Development of hyperthyroidism in a patient with idiopathic nephrotic syndrome

We present a 13-year-old boy who developed hyperthyroidism during the clinical course of idiopathic nephrotic syndrome treated with glucocorticoid. He had a second relapse of minimal change nephrotic syndrome, and complete remission of nephrotic syndrome was achieved immediately with oral glucocorticoid. However, when the steroid dosage was reduced, signs of hyperthyroidism such as systolic hypertension and tachycardia were observed. Laboratory findings revealed thyroid-stimulating hormone (TSH) below 0.05 μU/ml, free tri-iodothyronine of 16.1 pg/ml, free thyroxine of 5.6 ng/dl, and anti-TSH receptor antibody of 90%. Thus, a diagnosis of hyperthyroidism was made and treatment with thiamazol was started. Massive proteinuria may decrease the activity of hyperthyroidism due to urinary loss of thyroid hormones. A decrease in glucocorticoid dosage may also be involved in the development of hyperthyroidism due to a reduced immunosuppressive effect. Received: 11 July 2001 / Revised: 22 October 2001 / Accepted: 27 November 2001     

Thin basement membrane nephropathy associated with minimal change disease in a 15-year-old boy

Thin basement membrane nephropathy (TBMN) is characterized clinically by persistent hematuria, minimal proteinuria, normal renal function, another family member with hematuria, and a benign course. Especially in childhood TBMN, proteinuria of any degree is reported to be uncommon. We report on a boy with benign familial hematuria found by urinary screening at 3 years of age who presented with nephrotic syndrome (NS) at 15 years of age. His renal histology showed TBMN associated with minimal change disease (MCD). Treatment with corticosteroid resulted in complete remission of NS in a short period of time, while isolated hematuria persisted during the follow-up period despite this therapy. We speculate, therefore, that the nephrotic range proteinuria is not due to TBMN but rather is the manifestation of associated MCD. Several cases of TBMN with NS have been reported in adults, but it has not yet been reported in children in the literature. To our knowledge, this is the first case of childhood TBMN associated with NS resulting from coincidental MCD.     

Long-term results of two unconventional agents in steroid-dependent nephrotic children

Children with steroid-dependent minimal change nephrotic syndrome are prone to serious steroid side effects. Alternative therapies, such as oral cyclophosphamide, may also have serious side effects. We conducted this novel prospective study to compare the long-term efficacies of levamisole and I.V. pulse cyclophosphamide as therapies with potentially fewer side effects. This study included 40 children with idiopathic steroid-dependent minimal change nephrotic syndrome (age 3–15 years; 31 boys and 9 girls). The patients were randomized into two equal groups. One group received levamisole 2.5 mg/kg on alternate days (levamisole group) while the other group received I.V. cyclophosphamide 500 mg/m²/month for six months (cyclophosphamide group). Prednisolone was gradually withdrawn. After stopping treatment, the number of patients that maintained remission was five (25%) in each group at six months, four (20%) versus two (10%) at one year and three (15%) versus one (5%) at two years in the levamisole and cyclophosphamide groups respectively, and one (5%) in each group at three and four years. The overall side effects were mild and both drugs were well tolerated. In view of the results, we recommend trial of levamisole before adopting other therapies with more serious side effects in such patients.     

