Podocyte injury induced by mesangial-derived cytokines in IgA nephropathy

Background. We have previously documented that human mesangialcell (HMC)-derived tumour necrosis factor- (TNF-) is an importantmediator involved in the glomerulo-tubular communication inthe development of interstitial damage in IgA nephropathy (IgAN).With the strategic position of podocytes, we further examinedthe function of podocytes in IgAN. Methods. Podocyte markers were examined in renal tissues byimmunofluorescence. In vitro experiments were conducted withpodocytes cultured with polymeric IgA (pIgA) or conditionedmedium prepared from HMC incubated with pIgA (IgA–HMCconditioned medium). Results. Glomerular immunostaining for nephrin or ezrin wassignificantly weaker in patients with IgAN. The immunostainingof IgA and nephrin was distinctly separate with no co-localization.In vitro experiments revealed no effect of pIgA on the expressionof these podocyte proteins as IgA from IgAN patients did notbind to podocytes. In contrast, IgA conditioned medium preparedfrom IgAN patients down-regulated the expression of these podocyteproteins as well as other podocyte markers (podocin and synaptopodin)in cultured podocytes. The mRNA expression of nephrin, erzin,podocin but not synaptopodin correlated with the degree of proteinuriaand creatinine clearance. The down-regulation was reproduciblein podocytes cultured with TNF- or transforming growth factor-β(TGF-β) at concentration comparable to that in the IgA–HMCconditioned medium. The expression of these podocyte proteinswas restored partially with a neutralizing antibody againstTNF- or TGF-β and fully with combination of both antibodies. Conclusion. Our finding suggests podocyte markers are reducedin IgAN. An in vitro study implicates that humoral factors (predominantlyTNF- and TGF-β) released from mesangial cells are likelyto alter the glomerular permeability in the event of proteinuriaand tubulointerstitial injury in IgAN.     

Activation of complement in IgA nephropathy

Considerable evidence supports a role for the complement system in the pathogenesis of IgA nephropathy (IgAN). The alternative pathway components C3 and properdin (P) and the membrane attack complex (C5b-9) are generally found in the mesangial deposits in IgAN, while the classical pathway components C1q and C4 are usually absent. This pattern of immunofluorescence staining for complement components suggests activation of the alternative and terminal pathways in most patients. Despite normal serum concentrations of C3 and other complement proteins, fragments generated by activation of C3, including iC3b, C3d, and iC3b-C3d neoantigen, and sometimes C4, are often detected in plasma. We found that the severity of the histologic changes in the renal biopsy specimens correlated with plasma iC3b-C3d neoantigen concentrations as measured by an enzyme-linked immunosorbent assay. However, no other clinical feature correlated with the plasma concentrations of this neoantigen.     

肾小管上皮细胞转分化在慢性移植肾肾病中的作用

目的探讨肾小管上皮细胞-肌成纤维细胞转分化在慢性移植肾肾病(CAN)的发生、发展中的作用。方法36例移植肾穿刺标本分为正常组(N组),CAN组(C组),依Banff 97标准将C组按CANⅠ、Ⅱ、Ⅲ级分为C_1、C_2、C_3组,每组9例。免疫组化染色半定量分析比较α-平滑肌肌动蛋白(α-SMA)、波形蛋白(VIM)、角质蛋白(CK_(AEI/AE3))和转化生长因子β1(TGF-β1)在各组中的表达,线性相关分析TGF—β1和α-SMA、VIM、CK_(AE1/AE3)表达的相关性。结果C_1、C_2、C_3组α-SMA表达积分分别为0．95±0．07、1．78±0．12、2．42±0．31,VIM表达积分分别为0．74±0．05、1．31±0．18、2．34±0．25,组间呈递增趋势,均明显高于N组α-SMA表达积分0．07±0．02、VIM表达积分0．09±0．02(P＜0．05)；移植肾组织中TGF-β1表达与α-SMA、VIM呈正相关(r分别为0．73、0．68,P＜0．05),而与CKAE1/AE3表达呈负相关(r=-0．71,P＜0．05)。结论肾小管上皮细胞-肌成纤维细胞转分化参与了CAN的发生、发展,而局部肾组织中TGF-β1的表达上调可能是介导肾小管上皮细胞转分化的重要原因。     

