Regulatory T cells and minimal change nephropathy: in the midst of a complex network

Etiology of nephrotic syndrome: insights from univariate and multivariate Mendelian randomization study

Nephrotic syndrome (NS) is a common cause of chronic glomerular disease. However, the precise way in which one or more risk exposure traits of renal injury lead to NS remains unclear. In this study, we systematically examined the causal relationships between NS and various exposure traits, including traits related to chronic hepatitis B/C infection, COVID-19 (hospitalized), general allergy status, herbal tea intake, immunoglobulin E, childhood obesity, and the human leukocyte antigen (HLA)-II histocompatibility DM α/DP β1/DQ α2 chain, via multivariate Mendelian randomization (MVMR). A previously reported exposure trait, ulcerative colitis, was also included to analyze the independent effect of each significant exposure on the risk of developing NS. In the univariable MR analysis, immunoglobulin E (OR = 5.62, 95% CI = 2.91-10.84, p = 2.67 × 10-7) and the HLA-II histocompatibility DQ α2 chain (OR = 0.70, 95% CI = 0.63-0.80, p = 2.83 × 10-7) were shown to have effect estimates consistent with a greater risk of developing NS. The reverse MR analysis showed no evidence of causal effect from NS to histocompatibility DQ α2 chain (p = 0.76). In MVMR, only the HLA-II histocompatibility DQ α2 chain retained a robust effect (OR = 0.71, 95% CI = 0.61-0.82; p = 9.39 × 10-6), and the estimate for immunoglobulin E was weakened (OR = 1.04, 95% CI = 0.60-2.13; p = 0.92). With two independent ulcerative colitis resources used for validation, ulcerative colitis was not significantly associated with NS. This study provides genetic evidence that the HLA-II histocompatibility DQ α2 chain has a predominant causal effect on the risk of developing NS. HLA-II histocompatibility-mediated immune abnormalities may lead to subtypes of NS and its pathological changes.

Causal association of circulating immune cells with nephrotic syndrome: evidence from a two-sample Mendelian randomization study

OBJECTIVE

Nephrotic syndrome, a debilitating manifestation of kidney disease, often arises from diverse glomerular disorders and is accompanied by notable comorbidities. Despite indications of an immunological etiology, the precise role of immune cells in its pathogenesis remains unclear. This study aimed to elucidate the causal relationships between circulating immune cell phenotypes and nephrotic syndrome using a rigorous bidirectional Mendelian randomization approach.

METHODS

We conducted a bidirectional Mendelian randomization analysis leveraging public genome-wide association studies (GWAS) datasets to investigate the causal links between 731 immune cell features and nephrotic syndrome. Our primary analysis employed inverse variance weighting (IVW), complemented by MR-Egger regression, simple model, weighted median method, and weighted model techniques to ensure robustness. Sensitivity analyses were performed to address potential biases arising from heterogeneity, horizontal pleiotropy, and single-nucleotide polymorphism (SNP) instability in nephrotic syndrome.

RESULTS

Among traits examined, 13 immune cell phenotypes were identified to have significant causal impacts on nephrotic syndrome (adjusted P >  < 0.05). Among these phenotypes, CD25 on unswitched memory B cell, CD25 on memory B cell, CD25 on CD24 + CD27 + B cell, CD25 on IgD-CD38-B cell, CD33dim HLA DR-Absolute Count, and CD127 on granulocyte emerged as causal risk factors, while seven circulating immune cell phenotypes, predominantly monocyte subsets, exhibited protective effects. Furthermore, the reverse Mendelian randomization analysis demonstrated significant effects of nephrotic syndrome on 27 immune phenotypes (P < 0.05).

CONCLUSION

The genetic predictions indicate that multiple circulating immune cell phenotypes, particularly CD25 on specific B-cell subsets, serve as independent risk factors for the onset and progression of nephrotic syndrome. Conversely, monocytes expressing specific phenotypes may exert protective effects against the development of nephrotic syndrome. These findings offer a novel therapeutic approach for the prevention and treatment of nephrotic syndrome.

Amino acid variants in the HLA-DQA1 and HLA-DQB1 molecules explain the major association of variants with relapse status in pediatric patients with steroid-sensitive nephrotic syndrome

BACKGROUND

Management of patients with steroid-sensitive nephrotic syndrome (SSNS) is challenging because of frequent relapses. Causal variants in the human leukocyte antigen (HLA) class II region that are associated with relapse remain undetermined.

METHODS

We collected a cohort of East Asian individuals comprising 206 pediatric patients with SSNS and 435 healthy controls from Southwest China. Ninety children with steroid-sensitive nephrotic syndrome without relapse (SSNSWR) and 116 children with steroid-dependent and/or frequent relapse nephrotic syndrome (SDNS/FRNS) were genotyped using Sanger sequencing. We then measured the transcriptional level, allele expression imbalance (AEI) and functional proteins of HLA-DQA1 and HLA-DQB1 in different stages of SDNS/FRNS.

RESULTS

rs1464545187 in ANKRD36 was associated with an approximately 1.69-fold greater risk for SSNSWR (P = 0.04; 95% confidence interval [CI], 1.05-2.72). Clustered risk variants in HLA-DQA1 and HLA-DQB1 were significantly associated with SDNS/FRNS (rs1047989: P = 2.26E-07, odds ratio [OR] = 2.25, 1.65-3.05; rs9273471: P = 5.45E-05, OR = 1.84, 1.37-2.46; HLA-DQB1*06:02: P = 0.017, OR = 0.19, 0.04-0.77). The genotype distributions of rs1047989, 2:171713702, rs1049123, rs9273471, and HLA-DQB1*06:02 in patients with SSNS were significantly different from those in healthy controls. rs1047989 (HLA-DQA1) was significantly associated with a greater number of infections at relapse in SDNS/FRNS patients (P = 0.045, OR = 6.79, 95% CI: 1.29-168.52). Flow cytometry showed that the proportion of cells expressing HLA-DQA1+/DQB1+ (HLA-DQA1+, P = 0.0046; HLA-DQB1+, P = 0.0045) was lowest in the relapse stage. In addition, the mRNA levels of HLA-DQA1 and HLA-DQB1 were significantly greater in the relapse group than in the remission group (HLA-DQA1, P = 0.03; HLA-DQB1, P = 0.002). No significant AEIs were detected in the different stages of SDNS/FRNS. The rs1047989 variant is likely to affect the structure and stability of HLA-DQA1.

CONCLUSION

rs1464545187 is a risk locus for SSNSWR but not SDNS/FRNS in Chinese children. Functional variations in HLA-DQA1 and HLA-DQB1 are implicated in regulating the immune response of SSNS patients, which may explain the typical triggering of SDNS/FRNS onset by infections.

