Glomerular diseases: membranous nephropathy--a modern view

Observational study of immunosuppressive treatment patterns and outcomes in primary membranous nephropathy: a multicenter retrospective analysis

BACKGROUND

We evaluated the efficacy of different immunosuppressive regimens in patients with primary membranous nephropathy in a large national cohort.

METHODS

In this registry study, 558 patients from 47 centers who were treated with at least one immunosuppressive agent and had adequate follow-up data were included. Primary outcome was defined as complete (CR) or partial remission (PR). Secondary composite outcome was at least a 50% reduction in estimated glomerular filtration (eGFR), initiation of kidney replacement therapies, development of stage 5 chronic kidney disease, or death.

RESULTS

Median age at diagnosis was 48 (IQR: 37-57) years, and 358 (64.2%) were male. Patients were followed for a median of 24 (IQR: 12-60) months. Calcineurin inhibitors (CNIs) with or without glucocorticoids were the most commonly used regimen (43.4%), followed by glucocorticoids and cyclophosphamide (GC-CYC) (39.6%), glucocorticoid monotherapy (25.8%), and rituximab (RTX) (9.1%). Overall remission rate was 66.1% (CR 26.7%, PR 39.4%), and 59 (10.6%) patients reached secondary composite outcome. Multivariate logistic regression showed that baseline eGFR (OR 1.011, 95% CI: 1.003-1.019, p = 0.007), serum albumin (OR 1.682, 95% CI: 1.269-2.231, p < 0.001), and use of RTX (OR 0.296, 95% CI: 0.157-0.557, p < 0.001) were associated with remission rates; whereas only lower baseline hemoglobin was significantly associated with secondary composite outcome (OR: 0.843, 95% CI: 0.715-0.993, p = 0.041). CYC use was significantly associated with higher remission (OR 1.534, 95% CI: 1.027-2.290, p = 0.036).

CONCLUSIONS

Higher baseline eGFR and serum albumin levels correlated with increased remission rates. Remission rates were lower in patients treated with RTX, while those on GC-CYC showed higher rates of remission. Due to the study's retrospective nature and multiple treatments used, caution is warranted in interpreting these findings.

Current progress in CAR-based therapy for kidney disease

Despite significant breakthroughs in the understanding of immunological and pathophysiological features for immune-mediated kidney diseases, a proportion of patients exhibit poor responses to current therapies or have been categorized as refractory renal disease. Engineered T cells have emerged as a focal point of interest as a potential treatment strategy for kidney diseases. By genetically modifying T cells and arming them with chimeric antigen receptors (CARs), effectively targeting autoreactive immune cells, such as B cells or antibody-secreting plasma cells, has become feasible. The emergence of CAR T-cell therapy has shown promising potential in directing effector and regulatory T cells (Tregs) to the site of autoimmunity, paving the way for effective migration, proliferation, and execution of suppressive functions. Genetically modified T-cells equipped with artificial receptors have become a novel approach for alleviating autoimmune manifestations and reducing autoinflammatory events in the context of kidney diseases. Here, we review the latest developments in basic, translational, and clinical studies of CAR-based therapies for immune-mediated kidney diseases, highlighting their potential as promising avenues for therapeutic intervention.

From Diagnosis to Dialysis: Managing Primary Membranous Nephropathy in a Patient Living With Human Immunodeficiency Virus (HIV)

Membranous nephropathy (MN) is a significant cause of nephrotic syndrome in adults, with both primary and secondary etiologies contributing to its pathogenesis. This case report explores the clinical course of a 69-year-old African American man with human immunodeficiency virus (HIV) who developed primary MN, progressing to end-stage renal disease (ESRD) despite treatment efforts. Initially diagnosed with IgA nephropathy and HIV-associated immune complex kidney disease (HIVICK), the patient later developed anti-phospholipase A2 receptor (anti-PLA2R) antibody-positive MN. Despite immunosuppressive therapy and partial remission with rituximab, non-adherence to treatment led to disease exacerbation and eventual hospitalization for acute heart failure and worsening renal function. A subsequent renal biopsy revealed severe interstitial fibrosis and tubular atrophy, limiting further therapeutic options. This case underscores the challenges in managing MN, particularly in high-risk patients with comorbidities such as HIV, and highlights the importance of adherence to treatment and tailored management strategies to optimize outcomes in this complex condition.

A dynamic online nomogram for predicting renal outcomes of idiopathic membranous nephropathy

BACKGROUND

Because spontaneous remission is common in IMN, and there are adverse effects of immunosuppressive therapy, it is important to assess the risk of progressive loss of renal function before deciding whether and when to initiate immunosuppressive therapy. Therefore, this study aimed to establish a risk prediction model to predict patient prognosis and treatment response to help clinicians evaluate patient prognosis and decide on the best treatment regimen.

METHODS

From September 2019 to December 2020, a total of 232 newly diagnosed IMN patients from three hospitals in Liaoning Province were enrolled. Logistic regression analysis selected the risk factors affecting the prognosis, and a dynamic online nomogram prognostic model was constructed based on extreme gradient boost, random forest, logistic regression machine learning algorithms. Receiver operating characteristic and calibration curves and decision curve analysis were utilized to assess the performance and clinical utility of the developed model.

RESULTS

A total of 130 patients were in the training cohort and 102 patients in the validation cohort. Logistic regression analysis identified four risk factors: course ≥ 6 months, UTP, D-dimer and sPLA2R-Ab. The random forest algorithm showed the best performance with the highest AUROC (0.869). The nomogram had excellent discrimination ability, calibration ability and clinical practicability in both the training cohort and the validation cohort.

CONCLUSIONS

The dynamic online nomogram model can effectively assess the prognosis and treatment response of IMN patients. This will help clinicians assess the patient's prognosis more accurately, communicate with the patient in advance, and jointly select the most appropriate treatment plan.

Membranous Nephropathy as a Paraneoplastic Syndrome in Cancer of Unknown Primary

BACKGROUND/AIM

Membranous nephropathy (MN) is a nephrotic syndrome with both idiopathic and secondary etiologies. The mechanism of cancer-associated MN is presumed to involve the immunological production of antibodies against a tumor antigen, although little is known about the detailed mechanism. Lung cancer is a major neoplasm associated with cancer-associated MN. However, the simultaneous occurrence of secondary MN in patients with cancer of unknown primary (CUP) remains unclear.

CASE REPORT

Here, we present a case of secondary MN in a 72-year-old female as a paraneoplastic syndrome in CUP. Thoracic radiotherapy up to a total of 60 Gy was initially performed on the right subclavian and mediastinal lymph nodes. Computed tomography revealed marked shrinking of these lymph nodes, and the secondary MN also improved without any symptoms.

CONCLUSION

The presence of proteinuria in patients with CUP suggests the possibility of secondary MN as a rare differential diagnosis.

Fangji Huangqi decoction ameliorates membranous nephropathy through the upregulation of BNIP3-mediated mitophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Fangji Huangqi Decoction (FJHQ), a traditional Chinese medicinal formula outlined in Zhang Zhongjing's "Jin Gui Yao Lue" during the Han Dynasty, is often used to treat conditions characterized by symptoms like edema and dysuria, including membranous nephropathy (MN). Despite its proven clinical effectiveness, the exact mechanisms through which FJHQ acts on MN remain elusive.

AIM OF THE STUDY

This study aimed to investigate whether FJHQ enhances BNIP3-mediated mitophagy in podocytes by promoting BNIP3 expression and whether this improvement leads to the amelioration of MN.

MATERIALS AND METHODS

In this study, by establishing passive Heymann nephritis (PHN) rats, an experimental rat model of MN induced by sheep anti-rat Fx1A serum, we evaluated the effects of FJHQ in vivo. In vitro experiments were carried out by treating primary podocytes with experimental rat serum. Furthermore, the potential mechanism by which FJHQ acts through BNIP3 was further examined by transfecting primary podocytes with the siRNA of BNIP3 or the corresponding control vector.