Immunoglobulin-producing cells in IgA nephropathy

The number of peripheral blood mononuclear cells (PBMC) producing IgA, IgG and IgM spontaneously, after in vitro polyclonal stimulation with pokeweek mitogen (PWM) and in response to autologous mixed lymphocyte reaction (AMLR), were determined by a protein A hemolytic plaque assay in 23 patients with IgA nephropathy confirmed by renal biopsies and in 24 normal controls. The geometric mean of circulating IgA-producing cells in Berger's disease (689 +/- 1.73 cells/10(6) PBMC) was increased when compared with the normal controls (332 X divided by 1.52 cells/10(6) PBMC; p less than 0.001). To a lesser degree, there was also an increase in the number of IgG-secreting cells (98 +/- 3.97 cells/10(6) PBMC vs. 38 +/- 2.90 cells/10(6) PBMC; p less than 0.05). After PWM stimulation, although the number of IgA-producing cells was increased in patients with IgA nephropathy, no significant differences were observed between the 2 groups. In response to AMLR, the number of IgA-secreting cells was significantly higher in the cases with Berger's disease (1,979 +/- 1.76 cells/10(6) non-T cells vs. 783 +/- 1.95 cells/10(6) non-T cells; p less than 0.001). Although it did not reach statistical significance, the patient group had also an increase in the number of IgG-producing cells (884 +/- 2.64 cells/10(6) non-T cells vs. 317 +/- 5.05 cells/10(6) non-T cells). These data support the existence of some abnormalities in the mechanisms regulating the synthesis of IgA in Berger's disease which might contribute to its pathogenesis.     

Antigen presentation by renal tubular epithelial cells

The interaction between immune effector cells such as T lymphocytes and parenchymal cells in organ-specific immune injury is dynamic. It is now appreciated that the specificity, intensity, and eventual destructive effects of such interactions can be greatly influenced by responses of the target issue. Renal tubular cells are particularly well suited to participate in such immune collaborations. (1) They are exposed to innumerable potentially immunogenic peptides from blood and glomerular filtrate and have pathways to further process these peptides; (2) they express surface molecules which facilitate their engagement to T cells; and (3) they can produce proinflammatory cytokines. In the models of immune-mediated tubulointerstitial injury that are currently studied, there has been a great interest in defining the T lymphocytes that initiate, accelerate, or suppress disease. Surprisingly, there has been relatively little attention on defining the tubular cell responses that regulate these immune-mediated processes. This review will therefore focus on this intriguing aspect of immune tubular injury and relate what is known about antigen presentation by tubular cells in autoimmune renal disease.     

Role of endothelial cells in IgA nephropathy

Summary: Various polyspecific autoantibodies have been described in the sera of patients with IgA nephropathy, including anti-IgG, anti-IgA, antigalactosyl, antifibronectin and antimesangial antibodies. We and other authors have demonstrated the presence of antivascular endothelial cell (VEC) antibodies, in up to 32% of patients with IgA nephropathy. These antibodies were directed against molecules on the endothelial cell surface. Some of these antibodies were directed against HLA class I antigens; the majority, however, were reactive against antigens present on unstimulated endothelial cells, as prior stimulation of the cells with interferon-γ or interleukin 1 did not result in an increase in anti-VEC activity of the sera. The clinical significance of these anti-VEC antibodies in IgA nephropathy is unknown. A significant correlation was demonstrated between these antibodies and the presence of heavy proteinuria. A significant association was also shown between the presence of these antibodies and the histopathologic markers of activity such as crescents and focal and segmental necrotizing lesions, as well as immunoglobulin and C3 deposition in the vessel walls.     

慢性马兜铃酸肾病患者肾小管上皮细胞转分化的研究

目的探讨慢性马兜铃酸肾病。肾小管上皮细胞转分化与肾间质纤维化的关系。方法以慢性马兜铃酸肾病患者的肾组织为标本,作常规Masson染色化病理检查;用天狼星红组织化学(组化)染色检查胶原Ⅰ、Ⅲ表达;用免疫组化染色检查角蛋白(CK)、α-平滑肌肌动蛋白(α-SMA)、波形蛋白(Vim)及转化生长因子-β1(TGF-β1)表达。对结果进行定量或半定量分析。结果 肾间质Masson染色纤维化面积及胶原Ⅰ、Ⅲ面积,与肾小管间质α-SMA及Vim阳性表达面积呈显著正相关(P<0.05),与肾小管CK阳性表达面积呈显著负相关(P<0.05);病变过程中健存肾小管TGF-β1表达明显增强。结论慢性马兜铃酸肾病患者的肾小管上皮细胞可转分化为肌成纤维细胞,参与肾间质纤维化,而这细胞转分化很可能与其自身高表达TGF-β1相关。     

