Biomarkers to detect membranous nephropathy in Chinese patients

Chinese medicinal herbs for idiopathic membranous nephropathy in adults with nephrotic syndrome: A systematic review of effectiveness and safety

ABSTRACT

To assess the benefits and harms of Chinese medicinal herbs formulae for the treatment of idiopathic membranous nephropathy in adult patients with primary nephrotic syndrome.Only randomized controlled trials were included. We searched the Cochrane Central Register of Controlled Trials database, PubMed, EMBASE, Chinese National Knowledge Internet, Chinese Biomedicine Database, and VIP. All studies were analyzed using the criteria of the Cochrane Handbook and were assessed in terms of quality and the risk of bias. Review Manager ver. 5.3.5 software was used for the data analysis, and GRADE profiler software was employed to evaluate quality.Two studies were included (n = 126 Chinese participants). We found that compared with against conventional treatment, one Chinese medicinal herbs formula plus conventional treatment reduced 24-hours urinary total protein (mean differences -3.16 g/24 h, 95% confidence intervals -4.03 to -2.29), and two Chinese medicinal herbs formulae increased serum albumin levels (mean differences 3.18 g/L, 95% confidence intervals 1.12 to 5.52; I2 = 0%).Chinese medicinal herbs formulae may reduce 24-hours urinary total protein and increase serum levels of albumin. However, larger and multicenter studies with high methodological quality are still needed.

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).

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

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

Novel ELISA for thrombospondin type 1 domain-containing 7A autoantibodies in membranous nephropathy

Autoantibodies against phospholipase A2 receptor 1 (PLA2R1) and thrombospondin type 1 domain-containing 7A (THSD7A) are emerging as biomarkers to classify membranous nephropathy (MN) and to predict outcome or response to treatment. Anti-THSD7A autoantibodies are detected by Western blot and indirect immunofluorescence test (IIFT). Here, we developed a sensitive enzyme-linked immunosorbent assay (ELISA) optimized for quantitative detection of anti-THSD7A autoantibodies. Among 1012 biopsy-proven MN patients from 6 cohorts, 28 THSD7A-positive patients were identified by ELISA, indicating a prevalence of 2.8%. By screening additional patients, mostly referred because of PLA2R1-unrelated MN, we identified 21 more cases, establishing a cohort of 49 THSD7A-positive patients. Twenty-eight patients (57%) were male, and male patients were older than female patients (67 versus 49 years). Eight patients had a history of malignancy, but only 3 were diagnosed with malignancy within 2 years of MN diagnosis. We compared the results of ELISA, IIFT, Western blot, and biopsy staining, and found a significant correlation between ELISA and IIFT titers. Anti-THSD7A autoantibodies were predominantly IgG4 in all patients. Eight patients were double positive for THSD7A and PLA2R1. Levels of anti-THSD7A autoantibodies correlated with disease activity and with response to treatment. Patients with high titer at baseline had poor clinical outcome. In a subgroup of patients with serial titers, persistently elevated anti-THSD7A autoantibodies were observed in patients who did not respond to treatment or did not achieve remission. We conclude that the novel anti-THSD7A ELISA can be used to identify patients with THSD7A-associated MN and to monitor autoantibody titers during treatment.

Clinical value of renal phospholipase A2 receptor deposit in the prognosis evaluation and treatment options of idiopathic membranous nephropathy: A retrospective cohort study

Aim

Phospholipase A2 receptor (PLA2R) is a target antigen for idiopathic membranous nephropathy (IMN). However, the association between renal PLA2R antigen and disease prognosis had not been fully investigated. In addition, there was a paucity of studies investigating the difference of therapeutic effects between cyclophosphamide and cyclosporine A in PLA2R‐associated IMN.

Methods

This retrospective cohort study recruited 300 eligible patients diagnosed with biopsy‐proven IMN between September 2015 and July 2018 in Guangdong Provincial People's Hospital. The remission of proteinuria was compared between PLA2R‐associated and non‐PLA2R‐associated IMN. The difference of therapeutic effects between cyclophosphamide and cyclosporine A were also investigated in PLA2R‐associated IMN.

