iMN Patients Research Articles

Effect of Low-Density Lipoprotein Apheresis for Nephrotic Idiopathic Membranous Nephropathy as Initial Induction Therapy.

Low-density lipoprotein apheresis (LDL-A) has been used for nephrotic syndrome (NS) caused by focal segmental glomerulosclerosis in Japan. Idiopathic membranous nephropathy (iMN) can also cause treatment-resistant NS. Therefore, we investigated the effect of LDL-A during initial induction for it. This retrospective, observational, and single-center study enrolled consecutive iMN patients who received steroids from March 2000 to May 2015. We compared data between 11 patients treated with LDL-A (LDL-A group) and 27 patients without (non-LDL-A group) at baseline and 4 and 8 weeks later. Reduction rate of proteinuria and increase rate of serum albumin in LDL-A group were significantly higher than the other after 4 weeks (P = 0.036 and 0.030) and 8 weeks (P = 0.030 and <0.001), respectively. There was no adverse event caused by LDL-A and immunosuppressant dose was not significantly different. In conclusion, LDL-A may be an effective choice for initial induction of nephrotic iMN.

Lipid metabolism participates in human membranous nephropathy identified by whole-genome gene expression profiling.

A genomics approach is an effective way to understand the possible mechanisms underlying the onset and progression of disease. However, very limited results have been published regarding whole-genome expression analysis of human idiopathic membranous nephropathy (iMN) using renal tissue. In the present study, gene expression profiling using renal cortex tissue from iMN patients and healthy controls was conducted; differentially expressed genes (DEGs) were filtered out, and 167 up- and 291 down-regulated genes were identified as overlapping DEGs (ODEGs). Moreover, enrichment analysis and protein-protein network construction were performed, revealing enrichment of genes mainly in cholesterol metabolism and arachidonic acid metabolism, among others, with 38 hub genes obtained. Furthermore, we found several associations between circulating lipid concentrations and hub gene signal intensities in the renal cortex. Our findings indicate that lipid metabolism, including cholesterol metabolism and arachidonic acid metabolism, may participate in iMN pathogenesis through key genes, including apolipoprotein A1 (APOA1), apolipoprotein B (APOB), apolipoprotein C3 (APOC3), cholesteryl ester transfer protein (CETP), and phospholipase A2 group XIIB (PLA2G12B).

A comparison of cyclophosphamide versus tacrolimus in terms of treatment effect for idiopathic membranous nephropathy: A meta-analysis

Background and aimsIdiopathic membranous nephropathy (IMN), which is considered one of the most common causes of nephrotic syndrome in adult patients, is frequently managed with immunosuppressive agents. Both tacrolimus (TAC) and cyclophosphamide (CTX) are recommended as immunosuppressive agents in the management of IMN. However, profound effects and moderate evidence on the two drugs remains poorly defined at this period. The meta-analysis aims to summarize current best evidence on the efficacy as well as safety of TAC and CTX among IMN patients. MethodsWe searched the publications on comparison of the safety and efficacy of TAC versus CTX for IMN up to April 2018. After rigorous reviewing on the quality, the data was extracted from eligible trials. All trials analyzed the summary hazard ratios (HRs) of the endpoints of interest. ResultsModerate-strong evidence indicated that tacrolimus and cyclophosphamide had comparable effects on remission rate (either CR or PR) (p>0.05). No significant differences were found in the following parameters: the rates of diarrhea, glucose intolerance (or diabetes mellitus), gastrointestinal syndrome, as well as hypertension because of adverse effects (p>0.05). However, patients with TAC therapy had a higher chance to develop urinary tract infection (p=0.010) and tremor (p=0.006). Additionally, remarkably higher risk existed in leukopenia among the CTX group as compared with the TAC group (p=0.03). ConclusionThis meta-analysis presents a comprehensive assessment of current available evidence for the therapy of IMN, indicating a comparable remission rate with both TAC and CTX, while the long-term effects are needed for further verification. Nevertheless, different adverse effect profiles of two groups need careful consideration. Remarkably higher rates of urinary tract infection and tremor were observed among TAC group, while higher risk of leukopenia was found among CTX group. Further research into the treatment efficacy of both drugs is warranted to confirm the present conclusions.

