Synaptopodin expression in idiopathic nephrotic syndrome of childhood

BACKGROUND: Synaptopodin is a proline-rich protein intimately associated with actin microfilaments present in the podocytes' foot processes. We investigated for synaptopodin expression in children with idiopathic nephrotic syndrome (INS), including minimal change disease (MCD), diffuse mesangial hypercellularity (DMH), and focal segmental glomerulosclerosis (FSGS); in children with congenital nephrotic syndrome of the Finnish type (CNF); and in normal kidney tissue. In particular, we examined whether an association exists between synaptopodin expression in podocyte cells and the response to steroids in INS, and whether synaptopodin expression can predict FSGS upon the initial kidney biopsy in children who progress from MCD or DMH to FSGS. METHODS: Immunohistochemistry was performed for synaptopodin expression on renal tissues from MCD (N = 18), DMH (N = 7), FSGS (N = 13), CNF (N = 9), and normal children (N = 7). Synaptopodin expression in nonsclerosed glomeruli was quantitated by computerized image analysis on the Optimastrade mark software for both luminance (L) and percentage of glomerular area (A). RESULTS: Synaptopodin expression was absent in areas of sclerosis. In nonsclerosed glomeruli, synaptopodin was significantly less expressed in all groups of INS and in CNF compared with normal (P < 0.0001 for both L and A, in each MCD, DMH, FSGS, and CNF). In INS, synaptopodin expression decreased in order from MCD to DMH to FSGS, reaching statistical significance between MCD and FSGS (P = 0.001 for L and P = 0.05 for A). Greater synaptopodin expression in podocytes was associated with a significantly better response to steroid therapy (P < 0.05 for both L and A). On the other hand, the expression of synaptopodin did not predict progression of MCD or DMH to FSGS. CONCLUSION: We conclude that measurement of synaptopodin has the potential to be used as a marker to study the alteration in podocyte cell and response to therapy in INS.     

Reduced podocin expression in minimal change disease and focal segmental glomerulosclerosis is related to the level of proteinuria

Background

Glomerular podocyte molecules are involved in the pathogenesis of congenital nephrotic syndrome. However, their role in primary nephrotic syndrome is not clear. This study investigated the expression of nephrin, podocin and synaptopodin in primary nephrotic syndrome.

Methods

Eighty-seven patients with primary nephrotic syndrome including minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), membranous nephropathy (MN) and membranoproliferative glomerulonephritis Type I (MPGN) were included in the study. Glomerular expression of nephrin, podocin and synaptopodin was studied in renal biopsies by immunofluorescence and immunohistochemistry. Correlation of expression with clinical and biochemical parameters was performed.

Results

The pattern of expression for all podocyte proteins in controls was uniform fine granular along the capillary walls towards the visceral epithelial cell aspect. Glomerular expression of nephrin was present in all renal biopsies and was similar to that in controls. Glomerular synaptopodin expression was seen in all MN and MPGN patients, while it was seen in 74 % (17/23) MCD and 93.5 % (29/31) FSGS. Reduced synaptopodin expression showed no correlation with clinical and biochemical factors. Podocin expression was present in 5/23 MCD (22 %), 3/31 FSGS (9.6 %), 13/17 MN (76.4 %) and 13/16 MPGN (81 %) patients. The reduced expression of podocin significantly correlated with the degree of proteinuria (p = 0.032). No correlation with age, gender and serum creatinine level was observed.

Conclusion

Reduction of glomerular podocin expression found in MCD and FSGS is related to the amount of proteinuria. Our findings suggest that alteration in podocyte phenotype may not be a primary event and may reflect the degree of podocyte injury in primary nephrotic syndrome.     

