Increased rates of polymeric IgA synthesis by circulating lymphoid cells in IgA mesangial glomerulonephritis.

Recently we have described the existence of high levels of polymeric IgA, partially as immune complexes, in the serum and kidney from patients with IgA mesangial glomerulonephritis. As these patients often have macroscopic haematuria, following upper respiratory tract infections, our working hypothesis in this paper was that circulating lymphocytes from secretory tissues after viral stimulus could produce in these patients a large amount of polymeric IgA. To test it, peripheral blood lymphocytes (PBL) from patients and controls were cultured for seven days in the presence or absence of pokeweed mitogen (PWM). In cell culture supernatants immunoglobulin synthesis was measured by RIA and the proportion of polymeric and monomeric IgA was determined on Ultrogel Ac A22 column. There was no difference in spontaneous production of immunoglobulins between patients and controls. On the contrary, the IgA synthetized by PWM-stimulated PBL was significantly higher in patients than in controls. The percentages of IgA with molecular weight between 600,000 and 250,000 after supernate fractionation were significantly higher in patients than in controls. The true nature of polymeric IgA was confirmed by their ability to bind secretory component, the existence of covalent structures, and the decrease of the larger forms of IgA after reduction and alkylation. The percentage of IgA producing cells binding secretory component was significantly higher in patients than in controls (69 +/- 21 versus 44 +/- 27) after seven days of culture. IgM and IgG produced in patient culture were similar to controls. These results show that mitogen stimulated PBL from patients with Berger's disease synthetized a large amount of true polymeric IgA. It is suggested that a similar situation could occur in vivo after viral of other stimuli.     

The role of the mesangial cell in proliferative glomerulonephritis

In 40 patients with a histological diagnosis of proliferative glomerulonephritis the deposition of immunoglobulins, complement (C(3)), and fibrin/fibrinogen has been assessed by immunofluorescence and electron microscopy. The results of such examinations have been correlated with the outcome of the illness.In minor or resolving disease there is usually minor functional impairment, a good response to therapy or spontaneous resolution, the deposition of small amounts of material in glomerular capillary walls, and active mesangial removal. In moderate to marked disease there is initially a moderately severe functional disorder, a good response to therapy, considerable deposition of material in glomerular capillary walls but with less active mesangial regions than in the previous group. In progressive glomerulonephritis there was initial severe functional disorder, poor response to therapy, large amounts of material deposited within capillary walls, and active mesangial regions which were greatly enlarged, containing numerous deposits. In the rapidly progressive group there was severe functional disorder with poor response to therapy, the deposition of only small amounts of material within capillary walls, the lack of any significant mesangial cell reaction, and the formation of epithelial crescents.The results of the study indicate that in proliferative glomerulonephritis following the deposition of material in glomerular capillary loops, the progression of the disease is, to some extent at least, dependent upon the ability of the mesangial cell to remove such material.     

Platelet-derived growth factor expression in mesangial proliferative glomerulonephritis.

Proliferation of mesangial cells and expansion of mesangial matrix are common histologic features of proliferative glomerular disease, a frequent cause of renal failure. Proliferation of glomerular mesangial cells occurs in response to platelet-derived growth factor (PDGF), and these cells release PDGF and express PDGF A and B chain mRNAs. However, all studies relating PDGF to potential changes in glomerular structure and function to date have been performed in vitro. To explore the role of PDGF in proliferative glomerulonephritides, we studied the expression of PDGF in vivo in two animal models of IgA nephropathy with different histologic patterns of glomerular injury: either predominant mesangial proliferation or expansion of mesangial matrix. Increased expression of PDGF and PDGF B-chain mRNA in whole kidneys from diseased mice was demonstrated by immunohistochemical techniques and by solution hybridization assay, respectively. Immunohistochemically, PDGF was localized primarily within the mesangial area of glomeruli and to a much lower extent in interstitium. The increased PDGF expression correlated with the degree of hypercellularity and clinical features of the disease. In addition, PDGF expression was increased in some forms of human glomerulonephritis, characterized by mesangial proliferation. These findings suggest that PDGF may be a major contributor to mesangial cell proliferation seen in proliferative glomerulonephritides.     

