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

Phospholipase A2 Receptor Antibodies and Clinical Prognosis in Patients with Idiopathic Membranous Nephropathy: An Updated Systematic Review and Meta-Analysis

BACKGROUND

Idiopathic membranous nephropathy (IMN) is the most common form of primary nephrotic syndrome in adults. Antibodies against the M-type phospholipase A2 receptor (PLA2R-ab) are considered as diagnostic biomarkers of IMN.

OBJECTIVE

Here, we performed an updated meta-analysis to assess the diagnostic value of PLA2R-ab for clinical remission in IMN patients.

METHOD

PubMed, Embase, and Cochrane databases were searched for relevant studies published before September 2022. Odds ratios and corresponding 95% confidence intervals were determined using a fixed or random effects model. The heterogeneity among studies was explored by subgroup analysis.

RESULTS

Sixteen studies involving 1,761 IMN participants were included. There were significant differences between PLA2R-ab (+) and PLA2R-ab (-) patients in terms of complete remission (CR) and spontaneous remission. The rates of partial remission (PR) and relapse were similar between the two groups. Patients with PLA2R-ab (-) were at a higher CR rate when treated with a calcineurin inhibitor or a treatment course for 3 months and 6 months, while the spontaneous remission rate was higher in PLA2R-ab seronegative patients from Asia. However, the CR and spontaneous remission rate only significantly declined in IMN patients with the highest titer, but not a middle titer, when compared to those with the lowest titer.

CONCLUSION

In contrast with previous meta-analyses, our results verified that PLA2R-ab can likely predict CR and spontaneous remission in IMN patients, instead of PR and relapse. Race, immunosuppressive agents, and duration of treatment may affect the prognostic value of PLA2R-ab. Considering that the remission rate of IMN patients with a middle level of PLA2R-ab was not different from that of patients with the lowest level, a proper cut-off value of PLA2R-ab for prognosis should be clarified.

The Value of Peripheral Blood Cell Ratios in Primary Membranous Nephropathy: A Single Center Retrospective Study

Background

Primary membranous nephropathy (PMN) is a common cause of nephrotic syndrome in adults. Forty percent of the patients continue to progress and eventually develop into chronic renal failure. Although phospholipase A2 receptor (PLA2R) is the major antigen of PMN, the clinical features do not often parallel with the antibody titers. Therefore, it is significant to find relative credible markers to predict the treatment response.

Methods

One hundred and eighteen PMN patients were recruited. The response to treatment was defined as ALB≥30g/L at 6 months and complete remission (CR) or not at the end of the follow-up. Renal outcome endpoint was defined as 50% or more Cr increase at the end.

Results

The patients with poor treatment effects had numerically higher platelet-lymphocytes ratio (PLR). For patients with CR or not, the difference was near to statistic significant (P=0.095). When analyzing CR or not, the fitting of the binary logistic regression model including both PLA2R Ab titer and PLR (Hosmer-Lemeshow test: χ ²=8.328, P = 0.402; OR (PLA2R Ab titer) = 1.002 (95% CI 1.000-1.004, P = 0.042); OR (PLR) = 1.006 (95% CI 0.999-1.013, P = 0.098)) was markedly better than that with only PLA2R Ab titer (Hosmer-Lemeshow test: χ ²=13.885, P = 0.016). The patients with renal function deterioration showed significantly higher monocyte-lymphocyte ratio (MLR) (0.26 (0.22-0.31) vs 0.18 (0.13-0.22), P = 0.012).

Conclusion

PMN patients with poor treatment response tended to have higher PLR at the time of renal biopsy, and a higher MLR was associated with poor renal outcomes. Our findings suggested that PLR and MLR might be used to predict treatment efficacy and prognosis for PMN patients, respectively.

Correlation of Body Mass Index with Clinicopathologic Parameters in Patients with Idiopathic Membranous Nephropathy

OBJECTIVE

To investigate the association between body mass index (BMI) and clinicopathologic parameters in patients with idiopathic membranous nephropathy (IMN).

