Thrombospondin type-1 domain-containing 7A in idiopathic membranous nephropathy

Response to immunosuppressive therapy in PLA2R- associated and non-PLA2R- associated idiopathic membranous nephropathy: a retrospective, multicenter cohort study

Background

According to renal M type phospholipase A₂ receptor (PLA₂R) immunohistochemistry, idiopathic membranous nephropathy (IMN) could be categorized into PLA₂R-associated and non-PLA₂R-associated IMN. We conducted a retrospective, multicenter cohort study with 91 patients to compare the effect of immunosuppressive therapy between PLA₂R-associated and non-PLA₂R-associated IMN patients.

Methods

A total of 91 biopsy-proven IMN patients from Huashan hospital and People’s Hospital of Wuxi in past 5 years were collected into this study. IMN with positive PLA₂R immunohistochemistry in kidney biopsies were designated as PLA₂R-associated IMN. Seventy-eight of the 91 IMN patients was PLA₂R-associated IMN and 13 were non-PLA₂R-associated IMN. Forty-five patients were treated with prednisone plus cyclophosphamide (CTX), and 46 with prednisone plus calcineurin inhibitors (CNIs). The follow-up duration was 15 months.

Results

The total remission rate (76.9% versus 44.9%, p = 0.032) and complete remission rate (30.8% versus 2.6%, p = 0.003) were both significantly higher in the non-PLA₂R-associated group than in the PLA₂R-associated group at the 3rd month visit point, and at the 6th month time point, the complete remission rate was still significantly higher in the non-PLA₂R-associated group (46.2% versus 11.5%,p = 0.007). But similar remission rates were found after the 9th month. Relapses were observed in 8 patients in PLA₂R-associated group and none in non-PLA₂R-associated group, although there was no significant difference between these two groups.

Conclusion

Compared with the PLA₂R-associated IMN, the non-PLA₂R-associated IMN responded quicker to the immunosuppressive therapy.

Treatment of membranous nephropathy: time for a paradigm shift

In patients with membranous nephropathy, alkylating agents (cyclophosphamide or chlorambucil) alone or in combination with steroids achieve remission of nephrotic syndrome more effectively than conservative treatment or steroids alone, but can cause myelotoxicity, infections, and cancer. Calcineurin inhibitors can improve proteinuria, but are nephrotoxic. Most patients relapse after treatment withdrawal and can become treatment dependent, which increases the risk of nephrotoxicity. The discovery of nephritogenic autoantibodies against podocyte M-type phospholipase A2 receptor (PLA₂R) and thrombospondin type-1 domain- containing protein 7A (THSD7A) antigens provides a clear pathophysiological rationale for interventions that specifically target B-cell lineages to prevent antibody production and subepithelial deposition. The anti-CD20 monoclonal antibody rituximab is safe and achieves remission of proteinuria in approximately two-thirds of patients with membranous nephropathy. In those with PLA₂R-related disease, remission can be predicted by anti-PLA₂R antibody depletion and relapse by antibody re-emergence into the circulation. Thus, integrated evaluation of serology and proteinuria could guide identification of affected patients and treatment with individually tailored protocols. Nonspecific and toxic immunosuppressive regimens will fall out of use. B-cell modulation by rituximab and second-generation anti-CD20 antibodies (or plasma cell-targeted therapy in anti-CD20 resistant forms of disease) will lead to a novel therapeutic paradigm for patients with membranous nephropathy.

PLA2R and THSD7A: Disparate Paths to the Same Disease?

The phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A) are the two major autoantigens in primary membranous nephropathy (MN), and define two molecular subclasses of this disease. Both proteins are large transmembrane glycoproteins expressed by the podocyte, and both induce IgG4-predominant humoral immune responses that produce circulating autoantibodies that can be used clinically for diagnostic and monitoring purposes. The biologic roles of these proteins remain speculative, although several features of THSD7A suggest a role in adhesion. PLA2R-associated MN was initially found to associate with risk alleles within HLA-DQA1, but subsequent studies have shifted the focus to the HLA-DRB locus. Three distinct humoral epitope-containing regions have been defined within the extracellular portion of PLA2R, and it appears that the number of targeted epitopes may determine disease severity. Although similar information is not yet available for THSD7A-associated MN, this form of MN may have a unique association with malignancy. Finally, it appears likely that other autoantigens in primary MN exist. Although protocols similar to those that identified PLA2R and THSD7A may be successful in the identification of novel antigenic targets in MN, newer techniques such as laser-capture mass spectrometry or protein arrays may be helpful as well.

A podocyte view of membranous nephropathy: from Heymann nephritis to the childhood human disease

Membranous nephropathy (MN) is characterized by an accumulation of immune deposits on the subepithelial side of the glomerular basement membrane, which results in complement activation and proteinuria. Since 2002, several major antigens of the podocyte have been identified in human MN, the first one being neutral endopeptidase (NEP), the alloantigen involved in neonatal cases of MN that occur in newborns from NEP-deficient mothers. This discovery opened the field to the major advances that have occurred since then in the pathophysiology and treatment of MN. It is remarkable that experimental models such as Heymann nephritis and cationic bovine serum albumin-induced MN in the rabbit predicted the pathomechanisms of the human glomerulopathy. The podocyte is at the center of the pathogenesis of MN either by providing a source of endogenous antigens or by creating an environment favorable to deposition and accumulation of immune complexes containing exogenous (non-podocyte) antigens. The podocyte is also a victim of complement activation and antibody blocking activity against enzymes or receptors. A search for innovative drugs aimed at protecting this cell against complement activation and the effects of prolonged ER stress has become a priority.

Primary Membranous Nephropathy

Membranous nephropathy (MN) is a unique glomerular lesion that is the most common cause of idiopathic nephrotic syndrome in nondiabetic white adults. About 80% of cases are renal limited (primary MN, PMN) and 20% are associated with other systemic diseases or exposures (secondary MN). This review focuses only on PMN. Most cases of PMN have circulating IgG4 autoantibody to the podocyte membrane antigen PLA2R (70%), biopsy evidence PLA2R staining indicating recent immunologic disease activity despite negative serum antibody levels (15%), or serum anti-THSD7A (3%-5%). The remaining 10% without demonstrable anti-PLA2R/THSd7A antibody or antigen likely have PMN probably secondary to a different, still unidentified, anti-podocyte antibody. Considerable clinical and experimental data now suggests these antibodies are pathogenic. Clinically, 80% of patients with PMN present with nephrotic syndrome and 20% with non-nephrotic proteinuria. Untreated, about one third undergo spontaneous remission, especially those with absent or low anti-PLA2R levels, one-third progress to ESRD over 10 years, and the remainder develop nonprogressive CKD. Proteinuria can persist for months after circulating anti-PLA2R/THSD7A antibody is no longer detectable (immunologic remission). All patients with PMN should be treated with supportive care from the time of diagnosis to minimize protein excretion. Patients with elevated anti-PLA2R/THSD7A levels and proteinuria >3.5 g/d at diagnosis, and those who fail to reduce proteinuria to <3.5 g after 6 months of supportive care or have complications of nephrotic syndrome, should be considered for immunosuppressive therapy. Accepted regimens include steroids/cyclophosphamide, calcineurin inhibitors, and B cell depletion. With proper management, only 10% or less will develop ESRD over the subsequent 10 years.