肾病综合征患者肾组织podocin的表达

目的 观察不同病理类型&#65380; 不同激素反应性肾病综合征(NS)患者肾小球足细胞中podocin的表达和分布特征&#65377;方法 肾组织作冰冻切片免疫荧光双染色, 以激光共聚焦显微镜采集图像&#65377;与定位标志Ⅳ型胶原α3链比较&#65377; 受检NS患者21例, 其中局灶节段性肾小球硬化(FSGS)12例(难治性7例, 非难治性5例)&#65380; 微小病变(MCD)5例&#65380; 膜性肾病(MN)4例;正常肾组织对照3例&#65377;采用LSM 510图像处理系统进行处理&#65377;荧光强度以吸光度表示&#65377; 结果 (1)podocin在正常肾组织沿肾小球基底膜呈连续&#65380; 线形分布&#65377;部分FSGS患者podocin的分布呈点状&#65380; 短线条状, 少数患者未见podocin沉积&#65377;(2)FSGS患者肾小球中podocin表达量(80.5±33.5)与对照正常肾组织(138.4±38.1)比较,显著减少(P=0.0211), 其中难治性FSGS(67.2±30.5)与正常肾组织的差异有统计学意义(P=0.0131); 非难治性FSGS患者(99.0±31.0)与正常肾组织的差异无统计学意义(P=0.1585)&#65377;(3)MCD(112.1±47.6)&#65380; MN(92.5±34.8)患者podocin的表达量亦降低,与正常肾组织比较,无统计学意义(P=0.4497, P=0.1570)&#65377;(4)不同病理类型各组NS患者肾小球中podocin表达量的差异均无统计学意义(P > 0.05)&#65377;结论 FSGS的NS患者肾小球中podocin的表达减少, 难治性FSGS患者尤为明显, 部分FSGS患者podocin分布发生改变&#65377;podocin的检测可能在FSGS激素疗效评价方面有一定价值&#65377;     

Podocyte proteins in Galloway-Mowat syndrome

Galloway-Mowat syndrome is an autosomal recessive disorder characterized by early onset nephrotic syndrome and central nervous system anomalies. Mutations in podocyte proteins, such as nephrin, α-actinin 4, and podocin, are associated with proteinuria and nephrotic syndrome. The genetic defect in Galloway-Mowat syndrome is as yet unknown. We postulated that in Galloway-Mowat syndrome the mutation would be in a protein that is expressed both in podocytes and neurons, such as synaptopodin, GLEPP1, or nephrin. We therefore analyzed kidney tissue from normal children (n=3), children with congenital nephrotic syndrome of the Finnish type (CNF, n=3), minimal change disease (MCD, n=3), focal segmental glomerulosclerosis (FSGS, n=3), and Galloway-Mowat syndrome (n=4) by immunohistochemistry for expression of synaptopodin, GLEPP1, intracellular domain of nephrin (nephrin-I), and extracellular domain of nephrin (nephrin-E). Synaptopodin, GLEPP1, and nephrin were strongly expressed in normal kidney tissue. Nephrin was absent, and synaptopodin and GLEPP1 expression were decreased in CNF. The expression of all three proteins was reduced in MCD and FSGS; the decrease in expression being more marked in FSGS. Synaptopodin, GLEPP1, and nephrin expression was present, although reduced in Galloway-Mowat syndrome. We conclude that the reduced expression of synaptopodin, GLEPP1, and nephrin in Galloway- Mowat syndrome is a secondary phenomenon related to the proteinuria, and hence synaptopodin, GLEPP1, and nephrin are probably not the proteins mutated in Galloway-Mowat syndrome. Received: 27 April 2001 / Revised: 15 June 2001 / Accepted: 18 June 2001     

