B cell-derived IL-4 acts on podocytes to induce proteinuria and foot process effacement

Role of the Innate Immune Response in Glomerular Disease Pathogenesis: Focus on Podocytes

Accumulating evidence indicates that inflammatory and immunologic processes play a significant role in the development and progression of glomerular diseases. Podocytes, the terminally differentiated epithelial cells, are crucial for maintaining the integrity of the glomerular filtration barrier. Once injured, podocytes cannot regenerate, leading to progressive proteinuric glomerular diseases. However, emerging evidence suggests that podocytes not only maintain the glomerular filtration barrier and are important targets of immune responses but also exhibit many features of immune-like cells, where they are involved in the modulation of the activity of innate and adaptive immunity. This dual role of podocytes may lead to the discovery and development of new therapeutic targets for treating glomerular diseases. This review aims to provide an overview of the innate immunity mechanisms involved in podocyte injury and the progression of proteinuric glomerular diseases.

Focal Segmental Glomerulosclerosis

Focal segmental glomerular sclerosis (FSGS) is a histological lesion characterized by sclerosis in sections (segmental) of some glomeruli (focal) in association with podocyte injury. Historically, FSGS has often been characterized as a disease, but it is a heterogeneous entity based on etiology, clinical course, and therapeutic approach. A unifying feature is podocyte injury and loss, which can be primary or the result of secondary maladaptive responses to glomerular stressors. FSGS has been demonstrated over time to carry a large health burden and remains a leading glomerular cause of ESRD globally. Recent clinical practice guidelines highlight the unmet scientific need for better understanding of disease pathogenesis, particularly for immunologic etiologies, as well as more targeted therapeutic drug development. In this review, we will discuss the current FSGS classification scheme, pathophysiologic mechanisms of injury, and treatment guidelines, along with emerging and investigational therapeutics.

Swollen Feet: Considering the Paradoxical Roles of Interleukins in Nephrotic Syndrome

Interleukins are a family of 40 bioactive peptides that act through cell surface receptors to induce a variety of intracellular responses. While interleukins are most commonly associated with destructive, pro-inflammatory signaling in cells, some also play a role in promoting cellular resilience and survival. This review will highlight recent evidence of the cytoprotective actions of the interleukin 1 receptor (IL-1R)- and common gamma chain receptor (IL-Rγc)-signaling cytokines in nephrotic syndrome (NS). NS results from the injury or loss of glomerular visceral epithelial cells (i.e., podocytes). Although the causes of podocyte dysfunction vary, it is clear that pro-inflammatory cytokines play a significant role in regulating the propagation, duration and severity of disease. Pro-inflammatory cytokines signaling through IL-1R and IL-Rγc have been shown to exert anti-apoptotic effects in podocytes through the phosphoinositol-3-kinase (PI-3K)/AKT pathway, highlighting the potential utility of IL-1R- and IL-Rγc-signaling interleukins for the treatment of podocytopathy in NS. The paradoxical role of interleukins as drivers and mitigators of podocyte injury is complex and ill-defined. Emerging evidence of the cytoprotective role of some interleukins in NS highlights the urgent need for a nuanced understanding of their pro-survival benefits and reveals their potential as podocyte-sparing therapeutics for NS.

Understanding the podocyte immune responses in proteinuric kidney diseases: from pathogenesis to therapy

The glomerular filtration barrier, comprising the inner layer of capillary fenestrated endothelial cells, outermost podocytes, and the glomerular basement membrane between them, plays a pivotal role in kidney function. Podocytes, terminally differentiated epithelial cells, are challenging to regenerate once injured. They are essential for maintaining the integrity of the glomerular filtration barrier. Damage to podocytes, resulting from intrinsic or extrinsic factors, leads to proteinuria in the early stages and eventually progresses to chronic kidney disease (CKD). Immune-mediated podocyte injury is a primary pathogenic mechanism in proteinuric glomerular diseases, including minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, and lupus nephritis with podocyte involvement. An extensive body of evidence indicates that podocytes not only contribute significantly to the maintenance of the glomerular filtration barrier and serve as targets of immune responses but also exhibit immune cell-like characteristics, participating in both innate and adaptive immunity. They play a pivotal role in mediating glomerular injury and represent potential therapeutic targets for CKD. This review aims to systematically elucidate the mechanisms of podocyte immune injury in various podocyte lesions and provide an overview of recent advances in podocyte immunotherapy. It offers valuable insights for a deeper understanding of the role of podocytes in proteinuric glomerular diseases, and the identification of new therapeutic targets, and has significant implications for the future clinical diagnosis and treatment of podocyte-related disorders.

