Altered steady-state levels of mRNA coding for extracellular matrices in renal tissues of ddY mice, an animal model for IgA nephropathy

Correlations between the steady-state mRNA levels of extracellular matrices using specific cDNA probes for the alpha 1 chain of type IV collagen (alpha 1 (IV) chain); laminin A, B1, and B2 chains; and heparan sulfate proteoglycan (HSPG); and glomerular injuries in ddY mice were evaluated. Eight-, sixteen- and forty-week-old ddY mice were used in this study. ICR mice of the same age served as control. Extracted total RNA of pooled kidneys was fixed on a filter and then hybridized with the cDNA probes. Renal cryostat sections were incubated with rabbit anti-mouse type IV collagen, laminin, and HSPG antisera and then stained with FITC-labeled goat anti-rabbit IgG antiserum. The sections were also stained with FITC-labeled goat anti-mouse IgA, IgM, IgG, and C3 antisera. In light microscopy, the average number of glomerular cells was calculated at each age. Increased expression of extracellular matrices genes for the alpha 1(IV) chain; laminin A, B1, and B2 chains; and HSPG was found in renal tissues of ddY mice. Staining of type IV collagen, laminin, and HSPG was observed in renal tissues of ddY mice at each age. Increased proteinuria in 40-week-old ddY mice might be related to the decrease in glomerular basement membrane HSPG which acts as the anionic sites in such areas. Marked proliferation and or expansion of glomerular cells and mesangial matrices were observed in 40 week-old-ddY mice. The intensity of IgA and C3 deposits in the glomeruli was parallel to the levels of mRNA for such components.(ABSTRACT TRUNCATED AT 250 WORDS)     

Polymorphism of T cell receptor genes and hyper-production of cytokines: their possible contribution to the pathogenesis of IgA nephropathy in ddY mouse]

The ddY mouse has been used as the spontaneous model animal of human IgA nephropathy (IgAN), because kidney lesion as well as immunological abnormalities resemble that of human IgAN. The intensity of mesangial IgA deposition in neonatally thymectomized ddY mice, in which T cell function was impaired, was less severe, indicating that cytokines from T cells determine the amount of mesangial IgA deposition. Therefore ddY mouse may possess a large amount of cytokines due to hyperactivity of T cells. To elucidate the reason for T cell hyperactivity in ddY mice, genetic polymorphism of T cell receptor genes was examined. Though restriction fragment length polymorphism (RFLP) of alpha and beta chain genes is the same as that of normal mice, the RFLP of the gamma chain is unique. Since T cells bearing gamma chain are observed frequently in the tonsil gland or intestinal intraepithelium, which are indispensable lymphoid tissues for IgA production, an uncommon DNA sequence of the gamma chain could contribute to the pathogenesis of IgAN.     

IgA肾病86例临床和病理分析

目的 :了解IgA肾病患者的临床表现及其病理情况。方法 :对 1984年 6月～ 2 0 0 0年 12月间经肾活检证实为IgA肾病患者 86例随访资料进行分析。结果 :以感染为首次发病诱因者 4 2例 ,其中呼吸道感染 36例。存在血尿 79例 ,蛋白尿 83例 ;伴高血压 4 0例 ;发生急性肾衰竭 4例。治疗前内生肌酐清除率 (Ccr>70ml/min 6 2例 ,5 0～ 70ml/min 15例 ,2 5～ 5 0ml/min 8例 ,<2 5ml/min 1例 ;治疗后Ccr>70ml/min 73例 ,5 0～ 70ml/min 5例 ,2 5～ 5 0ml/min 4例 ,<2 5ml/min 4例。除肾小球系膜增生外 ,病理改变以间质炎症和肾小球硬化出现的比例最高 ,其次为肾小管萎缩、间质纤维化等。结论 :IgA肾病的临床表现以蛋白尿和血尿多见 ,且两者合并存在的机会多见 ;部分患者可出现血压升高及肾功能恶化。IgA肾病患者应早期进行肾活检检查     