The relation of IgM deposition to clinical parameters and histomorphometry in childhood mesangial proliferative glomerulonephritis

We investigated the question of whether IgM deposition causes any difference in the histomorphometry of children with mesangial proliferative glomerulonephritis (MePGN). We retrospectively compared the urinalysis, blood pressure measurements, and serum creatinine levels of children with IgM (+) and IgM (-) MePGN. For histopathological evaluation, the outlines of Bowman's capsules and glomerular tufts of 10 glomeruli were rimmed manually, and the surrounded areas were calculated as pixels. The cells at each tuft of the largest four glomeruli were counted. Bowman's capsular areas, glomerular tuft areas, glomerular cellularities, and the number of cells per tuft area were determined for each patient. There were 24 (M/F: 14/10) patients with MePGN. Twelve of them were IgM (+). Mean age at biopsy was 6.8+/-4.1 years. IgM (+) patients mostly presented with nephrotic syndrome (NS) (n=9) and IgM (-) patients mostly with macroscopic hematuria (n=7). None of the clinical or laboratory findings was statistically different between the groups (p>0.05) except increased NS frequency in IgM (+) patients (p: 0.038). The histomorphometric parameters were similar in both groups (p>0.05). IgM (+) patients with MePGN mostly presented with NS in our study, but their histomorphometric parameters demonstrated no significant difference.     

Immunohistochemical study of tenascin in mesangial proliferative (IgA-negative) glomerulonephritis.

Glomerular and interstitial expression of tenascin was examined by an indirect immunoperoxidase method in renal biopsy specimens from 27 patients with mesangial proliferative (IgA-negative) glomerulonephritis (MesProGN). Histologically normal samples of kidney tissue (n = 10) obtained from patients with renal trauma were used as controls. In patients with MesProGN, expression of tenascin in glomeruli and interstitium was significantly higher as compared with controls. Tenascin was present in mesangial regions and particularly in areas with interstitial damage. Our results confirm that tenascin is present in normal renal tissue and show a strongly positive correlation between glomerular tenascin expression and surface of mesangial areas and between interstitial expression of tenascin and the relative interstitial cortical volume in patients with MesProGN. In addition, there was a significant correlation between intensity of glomerular and interstitial tenascin staining and serum creatinine levels. Our data indicate that tenascin accumulates in glomeruli and interstitium in patients with MesProGN. Therefore, immunohistochemical staining of tenascin may be a useful marker of progression of the disease in this type of glomerulonephritis.     

Focal mesangial proliferative glomerulonephritis in the rat caused by Habu snake venom: the role of platelets.

Platelet aggregates are a prominent early feature in the glomerular lesions of focal mesangial proliferative glomerulonephritis induced by Habu venom. After venom injection the peripheral blood platelet count falls rapidly, and in vitro the venom causes platelet aggregation and release of 5-HT. The role of platelets in this model has been studied in rats depleted of platelets by antiplatelet serum administration. No effect on the early (24 h) glomerular damage was found. Mesangial proliferation which appears 2--3 days after glomerular injury was significantly inhibited in platelet-depleted rats. These results show that platelet activity does not initiate the mesangial injury in this model, but suggest that platelets or their products act as a stimulus to mesangial proliferation.     

Morphometric comparison of the quantity of the mesangial deposits in rebiopsied patients with idiopathic mesangial proliferative glomerulonephritis

We examined 17 patients with idiopathic mesangial proliferative glomerulonephritis (MPG) who had undergone repeated renal biopsies and for whom both light and electron microscopy as well as immunofluorescence microscopy and full clinical data were available. Ultrastructural investigations were carried out by a computer image analysis system to compare quantitatively the area of the mesangial deposits in serially biopsied patients with MPG, and to find out whether this parameter would correlate with the degree of proteinuria. Another purpose of this study was to verify whether the intensity of the glomerular infiltrates of monocytes/macrophages depends on the accumulation of mesangial deposits. Comparisons between the first biopsy and rebiopsy showed that the mean values of the deposit area per mesangial area were significantly decreased at rebiopsy. Similarly, the glomerular infiltrates of monocytes/macrophages were significantly greater at the first biopsy than they were at rebiopsy. At the first biopsy and at rebiopsy, a significant, positive correlation existed between the density of the mesangial deposits and glomerular monocytes/macrophages as well as proteinuria. Glomerular infiltrates of monocytes/macrophages correlated positively with proteinuria in both the first biopsy and rebiopsy groups. In conclusion, this study points out that the density of the mesangial deposits and glomerular infiltrates of monocytes/macrophages were significantly decreased at rebiopsy, as compared with the first biopsy. Cited data and results of the correlative study correspond with the observation that in most of our serially biopsied patients, proteinuria at rebiopsy was significantly lower than that at the initial biopsy, a finding that might explain the clinical improvement in these cases.     