RESULTS

After 4 weeks, significant kidney damage was observed in the rats in the model group, comparatively, FJHQ markedly decreased urine volume, 24-h urinary protein, blood urea nitrogen (BUN), creatinine (Scr), and increased serum total albumin (ALB). Histology showed that FJHQ caused significant improvements in glomerular hyperplasia, and IgG immune complex deposition in MN rats. JC-1 fluorescence labelling and flow cytometry analysis showed that FJHQ could significantly increase mitochondrial membrane potential in vivo. In the mitochondria of MN model rats, FJHQ was able to down-regulate the expression of P62 and up-regulate the expression of BNIP3, LC3B, and LC3 II/LC3 I, according to Western blot and immunofluorescence studies. Furthermore, FJHQ has been shown to significantly up-regulate mitochondrial membrane potential, down-regulate P62 expression in mitochondria, and up-regulate the expression of BNIP3, LC3B, and LC3 II/LC3 I in mitochondria at the cellular level. After the administration of the autophagy inhibitor chloroquine, the serum of rats treated with FJHQ further increased the expression of LC3 II/LC3 I in primary podocytes, showing higher autophagy flow. After the interference of BNIP3 in podocytes, the effect of FJHQ on mitochondrial membrane potential and autophagy-related proteins almost disappeared.

CONCLUSION

FJHQ enhanced mitophagy in podocytes by promoting the expression of BNIP3, thereby contributing to the amelioration of MN. This work reveals the possible underlying mechanism by which FJHQ improves MN and provides a new avenue for MN treatment.

Klotho Stabilizes the Podocyte Actin Cytoskeleton in Idiopathic Membranous Nephropathy through Regulating the TRPC6/CatL Pathway

INTRODUCTION

The aim of this study was to explore the renoprotective effects of Klotho on podocyte injury mediated by complement activation and autoantibodies in idiopathic membranous nephropathy (IMN).

METHODS

Rat passive Heymann nephritis (PHN) was induced as an IMN model. Urine protein levels, serum biochemistry, kidney histology, and podocyte marker levels were assessed. In vitro, sublytic podocyte injury was induced by C5b-9. The expression of Klotho, transient receptor potential channel 6 (TRPC6), and cathepsin L (CatL); its substrate synaptopodin; and the intracellular Ca2+ concentration were detected via immunofluorescence. RhoA/ROCK pathway activity was measured by an activity quantitative detection kit, and the protein expression of phosphorylated-LIMK1 (p-LIMK1) and p-cofilin in podocytes was detected via Western blotting. Klotho knockdown and overexpression were performed to evaluate its role in regulating the TRPC6/CatL pathway.

RESULTS

PHN rats exhibited proteinuria, podocyte foot process effacement, decreased Klotho and Synaptopodin levels, and increased TRPC6 and CatL expression. The RhoA/ROCK pathway was activated by the increased phosphorylation of LIMK1 and cofilin. Similar changes were observed in C5b-9-injured podocytes. Klotho knockdown exacerbated podocyte injury, while Klotho overexpression partially ameliorated podocyte injury.

CONCLUSION

Klotho may protect against podocyte injury in IMN patients by inhibiting the TRPC6/CatL pathway. Klotho is a potential target for reducing proteinuria in IMN patients.

HBx-induced PLA2R overexpression mediates podocyte pyroptosis through the ROS-NLRP3 signaling pathway

INTRODUCTION

Hepatitis B virus-associated glomerulonephritis (HBV-GN) is one of the main types of secondary glomerular diseases, and podocyte injury is an important pathogenic mechanism of HBV-GN, participating in the occurrence and development of HBV-GN. However, the specific mechanism of podocyte injury remains to be studied.

METHODS

Human renal podocytes cultured in vitro were divided into six groups. The podocyte morphology was observed under a transmission electron microscope, and the expression of M-type phospholipase A₂ receptor (M-PLA₂R) on the podocyte membrane was observed by indirect immunofluorescence staining under a fluorescence microscope. The pyroptosis rate and reactive oxygen species (ROS) of podocytes were assessed by FLICA/PI double staining and flow cytometry. Western blot (WB) and quantitative real-time PCR (qPCR) were used to determine the expression of PLA₂R, nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), apoptosis-associated speck-like protein containing card (ASC), caspase-1, IL-1β, and IL-18.

RESULTS

Hepatitis B virus X (HBx) transfected into human renal podocytes in vitro induced the overexpression of PLA₂R. Moreover, the overexpressed PLA₂R combined with secretory phospholipase A₂ group IB (sPLA₂-IB) aggravated podocyte injury and increased the pyroptosis rate. In addition, the expression of ROS, the NLRP3 inflammasome and downstream inflammatory factors was increased. In contrast, after inhibiting the expression of PLA₂R and ROS, podocyte damage was alleviated, and the pyroptosis rate and the expression of genes related to the ROS-NLRP3 signaling pathway were decreased.

CONCLUSION

HBx-induced PLA₂R overexpression on the podocyte membrane can significantly upregulate the ROS-NLRP3 signaling pathway, thereby mediating podocyte pyroptosis.

Environmental pollutants induce NLRP3 inflammasome activation and pyroptosis: Roles and mechanisms in various diseases

Environmental pollution is changing with economic development. Most environmental pollutants are characterized by stable chemical properties, strong migration, potential toxicity, and multiple exposure routes. Harmful substances are discharged excessively, and large quantities of unknown new compounds are emerging, being transmitted and amplifying in the food chain. The increasingly severe problems of environmental pollution have forced people to re-examine the relationship between environmental pollution and health. Pyroptosis and activation of the NLRP3 inflammasome are critical in maintaining the immune balance and regulating the inflammatory process. Numerous diseases caused by environmental pollutants are closely related to NLRP3 inflammasome activation and pyroptosis. We intend to systematically explain the steps and important events that are common in life but easily overlooked by which environmental pollutants activate the NLRP3 inflammasome and pyroptosis pathways. This comprehensive review also discusses the interaction network between environmental pollutants, the NLRP3 inflammasome, pyroptosis, and diseases. Thus, research progress on the impact of decreasing oxidative stress levels to inhibit the NLRP3 inflammasome and pyroptosis, thereby repairing homeostasis and reshaping health, is systematically examined. This review aims to deepen the understanding of the impact of environmental pollutants on life and health and provide a theoretical basis and potential programs for the development of corresponding treatment strategies.

Overlap of Primary Membranous Nephropathy, IgA Nephropathy, and Diabetic Nephropathy: A Case Report

The coexistence of primary membranous nephropathy (PMN), immunoglobulin A nephropathy (IgAN), and diabetic nephropathy (DN) in the same patient has been a subject of clinical and pathological investigation, yielding inconclusive results. The limited availability of cases and resource materials has hindered a comprehensive understanding of this phenomenon. We present the case of a 70-year-old Saudi Arabian man diagnosed with type 2 diabetes mellitus and nephrotic syndrome. A kidney biopsy revealed the coexistence of PMN, IgAN, and DN. The patient presented with an unusual and rare combination of PMN, IgAN, and DN. To address his condition, the patient consented to rituximab therapy and planned follow-up with the kidney transplant team. However, before the first dose of rituximab could be administered, the patient experienced severe septic shock secondary to pneumonia, which tragically led to his demise. The simultaneous occurrence of PMN, IgAN, and DN represents a rare and scarcely documented condition. The purpose of this article is to report this exceptional case, emphasizing the significance of further research to deepen the understanding of the underlying pathology behind these concurrent renal disorders. This report aims to shed light on the complexities of managing such complex cases and advancing therapeutic approaches in the future.

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.

Comparison of performance and clinical utility of different methods for detecting anti-PLA2R antibody

OBJECTIVES

This study aimed to compare the performance of enzyme-linked immunosorbent assay (ELISA) and magnetic particle chemiluminescence immunoassay (MP-CLIA) for detecting anti-phospholipase A2 receptor (PLA2R) antibody and their clinical significance in idiopathic membranous nephropathy (IMN) patients.

METHODS

Serum samples from 448 patients with different types of nephropathy, including 222 with IMN, were tested using both methods. Sensitivity, specificity, and prognostic significance of PLA2R antibody levels were evaluated.