[Membranous nephropathy: New insights in therapeutic approach]

Membranous nephropathy is one of the leading causes of nephrotic syndrome in adults, evolving to 30 % end-stage renal disease after 10 years, in the absence of specific treatment. In 2009, the M-type phospholipase A2 receptor (PLA2R), a podocyte membrane glycoprotein, was identified as the first autoantigen involved in more than 70 % of primitive membranous nephropathy. Many studies have reported that high titers of PLA2R antibodies are correlated with a lower risk of spontaneous or immunosuppressant-induced remission, a higher risk of nephrotic syndrome and of progression to end-stage renal disease. Treatment is still challenging and controversial because of potential toxicity and lack of a reliable prognosis marker. In the past, the 2012 Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guidelines recommended immunosuppressive therapies as steroids and alkylating agents or cyclosporine in patients with persistent nephrotic syndrome or impaired renal function. Recent studies and one multicentric randomised controlled trial brought clear evidence to support the use of rituximab in these patients: rituximab regimen induces immunological and clinical remission in patients with membranous nephropathy, with a high safety profile. However, they have provided important data on the impact of PLA2R antibodies assessment as a prognostic biomarker in patients with membranous nephropathy. The next step will be the integration of this biomarker in KDIGO guidelines and the recommendation of rituximab as a first line immunosuppressive therapy in patient with persistent nephrotic syndrome due to membranous nephropathy.

Serum anti-PLA2R antibody and glomerular PLA2R deposition in Chinese patients with membranous nephropathy: A cross-sectional study

M-type phospholipase A2 receptor (PLA2R) is the major target antigen in primary membranous nephropathy (PMN). Previous studies have evaluated the diagnostic value of serum anti-PLA2R antibody. However, the correlation of serum anti-PLA2R antibody and glomerular PLA2R deposition, and their association with clinical characteristics need to be further evaluated.A total of 136 patients were involved as inception group because serum anti-PLA2R antibody and glomerular PLA2R antigen were simultaneously measured. We examined serum anti-PLA2R antibody by ELISA and glomerular PLA2R deposition by immunofluorescence assay.Positive serum anti-PLA2R antibody and glomerular PLA2R deposition were seen in 58.8% (80/136) and 95.6% (130/136) patients, respectively (P < .001). Proteinuria, serum total protein, serum albumin, serum creatinine, and estimated glomerular filtration rate (eGFR) had significant differences between patients with serum anti-PLA2R antibody and those without. Serum anti-PLA2R antibody levels were correlated with serum albumin, serum creatinine, eGFR, and proteinuria. Glomerular PLA2R deposition intensities were weakly correlated with proteinuria. Unexpectedly, there was a positive correlation rather than a negative correlation between glomerular PLA2R deposition intensity and eGFR.In conclusion, serum anti-PLA2R antibody is more closely correlated with disease activity and renal function than glomerular PLA2R deposition.

Membranous nephropathy-one morphologic pattern with different diseases

Since the discovery of the phospholipase A₂ receptor 1 (PLA₂R1) and thrombospondin type-1 domain-containing 7A (THSD7A) as endogenous antigens involved in the development of membranous nephropathy (MN) in over 80% of adult patients, substantial progress in the diagnosis, prognosis, and therapy of MN has been made. In most cases of patients with MN, it is now possible to specifically define the responsible pathogenic mechanisms of disease and make a diagnosis even without a renal biopsy. Moreover, the presence of antibodies in the blood and the detection of the antigens in renal biopsies allow the definite diagnosis without the morphologic uncertainties, which now still apply for only about 20% of all renal biopsies showing MN. The discovery that the expression of THSD7A in malignant tumors might serve as the site of primary antigen recognition for the immune system to start MN might lead to a better understanding of not only tumor-associated MN, which accounts for up to 10% of all patients with MN, but also of the pathomechanisms relevant for MN development in general.

Recent Treatment Advances and New Trials in Adult Nephrotic Syndrome

The etiology of nephrotic syndrome is complex and ranges from primary glomerulonephritis to secondary forms. Patients with nephrotic syndrome often need immunosuppressive treatment with its side effects and may progress to end stage renal disease. This review focuses on recent advances in the treatment of primary causes of nephrotic syndrome (idiopathic membranous nephropathy (iMN), minimal change disease (MCD), and focal segmental glomerulosclerosis (FSGS)) since the publication of the KDIGO guidelines in 2012. Current treatment recommendations are mostly based on randomized controlled trials (RCTs) in children, small RCTs, or case series in adults. Recently, only a few new RCTs have been published, such as the Gemritux trial evaluating rituximab treatment versus supportive antiproteinuric and antihypertensive therapy in iMN. Many RCTs are ongoing for iMN, MCD, and FSGS that will provide further information on the effectiveness of different treatment options for the causative disease. In addition to reviewing recent clinical studies, we provide insight into potential new targets for the treatment of nephrotic syndrome from recent basic science publications.

Detection and monitoring PLA2R autoantibodies by LIPS in membranous nephropathy

Autoantibodies against the M-type phospholipase A2 receptor (PLA2R) are specific markers for primary membranous nephropathy (MN). Quantification of PLA2R autoantibodies is an important, noninvasive tool that facilitates the diagnosis and monitoring of primary MN. In this report we describe a highly quantitative luciferase immunoprecipitation systems (LIPS) assay for detecting PLA2R autoantibodies. For these studies, a cDNA fragment encoding the first 858 amino acids of PLA2R protein was cloned to generate N-terminal antigen fusion constructs with Gaussia luciferase (Gluc) and Nano luciferase (NanoLuc) reporters. Following transfection, crude cell extracts containing the recombinant PLA2R-luciferase fusion proteins were tested by LIPS on healthy controls, subjects with other kidney disease and subjects with MN. LIPS testing with both reporters detected robust PLA2R autoantibody levels in a subset of patients with primary MN and demonstrated 100% sensitivity compared to ELISA and/or Western blotting. The PLA2R-NanoLuc LIPS assay demonstrated 100% specificity matching the ELISA, but the specificity of the PLA2R-Gluc LIPS assays was slightly lower (97%). Further analysis revealed that autoantibody levels determined by PLA2R-NanoLuc LIPS correlated well with urinary protein excretion (R=0.79) and disease activity and was very sensitive for detecting clinical relapse. These results highlight the potential utility of the LIPS PLA2R-NanoLuc assay for diagnosis and management of MN.

New Insights into Podocyte Biology in Glomerular Health and Disease

Podocyte and glomerular research is center stage for the development of improved preventive and therapeutic strategies for chronic progressive kidney diseases. Held April 3-6, 2016, the 11th International Podocyte Conference took place in Haifa and Jerusalem, Israel, where participants from all over the world presented their work on new developments in podocyte research. In this review, we briefly highlight the advances made in characterizing the mechanisms involved in podocyte development, metabolism, acquired injury, and repair, including progress in determining the roles of genetic variants and microRNA in particular, as well as the advances made in diagnostic techniques and therapeutics.

