Distinguishing minimal-change disease from mesangial disorders

IgA nephropathy in a boy with frequently relapsing nephrotic syndrome

A Japanese boy developed nephrotic syndrome (NS) and had microscopic hematuria at 8 years old. Renal biopsy was performed. Light microscopy study revealed mesangial proliferation and all immunofluorescent stains (including IgA) were negative, so he was diagnosed with non-IgA diffuse mesangial proliferation (DMP). Complete remission was achieved at 13 days after the initiation of oral prednisolone, and hematuria also disappeared 3 days later, but the patient developed frequently relapsing nephrotic syndrome. Cyclosporine A (CyA) was introduced at 10 years old, and there were no relapses between then and when it was discontinued at 12 years old. A second renal biopsy revealed minimal change without CyA nephrotoxicity. However, there was repeated relapse of NS after discontinuation, so CyA was reintroduced 8 months later, and NS remained in remission thereafter. Microscopic hematuria appeared at 13 years old, however, with gross hematuria appearing at the time of infection. A third renal biopsy revealed mesangial proliferation with IgA-dominant deposition, so the patient was diagnosed with IgA nephropathy. Currently (14 years old), CyA treatment has been discontinued and the patient is undergoing lisinopril therapy for IgA nephropathy, but there are still relapses of NS. To the best of our knowledge, there have been no previous reports of a patient with non-IgA DMP at the onset of NS who had later development of IgA nephropathy. The patient showed non-IgA DMP at the onset, suggesting that NS with non-IgA DMP and IgA nephropathy has some common pathophysiology. Treatment for NS, such as PSL and/or CyA treatment, may suppress the clinical manifestation of late IgA nephropathy.

Development of Immunoglobulin M Nephropathy in a Pregnant Woman

Immunoglobulin M nephropathy (IgMN) is a glomerular disease that may be identified in all age groups, but children and young adults appear to have been affected more frequently in some series. The clinical picture could differ from hematuria to rapidly progressive glomerulonephritis. The main characteristics in pathologic examination are mesangial hypercellularity with a diffuse and granular immunoglobulin M deposition in the glomerular structure. To date, a standardized protocol has not been proposed for IgMN treatment. Systemic corticosteroids, calcineurin inhibitors, cyclophosphamide, and rituximab were agents reported in the literature. We present a 30-year-old woman admitted to the hospital for edema in the lower extremities at the 31st week of pregnancy. She had one abortus previously, and this was her second pregnancy. Renal biopsy performed after delivery was reported as IgMN with mesangial proliferation. She received 1 mg/kg/day prednisone therapy achieving complete remission. This report is the first case of IgMN developed in pregnancy.

Renal Outcome of IgM Nephropathy: A Comparative Prospective Cohort Study

Immunoglobulin M nephropathy (IgMN) is an idiopathic glomerulonephritis characterized by diffuse deposits of IgM in the glomerular mesangium. However, its renal prognosis remains unknown. We compared renal outcomes of IgMN patients with those of patients with minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), or mesangial proliferative glomerulonephritis (MsPGN) from a prospective observational cohort, with 1791 patients undergoing native kidney biopsy in eight hospitals affiliated with The Catholic University of Korea between December 2014 and October 2020. IgMN had more mesangial proliferation and matrix expansion than MsPGN and more tubular atrophy and interstitial fibrosis than MCD. IgMN patients had decreased eGFR than MCD patients in the earlier follow-up. However, there was no significant difference in urine protein or eGFR among all patients at the last follow-up. When IgMN was divided into three subtypes, patients with FSGS-like IgMN tended to have lower eGFR than those with MCD-like or MsPGN-like IgMN but higher proteinuria than MsPGN-like IgMN without showing a significant difference. The presence of hypertension at the time of kidney biopsy predicted ≥20% decline of eGFR over two years in IgMN patients. Our data indicate that IgMN would have a clinical course and renal prognosis similar to MCD, FSGS, and MsPGN.

IgM mesangial deposition as a risk factor for relapses of adult-onset minimal change disease

BACKGROUND

Immunoglobulin M (IgM) mesangial deposition in pediatric minimal change disease (MCD) has been reported to be associated with steroid dependence and poor renal outcomes. However, the evidence linking the impacts of IgM mesangial deposition to the treatment prognosis in adult-onset MCD is still elusive.

METHODS

In this retrospective cohort study, 37 adult patients with MCD received kidney biopsies from January 2010 to May 2020. Immunofluorescence microscopy was performed and the patients dichotomized according to IgM mesangial deposition (12 patients with positive IgM deposition; 25 patients with negative IgM deposition). We analyzed the clinical features, the dosage of immunosuppressive agents, and the response to treatment for 2 years between the two groups.

RESULTS

Analysis of the clinical symptoms, the dosage of immunosuppressive treatment, and the time to remission revealed no statistical difference between the groups. However, compared to the negative IgM group, the frequency of relapses was significantly higher in the positive IgM group during the two-year follow-up period (the negative IgM group 0.25 episodes/year; the positive IgM group 0.75 episodes/year, p = 0.029). Furthermore, multivariate linear regression revealed that the positivity of IgM mesangial deposition is independently associated with the frequency of relapses (regression coefficient B 0.450, 95% CI 0.116-0.784, p = 0.010).

CONCLUSIONS

Our findings indicated that adult-onset MCD patients with IgM mesangial deposition have a high risk of relapses. Therefore, intensive monitoring of disease activity should be considered in MCD adults with IgM mesangial deposition.

Successful treatment of a rare variant of mesangioproliferative glomerulonephritis with IgM deposits with Cyclosporin A

We present a case with a rare variant of glomerulonephritis, IgM nephropathy, which occurs mainly with nephrotic syndrome. The clinical features of this variant of kidney damage are characterized; the pathogenetic and the transformation of this form of nephritis into focal segmental glomerulosclerosis are discussed. The development of severe nephrotic syndrome at the beginning of the disease, the formation of secondary steroid resistance have confirmed this hypothesis and have justified the treatment with cyclosporin A aimed at the recovery of the function of the podocyte with remission of nephritis.

A case report of immunoglobulin M nephropathy manifesting as crescentic glomerulonephritis and nephrotic syndrome in an adult

Background

The nature of immunoglobulin M (IgM) nephropathy has been controversial for a long time, but it is now considered an independent disease like immunoglobulin A nephropathy. IgM nephropathy has been known to have various clinical manifestations ranging from asymptomatic hematuria and/or proteinuria to nephrotic syndrome. Recently, one case of IgM nephropathy manifesting as crescentic glomerulonephritis (GN) was reported in a child.

Case presentation

We experienced a case of IgM nephropathy that manifested clinically as nephritic and nephrotic syndrome with pathologically confirmed crescentic GN in a 30-year-old woman. We administered a calcineurin inhibitor and corticosteroids to treat the ongoing nephrotic syndrome after remission of crescentic GN. As a result, her proteinuria was significantly reduced and edema improved.

Conclusions

We described a case of IgM nephropathy in an adult patient who initially developed crescentic GN with nephritic and nephrotic syndrome. This case report could contribute to a deeper understanding of IgM nephropathy.

The natural history of immunoglobulin M nephropathy in adults

Background

Immunoglobulin M (IgM) nephropathy is an idiopathic glomerulonephritis characterized by diffuse mesangial deposition of IgM. IgM nephropathy has been a controversial diagnosis since it was first reported, and there are few data identifying specific pathological features that predict the risk of progression of renal disease.

