Expression of a novel PDGF isoform, PDGF-C, in normal and diseased rat kidney

Platelet-derived growth factor-C (PDGF-C) is a new member of the PDGF family. Its expression in normal and diseased kidney is unknown. Rabbit antisera were generated against human full-length, core domain, and mouse PDGF-C, and their specificity was confirmed by Western blot analyses. Renal PDGF-C expression was analyzed by immunohistochemistry in normal rats (n = 8), mesangioproliferative anti-Thy 1.1 nephritis (n = 4 each at days 1, 4, 6, and 85), passive Heymann nephritis (PHN, n = 4), puromycin nephrosis (PAN, n = 2), Milan normotensive rats (MN, n = 2), and obese Zucker rats (n = 3). PDGF-C expression was also studied in anti-Thy 1.1 rats treated with PDGF-B aptamer antagonists (n = 5) or irrelevant control aptamers (n = 5). PDGF-C was constitutively expressed in arterial smooth muscle cells and collecting duct epithelial cells. Mesangial PDGF-C was markedly upregulated in anti-Thy 1.1 nephritis in parallel with the peak mesangial cell proliferation. Furthermore, PDGF-CC acted as a potent growth factor for mesangial cells in vitro. Inhibition of PDGF-B via specific aptamers reduced the injury in anti-Thy 1.1 nephritis but did not affect the glomerular PDGF-C overexpression or the mitogenicity of PDGF-CC in vitro. In PHN, PAN, and obese Zucker rats, glomeruli remained negative for PDGF-C despite severe glomerular injury. PDGF-C localized to podocytes at sites of focal and segmental sclerosis in MN. Interstitial PDGF-C expression was increased at sites of fibrosing injury in obese Zucker rats. The use of the different antisera resulted in virtually identical findings. It is concluded that PDGF-C is a novel mesangial cell mitogen that is constitutively expressed in the kidney and specifically upregulated in mesangial, visceral epithelial, and interstitial cells after predominant injury to these cells. PDGF-C may therefore be involved in the pathogenesis of renal scarring.     

Intraglomerular synthesis of complement C3 and its activation products in IgA nephropathy

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.     

Angiogenic protein Cyr61 is expressed by podocytes in anti-Thy-1 glomerulonephritis

Dynamic recovery of glomerular structure occurs after severe glomerular damage in anti-Thy-1 glomerulonephritis (Thy-1 GN), but its mechanism remains to be investigated. To identify candidate genes possibly involved in glomerular reconstruction, screening was performed for genes that are specifically expressed by podocytes and are upregulated in glomeruli of Thy-1 GN. Among them, cysteine-rich protein 61 (Cyr61 or CCN1), a soluble angiogenic protein belonging to the CCN family, was identified. By Northern blot analysis, Cyr61 mRNA was markedly upregulated in glomeruli of Thy-1 GN from day 3 through day 7, when mesangial cell migration was most prominent. By in situ hybridization and immunohistochemistry, Cyr61 mRNA and protein were expressed by proximal straight tubules and afferent and efferent arterioles in normal rat kidneys and were intensely upregulated at podocytes in Thy-1 GN. Platelet-derived growth factor-BB (PDGF-BB) and transforming growth factor-beta1 (TGF-beta1), of which the gene expression in the glomeruli of Thy-1 GN was upregulated in similar time course as Cyr61, induced Cyr61 mRNA expression in cultured podocytes. Furthermore, supernatant of Cyr61-overexpressing cells inhibited PDGF-induced mesangial cell migration. In conclusion, it is shown that Cyr61 is strongly upregulated at podocytes in Thy-1 GN possibly by PDGF and TGF-beta. Cyr61 may be involved in glomerular remodeling as a factor secreted from podocytes to inhibit mesangial cell migration.     

Expression of Ras GTPases in normal kidney and in glomerulonephritis.