Expression, prognosis and functional role of Thsd7a in esophageal squamous cell carcinoma of Kazakh patients, Xinjiang

Thsd7a (Thrombospondin type 1 domain containing 7a) is a critical transmembrane protein. Studies have indicated that Thsd7a was associated with cytoskeletal organization, cell migration and filopodia formation. However, the involvement of Thsd7a remains elusive in human Esophageal Squamous Cell Carcinoma (ESCC). Consequently, immunohistochemistry and reverse transcription-polymerase chain reaction were utilized to study the correlation between the expression of Thsd7a and clinical-pathological characteristics. The influence of Thsd7a on apoptosis, cell proliferating activity, cell cycle, migratory and invasive capacity was determined in Eca 109 and EC 9706 cell lines in vitro. And the influence on proliferating activity was testified using naked mice model in vivo. In addition, the potential molecular mechanism was tested by microarray. It was discovered that there is a certain correlation between Thsd7a and the Kazakh ESCC. By knocking out Thsd7a, the invasion, migration and proliferation could be decreased. And it could also arrest the cell cycle at G1 phase and increase the apoptosis rate. It was further verified that Thsd7a had obvious effect on proliferation in naked mice with xenograft of Eca109 cells. Finally, it was uncovered by microarray analysis that a variety of tumor genes and pathways related to Thsd7a. Together, it was demonstrated that Thsd7a might have a certain degree of carcinogenesis in ESCC.

Chronic Fibro-Inflammatory Responses in Autoimmune Pancreatitis Depend on IFN-α and IL-33 Produced by Plasmacytoid Dendritic Cells

In previous studies, we found that human IgG4-related autoimmune pancreatitis (AIP) and murine AIP are driven by activation of plasmacytoid dendritic cells (pDCs) producing IFN-α. In the present studies we examined additional roles of pDC-related mechanisms in AIP pathogenesis, particularly those responsible for induction of fibrosis. We found that in murine AIP (MRL/Mp mice treated with polyinosinic-polycytidylic acid) not only the pancreatic infiltration of immune cells but also the development of fibrosis were markedly reduced by the depletion of pDCs or blockade of type I IFN signaling; moreover, such treatment was accompanied by a marked reduction of pancreatic expression of IL-33. Conversely, polyinosinic-polycytidylic acid-induced inflamed pancreatic tissue in murine AIP exhibited increased expression of type I IFNs and IL-33 (and downstream IL-33 cytokines such as IL-13 and TGF-β1). pDCs stimulated by type I IFN were the source of the IL-33 because purified populations of these cells isolated from the inflamed pancreas produced a large amount of IL-33 upon activation by TLR9 ligands, and such production was abrogated by the neutralization of type I IFN. The role of IL-33 in murine AIP pathogenesis was surprisingly important because blockade of IL-33 signaling by anti-ST2 Ab attenuated both pancreatic inflammation and accompanying fibrosis. Finally, whereas patients with both conventional pancreatitis and IgG4-related AIP exhibited increased numbers of acinar cells expressing IL-33, only the latter also exhibited pDCs producing this cytokine. These data thus suggest that pDCs producing IFN-α and IL-33 play a pivotal role in the chronic fibro-inflammatory responses underlying murine AIP and human IgG4-related AIP.

Out of Africa: Complete and partial remissions as a combined outcome in patients with idiopathic membranous glomerulonephritis in Cape Town

AIM

Remission outcomes among patients with idiopathic membranous glomerulonephritis is unknown in Africa. We sought to determine remission outcomes in a cohort of South African adult patients with IMGN.

METHODS

This was a retrospective review of patients with biopsy-proven IMGN over a 10 year period. Secondary causes of MN were excluded. Demographic, clinical, biochemical and histological records were retrieved for analysis. The trends in biochemical parameters from baseline were determined. The primary outcome was the attainment of a complete or partial remission (CR / PR) at the last follow-up.

RESULTS

Fifty-six patients met the criteria for inclusion and 43 had subsequent follow-up care with a median duration of follow-up of 23.0 (13.0-48.0) months. Sixteen patients (37.2%) were treated with immunosuppression (corticosteroids and cyclophosphamide) and 81.4% received anti-proteinuric agents. There were no significant differences in demographic and clinical features of patients categorized by immunosuppression (ISP) use. Changes in level of proteinuria and estimated glomerular filtration rate (eGFR) were also not significantly different between the two groups. Eighteen patients (41.9%) reached CR or PR at the last visit. The median times-to-remission of patients according to ISP status were similar at 48.6 and 48.7 months respectively (P = 0.104) while the proportions of patients not reaching CR/PR at 12 and 24 months were 94.6% and 80.8% respectively. Gender and race did not predict remission status (P > 0.05). Predictors of CR/PR at last visit were eGFR [OR 1.01 (95%CI: 1.00 - 1.02); P = 0.041], and systolic BP (OR 0.97 [95%CI: 0.95 - 0.99); P = 0.036].

CONCLUSION

Remission outcomes in this African IMGN cohort are delayed and poor.

Prognostic value of PLA2R autoimmunity detected by measurement of anti-PLA2R antibodies combined with detection of PLA2R antigen in membranous nephropathy: A single-centre study over 14 years

Introduction

Clinical course of membranous nephropathy (MN) is difficult to predict. Measurement of circulating anti-PLA2R autoantibodies (PLA2R-Ab) and detection in immune deposits of PLA2R antigen (PLA2R-Ag) are major advances in disease understanding. We evaluated the clinical significance of these biomarkers.

Methods

In this 14-year retrospective study, we collected data from 108 MN patients and assessed the relationship between clinical course, PLA2R-Ab and PLA2R-Ag. We also assessed THSD7A status.

Results

Eighty-five patients suffered from primary MN (PMN) and 23 patients from a secondary form. The median follow-up was 30.4 months [interquartile range, 17.7;56.7]. Among the 77 patients with PMN and available serum and/or biopsy, 69 (89.6%) had PLA2R-related disease as shown by anti-PLA2R-Ab and/or PLA2R-Ag, while 8 patients (8/77, 10.4%) were negative for both. There was no significant difference between these two groups in age at diagnosis and outcome assessed by proteinuria, serum albumin level and eGFR. Two of the 8 negative patients were positive for THSD7A. In patients with PLA2R related PMN, younger age, lower proteinuria, higher eGFR, and lower PLA2R-Ab level at baseline and after 6 months were associated with remission of proteinuria. Initial PLA2R-Ab titer ≤ 97.6 RU/mL and complete depletion of PLA2R-Ab within 6-months were significantly associated with spontaneous remission at the end of follow-up. In rituximab treated patients, lower PLA2R-Ab titer at initiation of treatment, and absence of PLA2R-Ab and higher serum albumin level at 3 months were significantly associated with remission. Noticeably, 81.8% of the patients who achieved remission completely cleared PLA2R-Ab. Depletion of PLA2R-Ab and increase of serum albumin level preceded the decrease of proteinuria.

Conclusion

Assessment of PLA2R autoimmunity is essential for patient management. Combination of PLA2R-Ab and PLA2R-Ag increases diagnosis sensitivity. PLA2R-Ab titer is a biomarker of disease severity at initial assessment, and the kinetics of the antibody are significantly correlated to disease evolution.