Sirtuin 6 protects against podocyte injury by blocking the renin-angiotensin system by inhibiting the Wnt1/β-catenin pathway

Sirtuins (Sirts) are a family of nicotinamide adenine dinucleotide-dependent protein deacetylases that share diverse cellular functions. Increasing evidence shows that Sirts play a critical role in podocyte injury, which is a major determinant of proteinuria-associated renal disease. Membranous nephropathy (MN) is a typical glomerular disease in which podocyte damage mediates proteinuria development. In this study we investigated the molecular mechanisms underlying the regulatory roles of Sirt in podocyte injury in MN patients, rats with cationic bovine serum albumin (CBSA)-induced MN and zymosan activation serum (ZAS)-stimulated podocytes. Compared with healthy controls, MN patients showed significant reduction in intrarenal Sirt1 and Sirt6 protein expression. In CBSA-induced MN rats, significant reduction in intrarenal Sirt1, Sirt3 and Sirt6 protein expression was observed. However, only significant decrease in Sirt6 protein expression was found in ZAS-stimulated podocytes. MN patients showed significantly upregulated protein expression of Wnt1 and β-catenin and renin-angiotensin system (RAS) components in glomeruli. CBSA-induced MN rats exhibited significantly upregulated protein expression of intrarenal Wnt1 and β-catenin and their downstream gene products as well as RAS components. Similar results were observed in ZAS-stimulated podocytes. In ZAS-stimulated podocytes, treatment with a specific Sirt6 activator UBCS039 preserved the protein expression of podocin, nephrin and podocalyxin, accompanied by significant inhibition of the protein expression of β-catenin and its downstream gene products, including Snail1 and Twist; treatment with a β-catenin inhibitor ICG-001 significantly preserved the expression of podocyte-specific proteins and inhibited the upregulation of downstream β-catenin gene products accompanied by significant suppression of the protein expression of RAS components. Thus, we demonstrate that Sirt6 ameliorates podocyte injury by blocking RAS signalling via the Wnt1/β-catenin pathway. Sirt6 is a specific therapeutic target for the treatment of podocyte damage-associated renal disease.

The podocyte: glomerular sentinel at the crossroads of innate and adaptive immunity

Focal segmental glomerulosclerosis (FSGS) is a common glomerular disorder that manifests clinically with the nephrotic syndrome and has a propensity to recur following kidney transplantation. The pathophysiology and therapies available to treat FSGS currently remain elusive. Since the podocyte appears to be the target of apparent circulating factor(s) that lead to recurrence of proteinuria following kidney transplantation, this article is focused on the podocyte. In the context of kidney transplantation, the performance of pre- and post-reperfusion biopsies, and the establishment of in vitro podocyte liquid biopsies/assays allow for the development of clinically relevant studies of podocyte biology. This has given insight into new pathways, involving novel targets in innate and adaptive immunity, such as SMPDL3b, cGAS-STING, and B7-1. Elegant experimental studies suggest that the successful clinical use of rituximab and abatacept, two immunomodulating agents, in our case series, may be due to direct effects on the podocyte, in addition to, or perhaps distinct from their immunosuppressive functions. Thus, tissue biomarker-directed therapy may provide a rational approach to validate the mechanism of disease and allow for the development of new therapeutics for FSGS. This report highlights recent progress in the field and emphasizes the importance of kidney transplantation and recurrent FSGS (rFSGS) as a platform for the study of primary FSGS.

Therapeutic trials in difficult to treat steroid sensitive nephrotic syndrome: challenges and future directions

Steroid sensitive nephrotic syndrome is a common condition in pediatric nephrology, and most children have excellent outcomes. Yet, 50% of children will require steroid-sparing agents due to frequently relapsing disease and may suffer consequences from steroid dependence or use of steroid-sparing agents. Several steroid-sparing therapeutic agents are available with few high quality randomized controlled trials to compare efficacy leading to reliance on observational data for clinical guidance. Reported trials focus on short-term outcomes such as time to first relapse, relapse rates up to 1-2 years of follow-up, and few have studied long-term remission. Trial designs often do not consider inter-individual variability, and differing response to treatments may occur due to heterogeneity in pathogenic mechanisms, and genetic and environmental influences. Strategies are proposed to improve the quantity and quality of trials in steroid sensitive nephrotic syndrome with integration of biomarkers, novel trial designs, and standardized outcomes, especially for long-term remission. Collaborative efforts among international trial networks will help move us toward a shared goal of finding a cure for children with nephrotic syndrome.

Microbiota and glomerulonephritis: An immunological point of view

Glomerular injury is the major cause of chronic kidney diseases (CKD) worldwide and is characterized by proteinuria. Glomerulonephritis (GN) has a wide spectrum of etiologies, the intensity of glomerular damage, histopathology, and clinical outcomes that can be associated with the landscape of the nephritogenic immune response. Beyond impaired immune responses and genetic factors, recent evidence indicates that microbiota can be contributed to the pathogenesis of GN and patients' outcomes by impacting many aspects of the innate and adaptive immune systems. It is still unknown whether dysbiosis induces GN or it is a secondary effect of the disease. Several factors such as drugs and nutritional problems can lead to dysbiosis in GN patients. It has been postulated that gut dysbiosis activates immune responses, promotes a state of systemic inflammation, and produces uremic toxins contributing to kidney tissue inflammation, apoptosis, and subsequent proteinuric nephropathy. In this review, the impact of gastrointestinal tract (GI) microbiota on the pathogenesis of the primary GN will be highlighted. The application of therapeutic interventions based on the manipulation of gut microbiota with special diets and probiotic supplementation can be effective in GN.

Minimal change disease caused by polycythemia vera: A case report

BACKGROUND

Polycythemia vera (PV), often attributed to the JAK2 V617F mutation, is characterized by enhanced red blood cell counts in the peripheral blood. PV-associated renal disease is clinically rare; to date, there have been reports of other chronic kidney diseases related to PV, but no reports on PV-associated minimal change disease.

CASE SUMMARY

A 37-year-old man presented with proteinuria and high red blood cell count on January 4, 2021. The patient underwent bone marrow and renal biopsies, then was subsequently diagnosed with PV and minimal change in disease. Hydroxyurea was administered and proteinuria remission was achieved. The patient's last visit was on April 14, 2022.

CONCLUSION

We inferred that there may be a causal relationship between PV and minimal change disease.

Prostate Cancer Associated with Minimal Change Disease: A Case Report

Introduction

Minimal change disease (MCD), a common cause of primary nephrotic syndrome that accounts for 10%-15% of all primary nephrotic syndrome cases in adults, is frequently associated with malignant lymphoma. However, studies on MCD associated with prostate cancer are scarce.

Case Presentation

A 73-year-old male with prostate cancer was referred to our department with hypoalbuminemia and severe proteinuria while waiting for prostatectomy. We diagnosed the patient with nephrotic syndrome and performed a renal biopsy. Renal pathological findings were consistent with those of MCD. The clinical course suggested an association between prostate cancer and MCD as our patient achieved complete remission of MCD after receiving androgen deprivation and radiation therapy for prostate cancer without the use of glucocorticoids or other immunosuppressants.

Discussion

Although MCD can be associated with solid tumors, MCD associated with prostate cancer is very rare. The current case is the first to directly raise the possibility that secondary MCD may develop due to prostate cancer in some patients.

Molecular Mechanisms of Proteinuria in Minimal Change Disease

Minimal change disease (MCD) is the most common type of idiopathic nephrotic syndrome in childhood and represents about 15% cases in adults. It is characterized by massive proteinuria, edema, hypoalbuminemia, and podocyte foot process effacement on electron microscopy. Clinical and experimental studies have shown an association between MCD and immune dysregulation. Given the lack of inflammatory changes or immunocomplex deposits in the kidney tissue, MCD has been traditionally thought to be mediated by an unknown circulating factor(s), probably released by T cells that directly target podocytes leading to podocyte ultrastructural changes and proteinuria. Not surprisingly, research efforts have focused on the role of T cells and podocytes in the disease process. Nevertheless, the pathogenesis of the disease remains a mystery. More recently, B cells have been postulated as an important player in the disease either by activating T cells or by releasing circulating autoantibodies against podocyte targets. There are also few reports of endothelial injury in MCD, but whether glomerular endothelial cells play a role in the disease remains unexplored. Genome-wide association studies are providing insights into the genetic susceptibility to develop the disease and found a link between MCD and certain human haplotype antigen variants. Altogether, these findings emphasize the complex interplay between the immune system, glomerular cells, and the genome, raising the possibility of distinct underlying triggers and/or mechanisms of proteinuria among patients with MCD. The heterogeneity of the disease and the lack of good animal models of MCD remain major obstacles in the understanding of MCD. In this study, we will review the most relevant candidate mediators and mechanisms of proteinuria involved in MCD and the current models of MCD-like injury.