肾小球疾病患者尿沉渣足细胞分子podocin和podocalyxin分析

目的：以ELISA法检测尿沉渣足细胞podocin,podocalyxin排泌并观察其与不同肾小球疾病的关系。方法：共收集我院自2010年5月～8月以来行肾活检证实为肾小球疾病的患者,收集其临床资料,并以ELISA法检测尿沉渣足细胞分子podocin,podocalyxin。结果：共40个患者,男15例,女25例,平均年龄（38.27±16.33）岁,增殖性肾小球疾病患者19例：IgA肾病10例,新月体性肾炎2例,IgM肾病2例,Ⅳ（A/G）型狼疮性肾炎5例;非增殖性肾小球疾病患者19例：微小病变型（MCD）5例,局灶节段硬化性肾小球肾炎（FSGS）8例,膜性肾病（MN）6例,另原发性肾淀粉样变性2例,对照健康自愿者10例。尿podocin分子排泌在正常对照组最低,在增殖性肾小球疾病和非增殖性肾小球疾病间差异无统计学意义（P〉0.05）,增殖性肾小球疾病尿podocin排泌高于肾淀粉样变性患者（P〈0.05）。新月体肾炎的尿podocin排泌显著高于其他肾小球疾病（P〈0.05）,后依次FSGS,IgA肾病,狼疮性肾炎,MN,IgM肾病,MCD;尿沉渣podocalyxin排泌在正常对照组最低,而增殖性肾小球肾炎和非增殖性肾小球肾炎间差异无统计学意义（P〉0.05）。新月体肾炎尿podocalyxin排泄量最高,其后依次为FSGS,IgA肾病,MN,狼疮性肾炎,MCD,IgM肾病,以肾淀粉样变性最低。尿podocalyxin与podocin呈正相关,尿podocin与血C3呈负相关。结论：ELISA法检测尿沉渣足细胞分子检测可对肾小球疾病患者的肾病理类型提供参考,以正常人尿podocin,podocalyxin排泌最少,增殖性肾小球疾病和非增殖性肾小球疾病间差异无统计学意义,新月体性肾炎尿沉渣podocin及Podocalyxin高于其他疾病患者,FSGS患者的尿沉渣podocin及Podocalyxin排泌量也较多,肾淀粉样变性患者的尿沉渣podocin及Podocalyxin最低,血清C3与尿podocin的排泌呈负相关。     

Morphometric insights into nephrotic syndrome in children: Are we any wiser?

Summary: The present study was undertaken in the hope that conflicting opinions concerning interrelationships among minimal change disease (MCD), mesangial proliferative glomerulonephritis (MPG) and focal segmental glomeruloscierosis (FSGS) might be elucidated by morphometric methods performed by image analysis, as well as to study whether serum creatinine and changes in quantitatively analysed glomeruli could correlate with the interstitial fibrosis in these glomerulopathies. Fifteen renal biopsy specimens from children with MCD, 10 with primary MPG and 12 with FSGS for whom both light and electron microscopy as well as immunofluorescence microscopy and full clinical data were available, were examined quantitatively. As a control five biopsy and 10 autopsy specimens of the normal kidneys were used. Our quantitative study showed that in MCD, MPG and FSGS glomerular and interstitial values differed from normal. Morphometric differences between MPG and both MCD and FSGS groups were also shown. Although the mean values of total glomerular area and relative interstitial volume were increased in FSGS patients, in total glomerular cells per unit of glomerular area and mesangium (% of total glomerular area) were similar in both MCD and FSGS groups. In MPG strong positive correlations existed between interstitial volume and serum creatinine, interstitial volume and total glomerular cells per unit of glomerular area as well as between interstitial volume and glomerular mesangium (% of total glomerular area). In FSGS there was significant positive correlation between interstitial volume and serum creatinine. In the MCD group all correlations were weak and not significant. In conclusion, our morphometric studies suggest a close relationship between MCD and FSGS, and indicate that MPG is a separate morphologic entity in children.     

MicroRNA-206 and its down-regulation of Wilms’Tumor-1 dictate podocyte health in adriamycin-induced nephropathy

Background: Focal segmental glomerulosclerosis (FSGS) is a frequent and severe glomerular disease characterized by destabilization of podocyte foot processes. Emerging evidence suggests that microRNAs play crucial roles in podocyte homeostasis. The aim of the present study was to determine the role of miR-206 in podocyte injury and to elucidate the mechanisms responsible for the damage to podocyte. Methods: FSGS nephropathy model was induced by a single intravenous injection of Adriamycin (ADR) in BALB/c mice and the levels of proteinuria were measured on week of 1,3,5. The conditionally immortalized mouse podocyte cell line 5 was either transfected with microRNA mimics or negative control. Real-time PCR analysis was conducted to demonstrate the microRNA level in the glomeruli. Expression of Wilms’ tumor-1 (WT1) and synaptopodin were detected by immunofluorescence and western blotting. Results: The results revealed that miR-206 was up-regulated in ADR nephropathy mice, which led to severe podocyte injury and inhibited the expression of WT1 and synaptopodin. Using luciferase reporter assays, WT1 was identified as a target gene of miR-206. In vitro, over expression of miR-206 induced WT1 and synaptopodin degradation and actin rearrangement, initiating a catastrophic collapse of the entire podocyte-stabilizing system. Conclusions: Over expression of miR-206 promotes podocyte injury via downregulation of WT1, which provides a new pathogenic mechanism for FSGS and miR-206 may be a potential therapeutic target.     