Low serum C3 level, high neutrophil-lymphocyte-ratio, and high platelet-lymphocyte-ratio all predicted poor long-term renal survivals in biopsy-confirmed idiopathic membranous nephropathy

Idiopathic membranous nephropathy (iMN) is the major cause of end-stage renal disease (ESRD). Recent guidelines suggest limiting immunosuppressants only to high risk patients for ESRD. The present study is aimed at identifying new predictors for the renal outcome of iMN patients. We conducted a retrospective cohort study covering a period from January 2003 to December 2013. We enrolled participants who had received their first renal biopsy at our medical center in Taiwan with the diagnosis of iMN. Clinical, pathological and laboratory data were collected from medical records. Analyses with Mann–Whitney U test was used for continuous variables and Chi-square test for categorical variables. The Kaplan-Meier curve was used for the analyses of patient survival and renal survival. Youden index was used for evaluating the performance of a dichotomous diagnostic test for renal and patient outcomes. Cox proportional hazard regression was used to determine factors affecting renal survival.A total of 99 patients with renal biopsy-confirmed idiopathic iMNs were enrolled. C3 level ≤114 mg/dl predicted patient outcome (p < 0.001) with good predictive power (AUC = 0.736). The univariate analysis showed that risk factors for poor renal outcome were older age (HR = 1.04, p = 0.002), high BUN (HR = 1.03, p < 0.001), poor baseline renal function (HR = 1.30 and p < 0.001 for higher serum creatinine; HR = 0.97 and p < 0.001 for higher eGFR; HR = 1.06 and p < 0.001 for urine PCR), C3 ≤ 93.4 mg/dl (HR = 2.15, p = 0.017), NLR > 3.34 (HR = 3.30, p < 0.001) and PLR > 14.48 (HR = 2.54, p = 0.003). Stage of iMN did not fully account for the risk of ESRD. This is the first evidence that serum levels of C3 ≤ 93.4 mg/dl predicted poor renal outcomes with good predictive power. Easily obtained markers, NLR > 3.34 also predicted poor renal outcomes.

A comparison of cyclophosphamide versus tacrolimus in terms of treatment effect for idiopathic membranous nephropathy: A meta-analysis

Background and aimsIdiopathic membranous nephropathy (IMN), which is considered one of the most common causes of nephrotic syndrome in adult patients, is frequently managed with immunosuppressive agents. Both tacrolimus (TAC) and cyclophosphamide (CTX) are recommended as immunosuppressive agents in the management of IMN. However, profound effects and moderate evidence on the two drugs remains poorly defined at this period. The meta-analysis aims to summarize current best evidence on the efficacy as well as safety of TAC and CTX among IMN patients. MethodsWe searched the publications on comparison of the safety and efficacy of TAC versus CTX for IMN up to April 2018. After rigorous reviewing on the quality, the data was extracted from eligible trials. All trials analyzed the summary hazard ratios (HRs) of the endpoints of interest. ResultsModerate-strong evidence indicated that tacrolimus and cyclophosphamide had comparable effects on remission rate (either CR or PR) (p>0.05). No significant differences were found in the following parameters: the rates of diarrhea, glucose intolerance (or diabetes mellitus), gastrointestinal syndrome, as well as hypertension because of adverse effects (p>0.05). However, patients with TAC therapy had a higher chance to develop urinary tract infection (p=0.010) and tremor (p=0.006). Additionally, remarkably higher risk existed in leukopenia among the CTX group as compared with the TAC group (p=0.03). ConclusionThis meta-analysis presents a comprehensive assessment of current available evidence for the therapy of IMN, indicating a comparable remission rate with both TAC and CTX, while the long-term effects are needed for further verification. Nevertheless, different adverse effect profiles of two groups need careful consideration. Remarkably higher rates of urinary tract infection and tremor were observed among TAC group, while higher risk of leukopenia was found among CTX group. Further research into the treatment efficacy of both drugs is warranted to confirm the present conclusions.

