Rationale and design of the Japanese Biomarkers in Nephrotic Syndrome (J-MARINE) study

INTRODUCTION

Disease subtyping and monitoring are essential for the management of nephrotic syndrome (NS). Although various biomarkers for NS have been reported, their clinical efficacy has not been comprehensively validated in adult Japanese patients.

METHODS

The Japanese Biomarkers in Nephrotic Syndrome (J-MARINE) study is a nationwide, multicenter, and prospective cohort study in Japan, enrolling adult (≥18 years) patients with minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), membranous nephropathy (MN), membranoproliferative glomerulonephritis (MPGN), C3 glomerulopathy (C3G), and lupus nephritis (LN). Baseline clinical information and plasma and urine samples will be collected at the time of immunosuppressive therapy initiation or biopsy. Follow-up data and plasma and urine samples will be collected longitudinally based on the designated protocols. Candidate biomarkers will be measured: CD80, cytotoxic T-lymphocyte antigen 4, and soluble urokinase plasminogen activator receptor for MCD and FSGS; anti-phospholipase A2 receptor and thrombospondin type-1 domain-containing protein 7A antibodies for MN; fragment Ba, C3a, factor I, and properdin for MPGN/C3G; and CD11b, CD16b, and CD163 for LN. Outcomes include complete and partial remission, relapse of proteinuria, a 30% reduction in estimated glomerular filtration rate (eGFR), eGFR decline, and initiation of renal replacement therapy. The diagnostic accuracy and predictive ability for clinical outcomes will be assessed for each biomarker.

RESULTS

From April 2019 to April 2023, 365 patients were enrolled: 145, 21, 138, 10, and 51 cases of MCD, FSGS, MN, MPGN/C3G, and LN, respectively.

CONCLUSION

This study will provide valuable insights into biomarkers for NS and serve as a biorepository for future studies.

Urine albumin-to-creatinine ratio diurnal variation rate predicts outcomes in idiopathic membranous nephropathy

BACKGROUND

Idiopathic membranous nephropathy (IMN) is a leading cause of end-stage renal disease (ESRD). The purpose of this study was to evaluate whether urinary albumin-to-creatinine ratio (UACR) diurnal variation rate calculated by spot urinary protein test predicts 1-year nephrotic outcomes as a biomarker of proteinuria severity in patients with IMN.

METHODS

Patients' baseline demographics, blood and urinary biomarkers, and clinical and pathological characteristics were collected retrospectively. Urine samples were collected at 7:00 (before breakfast) and 19:00 (after dinner) to calculate the UACR diurnal variation rate. A prediction model for no remission (NR) was developed statistically based on differences between prognosis groups. Receiver operating characteristic curve (ROC) analysis was performed to evaluate prediction abilities and determine optimal cut-off points of the model and UACR diurnal variation rate alone.

RESULTS

The formula for calculating the probability of NR was exp(L)/(1 + exp(L)), where the linear predictor L =  - 22.038 + 0.134 × Age (years) + 0.457 × 24-h urinary protein + 0.511 × blood urea nitrogen (BUN) + 0.014 × serum uric acid (SUA) + 2.411 if glomerular sclerosis + 0.816 × fasting blood glucose (FBG)-0.039 × UACR diurnal variation rate (%). Optimal cut-off points for NR prediction by the final model and UACR diurnal variation rate alone were 0.331 and 58.5%, respectively. Sensitivity and specificity were 0.889 and 0.859 for the final model, and 0.926 and 0.676 for UACR diurnal variation rate alone.

CONCLUSION

UACR diurnal variation using spot urinary protein is a simpler way to predict nephrotic outcomes and is a highly sensitive screening tool for identifying patients who should undergo further comprehensive risk assessment.

Role of Serum and Urine Biomarkers (PLA2R and THSD7A) in Diagnosis, Monitoring and Prognostication of Primary Membranous Glomerulonephritis

Differentiating primary and secondary membranous glomerulonephritis (MGN) using biomarkers for MGN is essential in patients' diagnosis, treatment and follow-up. Although biopsy has been the primary tool in making the diagnosis, not all patients can withstand it due to its invasive nature, and it cannot be used to monitor treatment. Hence, there is the need for less invasive or even non-invasive biomarkers for effective diagnosis, treatment monitoring and prognostication. This study aimed at providing an alternative way of differentiating primary and secondary MGN using enzyme-linked immunosorbent assay (ELISA) technique for serum and urine biomarkers (M-type phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A)) for prompt diagnosis, treatment and prognosis. A total of 125 subjects, including 81 primary and 44 secondary MGN subjects, were diagnosed from January 2012 to October 2019 at Hospital Serdang and Hospital Kuala Lumpur from which 69 subjects consisting of 45 primary and 24 secondary MGN subjects participated in the study. Of these, 13 primary MGN subjects were positive for both serum and urine anti-PLA2R antibodies (Ab) whereas only one secondary MGN subject associated with hepatitis B virus was positive for both serum and urine anti-PLA2R Ab. At the same time, anti-THSD7A Ab was found positive in four primary MGN subjects and two secondary MGN subjects with malignancy.

Spot urine protein/creatinine ratio as a reliable estimate of 24-hour proteinuria in patients with immunoglobulin A nephropathy, but not membranous nephropathy

BACKGROUND

Proteinuria is known to be associated with both kidney function deterioration and cardiovascular diseases. While proteinuria estimation from 24-h urine samples has traditionally been considered as the standard method for assessment of the degree of urinary protein excretion, sample collection is associated with several technical problems such as inaccurate collection and the potential spread of drug-resistant pathogens. Therefore, the spot urine protein/creatinine ratio (PCR) assessment is currently recommended as an alternative. While the utility of PCR has been validated, studies on the association between spot urine PCR and 24-h proteinuria (24HP) in patients with chronic glomerular nephritis (CGN) and nephrotic syndrome (NS) are limited. This study aimed to evaluate whether an estimated result from a spot urine PCR could sufficiently approximate the daily urine protein excretion amount from a 24-h urine sample in patients with immunoglobulin A nephropathy (IgAN), minimal change disease (MCD), and membranous nephropathy- nephrotic syndrome (MN-NS).

METHODS

The study participants included 161 patients with IgAN, MCD, or MGN-NS at the Jikei University Kashiwa Hospital and Kanagawa Prefecture Shiomidai Hospital. The correlation between spot urine PCR and a 24-h urine protein was investigated using linear regression analysis with Spearman's correlation (r) coefficient and intraclass correlation coefficient (ICC).

RESULTS

While high correlation coefficients (r = 0.86, P < 0.001) and substantial agreement (ICC: 0.806, P < 0.001) were observed in patients with IgAN, similar correlations were not observed in patients with MCD or MN-NS. In the patients with MCD, r was 0.53 (P < 0.001), which signified a slight correlation, and in the patients with MN-NS, r was 0.289 (P = 0.17), which was not statistically significant.

CONCLUSIONS

This study revealed that spot urine PCR is a reliable estimate of 24HP value in patients with IgAN. In contrast, there is a considerable difference between the daily urine protein excretion amount based on a 24-h urine sample and that which is calculated from spot urine PCR in patients with NS.

Light Chain Cast Nephropathy: Practical Considerations in the Management of Myeloma Kidney-What We Know and What the Future May Hold

PURPOSE OF REVIEW

To update and evaluate the current knowledge on pathogenesis and management of light chain cast nephropathy. Light chain cast nephropathy (LCCN) is the leading cause of acute renal failure in patients with multiple myeloma and is currently recognized as a myeloma defining event.

