Membranous Nephropathy: A Journey From Bench to Bedside

Lupus nephritis: redefining the treatment goals

The course of proliferative lupus nephritis is characterized by flares of activity alternating with periods of quiescence against a background of chronic immune dysregulation. An accurate assessment of disease activity is of unassailable importance to tailor therapy. In the present communication, we discuss the available clinical, serologic, and histologic tools to evaluate disease activity and how they may be applied to redefine the treatment goals in lupus nephritis. Traditionally, treatment response is judged by the degree of proteinuria reduction and improvement of kidney function, but this fails to differentiate ongoing inflammatory disease from chronic damage. Despite intensive research, no novel biomarker has proved useful for clinical practice, and we continue to rely on anti-double-stranded DNA antibody levels to assess serologic activity. Repeat kidney biopsies sometimes reveal persistent inflammation despite apparent clinical remission, giving credibility to the conviction that histologic remission should be a treatment goal and protocol biopsies be part of the decision-making process. However, the discrepancies between clinical and histologic responses to therapy can be explained by persistent systemic autoimmunity with low-grade immune complex deposition or, alternatively, by delayed clearance of intrarenal inflammation once immunologic remission has been achieved. Because persistent immune dysregulation is the motor of disease activity in lupus nephritis, it should be the principal focus of therapy and monitoring. We propose to replace the traditional induction-remission maintenance protocol by a more dynamic and individualized approach and aim for 3 treatment goals, concomitantly rather than sequentially: (i) clinical remission, by attenuating renal inflammation, using microscopic hematuria, proteinuria, estimated glomerular filtration rate, and complement levels as biomarkers; (ii) immunologic remission, by decreasing immune complex generation, using anti-double-stranded DNA antibody as a biomarker; and (iii) preservation of kidney function, by curtailing chronic kidney damage, using estimated glomerular filtration rate slope as a biomarker.

Post-transplant glomerular diseases: update on pathophysiology, risk factors and management strategies

In recent years, advancements in immunosuppressive medications and post-transplant management have led to a significant decrease in acute rejection rates in renal allografts and consequent improvement in short-term graft survival. In contrast, recent data have shown an increased incidence of post-transplant glomerular diseases, which currently represent a leading cause of allograft loss. Although pathogenesis is not fully understood, growing evidence supports the role of inherited and immunological factors and has identified potential pre- and post-transplant predictors. In this review, we illustrate recent advancements in the pathogenesis of post-transplant glomerular disease and the role of risk factors and immunological triggers. In addition, we discuss potential prevention and management strategies.

Antimalarials in Lupus Nephritis: How Strong Is the Evidence?

SLE is a chronic multisystem autoimmune disease that affects the kidneys in approximately 50% of patients, with the prevalence rising to as high as 70% in certain populations, such as African American and Asian people. Antimalarials-and particularly hydroxychloroquine (HCQ)-are currently considered a mainstay of therapy, together with immunosuppressants. Over the past decades, several studies have extensively investigated the mechanisms of action of antimalarial agents and their potential beneficial properties in patients with SLE in general. However, the evidence for the therapeutic benefit of HCQ in patients with lupus nephritis (LN) derives mainly from observational studies, conducted in an era before the refinement of induction and maintenance protocols for immunosuppressive therapy. Despite the paucity of high-quality evidence on its efficacy in LN, the nephrology community widely supports the universal use of HCQ in patients with LN, and recommendations for its use are firmly entrenched in various clinical practice guidelines. Nonetheless, the use of antimalarials may also carry inherent risks, underscoring the importance of personalized approaches in these patients. Herein, we comprehensively review the available literature on antimalarials in LN, aiming to update the current evidence, limitations, and future perspectives for the use of antimalarials in adults.

THSD7A as a Promising Biomarker for Membranous Nephrosis

Membranous nephropathy (MN) is an autoimmune disease of the kidney glomerulus and one of the leading causes of nephrotic syndrome. The disease exhibits heterogeneous outcomes with approximately 30% of cases progressing to end-stage renal disease. Traditionally, the standard approach of diagnosing MN involves performing a kidney biopsy. Nevertheless, kidney biopsy is an invasive procedure that poses risks for the patient including bleeding and pain, and bears greater costs for the health system. The clinical management of MN has steadily advanced owing to the identification of autoantibodies to the phospholipase A2 receptor (PLA2R) in 2009 and thrombospondin domain-containing 7A (THSD7A) in 2014 on the podocyte surface. At present, serum anti-PLA2R antibody detection and glomerular PLA2R antigen staining have been used for clinical diagnosis and prognosis, but the related detection of THSD7A has not been widely used in clinical practice. Here, we summarized the emerging knowledge regarding the roles THSD7A plays in MN and its clinical implications as diagnostic, prognostic, and therapeutic response as well as Methods for detecting serum THSD7A antibodies.

Low risk of hepatitis B virus reactivation in membranous nephropathy patients with resolved infection undergoing rituximab-based regimens without antiviral prophylaxis

INTRODUCTION

Patients with resolved hepatitis B virus infection undergoing rituximab are at risk of hepatitis B virus reactivation without antiviral prophylaxis. However, the risk in such patients treated with rituximab-based regimens for membranous nephropathy is not clear. We evaluated the risk of hepatitis B virus reactivation in membranous nephropathy patients with resolved infection undergoing rituximab-based regimens without antiviral prophylaxis.

METHODS

Clinical data of 51 membranous nephropathy patients with resolved hepatitis B virus infection undergoing rituximab-based regimens without antiviral prophylaxis were retrospectively analyzed. Among these, 21 patients were followed for more than 1 year after rituximab discontinuation. The clinical data collected aimed to assess patients' responses and the risk of hepatitis B virus reactivation during and after rituximab treatment.

RESULTS

30/51 (58.8 %) patients reached complete or partial remission at 12 months. None of the patients experienced HBsAg seroreversion during rituximab treatment. Alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transpeptidase and total bilirubin levels, as well as the numbers of patients who exceeded the upper limits of normal for alkaline phosphatase and prothrombin time, did not show any statistically significant difference during rituximab-based therapy. Neither did the anti-HBs level, the number of patients with protective anti-HBs titers exceeding 10 U/L, nor the levels of CD19+ B cells, CD4+ T cells, CD8+ T cells, and natural killer cells. Among the 21 patients followed for 12 (ranging from 12 to 19) months after rituximab discontinuation, no hepatitis B virus reactivation was observed. The mean anti-HBs level and the number of patients with anti-HBs titers over 10 U/L did not show any statistically significant difference during the extended follow-up of 33 patient-years. Neither did the CD4+ T cell, CD8+ T cell, nor the natural killer cell counts. One patient presented with an ALT level that exceeded the baseline value by three times and reached above 100 U/L, accompanied by elevations in AST, GGT, and ALP levels. Meanwhile, the anti-HBs titer was 816.09 U/L, and HBsAg was negative.

CONCLUSION

The administration of rituximab-based regimens in membranous nephropathy patients with hepatitis B virus resolved infection leads to a low risk of hepatitis B virus reactivation without antiviral prophylaxis. Patient's immune status, drug combination, rituximab strategy should be fully evaluated when considering antiviral prophylaxis therapy.

Mannose-Binding Lectin Deposition in Membranous Nephropathy and Differentiation of Primary from Secondary Forms

The differentiation between primary and secondary forms of membranous nephropathy (MN) is a cornerstone that is necessary for adequate decision making regarding the treatment options and behavior of each specific case. Kidney biopsy and antibody results can be controversial, and a unique biomarker has still not been found.

BACKGROUND AND OBJECTIVES

We investigated the lack of mannose-binding lectin (MBL) deposition in patients with secondary MNs (sMNs) with the presence of IgG4 deposition in relation to the presence of MBL deposition in patients with primary MNs (pMNs). We also established a connection between the stage of MN and MBL deposition.

MATERIALS AND METHODS

Materials from 72 renal biopsies with proven MN were used for immunohistochemistry staining (IHC) for the phospholipase A2 receptor (PLA2R), immunoglobulin subtype IgG4, and MBL. Patients were separated into one of the following three groups: primary MN (pMN), idiopathic MN (iMN), and secondary MN (sMN). Serum antibodies for PLA2R and thrombospondin type-I-domain-containing 7A (THSD7A) were also used for the precise evaluation of the type of MN, as well as for detecting positivity for PLA2R using IHC. Which stage of MN was present in relation to the deposition of MBL was evaluated.

RESULTS

In total, 50 patients were positive for IgG4, 34 with pMN, 12 with iMN, and 4 with sMN. A total of 20 patients were positive for MBL, 14 with pMN and 6 with iMN; no MBL deposits were found in patients with sMN. MBL positivity was predominantly present in the first two stages of MN, with a gradual reduction in the later stages.

CONCLUSIONS

The activation of the lectin-complement pathway occurs in the early stages of the disease and is associated with the deposition of IgG4; IgG4 deposition is present in sMN, but there is no MBL deposition. IgG4 cannot be used for the differentiation of primary from secondary MNs, but the lack of MBL can be used as a marker for sMN in the early stages of the disease.