β1-Integrin blockade prevents podocyte injury in experimental models of minimal change disease

INTRODUCTION

Activation of the focal adhesion kinase (FAK) in podocytes is involved in the pathogenesis of minimal change disease (MCD), but the pathway leading to its activation in this disease is unknown. Here, we tested whether podocyte β1 integrin is the upstream modulator of FAK activation and podocyte injury in experimental models of MCD-like injury.

METHODS

We used lipopolysaccharide (LPS) and MCD sera to induce MCD-like changes in vivo and in cultured human podocytes, respectively. We performed functional studies using specific β1 integrin inhibitors in vivo and in vitro, and integrated histological analysis, western blotting, and immunofluorescence to assess for morphological and molecular changes in podocytes. By ELISA, we measured serum LPS levels in 35 children with MCD or presumed MCD (idiopathic nephrotic syndrome [INS]) and in 18 healthy controls.

RESULTS

LPS-injected mice showed morphological (foot process effacement, and normal appearing glomeruli on light microscopy) and molecular features (synaptopodin loss, nephrin mislocalization, FAK phosphorylation) characteristic of human MCD. Administration of a β1 integrin inhibitor to mice abrogated FAK phosphorylation, and ameliorated proteinuria and podocyte injury following LPS. Children with MCD/INS in relapse had higher serum LPS levels than controls. In cultured human podocytes, β1 integrin blockade prevented cytoskeletal rearrangements following exposure to MCD sera in relapse.

CONCLUSIONS

Podocyte β1 integrin activation is an upstream mediator of FAK phosphorylation and podocyte injury in models of MCD-like injury.

The Importance of Sphingomyelin Phosphodiesterase Acid-Like 3b (SMPDL-3b) Levels in Kidney Biopsy Specimens of Children With Nephrotic Syndrome

OBJECTIVE

It remains unclear whether the low amount of SMPDL-3b required for rituximab binding is the cause of treatment resistance in patients with treatment-resistant nephrotic syndrome with advanced podocyte injury. Given the limited number of studies on the relationship between rituximab and SMPDL-3b, this study was conducted to assess whether SMPDL-3b levels in pretreatment renal biopsy specimens can be used to predict the clinical effectiveness of immunosuppressive drugs, especially rituximab, in children with nephrotic syndrome.

METHODS

Kidney biopsy specimens from 44 patients diagnosed with idiopatic nephrotic syndrome were analyzed using immunohistochemical staining with an anti-SMPDL-3b antibody and real-time polymerase chain reaction (PCR) for SMPDL-3b mRNA expression.

RESULTS

We showed that SMPDL-3b mRNA expression and anti-SMPDL-3b antibody staining did not differ significantly between the patient groups with different responses to immunosuppressive therapies.

CONCLUSION

Our results suggest that SMPDL-3b may actually be an indicator of disease progression rather than a marker for predicting response to a particular immunosuppressive agent.

Use of Rituximab in Childhood Idiopathic Nephrotic Syndrome

Rituximab is an established therapy in children with idiopathic nephrotic syndrome to sustain short- to medium-term disease remission and avoid steroid toxicities. Recent trials focus on its use as a first-line agent among those with milder disease severity. Rituximab is used in multidrug refractory nephrotic syndrome and post-transplant disease recurrence, although the evidence is much less substantial. Available data suggest that the treatment response to rituximab depends on various patient factors, dosing regimen, and the concomitant use of maintenance immunosuppression. After repeated treatments, patients are found to have an improving response overall with a longer relapse-free period. The drug effect, however, is not permanent, and 80% of patients eventually relapse and many will require an additional course of rituximab. This underpins the importance of understanding the long-term safety profile on repeated treatments. Although rituximab appears to be generally safe, there are concerns about long-term hypogammaglobulinemia, especially in young children. Reliable immunophenotyping and biomarkers are yet to be discovered to predict treatment success, risk of both rare and severe side effects, e.g. , persistent hypogammaglobulinemia, and guiding of redosing strategy. In this review, we highlight recent advances in the use of rituximab for childhood nephrotic syndrome and how the therapeutic landscape is evolving.