巢蛋白在足突广泛融合的肾小球中表达下调及与蛋白尿程度的相关性

目的 观察中间丝蛋白类的巢蛋白（nestin）在足突广泛融合的肾小球中的表达及其与足突病变动态过程和蛋白尿产生的关系。 方法 免疫组化法检测nestin在人正常肾组织及微小病变肾组织中的表达。构建氨基核苷嘌呤霉素肾病大鼠模型，应用免疫组化、荧光实时定量PCR、Western印迹法检测注射嘌呤霉素后第1、4、10、20天大鼠肾小球中nestin的分布与表达；电镜观察肾脏足细胞改变，测定尿蛋白量（24 h）。分析nestin的变化与蛋白尿的相关性。 结果 免疫组化显示nestin在人类微小病变肾小球中的表达较正常组织显著下调（0.93±0.08 比 1.65±0.12，P < 0.05）。在嘌呤霉素损伤足细胞早期，肾小球nestin的表达曾有一过性增加（mRNA和蛋白水平分别为对照组的1.23倍和1.48倍，P < 0.05），随后持续下降。nestin的mRNA水平在嘌呤霉素注射后第4天时降至对照组的35.8%；第10天时为对照组的12.1%（均P < 0.01）；病变好转后开始上升，恢复为对照组的65.8%（P < 0.05）。Western印迹检测nestin蛋白改变也有类似的趋势，嘌呤霉素注射后第4 天，nestin蛋白水平有所下降，为对照组的77.0%（P < 0.05）；至大量蛋白尿的第10天，nestin蛋白水平仅为对照组的58.0%（P < 0.05）；而随着病变的恢复，嘌呤霉素注射后第20天时nestin蛋白量恢复为对照的83.4%。Pearson相关分析结果显示，注射嘌呤霉素后nestin mRNA（r = －0.667，P < 0.05）及蛋白（r = －0.621，P < 0.05）表达与尿蛋白量(24 h)均呈负相关。 结论 在以足突广泛融合为特征的肾脏病变中，肾小球中间丝蛋白nestin表达显著减少，并与蛋白尿程度呈负相关，提示nestin可能参与了足细胞形态和功能的维持。     

Expression of nephrin in acquired forms of nephrotic syndrome in childhood

Nephrin is a podocyte adhesion molecule located at the slit diaphragm between adjacent glomerular epithelial cells. Mutations in the gene encoding nephrin result in the absence of nephrin or alterations in nephrin causing massive proteinuria in patients with congenital nephrotic syndrome. Given the importance of nephrin to the structural integrity of the glomerular filtration barrier, we postulated that it might also be altered in acquired forms of nephrotic syndrome (NS). To test this hypothesis, frozen kidney biopsy sections from 29 pediatric patients with acquired NS and 5 controls were examined for expression of nephrin. The pathological diagnoses were minimal change disease (MCNS) (19) and focal segmental glomerulosclerosis (FSGS) (10). To determine if nephrin expression differed between children and adults with NS, 10 adult patients and 3 controls were also examined. Nephrin expression was evaluated by immunoperoxidase staining with a monoclonal antibody against the extracellular FnIII portion of human nephrin. In all cases, nephrin expression was seen along the glomerular basement membrane in a finely granular/linear pattern. Expression of nephrin was similar to controls in all 19 patients with MCNS and all 10 patients with FSGS. Areas of sclerosis in patients with FSGS did not demonstrate nephrin expression. A distinctly granular pattern to nephrin expression was seen in adult patients with NS as well as controls. These findings suggest that an alteration in nephrin expression is not a feature of acquired forms of NS in childhood.     

Diagnostic value of urinary retinol-binding protein in childhood nephrotic syndrome

Urinary excretion of N-acetyl-β-d-glucosaminidase (NAG) and retinol-binding protein (RBP), sensitive markers of renal tubular damage and dysfunction respectively, were evaluated in paired remission and relapse urine samples from 16 patients (median age 12 years), with minimal change nephrotic syndrome (MCNS), in single samples from 5 nephrotic patients (median age 12 years) with focal segmental glomerulosclerosis (FSGS) and in 183 normal controls aged 2–16 years. The NAG and RBP data were expressed as a ratio over urinary creatinine (Cr). The NAG/Cr and RBP/Cr geometric means (ranges) for normal subjects were 11.1 (3.4–35.5) μmol 2-methoxy-4-(2"-nitrovinyl)-phenol (MNP)/h per mmol and 3.1 (0.3–38.8) μg/mmol, respectively. The NAG/Cr data revealed a weak negative correlation with age in normal children, whereas RBP/Cr was independent of age. RBP/Cr and NAG/Cr in MCNS in remission were the same as in controls. In MCNS in relapse, NAG/Cr was significantly elevated (P=<0.001), while in FSGS both RBP/Cr and NAG/Cr were significantly raised (P=<0.001 and P<0.008, respectively). These findings suggest that elevated NAG/Cr may be an indicator of relapse in both MCNS and FSGS and elevated RBP/Cr may allow differentiation between the two. Received May 7, 1997; received in revised form January 30, 1998; accepted February 4, 1998     