Results

The positive rate of renal PLA2R antigen in recruited IMN patients was 82.3%. Non‐PLA2R‐associated IMN patients had a higher probability to achieve remission than PLA2R‐associated IMN patients (Log–rank test, P = .013). Multivariate COX analysis showed that renal PLA2R antigen was an independent risk factor for not achieving remission in IMN patients (Hazard Ratio: 1.619; 95% confidence interval: 1.133 to 2.313; P = .008). In PLA2R‐associated IMN, patients receiving cyclophosphamide had a higher probability to achieve remission compared with those receiving cyclosporine A (Log–rank test, P = .018) while there was no difference in renal survival. Multivariate COX regression analysis showed that compared with cyclosporine A, patients receiving cyclophosphamide had a higher probability to achieve remission.

Conclusion

Phospholipase A2 receptor ‐associated IMN patients had a lower probability to achieve remission compared with non‐PLA2R‐associated IMN. Compared with cyclosporine A, cyclophosphamide exerted better therapeutic effects in remission of proteinuria and may be the preferred immunosuppressant for PLA2R‐associated IMN.

Primary Membranous Glomerulonephritis: The Role of Serum and Urine Biomarkers in Patient Management

The detection of phospholipase A2 receptor (PLA2R) and thrombospondin domain containing 7A THSD7A among primary membranous glomerulonephritis (MGN) patients transformed the diagnosis, treatment monitoring, and prognosis. Anti-PLA2R can be detected in 70-90% of primary MGN patients while anti-THSD7A in 2-3% of anti-PLA2R negative primary MGN patients depending on the technique used. Serum and urine samples are less invasive and non-invasive, respectively, and thus can detect the presence of anti-PLA2R and anti-THSD7A with higher sensitivity and specificity, which is significant in patient monitoring and prognosis. It is better than exposing patients to a frequent biopsy, which is an invasive procedure. Different techniques of detection of PLA2R and THSD7A in patients' urine and sera were reviewed to provide newer and alternative techniques. We proposed the use of biomarkers (PLA2R and THSD7A) in the diagnosis, treatment decision, and follow-up of patients with primary MGN. In addition, other prognostic renal biomarkers like retinol binding protein (RBP) and beta-2 microglobulin were reviewed to detect the progression of renal damage for early intervention.

Features of phospholipase A2 receptor and thrombospondin type-1 domain-containing 7A in malignancy-associated membranous nephropathy

Aims

Phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A) were identified as pathogenic antigens in patients with membranous nephropathy (MN). Notably, PLA2R is detected in few patients with malignancy-associated MN, and a high incidence of cancer is reported in patients with THSD7A-associated MN. Therefore, the roles of PLA2R and THSD7A in malignancy-associated MN must be clarified.

Methods

Serum anti-PLA2R antibodies and glomerular PLA2R staining were assessed in 36 patients with malignancy-associated MN, followed by examination of serum anti-THSD7A antibodies and glomerular THSD7A. THSD7A staining in cancer tissues was also assessed in 9 of the 36 patients.

Results

Twelve (33%) of 36 patients were positive for both glomerular PLA2R and serum anti-PLA2R antibodies, one of whom had enhanced glomerular THSD7A staining. Two patients were positive for either glomerular PLA2R or serum anti-PLA2R antibody. All these patients had IgG4-dominant deposits in glomeruli. Among the 22 (61%) patients who were double negative for glomerular PLA2R and serum anti-PLA2R antibodies, 17 of 20 (85%) had IgG1-dominant deposits in glomeruli, and 2 (9.1%) were positive for glomerular THSD7A staining. Serum anti-THSD7A antibody was not detected in any of the 36 patients. Among the nine patients with available cancer tissues, positive staining of THSD7A in the cancer tissues was observed in five (56%) patients, and one showed enhanced glomerular staining of THSD7A.

Conclusions

Screening of glomerular PLA2R antigen and serum anti-PLA2R antibodies is necessary in patients with malignancy-associated MN, whereas the incidence of glomerular THSD7A antigen or circulating anti-THSD7A antibodies is uncommon.

Prognostic value of phospholipase A2 receptor in primary membranous nephropathy: a systematic review and meta-analysis

PURPOSE

We aimed to evaluate the prognostic value of serum anti-PLA2R and glomerular PLA2R deposit (gPLA2R) in predicting remission of proteinuria in Primary Membranous Nephropathy (PMN) patients.