膜型IgA肾病

肾病是我国常见的肾小球疾病，病理类型很多，但膜型ＩｇＡ肾病极罕见。本文报告３例膜型ＩｇＡ肾病。病理特点是系膜增生的同时，肾小球毛细血管基底膜增厚，并有钉突形成。患者有大量蛋白尿。系膜区有大量ＩｇＡ沉积，毛细血管基底膜外侧有ＩｇＧ沉积。超微结构显示在系膜区及基底膜上皮细胞下均有电子致密物。本文通过免疫荧光和免疫电镜的研究认为，膜型ＩｇＡ肾病是膜型肾小球肾炎与系膜增生型ＩｇＡ肾病的相互重叠。     

Complications of IgA nephropathy in a non-insulin-dependent diabetes model,the Akita mouse

The Akita mouse, which has a mutation (Cys96Tyr) in the insulin 2 gene (Ins2(Akita)), is a model for diabetes. The male Akita mouse has diabetes, while females develop mild diabetes. This study aimed to investigate renal complications in the Akita mouse model, which has been maintained in a heterozygous state Ins2(Akita) (+/-) with a C57BL/6 background (B6). Renal function (BUN, creatinine), serum IgA concentrations and histological changes in the kidneys were evaluated in diabetic and control mice in a B6 background. Five each of male and female mice per group (diabetes vs. control) were killed at 10, 20, 30 and 40 weeks of age. The influence of major histocompatibility antigens (MHC) on renal complications was tested using male diabetic mice in a C3H/He (C3H) background. When compared with controls, diabetic males, but not females, developed impaired renal function with elevation of serum IgA after 30 weeks of age. Diabetic glomerulosclerosis advanced with age in both sexes. Diffuse granular mesangial deposits of IgA were detected by immunofluorescence microscopy in diabetic males after 20 weeks. We tested whether the IgA-associated lesions were influenced by MHC using diabetic males in a C3H background. Similar degrees of diabetic glomerulosclerosis and glomerular IgA deposition were found in mice with C3H and B6 backgrounds. Akita mouse is a unique mouse model showing both mesangial sclerosis and IgA nephropathy.     

Enzymolysis of glomerular immune deposits in vivo with dextranase/protease ameliorates proteinuria, hematuria, and mesangial proliferation in murine experimental IgA nephropathy.

The therapeutic effects of saccharolytic and proteolytic enzymes were investigated in models of IgA nephropathy. Mesangial glomerulonephritis was induced in mice by intravenous injection of preformed soluble immune complexes of dextran sulfate and either IgA (J 558) or IgM (MOPC 104 E) anti-dextran MAb (passive model) or by immunization with DEAE dextran (active model). In the passive model, only 30-40% of dextranase-treated mice given IgA or IgM immune complexes had mesangial Ig or dextran deposits, compared with 100% of saline-treated controls (P less than 0.01). There was no significant difference in mice given only protease. In the active model, dextranase and protease separately each reduced glomerular dextran and C3 deposits, and hematuria (P less than 0.01). Dextranase also reduced the glomerular IgA deposits (20 vs. 100% of saline-treated mice) and the frequency and severity of mesangial matrix expansion (both P less than 0.02), but did not reduce the modest IgG or IgM codeposits. Protease reduced IgG and IgM deposits, proteinuria and mesangial hypercellularity compared with saline (P less than 0.02), but did not diminish IgA, and had no effect on mesangial matrix expansion. The combination of dextranase plus protease attenuated all components of glomerular injury as judged by clinical and pathological parameters, but inactivated dextranase plus inactivated protease had no effect on any parameter. We conclude that enzymatic digestion of antigen and antibody can reduce immune deposits, mesangial proliferation, proteinuria, and hematuria in experimental glomerulonephritis.     

Experimental IgA nephropathy induced by oral immunization

To test the hypothesis that IgA nephropathy can result from a mucosal immune response, mice were orally immunized with one of three protein antigens for 14 wk. Such mice exhibited an essentially pure mucosal antibody response characterized by specific IgA-producing plasma cells in exocrine sites and specific IgA antibodies in serum. Furthermore, 73% of immunized mice had IgA and 88% had immunogen deposited in the glomerular mesangium, and 64% of immunized mice examined ultrastructurally had electron-dense mesangial deposits. All three were present concurrently in 57% of the immunized mice. No differences in regard to IgG or IgM were observed between immunized and control mice for any of these parameters. Mucosal immunization therefore can result in a specific immune response that leads to mesangial deposition of immune complexes containing IgA antibody. In its fundamental features the experimental renal lesion resembles that seen in the human disease IgA nephropathy.     