Idiopathic Nephrotic Syndrome in Pediatrics: An Up-to-date

BACKGROUND

Idiopathic or Primary Nephrotic Syndrome (INS) is a common glomerular disease in pediatric population, characterized by proteinuria, edema and hypoalbuminemia with variable findings in renal histopathology.

OBJECTIVE

This review aims to summarize current data on the etiopathogenesis diagnosis, protocols of treatment and potential therapeutic advances in INS.

METHODS

This narrative review searched for articles on histopathology, physiopathology, genetic causes, diagnosis and treatment of INS in pediatric patients. The databases evaluated were PubMed and Scopus.

RESULTS

INS is caused by an alteration in the permeability of the glomerular filtration barrier with unknown etiology. There are several gaps in the etiopathogenesis, response to treatment and clinical course of INS that justify further investigation. Novel advances include the recent understanding of the role of podocytes in INS and the identification of genes associated with the disease. The role of immune system cells and molecules has also been investigated. The diagnosis relies on clinical findings, laboratory exams and renal histology for selected cases. The treatment is primarily based on steroids administration. In case of failure, other medications should be tried. Recent studies have also searched for novel biomarkers for diagnosis and alternative therapeutic approaches.

CONCLUSION

The therapeutic response to corticosteroids still remains the main predictive factor for the prognosis of the disease. Genetic and pharmacogenomics tools may allow the identification of cases not responsive to immunosuppressive medications.

The role of the immune system in idiopathic nephrotic syndrome

Idiopathic nephrotic syndrome (INS) in children is characterized by massive proteinuria and hypoalbuminemia and usually responds well to steroids. However, relapses are frequent, which can require multi-drug therapy with deleterious long-term side effects. In the last decades, different hypotheses on molecular mechanisms underlying INS have been proposed and several lines of evidences strongly indicate a crucial role of the immune system in the pathogenesis of non-genetic INS. INS is traditionally considered a T-cell-mediated disorder triggered by a circulating factor, which causes the impairment of the glomerular filtration barrier and subsequent proteinuria. Additionally, the imbalance between Th17/Tregs as well as Th2/Th1 has been implicated in the pathomechanism of INS. Interestingly, B-cells have gained attention, since rituximab, an anti-CD20 antibody demonstrated a good therapeutic response in the treatment of INS. Finally, recent findings indicate that even podocytes can act as antigen-presenting cells under inflammatory stimuli and play a direct role in activating cellular pathways that cause proteinuria. Even though our knowledge on the underlying mechanisms of INS is still incomplete, it became clear that instead of a traditionally implicated cell subset or one particular molecule as a causative factor for INS, a multi-step control system including soluble factors, immune cells, and podocytes is necessary to prevent the occurrence of INS. This present review aims to provide an overview of the current knowledge on this topic, since advances in our understanding of the immunopathogenesis of INS may help drive new tailored therapeutic approaches forward.

Premature birth carries a higher risk of nephrotic syndrome: a cohort study

The pathogenesis of nephrotic syndrome is unclear. We conducted a nationwide population-based cohort study to examine the associations between preterm births and subsequent development of NS. NS was defined as ≥ 3 records with ICD-9-CM codes for NS in hospital admission or outpatient clinic visits. To avoid secondary nephrotic syndrome or nephritis with nephrotic range proteinuria, especially IgA nephropathy, we excluded patients with associated codes. A total of 78,651 preterm infants (gestational age < 37 weeks) and 786,510 matched term infants born between 2004 and 2009 were enrolled and followed until 2016. In the unadjusted models, preterm births, maternal diabetes, and pregnancy induced hypertension were associated with subsequent NS. After adjustment, preterm births remained significantly associated with NS (p = 0.001). The risk of NS increased as the gestational age decreased (p for trend < 0.001). Among the NS population, preterm births were not associated with more complications (Hypertension: p = 0.19; Serious infections: p = 0.63, ESRD: p = 0.75) or a requirement for secondary immunosuppressants (p = 0.61). In conclusion, preterm births were associated with subsequent NS, where the risk increased as the gestational age decreased. Our study provides valuable information for future pathogenesis studies.

Seven novel podocyte autoantibodies were identified to diagnosis a new disease subgroup-autoimmune Podocytopathies

Children with idiopathic nephrotic syndrome (INS) usually have podocyte injury, and recent studies suggest a B cell dysfunction in INS. Therefore, this study attempts to screen and identify the podocyte autoantibodies in patients. Two-dimensional electrophoresis and mass spectrometry were used to screen and identify the pathogenic podocyte autoantibodies in children with INS. The positive rate, expression pattern, and clinical correlation of these podocyte autoantibodies in children with INS were determined by clinical study. At least 66% of INS children have podocyte autoantibodies. Seven podocyte autoantibodies closely related to INS were screened and identified for the first time in this study. These podocyte autoantibodies are positively correlated with proteinuria, and its titer will decrease rapidly after effective treatment. In this study, a group of new disease subgroup-"autoimmune podocytes" were identified by podocyte autoantibodies.

Low regulatory T-cells: A distinct immunological subgroup in minimal change nephrotic syndrome with early relapse following rituximab therapy

Rituximab is an important second line therapy in difficult nephrotic syndrome (NS), especially given toxicity of long-term glucocorticoid or calcineurin inhibitor (CNI) use. However, clinical response to rituximab is heterogenous. We hypothesized that this was underpinned by immunological differences amongst patients with NS. We recruited a cohort of 18 subjects with glucocorticoid-dependent or glucocorticoid-resistant childhood-onset minimal change NS who received rituximab either due to CNI nephrotoxicity, or due to persistent glucocorticoid toxicity with inadequate response to cyclophosphamide or CNIs. Immunological subsets, T-cell activation assays and plasma cytokines were measured at baseline and 6-months post-rituximab. Time to relapse was bifurcated: 56% relapsed within one year ("early relapse"), while the other 44% entered remission mainly lasting ≥3 years ("sustained remission"). At baseline, early relapse compared to sustained remission group had lower regulatory T-cells (Tregs) [2.94 (2.25, 3.33)% vs 6.48 (5.08, 7.24)%, P<0.001], PMA-stimulated IL-2 [0.03 (0, 1.85)% vs 4.78 (0.90, 9.18)%, P=0.014] and IFNγ [2.22 (0.18, 6.89)% vs 9.47 (2.72, 17.0)%, P=0.035] levels. Lower baseline Treg strongly predicted early relapse (ROC-AUC 0.99, 95% CI 0.97-1.00, P<0.001). There were no differences in baseline plasma cytokine levels. Following rituximab, there was significant downregulation of Th2 cytokines in sustained remission group (P=0.038). In particular, IL-13 showed a significant decrease in sustained remission group [-0.56 (-0.64, -0.35)pg/ml, P=0.007)], but not in the early relapse group. In conclusion, early relapse following rituximab is associated with baseline reductions in Treg and T-cell hyporesponsiveness, which suggest chronic T-cell activation and may be useful predictive biomarkers. Sustained remission, on the other hand, is associated with downregulation of Th2 cytokines following rituximab.

The important roles and molecular mechanisms of annexin A2 autoantibody in children with nephrotic syndrome

BACKGROUND

In recent years, B-cell dysfunction has been found to play an important role in the pathogenesis of primary nephrotic syndrome (PNS). B cells play a pathogenic role by secreting antibodies against their target antigens after transforming into plasma cells. Therefore, this study aimed to screen the autoantibodies that cause PNS and explore their pathogenic mechanisms.

METHODS

Western blotting and mass spectrometry were employed to screen and identify autoantibodies against podocytes in children with PNS. Both in vivo and in vitro experiments were used to study the pathogenic mechanism of PNS. The results were confirmed in a large multicenter clinical study in children.