Systematic Review of Kidney Injury Biomarkers for the Evaluation of CKD of Uncertain Etiology

Introduction

Chronic kidney disease of uncertain etiology (CKDu) is an incompletely defined phenotype of chronic kidney disease (CKD) affecting young individuals mostly in agricultural communities in Central America and South Asia. CKDu is a diagnosis of exclusion made in individuals from endemic regions.

Methods

We conducted a systematic review of the primary literature on urinary and plasma kidney injury biomarkers measured in the setting of CKDu (through February 2023). The literature was identified via a Web of Science search and hand search of the references of previously identified literature. Search terms included "CKDu," "Mesoamerican Nephropathy," "CKD of unknown etiology," "Chronic Interstitial Nephritis in Agricultural Communities," "biomarker," "urin∗," and/or "plasma."

Results

A total of 25 papers were included. The 2 most frequently measured biomarkers were urinary kidney injury molecule-1 (KIM-1) and urinary neutrophil gelatinase-associated lipocalin (NGAL). There was substantial variability in study design, laboratory assay methods, and statistical methodology, which prohibited meta-analysis.

Conclusion

Biomarkers that identify tubulointerstitial disease early and accurately may substantially accelerate progress in the study of CKDu and facilitate public health approaches that eventually lead to its prevention and elimination. To date, the literature is limited by relatively small sample sizes and methodological limitations which should be addressed in future studies.

The Association of Lower Levels of Baseline Proteinuria With Earlier Remission in Primary Membranous Nephropathy

Aim To study the clinical profile and course and to assess the outcome of patients with biopsy-proven primary membranous nephropathy (MN). Methods This study was carried out in a tertiary care hospital between December 2017 and December 2021 on four-year retrospective biopsy-proven patients with membranous nephropathy (MN). Urinary proteins, serum albumin, and serum creatinine were the baseline investigations that were performed. Special tests were done whenever necessary. Patients were treated with a modified Ponticelli (MP) regimen whenever needed. Patients were followed up after treatment administration for a minimum of a year. Results The study was done in 48 biopsy-proven MN patients. Thirty-six patients had primary MN with a mean age of 47+/-11.7 years. The male-female ratio was 2.6:1. Hypertension was present in 39% (14 patients), microscopic hematuria in 28% (10 patients), and acute kidney injury in 22% (8 patients). The mean 24-hour urinary protein was 11.2+/-2.9 g/day. PLA2R was positive in 78% (28 patients) of primary MN patients. Spontaneous remission was noted in 13.8% (5 patients) who were treated conservatively. Spontaneous remission was associated with lower baseline proteinuria (p<0.001), higher baseline serum albumin (p<0.001), and PLA2R negativity (p=0.04). Complete or partial treatment response was noted in 74.2% (23 patients). Treatment remission was associated with lower baseline proteinuria (p=0.018). Secondary membranous nephropathy (secondary MN) was diagnosed in 12 patients. Eleven were class V lupus nephritis, all women, and one male person living with HIV/AIDS (PLHA). Conclusions The majority of our primary MN patients were PLA2R positive on renal biopsy. Statistically significant factors associated with spontaneous remission were lower proteinuria, higher serum albumin at baseline, and PLA2R negativity. Treatment response was associated with lower proteinuria at presentation. The most common cause of secondary MN was lupus nephritis.

Stroke associated with primary membranous nephropathy in a young adult: Case report

INTRODUCTION

Stroke in young individuals is becoming increasingly prevalent worldwide. Its causes can vary widely, so a thorough investigation by a multidisciplinary team is needed. Pinpointing the precise underlying pathology responsible for the stroke yields benefits for patients, particularly in recurrent events.

CASE PRESENTATION

A 38-year-old man presented to the emergency department with symptoms suggestive of stroke, including right hemiparesis, dysarthria, ataxic gait, and right central facial palsy. The brain magnetic resonance image revealed an ischemic lesion located in the left basal ganglia and near the corona radiata. Following an extensive workup, a diagnosis of nephrotic was reached. Histopathology and the exclusion of secondary causes confirmed primary membranous nephropathy as the underlying condition. The patient underwent treatment tailored to address the specific glomerulopathy, along with anticoagulation therapy and immunosuppression as per current guidelines. Subsequent assessments showed stabilization of renal function, resolution of the edema, and the absence of new thromboembolic events during follow-up.

CONCLUSION

The nephrotic syndrome should be recognized as a potential underlying cause of stroke in young patients and, therefore, it should be included in the differential diagnosis during the evaluation of patients with coagulopathies. Nephrotic syndrome screening may be done by conducting a simple urinalysis readily available in most healthcare facilities. This underlines the importance of considering renal pathology in the assessment of stroke etiologies, especially when coagulation abnormalities are present.

Significance of the total renal chronicity score in predicting renal outcome in PLA2R-associated membranous nephropathy

BACKGROUND

Phospholipase A2 receptor (PLA2R)-associated membranous nephropathy accounts for the majority of membranous nephropathy; however, few studies have determined the prognostic impact and clinical application of renal pathologic change on this disease.

METHODS

A retrospective cohort study of 262 patients with PLA2R-associated membranous nephropathy was conducted. The total renal chronicity score calculated according to the degree of glomerulosclerosis, interstitial fibrosis, tubular atrophy, and arteriosclerosis was applied to evaluate renal chronicity. Baseline bias was adjusted by inverse probability weight when assessing the prognostic impact of chronicity, and multiple parameters were used to evaluate the application value of renal chronicity.

RESULTS

During a median follow-up of 24.5 months, renal outcome (kidney function deterioration and/or end-stage kidney disease) was observed in 22 (8.40%) patients. Not only did a higher total renal chronicity score independently predict renal outcome [odds ratio (OR): 1.562, 95% confidence interval (CI) 1.073-2.273, P = 0.020], but non-minimal chronicity was also an independent risk factor for renal outcome (OR: 3.170, 95% CI 1.040-9.659, P = 0.042). Moreover, the membranous nephropathy risk classification in the Kidney Disease: Improving Global Outcomes (KDIGO) guideline integrated with non-minimal chronicity showed improvements in categorical net reclassification (0.174, 95% CI 0.012-0.335, P = 0.035), continuous net reclassification (0.462, 95% CI 0.087-0.838, P = 0.016), and integrated discrimination (0.019, 95% CI 0.003-0.035, P = 0.020) compared to the original classification.

CONCLUSIONS

Renal chronicity is closely associated with renal outcomes in PLA2R-associated membranous nephropathy, and combining the KDIGO risk classification with chronicity scores may provide a more accurate prognostic prediction.

Comparison of the efficacy of steroid-free versus classic steroid-containing regimens in primary membranous nephropathy

Objective: To compare the efficacy of a steroid-free regimen with steroid-based treatment in managing primary membranous nephropathy (PMN) and investigate the potential benefits of steroid-free regimens in PMN therapy. Methods: This was a single-centre prospective cohort study. A total of 81 patients were divided into two groups according to their medication regimen: a rituximab (RTX)/tacrolimus (TAC) group (low-dose RTX combined with low-dose TAC group, without steroids, n = 31) and a prednisone (P)/TAC group (P combined with TAC group, n = 61). The changes in 24-h urine protein quantification, levels of blood albumin, blood creatinine, total cholesterol, triglyceride and fasting blood glucose as well as anti-phospholipase A2 receptor antibody titres were observed in both groups before treatment and after 1, 3, 6 and 12 months of treatment. Clinical remission (complete and partial remission), serological remission and recurrence were assessed in both groups after treatment, and the occurrence of adverse reactions was observed. Results: 1) Before treatment, there was no significant difference in baseline values between the two groups (p > 0.05). 2) After 12 months of treatment, the 24-h proteinuria and total cholesterol levels in the RTX/TAC group were significantly lower than those in the P/TAC group (p < 0.05). 3) After 6 months of treatment, the clinical remission rate of the RTX/TAC group was significantly higher than that of the P/TAC group (p < 0.05). After 12 months of treatment, the clinical remission rate of the RTX/TAC group was significantly higher than that of the P/TAC group (p < 0.05). (4) After 3, 6 and 12 months of treatment, serological remission rates in the RTX/TAC group were significantly higher than those in the P/TAC group (p < 0.05). During treatment, the anti-PLA2R antibody titres in the RTX/TAC group remained lower than those in the P/TAC group (p < 0.05). Conclusion: The low-dose RTX combined with low-dose TAC steroid-free regimen induces serological remission in patients with PMN earlier than the classic regimen of P combined with TAC, and there was no significant difference in adverse effects between the two groups. Besides, the long-term clinical remission effect of low-dose RTX combined with low-dose TAC is better than that of P combined with TAC.

Salivary microbiome in kidney diseases: A narrative review

Many research has been conducted since the microbiota's discovery that have focused on the role it plays in health and disease. Microbiota can be divided into categories like intestinal, oral, respiratory, and skin microbiota based on the specific localized areas. To maintain homeostasis and control immunological response, the microbial populations live in symbiosis with the host. On the other hand, dysbiosis of the microbiota can cause diseases including kidney diseases and the deregulation of body functioning. We discuss the current understanding of how various kidney diseases are caused by the salivary microbiome (SM) in this overview. First, we review the studies on the salivary microbiota in diverse clinical situations. The importance of the SM in diabetic kidney disease, chronic kidney disease, membranous nephropathy, and IgA nephropathy is next highlighted. We conclude that the characteristics of the SM of patients with various kidney diseases have revealed the potential of salivary microbial markers as noninvasive tool for the detection of various kidney diseases.