Posttransplantation relapse of FSGS is characterized by glomerular epithelial cell transdifferentiation

This study examined six cases of idiopathic nephrotic syndrome with primary lesions of focal segmental glomerulosclerosis (FSGS) that relapsed after renal transplantation. The glomerular lesions comprised the cellular, the collapsing, and the scar variants of FSGS and showed shedding of large round cells into Bowman's space and within the tubular lumens. Immunohistochemistry and confocal laser microscopy carried out on kidneys with FSGS relapse disclosed several phenomena. (1) Some podocytes that expressed podocalyxin, synaptopodin, and glomerular epithelial protein-1 were detached from the tuft and were free in the urinary space. (2) In the cellular variant, most podocytes had lost podocyte-specific epitopes (podocalyxin, synaptopodin, glomerular epithelial protein-1, Wilm's tumor protein-1, complement receptor-1, and vimentin). In the scar variant, these podocyte markers were absent from cobblestone-like epithelial cells and from pseudotubules. (3) Podocytes had acquired expression of various cytokeratins (CK; identified by the AE1/AE3, C2562, CK22, and AEL-KS2 monoclonal antibodies) that were not found in the podocytes of control glomeruli. Parietal epithelial cells expressed AE1/AE3 CK that were faintly, if ever, found on the parietal epithelial cells of normal glomeruli. (4) Numerous cells located at the periphery of the tuft or free in Bowman's space and within tubular lumens expressed macrophagic epitopes (identified by PGM1 [CD68], HAM56, and 25F9 monoclonal antibodies). These macrophage-like cells expressed the activation epitopes HLA-DR and CD16. (5) A number of these cells coexpressed podocalyxin + AE1/AE3 CK, podocalyxin + CD68, and CD68 + AE1/AE3. These findings suggest that in primary FSGS relapsing on transplanted kidneys, some "dysregulated" podocytes, occasionally some parietal epithelial cells, and possibly some tubular epithelial cells undergo a process of transdifferentiation. This process of transdifferentiation was especially striking in podocytes that acquired macrophagic and CK epitopes that are absent from normal adult and fetal podocytes.     

Cloning of rat homologue of podocin: expression in proteinuric states and in developing glomeruli

Podocin is identified as a product of the gene mutated in a patient with autosomal recessive steroid-resistant nephrotic syndrome. Although podocin is reported to be located at the slit diaphragm area, the precise role of podocin for maintaining the barrier function of the slit diaphragm has not been clearly elucidated. A rat homologue of podocin was cloned, and the expression of podocin was investigated and then compared with the nephrin and the ZO-1 expressions in rat experimental proteinuric models and in developing glomeruli. Amino acid sequences of rat and human podocin are highly homologous (84.3% identity). The domain structure of podocin is also highly conserved between rat and human. The mRNA expression for podocin was detected in glomeruli and the nerve tissues. The localization of podocin has close proximity to that of nephrin in normal adult rat glomeruli. Podocin staining was restricted to the basal side of the podocyte of the early developing stage, whereas nephrin staining was detected on the basolateral surface of podocyte. The redistribution of podocin was observed in the anti-nephrin antibody (ANA)-induced nephropathy and puromycin aminonucleoside (PAN) nephropathy. The redistribution of podocin paralleled with nephrin in ANA nephropathy but not in PAN nephropathy. Podocin is observed at the site of tight junction newly formed in proteinuric state in PAN nephropathy. It is postulated that podocin is one of the critical components of a slit diaphragm for maintaining the barrier function of the glomerular capillary wall.     