RECENT FINDINGS

The immunoglobulin free light chain plays an integral role in the pathogenesis of LCCN. The level of free light chain (FLC) in the blood and urine is directly associated with the risk of developing LCCN. Recovery of renal function is related to the speed and degree of the serum FLC reduction. Recently, two randomized trials using high cutoff dialyzer for the removal of serum FLC produced different results in terms of renal recovery. FLC plays a key role in the development and resolution of LCCN. Future therapies will aim to rapidly reduce its concentration or interrupt its interaction with Tamm-Horsfall protein.

Urinary Volatile Organic Compounds as Potential Biomarkers in Idiopathic Membranous Nephropathy

OBJECTIVE

To detect urinary volatile organic compounds (VOCs) in patients with idiopathic membranous nephropathy (iMN) and normal controls, and to examine whether or not urinary VOCs can act as biomarkers for the diagnosis of iMN independent of renal biopsy.

MATERIALS AND METHODS

Gas chromatography/mass spectrometry (GC/MS) was used to assess the urine collected from 63 iMN patients and 15 normal controls. The statistical methods of principal component analysis and partial least squares discriminant analysis were performed to process the final data in Common Data Format which were converted from GC/MS data.

RESULTS

Six VOCs in the urine samples of iMN patients exhibited significant differences from those of normal controls: carbamic acid monoammonium salt, 2-pentanone, 2,4-dimethyl-pentanal, hydrogen azide, thiourea, and 4-heptanone were significantly higher than in controls (p < 0.05).

CONCLUSIONS

Six urinary VOCs were isolated from patients with iMN using GC/MS. The analysis of urinary VOCs using GC/MS could be developed into a non-invasive method for the detection of iMN.

Different Effects of Tolvaptan in Patients with Idiopathic Membranous Nephropathy with Nephrotic Syndrome

This case report discusses the clinical indication for immunosuppressants in patients with idiopathic membranous nephropathy (IMN). Because this disease occasionally shows spontaneous remission, it is necessary to determine the predictive values for a therapeutic effect in order to provide appropriate treatment. Two distinct cases described herein illustrate the different effects of tolvaptan in responders and non-responders, according to the pre-treatment levels of AQP-2 immunostaining in the samples from renal biopsy and urinary levels of AQP-2 and osmolality, suggesting that these values may be useful predictors of response to tolvaptan in patients with nephrotic IMN.

Increased expression of lysosome membrane protein 2 in glomeruli of patients with idiopathic membranous nephropathy

Urinary microvesicles constitute a rich source of membrane-bound and intracellular proteins that may provide important clues of pathophysiological mechanisms in renal disease. In the current study, we analyzed and compared the proteome of urinary microvesicles from patients with idiopathic membranous nephropathy (iMN), idiopathic focal segmental glomerulosclerosis (iFSGS), and normal controls using an approach that combined both proteomics and pathology analysis. Lysosome membrane protein-2 (LIMP-2) was increased greater than twofold in urinary microvesicles obtained from patients with iMN compared to microvesicles of patients with iFSGS and normal controls. Immunofluorescence analysis of renal biopsies confirmed our proteomics findings that LIMP-2 was upregulated in glomeruli from patients with iMN but not in glomeruli of diseased patients (iFSGS, minimal change nephropathy, IgA nephropathy, membranoproliferative glomerulonephritis) and normal controls. Confocal laser microscopy showed co-localization of LIMP-2 with IgG along the glomerular basement membrane. Serum antibodies against LIMP-2 could not be detected. In conclusion, our data show the value of urinary microvesicles in biomarker discovery and provide evidence for de novo expression of LIMP-2 in glomeruli of patients with iMN.

Patient age and the prognosis of idiopathic membranous nephropathy

BACKGROUND

Idiopathic membranous nephropathy (IMN) is increasingly seen in older patients. However, differences in disease presentation and outcomes between older and younger IMN patients remain controversial. We compared patient characteristics between younger and older IMN patients.

METHODS

We recruited 171 Japanese patients with IMN, including 90 (52.6%) patients <65 years old, 40 (23.4%) patients 65-70 years, and 41 (24.0%) patients ≥ 71 years. Clinical characteristics and outcomes were compared between younger and older IMN patients.

RESULTS

During a median observation period of 37 months, 103 (60.2%) patients achieved complete proteinuria remission, which was not significantly associated with patient age (P = 0.831). However, 13 (7.6%) patients were hospitalized because of infection. Multivariate Cox proportional hazards models identified older age [adjusted hazard ratio (HR) = 3.11, 95% confidence interval (CI): 1.45-7.49, per 10 years; P = 0.003], prednisolone use (adjusted HR = 11.8, 95% CI: 1.59-242.5; P = 0.014), and cyclosporine used in combination with prednisolone (adjusted HR = 10.3, 95% CI: 1.59-204.4; P = 0.012) as significant predictors of infection. A <25% decrease in proteinuria at 1 month after immunosuppressive therapy initiation also predicted infection (adjusted HR = 6.72, 95% CI: 1.51-37.8; P = 0.012).

CONCLUSIONS

Younger and older IMN patients had similar renal outcomes. However, older patients were more likely to develop infection when using immunosuppressants. Patients with a poor response in the first month following the initiation of immunosuppressive therapy should be carefully monitored for infection and may require a faster prednisolone taper.

Kidney biopsy reveals metastatic adenocarcinoma of the appendix simulating nephrotic syndrome

Membranous glomerulonephritis (MGN) is among the most common causes of nephrotic syndrome in adults. The malignancy in presumed tumor-induced MGN has usually been diagnosed at the time the proteinuria is discovered. Here we report a 57-year-old male patient with a history of refractory pyuria and nephrotic syndrome. The kidney biopsy confirmed the diagnosis of not only MGN, but also metastasis of appendix adenocarcinoma. To our knowledge this is the first case report diagnosed as a metastatic malignancy from a kidney biopsy which no other imaging techniques were able to display.

[Clinical significance of detection of plasma and urine IgG4 in idiopathic membranous nephropathy]

OBJECTIVE

To investigate the possibility of IgG4/IgG as one of biomarkers to reflect disease activity and the relapse of idiopathic membranous nephropathy (IMN).

METHODS

Plasma and urine samples were obtained from patients with IMN (Twenty-four patients had follow-up data), minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) before immunosuppressive therapy. Concentrations of plasma and urine IgG4 and total IgG were detected by sandwich ELISA. The ratio of IgG4/IgG was calculated as the concentration of IgG4 divided by total IgG.

RESULTS

Both plasma and urine IgG4/IgG ratios were significantly higher in IMN group compared with MCD or FSGS group (both P<0.05). In IMN, both plasma and urine IgG4/IgG ratios in patients with nephritic syndrome were significantly higher versus those with subnephrotic proteinuria (P=0.063; P<0.05). Both plasma and urine IgG4/IgG ratios were significantly decreased with remission (P<0.05) and maintained or even increased with resistance to therapy. Patients who relapsed within 2 years had higher urine IgG4/IgG-ratios than those who had no relapse (P<0.05), and patients with urine IgG4/IgG-ratios≥9% upon renal biopsy had higher relapse tendency (P=0.071).

CONCLUSION

Both plasma and urine IgG4/IgG ratios might be a promising biomarker to reflect disease activity of IMN, and higher urine IgG4/IgG ratios might suggest higher relapse tendency.

Membranous nephropathy complicating nasopharyngeal carcinoma

The patient was a 38-year-old woman diagnosed with nephrotic syndrome. Steroid pulse therapy and mizoribine was started in late October 2002 and continued for about 10 months, but no apparent therapeutic effect was obtained. During this period, the patient was diagnosed with nasopharyngeal carcinoma. As nephrotic syndrome did not improve, renal biopsy was performed and membranous nephropathy (MN) was diagnosed. After resection of nasopharyngeal carcinoma was performed, the urinary protein level decreased rapidly. Since MN caused by nasopharyngeal carcinoma is very rare, this represents an interesting case of malignancy-associated MN.