RESULTS

Annexin A2 autoantibody was highly expressed in children with PNS with a pathological type of minimal change disease (MCD) or focal segmental glomerulosclerosis without genetic factors. The mouse model showed that anti-Annexin A2 antibody could induce proteinuria in vivo. Mechanistically, the effect of Annexin A2 antibody on the Rho signaling pathway was realized through promoting the phosphorylation of Annexin A2 at Tyr24 on podocytes by reducing its binding to PTP1B, which led to the cytoskeletal rearrangement and damage of podocytes, eventually causing proteinuria and PNS.

CONCLUSIONS

Annexin A2 autoantibody may be responsible for some cases of PNS with MCD/FSGS in children.

CD73 Overexpression in Podocytes: A Novel Marker of Podocyte Injury in Human Kidney Disease

The CD73 pathway is an important anti-inflammatory mechanism in various disease settings. Observations in mouse models suggested that CD73 might have a protective role in kidney damage; however, no direct evidence of its role in human kidney disease has been described to date. Here, we hypothesized that podocyte injury in human kidney diseases alters CD73 expression that may facilitate the diagnosis of podocytopathies. We assessed the expression of CD73 and one of its functionally important targets, the C-C chemokine receptor type 2 (CCR2), in podocytes from kidney biopsies of 39 patients with podocytopathy (including focal segmental glomerulosclerosis (FSGS), minimal change disease (MCD), membranous glomerulonephritis (MGN) and amyloidosis) and a control group. Podocyte CD73 expression in each of the disease groups was significantly increased in comparison to controls (p < 0.001–p < 0.0001). Moreover, there was a marked negative correlation between CD73 and CCR2 expression, as confirmed by immunohistochemistry and immunofluorescence (Pearson r = −0.5068, p = 0.0031; Pearson r = −0.4705, p = 0.0313, respectively), thus suggesting a protective role of CD73 in kidney injury. Finally, we identify CD73 as a novel potential diagnostic marker of human podocytopathies, particularly of MCD that has been notorious for the lack of pathological features recognizable by light microscopy and immunohistochemistry.

Circulating plasmablasts and high level of BAFF are hallmarks of minimal change nephrotic syndrome in adults

BACKGROUND

The recent success achieved with the use of B cell-depleting agents in some patients with minimal change nephrotic syndrome (MCNS) suggests an unexpected role for B lymphocytes in the pathogenesis of this immune-mediated glomerular disease. Nevertheless, no extensive B-cell phenotyping analysis has ever been performed in untreated adult patients soon after MCNS diagnosis.

METHODS

We investigated the distribution of the different B-cell subpopulations in 22 untreated adult patients with biopsy-proven MCNS [MCNS relapse (MCNS-Rel)]. We compared these data with those for 24 healthy controls, 13 MCNS patients in remission (with no specific treatment) and 19 patients with idiopathic membranous nephropathy (IMN).

RESULTS

Patients with MCNS-Rel or IMN had higher proteinuria and lower serum albumin and gammaglobulin levels (P < 0.0001 for all comparisons) than MCNS patients in remission. Plasmablasts were the only B-cell subsets present at significantly higher levels in MCNS-Rel patients than in the patients of the other three groups (P < 0.05 for all comparisons). The lower albumin levels and higher proteinuria levels were positively correlated with the percentage of circulating plasmablasts (Spearman test's ρ = -0.54, P = 0.01 and ρ = 0.65, P = 0.002, respectively). Similarly, the increase of immunoglobulin M (IgM) and the decrease of IgG levels were significantly associated with the percentage of plasmablasts in MCNS-Rel patients (Spearman's ρ = 0.36, P = 0.01 and Spearman's ρ = -0.60, P = 0.01, respectively). Increased production of interleukin (IL)-21, IL-6 and B-cell activating factor (BAFF) in the serum of MCNS-Rel patients was found significantly correlated with the percentage of plasmablasts (ρ = 0.72, P = 0.0002, ρ = 0.49, P = 0.04 and ρ = 0.62, P = 0.009, respectively).

CONCLUSIONS

An increase in the proportion of circulating plasmablasts seems to be a hallmark of untreated MCNS in adult patients. Further studies are required to more precisely determine the phenotype and functions of these cells.

Financial market volatility based on complex network and fuzzy logic theory

Volatility is an inherent attribute of the financial market, which is usually expressed as the degree of volatility of financial asset prices. The volatility of the financial market means that there is uncertainty or risk in the market. This paper mainly studies financial market fluctuations based on complex networks and fuzzy logic theory. This article first systematically organizes and summarizes the theoretical construction of complex networks and fuzzy logic. In terms of complex networks, the definition of complex networks, the theory of commonly used functions (classical models of complex networks) and the solving methods are sorted out. In the construction of fuzzy logic theory, starting with quantifiable financial market volatility indicators, the construction models of realized volatility and implied volatility are discussed, and complex network models of implied volatility and model-free models are discussed. The theoretical construction methods were compared and analyzed. Finally, it summarizes the theoretical construction methods of implied volatility index and points out the advantages of model-free implied volatility as a market volatility and risk measurement index, which contains more effective future risk information and is based on implied volatility. The empirical research on indexes and complex network models has laid a theoretical foundation. Experimental data shows that the bond market and the foreign exchange market have the largest fluctuations in the correlation coefficient, reaching 0.35; followed by the stock market and the bond market, which is about 0.17; the stock market and foreign exchange market with the smallest fluctuations are about 0.08. The experimental results show that the financial market volatility research data based on complex networks and fuzzy logic theory is more accurate.

Idiopathic nephrotic syndrome in children: role of regulatory T cells and gut microbiota

BACKGROUND

We investigated whether an association exists between regulatory T cells (Tregs) during initial presentation in children with idiopathic nephrotic syndrome (INS) and later development of frequently relapsing INS.

METHODS

Blood samples were obtained at onset and at remission from 25 patients (median age, 4.0 years) with INS; eight did not show relapse after initial response (non-relapsing [NR]), whereas 17 showed frequent relapses (frequently relapsing [FR]). Tregs were measured by flow cytometry; increases were compared between groups. Fecal samples were obtained at onset from 20 patients with INS, as well as from 20 age-matched healthy children. Gut microbiota composition was assessed using 16S ribosomal RNA (rRNA) sequencing (ion PGM).

RESULTS

The rate of increase in Tregs from onset to remission was significantly lower in the FR group (124.78%) than in the NR group (879.16%; P < 0.001). Additionally, 16S rRNA sequencing of gut microbiota showed that the proportion of butyric acid-producing bacteria was significantly lower in the FR group (7.08%) than in the healthy children (17.45%; P < 0.001).

CONCLUSIONS

In children with INS, small increases in Tregs in response to steroid treatment were associated with subsequent increased risk of frequent relapses. In addition, the FR group had a greater degree of dysbiosis at onset.

IMPACT

A low rate of Tregs increase is associated with subsequent frequent relapses of INS. The increase in Tregs in response to steroid treatment was small when dysbiosis was present in patients with INS, particularly when the proportion of butyrate-producing bacteria was considerably reduced We presume that improvement of dysbiosis by administration of probiotics and prebiotics may enhance the rate of Tregs' increase, thus preventing frequent relapse.

Efficacy and safety of rituximab in adult frequent-relapsing or steroid-dependent minimal change disease or focal segmental glomerulosclerosis: a systematic review and meta-analysis

Background

The efficacy and safety of rituximab (RTX) in adult frequent-relapsing (FR) or steroid-dependent (SD) nephrotic syndrome (NS), including minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS), are still inconclusive.