The ion transporter Na+-K+-ATPase enables pathological B cell survival in the kidney microenvironment of lupus nephritis

The kidney is a comparatively hostile microenvironment characterized by highsodium concentrations; however, lymphocytes infiltrate and survive therein in autoimmune diseases such as lupus. The effects of sodium-lymphocyte interactions on tissue injury in autoimmune diseases and the mechanisms used by infiltrating lymphocytes to survive the highsodium environment of the kidney are not known. Here, we show that kidney-infiltrating B cells in lupus adapt to elevated sodium concentrations and that expression of sodium potassium adenosine triphosphatase (Na⁺-K⁺-ATPase) correlates with the ability of infiltrating cells to survive. Pharmacological inhibition of Na⁺-K⁺-ATPase and genetic knockout of Na⁺-K⁺-ATPase γ subunit resulted in reduced B cell infiltration into kidneys and amelioration of proteinuria. B cells in human lupus nephritis biopsies also had high expression of Na⁺-K⁺-ATPase. Our study reveals that kidney-infiltrating B cells in lupus initiate a tissue adaption program in response to sodium stress and identifies Na⁺-K⁺-ATPase as an organ-specific therapeutic target.

Contribution of IL-33/ILC2-mediated Th2 cytokines during the progression of minimal change disease

Minimal change disease (MCD) is a common type of nephrotic syndrome with high recurrence rate. This study aims to explore the impacts of interleukin (IL)-33 in MCD and to discuss its potential mechanism. In adriamycin (ADM) and puromycin aminonucleoside (PAN)-induced MCD rat model, IL-33 was used for treatment. H&E staining was applied for detecting histological changes. Critical proteins were examined by western blot. Corresponding commercial kits tested oxidative stress- and inflammation-related factors. Cell apoptosis was measured by TUNEL assay. ADM-induced podocyte injury model was establish to mimic MCD in vitro. Cell proliferation and apoptosis were detected by CCK-8 and TUNEL assays. Finally, podocyte was stimulated by innate lymphoid type-2 cells-secreted Th2 cytokines (ILC2s: IL-13 and IL-5 respectively), with or without incubation with M1 macrophage medium to further explore the immune-regulation of ILC2s behind the inflammatory environment of MCD. It was found that PAN-induced kidney jury, inflammation, oxidative stress and apoptosis were severer than ADM, and IL-33 treatment significantly alleviated the above injuries in PAN and ADM-induced MCD rat model. Moreover, IL-33 reversed the reduced viability and increased oxidative stress and apoptosis in ADM-induced podocyte injury model. Further, the capacities of IL-13 alone in inducing M1/M2 macrophage polarization, apoptosis, inflammation, kidney injury and reducing cell viability are stronger than IL-5. However, IL-13 reversed reduced cell viability and stimulated apoptosis, inflammation, kidney injury mediated by co-incubation with M1-conditioned medium. Collectively, IL-33 might protect against immunologic injury in MCD via mediating ILC2s-secreted IL-13.

Sexual dimorphism in acute myocardial infarction-induced acute kidney injury: cardiorenal deteriorating effects of ovariectomy in premenopausal female mice

Acute kidney injury (AKI) is a common complication of cardiovascular diseases (CVDs) in both males and females, increasing mortality rate substantially. Premenopausal females appear to be more protected, suggesting a potential protective role of female sex hormones. Here, we tested the hypothesis that ovariectomy (OVX) eliminates the beneficial effect of female sex on renal protection following acute myocardial infarction (MI). Seven days post-MI, both sexes exhibited worsened kidney function and a substantial decrease in total kidney NAD levels. Unlike MI female mice, MI males showed exacerbated morphological alterations with increased proinflammatory, proapoptotic, and profibrotic biomarkers. The expression of NAD+ biosynthetic enzymes NAMPT and NMRK-1 was increased in MI females only, while males showed a substantial increase in NAD+ consuming enzyme PARP-1. OVX did not eliminate the female-sex protection of glomerular morphology but was associated with swelling of proximal convoluted tubules with MI as in males. With OVX, MI females had enhanced proinflammatory cytokine release, and a further decrease in creatinine clearance and urine output was observed. Our findings suggest that MI induced AKI in both sexes with pre-menopausal female mice being more protected. Ovariectomy worsens aspects of AKI in females after MI, which may portend increased risk for development of chronic kidney disease.