Charge and size selectivity of proteinuria in children with idiopathic nephrotic syndrome

 Experimental studies have pointed to charge selectivity as an important determinant of glomerular permeability to macromolecules. Loss of glomerular basement membrane (GBM) polyanion has been proposed as a cause of the selective proteinuria in minimal change nephrotic syndrome (MCNS). However, the presence of less-anionic albumin in urine than plasma from MCNS and focal and segmental glomerulosclerosis (FSGS) patients has been interpreted both as evidence for partial maintenance of charge selectivity and for involvement of other pathogenic mechanisms. The exact role of charge selectivity in the pathogenesis of nephrotic proteinuria remains controversial. We have examined the clearance of endogenous proteins of differing size and charge in children with idiopathic nephrotic syndrome (NS). Chromatofocusing was used to determine the isoelectric points (pIs) of albumins in paired plasma and urine samples from patients with FSGS (n = 6) and MCNS (n = 6). Charge selectivity was assessed by comparing the pIs of the fractions with the highest albumin concentration (modal pI) in plasma and urine. The difference between the modal pIs was defined as the delta modal pI. Charge selectivity was also assessed from the albumin/transferrin and IgG4/IgG1 clearance ratios; size selectivity from the IgG1/albumin and IgG1/transferrin as well as the IgG4/albumin and IgG4/transferrin clearances. In children with FSGS, the mean (± SD) delta modal pI was  – 0.05 ± 0.16, and in MCNS  – 0.05 ± 0.11. Neither value differed significantly from zero. The albumin/transferrin clearance ratio showed no significant difference between FSGS and MCNS, but the IgG4/IgG1 clearance ratio was significantly higher in MCNS (P<0.05). Size selectivity was significantly reduced in FSGS compared with MCNS (for IgG1/transferrin P<0.01 and for IgG1/albumin P<0.05). For IgG4/transferrin and IgG4/albumin, P was <0.05. In conclusion, there was no evidence for residual charge selectivity in idiopathic NS associated with either MCNS or FSGS during nephrotic-range proteinuria. There was a significant loss of GBM size selectivity in children with FSGS with heavy proteinuria compared with children with MCNS with heavy proteinuria. Received August 7, 1996; received in revised form and accepted December 16, 1996     

Use of tacrolimus in steroid- and cyclophosphamide-resistant minimal change nephrotic syndrome

The authors report a case of adult-onset minimal change nephrotic syndrome (MCNS) that was resistant to steroid and cyclophosphamide therapy. Introduction of cyclosporin induced an usual cutaneous reaction of severe flushing attacks. Tacrolimus successfully alleviated both the nephrotic syndrome and the cutaneous side effect associated with cyclosporin use. The antiproteinuric mechanisms of tacrolimus and its potential in treating refractory MCNS and other forms of primary glomerulonephritides are discussed.     