RESULTS

Similar sensitivity and specificity of ELISA and MP-CLIA in identifying IMN patients was found. However, MP-CLIA performed better than ELISA in predicting the prognosis of IMN patients. Adjusting the cutoff value reduced the false-negative rate in both methods. Logistic regression analysis identified six variables, including MP-CLIA-PLA2R levels, eGFR, lymphocyte count, B lymphocyte count, NK cell count, and complement 4, as predictors of renal function outcomes in IMN patients.

CONCLUSIONS

Both ELISA and MP-CLIA are reliable methods for detecting anti-PLA2R antibodies in IMN patients. However, MP-CLIA is more accurate in predicting the prognosis of IMN. Combining MP-CLIA-PLA2R with other variables can help predict renal function outcomes in IMN patients. Our study emphasizes the importance of considering both analytical performance and clinical utility when selecting a PLA2R antibody assay kit.

Single-Nephron GFR in Different Glomerular Basement Membrane Stages of Membranous Nephropathy

Key Points

The first study that estimated single-nephron GFR (SNGFR) in patients with membranous nephropathy (MN). Associations of SNGFR with MN staging by electron microscopy and clinicopathologic findings were cross-sectionally investigated. This study illustrates a role for disease-specific GBM structural lesions as determinants of SNGFR in patients with MN.

Background

Alterations in single-nephron dynamics have been demonstrated in animal models of membranous nephropathy (MN). This study applied a recently developed technique to estimate single-nephron parameters in human MN.

Methods

Single-nephron GFR (SNGFR) and single-nephron urinary protein excretion (SNUPE) were calculated by dividing total GFR and UPE by the total estimated number of nonglobally sclerotic glomeruli (NSG). The NSG number per kidney was estimated using cortical volume assessment and biopsy-based stereology. MN staging by electron microscopy was performed using Ehrenreich-Churg (EC) criteria. Single-nephron parameters were analyzed in relation to clinicopathological factors known to associate with disease outcomes.

Results

The study included 109 patients with MN (mean age 65 years; 73% male; eGFR 62 ml/min, 36% on renin-angiotensin-aldosterone system inhibitors prebiopsy). EC stages were I, 19%; II, 49%; III, 26%; and IV, 6%. There was no difference in glomerular volume among EC stage groups. With advancing EC stage, SNGFR and SNUPE decreased from mean 56–42 nl/min and 5.1–3.8 µ g/d, respectively. In multivariable models, EC stage was associated with SNGFR even after adjustment for key clinicopathological factors, such as reduced GFR, serum albumin, UPE, segmental glomerulosclerosis, chronic tubulointerstitial damage, and prebiopsy use of renin-angiotensin-aldosterone system inhibitors. By contrast, EC stage was not associated with glomerular volume and SNUPE after multivariable adjustment.

Conclusions

These results provide the first clinical evidence of alterations in single-nephron dynamics with advancing EC stage of human MN and support a role for disease-specific glomerular basement membrane structural lesions as determinants of SNGFR.

Membranous nephropathy in a patient with ankylosing spondylitis: A rare renal manifestation or just a coincidence?

Renal involvement in ankylosing spondylitis (AS) is uncommon and usually secondary to amyloidosis or analgesic nephropathy. A 41-year-old female patient who was diagnosed with human leukocyte antigen-B27-positive AS 16 years ago was admitted to the rheumatology outpatient clinic with pretibial and pedal edema. She had nephrotic-range proteinuria. Renal biopsy findings confirmed the diagnosis of membranous nephropathy. Extensive malignancy evaluation was negative. Edema regressed, renal functions stabilized, and proteinuria reduced within two months after immunosuppressive therapy.

Myostatin silencing inhibits podocyte apoptosis in membranous nephropathy through Smad3/PKA/NOX4 signaling pathway

This article focuses on deciphering the effect of myostatin (MSTN) on podocyte apoptosis in membranous nephropathy (MN) and fathoming out its underlying mechanism. Rats received the intravenous injection of cationized-bovine serum albumin to induce MN in vivo, while angiotensin II (Ang II) was exposed to AB8/13 cells to induce MN model in vitro. The mRNA expression of MSTN was detected by qRT-PCR. The effects of MSTN silencing on MN model rats and cells were assessed by cell counting kit-8 assay, flow cytometry, hematoxylin and eosin staining, and TUNEL assay. The expressions of proteins related to apoptosis and Smad3/protein kinase A (PKA)/NADPH oxidase 4 (NOX4) signaling pathway were examined by western blot. As a result, MSTN was highly expressed in MN cell and rat models. Besides, knockdown of MSTN elevated the MN cell viability and dwindled apoptosis rate, as well as attenuated kidney injury in MN rats. Meanwhile, MSTN silencing lessened the expressions of phosphorylated (p)-Smad3 and Nox4, while boosting the p-PKA expression in MN rats and cells. Additionally, Smad3 overexpression reversed the above effects of MSTN silencing on Ang II-induced podocytes. In conclusion, MSTN knockdown restrains the podocyte apoptosis through regulating Smad3/PKA/NOX4 signaling pathway.

Primary membranous nephropathy: an endless story

Primary membranous nephropathy (PMN) is an autoimmune disease caused by the attack of autoantibodies against podocyte antigens leading to the in situ production of immune complexes. However, the etiology is unknown and the pathogenesis is still far from being completely elucidated. MN is prevalently idiopathic or primary, but in about 20-30% of cases it is secondary to chronic infections, systemic diseases, exposure to drugs, or malignancy. The differentiation between primary and secondary MN may be difficult, particularly when MN precedes signs and symptoms of the original disease, as in some cases of cancer or systemic lupus erythematosus. The natural course of PMN is variable, but in the long term 40-60% of patients with nephrotic syndrome progress to end-stage renal disease (ESRD) or die from thrombotic or cardiovascular events. PMN is a treatable disease. Patients with asymptomatic proteinuria should receive supportive care. Immunosuppressive treatments should be given to patients with nephrotic syndrome or risk of progression. The most frequently adopted treatments rely on cyclical therapy alternating steroids with a cytotoxic agent every other month, i.e., rituximab at different doses, or calcineurin inhibitors plus low-dose steroids. A good rate of response may be obtained but relapses can occur. Randomized controlled trials, with adequate size, long-term follow-up, and fair definition of endpoints are needed to identify treatment with the best therapeutic index.

Computer-aided diagnosis of primary membranous nephropathy using expert system

BACKGROUND

The diagnosis of primary membranous nephropathy (PMN) often depends on invasive renal biopsy, and the diagnosis based on clinical manifestations and target antigens may not be completely reliable as it could be affected by uncertain factors. Moreover, different experts could even have different diagnosis results due to their different experiences, which could further impact the reliability of the diagnosis. Therefore, how to properly integrate the knowledge of different experts to provide more reliable and comprehensive PMN diagnosis has become an urgent issue.

METHODS

This paper develops a belief rule-based system for PMN diagnosis. The belief rule base is constructed based on the knowledge of the experts, with 9 biochemical indicators selected as the input variables. The belief rule-based system is developed of three layers: (1) input layer; (2) belief rule base layer; and (3) output layer, where 9 biochemical indicators are selected as the input variables and the diagnosis result is provided as the conclusion. The belief rule base layer is constructed based on the knowledge of the experts. The final validation was held with gold pattern clinical cases, i.e., with known and clinically confirmed diagnoses.

RESULTS

134 patients are used in this study, and the proposed method is defined by its sensitivity, specificity, accuracy and area under curve (AUC), which are 98.0%, 96.9%, 97.8% and 0.93, respectively. The results of this study present a novel and effective way for PMN diagnosis without the requirement of renal biopsy.

CONCLUSIONS

Through analysis of the diagnosis results and comparisons with other methods, it can be concluded that the developed system could help diagnose PMN based on biochemical indicators with relatively high accuracy.

Clinical characteristics of membranous nephropathy with spontaneous remission: An analysis of 24 patients

PURPOSE

To investigate the prognosis of patients with spontaneous remission (SR) of phospholipase A2 receptor (PLA2R)-associated membranous nephropathy (MN).