Methods

We identified 57 cases of IgM nephropathy among 3220 adults undergoing renal biopsy at our institution. Biopsies had to satisfy the following three criteria to meet the definition of IgM nephropathy in this study: (i) dominant mesangial staining for IgM, (ii) mesangial deposits on electron microscopy (EM) and (iii) exclusion of systemic disease.

Results

The median age was 42 years and 24 patients were male. Thirty-nine per cent of patients presented with the nephrotic syndrome, 49% presented with non-nephrotic proteinuria and 39% had eGFR <60 mL/min. The median post-biopsy follow-up was 40 months and serum creatinine had doubled in 31% by 5 years. Of histological parameters, glomerular sclerosis and tubular atrophy, but not mesangial proliferation, were risk factors for renal insufficiency. Thirty-nine per cent of nephrotic patients achieved complete remission, and outcome was significantly worse in those who did not respond to treatment. Focal segmental glomerulosclerosis was diagnosed in 80% of those undergoing repeat renal biopsy, despite ongoing mesangial IgM deposition.

Conclusions

We propose criteria for a consensus definition of IgM nephropathy.

Pregnancy in immunoglobulin M nephropathy

Immunoglobulin M nephropathy is an uncommon glomerular disease and a relatively less recognized clinico-immunopathological entity in the domain of glomerulonephritis, often thought to be a bridge between minimal change disease and focal segmental glomerulosclerosis. It is characterized by asymptomatic hematuria, episodes of macroscopic hematuria and proteinuria. Corticosteroids remain the mainstay of therapeutic strategies for such patients. We present what we believe to be the first known case of successful pregnancy in a 40-year-old woman with a 12-year history of underlying immunoglobulin M nephropathy. In view of the rarity of this disease we hope this report will assist professionals managing such cases.

IgM nephropathy: is it closer to minimal change disease or to focal segmental glomerulosclerosis?

Immunoglobulin (Ig)M nephropathy (IgMN), known since 1978, is a very controversial clinicopathological entity characterized by IgM diffuse deposits in the mesangium at immunofluorescence whereas light microscop identifies minimal glomerular lesion, hypercellularity and expansion of the mesangium or sclerotic focal, segmental lesion. Clinically, it is a nephrotic syndrome, especially in pediatric patients, or asymptomatic proteinuria and/or isolated hematuria. These characteristics narrowly define IgMN between minimal change disease and focal segmental glomerulosclerosis, so it is not often recognized as a separate pathology. Homogeneous epidemiologic, pathogenetic, clinical or histological data are not available. Recent research on the pathogenetic role of mesangial IgM has, however, renewed interest in IgMN and naturally the controversies.

Do C1q or IgM nephropathies predict disease severity in children with minimal change nephrotic syndrome?

BACKGROUND

It has been suggested that C1q and immunoglobulin M (IgM) nephropathy are variants of minimal change nephrotic syndrome (MCNS). Many researchers believe that these two conditions signify a worse prognosis for children with MCNS in comparison with immunofluorescence (IF)-negative MCNS. The aim of our study was to determine the prognostic significance of C1q nephropathy and IgM nephropathy in children with MCNS.

METHODS

Fifty-five children with MCNS who had been biopsied over the course of 24 years at our institution were retrospectively categorized into three groups on the basis of IF microscopy findings: IF-negative MCNS (29/55 patients), MCNS with IgM nephropathy (19/55 patients), and MCNS with C1q nephropathy (7/55 patients). Clinical characteristics at disease presentation, clinical course, and renal outcome were compared between groups during the median follow-up period of 16.9 years (minimum 1.0, maximum 31.1 years).

RESULTS

No statistically significant differences in clinical characteristics at disease presentation, clinical course, and renal outcome were found. Children with IgM nephropathy, C1q nephropathy, and IF-negative MCNS were clinically indistinguishable.

CONCLUSIONS

We concluded that C1q or IgM nephropathy variants do not seem to signify a worse prognosis in children with MCNS in comparison with IF-negative MCNS.

IgM nephropathy; time to act

Implication for health policy/practice/research/medical education: Much has been published on the epidemiology and clinicopathological characteristics of IgM nephropathy, but there is little information on the etiology,pathogenesis and specific therapy of the disease. Controversy still shrouds the definition and nosologic status of the disease. Well-coordinated and concerted international efforts and collaboration between researchers in the developing and developed countries are needed to make further progress on the above aspects of the disease.

A case of membranoproliferative glomerulonephritis developed over twenty years with three different findings of renal pathology

A 31-year-old woman with proteinuria, hypocomplementemia, rheumatoid factor, and high serum polyclonal IgM concentration was admitted to our hospital for renal biopsy. She had a past history of two renal biopsies. When she was 12 years old, she developed proteinuria, microscopic hematuria, and hypocomplementemia. She was diagnosed as having 'IgM nephropathy' based on minor glomerular abnormalities as determined by light microscopy and IgM and C3 deposition in the mesangial region by immunofluorescence microscopy at the first biopsy. Despite corticosteroid treatment, her proteinuria did not improve and she discontinued regular outpatient checkups. When she was 29 years old and pregnant, she developed preeclampsia and, after delivery, a second renal biopsy was implemented. She was diagnosed as having progressed 'IgM nephropathy' with endotheliosis induced by preeclampsia. She was treated with angiotensin II receptor blocker and her proteinuria diminished; however, 1 year after the delivery, she developed proteinuria again, along with microscopic hematuria and hypocomplementemia. A third renal biopsy was conducted at 31 years of age and she was diagnosed as having membranoproliferative glomerulonephritis (MPGN) type I on the basis of diffuse mesangial proliferation, endocapillary hypercellularity with double contour of the capillary wall, and lobular formation in glomeruli, as determined by light microscopy. Immunofluorescence staining demonstrated deposits of C3, C4, C1q, and IgM in the mesangial region and capillary wall. She underwent corticosteroid therapy followed by normalization of urinalysis and serum complement level. Although she had initially been diagnosed with 'IgM nephropathy', she was finally diagnosed with secondary MPGN and was successfully treated by corticosteroid therapy.

Is cyclophosphamide effective in patients with IgM-positive minimal change disease?

BACKGROUND

We analyzed the impact of immunoglobulin M (IgM) positivity on the relapse-free interval post completed course of cyclophosphamide (CYC) treatment in patients with steroid-dependent nephrotic syndrome (SDNS) and minimal change disease (MCD).

METHODS

This was a retrospective chart review of all children who received CYC for SDNS and MCD between 1988 and 2009. Patients were divided into three groups based on kidney biopsy: MCD without immunoglobulin M (IgM) positivity (IgM-), MCD with IgM-positive immunofluorescence (IF) only (IgM+), and MCD with IgM-positive IF and electron-dense deposits on electron microscopy (IgM++). The relapse-free time interval to the first relapse post-CYC therapy or up to 48 months of follow-up (if no relapse occurred) was used for survival analysis.

RESULTS

Forty children aged 1.5-12.3 years (15 were IgM-, 16 were IgM+, 9 were IgM++) received a cumulative CYC dose of 175 ± 30 mg/kg. The overall relapse-free survival time was 75 % at 12 months, 64 % at 24 months, 59 % at 36 months, and 56 % at 48 months, with no significant differences between the IgM groups (p = 0.80).

CONCLUSIONS

Based on our results, we conclude that more than 50% of our SDNS patients with MCD remained relapse-free 4 years post-CYC treatment. No significant difference in the response to CYC was observed between patients with or without IgM positivity.