Atubular glomeruli and glomerulotubular junction abnormalities in diabetic nephropathy

Atubular glomeruli (AG) have been described in several renal disorders. However, little attention has been paid to AG in diabetic nephropathy (DN). Preliminary studies suggested that tip lesions were frequently present in type 1 diabetic (D) patients with proteinuria. The aim of this study was to determine the frequency of AG and their possible relationship with tip lesions in DN. Renal biopsies from eight proteinuric type 1 D patients with normal to moderately reduced GFR (76 +/- 26 ml/min per 1.73 m(2)) and eight normal subjects were studied by light (LM) and electron microscopy (EM). Glomerular volume, volume of the glomerular corpuscle, which is tuft, and the fractional volumes of proximal, distal, and atrophic tubules per cortex were estimated using appropriate stereologic methods. Glomerulotubular junctions were examined on serial sections and classified into glomeruli attached to: normal tubules (NT); short atrophic tubules (SAT); long atrophic tubules (LAT); atrophic tubules with no observable glomerular opening (ATNO); and atubular glomeruli (AG). EM studies showed typical diabetic changes in biopsies, including increased GBM width (P < 0.00001) and mesangial fractional volume (P < 0.0001) and decreased filtration surface density (P < 0.01) compared with normal subjects. Seventeen percent of glomeruli in the D patients were atubular, and 51% were attached to atrophic tubules. Tip lesions were present in all SAT, 64% of LAT, 82% of ATNO, and only 9% of NT and were never observed in normal subjects. The relative volume of AG was smaller than glomeruli in other categories (P < 0.05). Fractional volume of proximal (P < 0.01) and distal (P <0.01) tubules per cortex were decreased, while fractional volume of cortical interstitium (P <0.00001) and atrophic tubules (P <0.01) were increased in D patients. Fractional volume of atrophic tubules, %AG, and percent of glomeruli with tip lesion explained 94% of the GFR variability in diabetic patients (P <0.05). Thus, AG and glomerulotubular junction abnormalities may be important in the development and progression of DN.     

The number of CD10-positive glomerular epithelial cells reflects renal prognosis in IgA nephropathy patients

BACKGROUND: The glomerular epithelial cells play an important role in glomerular filtration of the kidney. The disruption of these cells contributes to the development of glomerulosclerosis. The present study was performed to elucidate whether loss of the glomerular epithelial cells is associated with renal injury in patients with IgA nephropathy. PATIENTS AND METHODS: Thirty renal biopsy specimens from IgA nephropathy, 12 from minor glomerular abnormalities and 5 from normal controls were observed. The specimens from IgA nephropathy were divided into 2 groups: Group IgA-1, including 11 patients who had received a follow-up renal biopsy because of deterioration of renal function, and Group IgA-2, consisting of the remaining 19 patients without follow-up biopsy. Immunohistochemistry was performed using a monoclonal antibody against CD10 antigen that appears on mature epithelial cells of glomeruli. RESULTS: The average number of CD10-positive glomerular epithelial cells (GECs) was significantly lower in IgA nephropathy than in either minor glomerular abnormalities or the normal controls. In IgA nephropathy, there were significant correlations of the GECs with renal functions. The GECs were reduced along with the progression of histopathological damage. In group IgA-1, the GECs were significantly reduced at the second biopsy compared with the first biopsy, and significantly fewer in group IgA-1 than in group IgA-2 at the first biopsy. The GECs showed a significant correlation with renal prognosis during the follow-up period. CONCLUSIONS: The reduction of GECs was associated with renal dysfunction, histopathological damage and renal prognosis. The GECs may be a useful predictor of renal prognosis in IgA nephropathy.     