PATIENTS AND METHODS

Patients diagnosed with MN were recruited after examining their renal biopsy in the Renal Department of China-Japan Friendship Hospital between January 2015 and September 2021. Among them, 24 patients with SR were included in this study and follow-up.

RESULTS

Twenty-four patients diagnosed with SR of PLA2R-associated MN were recruited; 11 were male, and 13 were female, with a mean age of 49.5±14.5 years (range, 30-77 years). The initial 24-hour urinary total protein and serum albumin levels were 0.29±0.14g/d and 37.5±4.4g/L, respectively, and the initial serum creatinine was 65.0±15.8μmol/L. During the follow-up of 33.9±19.1 months (range, 6-73 months), 22 (91.7%) patients maintained remission; however, one patient had impaired renal function due to acute coronary syndrome and coronary angiography findings, and one patient experienced a repeated relapse caused by respiratory tract infection, at 50 and 70 months. A systematic review of the relevant literature was conducted, and records of patients with SR of PLA2R-associated MN were retrieved from 16 case reports or case series with a total of 97 cases.

CONCLUSIONS

Most patients with SR of MN had a promising long-term prognosis, with only a few cases of relapse.

Anti-glomerular basement membrane vasculitis

Antiglomerular basement membrane disease (anti-GBM) is a rare life-threatening autoimmune vasculitis that involves small vessels and it is characterized by circulating autoantibodies directed against type IV collagen antigens expressed in glomerular and alveolar basement membrane. The typical clinical manifestations are the rapidly progressive glomerulonephritis and the alveolar hemorrhage. The diagnosis is usually confirmed by the detection of anti-GBM circulating antibodies. If not rapidly recognized, anti-GBM disease can lead to end stage kidney disease (ESKD). An early diagnosis and prompt treatment with immunosuppressive therapies and plasmapheresis are crucial to prevent a poor outcome. In this review, we discuss the primary form of anti-GBM (the so called Goodpasture syndrome) but also cases associated with other autoimmune diseases such as antineutrophil-cytoplasmic-antibody (ANCA) vasculitis, membranous nephropathy, IgA nephritis and systemic lupus erythematosus (SLE), as well as the few cases of anti-GBM vasculitis complicating kidney transplantation in the Alport syndrome.

Determination of Anti-Phospholipase A2 and Anti-Thrombospondin Type 1 Domain-Containing Protein 7A in Latin Patients with Membranous Nephropathy

Primary membranous nephropathy (MN) is caused by antibodies against podocyte antigens, especially the type M receptor of phospholipase A2 (PLA2R) and thrombospondin type-1 domain containing 7 A (THSD7A). This study's aim was the determination of anti-PLA2R, anti-THSD7A serum antibodies, and anti-PLA2R renal tissue staining prevalence in a Latin population with MN, as well as evaluating their role as biomarkers for disease activity. The performance of the two anti-PLA2R serum diagnostic methods-ELISA and indirect immunofluorescence (IFI)-was evaluated for the diagnosis of MN. Fifty-nine patients, including 29 with MN, 18 with lupus membranous nephropathy (LMN) and 12 with focal and segmental glomerulosclerosis (FSGS), were evaluated for serum antibodies. Renal biopsies were also evaluated for the presence of anti-PLA2R staining. Twenty-one patients with MN were followed for 1 year. Patients with LMN and FSGS were negative for both antibodies. All 29 MN patients were negative for anti-THSD7A; 16 MN patients were positive for anti-PLA2R by ELISA and/or IFI, and 3 MN patients were positive for anti-PLA2R only by IFI. Thus, the anti-PLA2R ELISA test demonstrated 45% sensitivity and 97% specificity, while the IFI test showed, respectively, 55% and 100% in our MN patients. Among the 28 MN renal biopsies, 20 presented anti-PLA2R positive staining, corresponding to a 72% sensitivity. Positive correlations were observed between the anti-PLA2R ELISA titer and proteinuria. In conclusion, determination of anti-PLA2R antibodies in the MN Latin population showed similar rates to those reported for other populations. The anti-PLA2R serum levels correlated with MN disease activity.

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.

Lung cancer patients with nephropathy as the first manifestation: Literature review and clinical study report

Background

To investigate the relationship between membranous nephropathy (MN) and lung cancer.

Methods

To report patients with lung cancer detected by follow-up after the diagnosis of MN by renal biopsy in China-Japan Friendship Hospital from January 2010 to December 2019, and to study the prognosis of lung cancer-associated MN and have a review of the literature.

Results

Lung cancer was detected in six patients followed for 1–27 months (median 8 months) after the diagnosis of MN: including four cases of lung adenocarcinoma, one case of carcinoma in situ, and one case of small cell lung cancer with multiple metastases. Five cases were in remission after surgical resection, and one case was remitted after chemotherapy. Six patients were negative for serum anti-PLA2R antibodies, and glomerular IgG subclass deposition detected by immunofluorescence was positive for IgG1 and IgG2. Glomerular PLA2R, THSD7A, and NELL-1 stainings were assessed in all six patients; one patient was positive for glomerular PLA2R staining, two patients were positive for glomerular THSD7A staining, and all patients were negative for NELL-1 staining. A literature review of the relationship between MN and lung cancer was performed: seven articles about cancer-associated MN were searched, reporting 32 cases of MN associated with lung cancer, among which 14 cases had nephropathy as the first manifestation and only five patients had remission of MN after treatment of lung cancer.

Conclusions

A few lung cancer patients have nephropathy as the first clinical manifestation, and MN can also be remitted after treatment of lung cancer.

The Role of Anti-PLA2R and Anti-THSD7A Antibodies in the Pathogenesis and Diagnostics of Primary Membranous Nephropathy: A Review of Current Knowledge for Clinical Practice

Primary membranous nephropathy (PMN) is considered a major cause of nephrotic syndrome. The discovery of circulating autoantibodies directed against glomerular podocytes helped to classify them as autoimmune diseases. Over the past years, there has been an increasing significance of anti-Phospholipase A2 Receptor (anti-PLA₂R), which has been detected in 70–80% of PMN cases, and relevance of anti-Thrombospondin type I domain-containing 7A (anti-THSD7A) even though they are present in 2–5% of patients. The results of clinical and experimental studies indicate that these antibodies are pathogenic. It radically changed the diagnostic and therapeutic approach. Measurement of antibody titers in the serum seems to be a valuable tool for identifying PMN and for the assessment of disease activity. By monitoring pathogenic antibodies levels rather than proteinuria or reduced glomerular filtration rate (GFR) as an indicator of glomerular disease, physicians would easier divide patients into those with active and inactive PMN disease and decide about their therapy. The aim of this review is to evaluate scientific evidence about the role of autoantibodies, namely anti-PLA₂R and anti-THSD7A, as PMN biomarkers. The present manuscript focuses on PMN pathogenesis and key data of diagnosis, monitoring of the disease, and treatment strategies that are currently being used in clinical practice.

The Ameliorative Effect of Mahuang Fuzi and Shenzhuo Decoction on Membranous Nephropathy of Rodent Model is Associated With Autophagy and Wnt/β-Catenin Pathway

The increased incidence of membranous nephropathy (MN) has made it the most common pathological type of primary nephrotic syndrome in adults in China. According to the theory of Traditional Chinese Medicine (TCM), Mahuang Fuzi (Chinese ephedra and Radix Aconiti Lateralis Preparata) and Shenzhuo Decoction (MFSD) could be used to treat such diseases. We treated patients of MN with MFSD, and observed comparable efficacy to glucocorticoid and/or immunosuppressants. In this study, we observed the therapeutic effect of MFSD on the rat model of passive Heymann nephritis (PHN), a classical MN model. Our results showed that MFSD treatment significantly reduced urinary protein level and podocyte injury in PHN rats, and correspondingly improved renal pathology, with the improvement effect on MN comparable to that of Cyclosporine A (CsA) alone. To explore the potential therapeutical mechanism of MFSD, the main chemical components of MFSD were determined by High-performance liquid chromatography-mass spectrometry (HPLC-MS). There were about 30 active components of MFSD. Next, based on network pharmacology methods, we screened related targets of MSFD on MN, which provided a preliminary understanding of the MFSD bioactive compounds. The clustering analysis showed that its active site might be in the autophagy-related protein and Wnt/β-catenin pathway, which was related to podocyte injury. Finally, we observed an improvement in renal autophagy and a down-regulation of the Wnt/β-catenin pathway after MSFD treatment in a PHN rat model. According to this study, autophagy and Wnt/β-catenin pathway may be potential targets for MFSD in the treatment of 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.