IgM nephropathy revisited

IgM nephropathy (IgMN) is an idiopathic immune complex-mediated glomerulopathy that was first described as a distinct disease in a nephropathology literature in 1978. Here, a historical review and the current status of IgMN in the light of world literature and the current experience will be presented. The Pubmed (www.pubmed.gov) search was made for articles on IgMN as the sole subject of the study or where it constituted a significant number of cases in a biopsy series in the world literature written in English. A total of 41 articles were found. A critical review of the literature was made. Soon after 1978, a series of reports were published mostly from the western world, but the interest in the entity did not withstand the test of time. No substantial basic medical research was carried out and the disease was largely ignored by the western researchers. More recently, a flurry of articles have appeared in the literature on the topic, mostly from tropical countries, and have renewed the interest in the entity. However, most of the current literature on IgMN is based on clinical observations, and experimental models and mechanistic studies of IgMN are lacking. There is an urgent need to develop consensus based criteria for the diagnosis of the condition, as well as, to focus the research on mechanistic studies to understand the pathogenesis of the disease better.

Clinicopathologic characteristics and steroid response of IgM nephropathy in children presenting with idiopathic nephrotic syndrome

There is no detailed information on clinical and immunopathologic features of immunoglobulin M nephropathy (IgMN) in children with idiopathic nephrotic syndrome (INS) in Pakistan. We reviewed our native renal biopsies over 15 years (July 1995-July 2010) and identified 135 cases of IgMN in nephrotic children (≤17 years). Their demographic, clinical and immunopathologic data were retrieved from biopsy reports and case notes. Mean age of this cohort was 7.6 ± 4.2 years. Males were 92 (68.1%) and females were 43 (31.9%). Steroid-dependent NS was seen in 88 (65.2%) cases and steroid-resistant NS in 47 (34.2%). Hematuria was found in 42 cases (31.2%) and hypertension in 27 (19.5%). The most common morphologic change was glomerular mesangial proliferation, found in 89 (65.9%) biopsies. Minor changes were seen in 46 (34.1%) cases and focal segmental glomerulosclerosis (FSGS) in 37 (27.4%). Immunofluorescence microscopy showed diffuse mesangial positivity of IgM in all cases. C3 and C1q were found in 72 (53.3%) and 40 (29.7%) cases, respectively. Our results show that IgMN is a fairly common cause of INS in children in Pakistan. It shows a spectrum of morphologic changes ranging from minor changes to FSGS.

Familial forms of nephrotic syndrome

The recent discovery of genes involved in familial forms of nephrotic syndrome represents a break-through in nephrology. To date, 15 genes have been characterized and several new loci have been identified, with a potential for discovery of new genes. Overall, these genes account for a large fraction of familial forms of nephrotic syndrome, but they can also be recognized in 10-20% of sporadic cases. These advances increase diagnostic and therapeutic potentials, but also add higher complexity to the scenario, requiring clear definitions of clinical, histopathological and molecular signatures. In general, genetic forms of nephrotic syndrome are resistant to common therapeutic approaches (that include steroids and calcineurin inhibitors) but, in a few cases, drug response or spontaneous remission suggest a complex pathogenesis. Finally, syndromic variants can be recognized on the basis of the associated extra-renal manifestations. In this educational review, clinical, histological and molecular aspects of various forms of familial nephrotic syndrome have been reviewed in an attempt to define a rational diagnostic approach. The proposed model focuses on practical and economic issues, taking into consideration the impossibility of using genetic testing as starting diagnostic tool. The final objective of this review is to outline a diagnostic flow-chart for clinicians and geneticists and to generate a rational scheme for molecular testing.

Clinicopathological features and prognosis of Chinese children with idiopathic nephrotic syndrome between different age groups

Ethnicity and age play important roles in the epidemiology of idiopathic nephrotic syndrome (INS) in children. The purposes of this study were to compare the clinical features, renal histopathology, steroid response, and long-term prognosis in Chinese children between different age groups. This is a retrospective cohort study of children aged between 2 and 18 years old with INS. Patients were divided into two groups according to age. Group I consisted of children between 2 and 8 years old (n = 49). Group II consisted of the remaining patients (n = 50). The clinical biochemical parameters, response to steroid treatment, renal histology, and long-term outcomes were analyzed. The biochemical parameters at the onset were similar in the two groups. Group II had a significantly higher frequency of microscopic hematuria (P = 0.011). Of the 67 children biopsied, minimal change disease was the most common histopathology for both groups. There was a higher frequency with focal and segmental glomerulosclerosis in group II (24% vs. 6.1%), but the difference between the two groups was not significant. During follow-up, the frequency of hypertension was significantly higher in group II (P = 0.006). Two cases in group I developed chronic kidney disease (CKD) vs. eight cases in group II. The frequency of progression to CKD is significantly higher (P = 0.042) in Group II. In conclusion, children beyond 8 years of age with INS have a higher incidence of microscopic hematuria, higher risk of hypertension and progression to CKD in long-term follow-up.

Minimal change disease with IgM+ immunofluorescence: a subtype of nephrotic syndrome

Immunoglobulin (Ig) M nephropathy is defined by electron-dense mesangial deposits and mesangial IgM visible by immunofluorescence (IF) without other histopathologic and immunofluorescent microscopic abnormalities. Certain patients have only immuno-positive (IgM+) IF. Children presenting with steroid-dependent or steroid-resistant nephrotic syndrome have a high prevalence of IgM+ IF with or without electron-dense deposits. We reviewed the clinical course of children with steroid-dependent or steroid-resistant nephrotic syndrome who underwent renal biopsy at Texas Children's Hospital from 1989 to 2006 to further characterize IgM+ IF in children with nephrotic syndrome. Of the 55 children with steroid-resistant or -dependent minimal change disease (MCD), 23 had IgM+ IF. Of these 23 children, 61% had microscopic hematuria at presentation, 48% (11/23) were steroid-dependent, and 48% (11/23) steroid-resistant (one underwent biopsy prior to steroid therapy). We compared the efficacy of adjuvant treatment with cyclophosphamide and cyclosporine: 18% initially treated with cyclophosphamide obtained remission, while 55% had no response; 83% obtained subsequent remission with cyclosporine. Of those initially treated with cyclosporine, 88% obtained complete or partial remission. IgM+ IF may be surrogate marker for the severity of MCD. Based on our results, children with MCD and IgM+ IF have a better response to cyclosporine than cyclophosphamide.

C1q nephropathy and minimal change nephrotic syndrome

C1q nephropathy (C1qN) is an uncommon disorder seen in children and adults with nephrotic syndrome and non-specific urinary findings. It has been described with minimal change nephrotic syndrome (MCNS), focal segmental glomerulonephritis and isolated mesangial proliferative glomerulonephritis. We describe nine children with MCNS and mesangial C1q deposition. These children had a median age of 2.7 years at diagnosis (range 1.3-15 years), 56% were male and 78% were Hispanic. We compared these children to concurrent patients with nephrotic syndrome and biopsy-proven MCNS. We found that the C1qN patients were more likely than MCNS children to require chronic immunosuppression with calcineurin inhibitors or mycophenolate mofetil to maintain remission. However, all children were able to achieve and sustain clinical remission of nephrotic syndrome. Children with C1qN and minimal change histology have an increased frequency of frequently relapsing and steroid-unresponsive disease, but they can attain prolonged remission and stable renal function with calcineurin inhibitor or mycophenolate mofetil therapy.

Nicotine augments glomerular injury in a rat model of acute nephritis

BACKGROUND/AIMS

Epidemiologic studies suggest that cigarette smoke worsens the progression of renal injury in patients with glomerular diseases. The mechanisms involved have not been elucidated. These studies were designed to determine whether nicotine worsens markers of inflammation including glomerular cell proliferation and fibronectin deposition in an in vivo model of glomerular injury.