METHODS

PUBMED, EMBASE, WEB OF SCIENCE, COCHRANE LIBRARY and CNKI were searched from 2008 January to December 2018. Heterogeneity was assessed by Cochran Q test and I². Source of heterogeneity was explored by subgroup analysis and sensitivity analysis.

RESULTS

Totally 2345 patients from 29 cohort studies were eligible for inclusion. The results suggested that PMN patients with negative anti-PLA2R at the time of biopsy had a 1.31 times (95% CI 1.12-1.46, p < 0.05) higher possibility in achieving remission than those with positive anti-PLA2R. The clearance of anti-PLA2R at the end of immunosuppressive therapy showed an even greater chance of achieving remission (RR = 2.86, 95% CI 1.75-4.69, p < 0.05). The relative ratios for complete remission and spontaneous remission with negative anti-PLA2R were 1.65 (95% CI 1.46-1.87, p < 0.05) and 1.93, respectively (95% CI 1.53-2.45, p < 0.05), and heterogeneity percentages were I² = 18% and 46%, respectively. The possibility for remission was significantly greater among PMN patients with negative gPLA2R (RR = 1.30, 95% CI 1.13-1.50, p < 0.05). Subgroup analyses revealed that retrospective design of study might be the potential source of heterogeneity.

CONCLUSIONS

Negative anti-PLA2R or gPLA2R might predict higher possibility of remission, and the presence of anti-PLA2R or gPLA2R might serve as a useful biomarker for clinical outcome and predicting response to immunosuppressive therapy in PMN.

Clinicopathological features of atypical membranous nephropathy with unknown etiology in adult Chinese patients

Membranous nephropathy is typically classified as idiopathic and secondary, but nowadays the number of atypical membranous nephropathy (aMN) is increasing, many of which cannot determine its etiology in China. In this study, we compared the clinical and pathological characteristics of idiopathic membranous nephropathy (iMN) with aMN with unknown etiology from a single center in China.We retrospectively reviewed the clinical data of 577 patients with iMN and aMN at Peking University People's Hospital from January 2006 to December 2015 over a 10-year period, and analyzed their clinical and pathological characteristics. The level of serum phospholipase A2 receptors (PLA2R) antibody was detected in 106 iMN and 162 aMN patients.There were 278 iMN patients and 299 aMN patients who were included into this study in 3210 cases of renal biopsy during a 10-year period in our hospital. The average age of patients with iMN was significantly older than those with aMN (54.77 ± 13.01 vs 47.13 ± 16.16, P < .001). Around 75 patients (27%) were smokers in iMN patients, and 111 patients (37.1%) in aMN patients (P = .009). The mainly clinical manifestation of these 2 groups was nephrotic syndrome (61.5% in iMN group vs 58.4% in aMN group), but there were more patients accompanied with nephritis syndrome in aMN group than iMN group (17.1% vs 6.1%, P < .001). The immunofluorescence of renal biopsy showed "full house" in aMN group; and IgG subclass of the glomeruli demonstrated IgG4 (90.4%) was commonest in iMN group, but IgG1 (94.6%) in aMN group. 51 (48.1%) patients with iMN were detected positive PLA2R antibody in their serum, and 93 (57.4%) in aMN patients (P = .168). The patients with positive PLA2R antibody had higher positive rate of microscopic hematuria and urinary protein, lower albumin.The aMN patients are younger, higher smoking rate, its main clinical manifestation is nephrotic syndrome, but more of them accompanied with nephritis syndrome than those in iMN patients. Serum PLA2R antibody could not distinguish aMN from iMN. aMN could be a special glomerular disease in China, and need a further research on a larger scale.

Stability of important antibodies for kidney disease: pre-analytic methodological considerations

Background

The importance of circulating antibodies as biomarkers of kidney disease has recently been recognized. However, no study has systematically described the methodology of sample preparation and storage regarding antibodies as biomarkers of kidney disease. It remains unknown whether repetitive freeze-thaw cycles, physical disturbances, storage at different temperatures or for different periods of time, or haemolytic or turbid serum samples affect antibody measurements. The aim of this study was to investigate the stabilities of antibodies associated with kidney disease in serum samples under various relevant clinical and research conditions.