Efficacy of intravenous pulse cyclophosphamide treatment versus combination of intravenous dexamethasone and oral cyclophosphamide treatment in steroid-resistant nephrotic syndrome

We compared, in a randomized controlled trial, the efficacy of a regimen based on intravenous (i.v.) cyclophosphamide therapy with a combination of i.v. dexamethasone and oral cyclophosphamide therapy in inducing remission in patients with steroid-resistant nephrotic syndrome (SRNS). During April 2001 to December 2003, 52 consecutive patients with idiopathic SRNS, normal renal function and renal histology findings showing minimal change disease, focal segmental glomerulosclerosis or mesangioproliferative glomerulonephritis were enrolled into the study. Patients in group I received i.v. injection of cyclophosphamide once a month for 6 months and prednisolone on alternate days. Those in group II received i.v. treatment with dexamethasone (initially on alternate days, later fortnightly and monthly; total 14 doses), oral cyclophosphamide therapy (for 3 months) and prednisolone on alternate days. Data from 49 patients (26 in group I, 23 in group II) were analyzed; their clinical and biochemical features were similar at inclusion. Following treatment, complete remission was seen in 53.8% and 47.8% patients in groups I and II, respectively (P = 0.6). Long-term follow up showed favorable outcome in 14 (53.8%) patients in group I, and 9 (39.1%) in group II. Chief adverse effects, including cushingoid features and serious infections, were similar in both groups. Patients receiving i.v. dexamethasone therapy commonly showed hypertension and hypokalemia, while vomiting and reversible alopecia occurred in those receiving i.v. treatment with cyclophosphamide. In patients with SRNS, the efficacy of treatment intravenously with cyclophosphamide and orally with prednisolone was similar to the combination of dexamethasone intravenously, orally administered cyclophosphamide and prednisolone.     

阿霉素肾病大鼠肾组织中血管形成素样蛋白3表达与蛋白尿及高脂血症的关系

目的 动态观察血管形成素样蛋白3(angiopoietin-like protein 3,ANGPTL3)在阿 霉素大鼠肾病模型肾组织中表达水平的时相变化及细胞定位情况,探讨其与微小病变型肾病综 合征蛋白尿及高脂血症之间的关系。方法 给予大鼠一次性尾静脉注射阿霉素建立微小病变型 肾病综合征大鼠模型。采用免疫组织化学染色和斑点-ELISA,检测阿霉素注射后第7天、第14 天、第21天和第28天大鼠肾组织ANGFTL3的表达及分布。分析其与24 h尿蛋白量及血清胆 同醇(Cho)和甘油三酯(TG)的关系。结果(1)阿霉素注射后第14天开始出现大量蛋白尿(P<0.01), 血清白蛋白明显减少(P<0.01),Cho(P<0.01)和TG(P<0.05)明显增高,以上各项指标均在 第28天达高峰。(2)免疫组化定量分析显示阿霉素注射后第14天时,肾小球中ANGPTL3免疫 组化指数增高至同一时间点对照组的1.42倍(P<0.05);第21天时,为同一时间点对照组的 2.48倍(P<0.01),在肾小管中的表达也明显增高,免疫组化指数为同一时间点对照组的2.04 倍(P<0.01);到第28天,其在肾小球和肾小管中的表达均达最高水平,肾小球的免疫组化指 数为同一时间点对照组的3.28倍(P<0.01),肾小管的免疫组化指数为同一时间点对照组的 2.5倍(P<0.01)。(3)ANGPTL3在肾小球中的表达部位主要位于足细胞胞浆,此外,也可见于     