METHODS

Sprague-Dawley rats were injected with anti-Thy1 antibody and given either tap water or nicotine in the drinking water until sacrifice at day 14. Fibronectin expression was measured by Western blot and immunohistochemistry. COX-2 expression was also determined by Western blot in the kidney cortex of rats treated with nicotine and in cultured human mesangial cells treated with nicotine.

RESULTS

Anti-Thy1 antibody administration resulted in a significant increase in the number of cells per glomerulus that was further increased by the administration of nicotine. In nephritic rats, the administration of nicotine significantly increased fibronectin and COX-2 expression. In cultured human mesangial cells we also demonstrated that nicotine increases COX-2 expression and activity and that COX-2 mediates mesangial cell proliferation in response to nicotine.

CONCLUSION

Either in vivo or in vitro treatment with nicotine leads to activation of inflammatory mediators and hallmarks of glomerular injury, which may explain the mechanisms involved in the deleterious effects of cigarette smoking on renal disease.

Eye involvement in children with primary focal segmental glomerulosclerosis

Distinct eye abnormalities have been described in children with nephrotic syndrome, particularly in diffuse mesangial sclerosis (i.e. Pierson syndrome). The aim of the study was to investigate whether there were any associated ocular anomalies in children with steroid-resistant nephrotic syndrome (SRNS), all of whom had revealed primary focal segmental glomerulosclerosis in biopsy. Thirty-three SRNS patients (16 male, 17 female) with a median age of 10.5 years (range 3-25 years) were enrolled in the study. Twenty steroid-sensitive nephrotic syndrome (SSNS) patients (ten male, ten female) with a median age of 8 years (range 3-15 years) served as controls. All SRNS patients were examined by mutational analysis for mutations in the NPHS2, WT1, and LAMB2 genes. Nine out of 33 SRNS patients (27.2%) showed various eye abnormalities. However, no abnormal ocular findings were detected in any of the SSNS patients. Abnormal eye findings detected in SRNS patients were anisometropic amblyopia (n = 4), Mittendorf's dots (n = 4), myopic astigmatism (n = 3) and exotropia (n = 1). Macular pigment changes (n = 1), posterior subcapsular opacities (n = 1) and cataract (n = 1) were considered as steroid-induced side effects. In four patients, more than one eye abnormality was found. Mutational analysis for the NPHS2, WT1 and LAMB2 genes revealed disease-causing mutations in 24.2% of patients. Homozygous NPHS2 mutations were detected in five patients (15.1%), all of whom had parental consanguinity. In three patients (9%) from non-consanguineous parents, heterozygous de novo WT1 mutations were detected as disease-causing mutations. No LAMB2 mutation was detected in any patient. While four out of five (80%) patients with homozygous NPHS2 mutations showed at least one abnormal ocular finding (i.e. Mittendorf's dot or anisometric amblyopia), none of the patients with a WT1 mutation had ocular involvement. In conclusion, ocular involvement may accompany SRNS caused by primary focal segmental glomerulosclerosis (FSGS). Ophthalmologic evaluation at the time of diagnosis might be beneficial to characterize further the spectrum of this possible association.

Protracted remission of proteinuria after combined therapy with plasmapheresis and anti-CD20 antibodies/cyclophosphamide in a child with oligoclonal IgM and glomerulosclerosis

We describe a child presenting with oligoclonal plasma IgM (1.2 g%) and nephrotic syndrome with focal segmental glomerulosclerosis. Oligoclonality was demonstrated by the analysis of the complementary determining region 3 (CDR 3) on immunoglobulin heavy chains and by two dimensional electrophoresis and Western blot analysis that showed the bulk of isoforms having a cationic muU chain compared with the normal homologue (pI 7.5 vs 6.5). Urinary light chains were absent, and bone marrow aspirate was normal. Usual therapies for nephrotic syndrome with steroids and cyclosporin were useless. At the age of 9 years the patient was treated with plasmapheresis plus cyclophosphamide (2 mg/kg per day for 60 days), which temporarily reduced plasma IgM, and proteinuria was normal for 3 years. After this period, due to new recurrence of nephrotic syndrome, the patient received a cycle with anti-CD20 antibodies (500 mg/m(2) every week for a month) associated with a cycle of plasmapheresis that normalized proteinuria again, and, after 3 years, the proteinuria is still in remission. This is the first case of nephrotic syndrome associated with oligoclonal plasma IgM and mesangial IgM deposits. Both cyclophosphamide and anti-CD20 antibodies associated with plasmapheresis induced, at different stages, stable and protracted remission of proteinuria without evident side effects. Long term efficacy and safety of the association are still to be determined.

A proposed taxonomy for the podocytopathies: a reassessment of the primary nephrotic diseases

A spectrum of proteinuric glomerular diseases results from podocyte abnormalities. The understanding of these podocytopathies has greatly expanded in recent years, particularly with the discovery of more than a dozen genetic mutations that are associated with loss of podocyte functional integrity. It is apparent that classification of the podocytopathies on the basis of morphology alone is inadequate to capture fully the complexity of these disorders. Herein is proposed a taxonomy for the podocytopathies that classifies along two dimensions: Histopathology, including podocyte phenotype and glomerular morphology (minimal-change nephropathy, focal segmental glomerulosclerosis, diffuse mesangial sclerosis, and collapsing glomerulopathy), and etiology (idiopathic, genetic, and reactive forms). A more complete understanding of the similarities and differences among podocyte diseases will help the renal pathologist and the nephrologist communicate more effectively about the diagnosis; this in turn will help the nephrologist provide more accurate prognostic information and select the optimal therapy for these often problematic diseases. It is proposed that final diagnosis of the podocytopathies should result from close collaboration between renal pathologists and nephrologists and should whenever possible include three elements: Morphologic entity, etiologic form, and specific pathogenic mechanism or association.

Active focal segmental glomerulosclerosis is associated with massive oxidation of plasma albumin

The basic mechanism for idiopathic FSGS still is obscure. Indirect evidence in humans and generation of FSGS by oxidants in experimental models suggest a role of free radicals. In vitro studies demonstrate a main role of plasma albumin as antioxidant, its modification representing a chemical marker of oxidative stress. With the use of complementary liquid chromatography electron spray ionization tandem mass spectrometry (LC-ESI-MS/MS) and biochemical methods, plasma albumin was characterized in 34 patients with FSGS; 18 had received a renal transplant, and 17 had IgM mesangial deposition. Patients with FSGS that was in remission or without recurrence after transplantation had normal plasma albumin, and the same occurred in patients with primary and secondary nephrites and with chronic renal failure. In contrast, patients with active FSGS or with posttransplantation recurrence had oxidized plasma albumin. This finding was based on the characterization of albumin Cys 34 with an mass-to-charge ratio of 511.71 in triple charge that was consistent with the formation of a cysteic acid carrying a sulfonic group (alb-SO(3)(-)). The exact mass of albumin was increased accordingly (+48 Da) for incorporation of three oxygen radicals. Direct titration of the free sulfhydryl group 34 of plasma albumin and electrophoretic titration curves confirmed loss of free sulfhydryl group and formation of a fast-moving isoform in all cases with disease activity. This is the first demonstration of in vivo plasma albumin oxidation that was obtained with an adequate structural approach. Albumin oxidation seems to be specific for FSGS, suggesting some pathogenetic implications. Free radical involvement in FSGS may lead to specific therapeutic interventions.