The Clinical Profile and Long-Term Outcome of Children with Membranous Nephropathy, and the Evaluation of Anti-Phospholipase A2 Receptor Antibody Immunohistochemistry in Kidney Biopsy

Introduction

Idiopathic membranous nephropathy (iMN) is a rare cause of nephrotic syndrome in children (1%-7%). Anti-phospholipase A2 receptor (PLA2R) antibody positivity in kidney biopsy is observed in 52%-78% of adults and 45% of children with iMN. The objectives of the study are to analyze the clinical profile and outcome of membranous nephropathy in children, to assess the prevalence of anti-PLA2R immunohistochemistry (IHC) in kidney biopsy, and to correlate their presence with disease characteristics.

Methods

We are reporting a single-center retrospective study conducted in pediatric nephrology division. Clinical data and outcome parameters of children with membranous nephropathy were analyzed. PLA2R IHC was performed in kidney biopsy specimens retrospectively.

Results

We analyzed 43 children with membranous nephropathy (MN) from a single center. 18 (42%) had idiopathic MN (iMN). PLA2R IHC was performed in kidney biopsy specimens in 14/18 (78%) patients with iMN and 7/9 (78%) non-lupus secondary membranous nephropathy (SMN) patients. The most common cause of SMN was lupus nephritis in 16 patients (64%). The mean estimated glomerular filtration rate (eGFR) at onset was 156 ± 81 ml/min/1.73m2. The sensitivity and specificity of PLA2R IHC in diagnosing pediatric MN was 50% and 57%, respectively; positive and negative predictive values were 70% and 36%, respectively. At the final follow-up, chronic kidney disease stage 5 (CKD 5) developed in 2/14 (14.3%) iMN patients.

Conclusions

IHC PLA2R staining of glomerular tissue is a useful diagnostic marker of IMN. Though PLA2R prevalence is lower in children, its role in guiding treatment needs further exploration.

Identification of biomarkers related to immune and inflammation in membranous nephropathy: comprehensive bioinformatic analysis and validation

Background

Membranous nephropathy (MN) is an autoimmune glomerular disease that is predominantly mediated by immune complex deposition and complement activation. The aim of this study was to identify key biomarkers of MN and investigate their association with immune-related mechanisms, inflammatory cytokines, chemokines and chemokine receptors (CCRs).

Methods

MN cohort microarray expression data were downloaded from the GEO database. Differentially expressed genes (DEGs) in MN were identified, and hub genes were determined using a protein-protein interaction (PPI) network. The relationships between immune-related hub genes, immune cells, CCRs, and inflammatory cytokines were examined using immune infiltration analysis, gene set enrichment analysis (GSEA), and weighted gene co-expression network analysis (WGCNA). Finally, the immune-related hub genes in MN were validated using ELISA.

Results

In total, 501 DEGs were identified. Enrichment analysis revealed the involvement of immune- and cytokine-related pathways in MN progression. Using WGCNA and immune infiltration analysis, 2 immune-related hub genes (CYBB and CSF1R) were identified. These genes exhibited significant correlations with a wide range of immune cells and were found to participate in B cell/T cell receptor and chemokine signaling pathways. In addition, the expressions of 2 immune-related hub genes were positively correlated with the expression of CCR1, CX3CR1, IL1B, CCL4, TNF, and CCR2.

Conclusion

Our study identified CSF1 and CYBB as immune-related hub genes that potentially influence the expression of CCRs and pro-inflammatory cytokines (CCR1, CX3CR1, IL1B, CCL4, TNF, and CCR2). CSF1 and CYBB may be potential biomarkers for MN progression, providing a perspective for diagnostic and immunotherapeutic targets of MN.

Development and External Validation of a Nomogram for Predicting the Effect of RTX on the Treatment of Membranous Nephropathy

Introduction

Rituximab (RTX) has been shown to be effective in inducing immunological remission in patients with membranous nephropathy (MN). Some patients required more than one course of RTX to achieve immunological remission. Identifying patients who need more courses of RTX to achieve immunological remission is beneficial for better physician-patient communication, the assessment of treatment course, and the evaluation of medical costs. This study aims to establish a practical model to predict the probability of immunological remission after receiving one cycle of RTX.

Methods

This study enrolled 106 patients from the First Affiliated Hospital of Zhengzhou University in the modeling group and 30 patients from Henan Provincial Hospital of Traditional Chinese Medicine in the external validation group. Patients in the modeling group were divided into responders or nonresponders according to whether they achieved immunological remission or not after following up for 6 months. A nomogram was established based on the results of logistic regression analysis. The predictive performance of the nomogram was evaluated by the area under the receiver operating characteristic curve (AUC), calibration curves, and decision curve analysis (DCAs).

Results

In the modeling group, 75 (70.8%) patients achieved immunological remission within 6 months after receiving one cycle of RTX. Significant differences were observed between nonresponders and responders. Risk factors used in nomogram included PLA2R antibody, hemoglobin, and gender. The AUC value of nomogram was 0.797 (95% CI 0.701-0.894, P<0.001). The calibration curves demonstrated acceptable agreement between the predicted outcomes by the nomogram and the actual values. DCA curves showed good positive net benefits in the predictive model. The external validation also demonstrated the reliability of the prediction nomogram.

Conclusion

A predictive nomogram including PLA2R antibody, hemoglobin, and gender may provide a basis to predict the doses of RTX needed in MN patients.

Prognostic prediction of idiopathic membranous nephropathy using interpretable machine learning

BACKGROUND

Established prognostic models of idiopathic membranous nephropathy (IMN) were limited to traditional modeling methods and did not comprehensively consider clinical and pathological patient data. Based on the electronic medical record (EMR) system, machine learning (ML) was used to construct a risk prediction model for the prognosis of IMN.

METHODS

Data from 418 patients with IMN were diagnosed by renal biopsy at the Fifth Clinical Medical College of Shanxi Medical University. Fifty-nine medical features of the patients could be obtained from EMR, and prediction models were established based on five ML algorithms. The area under the curve, recall rate, accuracy, and F1 were used to evaluate and compare the performances of the models. Shapley additive explanation (SHAP) was used to explain the results of the best-performing model.

RESULTS

One hundred and seventeen patients (28.0%) with IMN experienced adverse events, 28 of them had compound outcomes (ESRD or double serum creatinine (SCr)), and 89 had relapsed. The gradient boosting machine (LightGBM) model had the best performance, with the highest AUC (0.892 ± 0.052, 95% CI 0.840-0.945), accuracy (0.909 ± 0.016), recall (0.741 ± 0.092), precision (0.906 ± 0.027), and F1 (0.905 ± 0.020). Recursive feature elimination with random forest and SHAP plots based on LightGBM showed that anti-phospholipase A2 receptor (anti-PLA2R), immunohistochemical immunoglobulin G4 (IHC IgG4), D-dimer (D-DIMER), triglyceride (TG), serum albumin (ALB), aspartate transaminase (AST), β2-microglobulin (BMG), SCr, and fasting plasma glucose (FPG) were important risk factors for the prognosis of IMN. Increased risk of adverse events in IMN patients was correlated with high anti-PLA2R and low IHC IgG4.

CONCLUSIONS

This study established a risk prediction model for the prognosis of IMN using ML based on clinical and pathological patient data. The LightGBM model may become a tool for personalized management of IMN patients.

Present and Future of IgA Nephropathy and Membranous Nephropathy Immune Monitoring: Insights from Molecular Studies

IgA Nephropathy (IgAN) and Membranous Nephropathy (MN) are primary immune-mediated glomerular diseases with highly variable prognosis. Current guidelines recommend that greater immunologic activity and worse prognosis should guide towards the best treatment in an individualized approach. Nevertheless, proteinuria and glomerular filtration rate, the current gold standards for prognosis assessment and treatment guidance in primary glomerular diseases, may be altered with chronic damage and nephron scarring, conditions that are not related to immune activity. In recent years, thanks to the development of new molecular technologies, among them genome-wide genotyping, RNA sequencing techniques, and mass spectrometry, we have witnessed an outstanding improvement in understanding the pathogenesis of IgAN and MN. In addition, recent genome-wide association studies have suggested potential targets for immunomodulating agents, stressing the need for the identification of specific biomarkers of immune activity. In this work, we aim to review current evidence and recent progress, including the more recent use of omics techniques, in the identification of potential biomarkers for immune monitoring in IgAN and MN.