Serum phospholipase A2 receptor antibodies and immunoglobulin G subtypes in adult idiopathic membranous nephropathy: Clinical value assessment

BackgroundIdiopathic membranous nephropathy (IMN) is widely considered as an organ-specific autoimmune disorder. Implicated in its pathogenesis are the phospholipase A2 receptors (PLA2R) expressed on glomerular podocytes against which serum antibodies are formed. In this study we quantified and assessed the clinical value of total serum PLA2R antibodies and the subtype antibodies in IMN. MethodsWe measured serum levels of total PLA2R antibodies and IgG subtype antibodies by Enzyme Linked Immunosorbent Assay (ELISA) in 146 biopsy-proven IMN patients, 51 non-IMN patients and 62 healthy controls. We went ahead and determined the diagnostic potential of total serum PLA2R antibodies and assessed if a relationship exists between the dominat subtype antibody and the clinical parameters. ResultsThe diagnostic sensitivity and specificity of total serum PLA2R antibody for IMN were found at 69.9% and 100% respectively. Significant differences in systolic blood pressure, serum Cystatin C, serum albumin and estimated glomerular filtration rate (eGFR) were found between the antibody-positive and antibody-negative groups of IMN patients. Subtype antibody 4 and 1 exhibited the highest positive rates of 94.4% and 91.6% respectively. The mean serum proportion of subtype antibodies was 65.4, 12.7, 7.6 and 4.6% for subtype 4, 1, 3 and 2 respectively. Serum levels of total protein and albumin were significantly decreased among patients with high serum titres of antibody subtype 4. ConclusionOur findings underscore the diagnostic potential of total serum PLA2R antibodies and highlight the importance of antibody subtype 4 over other subtype antibodies in IMN.

The elevated levels of urinary angiotensinogen are correlated with the severity of idiopathic membranous nephropathy

BackgroundImmunosuppressive treatment will predispose an idiopathic membranous nephropathy (iMN) patient to opportunistic infections. Disease severity is one of the main concerns for making the treatment decision. Urinary angiotensinogen (UAGT) level has been shown highly correlated with intrarenal renin-angiotensin system (RAS) activity and severity of chronic kidney diseases (CKD). We aimed to test the relationship between the UAGT level and the severity of iMN.MethodsThis cross-sectional study included a total of 48 biopsy-proven iMN patients, 46 minimal change disease (MCD) patients, and 44 healthy volunteers. The clinical and laboratory data and urine samples were collected from all subjects before the use of RAS inhibitors. We determined the UAGT levels with a method of enzyme-linked immunosorbent assay.ResultsThe UAGT levels were not different between the iMN (277.05 ± 61.25, μg/g.Cr) and MCD patients (244.19 ± 40.24, μg/g.Cr), but both of them were significantly higher than those of healthy controls (6.85 ± 1.10, μg/g.Cr). UAGT levels were correlated negatively with serum albumin (r = − 0.393, p = 0.006) and estimated glomerular filtration rate (eGFR) (r = − 0.352, p = 0.014) and positively with 24-h proteinuria (r = 0.614, p < 0.001) in iMN patients but not in MCD patients. Multivariate linear regression analysis revealed that only proteinuria independently determinate the levels of UAGT (β = 0.649, p < 0.001) in iMN patients.ConclusionsUAGT levels were correlated negatively with serum albumin and glomerular filtration rate and positively with proteinuria in iMN patients at the onset. This suggests that elevated levels of UAGT are associated with the severity of iMN. The UAGT level may be used as a cofactor for deciding immunosuppressive therapy in iMN patient.