Experimental glomerulonephritis in the mouse associated with mesangial deposition ofautologous ferritin immune complexes.

Mice undergoing prolonged (5 to 8 weeks) immunization with cadium-free feeritin were studied 1 to 32 days following the last ferritin injection. Urine protein was measured and renal tissue examined by light, immunofluorescence, and electron microscopy. Immunized animals developed significant proteinuria and circulating antibody to ferritin.by light microscopy, proetinuric animals had a proliferative glomerular lesion with mesangial hypercellularity and martrix increase, focal and segmental necrosis, fibrin deposits, and occasional crescents. Iron stains revealed prominent mesangial iron deposition. In immunized animals, IgG and C3 deposits were localized mainly in the mesanglium. Electron microscopic studies revealed marked deposition of ferratin complexesexpanded mesangial matrix and mesangial interposition. Ferratin immune complexes were also visualized in epithelial spaces. In the latter location ferritin immune complexes occasionally formed characteristic electron-dense subepithelial deposits. In this model, mesangial and subepithelial localization of autologous ferritin immune complexes is associated with development of glomerulonephritis and characteristic mesangial lesions resembling those seen in some types of human glomerulonephritis.     

骨髓间充质干细胞修复系膜增生性肾炎：作用及机制

BACKGROUND: Bone marrow mesenchymal stem cells are likely to repair renal injury by differentiating into renal parenchymal cells. OBJECTIVE: To explore the effect and mechanism of bone marrow mesenchymal stem cells in the renal repair after mesangial proliferative glomerulonephritis. METHODS: Thirty Sprague-Dawley rats were randomized into normal group, model group and treatment group (n=10 per group). Model group and treatment group were treated with tail vein injection of mouse anti-rat monoclonal antibody Thy1.1 to prepare mesangial proliferative glomerulonephritis models. One week after modeling, rats in the treatment group were given 2×106 bone marrow mesenchymal stem cells via the tail vein, and rats in the other two groups were given the same volume of normal saline. Two weeks after transplantation, urinary protein, urea nitrogen, creatinine levels were detected; hematoxylin-eosin staining was used for observing pathological changes of the renal tissue under microscope; and the expression of transforming growth factor beta 1 was detected by immunohistochemistry method. RESULTS AND CONCLUSION: The levels of urinary protein, urea nitrogen and creatinine as well as the expression of transforming growth factor beta 1 in the renal tissue arranged in descending order were listed as follows: model group > treatment group > control group, and there were significant differences among three groups (P < 0.05). In the model group, diffuse glomerular hyperplasia was observed with the presence of increased extracellular matrix, partial glomerular sclerosis, and interstitial infiltration of inflammatory cells; in the treatment group, glomerular hyperplasia, mesangial proliferation and inflammatory cell infiltration were all mitigated compared with the model group. Therefore, bone marrow mesenchymal stem cell transplantation may contribute to renal repair after mesangial proliferative glomerulonephritis, by inhibiting overexpression of transforming growth factor beta 1 in the kidney. 中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程      

Glomerular deposition of immune complexes prepared with monomeric or polymeric IgA.