Intra-renal and urinary mRNA expression of podocyte-associated molecules for the estimation of glomerular podocyte loss

Background: Podocyte loss plays an important role in the pathogenesis of diabetic nephropathy, but counting the number of glomerular podocyte in renal biopsy specimen is a labor-intensive task. We study whether intra-renal and urinary messenger RNA expression of podocyte-associated molecules could be used to estimate glomerular podocyte number in patients with diabetic nephropathy. Method: We studied 21 consecutive patients with biopsy-proven diabetic nephropathy. The intra-renal and urinary mRNA expression of nephrin, podocin, and synaptopodin were measured by real-time quantitative polymerase chain reaction. Podocyte number was determined in micro-dissected glomerulus. The degree of histological scarring was quantified by morphometric analysis. Results: Glomerular podocyte number correlated with intra-renal expression of nephrin (r = 0.510, p = 0.044), podocin (r = 0.605, p = 0.013), and synaptopodin (r = 0.480, p = 0.060). Glomerular podocyte number also significantly correlated with urinary expression of synaptopodin (r = 0.595, p = 0.019) but not other targets. Baseline renal function correlated with intra-renal expression of nephrin (r = 0.617, p = 0.005), synaptopodin (r = 0.474, p = 0.040), and podocin (r = 0.443, p = 0.057). The degree of tubulointerstitial scarring also inversely correlated with intra-renal expression of nephrin (r = ?0.462, p = 0.047), podocin (r = ?0.458, p = 0.049), and synaptopodin (r = ?0.500, p = 0.029) but not with urinary gene expression. Conclusion: Intra-renal expression of podocyte-associated molecules correlated with glomerular podocyte number, renal function, and tubulointerstitial scarring. The results suggest that intra-renal, but not urinary expression of podocyte-associated molecules, might be used to assess the degree of podocyte loss in diabetic nephropathy.     

Thiazolidinedione attenuate proteinuria and glomerulosclerosis in Adriamycin-induced nephropathy rats via slit diaphragm protection

Aim:   The slit diaphragm (SD) of podocyte impairment contributes to massive proteinuria and progressive glomerulosclerosis in many human glomerular diseases. The aim of the study was to determine if thiazolidinedione (TZD) reduce proteinuria and glomerulosclerosis in focal segmental glomerulosclerosis (FSGS) by preserving the structure and function of SD.
Methods:   Adriamycin-induced FSGS rat models were employed. Urinary protein content was measured dynamically during the experiment. Additional biochemical parameters in serum samples were measured after the animals were killed. Glomerular sclerosis index (SI) and podocyte foot processes fusion rate (PFR) were evaluated. The protein and mRNA expressing levels of nephrin, podocin and CD2-associated protein (CD2AP) in glomeruli were assessed by immunohistochemistry and real-time quantitative polymerase chain reaction, respectively. The density of podocytes was also evaluated after anti-Wilms' tumour-1 immunohistochemical staining.
Results:   Rosiglitazone treatment partially reduced proteinuria, but did not significantly affect the serum levels of triglyceride, cholesterol, albumin, glucose, urea nitrogen and creatinine in Adriamycin-induced FSGS rats. Glomerular SI and podocyte foot PFR were significantly attenuated by rosiglitazone treatment. Rosiglitazone prevented the reduction of nephrin, podocin and CD2AP protein expression induced by Adriamycin, however, the mRNA expression levels of these SD-related markers did not change significantly. Rosiglitazone therapy did not reverse Adriamycin-mediated reduction of the density of podocytes.
Conclusions:   The study data suggest that TZD are promising therapeutic agents on FSGS, and the mechanism may be mediated in part by directly protecting the structure and function of SD.     

APOL1 localization in normal kidney and nondiabetic kidney disease

In patients of African ancestry, genetic variants in APOL1, which encodes apolipoprotein L1, associate with the nondiabetic kidney diseases, focal segmental glomerulosclerosis (FSGS), HIV-associated nephropathy (HIVAN), and hypertensive nephropathy. Understanding the renal localization of APOL1 may provide clues that will ultimately help elucidate the mechanisms by which APOL1 variants promote nephropathy. Here, we used immunohistology to examine APOL1 localization in normal human kidney sections and in biopsies demonstrating either FSGS (n = 8) or HIVAN (n = 2). Within normal glomeruli, APOL1 only localized to podocytes. Compared with normal glomeruli, fewer cells stained for APOL1 in FSGS and HIVAN glomeruli, even when expression of the podocyte markers GLEPP1 and synaptopodin appeared normal. APOL1 localized to proximal tubular epithelia in normal kidneys, FSGS, and HIVAN. We detected APOL1 in the arteriolar endothelium of normal and diseased kidney sections. Unexpectedly, in both FSGS and HIVAN but not normal kidneys, the media of medium artery and arterioles contained a subset of α-smooth muscle actin-positive cells that stained for APOL1. Comparing the renal distribution of APOL1 in nondiabetic kidney disease to normal kidney suggests that a previously unrecognized arteriopathy may contribute to disease pathogenesis in patients of African ancestry.     