Retrospective analysis of tacrolimus combined with Tripterygium wilfordii polyglycoside for treating idiopathic membranous nephropathy

BackgroundIdiopathic membranous nephropathy (IMN) is one of the most common adult nephrotic syndromes. Some patients with this disorder require immunosuppressive therapy. This retrospective case series was performed to assess the effects of tacrolimus (TAC) combined with Tripterygium wilfordii polyglycoside (TWG) in treating IMN.MethodsFrom January 2015 to August 2016, kidney-biopsy-proven IMN patients treated with TAC in the Chinese PLA General Hospital were screened. Data were retrieved from the patients’ medical records. The first efficacy evaluation index was remission rate (complete remission and partial remission), and the secondary efficacy evaluation indices included relapse rate, proteinuria, serum albumin and estimated glomerular filtration rate (eGFR). Adverse events were also assessed.ResultsThe included patients’ treatments were tacrolimus monotherapy (TAC group, n = 33), tacrolimus combined with methylprednisolone (MP) (TAC + MP group, n = 24) and tacrolimus combined with Tripterygium wilfordii polyglycoside (TAC + TWG group, n = 21). The remission rates of the TAC, TAC + MP, and TAC + TWG groups in the 10th month were 54.5, 62.5, and 85.7%, respectively (TAC + TWG group vs TAC group, P = 0.037, TAC + TWG group vs TAC + MP group, P = 0.125). Moreover, the complete remission rates of the TAC, TAC + MP, and TAC + TWG groups in the 10th month were 21.2, 20.8, and 57.1%, respectively (TAC + TWG group vs TAC group, P = 0.007, TAC + TWG group vs TAC + MP group, P = 0.012). Compared with the TAC group, the TAC + TWG group had a higher remission rate during these ten months (log-rank, P = 0.005). Compared with the TAC and TAC + MP groups, the TAC + TWG group had a higher complete remission rate (log-rank, P = 0.019 and log-rank, P = 0.005, respectively).ConclusionThis retrospective study showed that TAC combined with TWG may be effective for treating IMN. Further randomized controlled trials (RCTs) are needed to assess the efficacy and safety of TAC combined with TWG.

The long-term therapeutic effects of two ponticelli methods in the treatment of idiopathic membranous nephropathy

Objective To investigate the long-term clinical effects of two ponticelli methods in the treatment of idiopathic membranous nephropathy. Methods All 88 patients of idiopathic membranous nephropathy were divided into two groups according to different methods. One group(n=40) received oral therapy of CTX(100 mg/d, cumulative dose 8~10 g), and another group(n=40) were treated with monthly intravenous therapy of CTX(0.8~1.0 mg/d, cumulative dose 8~10 g). All patients received treatment of metacortandracin, which was gradually reduced during 8~12 weeks. At the end of study, the clinical remission rate, complication rate, recurrence rate and lost rate were evaluated in two groups. Results Compared with the oral CTX group, the clinical remission rate was decreased for 3 months in intravenous CTX group(10% vs. 6%, P<0.05), and the peak value of remission rate was 12 months. The side-effect of recurrence rate, lost rate and low white blood cell count in oral group were higher than intravenous CTX group(P<0.05). Conclusions The early clinical remission rate is better in oral group, however, there is no difference on the long-term clinical effect between two groups. In a word, the combination of CTX and metacortandracin is for IMN patients. Moreover, compared with the intravenous CTX group, the complication rate, recurrence rate and lost rate are higher than oral CTX group.The therapy of oral CTX may be more security, however, more studies of long-term observation are needed to make the evidence stronger. Key words: Glomerulonephritis, Membranous; Prednisone

Rituximab for non-responsive idiopathic membranous nephropathy in a Chinese cohort.