NPHS2 (Podocin) mutations in nephrotic syndrome. Clinical spectrum and fine mechanisms

Nephrotic syndrome (NS) is the most frequent cause of proteinuria in children and is emerging as a leading cause of uremia. Molecular studies in families with recessive NS have led to the discovery of specialized molecules endowed in podocytes that play a role in proteinuria. This review focalizes the key position of podocin (NPHS2 gene) in this rapidly evolving field and furnishes a compendium to those involved in clinics and genetics of NS. Screening for NPHS2 mutations have been done in sporadic NS and familial cases with recessive inheritance, documenting a mutation detection rate of 45-55% in families and 8-20% in sporadic NS according to the different groups and considering all the clinical phenotypes. Almost 50 NPHS2 mutations have been reported and variants and/or non silent polymorphisms potentially involved in proteinuria were recognized. Personalized data on clinical aspects related to responsiveness to drugs, evolution to end stage renal failure and post-transplant outcome are reported. Functional studies and cell sorting experiments demonstrated retention in the endoplasmic reticulum of most mutants involving the stomatin domain. Pull-down experiments with the common R229Q polymorphism demonstrated an altered interaction with nephrin that affects the stability of the functional unit. Overall, data are here presented that underscore a major role of inherited defects of NPHS2 in NS in children (including a relevant impact in sporadic cases) and give the functional rationale for the association. A practical compendium is also given to clinicians involved in the management of NS that should modify the classic therapeutic approach.

Differential diagnosis in nephropathology: an immunofluorescence-driven approach

Evaluation of a renal biopsy can be intimidating, because observational data from histologic stains, direct immunofluorescence (IF), and electron microscopy must be integrated with clinical and laboratory data to arrive at the correct diagnosis. Numerous diagnostic categories usually merit consideration. The typical strategy to diagnose renal disease is heavily weighted toward analysis of the histologic pattern of glomerular injury. This focus on histology is understandable; histologic evaluation was the first analytic probe available and has driven the formulation of classification schemes. Evaluation of IF before review of the light microscopy facilitates diagnostic evaluation, because the possibilities are immediately reduced. This simplifies the crucial final step-clinical and histologic correlation. In this review, I discuss the information content of IF and provide an algorithmic approach to the major renal diseases based on an IF-driven dissection of the differential diagnosis.

Antiproliferative effect of nitric oxide on rat glomerular mesangial cells via inhibition of mitogen-activated protein kinase

The effect of nitric oxide (NO) donors and lipopolysaccharide (LPS) on the proliferation of rat glomerular mesangial cells was characterized. Exogenous application of a NO donor inhibited serum-induced proliferation in a time- and dose-dependent manner. S-Nitrosoglutathione (GSNO) also increased cGMP generation and arachidonic acid release, but it did not cause any measurable increase in the cytosolic Ca2+ concentration. Chelation of cytosolic Ca2+ or inhibition of mitogen-activated protein kinase (MAPK) kinase had an inhibitory effect on proliferation, but neither enhanced the antiproliferative effect of GSNO. In contrast, inhibition of guanylate cyclase or phospholipase A2 had no effect on proliferation, but partially reversed GSNO-induced antiproliferation by approximately 98 and 65%, respectively. GSNO did not cause cell death. Incubation of cells with LPS induced endogenous NO generation and had an antiproliferative effect. LPS-induced antiproliferation was reversed completely by inhibition of nitric oxide synthase and partially by inhibition of guanylate cyclase or phospholipase A2. GSNO or LPS inhibited serum-induced MAPK activation, and both effects were partially reversed by inhibition of guanylate cyclase or phospholipase A2. Inclusion of 8-bromo-cGMP or arachidonic acid in the growth medium resulted in a similar antiproliferative effect. In conclusion, in rat glomerular mesangial cells, MAPK inhibition and an antiproliferative effect could be induced by either an increase in the cellular concentration of NO or exposure of the cells to LPS. Part of the effect of NO was attributable to the increased cellular cGMP generation and arachidonic acid release.

Nonlupus nephritides in patients with systemic lupus erythematosus: a comprehensive clinicopathologic study and review of the literature

Renal biopsy specimens from patients with systemic lupus erythematosus (SLE) rarely show changes that are pathogenetically and morphologically unrelated to SLE. The morphology and behavior of these nonlupus nephritides are not well known. Two hundred fifty-two renal biopsies performed on 224 patients with SLE collected from 3,036 native kidney biopsies performed between 1975 and 1998 were reviewed, and those that showed nonlupus nephritides (index biopsies) were selected for studies. Thirteen biopsy specimens with nonlupus nephritides were identified in 13 patients, who belonged to 3 clinically distinct groups. Group I included 6 patients in whom SLE was diagnosed at the time of index biopsies. The index biopsies in these patients showed focal segmental glomerusclerosis (FSGS; 3 cases), Immunoglobulin (Ig) M nephropathy (1 case), and thin basement membrane disease (1 case). The diagnostic features for FSGS included segmental sclerosis involving at least 1 glomerulus, absence of lupus nephritis or other conditions that may cause nonspecific segmental sclerosis of glomeruli such as ischemia or nephrosclerosis, and nephrotic-range proteinuria. There was uniform, global, diffuse and marked thinning of the glomerular basement membrane in the case of thin basement membrane disease. Group II included 3 patients in whom SLE was diagnosed 2 to 9 years before the time of index biopsies and SLE was active at the time of biopsy. The index biopsies in these patients showed FSGS (2 cases) and hypertensive nephrosclerosis (1 case). Group III included 4 patients in whom SLE was diagnosed 5 to 36 years before the time of index biopsies and SLE was inactive at the time of biopsy. The index biopsies in these patients showed 1 case each of amyloidosis, FSGS, hypertensive nephrosclerosis, and allergic acute tubulointerstitial nephritis. Previous renal biopsies, performed in 5 patients, showed IgM nephropathy (1 case), diffuse proliferative lupus GN (1 case), focal proliferative lupus GN (1 case), and mesangial proliferative lupus GN (2 cases). Follow-up biopsies, performed in 3 patients, confirmed the diagnosis of FSGS (2 cases) and hypertensive nephrosclerosis (1 case) noted in the index biopsies. Nonlupus nephritides may occasionally be encountered in SLE patients, regardless of clinical or serologic disease activity. These renal lesions display a broad morphologic spectrum in which FSGS seems most frequent. Renal biopsy plays a crucial role in identifying these lesions, which may have prognostic and therapeutic implications distinct from those of lupus nephritis.

Glomerulopathy with mesangial IgM deposits: long-term follow up of 64 children

BACKGROUND

The aim of the present study was to investigate to what extent IgM nephropathy in children with minimal change nephrotic syndrome (MCNS) and diffuse mesangial hypercellularity (DMH) evolves to focal segmental glomerulosclerosis (FSGS).

METHODS

Tissues from renal biopsies were examined by light microscopy (LM), immunofluorescence (IF) and, in four cases, by electron microscopy (EM). From a total of 352 nephrotic children, 121 had renal biopsy results as steroid dependent or resistant. A diagnostic renal biopsy was also performed in 331 children with non-nephrotic proteinuria and/or hematuria. A second renal biopsy was performed in 16 children whose renal function was impaired during the follow up. The clinical course of IgM-positive children was compared with that of IgM-negative children.