Methods

We performed a systematic review and meta-analysis registered in  PROSPERO (CRD42019148102) by pooling data of cohort studies or case series on adult patients with difficult-to-treat NS. Steroid-resistant NS was excluded. The primary outcomes were the complete remission (CR) rate and the relapse rate. Partial remission (PR) rate, no response (NR) rate and adverse events were the secondary outcomes. A random-effects model was performed for all the outcomes.

Results

We included 21 studies involving 382 adult MCD/FSGS subjects with a median follow-up duration from 12 to 43 months. RTX treatment induced a pooled 84.2% CR rate [95% confidence interval (CI): 67.7–96.3%], while MCD patients had a high 91.6% CR rate and FSGS patients a moderate 43% CR rate. However, 27.4% (95% CI 20.7–34.5%) of the patients relapsed during the follow-up. The pooled PR and NR rates were 5.8% (95% CI 1.2–12.5%) and 5.2% (95% CI 0.0–15.0%), respectively. RTX was associated with trivial adverse events and good tolerance.

Conclusions

In summary, by pooling results of current pilot studies, RTX may be an effective and relatively safe alternative for most adult FR or SD MCD/FSGS to displace calcineurin inhibitors or prednisone in the hierarchy of treatment. More clinical trials comparing RTX with other immunosuppressants and concerning the long-term adverse events are needed.

CD40/CD40L Signaling as a Promising Therapeutic Target for the Treatment of Renal Disease

The cluster of differentiation 40 (CD40) is activated by the CD40 ligand (CD40L) in a variety of diverse cells types and regulates important processes associated with kidney disease. The CD40/CD40L signaling cascade has been comprehensively studied for its roles in immune functions, whereas the signaling axis involved in local kidney injury has only drawn attention in recent years. Clinical studies have revealed that circulating levels of soluble CD40L (sCD40L) are associated with renal function in the setting of kidney disease. Levels of the circulating CD40 receptor (sCD40), sCD40L, and local CD40 expression are tightly related to renal injury in different types of kidney disease. Additionally, various kidney cell types have been identified as non-professional antigen-presenting cells (APCs) that express CD40 on the cell membrane, which contributes to the interactions between immune cells and local kidney cells during the development of kidney injury. Although the potential for adverse CD40 signaling in kidney cells has been reported in several studies, a summary of those studies focusing on the role of CD40 signaling in the development of kidney disease is lacking. In this review, we describe the outcomes of recent studies and summarize the potential therapeutic methods for kidney disease which target CD40.

Increased number and activation of peripheral basophils in adult-onset minimal change disease

Nowadays, the pathogenesis of minimal change disease (MCD) is still not well-known, and the current understanding on MCD is mainly based on data derived from children, and very few adults. Here, we comprehensively analysed the correlation between the changes of peripheral basophils and the incidence rate and relapse of adult-onset MCD. The results showed that in patients at the onset of MCD, the ratio and activation of basophils were all higher than those of healthy controls (all P < .05). In vitro test results showed that basophils from healthy controls can be activated by the serum taken from patients with MCD. Among 62 patients at the onset of MCD, with complete remission after treatment and 1 year of follow-up, the relative and absolute basophil counts before treatment were higher in the long-term remission group (n = 33) than that of the relapse group (n = 29). The basophil counts were significantly higher in the infrequent relapse group (n = 13) than that of the frequent relapse group (n = 16; P < .05). These findings suggested that basophil may play a pathogenic role in adult-onset MCD, and the increased number and activation of peripheral basophils could predict recurrence in adult MCD.

Common risk variants in NPHS1 and TNFSF15 are associated with childhood steroid-sensitive nephrotic syndrome

To understand the genetics of steroid-sensitive nephrotic syndrome (SSNS), we conducted a genome-wide association study in 987 childhood SSNS patients and 3,206 healthy controls with Japanese ancestry. Beyond known associations in the HLA-DR/DQ region, common variants in NPHS1-KIRREL2 (rs56117924, P=4.94E-20, odds ratio (OR) =1.90) and TNFSF15 (rs6478109, P=2.54E-8, OR=0.72) regions achieved genome-wide significance and were replicated in Korean, South Asian and African populations. Trans-ethnic meta-analyses including Japanese, Korean, South Asian, African, European, Hispanic and Maghrebian populations confirmed the significant associations of variants in NPHS1-KIRREL2 (P_meta=6.71E-28, OR=1.88) and TNFSF15 (P_meta=5.40E-11, OR=1.33) loci. Analysis of the NPHS1 risk alleles with glomerular NPHS1 mRNA expression from the same person revealed allele specific expression with significantly lower expression of the transcript derived from the risk haplotype (Wilcox test p=9.3E-4). Because rare pathogenic variants in NPHS1 cause congenital nephrotic syndrome of the Finnish type (CNSF), the present study provides further evidence that variation along the allele frequency spectrum in the same gene can cause or contribute to both a rare monogenic disease (CNSF) and a more complex, polygenic disease (SSNS).

Relationship between soluble urokinase-type plasminogen activator receptor and serum biomarkers of endothelial activation in patients with idiopathic nephrotic syndrome

Background

Serum levels of soluble urokinase-type plasminogen activator receptor (suPAR) are high in some patients with idiopathic nephrotic syndrome (INS). Given that suPAR constitutes a predictor of vascular disease and has been associated with endothelial dysfunction, we hypothesized that suPAR levels are related to endothelial activation or dysfunction in INS patients. The aims of this study were to evaluate the relationship between serum concentrations of endothelial biomarkers and suPAR in patients with different histological patterns of INS and healthy controls, and to determine the demographic, clinical and biochemical characteristics of INS patients that influence suPAR serum levels.

Methods

This observational, cross-sectional study included patients with INS, diagnosed with minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS) or membranous nephropathy (MN) by renal biopsy. Patient demographic, clinical and biochemical characteristics were recorded and blood samples were obtained at the time of diagnosis. Measurements of suPAR and endothelial molecules via serum levels were performed using Enzyme-Linked ImmunoSorbent Assay kits.

Results

Patients with nephrotic syndrome (n = 152) caused by FSGS, MCD or MN had increased circulating levels of endothelial markers. suPAR levels positively correlated with age and the serum levels of almost all endothelial markers. Generally, endothelial cell molecules positively correlated with each other. suPAR levels were not associated with the histopathological pattern of INS.

Conclusions

In patients with INS secondary to FSGS, MCD and NM, circulating levels of suPAR are independent of the primary renal disease, and significantly associated with age, glomerular filtration rate and the levels of various endothelial markers.

CD80 expression and infiltrating regulatory T cells in idiopathic nephrotic syndrome of childhood

BACKGROUND

CD80 (also known as B7-1) is a co-stimulatory molecule that is expressed in biopsies and also excreted in urine in patients with minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS). CD80 is inhibited by the cytotoxic T-lymphocyte-associated-antigen 4 (CTLA4), which is mainly expressed on regulatory T cells (Tregs). Ineffective circulating Treg response is involved in the pathogenesis of nephrotic syndrome. In this study, we evaluated CD80 expression and infiltrating Tregs in children with MCD and FSGS.

METHODS

Evaluation of CD80 expression and semi-quantitative evaluation of Tregs (FOXP3-positive CD4 T cells) were carried out in 31 kidney biopsies (12 MCD, 19 FSGS) with immunofluorescence and immunohistochemistry staining.

RESULTS

All MCD sections were stained negative; whereas six out of 19 FSGS sections (all from steroid-resistant (SR) patients), including one from a Wilms' tumor 1 (WT1) mutation-positive FSGS patient, stained positive for anti-CD80 goat antibody, and negative for anti-CD80 rabbit antibody. FSGS biopsy specimens had significantly higher FOXP3-positive cells/mm² compared with MCD and control samples (P < 0.001). Biopsy samples from SR-FSGS patients (n = 12) with positive CD80 staining (n = 6) had significantly less Tregs (FOXP3-positive CD4 T cells) compared with CD80 (-) biopsies (n = 6; P = 0.004).