Severity of Vitamin D Deficiency in Children with Nephrotic Syndrome: A Study from Tertiary Care Center in Northern India

In nephrotic syndrome (NS) due to podocytopathies, loss of vitamin D binding globulin along with albumin in urine leads to Vitamin D deficient state. We aimed to study the severity of vitamin D deficiency and its clinical correlation in children with NS. We performed a cross-sectional study at a tertiary care hospital in Northern India. Enrolment of children aged 1-18 years was done. Patient's detailed history, numbers of relapse, treatment details, and data regarding various immunomodulatory drugs treatment. Vitamin D level was estimated, and its status was further classified as deficiency <20 ng/mL and insufficiency 20-30 ng/mL as per Global Consensus Recommendations on evaluation, treatment, and prevention of vitamin D deficiency. Continuous variables were compared using tests such as unpaired t-test, Kruskal-Wallis test, and Wilcoxon rank sum test depending on the distribution of parameters. Categorical variables were compared using Chi-squared tests or Fisher's exact test. A total of 96 children with NS were screened, of which 77.1% had vitamin D deficiency. The mean serum vitamin D level was 14.393 ± 8.52 ng/mL. Among the 48 children of the first episode of NS 36 were deficient (36/48 = 75%). Whereas in the relapse category, 30 patients had infrequently relapsing NS (deficient 24/30 = 80%). Eleven children had frequently relapsing NS; among them, 10 were vitamin D deficient (10/11 = 90.9%), and there was a negative correlation between vitamin D level and duration of illness. Vitamin D deficiency is a common comorbidity in children with NS. Given the putative immunomodulatory property of vitamin D, this deficiency should be identified and treated routinely in all cases of NS.

Pathogenic Role of MicroRNA Dysregulation in Podocytopathies

MicroRNAs (miRNAs) participate in the regulation of various important biological processes by regulating the expression of various genes at the post-transcriptional level. Podocytopathies are a series of renal diseases in which direct or indirect damage of podocytes results in proteinuria or nephrotic syndrome. Despite decades of research, the exact pathogenesis of podocytopathies remains incompletely understood and effective therapies are still lacking. An increasing body of evidence has revealed a critical role of miRNAs dysregulation in the onset and progression of podocytopathies. Moreover, several lines of research aimed at improving common podocytopathies diagnostic tools and avoiding invasive kidney biopsies have also identified circulating and urine miRNAs as possible diagnostic and prognostic biomarkers for podocytopathies. The present review mainly aims to provide an updated overview of the recent achievements in research on the potential applicability of miRNAs involved in renal disorders related to podocyte dysfunction by laying particular emphasis on focal segmental glomerulosclerosis (FSGS), minimal change disease (MCD), membranous nephropathy (MN), diabetic kidney disease (DKD) and IgA nephropathy (IgAN). Further investigation into these dysregulated miRNAs will not only generate novel insights into the mechanisms of podocytopathies, but also might yield novel strategies for the diagnosis and therapy of this disease.

The immunopathogenesis of idiopathic nephrotic syndrome: a narrative review of the literature

Idiopathic nephrotic syndrome (INS) is a common glomerular disease in childhood, and the immunological involvement in the pathogenesis of non-genetic INS, although not fully elucidated, is evident. This narrative review aims to offer a concise and in-depth view of the current knowledge on the immunological mechanisms of the development of INS as well as the role of the immunological components of the disease in the responsiveness to treatment. T cell immunity appears to play a major role in the INS immunopathogenesis and has been the first to be linked to the disease. Various T cell immunophenotypes are implicated in INS, including T-helper-1, T-helper-2, T-helper-17, and T regulatory cells, and various cytokines have been proposed as surrogate biomarkers of the disease; however, no distinct T helper or cytokine profile has been conclusively linked to the disease. More recently, the recognition of the role of B cell mediated immunity and the various B cell subsets that are dysregulated in patients with INS have led to new hypotheses on the underlying immunological causes of INS. Finally, the disambiguation of the exact mechanisms of the INS development in the future may be the key to the development of more targeted personalized approaches in managing INS.