Transglutaminase is essential for IgA nephropathy development acting through IgA receptors

IgA nephropathy (IgAN) is a common cause of renal failure worldwide. Treatment is limited because of a complex pathogenesis, including unknown factors favoring IgA1 deposition in the glomerular mesangium. IgA receptor abnormalities are implicated, including circulating IgA-soluble CD89 (sCD89) complexes and overexpression of the mesangial IgA1 receptor, TfR1 (transferrin receptor 1). Herein, we show that although mice expressing both human IgA1 and CD89 displayed circulating and mesangial deposits of IgA1-sCD89 complexes resulting in kidney inflammation, hematuria, and proteinuria, mice expressing IgA1 only displayed endocapillary IgA1 deposition but neither mesangial injury nor kidney dysfunction. sCD89 injection into IgA1-expressing mouse recipients induced mesangial IgA1 deposits. sCD89 was also detected in patient and mouse mesangium. IgA1 deposition involved a direct binding of sCD89 to mesangial TfR1 resulting in TfR1 up-regulation. sCD89-TfR1 interaction induced mesangial surface expression of TGase2 (transglutaminase 2), which in turn up-regulated TfR1 expression. In the absence of TGase2, IgA1-sCD89 deposits were dramatically impaired. These data reveal a cooperation between IgA1, sCD89, TfR1, and TGase2 on mesangial cells needed for disease development. They demonstrate that TGase2 is responsible for a pathogenic amplification loop facilitating IgA1-sCD89 deposition and mesangial cell activation, thus identifying TGase2 as a target for therapeutic intervention in this disease.     

Identification of the transferrin receptor as a novel immunoglobulin (Ig)A1 receptor and its enhanced expression on mesangial cells in IgA nephropathy

The biological functions of immunoglobulin (Ig)A antibodies depend primarily on their interaction with cell surface receptors. Four IgA receptors are presently characterized. The FcalphaRI (CD89) expressed by myeloid cells selectively binds IgA1 and IgA2 antibodies, whereas the poly-IgR, Fcalpha/muR, and asialoglycoprotein receptors bind other ligands in addition to IgA. IgA binding by mesangial cells, epithelial cells, and proliferating lymphocytes is also well documented, but the nature of the IgA receptors on these cells remains elusive. A monoclonal antibody (A24) is described here that specifically blocks IgA binding to epithelial and B lymphocyte cell lines. Both the A24 antibody and IgA1 myelomas bind a cell surface protein that is identified as the transferrin receptor (CD71). The transferrin receptor selectively binds IgA1 antibodies, monomeric better than polymeric forms, and the IgA1 binding is inhibitable by transferrin. Transferrin receptor expression is upregulated on cultured mesangial cells as well as on glomerular mesangial cells in patients with IgA nephropathy. The characterization of transferrin receptor as a novel IgA1 receptor on renal mesangial cells suggests its potential involvement in the pathogenesis of IgA nephropathy.     

Detection of activated platelets in urinary sediments by immunofluorescence using monoclonal antibody to human platelet GMP-140 in patients with IgA nephropathy

The presence of activated platelets in the urinary sediments was studied by indirect immunofluorescence using monoclonal antigranular membrane protein (GMP)-140 antibody. GMP-140 is generally expressed on the activated-platelets and -vascular endothelial cells. The purpose of the present study was to determine if the presence of activated platelets in the urinary sediments is correlated with glomerular injuries in patients with IgA nephropathy. Fourteen patients with IgA nephropathy and 11 patients with diffuse mesangial proliferative glomerulonephritis without glomerular IgA deposition (PGN) were examined. The number of activated platelets in the urinary sediments was markedly increased in patients in the advanced stage of IgA nephropathy. The ratio of activated platelets to total platelets in the urinary sediments was also increased in such patients. It appears that the detection of activated platelets in the urinary sediments is useful in determining the degree of histological changes in IgA nephropathy. © 1993 Wiley-Liss, Inc.     