Early initiation of tacrolimus or cyclophosphamide therapy for idiopathic membranous nephropathy with severe proteinuria

BACKGROUND

Early initiation of therapy is warranted for patients with idiopathic membranous nephropathy (IMN) who have severe proteinuria. Therapy with tacrolimus (TAC) or intravenous cyclophosphamide (CYC) may be an option in treating such patients.

METHODS

This prospective cohort study included patients with IMN whose daily proteinuria was greater than 6.0 g with 3-6 months observation of nonimmunosuppressive therapy. One cohort received prednisone combined with oral TAC (target trough blood level of 4-8 ng/mL) for 24 weeks. The other cohort received prednisone combined with intravenous CYC (750 mg/m2 body surface) every 2 weeks for the first 8 weeks and then once per 4 weeks for the next 16 weeks.

RESULTS

Thirty patients met criteria for enrollment, and 25 patients completed therapy. The results of the 24-week therapeutic period were complete remission (CR) 4 patients (30.8%) on CYC and 8 patients (66.7%) on TAC; partial remission (PR) 7 patients (53.8%) on CYC and 3 patients (25%) on TAC; no response 2 patients (15.4%) on CYC and 1 patient (8.3%) on TAC. The percentages of remission (either PR or CR) by 4 and 8 weeks were significantly higher in TAC group than in CYC group (p<or=0.05). The probability of CR was significantly higher in the TAC group than in the CYC group (p=0.018, by log-rank test).

CONCLUSION

Earlier initiation of therapy with TAC or intravenous CYC (combined steroid) for 24 weeks was useful for Chinese adults with IMN in inducing remission of severe proteinuria, and quicker remission was seen in TAC therapy.

Markedly Increased Urinary Preprohaptoglobin and Haptoglobin in Passive Heymann Nephritis: A Differential Proteomics Approach

Membranous nephropathy (MN), a common cause of idiopathic nephrotic syndrome in adults, remains a potentially devastating problem worldwide. At present, there is no reliable noninvasive method for predicting and/or monitoring this glomerular disease, and its pathophysiology remains poorly understood. In the present study, the urinary proteome profile of rats after 10 days of an induction of passive Heymann nephritis (PHN), which resembles human MN, was compared to that of the baseline (control) urine prior to the induction of PHN by anti-Fx1A injection. Each pool of PHN and control urine samples (n = 10 each) was labeled with different fluorescent dyes (Cy3 or Cy5), and equal amounts of the labeled proteins of both pools were resolved in the same 2D gel, together with an internal standard labeled with Cy2. Two-dimensional difference gel electrophoresis revealed a number of protein spots whose expression levels were altered during PHN. Eighteen protein spots with >1.5-fold changes and p < 0.05 were selected for subsequent identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. They were successfully identified as serum albumin precursor, alpha-1-antitrypsin, preprohaptoglobin, liver-regeneration-related protein, and transthyretin (which increased during PHN) and E-cadherin, MPP7, tropomyosin beta, kallikrein, and alpha-2u globulin (which decreased in the PHN urine). Among these proteins, the increase in urinary preprohaptoglobin has particularly drawn our attention because of its byproduct, haptoglobin (Hp), which is involved in the protection of tissue damage from hemoglobin-induced oxidative stress. Western blotting and enzyme-linked immunosorbent assay clearly showed a markedly increased level of Hp in the urine, but not in the serum, of the PHN animals. Our findings may lead to a significant advance in the attempt to define a new therapeutic target and/or novel biomarker for human MN.

Urine biomarkers predict the cause of glomerular disease

Diagnosis of the type of glomerular disease that causes the nephrotic syndrome is necessary for appropriate treatment and typically requires a renal biopsy. The goal of this study was to identify candidate protein biomarkers to diagnose glomerular diseases. Proteomic methods and informatic analysis were used to identify patterns of urine proteins that are characteristic of the diseases. Urine proteins were separated by two-dimensional electrophoresis in 32 patients with FSGS, lupus nephritis, membranous nephropathy, or diabetic nephropathy. Protein abundances from 16 patients were used to train an artificial neural network to create a prediction algorithm. The remaining 16 patients were used as an external validation set to test the accuracy of the prediction algorithm. In the validation set, the model predicted the presence of the diseases with sensitivities between 75 and 86% and specificities from 92 to 67%. The probability of obtaining these results in the novel set by chance is 5 x 10(-8). Twenty-one gel spots were most important for the differentiation of the diseases. The spots were cut from the gel, and 20 were identified by mass spectrometry as charge forms of 11 plasma proteins: Orosomucoid, transferrin, alpha-1 microglobulin, zinc alpha-2 glycoprotein, alpha-1 antitrypsin, complement factor B, haptoglobin, transthyretin, plasma retinol binding protein, albumin, and hemopexin. These data show that diseases that cause nephrotic syndrome change glomerular protein permeability in characteristic patterns. The fingerprint of urine protein charge forms identifies the glomerular disease. The identified proteins are candidate biomarkers that can be tested in assays that are more amenable to clinical testing.

Serial changes in urinary proteome profile of membranous nephropathy: implications for pathophysiology and biomarker discovery

Membranous nephropathy is one of the most common causes of primary glomerular diseases worldwide. The present study adopted a gel-based proteomics approach to better understand the pathophysiology and define biomarker candidates of human membranous nephropathy using an animal model of passive Heymann nephritis (PHN). Clinical characteristics of Sprague-Dawley rats injected with rabbit anti-Fx1A antiserum mimicked those of human membranous nephropathy. Serial urine samples were collected at Days 0, 10, 20, 30, 40, and 50 after the injection with anti-Fx1A (number of rats = 6; total number of gels = 36). Urinary proteome profiles were examined using 2D-PAGE and SYPRO Ruby staining. Quantitative intensity analysis and ANOVA with Tukey post-hoc multiple comparisons revealed 37 differentially expressed proteins among 6 different time-points. These altered proteins were successfully identified by MALDI-TOF MS and classified into 6 categories: (i) proteins with decreased urinary excretion during PHN; (ii) proteins with increased urinary excretion during PHN; (iii) proteins with increased urinary excretion during PHN, but which finally returned to basal levels; (iv) proteins with increased urinary excretion during PHN, but which finally declined below basal levels; (v) proteins with undetectable levels in the urine during PHN; and (vi) proteins that were detectable in the urine only during PHN. Most of these altered proteins have functional significance in signaling pathways, glomerular trafficking, and controlling the glomerular permeability. The ones in categories (v) and (vi) may serve as biomarkers for detecting or monitoring membranous nephropathy. After normalization of the data with 24-h urine creatinine excretion, changes in 34 of initially 37 differentially expressed proteins remained statistically significant. These data underscore the significant impact of urinary proteomics in unraveling disease pathophysiology and biomarker discovery.

Blunted renal dopaminergic system activity in HgCl2-induced membranous nephropathy

The present study evaluated the possible role of the renal dopaminergic system in the sodium retention of HgCl2-induced nephrotic syndrome. The time courses of urinary excretion of sodium, protein, dopamine and the precursor l-3,4-dihydroxyphenylalanine (L-Dopa) were evaluated in HgCl2-treated and control rats up to day 21. The renal aromatic l-amino acid decarboxylase (AADC) activity, the enzyme responsible for the synthesis of renal dopamine, was evaluated during negligible proteinuria accompanied with enhanced sodium retention (day 7), increased proteinuria accompanied with greatest sodium retention (day 14) as well as during increased proteinuria accompanied with negative sodium balance (day 21). Also, the influence of volume expansion (VE, 5% bw) and the effects of the D1-like agonist fenoldopam (10 microg kg bw(-1) min(-1)) on natriuresis and on proximal tubular Na+,K+-ATPase activity were examined on day 14. The daily urinary dopamine output and urinary dopamine/L-Dopa ratios were reduced in HgCl2-treated rats from day 2 and beyond. This was accompanied by a marked decrease in renal AADC throughout the study. During VE, the fenoldopam-induced inhibition of proximal tubular Na+,K+-ATPase activity was similar between HgCl2-treated and control rats. However, the urinary sodium excretion during fenoldopam infusion was markedly increased by 60% to 120% in control rats but was not altered in HgCl2-treated rats. It is concluded that HgCl2 nephrosis is associated with a blunted renal dopaminergic system activity. However, the lack of renal dopamine in HgCl2 nephrosis does not appear to be related with the overall renal sodium retention in a state of proteinuria.