BACKGROUND: Small monomeric Ras GTPases play critical and specific roles in the control of cellular proliferation and apoptosis but the expression of the three Ras isoforms (Ha-Ras, Ki-Ras and N-Ras) in human renal tissue is unknown. This work is an immunohistochemical study of Ras expression in normal renal tissue and in membranous glomerulonephritis (MGN), IgA nephropathy (IgAN) and IgA-negative mesangioproliferative glomerulonephritis (MPGN). METHODS: Formalin-fixed, paraffin-embedded tissue was stained using pan-Ras monoclonal antibody (mAb) and Ras isoform-specific mAb. Detection employed a (DAKO Envision) modified polymer system. RESULTS: The expression of Ras isoforms in normal human kidney was cell-specific. For example, N-Ras was detected in tubule epithelial cells but not in glomerular or interstitial cells. Ki-Ras was expressed in mesangial cells, interstitial cells and in proximal convoluted tubule cells (PCT) (particularly localized at brush borders) and in collecting duct cells (CD) (localized to cell membranes) but not in podocytes. Cytoplasmic Ha-Ras was detected in all the above cell types except podocytes. MGN was associated with podocyte expression of all three Ras isoforms and with reduced mesangial cell expression of Ha-Ras and Ki-Ras. IgAN was characterized by podocyte expression of Ha-Ras (but not Ki-Ras) and reduced mesangial cell expression of Ki-Ras without alterations in mesangial Ha-Ras expression. MPGN was associated with reduced mesangial cell Ha-Ras and Ki-Ras expression without significant podocyte Ras expression. CONCLUSION: These disease-specific and isoform-specific alterations in Ras expression may be of significance in pathogenesis and warrant further functional investigation.     

Localization of APOL1 Protein and mRNA in the Human Kidney: Nondiseased Tissue,Primary Cells,and Immortalized Cell Lines

Although APOL1 gene variants are associated with nephropathy in African Americans, little is known about APOL1 protein synthesis, uptake, and localization in kidney cells. To address these questions, we examined APOL1 protein and mRNA localization in human kidney and human kidney-derived cell lines. Indirect immunofluorescence microscopy performed on nondiseased nephrectomy cryosections from persons with normal kidney function revealed that APOL1 protein was markedly enriched in podocytes (colocalized with synaptopodin and Wilms’ tumor suppressor) and present in lower abundance in renal tubule cells. Fluorescence in situ hybridization detected APOL1 mRNA in glomeruli (podocytes and endothelial cells) and tubules, consistent with endogenous synthesis in these cell types. When these analyses were extended to renal-derived cell lines, quantitative RT-PCR did not detect APOL1 mRNA in human mesangial cells; however, abundant levels of APOL1 mRNA were observed in proximal tubule cells and glomerular endothelial cells, with lower expression in podocytes. Western blot analysis revealed corresponding levels of APOL1 protein in these cell lines. To explain the apparent discrepancy between the marked abundance of APOL1 protein in kidney podocytes observed in cryosections versus the lesser abundance in podocyte cell lines, we explored APOL1 cellular uptake. APOL1 protein was taken up readily by human podocytes in vitro but was not taken up efficiently by mesangial cells, glomerular endothelial cells, or proximal tubule cells. We hypothesize that the higher levels of APOL1 protein in human cryosectioned podocytes may reflect both endogenous protein synthesis and APOL1 uptake from the circulation or glomerular filtrate.     

In situ hybridization of connective tissue growth factor mRNA in IgA nephropathy

Connective tissue growth factor (CTGF) is a member of the new family of growth regulators. It plays an important role of the pathogenesis of mesangial matrix accumulation and progressive glomerulosclerosis in IgA nephropathy (IgAN).
We investigated the expression and localization of CTGF mRNA in renal tissues of patients with IgAN and normal human kidneys (NHK), using in situ hybridization with digoxigenin-labelled oligonucleotide. Open renal biopsy tissues were obtained from 16 patients with IgAN. The renal pathology was categorized into four grades by light microscopic findings. The expression level of CTGF mRNA was quantified by counting all nuclei, as well as nuclei surrounded by CTGF mRNA-positive cytoplasm in randomly selected non-sclerotic glomeruli and expressing the results as the percentage of total cells.
Connective tissue growth factor mRNA was mainly expressed in glomerular mesangial and epithelial cells in both IgAN and NHK, and cells of Bowman's capsule. In IgAN, CTGF mRNA-positive cells were increased in tubulointerstitial fibrotic areas. The percentage of positive cells for CTGF mRNA was significantly higher in IgAN than in NHK. The percentage of positive cells for CTGF mRNA in each IgAN grade was significantly higher than that in NHK. Furthermore, the percentage of positive cells for CTGF mRNA was significantly greater in IgAN with moderate mesangial proliferative lesions (grade 2, grade 3) than in IgAN with mild mesangial proliferative lesions.
Our study suggests that CTGF may play an important role in the development and progression of glomerulosclerosis and tubulointerstitial fibrosis in IgAN.     

