic minipumps. Fetuses were examined on E20 (n=27-36 per group). No significant differences in litter size or body weight were observed among the groups. Combined high-salt and Icatibant treatment caused aberrant fetal renal development characterized by tubular dysgenesis, widened stromal mesenchyme, and glomerular cysts. The dysgenetic tubules stained positively for the distal nephron lectin, Dolichos biflorus, and exhibited enhanced Bax expression and apoptosis. Renal microvascular development, the number of mature glomeruli, and percentage of proliferating glomerular cells were not affected. Gestational Icatibant or high salt alone had no deleterious effects on fetal nephrogenesis. We conclude that gestational blockade of the kallikrein-kinin system impairs fetal nephrogenesis if combined with an intrauterine stressor such as high-salt intake. B2R may play a protective role during segmental nephron differentiation.

Quantitative reverse transcription polymerase chain reaction shows that ethanol enhances interleukin-6 mRNA expression in cultured mesangial cells.

IgA nephropathy, a form of mesangial glomerulonephritis, is associated with chronic ethanol ingestion in humans and in a rat model. We investigated the hypothesis that ethanol has a direct effect on a mesangial cell cytokine, interleukin-6 (IL-6). We measured IL-6 mRNA in cultured mesangial cells using a novel method, quantitative reverse transcription-polymerase chain reaction (Q-RT-PCR). Primers were used to amplify a 346-bp segment. To quantify the results, we generated an internal standard using site-directed mutagenesis which resulted in a restriction site for EcoRI, absent in target IL-6 cDNA. In the presence of the same primers, the mutated internal standard (exogenous template) amplifies with equal efficiency as the target IL-6 cDNA. Q-RT-PCR, using 250 ng of total RNA, showed that after ethanol incubation, IL-6 mRNA was 65 (+/-30) attomol, a 1.5-fold increase from 44 (+/-28) attomol in control cells. This study shows that in vitro, ethanol enhances IL-6 mRNA expression in rat mesangial cells.

Evaluation of lupus nephritis during pregnancy by renal biopsy.

Patients with lupus nephritis frequently exhibit increasing proteinuria, hypertension and deterioration of renal function due to either active lupus nephritis, chronic lupus nephritis and/or superimposed preeclampsia during pregnancy. Percutaneous renal biopsies were therefore performed in 3 women with systemic lupus erythematosus during pregnancy and immediately postpartum in a fourth woman to evaluate their renal disease during pregnancy. Mean serum creatinine at renal biopsy was 2.9 mg/dl, with a mean creatinine clearance of 66 ml/min and protein excretion of 5.3 g/day. All patients had grade IV lupus nephritis and received pulse methylprednisolone immediately; 3 received cyclophosphamide. All 3 patients with crescent formation developed endstage renal disease within 3 years. The fourth patient has normal renal function 3 years after biopsy. Percutaneous renal biopsies during pregnancy in women with lupus nephritis provide an accurate histopathologic diagnosis and are important in providing appropriate therapy, counseling and prognosis.