Idiopathic Membranous Nephropathy: Outline and Rationale of a Treatment Strategy

Idiopathic membranous nephropathy is a common cause of nephrotic syndrome. The treatment of patients with idiopathic membranous nephropathy is heavily debated. Based on literature data and our own experience, we propose a rational treatment strategy. Patients with renal insufficiency (serum creatinine level > 1.5 mg/dL [> 135 micromol/L]) are at greatest risk for the development of end-stage renal disease and should receive immunosuppressive therapy. In patients with normal renal function (serum creatinine level < 1.5 mg/dL [< 135 micromol/L]), risk for developing end-stage renal disease can be estimated by measuring urinary excretion of beta2-microglobulin or alpha1-microglobulin and immunoglobulin G. For low-risk patients, a wait-and-see policy is advised. High-risk patients likely benefit from immunosuppressive therapy. Currently, combinations of steroids with chlorambucil or cyclophosphamide are the best studied. We prefer cyclophosphamide in view of its fewer side effects. Cyclosporine may be an alternative option in patients with well-preserved renal function, although long-term data are lacking. Other immunosuppressive agents, such as mycophenolate mofetil or rituximab, currently are under study; however, data are insufficient to support their routine use.

Urinary sediment features in proliferative and non-proliferative glomerular diseases

BACKGROUND

The studies on urine sediment particles in patients with glomerular diseases (GD) are few and have focused only on single urine particles. In this study, we investigated the prevalence and number of 12 urine sediment particles in two groups of patients, one with proliferative GD, and the other with non-proliferative GD.

METHODS

The urine sediment of 100 consecutive patients, with a renal biopsy-proven proliferative or non-proliferative GD and marked cylindruria, were examined a few hours before renal biopsy according to a standardized method. The urine particles investigated were erythrocytes, leukocytes, renal tubular cells, lipids and hyaline, hyaline-granular, granular, waxy, erythrocytic, leukocytic, epithelial and fatty casts.

RESULTS

Patients with proliferative GD (n=52) had both a significantly higher prevalence of microscopic hematuria, leukocyturia, tubular epithelial cells, erythrocytic casts, epithelial casts, and significantly higher amounts of erythrocytes,leukocytes, tubular epithelial cells/20 high power field (HPF), erythrocytic and epithelial casts. On the other hand, patients with non-proliferative GD (n=48) had significantly higher numbers of fatty casts. In proliferative GD, leukocyturia was associated with intracapillary and extracapillary proliferation, crescents and fibrinoid necrosis at renal biopsy. At discriminant analysis, the two types of GD could be identified with 80.8% sensitivity and 79.2% specificity. By multiple logistic regression analysis, patients with erythrocytes, leukocytes and erythrocytic casts in the urine had an odds ratio (OR) of 9.91 (95% confidence interval (95% CI): 1.01-97.51), 7.85 (95% CI: 2.77-22.20), and 4.33 (95% CI: 1.41-13.31), respectively, of having proliferative GD.

CONCLUSIONS

Our examination of the urine sediment shows that proliferative GD and non-proliferative GD differ in many respects.

Treatment-related changes in urinary excretion of high and low molecular weight proteins in patients with idiopathic membranous nephropathy and renal insufficiency

BACKGROUND

In patients with idiopathic membranous nephropathy, an increased urinary excretion of high (IgG) and low [beta(2)-microglobulin (beta(2)M), alpha(1)-microglobulin (alpha(1)M)] molecular weight proteins predicts prognosis and precedes renal insufficiency. We have studied the changes in the urinary excretion of these proteins in patients with idiopathic membranous nephropathy and renal insufficiency during and after treatment with cyclophosphamide and steroids, and investigated their value in predicting long-term outcome.

METHODS

Standardized measurements of urinary IgG, albumin, beta(2)M and alpha(1)M were performed at 0, 2, 6 and 12 months in 11 patients, at 12 months in 25 patients and in 17 of these last patients after 2-5 years.

RESULTS

We observed a rapid improvement of glomerular permselectivity and tubular protein reabsorption within 2 months after the start of therapy. Despite a partial remission of proteinuria within 12 months in most patients, evidence of tubulo-interstitial injury remained apparent. Neither absolute levels of urinary IgG, beta(2)M or alpha(1)M at baseline or at 12 months nor the percentage reduction between baseline and 12 months clearly predicted the occurrence of a remission or a relapse to nephrotic range proteinuria. In the case of a persistent stable remission, we observed a gradual decrease of urinary beta(2)M towards normal values.

CONCLUSIONS

In patients with idiopathic membranous nephropathy and renal insufficiency, treatment with cyclophosphamide and steroids resulted in an improvement of glomerular permeability and tubular proteinuria. Tubular proteinuria remained present for many years, even in patients with stable remission of proteinuria. Measurements of urinary proteins at 12 months after treatment start lacked predictive accuracy.

Urinary liver-type fatty acid-binding protein: discrimination between IgA nephropathy and thin basement membrane nephropathy

BACKGROUND

Microscopic hematuria without proteinuria is a common clinical finding in cases of immunoglobulin A (IgA) nephropathy and of thin basement membrane nephropathy. Liver-type fatty acid-binding protein (L-FABP) is expressed in renal proximal tubules and is reported to be a useful marker of the progression of chronic glomerulonephritis.

AIM

To assess urinary L-FABP levels for differential diagnosis in patients with microscopic hematuria but without proteinuria.

METHODS

This was a multi-center retrospective study. Thirty adult patients who underwent renal biopsy for microscopic hematuria and 20 healthy adult volunteers were included in this study. Urinary L-FABP levels were measured by enzyme-linked immunosorbent assay and compared, particularly between those diagnosed with IgA nephropathy and those diagnosed with thin basement membrane nephropathy.

RESULTS

Twelve (40%) patients had IgA nephropathy, 6 (20%) had thin basement membrane nephropathy and 12 (40%) had normal biopsy findings. The urinary L-FABP level was significantly higher in patients with IgA nephropathy (38.4 +/- 26.8 microg/g Cr) than in healthy subjects (5.8 +/- 4.0 microg/g Cr) (p < 0.01); however, the level in patients with thin basement membrane nephropathy or normal biopsy results was comparable to that in healthy subjects. Follow-up data were available for 11 of the 12 patients with IgA nephropathy who initially had no proteinuria. After 24 months, 4 of the 11 were found to have proteinuria, and the urinary L-FABP level had increased from 40.6 +/- 30.5 microg/g Cr to 58.8 +/- 40.5 microg/g Cr (p < 0.01).

CONCLUSIONS

Our data suggest that the urinary L-FABP level can be used to discriminate between IgA nephropathy and thin basement membrane nephropathy in patients with microscopic hematuria.

Urine protein patterns can serve as diagnostic tools in patients with IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is the most common chronic glomerular disease in adults. End-stage renal disease (ESRD) develops in about 30% of the patients. Early intervention and consequent therapy may prevent or at least delay the development of ESRD in these patients. Up to now, the diagnosis could only be achieved with a renal biopsy.