CONCLUSIONS

INS demonstrates particularly interesting immunopathogenetic pathways, in which multiple interactions between T cell and B cell immunity and the podocyte are involved. The disambiguation of these pathways will provide promising novel therapeutic targets in INS.

WHAT IS KNOWN

• INS is the most common glomerular disease in the paediatric population, and its onset and relapses have been linked to various immunological triggers. • Multiple immunological mechanisms have been implicated in the pathogenesis of INS; however, no single distinct immunological profile has been recognized.

WHAT IS NEW

• Th17 cells and Treg cells play an important role in the immune dysregulation in INS. • Transitional B cell levels as well as the transitional/memory B cell ratio have been correlated to nephrotic relapses and have been proposed as biomarkers of INS relapses in SSNS patients.

Role of the adaptive immune system in diabetic kidney disease

Diabetic kidney disease (DKD) is a highly prevalent complication of diabetes and the leading cause of end-stage kidney disease. Inflammation is recognized as an important driver of progression of DKD. Activation of the immune response promotes a pro-inflammatory milieu and subsequently renal fibrosis, and a progressive loss of renal function. Although the role of the innate immune system in diabetic renal disease has been well characterized, the potential contribution of the adaptive immune system remains poorly defined. Emerging evidence in experimental models of DKD indicates an increase in the number of T cells in the circulation and in the kidney cortex, that in turn triggers secretion of inflammatory mediators such as interferon-γ and tumor necrosis factor-α, and activation of cells in innate immune response. In human studies, the number of T cells residing in the interstitial region of the kidney correlates with the degree of albuminuria in people with type 2 diabetes. Here, we review the role of the adaptive immune system, and associated cytokines, in the development of DKD. Furthermore, the potential therapeutic benefits of targeting the adaptive immune system as a means of preventing the progression of DKD are discussed.

B-Cell Dysregulation in Idiopathic Nephrotic Syndrome: What We Know and What We Need to Discover

The therapeutic efficacy of B-cell depletion by anti-CD20 treatment in pediatric and, more recently, in adult idiopathic nephrotic syndrome patients suggests a key role of B cells in the pathogenesis of the disease. However, their exact role is still unclear. B cells are able to secrete a large variety of antibodies that can protect against infections. However, B-cell dysregulation is well-established in a variety of autoimmune diseases. In parallel with their ability to produce antibodies, pathogenic B cells display altered effector functions by expressing activating surface molecules, which can strongly modify the immune homeostasis, or by producing specific cytokines, which can directly affect either podocyte structure and functions or modulate T-cell homeostasis. Herein, we report the most relevant clinical and experimental evidences of a pathogenic role of B cells in idiopathic nephrotic syndrome. We further highlight similarities and differences between children and adults affected by non-genetic forms of the disease and discuss what needs to be investigated in order to define the exact mechanisms underlying the pathogenic role of B cells and to identify more tailored therapeutic approaches.

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.

UK experience of ofatumumab in recurrence of focal segmental glomerulosclerosis post-kidney transplant

BACKGROUND

Steroid-resistant nephrotic syndrome (SRNS), commonly caused by focal segmental glomerulosclerosis (FSGS), is associated with progression to stage 5 chronic kidney disease, requirement for kidney replacement therapy and a risk of disease recurrence post-kidney transplantation. Ofatumumab (OFA) is a fully humanised monoclonal antibody to CD20, with similar mechanisms of action to rituximab (RTX).

METHODS

We report a case series of seven UK patients (five paediatric, two adult), all of whom developed FSGS recurrence after kidney transplantation and received OFA as part of their therapeutic intervention. All also received concomitant plasmapheresis. The 2-year outcome of these seven patients is reported, describing clinical course, kidney function and proteinuria.