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

Background: The diagnostic role of circulating anti-phospholipase A2 receptor antibodies (anti-PLA2R Abs) is now well recognized in idiopathic membranous nephropathy (iMN). These Abs could also be interesting as predictors of clinical outcome. In this study, we explored the prognostic value of anti-PLA2R Abs measured in a cohort of iMN patients, with a special focus on their ability to detect patients achieving spontaneous remission.

Methods: All adult patients with biopsy-proven iMN diagnosed between 1978 and 2007 were retrospectively screened in our centre. Using a validated enzyme-linked immunosorbent assay, levels of anti-PLA2R Abs were measured from serum samples obtained at the time of renal biopsy and stored at −80°C until processing. Clinical data on disease activity, treatments and outcomes were collected by reviewing patients’ medical records. The association between anti-PLA2R Ab titres and clinical activity/outcome was assessed by Cox proportional hazard and Kaplan–Meier methods.

Results: In this retrospective study, 68 patients were included in the final analysis (median follow-up of 81 months). No significant association was found between anti-PLA2R Ab titres at diagnosis with baseline proteinuria, baseline estimated glomerular filtration rate or chronic kidney disease progression. Spontaneous remission was observed in 22% of patients. Ab titres were significantly and gradually correlated in a dose–response manner with the likelihood of spontaneous remission.

Conclusions: While Ab titres measured at diagnosis were not found to predict the activity of iMN, evaluation of anti-PLA2R Ab titres might prove useful in the early identification of patients likely to achieve spontaneous remission.

Early initiation of immunosuppressive treatment in membranous nephropathy patients

BACKGROUND/PURPOSE

Suggestion for the management of idiopathic membranous nephropathy (IMN) includes 6 months of observation, followed with steroid plus alkylating agent. However, delayed immunosuppression exposes the kidneys to persistent damage. This study aimed to examine the benefit of early immunosuppression in IMN patients.

METHODS

A retrospective study was performed. From 1993 to 2013, 161 IMN patients were enrolled. Patients receiving immunosuppression within 6 months after diagnosis were classified as initial-treatment group, whereas other patients as initial-no-treatment group. The clinical outcomes and complication were examined.

RESULT

Patients in the initial-treatment group had lower serum albumin concentration, less diabetes, and were younger. Steroid monotherapy is the main immunosuppression (64.5%) in this group. The initial-treatment group had a higher complete and partial remission rate than the initial-no-treatment group 6 months (52.9% vs. 35.0%, p=0.05) and 12 months (71.1% vs. 45.0%, p=0.003) after diagnosis. A similar result was seen between initial-steroid monotherapy and initial-no-treatment patients. Early immunosuppression is an independent predictor of remission within 1 year [hazard ratio (HR)=2.09; 95% confidence interval (CI)=1.25-3.49; p=0.005] and estimated glomerular filtration rate (eGFR) decline over 50% during the follow-up. (HR=0.33; 95% CI=0.13-0.86; p=0.02). The initial-treatment group also had a low frequency of eGFR decline over 50% (p=0.001) and low combined end-stage renal disease/mortality (p=0.001) compared with the initial-no-treatment group, but without more immunosuppression-related complication.

CONCLUSION

In contrast to Western countries, early immunosuppression (even steroid monotherapy) in our patients is associated with better remission in the 1^st year and renal preserve. Further randomized controlled trials are needed to clarify the benefit of early immunosuppression in IMN patients, especially with oriental ethnic background.

Immunohistochemical Glomerular Expression of Phospholipase A2 Receptor in Primary and Secondary Membranous Nephropathy: A Retrospective Study in an Indian Cohort with Clinicopathological Correlations

Background

Limited published literature exists on the utility and standardization of anti-phospholipase A2 receptor (anti-PLA2R) immunohistochemistry (IHC) for the diagnosis of primary membranous nephropathy (MN). The study aimed to validate anti-PLA2R IHC for the diagnosis of primary MN and clinicopathological correlations in an Indian cohort.

Methods

Subjects included patients with primary and secondary MN diagnosed between January 2012 and August 2014 with an adequate renal biopsy and at least 1 year of clinical follow-up. Anti-PLA2R IHC was performed in all cases with miscellaneous renal lesions as controls. Electron microscopy was performed in selected cases. Sensitivity and specificity of anti-PLA2R IHC to identify primary MN was evaluated. Histopathological analyses of primary and secondary MN were done with clinicopathological correlations including serum creatinine, eGFR, chronic kidney disease stage, 24-h urine protein, serum cholesterol, serum albumin, and hypertension at presentation and follow-up, using the Kruskal-Wallis test and Spearman rank correlation. A p value of ≤0.05 was considered statistically significant.

Results

In 153 MN patients (99 primary, 54 secondary) and 37 miscellaneous controls, anti-PLA2R IHC differentiated primary from secondary MN with a sensitivity of 70.2% and a specificity of 96.6%. Secondary MN had increased mesangial matrix expansion compared to primary MN (p = 0.001). Severe nephrotic syndrome, impaired renal function, and hypertension were all more common in primary than in secondary MN.

Conclusion

Anti-PLA2R IHC is a specific marker to distinguish primary MN from secondary MN.

THSD7A expression in human cancer

We recently described a case of a Thrombospondin Type-1 Domain containing 7A (THSD7A) associated membranous nephropathy in a female patient who was synchronously suffering from a THSD7A-positive malignancy. We here investigated the role of THSD7A as a new potential tumor antigen by evaluating over 20 000 tissue spots in more than 70 different tumor entities by immunohistochemistry using tissue microarrays. THSD7A expression was highly variable in different neoplasias with differing staining patterns. Both gain and loss of THSD7A expression compared to expression status in non-tumor tissue were linked to tumor-specific markers in the different tumor entities and were of prognostic value. The potential role of THSD7A in tumor development and therapy needs further investigation.

A Proposal for a Serology-Based Approach to Membranous Nephropathy

Primary membranous nephropathy (MN) is an autoimmune disease mainly caused by autoantibodies against the recently discovered podocyte antigens: the M-type phospholipase A2 receptor 1 (PLA2R) and thrombospondin type 1 domain-containing 7A (THSD7A). Assays for quantitative assessment of anti-PLA2R antibodies are commercially available, but a semiquantitative test to detect anti-THSD7A antibodies has been only recently developed. The presence or absence of anti-PLA2R and anti-THSD7A antibodies adds important information to clinical and immunopathologic data in discriminating between primary and secondary MN. Levels of anti-PLA2R antibodies and possibly, anti-THSD7A antibodies tightly correlate with disease activity. Low baseline and decreasing anti-PLA2R antibody levels strongly predict spontaneous remission, thus favoring conservative therapy. Conversely, high baseline or increasing anti-PLA2R antibody levels associate with nephrotic syndrome and progressive loss of kidney function, thereby encouraging prompt initiation of immunosuppressive therapy. Serum anti-PLA2R antibody profiles reliably predict response to therapy, and levels at completion of therapy may forecast long-term outcome. Re-emergence of or increase in antibody titers precedes a clinical relapse. Persistence or reappearance of anti-PLA2R antibodies after kidney transplant predicts development of recurrent disease. We propose that an individualized serology-based approach to MN, used to complement and refine the traditional proteinuria-driven approach, will improve the outcome in this disease.