成人微小病变肾病综合征发生急性肾损伤的相关影响因素分析

目的探讨成人微小病变肾病综合征发生急性肾损伤( AKI)的相关影响因素。 方法回顾性分析2002年1月1日至2015年12月31日在解放军总医院病理诊断为微小病变肾病,临床表现为首发肾病综合征的成年患者。记录其横断面临床及病理指标,并将其分为AKI组及非AKI组进行比较。用单因素及多元Logistic回归分析与AKI发生相关的影响因素。并对AKI相关的各影响因素进行交互作用检验。 结果共纳入403例患者,男女比例为1∶1.13,肾活检时平均年龄为(39.5 ± 15.1)岁,其中118(29.3%)例发生了AKI。AKI组与非AKI组相比,年龄、性别、尿蛋白定量、血清白蛋白、血肌酐、血尿素氮、估算的肾小球率过滤、肾小管萎缩、肾间质病变差异均有统计学意义(P<0.05)。单因素Logistic回归分析显示高龄、男性、尿蛋白定量多、肾小管萎缩、肾间质水肿、间质纤维化及炎细胞浸润、高血压是成人微小病变肾病发生AKI的危险因素。交互作用检验表明血清白蛋白对AKI的作用受到肾间质纤维化的显著影响(P＝0.0 050),且在调整年龄分组、性别、高血压、尿蛋白定量、肾小管萎缩、肾间质水肿、肾间质炎细胞浸润混杂因素后,其交互作用仍显著(P＝0.0 263)。从多元Logistic回归分析可见,在无肾间质纤维化的人群中,血清白蛋白水平的升高是AKI的独立保护因素(调整后的OR 0.8,95%CI 0.7～ 0.9,P<0.001)。在有肾间质纤维化人群中,血清白蛋白的升高对AKI肾脏的保护作用不显著(调整后的OR 1.0,95%CI 0.9～1.0,P＝0.0 278)。 结论高龄、男性、尿蛋白定量多、肾小管萎缩、肾间质水肿、间质纤维化及炎细胞浸润、高血压是成人微小病变肾病综合征发生AKI的危险因素。血清白蛋白升高对AKI的保护作用受到肾间质纤维化的影响。     

Validity of random urines to quantitate proteinuria in children with human immunodeficiency virus nephropathy

Accurate assessment of proteinuria in pediatric patients infected with the human immunodeficiency virus (HIV) is limited by constraints imposed by timed urine collections and low creatinine excretion in very ill patients with low muscle mass. We therefore sought to validate the use of random urine specimens to quantitate total protein and creatinine excretion in a population of 236 HIV-positive children. A mathematical derivation for estimating urine volume (V) was constructed. The accuracy of the final calculation [V=832 (kL/Ucr)BSA] (where k=constant, L body length, UCr urine creatinine and BSA body surface area) was tested by regression analysis comparing the calculated and measured volume of 31 urines from ambulatory HIV-negative patients. The correlation coefficient was highly significant (r=0.77, P≤0.0001). The relationship was also applied to 23 timed urine specimens from HIV-positive patients with similar significance (r=0.87, P<0.0001). A regression analysis of measured proteinuria against the urine protein: creatinine ratio (U_pr/U_Cr) in these same urines from the HIV-positive patients yielded a significant relationship both in the linear (r=0.95, y=0.4x) and the logarithmic regression (r=0.97, y=x+0.4). These data support the use of random U_pr/U_Cr ratios to estimate daily proteinuria in HIV-infected pediatric patients despite low creatinine excretion rates. The previously accepted values continue to apply, with U_pr/U_Cr≤2.0 considered normal and >2.0 representative of nephrotic proteinuria. Received November 3, 1994; received in revised form and accepted January 24, 1996     

Genetic effect of the NPHS2 gene variants on proteinuria in minimal change disease and immunoglobulin A nephropathy

Background: Proteinuria varies in different glomerular diseases and even the same one. Podocin, encoded by gene NPHS2, is important in maintaining the integrity of slit diaphragm structure and avoiding proteinuria. Presently, case–control association studies were performed to investigate the genetic effect of variants in NPHS2 in a mass proteinuric glomerulopathy, minimal change disease (MCD) at first, followed by further investigation in immunoglobulin A nephropathy (IgAN). Methods: At first, 214 northern Chinese patients with MCD and 493 geographically‐matched healthy controls were enrolled. Variants of the NPHS2 were screened. SNP‐2 (rs3829795:C>T, c.‐670C>T) and SNP‐5 (rs3738423:C>T, c.288C>T) were selected as tagging single nucleotide polymorphisms (SNP) and haplotypes were reconstructed. Association was analyzed in MCD patients. Then, the identified SNP site was analyzed in IgAN patients with mild histological changes (Haas subclass I and II). Results: The C allele and CC genotype frequencies at the SNP‐2 site, as well as the frequency of haplotype CC, were significantly lower in MCD patients than in healthy controls. Furthermore, they were also associated with the degree of proteinuria in MCD patients. But in IgAN patients, no such association was identified. Conclusion: The study suggested the polymorphism and haplotype of NPHS2 gene were associated with the genetic susceptibility and also the degree of proteinuria to MCD. Proteinuria in MCD and IgAN might occur through different mechanisms.     