Functional endothelin 1 receptors on human glomerular podocytes and mesangial cells.

To determine if endothelin 1 (Et1) receptors are present in human glomeruli, and which glomerular cells possess these receptors, 125I Et1 binding to isolated glomeruli and cultured glomerular mesangial and epithelial cells was studied. The latter were identified as podocytes. We demonstrated that Et1 binds specifically and reversibly to isolated human glomeruli and to cultured glomerular mesangial and epithelial cells. Scatchard analysis of competitive inhibition of 125I Et1 binding gave the following results (m +/- SEM, n = 3): isolated glomeruli, Kd = 4.2 +/- 2.1 x 10(-10) M, Bmax = 8.1 +/- 1.2 x 10(10) sites/mg protein; mesangial cells, Kd = 5.2 +/- 1.5 x 10(-10) M, Bmax = 1.87 +/- 0.49 x 10(4) sites/cell; epithelial cells, Kd = 7.2 +/- 1.5 x 10(-10) M, Bmax = 2.46 +/- 0.15 x 10(4) sites/cell. These receptors seem to be functional, since in both mesangial and epithelial cells Et1 induces a rapid and transient increase in intracellular [Ca2+]i. All these results indicate that Et1 may regulate glomerular filtration rate through an autocrine-paracrine pathway on mesangial cells and on podocytes.     

儿童原发性肾病综合征中血管生成素样蛋白3的表达

目的 研究血管生成素样蛋白3 (angiopoietin-like 3 protein，ANGPTL3)在儿童原发性肾病综合征(PNS)患者肾组织中表达分布及其参与蛋白尿发生的机制。方法 ANGPTL3分别与足细胞核标记抗原(WT1)、基底膜标记抗原类肝素硫酸蛋白多糖perlecan进行双标记法免疫荧光染色。应用免疫组化的方法检测ANGPTL3和perlecan在不同病理类型的69例PNS及血尿患儿，包括微小病变(MCD)31例、膜性肾病(MN)6例、局灶节段硬化性肾小球肾炎(FSGS)6例、IgA肾病16例、薄基底膜肾病(TBMN)10例以及2例正常对照肾组织中表达，并以IMS彩色图像分析系统量化为免疫组化指数。在MCD病例中将尿蛋白肌酐比值分别与肾组织中ANGPTL3和perlecan肾小球内染色强度及电镜下平均足突宽度(FWP)进行相关分析。对不同病理诊断时间(发病至肾穿刺)分组患儿肾小球ANGPTL3和perlecan的表达进行比较。结果 (1)ANGPTL3在正常肾组织呈现微弱的沉积，而在不同病理类型的肾病综合征患儿的肾组织的肾小球和肾小管存在不同程度的表达。肾小球内ANGPTL3表达量在MCD(7.49±1.96)、MN(6.27±0.98)中显著高于正常对照(0.02±0.001)、TBMN(0.02±0.001)及FSGS(3.14±0.49)(均P < 0.05)。在IgA肾病(系膜增生型)中，蛋白尿组肾小球中ANGPTL3表达量显著高于单纯血尿组(1.90±0.81比0.03±0.01， P < 0.05)。(2) 在MCD肾组织中，WT1及perlecan荧光双标记染色显示， ANGPTL3在足细胞胞浆及沿肾小球血管袢表达。(3) ANGPTL3在肾小球表达量分别与尿蛋白肌酐比值及电镜下平均足突宽度正相关(r为0.86、0.84，P均<0.05)，并与perlecan在肾小球内表达量负相关(r为-0.83，P < 0.05)。(4)不同发病年限的MCD患儿肾组织中肾小球ANGPTL3及perlecan的表达无显著性差异。结论 在不同程度的蛋白尿及不同足突融合程度的肾组织中存在ANGPTL3的表达差异。在MCD中，ANGPTL3主要在足细胞胞浆表达，肾小球中ANGPTL3的表达与蛋白尿程度及足细胞融合程度呈正相关。     

Protein localization and mRNA expression of epimorphin in mouse and human kidneys.