Membranous nephropathy: integrating basic science into improved clinical management

Idiopathic membranous nephropathy (INM) remains a common cause of the nephrotic syndrome in adults. The autoimmune nature of IMN was clearly delineated in 2009 with the identification of the glomerular-deposited IgG to be a podocyte receptor, phospholipase A2 receptor (PLA2R) in 70% to 75% of cases. This anti-PLA2R autoantibody, predominantly the IgG4 subclass, has been quantitated in serum using an enzyme-linked immunosorbent assay and has been used to aid diagnosis and monitor response to immunosuppressive therapy. In 2014, a second autoantigen, thrombospondin type 1 domain-containing 7A (THSD7A), was identified. Immunostaining of biopsy specimens has further detected either PLA2R or THSD7A antigen in the deposited immune complexes in 5% to 10% of cases autoantibody seronegative at the time of biopsy. Therefore, the term IMN should now be superseded by the term primary or autoimmune MN (AMN) (anti-PLA2R or anti-THSD7A positive) classifying ∼80% to 90% of cases previously designated IMN. Cases of secondary MN associated with other diseases show much lower association with these autoantibodies, but their true incidence in secondary cases still needs to be defined. How knowledge of the autoimmune mechanism and the sequential measurement of these autoantibodies is likely to change the clinical management and trajectory of AMN by more precisely defining its diagnosis, prognosis, and treatment is discussed. Their application early in the disease course to new and old therapies will provide additional precision to AMN management. We also review innovative therapeutic approaches on the horizon that are expected to lead to our ultimate goal of improved patient care in A(I)MN.

Lipoquality control by phospholipase A2 enzymes

The phospholipase A₂ (PLA₂) family comprises a group of lipolytic enzymes that typically hydrolyze the sn-2 position of glycerophospholipids to give rise to fatty acids and lysophospholipids. The mammalian genome encodes more than 50 PLA₂s or related enzymes, which are classified into several subfamilies on the basis of their structures and functions. From a general viewpoint, the PLA₂ family has mainly been implicated in signal transduction, producing bioactive lipid mediators derived from fatty acids and lysophospholipids. Recent evidence indicates that PLA₂s also contribute to phospholipid remodeling for membrane homeostasis or energy production for fatty acid β-oxidation. Accordingly, PLA₂ enzymes can be regarded as one of the key regulators of the quality of lipids, which I herein refer to as lipoquality. Disturbance of PLA₂-regulated lipoquality hampers tissue and cellular homeostasis and can be linked to various diseases. Here I overview the current state of understanding of the classification, enzymatic properties, and physiological functions of the PLA₂ family.

A Rare Adult Case with Diffuse Segmental Membranous Glomerulonephritis

A 71-year-old man with hypertension and diabetes mellitus presented with proteinuria. Laboratory data showed proteinuria of 3.1 g/g creatinine, serum albumin of 3.5 g/dL and serum creatinine of 1.03 mg/dL without autoantibodies. A renal biopsy revealed segmental granular IgG depositions on glomerular capillary walls. Electron microscopy showed segmentally subepithelial, intramembranous and mesangial deposits. Diffuse segmental membranous glomerulonephritis (MGN) was diagnosed with only IgG1 deposition and without M-type phospholipase A2 receptor or thrombospondin type-1 domain-containing 7A staining, suggesting secondary MGN with an unknown target antigen in immune deposits. Physicians should keep in mind the existence of segmental MGN to better understand the clinicopathological characteristics.

HLA-DRB1*15:01 and HLA-DRB3*02:02 in PLA2R-Related Membranous Nephropathy

Idiopathic membranous nephropathy (MN) is associated with HLA; however, the HLA allele involved remains unknown. To identify the HLA risk alleles associated with phospholipase A2 receptor (PLA2R)-related MN in the Chinese population, we sequenced the entire MHC region in DNA samples from 99 patients with PLA2R-related MN, 50 patients with PLA2R-unrelated MN, and 100 healthy subjects. Two HLA risk alleles, HLA-DRB1*15:01 and HLA-DRB3*02:02, independently and strongly associated with an increased risk of PLA2R-related MN. After adjusting for HLA-DRB1*15:01 and HLA-DRB3*02:02, no other alleles showed significant association with PLA2R-related MN. A replication study in an independent cohort of 293 participants with PLA2R-related MN and 285 healthy controls validated these findings. In a joint analysis, a multivariate logistic regression model confirmed that HLA-DRB1*15:01 (odds ratio [OR], 24.9; 95% confidence interval [95% CI], 15.3 to 42.6; P=2.3×10^-35) and HLA-DRB3*02:02 (OR, 17.7; 95% CI, 11.0 to 30.3; P=8.0×10^-29) independently and strongly associated with PLA2R-related MN. As many as 98.7% of patients with PLA2R-related MN, compared with 43.9% of control subjects, carried at least one HLA risk allele. Subjects with either risk allele had higher odds of developing PLA2R-related MN than those without a risk allele (OR, 98.9; 95% CI, 44.4 to 281.7; P=2.5×10^-23). These HLA risk alleles also associated with the age at disease onset in patients with PLA2R-related MN. In conclusion, our findings provide clear evidence that the HLA-DRB1*15:01 and HLA-DRB3*02:02 alleles independently and strongly associate with PLA2R-related MN in the Chinese population.

Characterization of glomerular extracellular matrix by proteomic analysis of laser-captured microdissected glomeruli

Abnormal extracellular matrix (ECM) remodeling is a prominent feature of many glomerular diseases and is a final common pathway of glomerular injury. However, changes in ECM composition accompanying disease-related remodeling are unknown. The physical properties of ECM create challenges for characterization of composition using standard protein extraction techniques, as the insoluble components of ECM are frequently discarded and many ECM proteins are in low abundance compared to other cell proteins. Prior proteomic studies defining normal ECM composition used a large number of glomeruli isolated from human kidneys retrieved for transplantation or by nephrectomy for cancer. Here we examined the ability to identify ECM proteins by mass spectrometry using glomerular sections compatible with those available from standard renal biopsy specimens. Proteins were classified as ECM by comparison to the Matrisome database and previously identified glomerular ECM proteins. Optimal ECM protein identification resulted from sequential decellularization and protein extraction of 100 human glomerular sections isolated by laser capture microdissection from either frozen or formalin-fixed, paraffin-embedded tissue. In total, 147 ECM proteins were identified, including the majority of structural and GBM proteins previously identified along with a number of matrix and glomerular basement membrane proteins not previously associated with glomeruli. Thus, our study demonstrates the feasibility of proteomic analysis of glomerular ECM from retrieved glomerular sections isolated from renal biopsy tissue and expands the list of known ECM proteins in glomeruli.

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

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

PLA2R antibodies and PLA2R glomerular deposits in psoriasis patients with membranous nephropathy

Background

The association between psoriasis and membranous nephropathy (MN) remains largely unclear. We examined the prevalence of serum PLA2R antibody and characterized the expression of PLA2R and THSD7A in glomeruli in patients with MN and psoriasis.