Renal disorders in rheumatoid arthritis]

Glomerulonephritis has been believed to be a rare complication in rheumatoid arthritis (RA). However, recent studies have revealed a focal segmental increase in mesangial cells and matrix in RA patients with hematuria. In our series, proteinuria, hematuria or both abnormalities were recognized in 74 (22%) out of 336 RA cases. Among 119 patients examined by renal biopsy, mild mesangial proliferative glomerulonephritis (GN) was found in 25 patients, of which 22 demonstrated mesangial IgA deposits, by immunofluorescent microscopy. Membranous nephropathy was noticed in 26 cases. Three cases of membranous nephropathy had no history of gold or D-penicillamine treatment. Electron microscopy revealed diffuse thinning of the glomerular basement membrane in 12 cases. The average thickness of the glomerular basement membrane was significantly thinner in RA patients than in normal subjects. The immunological processes associated with rheumatoid factor do not seem to be related to the renal lesions in RA patients.     

102例IgA肾病的临床与病理分析

目的探讨102例原发性IgA肾病患者的临床与病理的特点及其相关性。方法回顾性分析102例经肾活检病理确诊为原发性IgA肾病患者的临床及病理资料。结果原发性IgA肾病患者占同期肾活检患者总数的36.16%,男女发病比例1∶1.27,发病年龄（31.93±10.93）岁,平均病程3（11）个月,发病高峰年龄段20～40岁。IgA肾病患者在临床分型中以尿检异常型（U-ab）最多见,约占38.24%。病理Haas分级中主要为Ⅲ级局灶增生性肾小球病变,约为43.14%。高血脂、高血压和IgA肾病患者肾脏病理损伤程度有关（P〈0.05）。病理Haas分级和24 h尿蛋白定量没有明显的相关性（Spearman相关系数=0.12,P=0.19〉0.05）。结论 IgA肾病的临床、病理具有多样性,有一定相关性但不平行,有必要定期尿检及结合临床表现早期行肾活检以明确肾脏病理诊断。     

原发性膜性肾病合并IgA肾病3例临床病理分析

目的 探讨原发性膜性肾病合并IgA肾病的临床病理特征.方法 分析3例经肾活检病理检查及实验室检查证实的原发性膜性肾病合并IgA肾病患者的临床表现及病理特点.结果 2例患者呈肾病综合征表现,伴或不伴轻微镜下血尿,肾小球基底膜增厚,系膜无明显增生/轻度增生;1例呈慢性肾炎综合征表现,有发作性肉眼血尿并伴有高血压,肾小球基底...     

Mesangial cell autoantigens in immunoglobulin A nephropathy and Henoch-Schönlein purpura.

The autoantigen(s) that we have previously described in human glomeruli, recognized in IgA nephropathy, has (have) been identified as mesangial cell in origin. Cultured mesangial cells expressed 48- and 55-kD components binding IgG isotype autoantibodies (IgG-MESCA) present in sera of patients with both IgA nephropathy and Henoch-Sch?nlein purpura (HSP). IgG-MESCA were not detected in sera of normals, or patients with other autoimmune-mediated glomerulonephritides: anti-glomerular basement membrane disease, Wegener's granulomatosis, or in IgM-mesangial proliferative disease. Binding specificity was proven by F(ab')2 studies in enzyme-linked immunosorbent assay (ELISA) and Western blotting, and there was no significant affinity of IgA or IgM immunoglobulins. Fluorescein isothiocyanate-conjugated IgG from ELISA-positive sera localized to the mesangium and peripheral capillary loops of glomeruli, supporting the belief that the antigen is expressed in normal human renal tissue. However, only about one third of mesangial cells in culture showed affinity for IgG from ELISA-positive sera, suggesting variable expression of the antigen(s) in vitro. The only autoantigen(s) present in glomeruli, and extractable from whole normal glomeruli by the techniques employed, localized on the mesangial cell. In both IgA nephropathy and HSP, autoimmunity was intermittently present, with fluctuating levels of IgG-MESCA detectable in sera. There were positive correlations with the degree of glomerular injury assessed by erythrocyturia and proteinuria in IgA nephropathy, but significance was reached with only the degree of hematuria in HSP. These findings suggest a contributing role in the pathogenesis of the mesangial proliferative lesions and demonstrate autoimmunity common to both IgA nephropathy and HSP.     