Epimorphin is a mesenchymal cell surface protein which induces epithelial branching morphogenesis. However, the role of epimorphin in the kidney has not been addressed. In the present study, the localization of epimorphin protein and the expression of its mRNA were investigated in the developing mouse and adult human kidneys using immunohistochemistry and semiquantitative RT-PCR. The in vitro expression of epimorphin protein and its mRNA was also explored in cultured mouse and human mesangial cells. Epimorphin protein was expressed in the renal interstitium and the circumference of the comma-shaped body at day 16 of gestation. The intensity and distribution of epimorphin were gradually increased during kidney differentiation and maturation. Epimorphin was first observed in glomeruli at 1 week of age. The localization of epimorphin in glomerular mesangial cells and interstitial fibroblasts was confirmed by immunoelectron microscopy of 2-week-old mouse kidneys. The highest mRNA expression of epimorphin was observed at day 16 of gestation, thereafter it diminished with the maturation of the kidney. A similar localization of epimorphin was observed in a normal adult human kidney. Cultured human mesangial cells expressed epimorphin mRNA 150-kD protein. These results suggest that epimorphin may play a role in the development of the kidney and in the differentiation of fibroblast and mesangial cells.     

CCN3 is a novel endogenous PDGF-regulated inhibitor of glomerular cell proliferation

CCN proteins affect cell proliferation, migration, attachment, and differentiation. We identified CCN3 as a suppressed gene following platelet-derived growth factor (PDGF)-BB or -DD stimulation in a cDNA-array analysis of mesangial cells. In vitro growth-arrested mesangial cells overexpressed and secreted CCN3, whereas the addition of the recombinant protein inhibited cell growth. Induction of mesangial cell proliferation by PDGF-BB or the specific PDGF beta-receptor ligand PDGF-DD led to downregulation of CCN3 mRNA, confirming the array study. Specific PDGF alpha-receptor ligands had no effect. CCN3 protein was found in arterial smooth muscle cells, the medullary interstitium, and occasional podocytes in the healthy rat kidney. Glomerular CCN3 was low prior to mesangial proliferation but increased as glomerular cell proliferation subsided during mesangioproliferative glomerulonephritis (GN). Inhibition of PDGF-B in mesangioproliferative disease led to overexpression of glomerular CCN3 mRNA. CCN3 localized mostly to podocytes in human glomeruli, but this expression varied widely in different human glomerulonephritides. Glomerular cell proliferation negatively correlated with CCN3 expression in necrotizing GN. Our study identifies CCN3 as an endogenous inhibitor of mesangial cell growth and a modulator of PDGF-induced mitogenesis.     

Glomerular angiotensinogen protein is enhanced in pediatric IgA nephropathy

Enhanced intrarenal renin-angiotensin system (RAS) is implicated in the development and progression of renal injury. To investigate whether angiotensinogen (AGT) expression is involved in glomerular RAS activity and glomerular injury, we examined glomerular AGT expression and its correlation with expression of other RAS components, and levels of glomerular injury in samples from patients with immunoglobulin A nephropathy (IgAN) (23) and minor glomerular abnormalities (MGA) (8). Immunohistochemistry showed that AGT protein was highly expressed by glomerular endothelial cells (GEC) and mesangial cells in nephritic glomeruli of IgAN compared with glomeruli of MGA. Levels of glomerular AGT protein were well correlated with levels of glomerular angiotensin II (ang II), transforming growth factor-beta (TGF-beta), alpha-smooth-muscle actin, glomerular cell number, and glomerulosclerosis score but not with those of glomerular angiotensin-converting enzyme and ang II type 1 receptor. Real-time polymerase chain reaction (RT-PCR) and Western blot analyses using cultured human GEC indicated that ang II upregulated AGT messenger ribonucleic acid (mRNA) and protein expression in a dose- and time-dependent manner. These data suggest that activated glomerular AGT expression is likely involved in elevated local ang II production and, thereby, may contribute to increased TGF-beta production and development of glomerular injury in IgAN. Augmentation of GEC-AGT production with ang II stimulation might drive further glomerular injury in a positive-feedback loop.     