Rituximab had been shown to be effective in inducing remission of nephrotic syndrome in patients with idiopathic membranous nephropathy (iMN). This study applied rituximab therapy for 36 non-responsive iMN patients to investigate its effects and safety. Thirty-six iMN patients who were non-responsive to prior immunosuppression were enrolled. Rituximab was used for B-cell depletion in patients, with a goal of <5 B cells/mm3 in the circulation. After completing the study, patients were monitored for a median of 12.0 months [interquartile range (IQR) 9.0-19.3]. Fifteen of the 36 (41.7%) patients achieved partial (n = 13) or complete (n = 2) response to the rituximab treatment. The median time for achieving partial response was 4.0 months (IQR 3.0-6.0). The responders had relatively lower levels (118 ± 112 U/mL versus 345 ± 357 U/mL, P = 0.03) of anti-phospholipase 2 receptor (PLA2R) antibodies before the rituximab treatment, and all of them achieved antibody depletion or reduction. B-cell depletion was achieved in all patients. Renal function remained stable in the responders [estimated glomerular filtration rate (eGFR) 53.3 ± 40.5 versus 55.6 ± 33.2 mL/min/1.73m2, P = 0.67] but deteriorated in the non-responders (eGFR 57.5 ± 29.3 versus 45.3 ± 32.8 mL/min/1.73m2, P = 0.02) with two patients reaching end-stage kidney disease. Two of the 15 patients relapsed during the follow-up period with anti-PLA2R antibody reoccurrence and B-cell reconstitution. The second course of rituximab combined with tacrolimus induced a faster partial response again in one patient. Rituximab therapy could induce remission of proteinuria and stabilization of renal function in non-responsive iMN patients, even those with damaged renal function. Anti-PLA2R antibodies may be used as a marker for individualized rituximab dosage and treatment monitoring.

Diagnostic specificity of autoantibodies to M-type phospholipase A2 receptor (PLA2R) in differentiating idiopathic membranous nephropathy (IMN) from secondary forms and other glomerular diseases.

Autoantibody against phospholipase A2 receptor (anti-PLA2R) is a sensitive and specific biomarker of idiopathic membranous nephropathy (iMN), being found in approximately 70% of iMN patients and only occasionally in other glomerular diseases. However, whereas its diagnostic specificity vs. normal controls and other glomerulonephritides (GN) has been firmly established, its specificity vs. membranous nephropathy associated with various diseases (sMN) has given inconsistent results. The aim of our study was to evaluate the prevalence of anti-PLA2R antibodies in iMN in comparison with various control groups, including sMN. A total of 252 consecutive iMN patients, 184 pathological and 43 healthy controls were tested for anti-PLA2R antibody using indirect immunofluorescence (PLA2R IIFT, Euroimmun). Anti-PLA2R autoantibodies were detectable in 178/252 iMN patients, 1/80 primary GN, 0/72 secondary GN, 9/32 sMN and 0/43 healthy controls, with a diagnostic sensitivity of 70.6%. The diagnostic specificity of anti-PLA2R antibody vs. normal and pathological controls was 100 and 94.6% respectively. However, when the diagnostic specificity was calculated only vs. secondary forms of MN, it decreased considerably to 71.9%. Interestingly enough, 9 out of 10 anti-PLA2R positive patients in the disease control groups had membranous nephropathy associated with various diseases (7 cancer, 1 Crohn's disease, 1 scleroderma). In conclusion, anti-PLA2R positivity in a patient with MN, should not be considered sufficient to abstain from seeking a secondary cause, especially in patients with risk factors for neoplasia. The causal relationship between tumors and anti-PLA2R-induced MN remains to be established, as well as the possible mechanisms through which malignancies provoke autoimmunity.

Renal Phospholipase A2 Receptor and the Clinical Features of Idiopathic Membranous Nephropathy.

Background:According to the renal phospholipase A2 receptor (PLA2R) immunohistochemistry, idiopathic membranous nephropathy (iMN) could be categorized into PLA2R-associated and non-PLA2R-associated iMN. This study aimed to examine whether the non-PLA2R-associated iMN had any difference in clinical features compared with PLA2R-associated iMN.Methods:A total of 231 adult patients diagnosed as iMN were recruited to this retrospective study. Renal PLA2R expression was examined by immunofluorescence. Among these patients, 186 (80.5%) with complete baseline clinical data were used for further study. Urinary protein excretion, serum albumin, and creatinine were analyzed. For those patients with follow-up longer than 1 year, the relationship between PLA2R and response to immunosuppressants were analyzed. The t-test was used for parametric analysis and the Mann-Whitney U-test was used for nonparametric analysis. Categorical variables were described as frequencies or percentages, and the data were analyzed with Pearson's Chi-square test or Fisher's exact test.Results:Of the 231 iMN patients, 189 showed renal detectable PLA2R expression (81.8%). The baseline serum creatinine, serum albumin, and urine protein excretion were not significantly different between PLA2R-associated (n = 145) and non-PLA2R-associated iMN patients (n = 41). However, about 1/3 of the non-PLA2R-associated iMN had abnormal serological tests, significantly more common than PLA2R-associated iMN (31.7% vs. 8.3%, P = 0.000). The non-PLA2R-associated iMN had lower C4 levels compared with PLA2R-associated iMN (P = 0.004). The non-PLA2R-associated iMN patients also showed a better response to immunosuppressants (complete remission [CR] 42.9%; partial remission [PR] 14.3%) compared with PLA2R-associated iMN (CR 3.2%; PR 48.4%, P = 0.004) at the 3rd month.Conclusions:There were no significant differences in serum creatinine, albumin, and urine protein excretion between PLA2R-associated and non-PLA2R-associated iMN, while the non-PLA2R-associated iMN patients showed more abnormal serological tests. The non-PLA2R-associated iMN seemed to respond more quickly to the immunosuppressive therapy compared with PLA2R-associated iMN.