METHODS

The urine of 45 patients with IgAN was collected and screened for protein/polypeptide patterns with a novel high throughput method, capillary electrophoreses on-line coupled to a mass spectrometer (CE-MS). CE-MS allows the fast and accurate evaluation of up to 2000 polypeptides in one urine sample. The results in IgAN were compared to findings in 13 patients with membranous nephropathy (MN) and 57 healthy individuals.

RESULTS

In the patients with IgAN, even when urinary protein excretion was within the normal range of regular tests, the polypeptide pattern in urine differed significantly from that of healthy controls and patients with MN, indicating a specific "IgAN" pattern of polypeptide excretion. Classification regarding discrimination of IgAN from healthy controls and from MN had a sensitivity of 100% and 77%, respectively. Specificity was 90% and 100%, respectively. Compared to patterns established earlier in patients with minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), or diabetic nephropathy (DN), sensitivity and specificity were 100%. Treatment of the patients was associated with changes of the pattern, possibly indicating a therapeutic effect.

CONCLUSION

Proteomic analysis with CE-MS coupling permits fast and accurate identification and differentiation of polypeptide patterns in the urine of patients with IgAN, allowing differentiation from healthy controls and, probably, other renal diseases.

Glomerular deposition and urinary excretion of complement factor H in idiopathic membranous nephropathy

BACKGROUND/AIMS

The complement system plays an important role in the pathogenesis of membranous nephropathy (MN). In order to elucidate the regulatory mechanism of complement activation, we demonstrated glomerular deposition and urinary excretion of complement factor H, which controls the alternative pathway and the amplification loop at the C3 step, in patients with idiopathic MN.

METHODS

Renal biopsy specimens from 20 patients with idiopathic MN were studied immunohistochemically using monoclonal antibodies against complement components including factor H. SDS-PAGE and Western blotting analysis of urine samples were performed, and the urinary excretion of factor H and C5b-9 were measured by quantitative sandwich ELISA.

RESULTS

Intense glomerular deposition of factor H was observed with C3b.C3c and C5b-9 at an early stage of the disease. Factor H was detected in Western blots of urine samples, but factor H-like protein 1 (FHL-1) was not. The mean level of urinary factor H was elevated (86.30 +/- 21.93 U/mg urinary creatinine) in comparison to that of normal controls (4.76 +/- 1.03 U/mg urinary creatinine). Urinary factor H level exhibited no correlation with clinical parameters; however, a negative correlation was found between urinary C5b-9/factor H and creatinine clearance (r = 0.662, p < 0.01).

CONCLUSION

The source of glomerular and urinary factor H is supposedly a 150-kD protein. There was no evidence to suggest that FHL-1 is synthesized at the site of inflammation. The urinary C5b-9 to urinary factor H ratio is indicative of the degree of ongoing complement activation in the glomeruli and complement-mediated renal injury. These findings suggest that factor H contributes to the control mechanism of in situ complement activation and prevents renal damage in idiopathic MN.

Hematuria in Thin Basement Membrane Nephropathy

Thin basement membrane nephropathy (TBMN) often is diagnosed clinically when there is persistent dysmorphic or glomerular hematuria, but minimal proteinuria, normal kidney function, and no other obvious cause. This study investigated hematuria in patients with TBMN. A total of 112 patients with biopsy examination-proven TBMN were studied. All had hematuria at the time of presentation, with a mean urinary red blood cell (RBC) count of 256 +/- 250 x 10 3 /mL. Seventy-five (67%) patients attended for review over a median of 48 months (range, 3-120 mo) and provided a total of 485 urine specimens. Twenty-one patients (28%) had no hematuria by phase-contrast microscopy on at least 1 occasion. These corresponded to 32 urine specimens (7% of total). Of the 21 patients, the most recent urinary RBC counts were within the normal range in 11 (52%), but hematuria had recurred in the other 10 (48%). Hematuria is persistent in most patients with TBMN, but occasionally it resolves or is intermittent.

Thin Basement Membrane Nephropathy in Pregnancy

There are several published series of pregnancy in patients with nonimmunoglobulin A mesangial proliferative glomerulonephritis (most of whom have thin basement membrane nephropathy [TBMN]). The aim of the present study was to review the maternal and fetal outcomes of pregnancy in women with TBMN. The medical and obstetric histories of 86 women with TBMN and their 182 pregnancies (one twin) were reviewed. Data were collected retrospectively in 164 pregnancies (90%) and prospectively in 18 pregnancies (10%). Hypertension (alone or with proteinuria) developed in 15 unmonitored pregnancies (9%), and proteinuria alone developed in the third trimester in 2 pregnancies (1%). Hypertension was more common in the prospectively monitored pregnancies (6 pregnancies, 33%). In all, there were 174 live births (95%), and all fetal deaths occurred in the first and second trimesters in the absence of maternal complications. However, all the mothers of the 4 small for gestational age babies had been hypertensive. In TBMN, maternal hypertension, prematurity, and small for gestational age rates did not exceed those in the normal population. Overall, pregnancy in women with TBMN does not appear to be attended by a significantly increased maternal or fetal risk.

Urinary glycosaminoglycan composition in chronic glomerulonephritis

BACKGROUND

Glycosaminoglycans (GAG) play an important role in regulating glomerular permeability, and a reduction in their plasmatic concentration or urinary loss has been implicated in the pathogenesis of diseases associated with increased albumin permeability. The purpose of this study was to evaluate GAG excretion in renal pathology by analyzing the composition of urinary GAG in antibody mediated glomerular injury, such as mesangial glomerulonephritis (IgAGN) and primitive membranous glomerulonephritis (MGN), to verify the effects of glomerular capillary wall lesion with and without mesangial cell injury.

METHODS

Urinary GAG excretion was analyzed in 20 patients with IgAGN, 18 patients with MGN, and in 18 healthy subjects (controls). GAG were isolated from 24-hr urine using ion-exchange chromatography on DEAE-Sephacel, and the results are expressed as mg hexuronate/g creatinine (Cr). GAG composition was determined by cellulose acetate electrophoresis and expressed as relative percentages by densitometric scanning of Alcian Blue stained strips.

RESULTS

We found total GAG levels significantly higher in the urine of patients with MGN in comparison with controls and patients with IgAGN. The electrophoretic pattern analysis demonstrated low sulfated chondroitin sulfate proteoglycan (LSC-PG) in all patients compared to 44% in controls (8/18), but also low sulfated chondroitin sulfate (LSC) in 18.4% of patients (7/38) and slow migrating LSC (SM-LSC) in 8% of patients (3/38), only in the MGN group. Moreover, in patients with MGN, the LSC-PG relative content was significantly higher when compared to that observed in controls. Finally, in IgAGN and MGN patients, a significant reduction in chondroitin sulfate (CS) relative content was observed.

CONCLUSIONS

It seems likely that an increase in total GAG levels takes place when a reduction in renal function occurs, but the alteration of CS and herapan sulfate (HS) relative contents, and the presence of LSC-PG and free LSC also in the urine of IgAGN patients, allows us to suggest that the GAG distribution pattern becomes abnormal before an increase in total urine GAG excretion. In addition, the quali-quantitative determination of urinary GAG and GAGprotein complex could constitute an additional non-invasive marker to appraise the metabolism of renal connective tissue in some renal diseases.