RESULTS

Of the 121 nephrotic children with renal biopsy, 85 were MCNS. Twenty were IF positive mainly for IgM, six of whom (30%) presented evolution to FSGS, while of the remaining 65 IF-negative children, only three (4.6%) presented evolution to FSGS. Of the total 331 children with non-nephrotic proteinuria and/or hematuria, 139 were diagnosed as IgA--IgG nephropathy, 44 had positive IF for IgM and 148 were IF negative. Of the 44 children IF positive for IgM, seven (15.9%) presented evolution to FSGS, while none of the 148 IF-negative children presented evolution to FSGS. The follow-up time for all children ranged from 1 to 14 years.

CONCLUSIONS

Of IgM nephropathy patients with MCNS and DMH, a significant percentage develop impaired renal function, due to the evolution of FSGS, as revealed by repeat biopsy during long-term follow up.

Retinoic acid reduces glomerular injury in a rat model of glomerular damage

ABSTRACT.: In the reaction of kidneys to injury, cytokine-driven proliferation plays an important role and precedes the development of glomerulosclerosis. There is great interest in agents that may interfere with such proliferation. Therefore, a rat model of mesangioproliferative glomerulonephritis (induced by anti-Thy1.1) was studied, and the effects of all-trans-retinoic acid (all-trans-RA) and isotretinoin, powerful antiproliferative and anti-inflammatory substances, on glomerular damage and cell proliferation were examined. Vehicle-injected control rats were compared with rats treated with daily subcutaneous injections of 10 mg/kg body wt all-trans-RA or 40 mg/kg body wt isotretinoin (n = 9 to 11 per group), using either a pretreatment (days -2 through 8) or posttreatment (days +3 through +8) protocol, i.e., starting before or after the induction of anti-Thy1.1 nephritis, respectively. All-trans-RA prevented the BP increase evoked by anti-Thy1.1 (anti-Thy1.1/vehicle, 112.2 +/- 4.8 mmHg; anti-Thy1.1/RA, 87.5 +/- 2. 5 mmHg; P < 0.001). Treatment with all-trans-RA or isotretinoin produced a 70% decrease in the urinary albumin excretion rate (P < 0. 02). Periodic acid-Schiff staining of saline-perfused kidneys (day 8) revealed significantly fewer glomerular cells in RA-treated nephritic rats (anti-Thy1.1/vehicle, 97 +/- 3.1 cells/glomerulus; anti-Thy1.1/RA, 80 +/- 4.4; P < 0.02; control/vehicle, 69 +/- 1.2). No difference was observed between all-trans-RA and isotretinoin treatment. The capillary occlusion scores were significantly lower for the anti-Thy1.1/RA-treated group (1.9 +/- 0.1) than for the anti-Thy1.1/vehicle-treated group (2.9 +/- 0.5, P < 0.001). In the anti-Thy1.1/vehicle-treated group, 11.9 +/- 1.1 glomerular cells were proliferating cell nuclear antigen-positive; however, in the anti-Thy1.1/RA-treated group, only 5.3 +/- 0.8 cells were proliferating cell nuclear antigen-positive (P < 0.002; control, 2.2 +/- 0.2). Glomerular mitoses were reduced by 67% in the anti-Thy1. 1/RA-treated group, compared with the anti-Thy1.1/control group (P < 0.002). Glomerular staining for platelet-derived growth factor B-chain was significantly reduced in anti-Thy1.1-treated nephritic rats in the presence of isotretinoin or all-trans-RA, compared with the vehicle-treated group (P < 0.001). It is concluded that all-trans-RA limits glomerular proliferation, glomerular lesions, and albuminuria in an established model of renal damage. The findings point to retinoids as potential novel modulators of glomerular injury.

Adult-onset idiopathic nephrotic syndrome associated with pure diffuse mesangial hypercellularity

BACKGROUND

Pure diffuse mesangial hypercellularity (DMH), in its primary form, is a relatively rare histological finding and few data exist in the literature regarding its clinical course and prognosis in nephrotic adults with this diagnosis.

METHODS

We retrospectively analysed the clinical and histological data of 28 adult nephrotic patients (13 male) with this diagnosis with regard to response to the treatment, outcome and prognostic indicators.

RESULTS

Of 25 patients treated with prednisolone (Pred), nine (36%) showed complete remission (CR) of proteinuria, eight (32%) partial remission (PR) and eight (32%) did not respond at all (NR). The combination of cyclosporin treatment with prednisolone of those with PR or NR produced one further complete and two partial remissions. At the end of follow-up (mean 64 months), 10 patients (40%) were in CR, nine (36%) in PR and six (24%) were NR and remained nephrotic. Renal function remained unchanged in patients with CR or PR. In contrast, the six non-responders progressed to end-stage renal disease (ESRD). Compared with non-responders, patients who responded to Pred were older and had normal renal function at presentation. This group also had less mesangial sclerosis and severe tubulointerstitial fibrosis and none showed synechiae with Bowman's capsule. IgM mesangial deposits were observed in 22% of patients with CR in response to Pred, in 37% of those with PR and in 100% of non-responders, who finally progressed to ESRD. A multivariate analysis of clinical and histological features at biopsy showed persistent nephrotic syndrome (P<0.001), the severity of DMH (P<0.03) and the presence of mesangial IgM (P<0. 01) to have independent predictive value for ESRD. This analysis also demonstrated that only mesangial sclerosis (P<0.03) and the presence of mesangial IgM (P<0.002) independently predicted the response to therapy.

CONCLUSIONS

DMH associated with idiopathic nephrotic syndrome is a heterogeneous entity. Patients who respond to therapy (completely or partially) have a benign course similar to that of minimal change nephrotic syndrome. They are usually older and have normal renal function at presentation, whereas 'sclerotic' lesions are less frequent findings in initial biopsies. Non-responders tend to be younger and progress to ESRD. Most of them have impaired renal function at first assessment and more prominent 'sclerotic' lesions on initial biopsies. Mesangial IgM is an independent marker of poorer response to treatment and progression to ESRD but it lacks specificity.

Source of reactive oxygen species in anti-Thy1 nephritis

In proliferative glomerulonephritis, both macrophages and mesangial cells generate reactive oxygen species (ROS), contributing to the development of glomerular injury. We have attempted to determine which cell produces ROS during anti-Thy1 nephritis (ATN) in rats. The generation of ROS was studied using luminol amplified chemiluminescence (GCL) on isolated glomeruli. Immunohistochemical studies used avidin-biotin complex (ABC) to label macrophages and mesangial cells. Immediately after ATN induction, mesangiolysis and infiltration with ED-1 positive cells (referred to as macrophage) was noted with a peak at day 1. After day 4, mesangial proliferation appeared with a decrease of the ED-1 positive cells and a prominent increase of PCNA positive cells (regarded as mesangial cells). In the early phase of ATN, GCL, reflecting ROS generation, increased along with the appearance of ED-1 positive cells. GCL subsequently decreased as mesangial cells increased. This suggested that macrophage were the principal participants in ROS generation in the early phase of ATN although mesangial cells cannot be completely disregarded in the generation of ROS and development of glomerular injury.