Clearance kinetics and renal deposition of soluble IgA immune complexes (IgA IC) were examined to determine the nephritogenic potential of IgA molecular form in mediating experimental IgA nephropathy. The immune complexes were prepared by mixing purified radiolabelled monomeric (mIgA) or polymeric (pIgA) IgA anti-dinitrophenyl (DNP), derived from MOPC-315 myeloma, with DNP conjugated Ficoll (DNP8-Ficoll). Clearance of IgAIC from the circulation was curve fitted by two exponential components. The first component was similar for both mIgA IC and pIgA IC. The second component was slightly more rapid for mIgA IC than for pIgA IC. Immunofluorescence studies, however, showed that only pIgA IC deposited in the kidneys. Analysis of IgA IC by gradient polyacrylamide gel electrophoresis indicated that mIgA formed only small latticed complexes. The critical role of IgA IC lattice size in renal deposition was confirmed by demonstrating that large latticed mIgA IC, prepared by covalent cross-linking mIgA with a specific affinity labelling antigen, deposited in the kidneys in a pattern similar to pIgA IC. Our results suggest that the monovalency of mIgA is responsible for its inability to form a large latticed nephritogenic complexes.     

Altered long non-coding RNA expression profile in patients with IgA-negative mesangial proliferative glomerulonephritis

Mesangial proliferative glomerulonephritis (MsPGN) is one of the most common immune-mediated renal diseases. The mesangium is expanded and hypercellular, immuno-globulin deposits can be found in the mesangium, but the mechanism underlying its cause remains largely unclear. There is a large amount of evidence suggesting that long ﹥200 nucleotide) non-coding RNAs (lncRNA) have important regulatory functions in the epigenetic control of gene expression. Multiple lines of evidence increasingly link mutations and dysregulations of lncRNAs to a diverse number of human diseases. Through microarray expression analysis, tests show that thousands of lncRNAs and protein-coding genes are significantly differentially expressed in IgA-negative MsPGN. Some lncRNAs and their neighboring protein-coding genes are closely related and are cooperatively expressed. This may be part of a potential regulatory mechanism. The malfunction of regulation in the network of lncRNAs may be a possible mechanism for the development of IgA-negative MsPGN. Our observations suggest that some lncRNAs are closely related to IgA-negative MsPGN and may be playing an important role in this disease.     

IgA glomerulonephritis (Berger's disease): evidence of high serum levels of polymeric IgA.

Eleven out of 15 patients with IgA mesangial glomerulonephritis (Berger's disease) had an increased proportion of serum IgA in 9-21S fractions on 5-40% sucrose density-gradient ultracentrifugation; the heavier fractions decreased at acid pH. Serum IgA purified by starch electrophoresis was subjected to reduction-alkylation yielding fragments of lower molecular weight. J chain was detected on urea alkaline polyacrylamide electrophoresis and the high-molecular weight IgA bound the human secretory component. In six patients treated with phenytoin for 1 year there was a decrease in polymeric IgA and an increase in monomeric IgA adopting a pattern similar to that of the controls. Our results show the presence of a large amount of true IgA polymers, partially as immune complexes, in the serum of patients with Berger's disease. These data together with their normalization after phenytoin treatment may open a new pathogenic and therapeutic approach to this entity.     

Effect of cyclosporin on immune complex deposition in murine glomerulonephritis.

Chronic glomerulonephritis (GN) was induced in N/M mice by daily injections of human serum albumin (HSA). The glomerular lesion was similar to that observed in human membranous GN and was characterized by intense mesangial and capillary loop immunofluorescent staining for HSA, IgG and C3. Electron microscopic examination revealed numerous electron-dense deposits in the mesangium and along the subepithelial side of the glomerular basement membrane, the latter deposits being associated with membranous spikes. Chronically injected mice that had been treated with cyclosporin (CsA) from Day 1 had different patterns of immune complex deposition. Mesangial deposition was apparently unaltered but no subepithelial deposits or spikes were evident. In addition, only two out of 21 HSA-injected mice which began CsA treatment on Day 21 had subepithelial deposits. There was no significant difference in serum levels of HSA-specific IgG between the three groups of mice. CsA treatment would therefore appear to ameliorate the immunopathology of antigen-induced glomerulonephritis in this model without affecting serum antibody levels, and may be of therapeutic value in the treatment of human membranous GN.     

Mesangial proliferative glomerulonephritis associated with progressive amyloid deposition in hamsters experimentally infected with Leishmania donovani.