METHODS

This study was retrospective and included patients with biopsy-proven IMN from 2018 to 2021 in Hebei General Hospital. Patients were categorized into two groups based on BMI. Clinical and histopathologic data were analyzed at the time of renal biopsy. Pathological data included immunofluorescence staining, glomerulosclerosis (GS, 0-2), mesangial cell proliferation (MCP, 0-1), tubular atrophy (TA, 0-1), interstitial fibrosis (IF, 0-1), vascular wall thickness (VWT, 0-1) and a combination score (GMTIV) graded from 0 to 5.

RESULTS

Our study revealed that the obese group had a higher prevalence of hypertension and diabetes than the overweight/normal weight group (P=0.001, P=0.002). Systolic blood pressure (P=0.005), diastolic blood pressure (P<0.001), haemoglobin (P=0.006), triglycerides (P<0.001), serum uric acid (P=0.05), 24 h urine proteinuria concentration (UP) (P=0.012), MCP (P=0.042), IF (P=0.033), and GMITV (P=0.033) score were higher in obese group compared to the other group, while the high-density lipoprotein-cholesterol (P=0.034) and immunoglobulin A deposition score (P=0.005) were lower. Factors significantly associated with UP were the ratio of lymphocyte count to white blood cell count, serum pre-albumin, immunoglobulin G, microscopic hematuria, anti-phospholipase A2 receptor (anti-PLA2R), C3 deposit on multivariable analysis (adjusted R ²=0.343). Binary logistic regression analysis illustrated that MCP was correlated to BMI (OR=2.528, P=0.036). Ordinal logistic regression analysis demonstrated that GMTIV was associated with BMI (OR=1.114, P=0.010) and C3 deposit (OR=1.655, P=0.001).

CONCLUSION

High BMI was associated with MCP and GMTIV score in IMN patients. Obesity may play an essential role in mesangial lesions of IMN. This study emphasized the relation between BMI and histological parameters under the universal usage of anti-PLA2R antibodies for diagnosis and prognosis in IMN.

PLA2R Immunohistochemistry Staining in Membranous Glomerulopathy: A Challenging Stain to Interpret But a Potentially Useful Diagnostic Tool

Circulating autoantibodies to phospholipase A2 receptor (PLA2R-Ab) are detected in >70% of patients with primary membranous glomerulonephritis (MGN). Detection of PLA2R antigen in renal tissue, with immunohistochemistry (PLA2R IHC), strongly correlates with serum PLA2R-Ab, although it is more sensitive. As PLA2R IHC in literature has no univocal interpretation, we suggest reliable criteria for a standard approach for the assessment of immunostaining for differential diagnosis between primary and secondary MGN. We analyzed PLA2R IHC expression in 40 biopsies of patients with MGN and serum PLA2R-Ab titer at the time of biopsy. We carefully evaluated, at high magnification, the immunostaining pattern and distribution, regardless of intensity, in capillary loops, mesangium, and podocytes of all glomeruli.We defined, adopting this approach, positive stain when a granular pattern, coarse and/or fine, diffuse or focal, and global or segmental were observed. Negative stain was defined by mesangial staining, when there was a dirty pattern, or a peripheral staining of capillary loops with a smoky linear pattern. Podocytes showed homogenous cytoplasmatic stain both in positive and negative cases and in external negative controls. We found PLA2R IHC and serum PLA2R-Ab positivity in early-middle stage MGN compared with advanced stage more frequently. Correct stratification of patients with MGN needs PLA2R-Ab detection in serum and renal tissue. PLA2R IHC test, although a challenging stain, can be an easy diagnostic tool but requires reliable interpretation keys for a standard approach to the assessment of immunostaining.

Nomogram to predict the progression of patients with primary membranous nephropathy and nephrotic syndrome

Background

The outcome of patients with primary membranous nephropathy (pMN) who present with nephrotic syndrome (NS) is variable and difficult to predict. The goal of this study was to develop a nomogram to predict the risk of progression for specific individuals.