CONCLUSION

CD80 expression was not detected in the majority of the archival biopsy sections and the results were not consistent across the different antibodies. In the SR-FSGS sections, however, CD80-positive biopsies had decreased FOXP3-positive CD4 T cells, suggesting that a decreased anti-inflammatory milieu may be the cause of increased CD80 expression.

Compositional alterations of gut microbiota in children with primary nephrotic syndrome after initial therapy

Background

Primary nephrotic syndrome (PNS) is a common glomerular disease in children. T cell dysfunction plays a crucial role in the pathogenesis of PNS. Moreover, dysbiosis of gut microbiota contributes to immunological disorders. Whether the initial therapy of PNS affects gut microbiota remains an important question. Our study investigated compositional changes of gut microbiota after initial therapy.

Methods

Fecal samples of 20 children with PNS were collected before and after 4-week initial therapy. Total bacteria DNA were extracted and the V3-V4 regions of bacteria 16S ribosomal RNA gene were sequenced. The composition of gut microbiota before and after initial therapy was analyzed by bioinformatics methods. The function of altered gut microbiota was predicted with PICRUSt method.

Results

The richness and diversity of gut microbiota were similar before and after 4-week initial therapy. Gut microbiota at the phylum level was dominated by four phyla including Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria, but the increased relative abundance after initial therapy was found in Deinococcus-Thermus and Acidobacteria. At the genus level, the increased abundance of gut microbiota after initial therapy was observed in short chain fat acids (SCFA)-producing bacteria including Romboutsia, Stomatobaculum and Cloacibacillus (p < 0.05). Moreover, the predicted functional profile of gut microbiota showed that selenocompound metabolism, isoflavonoid biosynthesis and phosphatidylinositol signaling system weakened after initial therapy of PNS.

Conclusions

Initial therapy of PNS increased SCFA-producing gut microbiota, but might diminish selenocompound metabolism, isoflavonoid biosynthesis and phosphatidylinositol signaling system in children.

[Minimal change disease and focal segmental glomerulosclerosis]

Minimal change disease (MCD) or minimal change glomerulonephritis and focal segmental glomerulosclerosis (FSGS) are the two major causes of nephrotic syndrome in children and young adults. Both disease entities resemble each other and can sometimes only be discriminated on the basis of their clinical courses. MCD and FSGS display two classical examples that share a common pathophysiology in which the glomerular podocyte and the cytoskeleton of its foot processes play important roles. Therefore, the term "podocytopathy" was introduced for both diseases. In this article, we compare their differences and similarities, and summarized new data on pathophysiology and treatment. In adults, only a renal biopsy including electron microscopy allows for the discrimination of MCD and FSGS and other differential diagnoses. The identification of a primary or secondary form of the disease is based on the clinical course. Data from studies on the treatment are sparse; hence, treatment is still based on high-dose steroids followed by additional immunosuppressive agents. In secondary forms, treatment of the underlying disease is elementary.

PI3K/AKT and CD40L Signaling Regulate Platelet Activation and Endothelial Cell Damage in Sepsis

Platelets contribute to inflammation and their activation has been suggested as versatile effectors of sepsis. Activation of platelets promotes secretion of CD40L that induces sepsis and multiple organ dysfunction syndrome (MODS). However, the mechanisms regulate platelet-derived CD40L are not fully understood. Activation of PI3K/Akt pathway has been reported as a key component of sepsis, whereas the role of PI3K/Akt pathway in platelet-derived CD40L is unknown. In this study, we identified PI3K/Akt pathway as a key regulator of CD40L secretion by platelets. Significantly, inhibition of PI3K/Akt pathway by Ly294002 attenuated platelet activation and CD40L production. Moreover, PI3K/Akt pathway blocking suppresses vascular endothelial cells in vivo. Furthermore, the expression of biomarkers that represent the severity of sepsis, such as ICAM-1, VCAM-1, and E-selectin, was also suppressed by Ly294002. Altogether, our results confirm the pivotal role of PI3K/Akt pathway in sepsis and its inhibition might be a potential therapeutic target.

The elevated levels of urinary angiotensinogen are correlated with the severity of idiopathic membranous nephropathy

Background

Immunosuppressive treatment will predispose an idiopathic membranous nephropathy (iMN) patient to opportunistic infections. Disease severity is one of the main concerns for making the treatment decision. Urinary angiotensinogen (UAGT) level has been shown highly correlated with intrarenal renin-angiotensin system (RAS) activity and severity of chronic kidney diseases (CKD). We aimed to test the relationship between the UAGT level and the severity of iMN.

Methods

This cross-sectional study included a total of 48 biopsy-proven iMN patients, 46 minimal change disease (MCD) patients, and 44 healthy volunteers. The clinical and laboratory data and urine samples were collected from all subjects before the use of RAS inhibitors. We determined the UAGT levels with a method of enzyme-linked immunosorbent assay.

Results

The UAGT levels were not different between the iMN (277.05 ± 61.25, μg/g.Cr) and MCD patients (244.19 ± 40.24, μg/g.Cr), but both of them were significantly higher than those of healthy controls (6.85 ± 1.10, μg/g.Cr). UAGT levels were correlated negatively with serum albumin (r = − 0.393, p = 0.006) and estimated glomerular filtration rate (eGFR) (r = − 0.352, p = 0.014) and positively with 24-h proteinuria (r = 0.614, p < 0.001) in iMN patients but not in MCD patients. Multivariate linear regression analysis revealed that only proteinuria independently determinate the levels of UAGT (β = 0.649, p < 0.001) in iMN patients.

Conclusions

UAGT levels were correlated negatively with serum albumin and glomerular filtration rate and positively with proteinuria in iMN patients at the onset. This suggests that elevated levels of UAGT are associated with the severity of iMN. The UAGT level may be used as a cofactor for deciding immunosuppressive therapy in iMN patient.

[Up to date of pathophysiology mechanism of idiopathic nephrotic syndromes: Minimal change disease and focal and segmental glomerulosclerosis]

Idiopathic nephrotic syndrome represents up to 30% of adult glomerulopathies. However, its prognosis according to remission, relapse and renal failure remains unchanged since the 80s and prediction remains difficult. Physiopathology of adult idiopathic nephrotic syndrome is complex and multifactorial, including immunologic and environmental factors and a putative permeability-circulating factor, still unknown. In this point of view, we propose to summarize actual knowledge about idiopathic minimal change disease and focal and segmental glomerulosclerosis physiopathology.

Molecular and Cellular Mechanisms for Proteinuria in Minimal Change Disease

Minimal Change Disease (MCD) is a clinical condition characterized by acute nephrotic syndrome, no evident renal lesions at histology and good response to steroids. However, frequent recurrence of the disease requires additional therapies associated with steroids. Such multi-drug dependence and frequent relapses may cause disease evolution to focal and segmental glomerulosclerosis (FSGS) over time. The differences between the two conditions are not well defined, since molecular mechanisms may be shared by the two diseases. In some cases, genetic analysis can make it possible to distinguish MCD from FSGS; however, there are cases of overlap. Several hypotheses on mechanisms underlying MCD and potential molecular triggers have been proposed. Most studies were conducted on animal models of proteinuria that partially mimic MCD and may be useful to study glomerulosclerosis evolution; however, they do not demonstrate a clear-cut separation between MCD and FSGS. Puromycin Aminonucleoside and Adriamycin nephrosis are models of glomerular oxidative damage, characterized by loss of glomerular basement membrane polyanions resembling MCD at the onset and, at more advanced stages, by glomerulosclerosis resembling FSGS. Also Buffalo/Mna rats present initial lesions of MCD, subsequently evolving to FSGS; this mechanism of renal damage is clearer since this rat strain inherits the unique characteristic of overexpressing Th2 cytokines. In Lipopolysaccharide nephropathy, an immunological condition of renal toxicity linked to B7-1(CD80), mice develop transient proteinuria that lasts a few days. Overall, animal models are useful and necessary considering that they reproduce the evolution from MCD to FSGS that is, in part, due to persistence of proteinuria. The role of T/Treg/Bcells on human MCD has been discussed. Many cytokines, immunomodulatory mechanisms, and several molecules have been defined as a specific cause of proteinuria. However, the hypothesis of a single cell subset or molecule as cause of MCD is not supported by research and an interactive process seems more logical. The implication or interactive role of oxidants, Th2 cytokines, Th17, Tregs, B7-1(CD80), CD40/CD40L, c-Mip, TNF, uPA/suPAR, Angiopoietin-like 4 still awaits a definitive confirmation. Whole genome sequencing studies could help to define specific genetic features that justify a definition of MCD as a “clinical-pathology-genetic entity.”