Intrarenal synthesis of IL-6 in IgA nephropathy

Summary: Recent in vitro studies have shown the synthesis of interleukin-6 (IL-6) in glomerular mesangial and epithelial cells, and suggested the involvement of IL-6 in mesangial proliferative glomerulonephritis. However, the expression site of IL-6 mRNA in renal tissue of IgA nephropathy (IgAN), the most common chronic mesangial proliferative glomerulonephritis, remains obscure. to localize IL-6 mRNA in renal biopsy specimens of IgAN, we used nonradioactive in situ hybridization (ISH) developed in our laboratory, sensitive in detecting individual cells positive for a specific mRNA. In some sections, periodic acid-Schiff staining was performed after ISH in order to identify the topographical relation between IL-6 mRNA positive cells and glomerular basement membrane and mesangial area. In situ hybridization for IL-6 mRNA and immunohistochemistry for CD3 and CD68, markers for lymphocytes and monocytes, respectively, were also performed on serial sections to examine the contribution of infiltrated mononuclear cells to cells positive for IL-6 mRNA in glomeruli. Glomerular resident cells, including glomerular mesangial and epithelial cells and cells of Bowman's capsule, as well as tubular epithelial cells and infiltrated mononuclear cells expressed IL-6 mRNA. We also compared the localization of IL-6 mRNA and protein and showed different distribution between the gene product and protein. the expression of IL-6 mRNA correlated with the degree of mesangial cell proliferation and tubulointerstitial changes. Our results indicate that IL-6 is synthesized in renal tissues of IgAN and suggest that the increased IL-6 expression may be important in the pathogenesis of IgAN.     

Tissue-specific expression of renin-angiotensin system components in IgA nephropathy

BACKGROUND: The renin-angiotensin II system (RAS) has been implicated in the development of glomerulonephritis. The aims of this study were to determine (1) the expression of RAS components, angiotensin (Ang II)-forming enzymes [angiotensin-I-converting enzyme (ACE) and chymase], and Ang II receptors, and (2) the correlation between RAS expression and severity of tissue injury in IgA nephropathy (IgAN). METHODS: The expression levels of ACE, chymase, and Ang II type 1 and type 2 receptor (AT1R and AT2R) mRNAs were determined by in situ hybridization in renal specimens from 18 patients with IgAN, 5 patients with non-IgA mesangial proliferative glomerulonephritis (non-IgAN) and 10 patients with nonmesangial proliferative glomerulonephritis (minimal change nephrotic syndrome, n = 5, and membranous nephropathy, n = 5). Normal portions of surgically resected kidney served as control. RESULTS: In normal kidney, a few mesangial cells and glomerular and tubular epithelial cells weakly expressed ACE, chymase and AT1R mRNAs. In IgAN and non-IgAN samples, ACE, chymase, AT1R and AT2R mRNAs were expressed in resident glomerular cells, including mesangial cells, glomerular epithelial cells and cells of Bowman's capsule. The glomerular expressions in IgAN were stronger than in minimal change nephrotic syndrome and membranous nephropathy. In IgAN, the expressions in glomeruli correlated with the degree of mesangial hypercellularity, whereas the expression levels were weaker at the area of mesangial expansion. IgAN with severe tubulointerstitial injury showed expression of ACE, chymase, AT1R and AT2R mRNAs in atrophic tubules and infiltrating cells and such expression correlated with the degree of tubulointerstitial damage. CONCLUSION: Our results suggest that renal cells can produce RAS components and that locally synthesized Ang II may be involved in tissue injury in IgAN through Ang II receptors in the kidney.     

Mesangial IgA1 in IgA nephropathy exhibits aberrant O-glycosylation: observations in three patients

BACKGROUND: In IgA nephropathy (IgAN), circulating IgA1 molecules display an abnormal pattern of O-glycosylation. This abnormality may potentially contribute to mesangial IgA1 deposition, but this is unproven because the O-glycosylation of mesangial IgA1 has not been analyzed. METHODS: IgA1 was eluted from glomeruli isolated from the kidneys of three IgAN patients obtained after nephrectomy or at postmortem. Serum from these patients, other patients with IgAN, and controls was subjected to the same treatment as the glomerular eluates. The O-glycosylation of eluted and serum IgA1 was measured by lectin binding using an enzyme-linked immunosorbent assay-based system. RESULTS: In all three cases, the lectin binding of IgA1 eluted from the glomeruli of IgAN patients was markedly higher than that of the serum IgA1 of the same individual, and also all but one of a series of serum IgA1 samples from other patients and controls. CONCLUSIONS: The higher lectin binding of glomerular compared with serum IgA1 suggests that O-glycosylated IgA1 molecules abnormally and selectively deposit in the kidney. These results provide the first evidence that mesangial IgA1 is abnormally O-glycosylated, and support a direct role for abnormal IgA1 O-glycosylation in the mechanism of mesangial IgA deposition in IgAN.     

