| Part I The Relationship between the Expressions of Serum PLA2R Autoantibody and Renal PLA2RObjective:Idiopathic membranous nephropathy is one of the main causes of primary nephrotic syndrome in adults. The pathogenesis remains unknown, and the diagnosis and treatment are controversial over the decades. In recent years, circulating autoantibody of M-type phospholipase A2 receptor has been discovered in the serum of approximately 70% IMN patients, and PLA2R was regarded as a main antigen in IMN. However, the correlation between the expressions of autoantibody and antigen is not clear, meanwhile little was understood about how each of them influences the features of IMN. The purpose of this part is to analyze the correlation between the expressions of serum anti-PLA2R autoantibody and renal PLA2R. We will also assess the relationship between autoantibody expression and the severity of IMN.Method:26 adult patients diagnosed of IMN clinically and pathologically were recruited for the study. The expression of PLA2R in renal biopsy specimens bedded in paraffin was observed through microwave repair and immunofluorescence. The HEK293 cells transfected with PLA2R cDNA were incubated with the patients’serum samples collected by the time of renal biopsy. The expression of PLA2R autoantibodies in serum were observed with indirect immunofluorescence. The correlation between serum PLA2R antibody and renal PLA2R expression was analyzed and the serum creatinine, albumin and urine protein were compared between patients with or without antibody expression.Results:22(84.6%) of 26 IMN patients had PLA2R detected in the kidney.13 patients were found serum autoantibody positive, who accounted for 59.1% of renal PLA2R-positive patients.4 cases presented with both negative in serum PLA2R antibody and renal PLA2R expression. The serum creatinine of the patients with or without serum PLA2R antibody expression were 83 (59-103) μmol/L and 77 (61-87) μmol/L, and 24h urine protein were 7.84 (3.39-13.30) g/24h and 4.66 (4.03-7.71) g/24h. No statistically significant difference was observed (p>0.05). Serum albumin was significantly higher in antibody-negative patients than that in antibody-positive patients(21.2 ± 4.8 g/L vs.25.7 ±5.1 g/L, p= 0.028). In order to exclude the potential impact of renal PLA2R on clinical manifestations of IMN, we compare the clinical indexes only in patients with renal PLA2R expression. There were still no statistical difference in serum creatinine and 24h urine protein between patients with or without serum autoantibody(85.4 ± 27.Oμmol/L vs.74.7 ± 12.7μmol/L,7.84 (3.39-13.31) g/24h vs.4.66 (4.37-6.13) g/24h,p>0.05). Serum albumin was still significantly higher in antibody-negative patients than that in antibody-positive patients(21.2 ± 4.8 g/L vs.25.3 ± 3.4 g/L, p= 0.036).Conclusion:The expression of serum PLA2R autoantibody and renal PLA2R is not closely matched in IMN patients. All of the antibody-positive patients were found positive in renal PLA2R expression, while some of the renal-PLA2R-positive patients have no antibody detected in their serum. Serum PLA2R antibody expression in IMN patients is associated with hypoalbuminemia, which is independent of the expression of renal PLA2R, may reflect the severity of the disease.Part II The Clinical Features of PLA2R-Related Idiopathic Membranous NephropathyObjective:It remains unclear about the impact of renal PLA2R on the pathogenesis and clinical manifestations of idiopathic membranous nephropathy. According to the expression of PLA2R in renal tissues, IMN could be categorized into PLA2R-related IMN and non-PLA2R-related IMN. The purpose of this part is to investigate the clinical characteristics and prognostic features of PLA2R-related IMN and assess the clinical value of renal PLA2R for the diagnosis, prognosis and drug selection for IMN.Method:This study was a retrospective cohort study.231 adult patients diagnosed of IMN in Huashan Hospital and Wuxi People’s Hospital were recruited for the study. The expression of PLA2R in renal biopsy specimens bedded in paraffin was observed through microwave repair and immunofluorescence.186 cases from the above patients whose baseline clinical data was respectively well recorded were recruited for the idiopathic membranous nephropathy patient cohort. Comparative analysis of the baseline clinical features were conducted between PLA2R-related IMN and non-PLA2R-related IMN. For the patients who have a follow-up period longer than 90 days, the features of their clincal courses, remissions and sensitivity to the immunosuppresants were assessed and compared. We also had 29 IMN patients’ blood sample tested for the genotypes at 3 single-nucleotide polymorphisms, including rs4664308, rs35771982 on PLA2R and rs2187668 on HLA-DQA1.Results:The prevalence rate of PLA2R expression in IMN was 81.8%. Baseline clinical features were compared between PLA2R-related IMN and non-PLA2R-related IMN in our IMN cohort, including serum creatinine (74 (58-92) vs.68(55-85)μmol/L), albumin (22.8 ± 6.1 g/L vs.25.0 ± 9.1 g/L) and 24h urine protein (4.46 (2.75-5.85) g/24h vs.3.39 (1.78-6.02) g/24h). The two groups did not show any statistical difference in those clinical indexes (p>0.05). Abnormalities in immunological indexes were more common in non-PLA2R-related IMN(31.7%) than in PLA2R-related IMN(8.3%, p=0.000). PLA2R-related IMN patients tend to present with higher levels of uric acid (0.379 ± 0.085 mmol/L vs.0.332 ± 0.074 mmol/L, p=0.001), lower conjucted bilirubin (1.5 (1.1-2.5) μmol/L vs.2.0 (1.2-3.3) μmol/ L,p=0.020), more severe hyperlipidemia (total cholesterol, triglycerides, and APO-B were 7.6 ± 2.4 mmol/L,2.2 (1.6-3.1) mmol/L and 1.38 (0.98-1.69) g/L vs.6.8 ± 2.3mmol/L,1.7 (1.2-2.9) mmol/L and 1.05 (0.86-1.46) g/L,p<0.05), higher C4 (0.26 (0.21-0.29) g/L vs.0.21 (0.17-0.27) g/L,p=0.004), more red blood cell count in urine (53.8 (24.9-107.4)/μL vs.21.1 (9.6-76.0)/μL,p=0.006) when compared with non-PLA2R-related IMN patients. At 6th month after renal biopsy, non-PLA2R-related IMN patients achieved a higher rate of complete remission than PLA2R-related IMN patients (p=0.042), however such difference disappears at the 12th month.; The remissions of PLA2R related IMN patients are not as good as the non-PLA2R-related patients after 3 months of applying immunosuppressants(p=0.004), but become similar after 6 months(p> 0.05). Cyclophosphamide showed better effectiveness in non-PLA2R-related IMN patients by the 6th month of application (p=0.017). Our study revealed no difference of therapeutic efficacy between CTX and CNIs during initial therapy. There was no difference of the genotypes on the 3 SNPs between PLA2R-related IMN and non-PLA2R-related IMN.Conclusion:Our study showed no difference in serum creatine, albumin and 24h urine protein between PLA2R-related IMN and non-PLA2R-related IMN, however the former is characterized with more severe hyperlipidemia, higher uric acid, lower conjucted bilirubin, higher C4 and more hematuria when compared with the latter. Abnormalities in immunological indexes were more common in non-PLA2R-related IMN than in PLA2R-related IMN, which indicates a potential difference in the pathogenesis. During immunosuppressive intial therapy, PLA2R-related IMN respond more slowly to the drugs but the remissions of the two diseases tend to become similar. Non-PLA2R-related IMN is more sensitive to CTX than PLA2R-related IMN. The efficacies of CTX and CNIs seem to be equal and both can be applied to the IMN patients. |
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