Methods

A total of 24 patients with MN without evidence of a secondary cause except psoriasis were enrolled. The clinical and pathological features were retrospectively analyzed. Serum anti-PLA2R antibody was measured using IFA Mosaic. Renal tissue samples stored in the laboratory bio-bank were used for PLA2R staining under immunofluorescence microscopy and THSD7A immunohistochemical analysis.

Results

Twenty-four patients (21 male and 3 female) with a mean age of 43.6 ± 15.7 years old were enrolled. Serum anti-PLA2R antibody was positive in 7 patients, which was significantly lower than the positivity observed in idiopathic MN (29.2% vs. 81.7%, P < 0.001). Glomerular PLA2R staining was positive in 7 patients with positive serum anti-PLA2R antibody. THSD7A staining was negative in all 24 patients. During the follow-up visits, 13 patients with negative serum PLA2R antibody achieved CR. In contrast, CR was only achieved in 1 patient with positive serum PLA2R antibody, PR was achieved in 2 patients.

Conclusions

The prevalence of serum anti-PLA2R antibody and glomerular expression of PLA2R was significantly lower in patients with psoriasis and MN than in those with idiopathic MN, and THSD7A staining was negative, suggesting that MN is associated with psoriasis in the majority of patients. However, idiopathic MN might also accompany psoriasis in a minority of psoriatic patients with positive serum anti-PLA2R antibody.

Recent advances in our understanding of recurrent primary glomerulonephritis after kidney transplantation

Recurrent glomerulonephritis (GN) is an important cause of kidney allograft failure, particularly in younger recipients. Approximately 15% of death-censored graft failures are due to recurrent GN, but this incidence is likely an underestimation of the magnitude of the problem. Overall, 18% to 22% of kidney allografts are lost due to GN, either recurrent or presumed de novo. The impact of recurrent GN on allograft survival was recognized from the earliest times in kidney transplantation. However, progress in this area has been slow, and our understanding of GN recurrence remains limited, in large part due to incomplete understanding of the pathogenesis of these diseases. This review focuses on recent advances in our general understanding of the pathophysiology of primary GN, the risk of recurrence in the allograft, and the consequences for kidney graft survival. We focus specifically on the most common forms of primary GN, including focal segmental glomerulosclerosis, membranous nephropathy, membranoproliferative glomerulonephritis, and IgA nephropathy. New understanding of the pathogenesis of these diseases has had direct clinical implications for transplantation, allowing better identification of candidates at high risk of recurrence and earlier diagnoses, and it is expected to lead to significance improvements in the therapy and perhaps even prevention of GN recurrence. More than ever, it is essential to fully characterize GN before transplantation as this information will direct our management posttransplantation. Further, the relative rarity of recurrent GN dictates the need for multicenter studies in order to evaluate, test, and validate recent advances and therapies.

All Things Complement

The complement (C) cascade is an ancient system of proteins whose primary role is to initiate and modulate immune responses. During C activation, circulating proteins are cleaved and nascent cleavage fragments participate in a broad range of downstream innate and adaptive immune functions. Although the majority of these functions are either homeostatic or protective, a large body of experimental and clinical evidence also highlights a central role for the C system in the pathogenesis of many types of glomerular disease. From classic pathway activation in lupus nephritis to alternative pathway dysregulation in C3 glomerulopathy, our understanding of the spectrum of C involvement in kidney disease has expanded greatly in recent years. However, the characteristics that make the glomerulus so uniquely susceptible to C-mediated injury are not fully understood, and this remains an area of ongoing investigation. Several C inhibitors have been approved for clinical use, and additional C inhibitory drugs are in development. The use of these drugs in patients with kidney disease will expand our understanding of the benefits and limitations of C inhibition.

Temporal IgG Subtype Changes in Recurrent Idiopathic Membranous Nephropathy

Determination of the IgG subtypes within the immune deposits in membranous nephropathy (MN) may be helpful in the differential diagnosis. IgG4 is the predominant subtype in idiopathic MN and recurrent MN, while IgG1, IgG2, and IgG3 subtypes are more common in secondary MN and de novo disease in the allograft. The temporal change of IgG subclasses in individual patients and its correlation with clinical variables have not been studied. We reviewed all posttransplantation protocol and indication biopsies (49) in 18 patients with recurrent MN who underwent transplantation at our center between 1998 and 2013 and performed IgG subtyping (IgG1-4). We tested serum for M-type phospholipase A2 receptor (PLA2 R) autoantibodies or performed PLA2 R antigen staining on the kidney biopsy. IgG4 was the (co)dominant IgG subtype in 10 of 14 biopsies at the diagnosis of recurrence regardless of PLA2 R association. In 8 of 12 transplantations with serial biopsies, the (co)dominant subtype did not change over time. There was a trend toward IgG1 and IgG3 (co)dominance in biopsies >1 year from recurrence and more IgG1 (co)dominant subtyping in the setting of more-advanced EM deposits. Treatment with rituximab did not affect the IgG subtype. In conclusion, the dominant IgG subtype did not change over time in recurrent MN.

Rituximab in Membranous Nephropathy: Not All Studies Are Created Equal

Many prospective studies and a recent randomized controlled trial have shown that the B-cell-depleting monoclonal antibody, rituximab, safely promotes the remission of nephrotic syndrome in approximately 65% of patients with membranous nephropathy (MN). Mechanistic studies have indicated that rituximab-induced proteinuria reduction is associated with clearance of anti-podocyte antigens phospholipase 2 receptor autoantibodies and subepithelial immune complexes, the hallmarks of the disease. A recently published study reported results which, at first sight, looked less favorable and implied that, due to a publication bias against negative results, the efficacy of rituximab in MN might be overestimated. Since patients received only one or 2 rituximab administrations, the authors suggest that when rituximab is used, higher doses and longer treatments should be considered. In this study, we highlight limitations of the study and warn against an oversimplified interpretation of the data. Though information on the optimal dose of rituximab to use in MN is still limited, available data from studies with predefined rituximab administration protocols collectively support the concept of titrating rituximab to the number of circulating B-cells that are invariably depleted after the first or second administration. Additional doses may increase the risk of adverse effects and related costs without augmenting efficacy. Importantly, underpowered studies with inconclusive results should not be confused with negative studies formally proving a neutral effect of a treatment. Until data from ad hoc designed clinical trials are available, the B-cell-driven protocol should be the preferred regimen, since it is similarly effective, but safer and more cost effective than other protocols employing multiple rituximab administrations.

Glomerular basement membrane heparan sulfate in health and disease: A regulator of local complement activation

The glomerular basement membrane (GBM) is an essential component of the glomerular filtration barrier. Heparan sulfate proteoglycans such as agrin are major components of the GBM, along with α345(IV) collagen, laminin-521 and nidogen. A loss of GBM heparan sulfate chains is associated with proteinuria in several glomerular diseases and may contribute to the underlying pathology. As the major determinants of the anionic charge of the GBM, heparan sulfate chains have been thought to impart charge selectivity to the glomerular filtration, a view challenged by the negligible albuminuria in mice that lack heparan sulfate in the GBM. Recent studies provide increasing evidence that heparan sulfate chains modulate local complement activation by recruiting complement regulatory protein factor H, the major inhibitor of the alternative pathway in plasma. Factor H selectively inactivates C3b bound to surfaces bearing host-specific polyanions such as heparan sulfate, thus limiting complement activation on self surfaces such as the GBM, which are not protected by cell-bound complement regulators. We discuss mechanisms whereby the acquired loss of GBM heparan sulfate can impair the local regulation of the alternative pathway, exacerbating complement activation and glomerular injury in immune-mediated kidney diseases such as membranous nephropathy and lupus nephritis.