雷公藤多甙对IgA肾病大鼠免疫调节的实验研究

目的 观察雷公藤多甙对实验性IgA肾病大鼠的免疫调节作用.方法 采用牛血清白蛋白和葡萄球菌肠毒素复合免疫法建立大鼠实验性IgA肾病模型，比较正常对照组、模型组、雷公藤多甙组大鼠的尿红细胞、24 h尿蛋白、肾功能，以及红细胞C3b受体花环结合率和肾组织病理改变.结果 雷公藤多甙组大鼠的尿红细胞、尿蛋白、血清肌酐、血尿素氮含量均低于模型组（ P〈0.05），红细胞C3b受体花环率高于模型组（ P〈0.05），肾小球系膜区IgA沉积较模型组少，肾功能改善好于模型组.结论 雷公藤多甙对实验性IgA肾病大鼠有较好的治疗作用，对出现的免疫失调有调节作用。     

Detection of glycosylated protein in glomeruli of STZ-induced diabetic rats using the nitroblue tetrazolium (NBT) reaction

Detection of glycosylated protein in renal tissues was determined in streptozotocin (STZ)-induced diabetic rats using the nitroblue tetrazolium (NBT) reaction. The glycosylation of extra-cellular matrix (ECM) components such as laminin and fibronectin was examined in vitro using the same method. Immunofluorescence staining of laminin or type IV collagen was also performed in renal tissues of STZ-induced diabetic rats. There was no significant difference in the intensity of NBT in renal tissues between 4 week STZ-induced diabetic rats and control rats of the same age. The intensity of NBT staining in the glomerular mesangial areas and capillary walls was marked in 12 week diabetic rats. The mean values of fructosamine measured by the NBT reaction in the glycosylated-laminin and fibronectin were increased dose dependently. In immunofluorescence, laminin and type IV collagen were observed significantly in the glomerular mesangial areas and capillary walls of 12 week diabetic rats. However, there was no significant change in renal histopathology in 4 and 12 week diabetic rats. It appears that the non-enzymatic glycosylation and expression of ECM components in glomeruli increased in the early stage of diabetic nephropathy prior to the appearance of marked histologic alterations. In conclusion, non-enzymatic glycosylation of glomerular structural components may play an important role in the initiation of the early stage of renal injuries in diabetes. © 1994 Wiley-Liss, Inc.     

Experimental IgA nephropathy

An animal model for IgA immune complex nephritis was developed. IgA immune complexes formed in vitro with an IgA anti-dinitrophenyl (DNP) derived from MOPC-315 plasmacytoma, and dinitrophenylated bovine serum albumin (DNP-BSA) produced mild focal glomerulonephritis in mice. Similar, but more severe pathological changes were produced with complexes formed in vivo either in normal mice or MOPC-315 tumor-bearing mice. In contrast to the focal nature of the PAS-positive glomerular lesions observed by light microscopy, immunofluorescent examination revealed IgA deposits in all glomeruli. This discrepancy between immunofluorescent and histopathologic findings as well as the distribution of the immune complexes within the affected glomeruli, are some of the features which bear resemblance between this experimental model and human IgA nephropathy. Fixation of complements by DNP-BSA-IgA immune complexes, formed in vitro or in vivo, was shown to occur in the glomeruli of mice with IgA immune complex nephropathy. The pattern of C3 glomerular deposits was similar to that of IgA. However, complement proved to be nonessential for complex deposition. This conclusion is based on the observation that decomplemented mice, although showing no deposition of C3 in their glomerulus, developed glomerular immunohistological changes similar to those observed in experimental mice that were not decomplemented. Polymeric IgA was observed to be critical for renal deposition of complexes and induction of nephritic histological changes. In contrast, monomeric IgA immune complexes failed to produce glomerular deposits. This finding raises the possibility that secretory IgA, which is predominantly polymeric, may play a role in human IgA-associated glomerulonephritis.     