Membranous nephropathy without vacuolated podocytes in Fabry disease treated with agalsidase-β and carbamazepine: A case report

RATIONALE

Vacuolated podocytes are the most common form of renal damage in Fabry disease, but other types of renal damage have been reported, such as membranous nephropathy (MN) or IgM nephropathy. Enzyme replacement therapy (ERT) is effective at preventing renal damage, but the nephropathies require appropriate treatment to prevent renal damage.

PATIENT CONCERNS

A 22-year-old male with Fabry disease presented with proteinuria during ERT with agalsidase-β and carbamazepine. He had received the treatment for 10 years and maintained normal plasma globotryaosylceramide levels.

DIAGNOSIS

Renal biopsy revealed MN without vacuolated podocytes. Immunofluorescent staining of the IgG subclass revealed granular patterns of IgG1, G2, G4, and C3 deposition in the glomerular basement membrane.

INTERVENTIONS

The carbamazepine dose was reduced from 600 mg/day to 200 mg/day (serum concentration 10.0-11.0-4.0-5.0 μg/mL).

OUTCOMES

After reducing the carbamazepine dose, proteinuria was negative, and the patient has had a normal urinalysis for 17 months. Plasma globotryaosylceramide levels have also remained normal.

LESSONS

This report is a reminder of the co-existence of MN without vacuolated podocytes in Fabry disease during ERT with agalsidase-β and carbamazepine.Physicians should be aware of this form of renal damage in Fabry disease, even during treatment.

Acute chest pain and dyspnoea as clinical presentation of primary membranous nephropathy. A case report and literature review

Membranous nephropathy (MN) is the commonest cause of nephrotic syndrome (NS) in adult male patients worldwide. Most of the cases (80%) are idiopathic (primary MN, PMN), whereas about 20% are associated with autoimmune diseases, malignancies or exposures (secondary MN). PMN is a kidney-specific autoimmune glomerular disease mediated by antibodies to the M-type phospholipase A2 receptor (anti-PLA2R) (85%), thrombospondin type 1 domain containing 7A (THSD7A) (3-5%), or by other still unidentified mechanisms (10%). Most of the patients with PMN present with NS (80%). Clinical course of PMN is characterised by spontaneous remissions (40%) and relapses (15-30%). One third develop end-stage renal disease (ESRD) within 5 to 15 years from the onset. Anti-PLA2R/THSD7A antibodies levels correlate with proteinuria, clinical course, and outcomes. The treatment still remains matter of debate. Hypertension, proteinuria, and hyperlipidaemia must be treated in all patients. Immunosuppressive therapy is indicated in patients with elevated anti-PLA2R/THSD7A levels and proteinuria >3.5 g/d at diagnosis. With proper management, only 10% or less will develop ESRD over the subsequent 10 years. Here we report a case of a 34-year-old male patient with a ten-year history of asymptomatic PMN, treated with ACE-inhibitors, who presented to our emergency room for acute chest pain and exertional dyspnoea due to ESRD that required urgent dialysis. (www.actabiomedica.it).

The diagnostic value of immunohistochemical staining of the interstitial vascular C4d complement in membranous nephropathy

Membranous glomerulonephritis (MGN) is the most common cause of adulthood nephrotic syndrome. Diagnosis of membranous nephritis is based on light electron immunofluorescence microscopy and clinical signs. Immune complex deposition against podocyte antigens such as phospholipase A2 receptor (PLA2R) activates the complement system. Of this, complement Component C4d (C4d) is involved in the classical and lectin pathways. This marker may be used by immunohistochemistry to diagnose MGN when other methods are not available. In this work, C4d expression was monitored by immunohistochemical analysis in the glomerular capillaries of patients with primary MGN (study group, N=33) versus patients with minimal change disease (MCD, control group, N=20) in a cross-sectional evaluation performed based on the diagnosis confirmed by light microscopy and immunofluorescence. There was no significant demographic difference between the two groups except for age (P=0.002). C4d immune-expression was positive in glomerular capillary (2+ to 4+) in most of the MGN patients, while it was negative in the MCD group. The sensitivity and specificity of C4d immunostaining were 95% and 100%, respectively. The Pearson correlation coefficient was 0.74 between C4d (immunohistochemistry) and immunoglobulins (IgG; immunofluorescence) and 0.65 between C4d (immunohistochemistry) and the C3 complement product (immunofluorescence). Immunohistochemical evaluation of C4d is, therefore, a sensitive and specific method that has a high correlation with IgG immunofluorescence.

Microhematuria Enhances the Risks of Relapse and Renal Progression in Primary Membranous Nephropathy

Objective: To determine whether there is an association between microhematuria and relapse or kidney disease progression in patients with primary membranous nephropathy (PMN). Methods: A cohort of 639 patients with biopsy-proven PMN from two centers was followed for a median of 40 months. The exposures were initial hematuria, time-averaged hematuria, and cumulative duration of hematuria. The outcomes were relapse and renal progression, which were defined by a 40% reduction in renal function or end-stage renal disease. Cox proportional hazards regression and competing risk analyses were performed to yield hazard ratios (HRs) and subdistribution hazard ratios (sHRs) with 95% confidence intervals (CIs). Sensitivity and interaction analyses were also performed. Results: After adjusting for confounders, a higher level of initial hematuria was associated with a 1.43 (95% CI, 1.15-1.78) greater hazard of relapse. Worsening hematuria remarkably increased the risk of short-term relapse (HR, 4.64; 3.29-6.54). Time-averaged hematuria (sHR, 1.35; 1.12-1.63) and cumulative duration of hematuria (sHR, 1.17; 1.02-1.34) were independent predictors of renal progression. Hematuria remission was related to a reduced risk of renal progression over time in patients with positive microhematuria (sHR, 0.63; 0.41-0.96). Conclusions: A higher level of initial hematuria was a remarkable predictor of relapse in patients with PMN, and the magnitude and persistence of microhematuria were independently associated with kidney disease progression.

Clinical Outcomes of Patients With Primary Membranous Nephropathy and Subnephrotic Proteinuria

Objectives: To update the information about the prognosis of patients with primary membranous nephropathy (MN) and subnephrotic proteinuria and identify the relevant predictors. Methods: In total, 474 cases of biopsy-proven primary MN with at least 18 months of follow-up were reviewed to determine the outcomes of the subgroup of patients that presented with subnephrotic proteinuria. Clinical data included initial proteinuria and microhematuria, defined as the average proteinuria/microhematuria of the first 6 months during the course. Outcomes included partial remission (PR), complete remission (CR), nephrotic proteinuria progression, and kidney function progression, defined as ≥50% loss of kidney function or end-stage kidney disease. Results: In total, 205 patients with primary MN and subnephrotic proteinuria at biopsy were eligible. During a median follow-up of 43 months, 200 (97.56%), 167 (81.46%), and 53 (25.85%) patients attained PR, CR, and nephrotic proteinuria progression, respectively. Only one patient (0.49%) progressed to the kidney function progression. By multivariate Cox hazards regression analyses, the initial proteinuria was identified as the independent predictor for PR, CR, and nephrotic proteinuria progression with adjusted hazard ratios (aHRs) of 0.67 (95% confidence interval, 0.56-0.80), 0.50 (95% CI, 0.40-0.63), and 2.97 (95% CI, 2.23-3.97), respectively. A higher level of initial microhematuria was also associated with an increased risk of nephrotic proteinuria progression. The corresponding aHR was 1.11 (95% CI, 1.05-1.17). Conclusion: Among patients with primary MN and subnephrotic proteinuria, although the overall prognosis is excellent, dynamic detection and effective management of proteinuria remain important. In addition, initial microhematuria may be another predictor of nephrotic proteinuria progression.