Factors affecting the long-term outcomes of idiopathic membranous nephropathy

BackgroundWe attempted to describe the clinical features and determine the factors associated with renal survival in idiopathic membranous nephropathy (iMN) patients with nephrotic syndrome (NS) and to determine the factors associated with spontaneous complete remission (sCR) and progression to NS in iMN patients with subnephrotic proteinuria.MethodsThis retrospective study involved 166 iMN patients with NS and 65 patients with subnephrotic proteinuria. The primary end point was a doubling of serum creatinine or initiation of dialysis. In patients with subnephrotic proteinuria, we determined the factors associated with sCR and factors associated with progression to NS.ResultsRemission of NS was achieved in 125 out of 166 patients (75.3%). Of those who reached remission, 26 patients (20.8%) experienced relapse that was followed by second remission. The relapse or persistence of proteinuria was associated with the primary end points (hazard ratio [HR] = 12.40, P = 0.037, HR = 173, P < 0.001, respectively). In patients with subnephrotic proteinuria, sCR occurred in 35.4% of the patients. The patients with sCR had lower proteinuria and serum creatinine levels and higher serum albumin concentrations at baseline. The serum albumin level at diagnosis was a prognostic factor for progression to NS (Odds ratio [OR] = 0.015, P < 0.001).ConclusionsThe occurrence of relapse or persistence of proteinuria had negative effects on renal survival in iMN patients with NS, and low serum albumin levels at baseline were associated with non-achievement of sCR and progression to NS.

Anti-phospholipase A2 receptor antibody levels at diagnosis predicts spontaneous remission of idiopathic membranous nephropathy.

Background: The diagnostic role of circulating anti-phospholipase A2 receptor antibodies (anti-PLA2R Abs) is now well recognized in idiopathic membranous nephropathy (iMN). These Abs could also be interesting as predictors of clinical outcome. In this study, we explored the prognostic value of anti-PLA2R Abs measured in a cohort of iMN patients, with a special focus on their ability to detect patients achieving spontaneous remission. Methods: All adult patients with biopsy-proven iMN diagnosed between 1978 and 2007 were retrospectively screened in our centre. Using a validated enzyme-linked immunosorbent assay, levels of anti-PLA2R Abs were measured from serum samples obtained at the time of renal biopsy and stored at −80°C until processing. Clinical data on disease activity, treatments and outcomes were collected by reviewing patients’ medical records. The association between anti-PLA2R Ab titres and clinical activity/outcome was assessed by Cox proportional hazard and Kaplan–Meier methods. Results: In this retrospective study, 68 patients were included in the final analysis (median follow-up of 81 months). No significant association was found between anti-PLA2R Ab titres at diagnosis with baseline proteinuria, baseline estimated glomerular filtration rate or chronic kidney disease progression. Spontaneous remission was observed in 22% of patients. Ab titres were significantly and gradually correlated in a dose–response manner with the likelihood of spontaneous remission. Conclusions: While Ab titres measured at diagnosis were not found to predict the activity of iMN, evaluation of anti-PLA2R Ab titres might prove useful in the early identification of patients likely to achieve spontaneous remission.