Clinical and pathology features of IgA nephropathy with active tubular interstitial lesions

Objective To investigate the clinical and pathological characteristics of IgA nephropathy (IgAN) in association with active tubular interstitial lesions. Methods 148 patients who were diagnosed as IgAN by renal biopsy and admitted to Zhejiang Provincial People's Hospital from March 2014 to December 2014 were enrolled. They were divided into IgAN with active tubular interstitial lesions group (IgAN-ATIL group, 23 patients) and IgAN without active tubular interstitial lesions group (control group, 125 patients). Clinical and pathological characteristics were retrospectively analyzed. Multivariate logistic regression analysis was used to analyze the influence factors. Results The prevalence of ATIL in 148 IgAN patients was 15.5%. IgAN-ATIL group showed an older average age and more higher proportion of medication history (antibiotics, diuretics, nonsteroidal anti-inflammatory drugs, etc) than those in control group. There were significant differences in Alb, eGFR, Scr, BUN, 24-hour urinary protein quantity, urinary NGAL and urinary RBC count between two groups (P＜0.05, respectively). A moderate of tubulointerstitial lesions of IgAN-ATIL group was shown, while the control group was mainly mild lesions. Multivariate logistic regression analysis showed that age, medication history and the urinary NGAL level were independent risk factors of IgAN-ATIL. Conclusions IgAN patients with active tubular interstitial lesions had more severe clinical manifestations and chronic interstitial lesions. The age, medication history (antibiotics, diuretics, nonsteroidal anti-inflammatory drugs, etc) and the urinary NGAL level were independent risk factors of IgAN-ATIL.     

氧化应激介导糖尿病大鼠肾小管上皮细胞转分化及普罗布考的干预作用

目的 研究氧化应激在糖尿病肾病（DN）大鼠肾小管上皮细胞转分化中的作用,探讨抗氧化剂普罗布考对大鼠DN的肾脏保护作用。 方法 30只雄性SD大鼠随机分为正常对照组、DN组和普罗布考干预组（1％普罗布考饮食）,每组10只。分别于第3周、第8周及第12周检测24 h尿蛋白（UTP）;12周末检测各组大鼠血糖、血脂（胆固醇、三酰甘油）、Scr、肌酐清除率（Ccr）、肾脏组织匀浆液丙二醛（MDA）含量及谷胱甘肽过氧化物酶（GSH-Px）活性。肾组织病理切片行 HE和Masson染色;采用免疫组化和Western印迹检测肾组织核转录因子Sp1、α平滑肌肌动蛋白（α-SMA）及E钙黏蛋白（E-cadherin）表达。 结果 与正常对照组比较,DN组血糖、Scr、肾组织匀浆MDA和24 h UTP水平显著增高（均P < 0.01）,Ccr显著降低（P < 0.01）;肾组织肾小管损伤分数、α-SMA和 Sp1蛋白表达水平明显增高（均P < 0.01）;肾组织E-cadherin蛋白表达明显下调。肾组织MDA含量分别与α-SMA及Sp1蛋白表达呈正相关（r ＝ 0.896,P < 0.01;r ＝ 0.862,P < 0.01）,与E-cadherin蛋白表达呈负相关（r = -0.673, P < 0.01）。普罗布考干预组Scr、24 h UTP、肾组织MDA、肾小管损伤分数及肾组织α-SMA、 Sp1蛋白表达水平较DN组均明显降低（均P < 0.01）;Ccr和肾组织E-cadherin蛋白表达水平较DN组均明显增加（均P < 0.01）。 结论 氧化应激在DN大鼠肾小管上皮细胞转分化中起重要作用。普罗布考可能通过抗氧化、下调肾组织Sp1蛋白表达及抑制肾小管上皮细胞转分化延缓DN大鼠肾脏病变进展。     

Hyperuricemia and hypertriglyceridemia indicate tubular atrophy/interstitial fibrosis in patients with IgA nephropathy and membranous nephropathy

International Urology and Nephrology - Hyperuricemia (HUA) and hypertriglyceridemia (HTG) were very common in chronic kidney disease (CKD) and associated with accelerated progression of CKD. This...     

Gouty kidney associated with membranous nephropathy: participation of renal tubular epithelial antigen

Histological studies were performed on 3 patients with gout and proteinuria measured at 1.0 g a day or more. Light microscopy revealed diffuse thickening of the glomerular capillary walls accompanied by spike formation and bubble-like appearance as well as tophaceous granuloma in the interstitium, tubular atrophy and benign nephrosclerosis. Immunofluorescence technique showed fine granular deposits of IgG and C3 along the glomerular capillary walls together with the renal tubular epithelial antigen (RTE) in 1 patient. Subepithelial dense deposits were also observed by electron microscopy. These findings suggest that the association of membranous nephropathy should be considered in patients with gout having moderate to severe proteinuria and that RTE may be involved in the pathogenesis of subepithelial deposits in gouty membranous nephropathy.