Methods

This retrospective study involved biopsy-proven patients with pMN and NS treated between January 2012 and June 2018. The primary outcome of our investigation was progression, defined as a reduction of estimated glomerular filtration rate (eGFR) that was equal to or over 20% compared with baseline at the end of follow-up or the onset of end-stage renal disease (ESRD). We used backwards stepwise logistic regression analysis to create a nomogram to predict prognosis. The model was validated internally using bootstrap resampling.

Results

A total of 111 patients were enrolled. After a median follow-up of 40.0 months (range 12–92 months), 18.9% (21/111) patients showed progression. Backwards stepwise selection using the Akaike information criterion (AIC) identified the following four variables as independent risk factors for progression, which were all used in the nomogram: age ≥ 65 years [odds ratio (OR) 7.004; 95% confidence interval (CI) 1.783–27.505; p = 0.005], Ln (sPLA2R-Ab) (OR 2.150; 95% CI 1.293–3.577; p = 0.003), Ln (proteinuria) (OR 5.939; 95% CI 1.055–33.436; p = 0.043) and Ln (Uα1m/Cr) (OR 2.808; 95% CI 1.035–7.619; p = 0.043). The discriminative ability and calibration of the nomogram revealed good predictive ability, as indicated by a C-index of 0.888 (95% CI 0.814–0.940) and a bootstrap-corrected C-index of 0.869; calibration curves were also well fitted. A receiver operating characteristic (ROC) curve for the nomogram score revealed significantly better discrimination than each of the three risk factors alone, including Ln (sPLA2R-Ab) [area under the curve (AUC) 0.769], Ln (proteinuria) (AUC 0.653) and Ln (Uα1m) (AUC 0.781) in the prediction of progression (p < 0.05). The optimal cutoff value of the nomogram score was 117.8 with a positive predictive value of 44.4% and a negative predictive value of 98.5%.

Conclusion

The nomogram successfully achieved good predictive ability of progression for patients with pMN who present with NS. It can therefore help clinicians to individualize treatment plans and improve the outcome of pMN.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11255-021-02859-x.

Mechanisms of Primary Membranous Nephropathy

Membranous nephropathy (MN) is an autoimmune disease of the kidney glomerulus and one of the leading causes of nephrotic syndrome. The disease exhibits heterogenous outcomes with approximately 30% of cases progressing to end-stage renal disease. The clinical management of MN has steadily advanced owing to the identification of autoantibodies to the phospholipase A2 receptor (PLA2R) in 2009 and thrombospondin domain-containing 7A (THSD7A) in 2014 on the podocyte surface. Approximately 50–80% and 3–5% of primary MN (PMN) cases are associated with either anti-PLA2R or anti-THSD7A antibodies, respectively. The presence of these autoantibodies is used for MN diagnosis; antibody levels correlate with disease severity and possess significant biomarker values in monitoring disease progression and treatment response. Importantly, both autoantibodies are causative to MN. Additionally, evidence is emerging that NELL-1 is associated with 5–10% of PMN cases that are PLA2R- and THSD7A-negative, which moves us one step closer to mapping out the full spectrum of PMN antigens. Recent developments suggest exostosin 1 (EXT1), EXT2, NELL-1, and contactin 1 (CNTN1) are associated with MN. Genetic factors and other mechanisms are in place to regulate these factors and may contribute to MN pathogenesis. This review will discuss recent developments over the past 5 years.

PLA2R antibody, PLA2R rs4664308 polymorphism and PLA2R mRNA levels in Tunisian patients with primary membranous nephritis

BACKGROUND

Primary membranous nephritis (PMN) is an autoimmune disease induced by the deposit of antibodies (Ab) to the phospholipase receptor A2 receptor (PLA2R) on podocytes. In this context, we aimed to assess the relationships between anti-PLA2R Ab, PLA2R rs4664308 SNP, PLA2R mRNA levels and PMN susceptibility and outcome.