B Cells in Primary Membranous Nephropathy: Escape from Immune Tolerance and Implications for Patient Management

Membranous nephropathy (MN) is an important cause of nephrotic syndrome and chronic kidney disease (CKD) in adults. The pathogenic significance of B cells in MN is increasingly recognized, especially following the discovery of various autoantibodies that target specific podocytic antigens and the promising treatment responses seen with B cell depleting therapies. The presence of autoreactive B cells and autoantibodies that bind to antigens on podocyte surfaces are characteristic features of MN, and are the result of breaches in central and peripheral tolerance of B lymphocytes. These perturbations in B cell tolerance include altered B lymphocyte subsets, dysregulation of genes that govern immunoglobulin production, aberrant somatic hypermutation and co-stimulatory signalling, abnormal expression of B cell-related cytokines, and increased B cell infiltrates and organized tertiary lymphoid structures within the kidneys. An understanding of the role of B cell tolerance and homeostasis may have important implications for patient management in MN, as conventional immunosuppressive treatments and novel B cell-targeted therapies show distinct effects on proliferation, differentiation and reconstitution in different B cell subsets. Circulating B lymphocytes and related cytokines may serve as potential biomarkers for treatment selection, monitoring of therapeutic response and prediction of disease relapse. These recent advances in the understanding of B cell tolerance in MN have provided greater insight into its immunopathogenesis and potential novel strategies for disease monitoring and treatment.

Mycophenolate mofetil-induced peripheral neuropathy in the treatment of membranous glomerulonephropathy: A case report

Mycophenolate mofetil (MMF) as an immunosuppressive agent is widely used in the management of Membranous Glomerulonephropathy (MGN). In this report, we described a 66-year-old male MGN case treated with MMF and revealed acquired sensory-motor axonal polyneuropathy, which is rare and has not been reported before.

Excretion Patterns of Urinary Sediment and Supernatant Podocyte Biomarkers in Patients with CKD

Background

Podocyte depletion causes glomerulosclerosis, and persistent podocyte loss drives progression to ESKD. Urinary sediment podocin (u-sed Pod) mRNA excretion and urinary supernatant podocalyxin (u-sup PCX) protein have been used to monitor disease activity in glomerular diseases. However, the differences in these markers among pathologies have not been investigated. We examined the roles of these markers in kidney diseases.

Methods

From January 2013 to March 2016, early morning urine samples were collected from 12 healthy controls and 172 patients with kidney disease (n=15 patients with minor glomerular abnormality with mild proteinuria and/or microscopic hematuria, n=15 with minimal change nephrotic syndrome [MCNS], n=15 with membranous nephropathy [MN], n=60 with IgA nephropathy [IgAN], n=19 with crescentic GN [Cres GN], n=10 with lupus nephritis [LN], and n=38 with other kidney diseases). We examined u-sed Pod mRNA excretion, u-sup PCX protein, and the urinary protein-creatinine ratio (u-PCR).

Results

u-sed Pod mRNA excretion was significantly correlated with u-sup PCX protein (r=0.37, P<0.001). Both u-sed Pod mRNA excretion and u-sup PCX protein were significantly correlated with u-PCR (r=0.53, P<0.001 and r=0.35, P<0.001, respectively). Interestingly, u-sed Pod mRNA excretion was significantly increased in proliferative-type GN-including IgAN with extracapillary proliferative lesions, Cres GN, and LN class IV-and significantly correlated with the rate of crescent formation, whereas u-sup PCX protein was significantly increased only in those with MN and subepithelial dense deposit-type LN compared with controls.

Conclusions

Higher u-sed Pod mRNA excretion and u-sup PCX protein were associated with proliferative-type GN, indicating podocyte detachment and subepithelial dense deposit-type GN, respectively. The results suggest that u-sed Pod mRNA excretion and u-sup PCX protein have usefulness for the diagnosis and measurement of disease activity with regard to glomerular diseases.

Integrative analysis of miRNA-mRNA network in idiopathic membranous nephropathy by bioinformatics analysis

Background

Currently, several specific antigens, M-type receptor for secretory phospholipase A2(PLA2R1), thrombospondin type-1 domain-containing 7A(THSD7A), and neural epidermal growth factor-like 1 protein (NELL-1), are discovered associated with the onset of idiopathic membranous nephropathy (IMN). But the pathomechanisms of IMN still need to be further claried. Understanding the mechanisms of IMN is required to improve its diagnosis and treatment.

Methods

In this study, we constructed miRNA regulatory networks to investigate IMN development. Moreover, miRNAs and mRNAs that were differentially expressed between Idiopathic Membranous Nephropathy (IMN) patients and normal controls were examined using the GSE115857 dataset and our previous sequence study. DE miRNA target genes were determined based on the FUNRICH software, starBase, miRDB, and miRWalk, and an miRNA-mRNA network was designed using DE-mRNAs that were negatively correlated with DE-miRNAs. The miRNA-mRNA network contained 228 miRNA-mRNA pairs. Thereafter, we conducted KEGG pathway, GO functional annotation, immune-related gene screening, protein interaction networks, and potential hub gene analyses. Furthermore, 10 miRNAs and 10 genes were determined and preliminarily validated using the validation dataset from GEO. Finally, we identified which pair may offer more accurate diagnosis and therapeutic targets for IMN.

Results

Two miRNA-mRNA pairs, miR-155-5p-FOS and miR-146a-5p-BTG2, were differentially expressed in IMN, indicating that these genes may affect IMN through immune processes. These findings may offer more accurate diagnoses and therapeutic targets for IMN.

Evaluation of ultrastructural alterations of glomerular basement membrane and podocytes in glomeruli by low-vacuum scanning electron microscopy

Background

Low-vacuum scanning electron microscopy (LV-SEM) is applied to diagnostic renal pathology.

Methods

To demonstrate the usefulness of LV-SEM and to clarify the optimal conditions of pathology samples, we investigated the alterations of glomerular basement membrane (GBM) and podocytes in control and experimental active Heymann nephritis (AHN) rats by LV-SEM.

Results

On week 15 following induction of AHN, spike formation on GBM with diffuse deposition of IgG and C3 developed. Using LV-SEM, diffuse crater-like protrusions were clearly noted three-dimensionally (3D) on surface of GBM in the same specimens of light microscopy (LM) and immunofluorescence (IF) studies only after removal coverslips or further adding periodic acid-silver methenamine (PAM) staining. These 3D ultrastructural findings of GBM surface could be detected in PAM-stained specimens by LV-SEM, although true GBM surface findings could not be obtained in acellular glomeruli, because some subepithelial deposits remained on surface of GBM. Adequate thickness was 1.5–5 μm for 10% formalin-fixed paraffin-embedded (FFPE) and 5–10 μm for the unfixed frozen sections. The foot processes and their effacement of podocytes could be observed by LV-SEM using 10%FFPE specimens with platinum blue (Pt-blue) staining or double staining of PAM and Pt-blue. These findings were obtained more large areas in 2.5% glutaraldehyde-fixed paraffin-embedded (2.5%GFPE) specimens.

Conclusion

Our findings suggest that LV-SEM is a useful assessment tool for evaluating the alterations of GBM and podocytes in renal pathology using routine LM and IF specimens, as well as 2.5%GFPE specimens.

Spontaneous Remission of Thrombospondin Type-1 Domain-Containing-Associated Membranous Nephropathy

Membranous nephropathy often achieves spontaneous remission. However, there are scarce reports of spontaneous remission of thrombospondin type-1 domain-containing 7A (THSD7A)-associated membranous nephropathy. A 64-year-old female presented with nephrotic syndrome and edema of the lower extremities. We diagnosed membranous nephropathy by kidney biopsy and confirmed positive THSD7A on immunofluorescence using frozen sections; serum THSD7A antibodies were also detected. Thirty-four months after the initial diagnosis, she achieved a spontaneous complete remission without immunosuppressive therapy. With the complete remission, no serum THSD7A levels were detected. In this study, we describe serial examinations of kidney biopsies and serum THSD7A antibodies.