Immunology of idiopathic nephrotic syndrome

The pathogenesis of idiopathic nephrotic syndrome (INS) is as yet unknown, but several lines of evidence indicate that the immune system may play a crucial pathogenic role in non-genetic INS. The most important of these are, first, the effectiveness of therapy based on immunosuppression and, second, a vast body of data derived both from experimental models and from patient studies that implicate T cells and more recently B cells as major players in INS pathogenesis. However, recent findings also suggest a direct role of podocytes as drivers of the disease process, and the interplay between the glomerulus and the immune system is still being elucidated. In this review we provide an overview of current knowledge on the role of different components of the immune system in determining disease. Advances in our understanding of the pathogenesis of INS may help drive new, more tailored therapeutic approaches.

Increased PD-1+CD154+ Tfh cells are possibly the most important functional subset of PD-1+ T follicular helper cells in adult patients with minimal change disease

T follicular helper (Tfh) cells, especially programmed cell death protein 1 (PD-1)+ Tfh cells, exert important functions in the normal immune response. The purpose of this study was to determine the frequency of different subsets of PD-1+ Tfh cells and their functional effects in adult patients with minimal change disease (MCD). The frequencies of circulating PD-1+, PD-1+CD154+, and PD-1+interleukin (IL)-21+ Tfh cells, and CD38+CD19+ and CD38+CD19+CD40+ B cells, as well as serum IL-2, IL-4, IL-17A, IL-6, IL-21, and interferon (IFN)-γ were significantly increased in the MCD patients compared with the healthy controls (HCs) (P < 0.05). However, no significant difference was found in PD-1+BCL-6+ or PD-1+ICOS+ Tfh cells. Furthermore, the percentages of PD-1+ Tfh and PD-1+CD154+ Tfh cells were negatively correlated with the estimated glomerular filtration rate (eGFR), but positively correlated with the 24-h urinary protein concentration and serum IL-21 level. The percentages of PD-1+ Tfh and PD-1+CD154+ Tfh cells were positively correlated with the percentages of CD38+ plasma cells and active CD38+CD40+ plasma cells, respectively. After an 8-12-week treatment with prednisolone, the percentages of PD-1+, PD-1+CD154+, and PD-1+IL-21+ Tfh cells as well as the serum level of IL-21 were significantly reduced; in contrast, the serum levels of IL-4 and IL-10 were increased (P < 0.05). We conclude that increased PD-1+CD154+ Tfh cells are possibly the most important functional subset of PD-1+ Tfh cells and may contribute towards the pathogenesis of MCD.

Regulatory T cells in renal disease

The kidney is vulnerable to injury, both acute and chronic from a variety of immune and metabolic insults, all of which at least to some degree involve inflammation. Regulatory T cells modulate systemic autoimmune and allogenic responses in glomerulonephritis and transplantation. Intrarenal regulatory T cells (Tregs), including those recruited to the kidney, have suppressive effects on both adaptive and innate immune cells, and probably also intrinsic kidney cells. Evidence from autoimmune glomerulonephritis implicates antigen-specific Tregs in HLA-mediated dominant protection, while in several human renal diseases Tregs are abnormal in number or phenotype. Experimentally, Tregs can protect the kidney from injury in a variety of renal diseases. Mechanisms of Treg recruitment to the kidney include via the chemokine receptors CCR6 and CXCR3 and potentially, at least in innate injury TLR9. The effects of Tregs may be context dependent, with evidence for roles for immunoregulatory roles both for endogenous Tbet-expressing Tregs and STAT-3-expressing Tregs in experimental glomerulonephritis. Most experimental work and some of the ongoing human trials in renal transplantation have focussed on unfractionated thymically derived Tregs (tTregs). However, induced Tregs (iTregs), type 1 regulatory T (Tr1) cells and in particular antigen-specific Tregs also have therapeutic potential not only in renal transplantation, but also in other kidney diseases.

Clinical trials in minimal change disease

Minimal change disease (MCD) is a pathological condition characterized by subtle glomerular lesions causing massive and reversible proteinuria that is usually steroid sensitive. Recurrence of symptoms of active disease following successful treatment (including proteinuria, oedema and oliguria) and steroid toxicity requires the use of other drugs to attain or maintain remission. Unresolved MCD is considered the initial step in the pathological pathway leading to focal and segmental glomerulosclerosis (FSGS). Historically, cyclophosphamide, chlorambucil, mycophenolate and calcineurin inhibitors have been utilized with success in MCD; however, the chronic nature of the disease and the toxicity of long-term use of these medications has pushed the development of new therapies. Synthetic corticotropin (adrenocorticotropic hormone) and anti-CD20 monoclonal antibodies, for example, are currently under investigation in clinical trials. In addition, these new interventions have dramatically impacted our understanding of the mechanisms of the disease. Phase II-IV clinical trials targeting new mechanisms and/or molecules are in progress. The list is long and includes drugs blocking the adaptive immune system (abatacept and anti-CD40 antibodies), as well as retinoids and the sialic acid precursor N-acetyl-D-mannosamine (ManNAc), two agents that affect the sieving properties of the glomerular basement membrane. Other drugs are being tested against FSGS and, if successful, could also be utilized against MCD. Clinical trials currently in progress should furnish a proper solution to what appears to be a solvable problem.

Mesenchymal Stem Cells May Ameliorate Nephrotic Syndrome Post-Allogeneic Hematopoietic Stem Cell Transplantation-Case Report

INTRODUCTION

Because of their immunomodulatory and anti-inflammatory effects, mesenchymal stem cells (MSCs) have been considered as potential therapeutic agents for treating immune-related or autoimmune diseases, such as graft-versus-host disease (GVHD). Nephrotic syndrome (NS) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is an uncommon complication with unclear etiology and pathogenesis. It may be an immune disorder involving immune complex deposition, B cells, regulatory T cells (Tregs), and Th1 cytokines and be a manifestation of chronic GVHD. Corticosteroids and calcium antagonists, alone or in combination, are the most common therapeutic agents in this setting. Rituximab is commonly administered as salvage treatment. However, treatment failure and progressive renal function deterioration has been reported to occur in approximately 20% of patients in a particular cohort.

CASE PRESENTATION

We present a patient who developed NS 10 months after allo-HSCT. After treatment failure with cyclosporine A, prednisone, and rituximab, she achieved a complete response with MSC treatment. The clinical improvement of this patient was accompanied by a decreased B cell population together with an increased frequency of regulatory B cells (Bregs) and Tregs after MSC treatment.

CONCLUSION

MSCs could modulate NS after allo-HSCT by suppressing B cell proliferation, inducing Tregs and Bregs, and inhibiting inflammatory cytokine production by monocytes and NK cells. Among all these, Bregs might play an important role in ameliorating the NS of this patient.