Urinary Excretion of β2-Microglobulin and IgG Predict Prognosis in Idiopathic Membranous Nephropathy: A Validation Study

An accurate prediction of the prognosis of patients with idiopathic membranous nephropathy (iMN) should allow restriction of immunosuppressive treatment to patients who are at highest risk for ESRD. On the basis of retrospective studies, it has previously been suggested that the urinary excretions of beta2-microglobulin (Ubeta2m) and IgG (UIgG) are useful predictors of renal insufficiency in patients with iMN. The threshold values of 0.5 micro/min (Ubeta2m) and 250 mg/24 h (UIgG) have been validated in a new and larger patient cohort. From 1995 onward, 57 patients with iMN (38 men, 19 women; age 48 +/- 16 yr), a nephrotic syndrome, and a serum creatinine level </=1.5 mg/dl were studied prospectively. At baseline, a standardized measurement was carried out to determine renal function and protein excretion. The end point renal death was defined as a serum creatinine exceeding 1.5 mg/dl or a rise of serum creatinine of >50%. Mean (+/-SD) follow-up was 53 +/- 23 mo. Thus far, 25 (44%) of the patients have reached the end point renal death. Multivariate analysis confirmed Ubeta2m as the strongest independent predictor for the development of renal insufficiency. Sensitivity and specificity were 88 and 91%, respectively, for Ubeta2m, and both were 88% for UIgG. When the excretions of both proteins were combined, specificity improved to 97%. It is concluded that the present data validate the accuracy of Ubeta2m and of UIgG in predicting renal outcome in patients with iMN. These markers can be used to guide decisions on the start of immunosuppressive treatment.

Proteomic patterns established with capillary electrophoresis and mass spectrometry for diagnostic purposes

BACKGROUND

Proteomics applied in large scale may provide a useful diagnostic tool.

METHODS

We developed an online combination of capillary electrophoresis with mass spectrometry, allowing fast and sensitive evaluation of polypeptides found in body fluids. Utilizing this technology, polypeptide patterns from urine are established within 45 minutes. About 900 to 2500 polypeptides as well as their concentrations are detected in individual urine samples without the need for specific reagents such as antibodies. To test this method for clinical application, we examined spot urine samples from 57 healthy individuals, 16 patients with minimal change disease (MCD), 18 patients with membranous glomerulonephritis (MGN), and 10 patients with focal segmental glomerulosclerosis (FSGS).

RESULTS

One-hundred seventy-three polypeptides were present in more than 90% of the urine samples obtained from healthy individuals, while 690 polypeptides were present with more than 50% probability. These data permitted the establishment of a "normal" polypeptide pattern in healthy individuals. Polypeptides found in the urine of patients differed significantly from the normal controls. These differences allowed the distinction of specific protein spectra in patients with different primary renal diseases. Abnormal pattern of proteins were found even in urine from patients in clinical remission.

CONCLUSION

The data indicate that capillary electrophoresis with mass spectrometry coupling provides a promising tool that permits fast and accurate identification and differentiation of protein patterns in body fluids of healthy and diseased individuals, thus enabling diagnosis based on these patterns.

Mass spectrometry for the detection of differentially expressed proteins: a comparison of surface-enhanced laser desorption/ionization and capillary electrophoresis/mass spectrometry

The discovery of biomarkers is currently attracting much interest as it harbors great potential for the diagnosis and monitoring of human diseases. Here we have used two advanced mass spectroscopy based technologies, surface enhanced laser desorption ionization (SELDI-MS) and capillary electrophoresis/mass spectrometry (CE/MS), to obtain proteomic patterns of urine samples from patients suffering from membranous glomerulonephritis (MGN) and healthy volunteers. The results indicate that CE/MS analysis is able to display a rich and complex pattern of polypeptides with high resolution and high mass accuracy. In order to analyze these patterns, the MosaiqueVisu software was developed for peak identification, deconvolution and the display of refined maps in a three-dimensional format. The polypeptide profiles obtained with SELDI-MS from the same samples are much sparser and show lower resolution and mass accuracy. The SELDI-MS profiles are further heavily dependent on analyte concentration. SELDI-MS analysis identified three differentially expressed polypeptides, which are potential biomarkers that can distinguish healthy donors from patients with MGN. In contrast, approximately 200 potential biomarkers could be identified by CE/MS. Thus, while SELDI-MS is easy to use and requires very little sample, CE/MS generates much richer data sets that enable an in-depth analysis.

Demonstration of apoptosis-associated cleavage products of DNA, complement activation products SC5b-9 and C3d/dg, and immune complexes CIC-C3d, CIC-IgA, and CIC-IgG in the urine of patients with membranous glomerulonephritis

AIM

To investigate the involvement of complement activation and apoptosis in the pathogenesis of membranous glomerulonephritis by determining the concentrations of apoptosis-associated 180 bp nucleosomes and complement activation products SC5b-9 and C3d/dg in the urine of patients with membranous glomerulonephritis.

METHODS

Morning urine was taken from 15 patients with immunohistologically established membranous glomerulonephritis. Apoptosis-associated 180 bp nucleosomes, complement activation products SC5b-9, C3d/dg, and immune complexes CIC-C3d, CIC-IgA, and CIC-IgG were detected in the urine samples by using antigen-specific enzyme-linked immunosorbent assay.

RESULTS

Concentrations of measured parameters were expressed in units of standard deviation, ie, relatively to the average concentrations measured in healthy subjects. We found drastically increased concentrations of apoptosis-associated 180 bp nucleosomes (13.71+/-14.97; p=0.047), complement activation products SC5b-9 (197.07+/-134.88; p=0.003) and C3d/dg (38.70+/-43.35; p=0.048), and immune complexes CIC-C3d (11.01+/-13.39; p=0.74), CIC-IgA (7.93+/-4.38; p=0.001), and CIC-IgG (20.56+/-10.87; p=0.001) in the urine of patients with an active form of membranous glomerulonephritis. All studied molecules were absent, or present in very low concentrations, in healthy subjects and patients with membranous glomerulonephritis in remission. The mean differences between healthy controls and patients with the active disease were statistically significant in all parameters, except CIC-C3d.

CONCLUSIONS

There is an association of complement activation and apoptosis with membranous glomerulonephritis. Correlation analysis suggests that the excretion of apoptosis-associated 180 bp nucleosomes, SC5b-9, C3d/dg, and immune complexes containing IgA and IgG in the urine of patients with active membranous glomerulonephritis does not depend solely on the passive transport together with other proteins, but is probably an independent active process.

Podocytes that detach in experimental membranous nephropathy are viable

BACKGROUND

Podocyte loss contributes to the development of glomerulosclerosis. Although podocytes have been detected in the urine in certain glomerular diseases, the viability of detached cells is not known.

METHODS

Urine was collected from rats with experimental membranous nephropathy [passive Heymann nephritis (PHN) model], centrifuged, and following resuspension in tissue culture media, cells were seeded onto collagen-coated tissue culture plates. Cells were grown under typical cell culture conditions. Cell number was measured, the cell type was identified by immunostaining with specific antibodies, and cell morphology was assessed by light and electron microscopy.

RESULTS

Cells obtained in the urine from PHN rats were positive for synaptopodin, nephrin, podocin, WT-1, and GLEPP1 (podocyte-specific antigens). When grown ex vivo under cell culture conditions, cells obtained in the urine from PHN rats adhered to tissue culture plates, and expressed podocyte-specific proteins at the mRNA [reverse transcription-polymerase chain reaction (RT-PCR)] and protein (immunostaining) level. Cells did not stain with antibodies to mesangial (OX-7), tubular (Tamm-Horsfall protein) and endothelial (RECA) cells. Electron microscopy showed the presence of foot processes, and podocytes from PHN rats stained positive for C5b-9. Although podocyte number increased transiently during the first 5 days ex vivo, apoptosis increased significantly thereafter, reducing overall cell number.

CONCLUSION

Rats with experimental membranous nephropathy shed podocytes into the urine that attach to tissue culture plates ex-vivo, and proliferate. These results suggest that detached podocytes are viable. These results add new perspectives into our understanding of podocyte loss in the development of glomerulosclerosis.