Triggering of renal tissue damage in the rabbit by IgG Fc-receptor-positive group A streptococci

Our previous studies have shown that streptococcal IgG Fc receptors (FcR) act to elicit circulating anti-IgG as well as renal glomerular deposition of IgG in rabbits immunized with group A streptococci (GAS). In order to study if other FcR-positive bacteria might have similar effects, rabbits were immunized with either group G streptococci (GGS; strain G148) or Staphylococcus aureus (strain Cowan I) for two periods of 8 and 6 weeks, respectively. At the end of immunization, circulating anti-IgG was found in 6 of 20 (30%) and 4 of 19 (21%) animals receiving G148 and Cowan I, respectively, compared to all 28 receiving FcR-positive GAS strains of types M1, M4, M15 or M22 (p < 0.05 for both comparisons); furthermore, anti-IgG appeared earlier and at higher levels in the GAS groups. Weak glomerular IgG deposits occurred in 5 out of 10 (50%) and 2 out of 8 (25%) animals immunized with G148 and Cowan I, respectively. In contrast, all 11 rabbits examined, given GAS of types M1 or M15, displayed heavy deposits. None of four control animals immunized with either of two FcR-negative strains, GAS type T27 or group B streptococci (GBS) type Ia, exhibited any renal IgG deposits or circulating anti-IgG. Renal tissue materials from rabbits immunized with any of the four FcR-positive GAS strains showed strong inflammatory and degenerative glomerular changes, compatible with the picture seen in acute poststreptococcal glomerulonephritis (APSGN). Only transient renal changes were found in those rabbits immunized with G148 or Cowan I, or the controls injected with the FcR-negative strains, GAS type T27 or GBS. Thus, only the FcR-positive GAS strains showed capacity to induce high levels of anti-IgG, pronounced tissue deposition of IgG as well as irreversible glomerular changes. Our experimental data suggest that streptococcal IgG FcR activity might play an important role in triggering APSGN.

MP84 expression in the urine specimens of acute rejection renal transplant recipients

MP84 is a novel protein synthesized in response to all cytokines. This antigen is expressed only in stimulated mesangial cells and decreased kidney sections, but not in the normal kidney sections (1,2). This study was performed to determine the excretion of MP84 in the urine of renal transplant recipients with acute rejection. Six persons with renal transplant acute rejection and 10 healthy persons were included. Two urine specimens from each person were collected. Dot-blot assay was performed. It was shown that 12 urine specimens from 6 persons with acute rejection revealed MP84 in the matrix dot-blot assay while there was no staining for MP84 in the urine specimens of healthy persons. This could be due to the immunological alteration during the acute rejection which could lead to autocrine and paracrine secretion of growth factors and then the excretion of MP84 in the urine. The mechanism of MP84 secretion is not clear.

Focal segmental glomerulosclerosis

Over the last 2 decades, we have learnt that focal segmental glomerulosclerosis (FSGS) is a ubiquitous phenomenon underlying the progressive deterioration of many different types of renal diseases in both pediatric and adult populations. FSGS may also be the primary renal lesion, whether in new disease entities such as glycogen storage disease and human immunodeficiency virus infection, or in idiopathic FSGS. Although the mechanism which triggers the development of primary FSGS still remains unknown, laboratory and clinical studies have identified several key pathophysiological events leading to end-stage renal disease. While therapeutic modalities have not changed remarkably, a recent study, although uncontrolled, demonstrated an impressive efficacy of intravenous steroid pulse therapy in inducing remission. Nevertheless, it remains largely unknown whether such a forced remission decreases the overall risk of developing chronic renal failure. Studies have revealed an important pathophysiological role of angiotensin and the therapeutic efficacy of angiotensin converting enzyme inhibitors in progressive loss of renal function in diseases where glomerulosclerosis is secondary; however, it remains to be verified whether these results hold true in primary FSGS. As a result of the improvement in allograft survival rate, the benefit of renal transplant outweighs the risk of recurrence of FSGS, hence transplantation continues to be a vital therapy for FSGS patients who have reached renal failure. Thus, FSGS is not one disease, but rather a range of lesions seen in many settings. The type of lesions and the patient's unique genetic factors contribute to prognosis, and also may dictate choice of optimum therapy.

Fundamental concepts and immunosuppressive treatment in the various forms of glomerulonephritis

Immunosuppressive treatment in glomerulonephritis (GN) is still controversial. Most of the secondary forms of glomerulonephritis have the histologic features of one of the primary types of glomerulonephritis. Eight histologic expressions of primary glomerulonephritis can be distinguished and ordered in terms of severity of symptoms and prognosis: endocapillary GN, minimal change GN, mesangioproliferative GN, membranous GN, focal-sclerosing GN, membranoproliferative GN, focal-necrotizing GN, and rapidly progressive GN. Agreement exists only to the extent that immunosuppression is not required in endocapillary glomerulonephritis, although it is recommended in the other extreme of rapidly progressive GN. Primarily, an indication for immunosuppression is given by the severity of symptoms with a urinary protein excretion > 3.5 g per day and/or serum creatinine > 150 mumol per liter. As for anti-GBM, the type of glomerulonephritis is more important than the severity of symptoms in guiding therapy, whereas for IgA nephropathy it is controversial whether the prospective prognosis of even inexorably deteriorating renal function justifies immunosuppression. Renal biopsy is required to identify the type of glomerulonephritis so as to establish the specific immunosuppressive concept with different intensity and duration of treatment. Immunosuppression can reduce urinary protein excretion and improve deterioration of renal function; however, the proportion of patients responding varies with and depends on the different forms of GN.

Plasmapheresis reduces proteinuria and serum capacity to injure glomeruli in patients with recurrent focal glomerulosclerosis

To test the hypothesis that a circulating mediator is associated with recurrent idiopathic focal glomerulosclerosis (FGS), we studied the effect of plasmapheresis on reducing proteinuria in patients with the disease. An in vitro assay measured the capacity of sera before and after plasmapheresis to cause increased albumin permeability (P(albumin)++) in isolated rat glomeruli. Nine patients (five males aged 2 to 66 years) who underwent plasmapheresis for recurrent FGS were identified. Study variables included age, sex, time from diagnosis of recurrence to first pheresis, glomerular hyalinosis, complications, outcome, and proteinuria before and after plasmapheresis. Rat glomeruli were isolated in medium containing 4 g/dL bovine serum albumin, and P(albumin) was determined from the change in glomerular volume in response to an albumin gradient after incubation of the glomeruli in a 1:50 dilution of patient serum. Plasmapheresis reduced proteinuria from a mean of 12 +/- 7.46 g/24 hr to 5.1 +/- 7.39 g/24 hr (P = 0.03). Six patients in whom the diagnosis was made early in the course of the disease and in whom plasmapheresis was initiated immediately had lasting remissions. Preplasmapheresis biopsies in the patients who did not achieve remissions showed both epithelial foot process effacement and glomerular sclerosis. Serum samples were available from four patients for albumin testing in vitro. P(albumin)++ was reduced from a mean of 0.76 +/- 0.17 before pheresis to 0.18 +/- 0.31 after (P = 0.07). Therefore, the mechanism by which plasmapheresis reduces proteinuria in patients with recurrent FGS involves the decreased capacity of sera from these patients to injure the glomerular permeability barrier.(ABSTRACT TRUNCATED AT 250 WORDS)

Failure of clinical and laboratory characteristics to differentiate mesangial proliferative from minimal-change nephrotic syndrome

Twelve clinical and laboratory characteristics of nephrotic syndrome were compared in 24 children with biopsy-proven mesangial proliferative glomerulonephritis (MesPGN) and 17 children with biopsy-proven minimal-change nephropathy (MCNS). The objective of the study was to determine if these characteristics alone, without renal biopsy, could be used to differentiate the two histopathologic entities. Sex, urinary protein level and IgM immunofluorescence were found to be significantly different in the two groups. Discriminant analysis produced two formulae which gave a discriminant rate of 79% for MesPGN and 76% for MCNS. We conclude that the clinical and laboratory characteristics studied could not differentiate MesPGN from MCNS.