Angiotensin II type 1 receptor blockade inhibits the development and progression of HIV-associated nephropathy in a mouse model

HIV-associated nephropathy (HIVAN) is characterized by a collapsed glomerular capillary tuft with hyperplasia and hypertrophy of podocytes. Recently generated were conditional transgenic mice (podocin/Vpr) that express one of the HIV-1 accessory genes, vpr, selectively in podocytes using podocin promoter and Tet-on system. These transgenic mice developed renal injury similar to HIVAN when treated with doxycycline for 8 to 12 wk. This study demonstrated that nephron reduction by heminephrectomy markedly enhanced phenotypic changes of podocytes and led to severe FSGS within 4 wk. Nephrotic-range proteinuria was observed already at 2 wk, together with dedifferentiation and dysregulation of podocytes, indicated by decreased expression of nephrin, synaptopodin, and Wilms' tumor 1 protein and increased expression of Ki-67. The acceleration of phenotypic changes of podocytes, proteinuria, and subsequent glomerulosclerosis by heminephrectomy was almost completely inhibited by angiotensin II type 1 receptor (AT1R) blocker olmesartan. In contrast, the renoprotective effect of the calcium channel antagonist azelnidipine was minimal, although it lowered systemic BP to the same level as olmesartan, demonstrating that the inhibitory effect of AT1R blocker was independent of systemic BP. Olmesartan also reduced proteinuria and prevented glomerulosclerosis even by the delayed treatment, which was initiated after the podocyte injury appeared. These data suggest that nephron reduction exaggerates podocyte injury and subsequent glomerulosclerosis, possibly through glomerular hypertension, in the mouse model of HIVAN. AT1R blockade could be beneficial in the treatment of HIVAN by ameliorating podocyte injury by avoiding the vicious cycle of nephron reduction and glomerular hypertension.     

原发性局灶节段性肾小球硬化患者CD2AP基因突变的研究

目的了解原发性局灶节段性肾小球硬化（FSGS）患者CD2AP基因突变特点。方法研究对象为2001年至2004年我院收治的82例病理确诊为FSGS患者，年龄12-76岁，男性43例，女性39例，临床诊断为肾病综合征（NS）者55例，非NS27例；60例健康正常人为对照组。外周血基因组DNAPCR扩增后直接测序。冰冻切片免疫荧光双染色，激光共聚焦显微镜采集图像检测突变患者肾组织中CD2AP和podocin蛋白的表达。结果（1）发现2个CD2AP外显子突变，1个为2号外显子160G〉A杂合突变，造成第54位氨基酸由缬氨酸变为异亮氨酸（V54I），该患者为非NS患者，已出现肾功能不全。另1个为4号外显子358A〉G杂合突变，造成第120位氨基酸由异亮氨酸变为缬氨酸（1120V），该患者为NS患者，曾复发2次，目前肾功能尚正常。正常对照120条染色体中未发现同样突变。查阅文献和基因库，未发现相同突变报道。（2）CD2AP外显子突变患者肾小球内CD2AP表达明显减低，同时伴有podocin表达的降低。（3）发现1个启动子区突变、2个内含子突变和8个SNP位点，其中一个单核苷酸多态性（SNP）位点以往未见报道。结论CD2AP突变可能是原发性FSGS的致病原因之一。CD2AP外显子突变可导致CD2AP蛋白表达减少，并影响podocin的表达。     