A whitened face woman with nephrotic syndrome

Skin whitening cream from developing countries is a recognized source of chronic mercury poisoning. The authors report on a 34-year-old Indonesian domestic helper who presented with nephrotic syndrome secondary to membranous nephropathy. It was subsequently found that she used a skin whitening cream regularly that was found to contain a mercury level of almost 2,000 times above the allowable limit. Her blood and urinary mercury levels were both grossly elevated. Her symptoms improved after she stopped using the cream. However, she returned to her home country before chelating therapy could be arranged. Because mercury-containing skin products are still widely available in developing countries, the use of these products should be considered a possible cause of membranous nephropathy in immigrants from those countries.

Depletion of clusterin in renal diseases causing nephrotic syndrome

BACKGROUND

Clusterin is a lipoprotein that has anti-complement effects in membranous nephropathy (MN). In focal segmental glomerulosclerosis (FSGS), it inhibits permeability plasma factor activity and could influence proteinuria. Moreover, with aging, knockout mice for clusterin develop a progressive glomerulopathy with sclerosis.

METHODS

Since little is known about clusterin metabolism in humans, we determined clusterin levels and composition in the sera and urine of 23 patients with MN, 25 with FSGS and 23 with steroid-responsive nephrotic syndrome (NS). Renal localization was evaluated by immunofluorescence and morphometry.

RESULTS

Serum clusterin was markedly reduced in active MN, in FSGS and in children with NS compared to controls; after stable remission of proteinuria, nearly normal levels were restored. Among various biochemical variables, serum clusterin was inversely correlated with hypercholesterolemia. Urinary clusterin, representing a 0.01 fraction of serum, was higher in the urine from normal subjects and FSGS patients in remission with proteinuric MN, FSGS and idiopathic NS; clusterin was inversely correlated with proteinuria. In all cases, urinary and serum clusterin was composed of the same 80 kD isoforms. Finally, a decrease in focal segmental or global clusterin staining was found in FSGS glomeruli, especially in areas of sclerosis. Instead, in MN an overall increment of staining was observed that ranged from mild/focal to very intense/diffuse.

CONCLUSIONS

The overall pool of clusterin is reduced in glomerular diseases causing nephrotic syndrome, with hypercholesterolemia appearing as the unifying feature. Depletion of clusterin should negatively affect the clinical outcome in nephrotic patients and efforts should be aimed at normalizing clusterin overall pool.

[Familial membranous nephropathy: an analysis of 3 kindreds and literature review]

OBJECTIVE

To report three kindreds of familial membranous nephropathy and describe its clinical and pathological characteristics.

METHODS

6 patients with renal biopsy proved familial membranous nephropathy from 3 kindreds were described. Their clinical and pathological data were compared with 33 patients who were also suffering from familial membranous nephropathy from 16 kindreds documented in PubMed and 30 sporadic patients who were collected in our hospital with membranous nephropathy.

RESULTS

Compared with the patients documented in the literatures, the patients were older and the ratios of male and female patients in this series were equal. In both series, the pathological lesions were severe. Compared with sporadic patients with membranous nephropathy, the patients in familial form had severer pathological lesions. There were no differences among all patients in clinical manifestations, such as proteinuria, hypertension and renal function. The major clinical symptom in familial membranous nephropathy patients was nephritic syndrome.

CONCLUSIONS

The present study first reported the kindreds of familial membranous nephropathy in China. The clinical manifestations of familial membranous nephropathy in our patients, as well as in other familial cases reported to date, are similar with those in the non-familial membranous nephropathy patients, but the pathological changes in the familial cases were severer than those in the non-familial. To distinguish the familial form from idiopathic membranous nephropathy, it is essential to understand the genetic factors underlying this disease.

Urinary podocytes in primary focal segmental glomerulosclerosis

BACKGROUND/AIM

Focal segmental glomerulosclerosis (FSGS) is a common cause of nephrotic syndrome. Although the pathogenesis is not known, recent studies suggest that FSGS may be a podocyte disease. The aim of this study was to look for podocyte injury in this disease, using measurements of urinary podocytes.

METHODS

We examined the first morning urine of the day collected from 71 patients (45 men and 26 women, median age and range 11.2 and 3-29 years) diagnosed as having nephrotic syndrome. Freshly voided urine samples were examined by immunofluorescence labeling using monoclonal antibodies against human podocalyxin. Renal histological examinations were performed in 58 of the 71 patients: 28 had minimal-change disease, 20 had FSGS, and 10 had membranous nephropathy.

RESULTS

Median and range of urinary podocytes measured were 0.2 and 0-40.8 cells/ml for 71 patients with nephrotic syndrome and 0 and 0-0.8 cells/ml for normal healthy control subjects (n = 200). Patients with FSGS had significantly higher levels of urinary podocytes (median and range 1.3 and 0-40.8 cells/ml) than those with minimal-change disease (median and range 0 and 0-6.9 cells/m; p = 0.003) or membranous nephropathy (median and range 0 and 0-1.4 cells/ml; p = 0.02).

CONCLUSIONS

The urinary excretion of podocytes is significantly higher in patients with FSGS as compared with those having membranous nephropathy or minimal-change disease. These findings suggest that podocyte injury and loss in the urine may have an important role in the pathogenesis of FSGS.

Tubular NF-kappaB and AP-1 activation in human proteinuric renal disease

BACKGROUND

Nuclear factor-kappaB (NF-kappaB) and activated protein-1 (AP-1) are transcription factors that regulate many genes involved in the progression of renal disease. Recent data have shown that NF-kappaB is activated in tubules and glomeruli in various experimental models of renal injury. In vitro studies also suggest that proteinuria could be an important NF-kappaB activator. We therefore approached the idea that NF-kappaB may be an indicator of renal damage progression.

METHODS

Paraffin-embedded renal biopsy specimens from 34 patients with intense proteinuria [14 with minimal change disease (MCD) and 20 with idiopathic membranous nephropathy (MN)] and from 7 patients with minimal or no proteinuria (IgA nephropathy) were studied by Southwestern histochemistry for the in situ detection of activated transcription factors NF-kappaB and AP-1. In addition, by immunohistochemistry, we performed staining for the NF-kappaB subunits (p50 and p65) and AP-1 subunits (c-fos, c-jun). By immunohistochemistry and/or in situ hybridization, the expression of some chemokines [monocyte chemoattractant protein-1 (MCP-1), RANTES, osteopontin (OPN)] and profibrogenic cytokines [transforming growth factor-beta (TGF-beta)], whose genes are regulated by NF-kappaB and/or AP-1, were studied further.

RESULTS

NF-kappaB was detected mainly in the tubules of proteinuric patients, but rarely in nonproteinuric IgA nephropathy (IgAN) patients. In addition, there was a significant relationship between the intensity of proteinuria and NF-kappaB activation in MCD (r = 0.64, P = 0.01) and MN patients (r = 0.64, P < 0.01). Unexpectedly, patients with MCD had a significantly higher NF-kappaB tubular activation than those with MN (P < 0.01). To assess whether there was a different composition of NF-kappaB protein components, immunostaining was performed for the NF-kappaB subunits p50 and p65. However, no differences were noted between MCD and MN patients. In those patients, there was a lower tubular activation of AP-1 compared with NF-kappaB. Moreover, a strong correlation in the expression of both transcription factors was observed only in MN (r = 0.7, P = 0.004). Patients with progressive MN had an overexpression of MCP-1, RANTES, OPN, and TGF-beta, mainly in the proximal tubules, while no significant expression was found in MCD patients.

CONCLUSIONS

On the whole, our results show that a tubular overactivation of NF-kappaB and AP-1 and a simultaneous up-regulation of certain proinflammatory and profibrogenic genes are markers of progressive renal disease in humans. Increased activation of solely NF-kappaB and/or AP-1 may merely indicate the response of tubular renal cells to injury.