Methods

We stored serum samples in the following different conditions: repetitive freeze-thaw cycles (1, 6 or 12 times), long-term storage (7 or 12 months at -80 °C), physical disturbance (1 or 8 h), and storage at 4 °C (1, 3 or 6 weeks) and room temperature (1 or 7 days). The stabilities of the anti-phospholipase A2 receptor (anti-PLA2R), anti-glomerular basement membrane, anti-myeloperoxidase and anti-proteinase 3 antibodies were evaluated with enzyme-linked immunosorbent assays (ELISA).

Results

We found that repetitive freeze-thaw cycles did not have a significant effect on the stabilities of the abovementioned antibodies in clear serum samples. The ELISA readings of haemolytic and turbid serum samples tended to increase and decrease, respectively. Neither long-term storage at -80 °C nor physical disturbance had a significant effect on anti-PLA2R antibody stability in sealed serum samples. The concentrations of most of these antibodies increased in unsealed serum samples that were stored at 4 °C for more than 6 weeks or at room temperature for more than 7 days.

Discussion

Our findings revealed that the abovementioned circulating antibodies that are used as biomarkers for kidney disease had stable physicochemical properties, structures and immunoreactivities such that they were not influenced by repetitive freeze-thaw cycles, physical disturbances or long-term storage at -80 °C. However, the ELISA readings tended to change for haemolytic, turbid and unsealed serum samples.

The Genetic and Environmental Factors of Primary Membranous Nephropathy: An Overview from China

Background

Primary membranous nephropathy (pMN) is the most common cause of nephrotic syndrome in adults. The discovery of the 2 autoantigens, M-type phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing 7A (THSD7A), has defined pMN as an autoimmune disease. A remarkable increase in the frequency of pMN in primary glomerular disease was witnessed in China. The genetic and environmental contributors to disease susceptibility have been investigated in these patients.

Summary

We reviewed recent publications in genetic and environmental studies of pMN, focusing mainly on those undertaken in China. Following a genome-wide association study, the gene-gene interaction between the 2 most significant risk factors, PLA2R1 and DQA1, was validated in Chinese patients with MN. Fine mapping on human leukocyte antigen (HLA) locus found that DRB1*1501 and DRB1*0301 were risk alleles. Three amino acid residues on positions 13 and 71 of HLA-DRβ1 chain may confer the susceptibility to pMN by presenting T-cell epitopes on PLA2R. Another study found that DRB3*0202 was the most likely culprit allele for the signal at DRB1*0301. One environmental risk factor for pMN has been identified as the long-term exposure to high levels of PM_2.5 in Chinese patients with MN. Each 10 μg/m³ increase in PM_2.5 concentration was associated with 14% higher odds for pMN in the regions with PM_2.5 above 70 μg/m³.

Key Message

A gene-environment interaction is suspected as an underlying mechanism for the increasing trend of pMN in China.

Membranous Nephropathy and Anti-Podocytes Antibodies: Implications for the Diagnostic Workup and Disease Management

The discovery of circulating antibodies specific for native podocyte antigens has transformed the diagnostic workup and greatly improved management of idiopathic membranous nephropathy (iMN). In addition, their identification has clearly characterized iMN as a largely autoimmune disorder. Anti-PLA2R1 antibodies are detected in approximately 70% to 80% and anti-THSD7A antibodies in only 2% of adult patients with iMN. The presence of anti-THSD7A antibodies is associated with increased risk of malignancy. The assessment of PLA2R1 and THSD7A antigen expression in glomerular immune deposits has a better sensitivity than measurement of the corresponding autoantibodies. Therefore, in the presence of circulating anti-podocytes autoantibodies and/or enhanced expression of PLA2R1 and THSD7A antigens MN should be considered as primary MN (pMN). Anti-PLA2R1 or anti-THSD7A autoantibodies have been proposed as biomarkers of autoimmune disease activity and their blood levels should be regularly monitored in pMN to evaluate disease activity and predict outcomes. We propose a revised clinical workup flow for patients with MN that recommends assessment of kidney biopsy for PLA2R1 and THSD7A antigen expression, screening for circulating anti-podocytes antibodies, and assessment for secondary causes, especially cancer, in patients with THSD7A antibodies. Persistence of anti-podocyte antibodies for 6 months or their increase in association with nephrotic proteinuria should lead to the introduction of immunosuppressive therapies. Recent data have reported the efficacy and safety of new specific therapies targeting B cells (anti-CD20 antibodies, inhibitors of proteasome) in pMN which should lead to an update of currently outdated treatment guidelines.