[Diagnosis and therapy of membranous nephropathy-2023]

Membranous nephropathy (MN) is an immune-complex glomerulonephritis and is one of the most common causes of nephrotic syndrome in adults and is also one of the autoimmune kidney diseases with the highest rate of spontaneous remission. The most common autoantigen (> 70% of cases) is directed against the phospholipase A2 receptor (PLA2-R) and, with its detection and clinical course, allows for excellent diagnostics as well as optimal therapy monitoring. Other autoantigens are constantly being published and will enable an autoantigen-based diagnostic and therapeutic algorithm for MN in the future. In the absence of spontaneous remission, a specific B‑cell-directed therapy, especially with rituximab, is the initial therapy of choice. Calcineurininhibitors or cyclophosphamide should only be used if they are carefully indicated in the respective clinical context and if there are serious clinical consequences both from the nephrotic syndrome and from loss of kidney function. Since immune complexes within the kidney often require a long time to be degraded, proteinuria response can follow the immunological remission after many months. The therapy of MN represents the favorable case of a precision medicine-based therapy in nephrology, whereby new therapeutic B‑cell antibodies for the rare but difficult forms of MN will find their way into clinical routine in the not-too-distant future.

Pathogenicity of Human Anti-PLA 2 R1 Antibodies in Minipigs: A Pilot Study

SIGNIFICANCE STATEMENT

Membranous nephropathy (MN) is an autoimmune kidney disease characterized by immune deposits in the glomerular basement membrane. Circulating anti-phospholipase A 2 receptor 1 (PLA 2 R1) antibodies are detectable in 70%-80% of patients with MN, but experimental evidence of pathogenicity has been lacking. This study demonstrates the pathogenicity of human anti-PLA 2 R1 antibodies in minipigs, a model for MN that intrinsically expresses PLA 2 R1 on podocytes. After passive transfer of human anti-PLA 2 R1 antibody-containing plasma from patients with PLA 2 R1-associated MN to minipigs, antibodies were detected in the minipig glomeruli, but not in response to plasma from healthy controls. The minipigs developed histomorphological characteristics of MN, local complement activation in the glomeruli, and low-level proteinuria within 7 days, showing that human anti-PLA 2 R1 antibodies are pathogenic.

BACKGROUND

Primary membranous nephropathy (MN) is an autoimmune kidney disease in which immune complexes are deposited beneath the epithelium in the glomeruli. The condition introduces a high risk for end-stage kidney disease. Seventy percent to 80% of patients with MN have circulating antibodies against phospholipase A 2 receptor 1 (PLA 2 R1), and levels correlate with treatment response and prognosis. However, experimental evidence that human anti-PLA 2 R1 antibodies induce MN has been elusive.

METHODS

In passive transfer experiments, minipigs received plasma or purified IgG from patients with PLA 2 R1-associated MN or from healthy controls. Anti-PLA 2 R1 antibodies and proteinuria were monitored using Western blot, ELISA, and Coomassie staining. Kidney tissues were analyzed using immunohistochemistry, immunofluorescence, electron microscopy, and proteomic analyses.

RESULTS

Minipigs, like humans, express PLA 2 R1 on podocytes. Human anti-PLA 2 R1 antibodies bound to minipig PLA 2 R1 in vitro and in vivo . Passive transfer of human anti-PLA 2 R1 antibodies from patients with PLA 2 R1-associated MN to minipigs led to histological characteristics of human early-stage MN, activation of components of the complement cascade, and low levels of proteinuria. We observed development of an autologous, later phase of disease.

CONCLUSIONS

A translational approach from humans to minipigs showed that human anti-PLA 2 R1 antibodies are pathogenic in MN, although in the heterologous phase of disease only low-level proteinuria developed.

A Genetic Risk Score Distinguishes Different Types of Autoantibody-Mediated Membranous Nephropathy

Introduction

Membranous nephropathy (MN) is the leading cause of nephrotic syndrome in adults and is characterized by detectable autoantibodies against glomerular antigens, most commonly phospholipase A2 receptor 1 (PLA2R1) and thrombospondin type-1 domain containing 7A (THSD7A). In Europeans, genetic variation in at least five loci, PLA2R1, HLA-DRB1, HLA-DQA1, IRF4, and NFKB1, affects the risk of disease. Here, we investigated the genetic risk differences between different autoantibody states.

Methods

1,409 MN individuals were genotyped genome-wide with a dense SNV array. The genetic risk score (GRS) was calculated utilizing the previously identified European MN loci, and results were compared with 4,929 healthy controls and 422 individuals with steroid-sensitive nephrotic syndrome.

Results

GRS was calculated in the 759 MN individuals in whom antibody status was known. The GRS for MN was elevated in the anti-PLA2R1 antibody-positive (N = 372) compared with both the unaffected control (N = 4,929) and anti-THSD7A-positive (N = 31) groups (p < 0.0001 for both comparisons), suggesting that this GRS reflects anti-PLA2R1 MN. Among PLA2R1-positive patients, GRS was inversely correlated with age of disease onset (p = 0.009). Further, the GRS in the dual antibody-negative group (N = 355) was intermediate between controls and the PLA2R1-positive group (p < 0.0001).

Conclusion

We demonstrate that the genetic risk factors for PLA2R1- and THSD7A-antibody-associated MN are different. A higher GRS is associated with younger age of onset of disease. Further, a proportion of antibody-negative MN cases have an elevated GRS similar to PLA2R1-positive disease. This suggests that in some individuals with negative serology the disease is driven by autoimmunity against PLA2R1.

Clinical and pathologic features of primary membranous nephropathy in Turkey: a multicenter study by the Turkish Society of Nephrology Glomerular Diseases Working Group

Background

We aimed to evaluate the features of primary membranous nephropathy (MNP) in Turkish people.

Methods

This is a retrospective analysis of patients with biopsy-proven primary MNP. We obtained the data collected between 2009 and 2019 in the primary glomerulonephritis registry of the Turkish Society of Nephrology Glomerular Diseases Study Group (TSN-GOLD). Patients with a secondary cause for MNP were excluded. Clinical, demographic, laboratory, and histopathological findings were analyzed.

Results

A total of 995 patients with primary MNP were included in the analyses. Males constituted the majority (58.8%). The mean age was 48.4 ± 13.9 years. The most common presentation was the presence of nephrotic syndrome (81.7%) and sub nephrotic proteinuria (10.3%). Microscopic hematuria was detected in one-third of patients. The median estimated glomerular filtration rate (eGFR) was 100.6 mL/min/1.73 m² (IQR, 75.4–116.3), and median proteinuria was 6000 mg/d (IQR, 3656–9457). Serum C3 and C4 complement levels were decreased in 3.7 and 1.7% of patients, respectively. Twenty-four (2.4%) patients had glomerular crescents in their kidney biopsy samples. Basal membrane thickening was detected in 93.8% of cases under light microscopy. Mesangial proliferation and interstitial inflammation were evident in 32.8 and 55.9% of the patients, respectively. The most commonly detected depositions were IgG (93%), C3 complement (68.8%), and kappa and lambda immunoglobulin light chains (70%). Although renal functions were normal at presentation, vascular, interstitial, and glomerular findings were more prominent on biopsy in hypertensive patients. No significant effect of BMI on biopsy findings was observed.

Conclusions

Despite some atypical findings, the main features of primary MNP in Turkey were similar to the published literature. This is the largest MNP study to date conducted in Turkish people.

Rituximab in patients with membranous nephropathy and kidney insufficiency

Introduction: Patients with membranous nephropathy and kidney insufficiency have an extremely high risk of progression to end-stage renal disease. Whether rituximab can effectively treat membranous nephropathy patients with renal dysfunction remains unknown at present. The aim of our study was to evaluate the effectiveness and safety of rituximab (RTX) in membranous nephropathy with kidney insufficiency.

Methods: We retrospectively analyzed the clinical data of 35 membranous nephropathy patients with kidney insufficiency administered in the First Affiliated Hospital of Zhengzhou University between January 2020 and December 2021. Patients were followed every 1–3 months for a total of 6 months. Clinical data were collected including anti-phospholipase A2 receptor antibody (anti-PLA2R antibody) quantification, 24-h urinary protein, serum albumin, and serum creatinine. The percentage of patients who achieved clinical remission was measured.

Results: There were 7 (20%) patients who achieved complete or partial response at 6 months after RTX treatment. After 6 months of treatment, patients were clinically improved as evidenced by significant improvements in anti- PLA2R antibody titer [7.70 (5.72, 16.72) vs. 59.20 (17.70, 187.50) RU/ml, p < 0.001], 24-h urine protein [7.04 (4.43, 8.90) vs. 10.15 (4.83, 13.57) g/d, p < 0.001], serum albumin [30.55 (24.97, 33.27) vs. 21.40 (16.75, 25.00)g/L, p < 0.001], serum creatinine [99.50 (75.25, 140.25) vs. 152.00 (134.50, 232.50) µmol/L, p = 0.022], and estimated glomerular filtration rate (eGFR) [78.29 (50.15, 101.55) vs. 41.12 (26.53, 51.41) ml/min/1.73 m², p = 0.045]. There were no significantly differences between responders and nonresponders in the baseline levels of anti-PLA2R antibodies, proteinuria, serum albumin, and renal function. After the RTX treatment, anti-PLA2R antibodies turned negative in all responders, but the antibody level persisted maintained positive in all but 5 nonresponders. The patients who achieved response maintained a stable kidney function during the study period, with eGFR 29.03 (28.76, 35.07) ml/min/1.73 m² before rituximab treatment and 62.73 (62.34, 63.13) ml/min/1.73 m² at the end of follow-up (p = 0.053).