HLA-DR, and not PLA2R, is expressed on the podocytes in kidney allografts in de novo membranous nephropathy

Idiopathic membranous nephropathy (IMN) is known to be associated with antibodies acting on the M-type phospholipase A2 receptor (PLA2R) of the podocyte. However, the mechanism underlying de novo membranous nephropathy (dn MN) posttransplantation remains unclear. In this study, we aimed to elucidate the mechanism underlying dn MN.We selected 8 cases with dn MN and compared them to 20 IMN cases. Fifteen cases of stable grafts were selected as controls.Several differences between the dn MN group and the IMN group were detected. IgG4 showed negligible positive staining in patients with dn MN, while it was predominant in the IMN group (1/8 vs 20/20, P < 0.001). Serum anti-PLA2R antibodies and anti-PLA2R antibodies of the podocyte were very few in the dn MN patients; however, these antibodies were detected in most of the IMN patients (serum anti-PLA2R antibodies: 1/8 vs 16/20, P = 0.002, anti-PLA2R antibodies of the podocyte: 0/8 vs 17/20, P < 0.001). The dn MN patients also showed higher ratio of interstitial inflammation, peritubular capillaritis, and peritubular capillary C4d deposition. Importantly, human leukocyte antigens (HLA)-DR expression was detected on the podocytes in most of the dn MN patients, but none of the IMN patients and stable graft patients showed HLA-DR expression.These data suggested that the PLA2R pathway, which is known to play a role in IMN, was not involved in the mechanism underlying dn MN. On the contrary, dn MN might be associated with the alloimmune response directed against the podocyte.

Rituximab use in adult primary glomerulopathy: where is the evidence?

Rituximab is a chimeric anti-CD20 antibody that results in depletion of B-cell lymphocytes. It is currently used in the treatment of a variety of autoimmune diseases, in addition to CD20-positive lymphomas. The use of rituximab in the treatment of the adult primary glomerular diseases has emerged recently, although not yet established as first-line therapy in international guidelines. In patients with steroid-dependent minimal change disease or frequently relapsing disease, and in patients with idiopathic membranous nephropathy (IMN), several retrospective and prospective studies support the use of rituximab to induce remission, whereas in idiopathic focal and segmental glomerulosclerosis (FSGS), the use of rituximab has resulted in variable results. Evidence is still lacking for the use of rituximab in patients with immunoglobulin A nephropathy (IgAN) and idiopathic membranoproliferative glomerulonephritis (MPGN), as only few reports used rituximab in these two entities. Randomized controlled trials (RCTs) are warranted and clearly needed to establish the definitive role of rituximab in the management of steroid-dependent and frequently relapsing minimal change disease, IMN, both as first-line and second-line treatment, and in MPGN. We await the results of an ongoing RCT of rituximab use in IgAN. Although current evidence for the use of rituximab in patients with idiopathic FSGS is poor, more RCTs are needed to clarify its role, if any, in the management of steroid-resistant or steroid-dependent FSGS.

IgG Subclass Staining in Routine Renal Biopsy Material

Immunofluorescence staining plays a vital role in nephropathology, but the panel of antibodies used has not changed for decades. Further classification of immunoglobulin (Ig)G-containing immune-type deposits with IgG subclass staining (IgG1, IgG2, IgG3, and IgG4) has been shown to be of diagnostic utility in glomerular diseases, but their value in the evaluation of renal biopsies has not been addressed systematically in large renal biopsy material. Between January 2007 and June 2014, using direct immunofluorescence, we stained every renal biopsy for the IgG subclasses if there was moderate to prominent glomerular IgG staining and/or IgG-predominant or IgG-codominant glomerular staining. The total number of biopsies stained was 1084, which included 367 cases of membranous glomerulonephritis, 307 cases of lupus nephritis, 74 cases of fibrillary glomerulonephritis, 53 cases of proliferative glomerulonephritis with monoclonal IgG deposits, and 25 cases of antiglomerular basement membrane disease, among others. We found that monoclonality of IgG deposits cannot always be reliably determined on the basis of kappa and lambda light chain staining alone, particularly if concomitant (frequently nonspecific) IgM staining is present. In IgG heavy and heavy and light chain deposition disease (3 cases), subclass staining is very helpful, and in proliferative glomerulonephritis with monoclonal IgG deposits subclass staining is necessary. IgG subclass staining is useful in differentiating primary from secondary membranous glomerulonephritis. In proliferative glomerulonephritis with polyclonal IgG deposition, IgG1 dominance/codominance with concomitant IgG3 and IgG2 but weak or absent IgG4 staining favors an underlying autoimmune disease. IgG subclass staining is a very useful diagnostic method in a selected cohort of renal biopsies, particularly in biopsies with glomerulonephritis with monoclonal IgG deposits.

Clinicopathologic Features of Membranous-Like Glomerulopathy With Masked IgG Kappa Deposits

Introduction

Ig deposits identified on renal biopsy samples by paraffin immunofluorescence that show negative staining by routine immunofluorescence on frozen tissue have become known as “masked” deposits. Membranous-like glomerulopathy with masked IgG kappa (κ) deposits is a recently recognized pattern of immune complex deposition characterized by masked deposits that show IgG κ restriction and are subepithelial and mesangial by electron microscopy. Based on the frequent presence of C3-only staining by routine immunofluorescence microscopy (IF), these cases could be misdiagnosed as C3 glomerulonephritis in the absence of paraffin immunofluorescence evaluation.

Methods

The clinicopathologic details of all cases of membranous-like glomerulopathy with masked IgG κ deposits diagnosed in our laboratory were included, beginning with the initial recognition of this entity in 2011 through the end of 2015. Inclusion was based on renal biopsy sample morphologic features including glomerular deposits that stain for IgG κ and have a staining intensity that is significantly brighter by paraffin IF than by routine IF on frozen tissue.

Results

This pattern of immune complex deposition has been seen in 41 patients in our laboratory over a 5-year period. The patients with these biopsy findings are most commonly young female individuals with a mean age of 27.5 years, with 88% being less than 40 years. All patients had proteinuria with a mean 24-hour urine protein of 3.5 g (range 0.5−12.8 years) and 35% with nephrotic-range proteinuria. Hematuria was present in 88% of patients, and 29% had elevated serum creatinine at presentation. Autoimmune serologic tests were positive in 55% of patients, with a weakly positive antinuclear antibody being most common. Despite this, only 1 patient (2%) fulfilled the diagnostic criteria for systemic lupus erythematosus. The outcome data were mixed, as some patients showed spontaneous remission and mild disease whereas others progressed to end-stage renal disease. There was no apparent correlation between the treatment used and outcome in this retrospective analysis. One patient underwent transplantation and developed biopsy-proven recurrence of disease in the graft 42 months posttransplantation. The etiology of this entity remains unknown.