Leprecan distribution in the developing and adult kidney

The temporal and spatial deposition of extracellular matrix proteins is critical for nephrogenesis and glomerular maturation. We previously characterized leprecan as a novel chondroitin sulfate proteoglycan which has been recently shown to have prolyl hydroxylase activity. In this study, we examine the distribution of leprecan during nephrogenesis and after a hypertrophic stimulus to the adult kidney. During development, leprecan was localized to mesenchymal aggregates, early comma- and S-phase structures as determined by immunohistochemistry and in situ hybridization. Leprecan mRNA was increased in cells around the vascular cleft of the S- and comma-phase glomeruli. Expression was found in podocytes, mesangial cells, and parietal epithelial cells of loop-phase glomeruli. Leprecan mRNA was substantially decreased in the glomeruli of the adult kidney compared to the developing kidney with a uniform distribution between the glomeruli and the tubules. Within adult glomeruli, leprecan was found in the mesangium mesangial matrix, podocytes, and in Bowman's capsule. In response to glomerular hypertrophy, produced by unilateral nephrectomy, leprecan synthesis was increased in the adult kidney. We suggest that the regulated expression of leprecan during glomerular development or hypertrophy coupled with its reported prolyl hydroxylase activity plays a role during basement membrane assembly.     

Glomerular distribution and gelatinolytic activity of matrix metalloproteinases in human glomerulonephritis.

BACKGROUND: Matrix metalloproteinases (MMPs) have been implicated in the development of glomerular injury in rat experimental glomerulonephritis (GN). However, the significance of MMPs in human GN remains obscure. In order to evaluate the role of MMPs in human GN, we examined the glomerular distribution and gelatinolytic activities of MMP-2 and MMP-9 in human GN. METHODS: We performed immunohistochemistry with polyclonal anti-MMP-2 and MMP-9 antibodies, and analysed gelatin zymograms of five isolated glomeruli from various types of human renal disease. The renal specimens investigated were from normal kidneys (n=5), IgA nephritis (n=20), Henoch-Sch?nlein nephritis (n=4), non-IgA mesangial proliferative GN (n=9), lupus nephritis (n=6), acute poststreptococcal GN (APSGN) (n=4) and diabetic nephropathy (DN) (n=4). RESULTS: MMP-2 immunoreactivity was not detected in normal controls or in any type of GN. MMP-9 staining, which was almost negative in normal glomeruli, was increased mainly in the mesangial region and corresponded to the level of glomerular cell proliferative changes in mesangial proliferative GN (IgA nephritis, Henoch-Sch?nlein nephritis, non-IgA mesangial proliferative GN and lupus nephritis). Positive but weak staining for MMP-9 was observed in mesangial areas in DN. In addition, double immunostaining showed that MMP-9 is colocalized in scattered neutrophils within diseased glomeruli in APSGN. MMP-9 gelatinolytic activity in five normal glomeruli was weakly detected. Consistent with the levels of immunostaining, MMP-9 glomerular activity was dramatically increased in nephritic glomeruli with IgA nephritis, lupus nephritis and DN. The gelatinolytic activity of MMP-2 was occasionally detectable in nephritic glomeruli. CONCLUSION: These results strongly suggest that MMP-9 plays an important role in abnormal mesangial proliferative changes in human GN.     

Differential effects of FMLP-activated neutrophils from patients with IgA nephropathy enhanced endothelin 1 production of glomerular mesangial cells

BACKGROUND: Neutrophil infiltration in the glomeruli is common in patients with IgA nephropathy (IgAN). The pathogenetic roles of the infiltrated neutrophils and their relationship with glomerular mesangial cells, however, are not clear. METHODS: We examined the effects of coculture with N-formyl-methionyl-leucyl-phenylalanine (FMLP) activated neutrophils on the viability, endothelin 1 (ET-1) production, and ET-1 mRNA expression of rat glomerular mesangial cells. Neutrophils were isolated from 15 IgAN patients, from 13 patients with non-IgA mesangial proliferative glomerulonephritis (MsPGN), and from 10 normal controls. RESULTS: The ET-1 production by mesangial cells was significantly higher after stimulation with FMLP-activated neutrophils from IgAN patients than that of MsPGN patients and normal controls, and this effect was significantly abolished by pretreating mesangial cells with superoxide dismutase and partly abolished by catalase. The ET-I mRNA expression of mesangial cells showed a parallel increase with ET-1 protein. The trypan blue exclusion test showed significant mesangial cell death after stimulation with FMLP-activated neutrophils as compared with quiescent neutrophils, and the cell death was also prevented by superoxide dismutase but not catalase. The FMLP-activated neutrophils from IgAN patients produced more superoxide than those of MsPGN patients and normal controls. CONCLUSION: The FMLP-activated neutrophils from patients with IgAN have differential effects in enhancing the cell death and the ET-1 production of glomerular mesangial cells through the release of superoxide.     