Conclusion: RTX therapy might be an alternative treatment in reducing proteinuria and maintaining stable renal function among membranous nephropathy patients even with kidney insufficiency.

Comprehensively characterizing cellular changes and the expression of THSD7A and PLA2R1 under multiple in vitro models of podocyte injury

The unique morphology and gene expression of podocytes are critical for kidney function, and their abnormalities lead to nephropathies such as diabetic nephropathy and membranous nephropathy. Podocytes cultured in vitro are valuable tools to dissect the molecular mechanism of podocyte injury relative to nephropathy, however, these models have never been comprehensively compared. Here, we comprehensively compared the morphology, cytoskeleton, cell adhesion, cell spreading, cell migration, and lipid metabolism under five commonly used in vitro models including lipopolysaccharide (LPS), puromycin aminonucleoside (PAN), doxorubicin (Dox), high glucose, and glucose deprivation. Our results indicate that all stimulations significantly downregulate the expression of synaptopodin both in human and mouse podocytes. All stimulations affect podocyte morphology but show different intensity and phenotypes. In general, the five stimulations reduce cell adhesion, cell spreading, and cell migration, but the effect in human and mouse podocytes is slightly different. Human podocytes show high expression of genes enriched in the pentose phosphate pathway. Dox and PAN treatment show a strong effect on gene expression in lipid metabolism, while the other three stimulations show minimal effect. The expression of phospholipase A2 receptor (PLA2R1) and type-1 domain-containing protein 7 A (THSD7A) show opposite trends in given cells. Stimulations can dramatically affect the expression of PLA2R1 and THSD7A. Inhibition of super-enhancers reduces PLA2R1 and THSD7A expression, but ERK inhibition enhances their expression. Our results demonstrate distinctive responses in five commonly used in vitro podocyte injury models and the dynamic expression of PLA2R1 and THSD7A, which supply novel information to select suitable podocyte injury models.

Clinical Evaluation of Antiphospholipase A2 Receptor IgG4 level and Its IgG4-to-IgG Ratio Based on Quantitative Immunoassays in Idiopathic Membranous Nephropathy

Background. Phospholipase A2 receptor (PLA2R), located at the membrane of glomerular podocyte, is the major autoantigen of idiopathic membranous nephropathy (IMN), and its antibodies with a predominant IgG4 subclass lead to pathological lesions. Further studies could be performed to validate the clinical values of PLA2R-IgG, PLA2R-IgG4, and PLA2R-IgG4-to-IgG ratios, as ultrasensitive and quantitative immunoassays for PLA2R antibodies have been well established in our previous work. Methods. A cohort of 58 IMN patients, 30 of whom were followed from 3 to 42 months, was assessed for serum PLA2R-IgG and -IgG4 levels, and the ratio of PLA2R-IgG4/-IgG combined with relative clinicopathological indicators. Results. Serum PLA2R-IgG4 level was significantly correlated with glomerular PLA2R staining. In addition, it was strongly correlated with PLA2R-IgG and its ratio. PLA2R-IgG and -IgG4 levels were both correlated with high-density lipoprotein and erythrocyte sedimentation rates. The ratio at the first diagnosis can predict the remission, and its efficacy overmatched PLA2R-IgG4. In the survival curves, negative results for the ratio or PLA2R-IgG4 at the first diagnosis demonstrated higher remission rates. Conclusion. Serum PLA2R-IgG4 concentration may replace renal PLA2R immunohistochemistry in IMN diagnosis. We propose that the PLA2R-IgG4-to-IgG ratio and PLA2R-IgG4 could be novel indicators for remission prediction in clinical practice.

Analysis of glomerular PLA2R efficacy in evaluating the prognosis of idiopathic membranous nephropathy in the background of different serum anti-PLA2R levels

OBJECTIVE

To verify glomerular PLA2R antigen and serum PLA2R antibody expression in membranous nephropathy as well as to explore glomerular PLA2R efficacy in evaluating the prognosis of idiopathic membranous nephropathy (IMN) in the background of different serum anti-PLA2R levels.

METHODS

We retrospectively analyzed 155 patients who were diagnosed with IMN by kidney biopsy. Patients were divided into six groups according to their serum PLA2R antibody or glomerular PLA2R antigen positiveness and the level of serum anti-PLA2R titer. Both clinical features and pathological characteristics were recorded, and the remission time was compared among groups. Correlation between clinical figures and the anti-PLA2R titer or semi-quantity of glomerular PLA2R antigen was detected.

RESULTS

A positive correlation between time to partial remission and serum anti-PLA2R titer was found. Among patients with serum anti-PLA2R titer <150 RU/ml, there were shorter remission time in negative glomerular PLA2R antigen group compared with positive glomerular PLA2R antigen, and a positive correlation between time to complete remission and semi-quantity of glomerular PLA2R antigen was found.

CONCLUSION

Both glomerular PLA2R antigen and serum anti-PLA2R play a role in disease presentation and prognosis in primary membranous nephropathy. Glomerular PLA2R antigen has a major role on disease prognosis when serum anti-PLA2R titer is less than 150RU/ml, while serum anti-PLA2R has predominant role in IMN prognosis when serum anti-PLA2R titer is above 150RU/ml.

Novel Biomarkers in Membranous Nephropathy

Membranous nephropathy (MN) is the main cause of adult nephrotic syndrome (NS). The pathogenesis of MN is complex and involves subepithelial immune complex deposition. Approximately one-third of patients with MN develop end-stage renal disease (ESRD). Timely diagnosis and reasonable intervention are the keys to improving prognosis. In recent years, with the development of high-throughput technologies, such as mass spectrometry (MS), microarray, and sequencing technologies, the discovery of biomarkers for MN has become an important area of research. In this review, we summarize the significant progress in biomarker identification. For example, a variety of podocyte target antigens and their autoantibodies have been reported. Phospholipase A2 receptor (PLA2R) is the most well-established target antigen in MN. PLA2R and its autoantibodies have clinical significance, with both diagnostic and therapeutic value for MN. In addition, a variety of new biomarkers, including proteins, metabolites, noncoding RNAs (ncRNAs), and immune cells, have recently been found. These MN-related biomarkers have great significance in the diagnosis, progression, prognosis, and treatment response of MN.

The Canadian Glomerulonephritis Registry (CGNR) and Translational Research Initiative: Rationale and Clinical Research Protocol

Background

Glomerulonephritis (GN) is a leading cause of kidney failure and accounts for 20% of incident cases of end-stage kidney disease (ESKD) in Canada annually. Reversal of kidney injury and prevention of progression to kidney failure is possible; however, limited knowledge of underlying disease mechanisms and lack of noninvasive biomarkers and therapeutic targets are major barriers to successful therapeutic intervention. Multicenter approaches that link longitudinal clinical and outcomes data with serial biologic specimen collection would help bridge this gap.

Objective

To establish a national, patient-centered, multidimensional web-based clinical database and federated virtual biobank to conduct human-based molecular and clinical research in GN in Canada.

Design

Multicenter, prospective observational registry, starting in 2019.

Setting

Nine participating Canadian tertiary care centers.

Patients

Adult patients with a histopathologic pattern of injury consistent with IgA nephropathy, focal and segmental glomerulosclerosis, minimal change disease, membranous nephropathy, C3 glomerulopathy, and membranoproliferative GN recruited within 24 months of biopsy.

Measurements

Initial visits include detailed clinical, histopathological, and laboratory data collection, blood, urine, and tonsil swab biospecimen collection, and a self-administered quality of life questionnaire. Follow-up clinical and laboratory data collection, biospecimen collection, and questionnaires are obtained every 6 months thereafter.

Methods

Patients receive care as defined by their physician, with study visits scheduled every 6 months. Patients are followed until death, dialysis, transplantation, or withdrawal from the study. Key outcomes include a composite of ESKD or a 40% decline in estimated glomerular filtration rate (eGFR) at 2 years, rate of kidney function decline, and remission of proteinuria. Clinical and molecular phenotypical data will be analyzed by GN subtype to identify disease predictors and discover therapeutic targets.

Limitations

Given the relative rarity of individual glomerular diseases, one of the major challenges is patient recruitment. Initial registry studies may be underpowered to detect small differences in clinically meaningful outcomes such as ESKD or death due to small sample sizes and short duration of follow-up in the initial 2-year phase of the study.

Conclusions

The Canadian Glomerulonephritis Registry (CGNR) supports national collaborative efforts to study glomerular disease patients and their outcomes.

Trial registration

NCT03460054.