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.

M-type phospholipase A2 receptor (PLA2R) glomerular staining in pediatric idiopathic membranous nephropathy.

Identifying M-type phospholipase A2 receptor (PLA2R) is a landmark breakthrough for understanding adult idiopathic membranous nephropathy (iMN). However, potential roles for PLA2R in pediatric iMN have not been well investigated. A total of 34 pediatric iMN patients who underwent kidney biopsy between 1972 and 2015 were enrolled in this study. The study cohort consisted of 15 children aged from 3 to 9years and 19 aged from 10 to 15years. In all cases, secondary causes of MN, including infections, autoimmune diseases, and others, were ruled out. We examined PLA2R glomerular staining in stored, formalin-fixed, paraffin-embedded kidney biopsy samples. Kidney biopsy specimens obtained from an adult patient with iMN and an adult patient with lupus-associated MN were also examined to assess our PLA2R staining procedure. Granular staining of PLA2R along glomerular capillary loops was present in two patients: an 11-year-old girl and 12-year-old boy identified during a school urine screening test and who presented with mild proteinuria at the time of biopsy. Interestingly, the intensity of PLA2R glomerular staining in these patients was weaker than that of a PLA2R-positive adult iMN patient. There were no PLA2R-positive patients among our cohort of children younger than 10years. This preliminary study suggests PLA2R may play a role in some adolescent and preteen iMN patients but may be less frequently associated with iMN during childhood.

The putative role of MALDI-MSI in the study of Membranous Nephropathy

Membranous Nephropathy (MN) is an immunocomplex mediated renal disease that represents one of the most frequent glomerulopathies worldwide. This glomerular disease can manifest as primary (idiopathic) or secondary and this distinction is crucial when choosing the most appropriate course of treatment. In secondary cases, the best strategy involves treating the underlying disease, whereas in primary forms, the identification of confirmatory markers of the idiopathic etiology underlining the process is requested by clinicians. Among those currently reported, the positivity to circulating antigens (PLA2R, IgG4 and THSD7A) was demonstrated in approximately 75% of iMN patients, while approximately 1 in 4 patients with iMN still lack a putative diagnostic marker. Ultimately, the discovery of biomarkers to help further stratify these two different forms of glomerulopathy seems mandatory.Here, MALDI-MSI was applied to FFPE renal biopsies from histologically diagnosed primary and secondary MN patients (n=20) in order to detect alterations in their tissue proteome. MALDI-MSI was able to generate molecular signatures of primary and secondary MN, with one particular signal (m/z 1459), identified as Serine/threonine-protein kinase MRCK gamma, being over-expressed in the glomeruli of primary MN patients with respect to secondary MN. Furthermore, a number of signals that could differentiate the different forms of iMN that were positive to PLA2R or IgG4 were detected, as well as a further set of signals (m/z 1094, 1116, 1381 and 1459) that could distinguish these patients from those who were negative to both. These signals could potentially represent future targets for the further stratification of iMN patients. This article is part of a Special Issue entitled: MALDI Imaging, edited by Dr. Corinna Henkel and Prof. Peter Hoffmann.

Immunology of membranous nephropathy: from animal models to humans.

Membranous nephropathy (MN), the leading cause of nephrotic syndrome in adults, is characterized by the deposition of subepithelial immune deposits that consist mainly of immunoglobulin (Ig)G and complement. Most of the cases are primary or idiopathic (iMN), while only approximately 25% of the cases are secondary to some known disease such as systemic lupus erythematosus, hepatitis B, drugs and malignancies. Most of our knowledge on the pathogenesis of iMN has relied upon old experimental models (i.e. Heymann nephritis) that have shown that immune deposits are formed in situ by the reaction of autoantibodies against the respective podocyte antigen. Recent findings indicate that podocyte proteins also act as an autoantigen in human iMN. The M-type phospholipase A2 receptor (PLA2R) has been identified as the main target antigen, as it can be found in approximately 70% of iMN patients but only rarely in other glomerulonephritides. Podocytes damage in the experimental model of Heymann nephritis is complement-mediated. In humans, the presence of complement within the subepithelial deposits is well established, but IgG4, which does not activate complement by classical or alternative pathways, represents the predominant subclass of IgG anti-PLA2R. Some evidence suggests that IgG4 anti-PLA2R autoantibodies can bind mannan-binding lectin (MBL) and activate the lectin complement pathway. A genetic background for iMN has been demonstrated by genome-wide association studies that have shown highly significant associations of the PLA2R1 and the human leucocyte antigen (HLA)-DQA1 loci with iMN. In addition to their diagnostic value, anti-PLA2R antibodies may be useful to monitor disease activity and predict response to treatment.