Acute renal failure at the onset of idiopathic nephrotic syndrome in two children

Two children with idiopathic nephrotic syndrome (INS) developed acute renal failure (ARF) at the onset of the disease. Although the initial renal biopsy showed minimal change (MC) lesions with prominent interstitial edema, repeat renal biopsy revealed focal segmental glomerulosclerosis (FSGS). ARF has been reported to be a relatively rare complication in childhood INS. However, the initial manifestation of ARF may increase the risk for subsequent progression to FSGS in a proportion of children with INS with MC lesions. Received: April 3, 2000 / Accepted: October 31, 2000     

Sodium dodecyl sulphate polyacrylamide gel electrophoresis of urinary proteins in steroid-responsive and steroid-resistant nephrotic syndrome in children

Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE) of urinary proteins was performed in 56 children with nephrotic syndrome during relapse, of whom 31 had their urines tested within 2 months of the onset of disease. The urines of all 32 steroid-sensitive [presumed minimal change nephrotic syndrome (MCNS)] patients revealed albumin and transferrin bands only; whereas 19 steroid-resistant children with focal glomerular sclerosis showed additional excretion of IgG and low molecular weight proteins (lysozyme, ₂). This mixed pattern of proteinuria was also detected in 5 other steroid-resistant patients, 3 of whom were Africans with MCNS on biopsy and 2 who were Indians and not biopsied. Findings in patients studied within 2 months of presentation were identical to those investigated later in the course of the disease. SDS PAGE analysis of urine, which appears to distinguish steroid-responsive from steroid-resistant patients, may provide a valuable adjunct to the management of childhood nephrotic syndrome.     

T-cell subsets,interleukin-2 receptor expression and production of interleukin-2 in minimal change nephrotic syndrome

This study was designed to investigate T-lymphocyte subsets interleukin-2 receptor (IL-2R) expression and IL-2 production in minimal change nephrotic syndrome (MCNS). Peripheral blood T-lymphocytes and IL-2R expression were analysed using fluorescein isothiocyanatelabelled CD3, CD4, CD8 and CD25 monoclonal antibodies with flow cytometry. IL-2 production was determined by enzyme immunoassay. Ten children with MCNS in relapse and in remission were evaluated. Thirteen healthy children served as controls. The patients in relapse demonstrated a moderate decrease in the total absolute lymphocyte counts and CD8(+) T-lymphocytes compared with controls (P<0.05) and had a greatly increased IL-2R expression in frashly isolated, unstimulated peripheral lymphocytes compared with patients in remission and controls. While this was not statistically significant, IL-2R expression on cultured lymphocytes stimulated with phytohaemagglutinin was significantly elevated in relapse compared with those in remission and controls (P<0.05). IL-2 production did not correlate well with IL-2R expression and there was no significant difference between the groups. Our results suggest that T-cell subset changes and high IL-2R expression on peripheral lymphocytes may indicate the presence of stimulated T-cell populations in MCNS which could contribute to the immunopathogenesis.     

Do circulating factors play a role in the pathogenesis of minimal change nephrotic syndrome?

This review examines the studies which have been undertaken to test the hypothesis that minimal change nephrotic syndrome of childhood (MCNS) is a primary immune disorder and that there is altered T-cell function which results in release of a circulating factor. This factor alters glomerular permeability, perhaps by modifying charge sites in the glomerular capillary bed, and results in selective proteinuria. The abnormalities in immune function observed in MCNS are summarized, as are the studies of circulating factors which have been identified. Although some agents have been shown to alter capillary permeability, the unequivocal demonstration of such a factor causing selective proteinuria in vivo, either directly or indirectly, is lacking. The question is raised whether intrarenal release or activation of mediators of altered permeability, rather than the systemic release of such factors, may be important in the pathogenesis of MCNS.     