Salivary microbiota analysis of patients with membranous nephropathy

The oral microbiota are closely related to human health. Nonetheless, to the best of our knowledge, their relationship with membranous nephropathy (MN) remains unstudied. The saliva microbiota collected from 22 patients with MN and 15 healthy controls were analyzed by next-generation sequencing, and bioinformatics analysis of the 16S ribosomal RNA gene was subsequently carried out. The Chao1 and Shannon indices in patients with MN were higher than those in healthy controls. Analysis of similarities revealed that the oral microbiota in the patient group were significantly different from those in the healthy controls. At the genus level, the abundance of Alloprevotella, Granulicatella, Prevotella, Streptococcus and Prevotella_7 was markedly higher in patients with MN than in healthy controls. Six operational taxonomic units (OTUs; OTU5, OTU28, OTU9, OTU15, OTU33 and OTU38) were found to be markedly correlated with the clinical factors creatinine, proteinuria in 24 h, estimated glomerular filtration rate and systolic blood pressure. A total of 28 Kyoto Encyclopedia of Genes and Genomes pathways were obtained from the significant OTUs. The oral microbiota of patients with MN were investigated and it was found that OTU5, OTU28, OTU9, OTU15, OTU33 and OTU38 may be used as biomarkers. The present findings may assist in the diagnosis of patients with MN.

Anti-phospholipase A2 receptor antibodies directly induced podocyte damage in vitro

Background

The pathogenesis of primary membranous nephropathy (MN) involves the antibodies against antigens on the cell surface of podocytes, with the majority of M-type phospholipase A2 receptor (PLA2R), and a profound podocyte dysfunction. The effects of anti-PLA2R antibodies directly to the podocytes remain unclear.

Methods

Anti-PLA2R antibodies from patients with PLA2R-associated MN were affinity-purified using a column coupled with recombinant human PLA2R protein. Their effects on conditionally immortalized human podocytes were assessed by apoptosis assays, cellular calcium detection, wound healing assay, and immunofluorescent staining. Proteomics analysis was performed by LC-MS/MS and on PANTHER database.

Results

The stimulation by anti-PLA2R antibodies could induce early-stage apoptosis of podocytes (MFI of Annexin V = 104.3 ± 19.2 vs. 36.7 ± 7.6, p = 0.004). The increase of calcium concentration in podocytes (MFI = 3309.3 ± 363.6 vs. 1776.3 ± 212.7, p = 0.015) might attribute to the endoplasmic reticulum calcium efflux. The expression of calcium/calmodulin-dependent protein kinase IV (CaMK4) was also increased (MFI = 134.4 ± 9.8 vs. 105.3 ± 10.1, p = 0.011). Proteomics results suggested that anti-PLA2R antibody treatment led to damage on cellular structure, and produced functional disorders on protein binding, actin filament binding, and microtubule motor activity. The staining of F-actin on foot process was reduced (MFI = 27.3 ± 2.8 vs. 47.5 ± 1.0, p = 0.001) and the motility and adherence capacity of podocytes were reduced (number of migrated cells = 44.7 ± 3.1 vs. 53.3 ± 4.9, p = 0.001) after incubation with anti-PLA2R antibodies.

Conclusion

These data indicate that anti-PLA2R antibodies may directly induce podocyte damage independent of the complement system, which expands the mechanism of anti-PLA2R antibodies on MN.

Revisiting immunological and clinical aspects of membranous nephropathy

Idiopathic or primary membranous nephropathy (IMN) is one of the most frequent causes of nephrotic syndrome in adults and the elderly. It is characterized by a thickening of the wall of the glomerular capillaries due to the presence of immune complex deposits. 85% of membranous nephropathy cases are classified as primary or idiopathic (IMN). The rest are of secondary origin (SMN), caused by autoimmune conditions or malignant tumors as lung cancer, colon and melanomas. It is an organ-specific autoimmune disease in which the complement system plays an important role with the formation of the membrane attack complex (MAC; C5b-9), which produces an alteration of the podocyte structure. The antigen responsible for 70-80% of IMN is a podocyte protein called M-type phospholipase A2 receptor (PLA2R). More recently, another podocyte antigen has been identified, the "Thrombospondin type-1 domain-containing 7A" (THSD7A), which is responsible for 10% of the cases of negative IMN for anti- PLA2R.

Characteristics and Prognostic Value of Tertiary Lymphoid Organs in Membranous Nephropathy: A Retrospective Study

Background

Tertiary lymphoid organs play an essential role in the inflammation of the kidney. The clinical association between TLOs and membranous nephropathy (MN) is not clear yet.

Methods

Consecutive patients with the histologically confirmed membranous nephropathy in Tongji Hospital from July 19, 2012, to September 26, 2019, were included in this study. TLOs in renal biopsy tissues were detected by periodic acid–Schiff-stained and immunohistochemistry. Logistic regression was performed to evaluate the correlations of TLOs and clinical features of patients with MN. Kaplan–Meier analysis was utilized to examine the relationship between TLOs and remission of proteinuria.

Results

A total of 442 patients with MN were included in this study, of which the average age was 46.4 years old, and 58.8% were male. Moreover, 33% of patients with MN had TLOs in this study. The median value of proteinuria among patients with MN with TLOs was 4.9 g/24 h, which was much greater than no-TLOs ones (3.2 g/24 h, p < 0.001). Moreover, the patients with TLOs had higher serum creatinine and lower serum albumin. The severity of clinical features among the patients with MN aggravated with the increase in the grade of TLOs. In addition, the patients who had TLOs were more likely to be positive of anti-phospholipase A2 receptor autoantibodies. Meanwhile, the patients without TLOs showed significantly higher complete remission and total remission of proteinuria.

Conclusion

In this study, we demonstrated that TLOs were common among patients with MN. Moreover, the patients with MN with TLOs showed a worse clinical manifestation and an outcome compared with the patients without TLOs.

Establishment of Galectin-3 Time-resolved Fluoroimmunoassay and its Application in Idiopathic Membranous Nephropathy

The aim of this study was to establish a time-resolved fluorescent immunoassay (TRFIA) for the detection of serum Galectin-3 (Gal-3) and apply this method to evaluate the clinical significance of serum Gal-3 in predicting Idiopathic Membranous Nephropathy (IMN) progression. The Gal-3-TRFIA was established using the double antibody sandwich method, with the capture antibodies coated on a 96-well microplate and the detection antibodies chelated with Europium (III) (Eu³⁺). Serum Gal-3 was detected in 81 patients with IMN and 123 healthy controls to further evaluate the value of the Gal-3 in staging of IMN. The sensitivity of the Gal-3-TRFIA assay was 0.85 ng/mL, and the detection range was 0.85-1000 ng/mL. The Gal-3 intra-batch and inter-batch coefficients of variation were 3.45% and 5.12%, respectively. The correlation coefficient (R) between the Gal-3-TRFIA assay and commercially available enzyme-linked immunosorbent assay kits was 0.83. The serum Gal-3 concentration was higher in patients with IMN (65.57 ± 55.90 ng/mL) compared to healthy controls (16.29 ± 9.91 ng/mL, P < 0.0001). In this study, a wide detection range Gal-3-TRFIA assay was developed using lanthanide (Eu³⁺) chelates for the detection of Gal-3 concentrations in serum. Gal-3 concentration is elevated in patients with IMN.

Glomerular Diseases of the Kidney Allograft: Toward a Precision Medicine Approach

The continual development of potent immunosuppressive regimens has led to a decreased incidence of acute rejection and improvement of short-term kidney allograft survival. In contrast to acute rejection, glomerular diseases of the kidney allograft are being encountered more frequently and are emerging as leading causes of late kidney allograft failure. Although data on the pathogeneses of glomerular diseases in the kidney allograft are sparse, cumulative evidence suggests that post-transplant glomerular diseases may be the result of inherited predispositions and immunologic triggers. Although studying immunologic signals and performing genome-wide association studies are ideal approaches to tackle glomerular diseases in the kidney allograft, such studies are challenging because of the lack of adequately powered cohorts. In this review, we focus on the most commonly encountered recurrent and de novo glomerular diseases in the kidney allograft. We address the important advances made in understanding the immunopathology and genetic susceptibility of glomerular diseases in the native kidney and how to benefit from such knowledge to further our knowledge of post-transplant glomerular diseases. Defining genomic and immune predictors for glomerular diseases in the kidney allograft would support novel donor-recipient matching strategies and development of targeted therapies to ultimately improve long-term kidney allograft survival.

Rapamycin attenuates PLA2R activation-mediated podocyte apoptosis via the PI3K/AKT/mTOR pathway

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome in adults without diabetes. Primary MN has been associated with circulating antibodies against native podocyte antigens, including phospholipase A2 receptor (PLA2R); however, precision therapy targeting the signaling cascade of PLA2R activation is lacking. Both PLA2R and the mammalian target of rapamycin (mTOR) exist in podocytes, but the interplay between these two proteins and their roles in MN warrants further exploration. This study aimed to investigate the crosstalk between PLA2R activation and mTOR signaling in a human podocyte cell line. We demonstrated that podocyte apoptosis was induced by Group IB secretory phospholipase A2 (sPLA2IB) in a concentration- and time-dependent manner via upregulation of phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), and mTOR, and inhibited by rapamycin or LY294002. Furthermore, aberrant activation of the PI3K/AKT/mTOR pathway triggers both extrinsic (caspase-8 and caspase-3) and intrinsic (Bcl-2-associated X protein [BAX], B-cell lymphoma 2 [BCL-2], cytochrome c, caspase-9, and caspase-3) apoptotic cascades in podocytes. The therapeutic implications of our findings are that strategies to reduce PLA2R activation and PI3K/AKT/mTOR pathway inhibition in PLA2R-activated podocytes help protect podocytes from apoptosis. The therapeutic potential of rapamycin shown in this study provides cellular evidence supporting the repurposing of rapamycin for MN treatment.