METHODS

Sixty-eight PMN patients, 30 systemic lupus erythematosus (SLE) patients with secondary MN and 30 healthy control subjects served for anti-PLA2R Ab measurement by ELISA and PLA2R rs4664308 SNP genotyping by a commercial real-time PCR. Twenty patients with tubulo-interstitial nephritis (TIN) were used as controls for renal PLA2R mRNA quantification in PMN patients from kidney biopsies. PLA2R mRNA quantification was carried-out by real-time PCR after RNA extraction.

RESULTS

Forty-three (63.2%) PMN patients received initial therapy consisting of alternating monthly cycles of corticosteroids and cyclophosphamide. Twelve (17.6%) patients had resistant PMN to initial therapy and were consecutively treated by cyclosporine or tacrolimus. Anti-PLA2R Ab were positive in 54 (79.4%) PMN patients, while all SLE patients and controls were negative, p<0.0001. Moreover, anti-PLA2R Ab levels were significantly higher in PMN patients (134.85 [41.25-256.97] RU/ml) than in SLE patients (3.35 [2.3-4.35] RU/ml) and controls (2 [2-2.3]), p<0.0001. Consequently, a ROC curve showed for 100% specificity a sensitivity of 94.1% at a threshold of 2.6 RU/ml. Besides, Anti-PLA2R antibodies levels were significantly associated to non-remission; p = 0.002. The rs4664308*A wild-type allele was significantly more frequent in PMN patients (0.809) than in controls (0.633) and SLE patients (0.65); p = 0.008, OR [95% CI] = 2.44 [1.24-4.82] and p = 0.016, OR [95% CI] = 2.27 [1.15-4.5], respectively. Renal PLA2R mRNA levels were significantly higher in PMN patients (218.29 [66.05-486.07]) than in TIN patients (22.09 [13.62-43.34]), p<0.0001. Moreover, PLA2R mRNA levels were significantly higher in non-remission patients (fold-factor vs. partial remission = 2.46 and fold-factor vs. complete remission = 12.25); p = 1.56 10E-8. In addition, PLA2R mRNA and anti-PLA2R Ab levels were significantly correlated, Spearman Rho = 0.958, p<0.0001.

CONCLUSION

Anti-PLA2R Ab and renal PLA2R mRNA could be useful markers for PMN outcome predicting. The PLA2R rs6446308 SNP is associated with PMN susceptibility in Tunisians.

Single-nucleotide polymorphism rs4664308 in PLA2R1 gene is associated with the risk of idiopathic membranous nephropathy: a meta-analysis

Although many studies investigated the associations between single-nucleotide polymorphisms (SNPs) in the M-type phospholipase A2 receptor-1 (PLA2R1) gene and susceptibility to idiopathic membranous nephropathy (IMN), some showed inconsistent results. Here, we conducted a meta-analysis examining the associations between PLA2R1 SNPs and IMN susceptibility after systematic searches in the PubMed and Web of Science databases. Our meta-analysis for rs4664308 A>G including 2,542 IMN patients and 4,396 controls in seven studies showed a significant association between the G allele and a lower risk of IMN, as determined using an allelic model (odds ratio, 0.45; 95% confidence interval [0.41–0.50]), an additive model (for GG vs. AA: 0.26; [0.21–0.33]; for AG vs. AA: 0.40; [0.36–0.45]), a dominant model (0.37; [0.34–0.42]) and a recessive model (0.38; [0.31–0.48]). Our meta-analysis also suggested associations between rs3828323, rs35771982, rs3749117 and rs3749119 and IMN susceptibility although high heterogeneities and/or publication biases were observed. We did not study in our meta-analysis, but other studies indicated that high-risk genotype combinations of rs2187668 in the human leucocyte antigen-DQ a-chain 1 gene and rs4664308 in the PLA2R1 gene had even stronger associations and could affect the formation of anti-PLA2R1 antibodies, suggesting these SNPs could be novel therapeutic targets.