Circulating Antibodies against Thrombospondin Type-I Domain-Containing 7A in Chinese Patients with Idiopathic Membranous Nephropathy

BACKGROUND AND OBJECTIVES

Thrombospondin type-I domain-containing 7A (THSD7A) was recently identified as the target antigen in about 10% of patients with M-type phospholipase A2 receptor (PLA2R)-negative membranous nephropathy in European and North American populations. The prevalence of THSD7A in other populations and their clinical associations deserve further clarification.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Immunofluorescence assay was performed to investigate anti-THSD7A antibodies in 578 consecutive patients with biopsy-proven idiopathic membranous nephropathy, 114 patients with secondary membranous nephropathy, 64 disease controls, and 20 healthy controls. Glomerular expression of THSD7A antigen was examined by immunohistochemistry. Anti-PLA2R antibodies and glomerular PLA2R expression were also screened.

RESULTS

Among the 578 patients with idiopathic membranous nephropathy, 12 (2%) patients were identified as THSD7A-positive: ten patients were THSD7A-positive alone, which accounted for 16% (ten of 64) of PLA2R-negative patients; two patients were dual-positive for both anti-THSD7A and anti-PLA2R antibodies and showed enhanced expression of both antigens colocalized in glomeruli. Among the 114 patients with secondary membranous nephropathy, one among 44 (2%) patients with cancer had anti-THSD7A antibodies, whereas 18 of 44 (41%) had anti-PLA2R antibodies. No anti-THSD7A antibody was detected in other disease controls or healthy individuals. Clinical features were comparable between the patients with and without THSD7A. During follow-up, two patients who achieved remission had a clearance of circulating antibodies against THSD7A, whereas antibodies increased in parallel with proteinuria in a patient with a relapse.

CONCLUSIONS

THSD7A-associated membranous nephropathy has a low prevalence in Chinese patients. The double-positive patients suggest dual autoimmune responses.

A comprehensive narrative review of diagnostic biomarkers in human primary membranous nephropathy

Membranous nephropathy (MN) is relatively major cause of nephrotic syndrome in adults which is recognized as an organ-specific autoimmune disease. The etiology of most cases is idiopathic, whereas the secondary MN is caused by systemic autoimmune diseases, infections, medications and malignancies. The idiopathic disease is developed by the formation of sub-epithelial immune complex deposits most likely due to binding the circulating auto-antibodies to intrinsic antigen on podocytes. The major auto antibody is the anti-phospholipase A2 receptor (anti-PLA2R), however, it is not enough sensitive. Several attempts for diagnostic biomarker identification by modern analytical technologies have been devoted recently. This article reviews the biomarker candidates for primary type of MN that are detected by different approaches on human subjects.

Recent Progress in Deciphering the Etiopathogenesis of Primary Membranous Nephropathy

Primary membranous nephropathy (MN) is the leading cause of nephrotic syndrome in adults. Discovery of several antibodies has contributed to an increased understanding of MN. Antibodies against the M-type phospholipase A2 receptor (PLA2R) are present in 50-100% with primary MN and are associated with a lower frequency of spontaneous remission. High levels are linked with a higher probability of treatment resistance, higher proteinuria, and impaired renal function, as well as a more rapid decline of kidney function during follow-up. Immunologic remission precedes reduction of proteinuria by months. Pretransplant evaluation of PLA2R antibodies is warranted to predict recurrence of disease following renal transplantation. Several risk alleles related to the PLA2R1 gene and within the HLA loci have been identified, whereas epitope spreading of PLA2R may predict treatment response. More recently, thrombospondin type 1 domain-containing 7A (THSD7A) antibodies have been discovered in primary MN. Several other rare antigens have been described, including antibodies against neutral endopeptidase as a cause of antenatal MN and circulating cationic bovine serum albumin as an antigen with implications in childhood MN. This review focuses on the progress with a special focus on diagnostic accuracy, predictive value, and treatment implications of the established and proposed antigens.

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.