Complete Resolution of Paraneoplastic Membranous Nephropathy Following Curative Therapy of Triple-Negative Breast Cancer

A paraneoplastic syndrome, which includes glomerulopathy, is a manifestation of malignancy unexplained by direct tumor burden. Membranous nephropathy (MN) may be associated with malignancies that are primarily solid tumors of the lung, prostate and gastrointestinal tract. It is rarely associated with breast cancer. To our knowledge, we herein report the first case of MN associated with triple-negative carcinoma of the breast. The patient initially presented with MN as a paraneoplastic nephrotic syndrome. Treatment resulting in a complete pathological response of the breast cancer also resolved the MN. Neither has recurred after a 48-month follow-up. The patient exhibited autoantibodies against phospholipase A2 receptor and was also antinuclear antibody (ANA) and anti-Smith (anti-Sm) antibody positive. These results suggest that the neoplasm evoked an autoimmune response, which resolved with treatment. ANA and anti-SM positivity closely correlated with the neoplasm activity supporting this hypothesis.

Characteristics of Anti-Contactin1 Antibody-Associated Autoimmune Nodopathies With Concomitant Membranous Nephropathy

Background

The concurrence of anti-contactin 1 (CNTN1) antibody-associated chronic inflammatory demyelinating polyneuropathy (CIDP) and membranous nephropathy (MN) has previously been reported in the literature. CIDP with autoantibodies against paranodal proteins are defined as autoimmune nodopathies (AN) in the latest research. In view of the unclear relationship between CIDP and MN, we performed a case study and literature review to investigate the clinical characteristics of anti-CNTN antibody-associated AN with MN.

Methods

We detected antibodies against NF155, NF186, CNTN1, CNTN2, CASPR1 and PLA2R in blood samples of a patient with clinically manifested MN and concomitant peripheral neuropathy via double immunofluorescence staining and conducted a quantitative measurement of anti-PLA2R IgG antibodies via enzyme-linked immunosorbent assay (ELISA). Case reports of anti-CNTN1 antibody-associated AN, anti-CNTN1 antibody-associated AN with MN, and CIDP with MN were retrieved through a literature search for a comparative analysis of clinical characteristics. The cases were grouped according to the chronological order of CIDP and MN onset for the comparison of clinical characteristics.

Results

A 57-year-old man with anti-PLA2R positive MN was admitted to the hospital due to limb numbness, weakness, and proprioceptive sensory disorder. He was diagnosed with anti-CNTN1 antibody-associated AN and recovered well after immunotherapy. Our literature search returned 22 cases of CIDP with MN that occurred before, after, or concurrently with CIDP. Good responses were achieved with early single-agent or combination immunotherapy, but eight out of the 22 patients with CIDP and concomitant MN ultimately developed different motor sequelae. Five patients had anti-CNTN1 antibody-associated AN with MN. Among these patients, males accounted for the majority of cases (male:female=4:1), the mean age at onset was late (60.2 ± 15.7 years, range 43–78 years), and 40% had acute to subacute onset. Clinical manifestations included sensory-motor neuropathy, sensory ataxia caused by proprioceptive impairment, and elevated cerebrospinal fluid protein levels.

Conclusion

The age at onset of CIDP with MN was earlier than that of anti-CNTN1 antibody-associated AN. MN may occur before, after or concurrently with CIDP. The early detection and isotyping of anti-CNTN1 and anti-PLA2R antibodies and the monitoring of isotype switching may be essential for suspected CIDP patients.

A study of altered calcium sensing system caused primary membranous nephropathy to end-stage renal failure

PMN (primary membranous nephropathy) is the most prevalent source of idiopathic nephrotic syndrome, which further progressed to ESRD (end-stage renal disease) in non-diabetic adults worldwide. Autoantibodies circulating against podocyte membrane proteins PLA2R1 and THSD7A are present in approximately 75-80% of incidents. Furthermore, a research presented an unusual case of IgG4-RD correlated with elevated serum levels of calcium concluded that renal irregularities have been preceded and triggered by hypercalcemia. In-addition, previous research also indicates an elevated amount of calcium in the blood of PMN patients. However, we also found conflicting evidence from previous studies showing that autoantibodies that suppress the calcium-sensing receptor (CaSR) induce a high level of calcium in some cases of IgG4RD. Notably, the calcium ion plays a critical function not only as intracellular signaling molecule but binds extracellular receptor activity to intracellular events. Moreover, the raise in intracellular calcium levels during PMN is known as a crucial event involved in the activation of numerous nucleases, proteases and implicitly facilitates the release of prostaglandins, cytokines and superoxide radicals capable of causing cell damage and death. Thus, the precise mechanism of the PMN disease to renal failure is not fully clear and the disease incidence differs among patients. Therefore, we are hypothesizing the role of disrupted calcium signaling in PMN that progress to ESRD.

Advances in antigens associated with Idiopathic Membranous Nephropathy

Membranous nephropathy (MN) is a common cause of nephrotic syndrome in adults. Idiopathic MN (IMN), one of the forms of MN, usually has an unknown etiology. IMN is described as an autoimmune disease, and its pathogenesis is quite complex. The discovery of the M-type phospholipase A₂ receptor (PLA₂R) plays an important role in promoting our understanding of IMN, although the exact mechanisms of its occurrence and development are still not completely clear. Other target antigens have been discovered one after another, as considerable progress has been made in the molecular pathomechanisms of IMN. Here, we review the findings about the target antigens associated with IMN in recent years. It is hoped that this article can provide researchers with some scientific issues or innovative ideas for future studies of IMN, which will provide clinicians with more knowledge about further improving their abilities to provide better medical care for IMN patients.

Single-Cell Profiling Reveals Transcriptional Signatures and Cell-Cell Crosstalk in Anti-PLA2R Positive Idiopathic Membranous Nephropathy Patients

Idiopathic membranous nephropathy (IMN) is an organ-specific autoimmune disease of the kidney glomerulus. It may gradually progress to end-stage renal disease (ESRD) characterized by increased proteinuria, which leads to serious consequences. Although substantial advances have been made in the understanding of the molecular bases of IMN in the last 10 years, certain questions remain largely unanswered. To define the transcriptomic landscape at single-cell resolution, we analyzed kidney samples from 6 patients with anti-PLA2R positive IMN and 2 healthy control subjects using single-cell RNA sequencing. We then identified distinct cell clusters through unsupervised clustering analysis of kidney specimens. Identification of the differentially expressed genes (DEGs) and enrichment analysis as well as the interaction between cells were also performed. Based on transcriptional expression patterns, we identified all previously described cell types in the kidney. The DEGs in most kidney parenchymal cells were primarily enriched in genes involved in the regulation of inflammation and immune response including IL-17 signaling, TNF signaling, NOD-like receptor signaling, and MAPK signaling. Moreover, cell-cell crosstalk highlighted the extensive communication of mesangial cells, which infers great importance in IMN. IMN with massive proteinuria displayed elevated expression of genes participating in inflammatory signaling pathways that may be involved in the pathogenesis of the progression of IMN. Overall, we applied single-cell RNA sequencing to IMN to uncover intercellular interactions, elucidate key pathways underlying the pathogenesis, and identify novel therapeutic targets of anti-PLA2R positive IMN.

A conceptual framework linking immunology, pathology, and clinical features in primary membranous nephropathy

Primary membranous nephropathy is a leading cause of adult nephrotic syndrome. The field took a major step forward with the identification of phospholipase A2 receptor (PLA2R) as a target antigen in the majority of cases and with the ability to measure circulating autoantibodies to PLA2R. Since then, the existence of additional target antigens such as thrombospondin type-1 domain-containing 7A, exostosin 1 and 2, neural EGFL like 1, and semaphorin 3B has been demonstrated. The ability to detect and monitor levels of circulating autoantibodies has opened a new window onto the humoral aspect of primary membranous nephropathy. Clinicians now rely on clinical parameters such as proteinuria, as well as levels of circulating autoantibodies against PLA2R and the results of immunofluorescence staining for PLA2R within kidney biopsy tissue, to guide the management of this disease. The relationship between immunologic and clinical disease course is consistent, but not necessarily intuitive. In addition, kidney biopsy provides only a single snapshot of disease that needs to be interpreted in light of changing clinical and serological findings. A clear understanding of these dynamic parameters is essential for staging, treatment, and management of this disease. This review aims to shed light on current knowledge regarding the development and time course of changes in the serum levels of autoantibodies against PLA2R, proteinuria, and histological findings that underlie the pathophysiology of primary membranous nephropathy.