Role of gut microbiota in idiopathic nephrotic syndrome in children

Nephrotic syndrome characterized by heavy proteinuria and edema is the most common chronic kidney disease in children. It is classified into three categories, of which the idiopathic type accounts for the vast majority of cases. As indicated by the name, the etiology of idiopathic nephrotic syndrome remains unknown though it has been suggested that impaired T cell function is involved. Recently, evidence has mounted to suggest that dysfunction in regulatory T cells plays an important role in the development of allergic disease, a recognized comorbid condition for children with idiopathic nephrotic syndrome. It is known that regulatory T cells are mainly induced by short chain fatty acids produced by gut microbiota and that children with allergy are reported to have aberrant gut microbiota. On this basis, we hypothesize that an aberrant microbiota, i.e., dysbiosis in the gut resulting in defective induction of regulatory T cells, is also involved in the etiology of idiopathic nephrotic syndrome in children. Our hypothesis can be directly tested by metagenome analysis using bacterial DNA extracted from the feces of patients with idiopathic nephrotic syndrome. Indirect evidence could be obtained by epidemiological survey, such as a comparative study of the environmental factors influencing the initial colonization of gut microbiota between patients with idiopathic nephrotic syndrome and age-matched healthy children. Factors that may disrupt this colonization include a cesarean delivery, formula feeding, excessive use of antibiotics, or the introduction of inappropriate solid foods containing a high amount of saturated fat. Based on this hypothesis, we suggest it would be clinically worthwhile to study whether administration of probiotics composed of commensal bacteria known to efficiently induce regulatory T cells in vitro could control the exacerbation or relapse of INS.

Regulatory T cells and CTLA-4 in idiopathic nephrotic syndrome

The pathogenesis of idiopathic nephrotic syndrome (INS) remains unknown. Recently, it was postulated that suppression of regulatory T cells (Treg) leads to massive proteinuria in INS, although there is some controversy. Considering the important role of cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) in Treg-mediated immune suppression, the aim of this study was therefore to clarify the involvement of Treg and CTLA-4 in the pathogenesis of INS. Fifteen patients with INS were enrolled. Their blood was sampled twice, once at onset and once at remission induced by glucocorticoid. Although median Treg number was significantly lower at onset than in healthy children, it increased at remission. Similarly, serum CTLA-4 concentration significantly increased at remission compared with onset. Furthermore, a positive significant correlation was observed between Treg number and serum CTLA-4 level. This suggests that Treg and CTLA-4 are involved in the induction of remission in INS.

Rituximab in Minimal Change Disease: Mechanisms of Action and Hypotheses for Future Studies

Treatment with rituximab, a monoclonal antibody against the B-lymphocyte surface protein CD20, leads to the depletion of B cells. Recently, rituximab was reported to effectively prevent relapses of glucocorticoid-dependent or frequently relapsing minimal change disease (MCD). MCD is thought to be T-cell mediated; how rituximab controls MCD is not understood. In this review, we summarize key clinical studies demonstrating the efficacy of rituximab in idiopathic nephrotic syndrome, mainly MCD. We then discuss immunological features of this disease and potential mechanisms of action of rituximab in its treatment based on what is known about the therapeutic action of rituximab in other immune-mediated disorders. We believe that studies aimed at understanding the mechanisms of action of rituximab in MCD will provide a novel approach to resolve the elusive immune pathophysiology of MCD.

Minimal Change Disease

Minimal change disease (MCD) is a major cause of idiopathic nephrotic syndrome (NS), characterized by intense proteinuria leading to edema and intravascular volume depletion. In adults, it accounts for approximately 15% of patients with idiopathic NS, reaching a much higher percentage at younger ages, up to 70%-90% in children >1 year of age. In the pediatric setting, a renal biopsy is usually not performed if presentation is typical and the patient responds to therapy with oral prednisone at conventional doses. Therefore, in this setting steroid-sensitive NS can be considered synonymous with MCD. The pathologic hallmark of disease is absence of visible alterations by light microscopy and effacement of foot processes by electron microscopy. Although the cause is unknown and it is likely that different subgroups of disease recognize a different pathogenesis, immunologic dysregulation and modifications of the podocyte are thought to synergize in altering the integrity of the glomerular basement membrane and therefore determining proteinuria. The mainstay of therapy is prednisone, but steroid-sensitive forms frequently relapse and this leads to a percentage of patients requiring second-line steroid-sparing immunosuppression. The outcome is variable, but forms of MCD that respond to steroids usually do not lead to chronic renal damage, whereas forms that are unresponsive to steroids may subsequently reveal themselves as FSGS. However, in a substantial number of patients the disease is recurrent and requires long-term immunosuppression, with significant morbidity because of side effects. Recent therapeutic advances, such as the use of anti-CD20 antibodies, have provided long-term remission off-therapy and suggest new hypotheses for disease pathogenesis.

Rituximab use in adult primary glomerulopathy: where is the evidence?

Rituximab is a chimeric anti-CD20 antibody that results in depletion of B-cell lymphocytes. It is currently used in the treatment of a variety of autoimmune diseases, in addition to CD20-positive lymphomas. The use of rituximab in the treatment of the adult primary glomerular diseases has emerged recently, although not yet established as first-line therapy in international guidelines. In patients with steroid-dependent minimal change disease or frequently relapsing disease, and in patients with idiopathic membranous nephropathy (IMN), several retrospective and prospective studies support the use of rituximab to induce remission, whereas in idiopathic focal and segmental glomerulosclerosis (FSGS), the use of rituximab has resulted in variable results. Evidence is still lacking for the use of rituximab in patients with immunoglobulin A nephropathy (IgAN) and idiopathic membranoproliferative glomerulonephritis (MPGN), as only few reports used rituximab in these two entities. Randomized controlled trials (RCTs) are warranted and clearly needed to establish the definitive role of rituximab in the management of steroid-dependent and frequently relapsing minimal change disease, IMN, both as first-line and second-line treatment, and in MPGN. We await the results of an ongoing RCT of rituximab use in IgAN. Although current evidence for the use of rituximab in patients with idiopathic FSGS is poor, more RCTs are needed to clarify its role, if any, in the management of steroid-resistant or steroid-dependent FSGS.

Anti-CD20 Antibodies for Idiopathic Nephrotic Syndrome in Children

Rituximab, a chimeric anti-CD20 monoclonal antibody originally licensed for lymphoma, is emerging as a novel steroid-sparing agent for idiopathic nephrotic syndrome in children. The potential use of anti-CD20 monoclonal antibodies in idiopathic nephrotic syndrome has contributed to shifting the view of podocytopathies from T cell-mediated to more complex immunomediated disorders that can benefit from targeting B cells and other mediators of the early immune response. Clinical data on the use of rituximab also have implications on disease management and classification. In this review, we present results of clinical studies that support rituximab as an effective steroid-sparing agent in steroid-dependent idiopathic nephrotic syndrome. Recent randomized controlled trials suggest that potential benefits of rituximab therapy in steroid-dependent forms of idiopathic nephrotic syndrome vary depending on whether children are dependent on steroids alone or on both steroids and calcineurin inhibitors, with greater probabilities to achieve drug-free remission in the former group. Multiple-drug dependence may identify a different disease state with different prognosis and treatment options. Insufficient data are available on optimal use of rituximab as a maintenance steroid-sparing agent in these steroid-sensitive forms of the disease, including how often and for how long rituximab infusions should be repeated to maximize expected benefits and minimize potential harms. Finally, one randomized controlled trial in children with steroid-resistant idiopathic nephrotic syndrome yielded negative results. New anti-CD20 antibodies are under study in this patient population.