Anti-macrophage migration inhibitory factor reduces transforming growth factor-beta 1 expression in experimental IgA nephropathy.

BACKGROUND: In human glomerulonephritis, including immunoglobulin-A nephropathy (IgAN), glomerular expression of macrophage migration inhibitory factor (MIF) is found to correlate with progressive renal injury. We have shown previously that polymeric IgA is capable of inducing MIF production in cultured human mesangial cells, suggesting a role in inducing inflammatory injury in IgAN. Herein, we examined whether IgA deposition and the subsequent renal injury can be ameliorated with anti-MIF treatment in an experimental murine model of IgAN. METHODS: Glomerular IgA deposition was induced in 4-week-old BALB/c mice by intravenous injection of immune complexes consisting of dinitrophenyl-conjugated bovine serum albumin (DNP-BSA) and IgA MOPC-315 myeloma anti-DNP antibodies. To determine the therapeutic effect of anti-MIF, mice were given anti-MIF (5 mg/kg) or isotypic control antibody intravenously 2 h before the immune complexes administration. The mice were sacrificed 48 h after injection of DNP-IgA. Proteinuria and haematuria were determined and the kidneys were removed for histopathology, immunostaining and immunoblotting. The effect of exogenous MIF on production of TGF-beta 1 by cultured mesangial cells was also examined. RESULTS: IgA deposits were detected in glomeruli of all mice receiving the immune complexes while no glomerular deposit was detected in the control mice. Microscopic haematuria and mesangial hypercellularity were present in mice of the three experimental groups and were absent in the control group. Proteinuria was absent in all groups. Anti-MIF treatment also resulted in decreased renal expression of TGF-beta 1. Moreover, the reduction in TGF-beta 1 expression was confined mainly to glomerular mesangium. An in vitro culture experiment demonstrated that MIF increased TGF-beta 1 production in a time- and dose-dependent fashion. MIF-induced TGF-beta 1 synthesis was abolished by incubating cells with neutralizing antibody against MIF. CONCLUSIONS: Our finding shows that anti-MIF treatment can ameliorate kidney injury and reduce glomerular TGF-beta 1 expression in an experimental model of IgAN.     

三种实验性IgA肾病模型的比较

目的探讨建立一种理想的IgA肾病（IgAN）动物模型方法。方法分别采用葡聚糖G200、大肠杆菌外膜蛋白和金葡菌的细胞膜20肽抗原决定簇诱导小鼠IgA肾病模型。用分子生物学和病理学方法对3组IgAN模型小鼠进行鉴定和比较。结果（1）葡聚糖组尿蛋白增高，伴有血尿；免疫荧光显示部分肾小球大量IgA沉积；光镜下肾小球系膜细胞增多，肝和脾可见弥漫性的粉染物质沉积；电镜下肾小球系膜区少量低电子密度的致密沉积物，肝和脾可见淀粉丝样物质沉积。（2）大肠杆菌外膜蛋白组尿蛋白增高，伴有血尿；免疫荧光显示肾小球有少量IgA沉积；光镜下肾小球系膜细胞轻度增多，间质炎细胞浸润明显；电镜下肾小球系膜区无电子致密沉积物。（3）金葡菌细胞膜20肽抗原决定簇组尿蛋白增高，伴有血尿；免疫荧光显示多数肾小球均可见大量IgA沉积；光镜下肾小球系膜细胞增多，伴系膜基质轻度增生；电镜下肾小球系膜区和基底膜的内皮细胞下可见高电子密度的致密沉积物。结论金葡菌细胞膜20肽抗原决定簇组诱导的IgAN模型从临床表现和病理学变化与人IgAN极其相似，是3种IgAN模型中最理想的IgAN模型。