Analysis of Glomerular IgG Subclasses Switch in Idiopathic Membranous Nephropathy Classified by Glomerular Phospholipase A2 Receptor Antigen and Serum Antibody

Background

The role of IgG subclass in idiopathic membranous nephropathy (IMN) was unclarified. Recent study found IgG subtype switches from IgG1 to IgG4 in the early pathological stage in IMN. The profile of IgG subclass in phospholipase A2 receptor- (PLA2R-) related and PLA2R-unrelated IMN was unrevealed. Our study is aimed at testifying whether IgG subclass switch existed in PLA2R-related and PLA2R-unrelated IMN, respectively.

Methods

Our study retrospectively enrolled 157 Chinese patients with biopsy-confirmed IMN between September 2017 and November 2019. We measured glomerular PLA2R antigen and serum anti-PLA2R antibody to classify the patients into PLA2R-related (n = 132) and PLA2R-unrelated (n = 25) subgroup. We evaluated glomerular IgG subclass by immunofluorescence (IF) predominance. Our study defined IgG subclass deposition as predominant if the IF score was higher than the other three and ≥1 +, or as codominant if the IF intensity was equal to any other and ≥1 +. We explored the relationship between IF predominance of glomerular IgG subtype and electron microscopic (EM) stages of IMN.

Results

We did not find statistical difference of predominant or codominant rate (pre/co-rate) among EM stages in any subclass (P > 0.05). Pre/co-rate of IgG3 linearly associated with EM stage in total and PLA2R-related subgroup (P = 0.044, P = 0.013). PLA2R-related subgroup showed higher IgG4 intensity (2.1 ± 0.6 vs. 1.6 ± 0.7, P = 0.001) and pre/co-rate of IgG4 in stage 1 (97% vs. 57%, P = 0.015) than PLA2R-unrelated group. We found no difference of IgG subclass pre/co-rate in different EM stages or linear association between pre/co-rate of IgG1, IgG2, IgG4, and EM stages (P > 0.05).

Conclusions

Pre/co-rate of IgG3 declined with EM stage in total and PLA2R-related subgroup. We did not find IgG subclass switches from IgG1 to IgG4 in either IMN patients or subgroups.

Membranous nephropathy in a patient with pulmonary tuberculosis infection and lung adenocarcinoma: a case report

We report a case of membranous nephropathy (MN) in a patient with tuberculosis infection and lung adenocarcinoma. A 50-year-old Filipino woman underwent a renal biopsy for the evaluation of proteinuria and hematuria. Immunofluorescence analysis revealed positive staining of IgG in the glomerular basement membrane and mesangial matrices, while electron microscopy demonstrated the presence of sub-epithelial deposits, suggesting MN. To screen for secondary causes of MN, we conducted a computed tomography (CT) scan of the chest and abdomen, which revealed a ground-glass opacity in the middle lobe of the right lung and an enlarged paraaortic lymph node. A T-SPOT test was positive, suggesting the possibility of a latent tuberculosis infection, as she was asymptomatic. A follow-up chest CT scan showed persistent presence of the ground-glass opacities, suggesting a non-infectious cause. Video-assisted thoracoscopic resection of the middle right lobe and partial resection of the lower right lobe were performed because the possibility of lung cancer could not be excluded. Notably, pathological analysis of the lung revealed adenocarcinoma in the middle lobe and epithelioid granuloma in the lower lobe, suggesting an active tuberculosis infection. One month after surgery, anti-tuberculosis treatment was initiated. Thereafter, her proteinuria, which had increased to 6 g/gCre preoperatively, began to decrease. Five months after surgery, the patient achieved complete remission. The speed of remission suggests that tuberculosis likely played a primary role in the etiology of MN. Our case underscores the importance of screening tests for infections and malignancies in patients with MN, even if suggestive symptoms are absent.

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.

Informatics Analysis of Health Indicators and Pathological Manifestations of Foot-Process in Patients with Primary IgA Nephropathy

Objective: This paper focuses on the foot-process in renal biopsies of patients with lgA, and examines their correlation with baseline clinical indicators and pathological manifestations in patients with lgA. Method: A retrospective data of patients who performed renal biopsy proven IgA nephropathy was selected. The patients who reached the agreed standard were grouped based on the degree of foot-process. There were three groups (ABC Groups) (Du, Y. and Huang, C, 2009. The value of proteinuria and foot process fusion in the onset of prognosis of acute kidney disease. Chinese Journal of Integrated Traditional and Western Medicine, 10(1), pp.44-45): group A for patients with no obvious foot-process lesion; group B for patients with segmental foot-process; group C for patients with massive foot-process. The three groups were reviewed in the aspects of baseline clinical indicators and Oxford classification, so as to discover foot-process’ effect on patients with IgA nephropathy. Results: A total of 129 patients with IgA nephropathy were included in the study. Concerning about the clinical baseline indicators related to the degree of foot-process, the 24-hour proteinuria level at admission was statistically significant and positively correlated (r = 0.324, P = 0.000). The comparison between groups showed there was statistically significant difference between group C and group A and group B (P = 0.001, P = 0.035). According to the Oxford Classification, only the differences of mesangial hypercellularity (M) and segmental sclerosis/adhesion (S) were statistically significant (r = 0.239, P = 0.006; r = 0.257, P = 0.003) and were positively correlated. In terms of mesangial hypercellularity (M), the differences between group A and B, group A and C were statistically significant (P = 0.01, P = 0.003). The comparison between group B and group C showed statistical difference (P = −0.031) in segmental sclerosis/adhesion (S). Among the 76 patients with S0 revealed by the Oxford classification, there were 55 patients of glomerulosclerosis, which was positively correlated with the degree of foot process (r = 0.211, P = 0.016). The comparison between group A and group C showed statistical difference (P = 0.014). Conclusion: The severity foot-process was positively correlated with the level of proteinuria. Foot-process is positively related with mesangial hypercellularity, segmental sclerosis and glomerulosclerosis. With more severe the foot-process, there will be more serious mesangial hypercellularity and irreversible glomerular injury. Foot-process is positively correlated with Lee’s Pathological Grading.

The association between variants in PLA2R and HLA-DQA1 and renal outcomes in patients with primary membranous nephropathy in Western China

BACKGROUND

Both Genome-wide associations and our previous study have shown that single nucleotide polymorphisms (SNPs) of M-type phospholipase A2 receptor (PLA2R) and human leukocyte antigen complex class II HLA-DQα-chain 1 (HLA-DQA1) gene were identified to be associated with primary membranous nephropathy (PMN). However, whether these SNPs affect clinical manifestation and renal outcome for PMN patients is poorly defined. Here, we evaluated whether there is an association between these SNPs and clinical manifestations and renal outcomes of PMN in a western Chinese cohort.

METHODS

Seven SNPs within PLA2R and one SNP in HLA-DQA1 were selected in our study. Clinical data from 314 patients with PMN were collected and the relationship between the genotype and phenotype was evaluated. A total of 186 patients had follow-up data. We assessed the treatment responses and renal outcomes between patients with these gene polymorphisms after a median follow-up of 18.6 months.

RESULTS

Eight SNPs were not associated with clinical manifestations of PMN patients (Pc < 0.05). rs3828323 T allele was marginally significantly associated with hypertension (P = 0.008, Pc = 0.064, OR = 1.821). After treatment for PMN, the SR group (including CR and PR) had lower serum creatinine level (68.4 ± 18.8 μmol/L vs. 122.8 ± 126.6 μmol/L, P < 0.001), urea (5.5 ± 1.9 mmol/L vs. 8.0 ± 4.0 mmol/L, P < 0.001), uric acid (358.5 ± 95.1 μmol/L vs. 392.8 ± 118.1 μmol/L, P = 0.037) and urinary protein (0.23 (0.76,1.05) g/d vs. 3.01 (2.06,7.95) g/d, P < 0.001), higher eGFR (100.0 ± 20.1 ml/min/1.73m2 vs. 77.1 ± 35.3 ml/min/1.73m2, P < 0.001) and albumin (41.1 ± 5.1 g/L vs.30.4 ± 8.2 g/L, P < 0.001). We also identified that PMN patients with CT/TT genotype for rs3828323 achieved higher cumulative survival rate than patients with CC genotype.

