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Background: Complement activation is thought to be pathologically important in IgA nephropathy (IgAN). Although C3 deposition in the mesangium is found in IgAN, the origin of C3 is not clear. We recently demonstrated intraglomerular C3 synthesis in the human kidney; however, the activation and pathological role of locally synthesized C3 remains unclear. Here we performed nonradioactive in situ hybridization for C3 mRNA and immunohistochemistry for C3 and its activation products, such as C3d and membrane attack complex (MAC), to determine whether locally produced C3 in glomeruli was activated in IgA nephropathy. Methods: Renal samples from 14 patients with IgAN and 5 with minimal change nephrotic syndrome (MCNS) were examined. Uninvolved portions of surgically removed kidneys with tumors served as normal controls. Results: C3 mRNA was not detected in glomeruli in control tissue and MCNS, but was strongly expressed in resident glomerular cells of IgAN, including mesangial cells, glomerular epithelial cells and the cells of Bowman’s capsule. Examination of serial sections disclosed that more than 70% of cells positive for C3 mRNA were also stained for C3 protein, C3d, and MAC. Double staining for in situ hybridization and immunohistochemistry also revealed that those C3 mRNA signals were present in intraglomerular cells positive for C3. The expression of C3 mRNA and MAC in glomeruli correlated significantly with the degree of mesangial matrix expansion. Conclusions: Our results demonstrated that locally synthesized C3 is activated in the glomeruli of IgAN and that its expression correlated with the severity of mesangial matrix expansion. These findings suggest that activation of C3 may be involved in tissue injury in IgAN through the formation of membrane attack complex.Copyright © 2001 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

SUMMARY:Laminin is implicated in cell migration, remodelling of the extracellular matrix and basement membrane. Therefore, laminin deposition could be of concern in the progression of some renal diseases. In the present study, immunohistochemical and in situ hybridization studies were performed for laminin in IgA nephropathy (IgAN) specimens in order to reveal the importance of laminin deposition for their prognosis. Fifteen patients were used as the stable group who maintained stable renal function for more than 10 years after biopsy. Thirteen patients formed the progressive group who reached end-stage renal failure within 10 years after biopsy. Immunohistochemically, laminin was specifically deposited in damaged glomeruli and strong immunoreactivity was particularly shown in the expanded interstitial area containing infiltrating mononuclear cells. Although the staining score in glomeruli was not significantly different between these two groups (P = 0.181), deposition in the expanded interstitium was extensive and significantly greater in the progressive group (P < 0.01). In situ hybridization revealed that most of the interstitial cells and some of the tubular cells expressed laminin messenger ribonucleic acid. In conclusion, the extent of interstitial laminin deposition was an important prediction of adverse renal outcome. This laminin could be produced by interstitial cells and/or tubular cells. [ABSTRACT FROM AUTHOR]

SUMMARY: It is well established that mesangial cell proliferation plays a major role in glomerular injury and progressive renal injury. The expression of a number of different genes has been reported in proliferative mesangial cells in culture. However, the relevance of these genes to renal injury in general and IgA nephropathy (IgAN) remains to be established. Assessment of gene activity on a global genome-wide scale is a fundamental and newly developed molecular strategy to expand the scope of clinical investigation from a single gene to studying all genes at once in a systematic pattern. Capitalizing on the recently developed methodology of high cDNA array hybridization, the simultaneous expression of thousands of genes in primary human proliferating mesangial cells was monitored and compared with renal tissue of IgAN. Complex [α-33 P]-labelled cDNA targets were prepared from cultured mesangial cells, remnant tissue from five IgAN renal biopsies and four nephrectomies (controls). Each target was hybridized to a high-density array of 18 326 paired target genes. The radioactive hybridization signals were analysed by phosphorimager. Approximately 8212 ± 530 different gene transcripts were detected per target. Close to 5% (386 ± 90 genes) were full-length mRNA human transcripts (HT) and the remainder were expressed sequence tags (EST). Using a relational database, electronic subtraction was performed and matching was carried out to allow identification of 203 HT with shared expression in proliferative mesangial cells and IgAN renal biopsies. In addition hierarchical clustering analysis was performed on the HT of IgAN and controls to establish differential expression profiles of mesangial HT in IgAN and controls. Collectively the presented data constitutes a preliminary renal bioinformatics database of the transcriptional profiles in IgAN. More importantly, the information may help to speed up the discovery of genes underlying human IgAN. [ABSTRACT FROM AUTHOR]

SUMMARY: A comprehensive profile of genes expressed at the mRNA level (transcriptome) in human renal tissue is important for elucidating the pathogenesis and treatment of IgA nephropathy (IgAN). The recent development of complementary DNA (cDNA) array hybridization allows the parallel monitoring of thousands of genes expressed in renal tissue. High-density cDNA containing 18 326 paired unique human cDNA gene probes were used to quantitatively analyse the expression of genes in renal biopsies of IgAN and controls. Computational analysis was used to cluster genes according to similarity in pattern of gene expression. Through relational database analysis, we determined 1901 genes that were commonly expressed in four selected IgAN renal biopsies and four controls. Further analysis of the expressed genes by self-organizing maps and hierarchical clustering revealed a genomic profile unique to severely affected IgAN patients. These findings represent a comprehensive preliminary molecular index of genes transcribed in IgAN. More importantly, this molecular approach may accelerate the discovery of pathogenic mechanisms underlying the most common form of glomerulonephritis worldwide. [ABSTRACT FROM AUTHOR]

Expression of endothelial and inducible nitric oxide synthase in human glomerulonephritis. The presence of nitric oxide (NO) in the kidney has been implicated in the pathogenesis of human glomerulonephritis. However, the exact type of glomerular cells that express NO synthase (NOS) and the NOS isoform involved in the local production of NO has not been identified in the human diseased kidney. We examined the expression of three isoforms of NOS, inducible NOS (iNOS), endothelial NOS (eNOS) and brain NOS (bNOS) in the renal tissue of patients with IgA nephropathy (IgAN, N = 10), lupus nephritis (LN, N = 5), membranous nephropathy (MN, N = 5) and minimal change nephrotic syndrome (MCNS, N = 5). Sections were immunostained and the correlation between the expression of each NOS and the degree of glomerular injury in that section was also examined. Normal portions of surgically resected kidneys served as controls. eNOS was present in glomerular endothelial cells and endothelium of cortical vessels in the control and diseased kidneys. iNOS was localized in mesangial cells, glomerular epithelial cells and infiltrating cells in the diseased glomeruli, whereas immunostaining for iNOS was hardly detected in control kidneys. In addition, the expression pattern of eNOS in each glomerulus was the reverse of that of iNOS. In IgAN and LN, the extent of staining for eNOS correlated negatively with the degree of glomerular injury, while the extent of staining for iNOS correlated positively with the degree of glomerular injury in the same tissues. bNOS was not detected in normal or nephritic glomeruli. Our results indicate the presence of a NO pathway in human diseased kidney, and suggest that NO derived from eNOS and iNOS may be involved in the progression of renal diseases and that NO derived from each NOS may play an important role in different way in human inflamed glomeruli.*. [ABSTRACT FROM AUTHOR]