两种不同病理类型肾病患者尿蛋白诱导肾小管上皮细胞上调表达趋化因子及其分子信号机制研究

目的 观察不同病理类型肾病患者尿蛋白对人近端肾小管上皮细胞（HK-2）分泌趋化因子的影响并探讨其分子信号机制。 方法 所有患者均经临床和肾穿刺活检确诊为原发性局灶节段性肾小球硬化（FSGS）或微小病变性肾病（MCD）。以超滤法浓缩提取患者尿中总蛋白，分别刺激体外培养的HK-2细胞。RT-PCR检测调节正常T细胞表达和分泌的细胞因子（RANTES）及巨噬细胞移动抑制因子（MIF）的mRNA水平。免疫荧光、ELISA及流式细胞仪检测蛋白水平的表达。Western 印迹法检测p38 MAPK和胞外信号调节激酶（ERK）水平。特异性抑制剂SB203580抑制p38磷酸化；PD98059则用于抑制ERK磷酸化。 结果 两种尿蛋白成分有差异，FSGS患者尿蛋白中含有更多的大分子量蛋白。两种尿蛋白均刺激HK-2细胞RANTES及MIF表达上调，而FSGS患者尿蛋白刺激作用更强。两种尿蛋白均显著激活HK-2细胞内ERK和p38 MAPK信号通路。特异性抑制剂分别抑制ERK或p38 MAPK的活化后，FSGS患者尿蛋白介导的RANTES和MIF的上调表达作用可被SB203580或PD98059抑制，而MCD患者尿蛋白的刺激作用却仅能被SB203580所阻断。 结论 FSGS肾病患者的尿蛋白比MCD患者的尿蛋白有更强的上调HK-2细胞RANTES及MIF表达的作用。两种尿蛋白介导趋化因子上调表达的分子信号机制存在差异。     

Ultrastructural Features and Expression of Cytoskeleton Proteins of Podocyte from Patients with Minimal Change Disease and Focal Segmental Glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) have been suggested for the category of podocytopathies. An ultrastructural observation and immunogold labeling for cytoskeleton proteins of podocytes on 11 cases each of FSGS and MCD were performed. Compared to MCD, more severe ultrastructural alterations of podocyte were identified in FSGS, which were characterized by higher frequency of mat-like condensation of microfilaments in the foot process and the detachment of the foot process from glomerular basement membrane. The labeling of α-actinin of podocytes in FSGS was significantly higher than MCD, which suggested an abnormal expression of cytoskeleton protein of podocyte in FSGS. The present study demonstrated a much more severe podocyte injury at the ultrastructural level in FSGS than in MCD.     

Ultrastructural features and expression of cytoskeleton proteins of podocyte from patients with minimal change disease and focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD) have been suggested for the category of podocytopathies. An ultrastructural observation and immunogold labeling for cytoskeleton proteins of podocytes on 11 cases each of FSGS and MCD were performed. Compared to MCD, more severe ultrastructural alterations of podocyte were identified in FSGS, which were characterized by higher frequency of mat-like condensation of microfilaments in the foot process and the detachment of the foot process from glomerular basement membrane. The labeling of alpha-actinin of podocytes in FSGS was significantly higher than MCD, which suggested an abnormal expression of cytoskeleton protein of podocyte in FSGS. The present study demonstrated a much more severe podocyte injury at the ultrastructural level in FSGS than in MCD.     

Is mesangial hypercellularity with glomerular immaturity a variant of glomerulosclerosis?

Our aim was to correlate an immunohistochemical pattern of selected podocyte cytoskeleton-associated proteins in children diagnosed with focal segmental glomerulosclerosis (FSGS) and diffuse mesangial proliferation accompanied by glomerular immaturity (Im-DMP) with the clinical courses of both diseases. The material included 33 renal biopsies obtained from children diagnosed with DMP with or without signs of glomerular immaturity (ten and 15 participants, respectively) or FSGS (eight patients). Ezrin, podocalyxin, synaptopodin and nephrin expression was evaluated by immunohistochemical assay. A positive reaction for ezrin, podocalyxin, synaptopodin and nephrin was observed in the most superficial, continuous 'layer' of podocytes in Im-DMP patients. This distribution closely mimicked the immunohistochemical pattern observed in FSGS. The severe initial course of Im-DMP was transient. Resistance to steroids (six children) and renal insufficiency (two patients) in these subjects subsided, whilst, in the FSGS patients, the resistance to steroids recognized in all the children and the renal insufficiency diagnosed in three of them were still present. Mimicry between the immunohistochemical pattern of glomerular immaturity in DMP and focal segmental glomerulosclerosis might explain the severe initial course of this nephrotic syndrome in children. The transient clinical character of the former may also indicate that it is not a variant of FSGS.