CONCLUSIONS

Rs3828323 may influence hypertension and renal outcome in patients with PMN. Further research is needed to explore the mechanism for this genotype-disease phenotype association.

Effectiveness and safety of cyclophosphamide or tacrolimus therapy for idiopathic membranous nephropathy

BACKGROUND

Guidelines recommend classical combined therapy of steroid and cyclophosphamide (CYC) for patients with idiopathic membranous nephropathy (IMN), while it is associated with severe adverse effects.

AIMS

We conducted an observational and retrospective study to evaluate the effectiveness and safety of steroids plus tacrolimus (TAC) versus steroids plus CYC for IMN.

METHODS

A total of 203 kidney-biopsy-proven IMN patients was enrolled in this study. One group (n = 142) received steroid combined with intravenous CYC (750 mg/m² body surface) and the other group (n = 61) received steroid combined with oral TAC (target blood concentration of 4-8 ng/mL). The primary outcomes were achievement of remission. The secondary end-points included incidence of adverse events, relapse rates, 24 h urinary protein (UP), serum albumin, serum creatinine and estimated glomerular filtration rate.

RESULTS

Over the 18-month observation period, the study suggested that the remission rates at the first 3 months were significantly higher in TAC group than in CYC group (72.1% vs 54.9%, P < 0.05). Although the cumulative incidence of serious and non-serious adverse events was not different significantly between the two groups, the incidence after first 3 months was lower in TAC group. Levels of 24-h UP and serum albumin improved in the TAC group more than in the CYC group (P < 0.05) over the observed period.

CONCLUSIONS

Because of its short-term effectiveness and long-term safety profile, steroid plus TAC might be a better option for IMN.

Electron-Dense Deposition Patterns and the Outcomes of Nephrotic Idiopathic Membranous Nephropathy Treated with Tacrolimus in Chinese Adults

Background

Tacrolimus may be effective in the short-term treatment of idiopathic membranous nephropathy (IMN). However, it is not clear whether an electron microscopic classification of the homogeneous and heterogeneous types of nephrotic IMN is related to the efficacy of tacrolimus in patients with IMN. This study aimed to explore this question and to provide evidence for individualized patient treatment.

Material/Methods

This 6-month retrospective study included 61 Chinese patients previously diagnosed with IMN. Patients received treatment was tacrolimus plus glucocorticoid. The patients were divided into a homogeneous group and a heterogeneous group based on the evaluation of electron-dense deposits. The initial clinicopathologic factors in the 2 groups were analyzed, and the difference in efficacy of tacrolimus in the 2 groups was assessed. The factors predicting remission were also studied.

Results

No significant alteration in the initial clinicopathologic status was found between the 2 groups, except for proteinuria, serum albumin levels, systolic blood pressure, and renal biopsy results (stages I/II/III/IV). After 3 months of treatment, the difference in remission was not significant between the 2 groups. However, after 6 months of treatment, a significant difference in remission rates was observed between the 2 groups. The binary logistic model showed that the homogeneous nephrotic IMN was independently associated with total remission (partial plus complete remission), and was also related to complete remission.

Conclusions

The results of our study revealed that the homogeneous type of nephrotic IMN had a higher short-term remission rate and a predictive value for partial or complete remission, and it might be a meaningful marker of the short-term response to tacrolimus.

Mechanisms of Primary Membranous Nephropathy

Membranous nephropathy (MN) is an autoimmune disease of the kidney glomerulus and one of the leading causes of nephrotic syndrome. The disease exhibits heterogenous outcomes with approximately 30% of cases progressing to end-stage renal disease. 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. Approximately 50–80% and 3–5% of primary MN (PMN) cases are associated with either anti-PLA2R or anti-THSD7A antibodies, respectively. The presence of these autoantibodies is used for MN diagnosis; antibody levels correlate with disease severity and possess significant biomarker values in monitoring disease progression and treatment response. Importantly, both autoantibodies are causative to MN. Additionally, evidence is emerging that NELL-1 is associated with 5–10% of PMN cases that are PLA2R- and THSD7A-negative, which moves us one step closer to mapping out the full spectrum of PMN antigens. Recent developments suggest exostosin 1 (EXT1), EXT2, NELL-1, and contactin 1 (CNTN1) are associated with MN. Genetic factors and other mechanisms are in place to regulate these factors and may contribute to MN pathogenesis. This review will discuss recent developments over the past 5 years.

Autoantibodies in the Diagnosis, Monitoring, and Treatment of Membranous Nephropathy

The discovery of anti-podocyte antibodies in primary membranous nephropathy (MN) has revolutionized our approach toward the diagnosis and treatment of this disease. Evaluation of serum levels of anti-podocyte antibodies paved the way for non-invasive diagnosis and helped distinguish between primary and secondary MN although the relationship between anti-podocyte antibodies and cancer remains to be elucidated. Serum levels of anti-PLA2R antibodies directed against the major podocyte autoantigen are related to MN activity and the decrease in serum levels of anti-PLA2R antibodies in response to treatment (immunologic remission) also serves as an early indicator of the later putative proteinuric remission, enabling personalization of the treatment. The serum levels of anti-podocyte antibodies also enable the prediction of renal outcomes in terms of both remission and the risk of progression to end-stage renal disease. The positivity of anti-PLA2R antibodies before renal transplantation is associated with the risk of recurrence of MN. It remains to be established if all these relations observed in patients with anti-PLA2R antibodies are also valid for expanding spectrum of antibodies directed against recently discovered minor antigens (e.g., THSD7A, NELL-1, semaphorin 3B).

Nephrotic syndrome secondary to alpha-1 antitrypsin deficiency

We report a 64-year-old caucasian woman diagnosed with membranous nephropathy secondary to alpha-1 antitrypsin deficiency (AATD). AATD is a rare autosomal codominant genetic disorder. Its clinical manifestations are mostly observed in the lungs, with early-onset emphysema. Nephropathy due to AATD is still very rare and only a few cohort studies have been reported. It has been recognised that alpha-1 antitrypsin has a protective role in the kidneys which enhances the possibility of development of kidney failure, such as nephrotic syndrome, in cases of AATD. Further clinical investigation is needed to understand the relationship between the development of nephropathy, namely membranous nephropathy, and AATD.

Altered glycosylation of IgG4 promotes lectin complement pathway activation in anti-PLA2R1-associated membranous nephropathy

Primary membranous nephropathy (pMN) is a leading cause of nephrotic syndrome in adults. In most cases, this autoimmune kidney disease is associated with autoantibodies against the M-type phospholipase A2 receptor (PLA2R1) expressed on kidney podocytes, but the mechanisms leading to glomerular damage remain elusive. Here, we developed a cell culture model using human podocytes and found that anti-PLA2R1-positive pMN patient sera or isolated IgG4, but not IgG4-depleted sera, induced proteolysis of the 2 essential podocyte proteins synaptopodin and NEPH1 in the presence of complement, resulting in perturbations of the podocyte cytoskeleton. Specific blockade of the lectin pathway prevented degradation of synaptopodin and NEPH1. Anti-PLA2R1 IgG4 directly bound mannose-binding lectin in a glycosylation-dependent manner. In a cohort of pMN patients, we identified increased levels of galactose-deficient IgG4, which correlated with anti-PLA2R1 titers and podocyte damage induced by patient sera. Assembly of the terminal C5b-9 complement complex and activation of the complement receptors C3aR1 or C5aR1 were required to induce proteolysis of synaptopodin and NEPH1 by 2 distinct proteolytic pathways mediated by cysteine and aspartic proteinases, respectively. Together, these results demonstrated a mechanism by which aberrantly glycosylated IgG4 activated the lectin pathway and induced podocyte injury in primary membranous nephropathy.