Pathophysiology, diagnosis, and treatment of membranous nephropathy

Nephrotic syndrome is in adult patients mainly due to membranous nephropathy (MN) characterized by thickening of the glomerular basement membrane (GBM) and immune complex formation between podocytes and the GBM. Autoantibodies directed against the M-type phospholipase A2 receptor (PLA2R) and thrombospondin 1 domain-containing 7 A (THSD7A) can be used as diagnostic biomarkers. THSD7A seems to be of direct pathogenic significance as is suggested by experimental models and plasmapheresis in humans. Recently, further antigens like NELL-1 (neural tissue encoding protein with EGF-like repeats-1), exostosin 1 and 2 have been discovered. Thus, MN should be classified into antibody positive and antibody negative MN. More specific immunosuppressive treatments directed against B-cells and antibody production like rituximab have been introduced in addition to already existing immunosuppressive protocols including steroids, chlorambucil, cyclophosphamide, and calcineurin inhibitors. Antibody removal using immunoadsorption or plasmapheresis leads to short-term reduction in proteinuria and might be indicated only in patients with very severe proteinuria and complications. Studies are needed to identify a more specific immunosuppression directed against the production and effects of autoantibodies in order to protect the kidneys from autoimmune mediated tissue damage and to identify patients who require an immunosuppressive treatment, as the remission rate is high in patients with MN.

The correlation of anti-β2-glycoprotein I antibody with complement activation in patients with idiopathic membranous nephropathy

PURPOSE

This study evaluated the correlation of anti-β2-glycoprotein I (anti-β2-GPI) antibodies with complement activation in patients with idiopathic membranous nephropathy (IMN).

METHODS

Thirty-two IMN patients with positive anti-β2-GPI antibody were enrolled, and 32 age- and sex-matched IMN patients with negative anti-β2-GPI antibody were randomly enrolled as controls. The frozen serum samples of these 64 patients were collected for detection of anti-phospholipase A2 receptor (PLA2R) antibody and the activity of three complement pathways. Paraffin specimens of the kidney tissues of these 64 patients were collected for immunohistochemical staining of C4d.

RESULTS

IMN patients with positive anti-β2-GPI antibody had a significant decline of the residual complement activity of alternative pathway than those with negative anti-β2-GPI antibody (37.4 ± 21.2% vs 65.7 ± 50.5%, P = 0.021). The positive rate of kidney C4d staining in IMN patients with and without anti-β2-GPI was 65.6 and 81.2%, with no significant difference (P = 0.257). Patients with and without anti-β2-GPI had the same positive rate of anti-PLA2R antibody.

CONCLUSION

Anti-β2-GPI antibody was associated with alternative complement activation in patients with IMN.

M2 Macrophage Subpopulations in Glomeruli Are Associated With the Deposition of IgG Subclasses and Complements in Primary Membranous Nephropathy

Objectives: The role of M2 macrophages in the pathogenesis and progression of primary membranous nephropathy (PMN) remains unknown. In this study, we aimed to investigate the relationship between M2 subsets and clinicopathological features of patients with PMN. Methods: A total of 55 patients with PMN confirmed by biopsy were recruited. The clinical and pathological data were recorded, respectively. Immunohistochemistry was used to detect the markers of M2 macrophages, including total macrophages (CD68+), M2a (CD206+), M2b (CD86+) and M2c (CD163+). Results: The numbers of glomerular macrophages, M2a, M2b, and M2c macrophages were 1.83 (1.00, 2.67), 0.65 (0.15, 1.15), 0.67 (0.33, 1.50), and 0.80 (0.05, 2.30) per glomerulus, respectively. Higher number of glomerular macrophages was found in stage II compared with stage III (2.08 vs. 1.16, P = 0.008). These macrophages also were negatively correlated with serum albumin level (r = -0.331, P = 0.014), while positively associated with complement 3 (C3) deposition (r = 0.300, P = 0.026) and the severity of glomerulosclerosis (r = 0.276, P = 0.041). Moreover, glomerular M2a macrophages were significantly correlated with the deposition of C3 (r = 0.300, P = 0.026), immunoglobulin G1 (IgG1) (r = 0.339, P = 0.011), immunoglobulin G2 (IgG2) (r = 0.270, P = 0.046) and immunoglobulin G3 (IgG3) (r = 0.330, P = 0.014) in glomerular basement membrane (GBM). In addition, M2b macrophages were positively associated with IgG1 (r = 0.295, P = 0.029) and IgG2 (r = 0.393, P = 0.003), while M2c macrophages were negatively correlated with complement 4d (C4d) (r = -0.347, P = 0.009) in GBM. Conclusions: Our results showed that M2 macrophage subpopulations in glomeruli are associated with the deposition of IgG subclasses and complements in renal tissue of PMN, which indicate that M2 macrophages may be involved in the pathogenesis and progression of PMN. Moreover, M2a and M2c macrophages might show different tendencies in the pathogenesis of PMN.

Functional Magnetic Resonance Imaging Versus Kidney Biopsy to Assess Response to Therapy in Nephrotic Syndrome: A Case Report

In recent years, kidney functional magnetic resonance imaging (MRI) has seen great advances, with several cross-sectional studies demonstrating correlations between MRI biomarkers and glomerular filtration rate. However, the potential of MRI to monitor response to therapy in kidney disease remains undescribed. In this case report, a man in his 40s with drug-resistant membranous nephropathy was addressed to ofatumumab therapy. He underwent kidney biopsy before and 2 years after treatment and repeat non–contrast-enhanced MRI of the kidney every 6 months. An age- and sex-matched healthy volunteer was included as a normal control. The patient showed a striking positive immunologic response to therapy. Repeat MRI of the kidney documented progressive kidney functional recovery, with a significant widespread increase in kidney diffusivity, assessed using diffusion-weighted imaging, paralleling the increase in glomerular filtration rate and regression of albuminuria. Renal blood flow and ultrafiltration coefficient, assessed using phase-contrast MRI, significantly increased, suggesting an increase in filtration fraction. This case report provides the first clinical evidence in support of MRI of the kidney as a tool to noninvasively monitor pathophysiologic changes occurring in response to treatment. Although kidney biopsy remains critical for diagnosis, functional MRI of the kidney has promise for monitoring disease progression and response to therapy.

Meta-Analysis of the Diagnostic Efficiency of THSD7A-AB for the Diagnosis of Idiopathic Membranous Nephropathy

Thrombospondin type I domain-containing 7A (THSD7A), is a specific autoantigen of adult idiopathic membranous nephropathy (IMN), whose circulating antibody (THSD7A-AB) represents a promising biomarker for diagnosis of IMN. The objective of this meta-analysis is to investigate the diagnostic efficiency of THSD7A-AB for IMN. After rigorous data extraction, quality assessment, and data analysis, 10 articles (4545 patients) are included. For IMN, the summary sensitivity is 4% (2-7%), and the specificity is 99% (98-100%). The summary positive likelihood ratio (PLR) and negative likelihood ratio (NLR) are 5.40 (2.40-11.90) and 0.97 (0.95-0.99), respectively. The diagnostic odds ratio (DOR) is 6.00 (2.00-12.00). The area under the summary receiver operating characteristic curve (AUC) is 0.78 (0.74-0.81). For M-type phospholipase A2 receptor (PLA2R)-negative IMN, the summary sensitivity is 8% (6-10%), specificity is 100% (99-100%). The summary PLR and NLR are 15.80 (5.70-44.00) and 0.93 (0.91-0.95), respectively. The DOR is 17.00 (6.00-48.00). The AUC is 0.99 (0.98-1.00). THSD7A-AB has higher diagnostic value in PLA2R-negative patients than in IMN patients. These results suggest that THSD7A-AB could possibly be applied as an auxiliary non-invasive diagnostic method for PLA2R-negative IMN.

The gut microbiome in differential diagnosis of diabetic kidney disease and membranous nephropathy

Background

Diabetic kidney disease (DKD) and membranous nephropathy (MN) are the two major causes of end-stage renal disease (ESRD). Increasing evidence has shown that intestinal dysbiosis is associated with many diseases. The aim of this study was to explore the composition of the gut microbiome in DKD and MN patients.

Methods

16S rRNA gene sequencing was performed on 271 fecal samples (DKD = 129 and MN = 142), and taxonomic annotation of microbial composition and function was completed.

Results

We observed distinct microbial communities between the two groups, with MN samples exhibiting more severe dysbiosis than DKD samples. Relative increases in genera producing short-chain fatty acids (SCFAs) in DKD and a higher proportion of potential pathogens in MN were the main contributors to the microbiome alterations in the two groups. Five-fold cross-validation was performed on a random forest model, and four operational taxonomic unit (OTU)-based microbial markers were selected to distinguish DKD from MN. The results showed 92.42% accuracy in the training set and 94.52% accuracy in the testing set, indicating high potential for these microbiome-based markers in separating MN from DKD. Overexpression of several amino acid metabolic pathways, carbohydrate metabolism and lipid metabolism was found in DKD, while interconversion of pentose/glucoronate and membrane transport in relation to ABC transporters and the phosphotransferase system were increased in MN.

Conclusion

The composition of the gut microbiome appears to differ considerably between patients with DKD and those with MN. Thus, microbiome-based markers could be used as an alternative tool to distinguish DKD and MN.