In the present work, 42 golden hamsters (Mesocricetus auratus) were infected by intracardiac injection of 5 X 10(6) amastigote forms of Leishmania donovani. Another group of 28 animals served as uninfected controls. Six hamsters of the infected group and four hamsters of the control group were selected randomly and sacrificed at Days 7, 14, 21, 28, 35, 42, and 49 after inoculation. The kidneys were studied by light microscopy, immunofluorescence and electron microscopy. The levels of serum and urinary immunoglobulins were determined. None of the control hamsters had kidney lesions. Light-microscopically the kidneys of infected hamsters showed a marked mesangial proliferation from Day 7 after infection. These changes were more pronounced at Day 21, when a discrete infiltration of mononuclear cells was frequent. These glomerular changes diminished after Day 28 and were replaced by deposits of amyloid. In the beginning these deposits were in the mesangium and progressively became more extensive, involving capillary loops, Bowman's capsule, and interstitium. The immunofluorescence study showed L donovani antigens and hamster immunoglobulins, primarily in the mesangial areas, by Days 7-14 after infection. These deposits extended into contiguous loops from Day 21 to Day 28. In the last 2 weeks the fluorescent staining for L donovani antigens remained intensely positive, whereas the staining for hamster immunoglobulins became moderate to slightly positive. The ultrastructural study revealed mesangial proliferation, mesangial and paramesangial electron-dense deposits, and amyloidosis in the glomeruli of infected animals. The serum immunoglobulins increased from Day 7 after infection, reaching a peak at Day 21 and falling thereafter until Day 49 to near control values. Immunoglobulins were detected in the urine of infected hamsters at day 21, increasing in amount thereafter. Since L donovani antigens and immunoglobulins were identified in the glomerular lesions, it is likely that they are implicated in the pathogenesis of the mesangial proliferative glomerulonephritis in hamsters experimentally infected with L donovani. The glomerular changes may also explain the loss of immunoglobulins in the urine and the consequent lowering of serum immunoglobulin levels.     

Sequential expression of cellular fibronectin by platelets, macrophages, and mesangial cells in proliferative glomerulonephritis.

Fibronectin (Fn) regulates cell migration, proliferation, and extracellular matrix formation during embryogenesis, angiogenesis, and wound healing. Fn also promotes mesangial cell migration and proliferation in vitro and contributes to extracellular matrix formation and tissue remodeling during glomerular disease. In this study, we examined, by immunohistochemistry and in situ hybridization, the temporal glomerular localization and cellular sources of Fn in Habu snake venom (HSV)-induced proliferative glomerulonephritis. Early HSV-induced glomerular lesions consisted of microaneurysms devoid of resident glomerular cells and filled with platelets, leukocytes, and erythrocytes. Over the course of the disease, mesangial cells migrated into the lesions, proliferated, and formed a confluent cellular mass. Fn was present in lesions beginning at 8 hours, with highest intensity at 72 hours and diminishing at 2 weeks after HSV. Staining for Fn at 8 and 24 hours after HSV was attributed to platelets and macrophages. In situ hybridization and phenotypic identification of cell types within lesions revealed macrophages as the predominant source of cellular Fn mRNA at these times. At 48 hours after HSV, Fn mRNA was expressed in proliferating mesangial cells in addition to macrophages. Most cells in lesions at 72 hours after HSV were mesangial, at a time when expression of Fn mRNA peaked. Cellular expression for Fn mRNA and translated protein declined at 2 weeks after HSV. These studies support the hypothesis that Fn, derived from platelets and macrophages, provides a provisional matrix involved with mesangial cell migration into glomerular lesions. Fn produced by mesangial cells might contribute to the formation of a stable extracellular matrix.     

Focal mesangial proliferative glomerulonephritis in the rat caused by habu snake venom. A morphologic study.

A new model of focal mesangial proliferative glomerulonephritis in the rat has been produced by intravenous habu snake venom. Glomerulonephritis developed in 70% of rats surviving the first 6 hours after venom administration. The earliest ultrastructural change (10 minutes after venom) was the presence of loose platelet aggregates and free granules in the capillary lumen and mesangium. This was followed by dissolution of the matrix and endothelial damage. Between 4 and 24 hours, a characteristic focal and segmental ballooned lesion of glomerular capillaries developed. In these lesions, from 3 days onwards a segmental mesangial proliferation occurred, which persisted until sacrifice at 21 days.