伴新月体形成的青壮年原发性IgA肾病临床病理特征分析

目的分析青壮年原发性IgA肾病伴新月体形成的临床及病理特征。方法选取124例经肾活检确诊为原发性IgA肾病并伴新月体形成的青壮年患者,年龄20～40岁,按新月体占受累小球比例分为2组：A组48例和B组76例。按Katafuchi积分描述病理特征。结果 1）预后：A组24 h尿蛋白定量、尿酸显著高于B组,eGFR、白蛋白显著低于B组,2组比较差异有统计学意义（P〈0.05）;而血压、肌酐、血脂、血糖、血清IgA、血清C3及IgA/C3比值2组之间差异无统计学意义（P〉0.05）。2）病理：2组肾小球、肾小管积分比较差异均有统计学意义（P〈0.05）。结论青壮年患者随着新月体占受累小球比例的增加,临床预后渐趋严重,肾小管间质病理损害亦逐渐加重,临床应积极对青壮年伴新月体形成的IgA肾病患者进行干预治疗,以延缓病情进展。     

Single application of low-dose mycophenolate mofetil-OX7-immunoliposomes ameliorates experimental mesangial proliferative glomerulonephritis

IgA nephropathy, one of the most frequent forms of glomerulonephritis, characterized by mesangial hypercellularity and glomerular extracellular matrix (ECM) expansion, often leads to end-stage renal disease over a prolonged period. We investigated whether antiproliferative treatment in a single low dose specifically targeted to the glomerular mesangium by immunoliposomes (ILs) results in an amelioration of mesangial proliferative glomerulonephritis in rats (anti-Thy1.1 nephritis). Mycophenolate mofetil (MMF) containing ILs was generated that targets the Thy1.1 antigen (OX-7) in rat mesangial cells. Treatment benefit of a single intravenous dose of these ILs given 2 days after disease induction was investigated by stereology, immunohistochemistry, and functional analyses (creatinine, albuminuria) until day +9 and was compared among untreated and free MMF-treated rats using six male Wistar rats per group. MMF-loaded OX7-IL prevented creatinine increase and albuminuria. Stereological analyses of MMF OX7-IL-treated animals yielded 30% reduction of mesangial cells on day +9 and a 40% reduction of glomerular ECM volume on day +5, compared with all of the other nephritic animals. Furthermore, at days +5 and +9 we observed decreased ECM content and decreased glomerular volume (day +5) in the MMF-OX7-IL-treated group compared with the nephritic group treated with free MMF. In conclusion, MMF-OX7-IL-based directed drug delivery represents a novel approach for treating mesangial cell-mediated forms of glomerulonephritis.     

Mesangial autoantigens in IgA nephropathy: matrix synthesis and localization

Primary IgA nephropathy, a chronic nephritis with variable prognosis, is characterized by mesangial immunoglobulin A, frequently with codeposition of other immunoglobulin isotypes and complement components accompanying matrix expansion typically preceding glomerular scarring. Glomerular immunoglobulin G, when present, is localized to the mesangial periphery found variably in repeat biopsies. IgG anti-mesangial cell autoantibodies (IgG-MESCA) in sera of patients with IgA nephropathy, specific by F(ab')(2) binding to 48- and 55-kD autoantigen(s) could account for these deposits, but their in vivo localization, and the functional role in promoting scarring is unknown. A specific monoclonal antibody raised previously to these human mesangial cell autoantigen fractions, in this study localized to similar glomerular sites, reinforcing the view that immunoglobulin G deposition in vivo is a result of antibody-autoantigen binding. The propensity for immunoglobulin G more than other isotypes to enhance inflammation prompted study of its functional role in vitro. Using cultured human mesangial cells in a complement-free tritiated glycosaminoglycan synthesis single outcome assay, purified IgG fractions from patient sera increased matrix production in a dose-dependent manner compared with controls. At a constant total IgG concentration, matrix synthesis was proportional to the titre of IgG-MESCA. Autoreactive IgG stimulated matrix synthesis when compared with controls or IgA fractions. These findings are consistent with IgG-MESCA autoantibodies enhancing mesangial matrix synthesis in vitro, which suggests that in IgA nephropathy, similar prosclerotic autoimmune mechanisms might operate. Recombinant TGFbeta(1) also induced matrix synthesis, raising the possibility that both autoimmune mechanisms and those TGFbeta(1)-dependent are functional or inter-related. The pathogenesis of glomerular scarring and loss in IgA nephropathy may include, in part, these mechanisms.