Fibronectin turnover in human mesangial cell cultures as affected by adriamycin

Fibronectin (FN) turnover and turnover changes induced by the anticancer drug Adriamycin (ADR) were measured in human mesangial cells (HMC) in vitro. HMC cultures synthesize cellular FN (2.2 +/- 0.3% of total protein synthesis; n = 12) which is secreted and incorporated into a fibrillar extracellular matrix (ECM). A 24 hr incubation of HMC with ADR (0.5-5 micrograms/ml) resulted in an accumulation of FN in the culture medium, with a maximum increase following 5 micrograms/ml (7.3 +/- 2.3 pg/cell vs. controls: 4.4 +/- 1.9 pg/cell; n = 10). Correspondingly, radioactively labeled immunoprecipitable FN was increased in a dosage-dependent manner in the culture medium up to 50% vs. controls. The incorporation of radioactively labeled FN into ECM was significantly increased following 2 micrograms ADR/ml. In accordance, immunofluorescence staining revealed an expansion of pericellular FN fibers in cultures exposed to 2 micrograms ADR/ml. Concomitant with the accumulation of extracellular FN, radioactively labeled FN in the cells was reduced by 22%. Qualitative characterization of FN patterns revealed a diminished number of degradation products in the culture medium of ADR-treated HMC. These data suggest that ADR interferes with the turnover of FN secreted by HMC in vitro in such a way that FN accumulates extracellularly. This in turn leads to a reduced FN synthesis. These findings are compatible with a loss of urinary FN degradation products accompanying the onset of proteinuria in ADR-treated rats.

Expression of transforming growth factor beta is elevated in human and experimental diabetic nephropathy

Diabetes is now the most common cause of progressive kidney failure leading to dialysis or transplantation. The central pathological feature of diabetic nephropathy is accumulation of extracellular matrix within the glomeruli. The factors in the diabetic milieu responsible for extracellular matrix accumulation are not understood. Here we report that in glomeruli of rats made diabetic there is a slow, progressive increase in the expression of transforming growth factor beta (TGF-beta) mRNA and TGF-beta protein. A key action of TGF-beta is induction of extracellular matrix production, and specific matrix proteins known to be induced by TGF-beta were increased in diabetic rat glomeruli. These proteins include an alternatively spliced form of fibronectin, tenascin, and the proteoglycan biglycan. TGF-beta has not previously been implicated in the matrix accumulation that occurs in the diabetic kidney. Glomeruli from humans with diabetic nephropathy also showed a striking increase in immunoreactive TGF-beta protein and deposition of the special form of fibronectin, whereas glomeruli from normal subjects or from individuals with other glomerular diseases (where extracellular matrix accumulation is not a feature) were negative or barely positive. These results implicate TGF-beta in the pathogenesis of diabetic nephropathy.

Heparin suppresses mesangial cell proliferation and matrix expansion in experimental mesangioproliferative glomerulonephritis

Proliferation and extracellular matrix (ECM) overproduction by glomerular mesangial cells characterizes many types of glomerulonephritis and often precedes the development of glomerulosclerosis. Heparin is a potent inhibitor of mesangial cell growth in vitro. We examined whether standard heparin can inhibit mesangial cell proliferation in vivo in the mesangioproliferative anti-Thy 1.1 nephritis. Untreated control rats were compared to rats infused with heparin either early (day -2 to 1) or late (day 2 to 5) after induction of anti-Thy 1.1 nephritis. The results show that heparin treatment significantly reduced mesangial cell proliferation regardless of when it was initiated. Heparin (either early or late treatment) also reduced mesangial basic fibroblast growth factor (bFGF) expression and platelet-derived growth factor (PDGF) receptor up-regulation as reflected by immunostaining, whereas PDGF B-chain expression was reduced only by late heparin treatment. Furthermore, heparin treatment markedly inhibited the mesangial matrix expansion for a variety of ECM proteins, including laminin, type I and IV collagen, fibronectin and entactin. Heparin did not affect the initial mesangiolysis, glomerular macrophage influx, deposition of anti-Thy 1.1 IgG or fibrinogen, or the glomerular platelet influx. These results suggest that heparin, via its antiproliferative rather than anticoagulant effect, can inhibit mesangial cell proliferation, overexpression of polypeptide growth factors, and ECM protein overproduction in vivo. The beneficial effect of heparin can be demonstrated even if treatment is initiated after the development of nephritis. By virtue of these properties, heparin may be an effective agent in the treatment of human mesangioproliferative disease and in the prevention of glomerulosclerosis.

Natural inhibitor of transforming growth factor-beta protects against scarring in experimental kidney disease

The central pathological feature of human kidney disease that leads to kidney failure is the accumulation of extracellular matrix in glomeruli. Overexpression of transforming growth factor-beta (TGF-beta) underlies the accumulation of pathological matrix in experimental glomerulonephritis. Administration of an antibody raised against TGF-beta to glomerulonephritic rats suppresses glomerular matrix production and prevents matrix accumulation in the injured glomeruli. One of the matrix components induced by TGF-beta, the proteoglycan decorin, can bind TGF-beta and neutralize its biological activity, so decorin may be a natural regulator of TGF-beta (refs 3, 4). We tested whether decorin could antagonize the action of TGF-beta in vivo using the experimental glomerulonephritis model. We report here that administration of decorin inhibits the increased production of extracellular matrix and attenuates manifestations of disease, confirming our hypothesis. On the basis of our results, decorin may eventually prove to be clinically useful in diseases associated with overproduction of TGF-beta.

A monoclonal antibody (1G10) recognizes a novel human mesangial antigen

We have identified a unique mesangial matrix protein of the human glomerulus by using a monoclonal antibody, 1G10, generated against culture human glomerular cells. By immunofluorescence, the antigen recognized by 1G10 (1G10 antigen) is present in mesangium and smooth muscle tissue and cannot be detected in any other tissue examined. Immunoelectron microscopy of glomeruli indicated that 1G10 antigen is present exclusively in the mesangial matrix at the endothelial-mesangial interface. The 1G10 antigen is also expressed by cultured mesangial cells, but not by cultured glomerular epithelial cells, umbilical endothelial cells or fibroblasts. 1G10 did not react with the mesangial matrix proteins [fibronectin (FN), laminin (LAM), collagen types I, III, IV, V, and VI (Col I, III, IV, V, VI), heparin sulfate proteoglycan (HSPG), or thrombospondin (TS)] present under normal and diseased states or smooth muscle antigens (myosin, actin), but did react with a 4 M urea extract of renal cortex and a 0.3% deoxycholate extract of isolated glomeruli. Two dimensional immunoblot analysis using the urea extract demonstrated the binding of 1G10 to an approximately 200 KDa polypeptide with pI 6.0. On one dimensional immunoblot this band did not show cross react with polyclonal antisera to FN, LAM, Col IV, V, VI, HSPG or TS. This mesangial matrix component is trypsin and periodate sensitive, suggesting that it has the character of glycoprotein. In renal biopsy specimens from patients with mesangial proliferative glomerulonephritis (GN) and membranoproliferative GN, the expression of the 1G10 antigen increased along with mesangial hypercellularity or increased accumulation of mesangial matrix, but decreased in completely sclerosed glomeruli. No significant changes in 1G10 antigen expression was observed in membranous GN or minimal change nephrosis compared to normal glomeruli. This study suggests that the 1G10 antigen may not only be a useful marker for the clinical assessment of GN, but may also serve as a potential tool for the study of the pathogenesis of glomerular diseases characterized by cellular proliferation and mesangial matrix expansion.