Discussion

We provide an expanded case series detailing the clinicopathologic findings of patients with membranous-like glomerulopathy with masked IgG κ deposits. Patients are most commonly young female individuals <40 years of age and commonly have positive autoimmune serologic studies such as antinuclear antibody, although few carry a diagnosis of any well-defined autoimmune disease such as lupus. The outcome data were mixed, as some patients showed spontaneous remission and mild disease whereas others progressed to ESRD. There was no apparent correlation between the treatment used and outcome in this retrospective analysis.

Prevalence of serum anti M-type phospholipase A2 receptor antibody in primary membranous nephropathy: A single center experience

We conducted a prospective study to assess utility of detection of antibodies to phospholipase A₂receptor (PLA₂R) in the serum of patients with membranous nephropathy. Seventy five patients with biopsy proven membranous nephropathy admitted between January 2011 and September 2014 were studied. Serum anti- PLA₂R was tested by indirect immunofluorescence. The test was positive in 45 out of 60 patients with primary membranous nephropathy (PMN) and in none of the 15 patients with secondary membranous nephropathy, with a sensitivity of 75% and specificity of 100% for PMN. Anti PLA₂R positivity also showed a significant correlation with quantum of proteinuria and negative correlation with serum albumin. This study has validated detection of serum anti PLA₂R in PMN as a non invasive diagnostic tool in Indian patients.

[Glomerulonephritides]

Many forms of glomerulonephritis, even the more common types belong to the so-called rare diseases; however, they are very important, for example with respect to health economics as they often affect young people. An example is immunoglobulin A (IgA) nephropathy, which is the most common cause of end stage renal disease in young adults. This review summarizes the current knowledge on the pathogenesis, clinical presentation and therapy of the most common European types of glomerulonephritis with a special focus on the most recently acquired knowledge on IgA nephropathy, membranous glomerulonephritis, minimal change nephropathy and focal segmental glomerulosclerosis (FSGS).

Basement membranes and autoimmune diseases

Basement membrane components are targets of autoimmune attack in diverse diseases that destroy kidneys, lungs, skin, mucous membranes, joints, and other organs in man. Epitopes on collagen and laminin, in particular, are targeted by autoantibodies and T cells in anti-glomerular basement membrane glomerulonephritis, Goodpasture's disease, rheumatoid arthritis, post-lung transplant bronchiolitis obliterans syndrome, and multiple autoimmune dermatoses. This review examines major diseases linked to basement membrane autoreactivity, with a focus on investigations in patients and animal models that advance our understanding of disease pathogenesis. Autoimmunity to glomerular basement membrane type IV is discussed in depth as a prototypic organ-specific autoimmune disease yielding novel insights into the complexity of anti-basement membrane immunity and the roles of genetic and environmental susceptibility.

Motor neuron-derived Thsd7a is essential for zebrafish vascular development via the Notch-dll4 signaling pathway

Background

Development of neural and vascular systems displays astonishing similarities among vertebrates. This parallelism is under a precise control of complex guidance signals and neurovascular interactions. Previously, our group identified a highly conserved neural protein called thrombospondin type I domain containing 7A (THSD7A). Soluble THSD7A promoted and guided endothelial cell migration, tube formation and sprouting. In addition, we showed that thsd7a could be detected in the nervous system and was required for intersegmental vessels (ISV) patterning during zebrafish development. However, the exact origin of THSD7A and its effect on neurovascular interaction remains unclear.

Results

In this study, we discovered that zebrafish thsd7a was expressed in the primary motor neurons. Knockdown of Thsd7a disrupted normal primary motor neuron formation and ISV sprouting in the Tg(kdr:EGFP/mnx1:TagRFP) double transgenic zebrafish. Interestingly, we found that Thsd7a morphants displayed distinct phenotypes that are very similar to the loss of Notch-delta like 4 (dll4) signaling. Transcript profiling further revealed that expression levels of notch1b and its downstream targets, vegfr2/3 and nrarpb, were down-regulated in the Thsd7a morphants. These data supported that zebrafish Thsd7a could regulate angiogenic sprouting via Notch-dll4 signaling during development.

Conclusions

Our results suggested that motor neuron-derived Thsd7a plays a significant role in neurovascular interactions. Thsd7a could regulate ISV angiogenesis via Notch-dll4 signaling. Thus, Thsd7a is a potent angioneurin involved in the development of both neural and vascular systems.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-016-0277-9) contains supplementary material, which is available to authorized users.

Insights into kidney diseases from genome-wide association studies

Over the past decade, genome-wide association studies (GWAS) have considerably improved our understanding of the genetic basis of kidney function and disease. Population-based studies, used to investigate traits that define chronic kidney disease (CKD), have identified >50 genomic regions in which common genetic variants associate with estimated glomerular filtration rate or urinary albumin-to-creatinine ratio. Case-control studies, used to study specific CKD aetiologies, have yielded risk loci for specific kidney diseases such as IgA nephropathy and membranous nephropathy. In this Review, we summarize important findings from GWAS and clinical and experimental follow-up studies. We also compare risk allele frequency, effect sizes, and specificity in GWAS of CKD-defining traits and GWAS of specific CKD aetiologies and the implications for study design. Genomic regions identified in GWAS of CKD-defining traits can contain causal genes for monogenic kidney diseases. Population-based research on kidney function traits can therefore generate insights into more severe forms of kidney diseases. Experimental follow-up studies have begun to identify causal genes and variants, which are potential therapeutic targets, and suggest mechanisms underlying the high allele frequency of causal variants. GWAS are thus a useful approach to advance knowledge in nephrology.

An Indirect Immunofluorescence Method Facilitates Detection of Thrombospondin Type 1 Domain-Containing 7A-Specific Antibodies in Membranous Nephropathy

Thrombospondin type 1 domain-containing 7A (THSD7A) is a target antigen identified in adult membranous nephropathy (MN) along with the major antigen phospholipase A₂ receptor 1 (PLA₂R1). The prevalence of THSD7A-Ab-positive patients is unknown, and it is unclear whether the clinical presentation differs between patients positive for PLA₂R1-Ab or THSD7A-Ab. We screened serum samples of 1276 patients with MN from three different cohorts for the presence of THSD7A-Ab by Western blot analysis and a newly developed indirect immunofluorescence test (IFT). Compared with Western blot analysis, the IFT had a 92% sensitivity and a 100% specificity. The prevalence of THSD7A-associated MN in a prospective cohort of 345 patients with MN was 2.6%, and most were women. In this cohort, the percentage of patients with THSD7A-associated MN and malignant disease significantly exceeded that of patients with PLA₂R1-associated MN and malignant disease. In all cohorts, we identified 40 patients with THSD7A-associated MN, eight of whom developed a malignancy within a median time of 3 months from diagnosis of MN. In one patient with THSD7A-associated MN and metastases of an endometrial carcinoma, immunohistochemistry showed THSD7A expression on the metastatic cells and within follicular dendritic cells of the metastasis-infiltrated lymph node. We conclude that the IFT allows sensitive and specific measurement of circulating THSD7A-Ab in patients with MN. Patients with THSD7A-associated MN differ in their clinical characteristics from patients with PLA₂R1-associated MN, and more intensive screening for the presence of malignancies may be warranted in those with THSD7A-associated MN.