The M-type phospholipase A2 receptor (PLA2R1) was identified recently as a specific target antigen in idiopathic membranous nephropathy. However, the influence of different sample preparation techniques on the immunostaining of PLA2R1 is unclear. Previous studies have identified IgG4 as the dominant subclass of PLA2R1 antibodies. However, it remains unclear whether the IgG subclass profiles of the glomerular immune complexes of PLA2R1-positive and -negative idiopathic membranous nephropathy cases are similar. To address these questions, we conducted the present study of 58 idiopathic membranous nephropathy cases. The PLA2R1 positivity rate for the paraffin-embedded sections was 61%, whereas that for the frozen sections was 65%. Nonspecific background staining was observed in the frozen sections. Discrepancies between different sample preparations occurred in three cases (6%); two cases were PLA2R1-positive in paraffin sections and PLA2R1-negative in frozen sections and one case was PLA2R1-negative in paraffin sections and PLA2R1-positive in frozen sections. Regarding the IgG subclass profile, 89% of the PLA2R1-positive cases demonstrated the IgG4-dominant/codominant phenotype versus 31% of the PLA2R1-negative cases (p < 0.001). Clinical characteristics and pathological findings did not significantly differ between PLA2R1-positive and -negative cases. In summary, the PLA2R1 immunofluorescence results were not affected by the different sample preparation techniques, although paraffin-embedded sections were preferred for the histological detection of PLA2R1 because of the nonspecific background staining observed in frozen sections. The observed lower frequency of the non-IgG4-dominant/codominant phenotype in PLA2R1-negative idiopathic membranous nephropathy cases may suggest that there are heterogeneous subgroups of this disease.

BackgroundProliferative glomerulonephritis with monoclonal IgG deposits (PGNMID) is a form of renal involvement by monoclonal IgG deposits that was found in mesangial, subendothelial or subepithelial regions. The distribution of glomerular deposits was completely different from that in monoclonal immunoglobulin deposition disease. PGNMID is reported to be rarely associated with a hematological malignancy. Previously, only five cases of PGNMID with multiple myeloma have been reported. However, the pathogenic relationship between PGNMID and multiple myeloma was unclear because a detailed description was not provided. We report that a patient with PGNMID associated with multiple myeloma was treated with bortezomib and dexamethasone and underwent the second renal biopsy after treatment, showing that chemotherapy was effective for PGNMID clinically and pathologically.Case presentationA 75-year-old man presented with progressive leg edema, had nephrotic range proteinuria, hypoalbuminemia, moderate renal failure, and occult blood in his urine. Electrophoresis results showed serum and urinary monoclonal spikes of IgGκ type immunoglobulin. A renal biopsy specimen showed lobular mesangial proliferation with mesangiolysis, glomerular micro-aneurysm, and endocapillary hypercellularity. Immunofluorescence results revealed strong granular capillary and mesangial staining for IgG1, C3 and κ light chain in glomeruli without tubular deposits of any immunoglobulin. Electron microscopy also showed dense granular deposits in subendothelial and mesangial areas. PGNMID associated with multiple myeloma (IgGκ type) was diagnosed on the basis of a subsequent bone marrow examination. Bortezomib and dexamethasone therapy significantly reduced proteinuria and elevated serum albumin level. Eight months later, the second renal biopsy showed no active lesions and that the IgG1 and κ light chain deposits had drastically disappeared.ConclusionsThis is the first case of PGNMID with multiple myeloma successfully treated with bortezomib and dexamethasone in which comparative renal biopsies were performed before and after treatment. Our findings suggest the pathogenesis of PGNMID and therapeutic options for PGNMID.

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MyoR was originally identified as a transcriptional repressor in embryonic skeletal muscle precursors, but its function in adult kidney has not been clarified. In this study, we tried to clarify the functional role of MyoR using MyoR−/− mice. Cisplatin induced a significantly higher degree of severe renal dysfunction, tubular injury, and mortality in MyoR−/− mice than in wild-type mice. The injection of cisplatin significantly increased the number of apoptotic cells in the kidney tissues of MyoR−/− mice, compared with that in wild-type mice. To clarify the mechanism of severe cisplatin-induced damage and apoptosis in MyoR−/− mice, we focused on the p53 signaling pathway and bone morphogenic protein-7 (BMP-7). Treatment with cisplatin significantly activated p53 signaling in cultured renal proximal tubular epithelial cells (RTECs) in both wild-type and MyoR−/− mice, but no significant difference between the groups was observed. The injection of cisplatin significantly increased the expression of BMP-7 in the kidney tissues of wild-type mice, but no increase was observed in the MyoR−/− mice. Treatment with cisplatin significantly increased the expression of BMP-7 in cultured RTECs from wild-type mice but not in those from MyoR−/− mice. Moreover, treatment with recombinant BMP-7 rescued the cisplatin-induced apoptosis in RTECs from MyoR−/− mice. Taken together, our results demonstrate a new protective role of MyoR in adult kidneys that acts through the regulation of BMP-7.

Calcification of the thoracic aorta determined by three-dimensional computed tomography predicts cardiovascular complications in patients on hemodialysis.