Angiotensin converting enzyme gene polymorphisms do not predict the course of idiopathic nephrotic syndrome in Swiss children

AIM: Contradictory reports exist about a correlation of angiotensin I converting enzyme (ACE) gene polymorphisms to the outcome of idiopathic nephrotic syndrome (INS) in children. We investigated the frequency of ACE polymorphisms and their impact on the clinical course of INS in children in a Swiss hospital. METHODS: The ACE gene polymorphism (I, insertion; D, deletion) was assessed in 32 children - 22 with steroid-sensitive INS and 10 with steroid-resistant INS - with a median age at onset of INS of 2.9 years (range 1.1-15.0). Polymerase chain reaction amplification was performed on genomic DNA isolated from blood leucocytes. Results were correlated to clinical course and renal morphology. RESULTS: The ACE genotype was I/I, I/D and D/D in two, 12 and eight patients, respectively, with steroid-sensitive INS, and in one, eight and one patient, respectively, with steroid resistance. Renal morphology, available in 25 patients showed minimal change glomerulopathy in 17 patients (14 steroid-sensitive; three steroid-resistant) and focal segmental glomerulosclerosis in eight (one steroid-sensitive; seven steroid-resistant). There was no significant correlation between ACE genotype and steroid responsiveness, histology or outcome. ACE genotype was I/I, I/D and D/D in none, 12 and five patients, respectively, with minimal change glomerulopathy, and in one, five and two patients, respectively, with focal segmental glomerulosclerosis. Six patients with steroid-resistant nephrotic syndrome went into end stage renal disease; ACE genotype was I/I in one and I/D in five, but none were D/D. CONCLUSION: In contrast to previous reports, ACE gene polymorphism is irrelevant for clinical outcome, steroid responsiveness or morphology in Swiss children with INS.     

Expression of alpha-actinin-4 in acquired human nephrotic syndrome: a quantitative immunoelectron microscopy study.

BACKGROUND: The molecular basis for the alteration of glomerular podocyte phenotype in nephrotic syndrome probably involves adaptive changes of the actin cytoskeleton. alpha-Actinin-4 is an actin cross-linking protein that also interacts with intra- and intercellular adhesion molecules and elements of the transmembrane signal transduction pathway and is implicated in nephrotic syndrome by animal models and human genetic studies. METHODS: We have performed the first quantitative immunoelectron microscopy study of alpha-actinin-4 expression in humans, analysing 12 cases of minimal change nephrosis (MCNS) and 16 cases of idiopathic membranous nephropathy (MGN), and comparing this with expression in normal tissue from seven nephrectomies (Nx). alpha-Actinin-4 was visualized by immunogold labelling of plastic-embedded whole glomerular cross-sections, and analysed using LUCIA software. RESULTS: Despite podocyte effacement, alpha-actinin-4 expression (group mean+/-1 SD) in MCNS was similar to that seen in normal Nx podocytes. In contrast, alpha-actinin-4 expression in MGN was significantly higher than in MCNS or Nx (P<0.001). Furthermore, in MGN cases showing a segmental deposition, expression of alpha-actinin-4 was significantly higher only in those capillary loop segments containing deposits, whereas in those segments without deposits expression was unchanged compared with that seen in Nx (P<0.001). alpha-Actinin-4 expression was higher in MGN cases where subepithelial deposits abutted podocyte cytoplasm, and lower in disease stages where deposits were contained within the glomerular basement membrane or were being reabsorbed. CONCLUSIONS: Elevated alpha-actinin-4 expression is observed only in MGN, and only in areas of subepithelial deposits. Further investigation into the cause of this may reveal insights into the pathogenesis of acquired nephrosis.