Cross-reactivity of anti-PLA2R1 autoantibodies to rabbit and mouse PLA2R1 antigens and development of two novel ELISAs with different diagnostic performances in idiopathic membranous nephropathy.

About 70% of patients with idiopathic membranous nephropathy (iMN) have autoantibodies to the phospholipase A2 receptor PLA2R1. We screened sera from iMN patients for their cross-reactivity to human (h), rabbit (rb) and mouse (m) PLA2R1 by western blot (WB) and antigen-specific ELISAs. All iMN patients recognized hPLA2R1 and rbPLA2R1 by WB, and a rbPLA2R1 ELISA was as sensitive as the standardized hPLA2R1 ELISA to monitor anti-PLA2R1 in patients with active disease or in drug-induced remission. In contrast, only 51% of patients were reactive to mPLA2R1 by WB, and a maximum of 78% were weakly to highly positive in the mPLA2R1 ELISA, suggesting that iMN patients exhibit different subsets of anti-PLA2R1 autoantibodies against epitopes that are shared or not among PLA2R1 orthologs. In a cohort of 41 patients with a mean follow-up of 42 months from anti-PLA2R1 assay, the detection of anti-mPLA2R1 autoantibodies was an independent predictor of clinical outcome in multivariate analysis (p=0.009), and a ROC curve analysis identified a threshold of 605 RU/mL above which 100% of patients (12 patients) had a poor renal outcome (p<0.001). A similar threshold could not be defined in hPLA2R1 and rbPLA2R1 ELISAs. We conclude that rbPLA2R1 is an alternative antigen to hPLA2R1 to measure anti-PLA2R1 in active disease while mPLA2R1 is a unique antigen that can detect a subset of anti-PLA2R1 autoantibodies present at high levels (>605RU/mL) only in iMN patients at risk of poor prognosis, and is thus useful to predict iMN outcome.

TRPC6 single nucleotide polymorphisms and progression of idiopathic membranous nephropathy.

BackgroundActivating mutations in the Transient Receptor Potential channel C6 (TRPC6) cause autosomal dominant focal segmental glomerular sclerosis (FSGS). TRPC6 expression is upregulated in renal biopsies of patients with idiopathic membranous glomerulopathy (iMN) and animal models thereof. In iMN, disease progression is characterized by glomerulosclerosis. In addition, a context-dependent TRPC6 overexpression was recently suggested in complement-mediated podocyte injury in e.g. iMN. Hence, we hypothesized that genetic variants in TRPC6 might affect susceptibility to development or progression of iMN.Methods & ResultsGenomic DNA was isolated from blood samples of 101 iMN patients and 292 controls. By direct sequencing of the entire TRPC6 gene, 13 single nucleotide polymorphisms (SNPs) were identified in the iMN cohort, two of which were causing an amino acid substitution (rs3802829; Pro15Ser and rs36111323, Ala404Val). No statistically significant differences in genotypes or allele frequencies between patients and controls were observed. Clinical outcome in patients was determined (remission n = 26, renal failure n = 46, persistent proteinuria n = 29, follow-up median 80 months {range 51–166}). The 13 identified SNPs showed no association with remission or renal failure. There were no differences in genotypes or allele frequencies between patients in remission and progressors.ConclusionsOur data suggest that TRPC6 polymorphisms do not affect susceptibility to iMN, or clinical outcome in iMN.