Urinary excretion of IgG and alpha(1)-microglobulin predicts clinical course better than extent of proteinuria in membranous nephropathy

In idiopathic membranous nephropathy (MN), the main predictors for progression to chronic renal failure (CRF) are the amount of proteinuria and extent of tubulointerstitial damage. The aim of this study is to evaluate whether urinary excretion of proteins reflecting the alteration of permselectivity in the glomerular capillary wall, such as immunoglobulin G (IgG), and the reabsorption impairment of low-molecular-weight proteins, such as alpha(1)-microglobulin (alpha(1)m), correlates with the extent of tubulointerstitial damage and have a predictive value for functional outcome and response to therapy better than 24-hour proteinuria. In 78 patients with MN, urinary excretion of albumin, transferrin, IgG, and alpha(1)m was measured by immunonephelometry in second-morning urine samples and expressed in milligrams per gram of urinary creatinine (uCr). In 48 patients with characterization of proteinuria and renal biopsy performed at the same time, excretion of IgG (P = 0.0087) and alpha(1)m (P = 0.0024), but not albumin (P = 0.37), transferrin (P = 0.38), or 24-hour proteinuria (P = 0.32), was associated significantly with the extent of tubulointerstitial damage (score, 0 to 1 versus >/=2). Only alpha(1)m excretion was associated significantly with global glomerular sclerosis (P = 0.0032) and arteriolar hyalinosis (P = 0.0004). Moreover, urinary excretion of alpha(1)m was significantly dependent on IgG excretion (r = 0.67; P = 0.0001), but not on albumin (P = 0.66) or 24-hour proteinuria (P = 0.07). Functional outcome could be evaluated in 38 patients with nephrotic syndrome and baseline normal renal function (serum creatinine, 0.99 +/- 0.20 mg/dL; follow-up, 44 +/- 22 months). Remission was 100% versus 20% in patients with IgG excretion less than 110 mg/g uCr versus 110 mg/g uCr or greater (P = 0.0001) and 77% versus 17% in patients with alpha(1)m excretion less than 33.5 mg/g uCr versus 33.5 mg/g uCr or greater (P = 0.0009), respectively. In patients with IgG and alpha(1)m excretion less than or greater than the cutoff value, progression to CRF was 0% versus 35% (P = 0.0026) and 0% versus 58% (P = 0.0001), respectively. Nineteen patients treated with immunosuppressive therapy were compared with 19 untreated patients. There was no difference in remission or progression between treated and untreated patients when IgG and alpha(1)m excretion were less than the cutoff value. There was a significant difference for progression to CRF between treated and untreated patients when alpha(1)m excretion was greater than the cutoff value (17% versus 100%; P = 0.0076). In conclusion, IgG excretion is associated significantly with the extent of tubulointerstitial damage and alpha(1)m excretion. This observation supports the hypothesis that IgG may be the toxic moiety of proteinuria. Excretion of IgG and alpha(1)m has a significant predictive value for both remission and progression and is useful to identify patients who are at risk for progression and for whom treatment with immunosuppressive therapy is indicated soon after diagnosis.

Cyclosporine in patients with steroid-resistant membranous nephropathy: a randomized trial

BACKGROUND

A clinical trial of cyclosporine in patients with steroid-resistant membranous nephropathy (MGN) was conducted. Although MGN remains the most common cause of adult-onset nephrotic syndrome, its management is still controversial. Cyclosporine has been shown to be effective in cases of progressive MGN, but it has not been used in controlled studies at an early stage of the disease.

METHODS

We conducted a randomized trial in 51 biopsy-proven idiopathic MGN patients with nephrotic-range proteinuria comparing 26 weeks of cyclosporine treatment plus low-dose prednisone to placebo plus prednisone. All patients were followed for an average of 78 weeks, and the short- and long-term effects on renal function were assessed.

RESULTS

Seventy-five percent of the treatment group versus 22% of the control group (P < 0.001) had a partial or complete remission of their proteinuria by 26 weeks. Relapse occurred in 43% (N = 9) of the cyclosporine remission group and 40% (N = 2) of the placebo group by week 52. The fraction of the total population in remission then remained almost unchanged and significant different between the groups until the end of the study (cyclosporine 39%, placebo 13%, P = 0.007). Renal function was unchanged and equal in the two groups over the test medication period. In the subsequent follow-up, renal insufficiency, defined as doubling of baseline creatinine, was seen in two patients in each group, but remained equal and stable in all of the other patients.

CONCLUSION

This study suggests that cyclosporine is an effective therapeutic agent in the treatment of steroid-resistant cases of MGN. Although a high relapse does occur, 39% of the treated patients remained in remission and were subnephrotic for at least one-year post-treatment, with no adverse effect on filtration function.

Turnover of human tubular cells exposed to proteins in vivo and in vitro

BACKGROUND

The cause of tubulointerstitial pathology in glomerular disease is uncertain. Proteinuria may be a causative factor and has been shown to increase the turnover of tubular cells in a rat model of proteinuria. We investigated whether increased tubular cell proliferation occurs in human proteinuric renal disease. A human cell culture model was used to investigate the effects of proteins on tubular cell turnover further.

METHODS

Tubular proliferation in renal biopsies from patients with membranous nephropathy (MN) and minimal change nephropathy (MCN) was assessed by in situ hybridization for histone mRNA. Proliferation was measured in polarized human tubular cell cultures using tritiated thymidine, following addition of proteins to the apical medium. Toxicity was assessed by lactate dehydrogenase (LDH) release and monolayer permeability to inulin.

RESULTS

Increased tubular cell histone mRNA expression occurred in biopsies in MN (3.0-fold increase, P < 0.002) and MCN (3.6-fold increase, P < 0.02). Serum proteins added to the medium on human tubular cell cultures increased thymidine uptake (1.3-fold, P < 0.005), LDH release (1.5-fold, P < 0.001), and monolayer permeability (1.7-fold, P < 0.005). The effects were reproduced by a fraction of molecular weight 40 to 100 kD, but not by pure albumin or transferrin.

CONCLUSIONS

Proliferation of tubular cells is associated with proteinuria in vivo and is caused by proteins in cell culture. Toxicity of proteins to tubular cells and increased cell turnover may contribute to tubulointerstitial pathology in glomerular disease.

Reduced urinary excretion of intact osteopontin in patients with IgA nephropathy

Osteopontin (OPN) is a phosphoprotein secreted by many cells of epithelial, mesenchymal, and hematopoietic origin. In the kidney, OPN is expressed in the renal tubules and collecting ducts and is excreted into the urine. A pathophysiologic role for urinary OPN has not been established. In this study, urinary excretion of OPN was analyzed in patients with primary glomerular diseases, including immunoglobulin A nephropathy (IgAN; n = 32), minimal change nephrotic syndrome (MCNS; n = 16), and membranous nephropathy (MN; n = 18). Compared with normal controls (n = 20), mean +/- SD of urinary OPN in IgAN patients was decreased significantly (21.4 +/- 6.2 versus 11.6 +/- 9.6 mg/g creatinine, P: < 0.001). In contrast, the levels of urinary OPN in patients with MCNS or MN did not differ significantly from normal values. Immunoblot analysis showed that OPN is present as a 55- to 60-kd molecule in normal urine. A 34-kd fragment of OPN was the major immunoreactive band in samples from IgAN patients. This fragment also was detectable in the urine from some patients with MCNS or MN but was absent in normal subjects. OPN has a thrombin-cleavage site near its central portion. Thrombin treatment of the urine from normal controls could result in 34-kd OPN fragments. Although the underlying mechanisms remain to be determined, these data provide evidence that secretion or processing (or both) of urinary OPN is altered in patients with IgAN.