RESULTS

Four patients (all paediatric) achieved complete urinary remission with minimal proteinuria 12 months post-treatment. Three of those four also had normal graft function. Two patients showed partial remission-brief improvement to non-nephrotic proteinuria (197 mg/mmol) in one patient, maintained improvement in kidney function (estimated glomerular filtration rate 76 ml/min/1.73 m²) in the other. One patient did not demonstrate any response.

CONCLUSIONS

OFA may represent a useful addition to therapeutic options in the management of FSGS recurrence post-transplantation, including where RTX has shown no benefit. Concomitant plasmapheresis in all patients prevents any definitive conclusion that OFA was the beneficial intervention.

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.

The Efficacy and Safety of Rituximab for Childhood Steroid-Dependent Nephrotic Syndrome: A Systematic Review and Meta-Analysis

Objectives: Rituximab (RTX), a possible alternative treatment option, is recognized as a new therapeutic hope for the treatment of steroid-dependent nephrotic syndrome (SDNS) in children. However, the efficacy and safety of RTX in the treatment of childhood SDNS are still controversial. The objective of this study was to evaluate the efficacy and safety of RTX treatment in children with SDNS. Study Design: Six randomized controlled trials (RCTs) and one retrospective comparative control study data from studies, performed before January 2021 were collected, from PubMed, Cochrane Library, Embase, and Web of Science. The studies evaluating the efficacy and safety of RTX in childhood SDNS were included. Results: Six RCTs and one retrospective comparative control study were included in our analysis. Compared with the control group, the RTX treatment group achieved a higher complete remission rate (OR = 5.21; 95% CI, 3.18-8.54; p < 0.00001), and we found significant differences between the two groups on serum albumin level (MD = 0.88; 95% CI, 0.43-1.33; p = 0.0001) and estimated glomerular filtration rate (MD = 6.43; 95% CI, 2.68-10.19; p = 0.0008). However, RTX treatment did not significantly lower serum creatinine levels nor did it significantly reduce the occurrence of proteinuria. In addition, we found no advantages with RTX on treatment safety. Conclusions: RTX has shown satisfactory characteristics in terms of efficacy and may be a promising treatment method for SDNS in children. However, the long-term effects have not been fully evaluated and should be further studied through randomized clinical trials.

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.

Chemokine/Cytokine Levels Correlate with Organ Involvement in PR3-ANCA-Associated Vasculitis

Background: ANCA-associated vasculitis (AAV) is a rare small vessel disease characterized by multi-organ involvement. Biomarkers that can measure specific organ involvement are missing. Here, we ask whether certain circulating cytokines and chemokines correlate with renal involvement and if distinct cytokine/chemokine patterns can differentiate between renal, ear/nose/throat, joints, and lung involvement of AAV. Methods: Thirty-two sets of Birmingham vasculitis activity score (BVAS), PR3-ANCA titers, laboratory marker, and different cytokines were obtained from 17 different patients with AAV. BVAS, PR3-ANCA titers, laboratory marker, and cytokine concentrations were correlated to different organ involvements in active AAV. Results: Among patients with active PR3-AAV (BVAS > 0) and kidney involvement we found significant higher concentrations of chemokine ligand (CCL)-1, interleukin (IL)-6, IL21, IL23, IL-28A, IL33, monocyte chemoattractant protein 2 (MCP2), stem cell factor (SCF), thymic stromal lymphopoietin (TSLP), and thrombopoietin (TPO) compared to patients without PR3-ANCA-associated glomerulonephritis. Patients with ear, nose, and throat involvement expressed higher concentrations of MCP2 and of the (C-X-C motif) ligand-12 (CXCL-12) compared to patients with active AAV and no involvement of these organs. Conclusion: We identified distinct cytokine patterns for renal manifestation and for ear, nose and throat involvement of PR3-AAV. Distinct plasma cytokines might be used as non-invasive biomarkers of organ involvement in AAV.

The Effect of Interleukin-4 and Dexamethasone on RNA-Seq-Based Transcriptomic Profiling of Human Podocytes: A Potential Role in Minimal Change Nephrotic Syndrome

Interleukin-4 (IL-4) expression is implicated in the pathogenesis of nephrotic syndrome (NS). This study aimed to investigate the changes in the transcriptomes of human podocytes induced by IL-4 treatment and to analyze whether these changes could be affected by simultaneous steroid treatment. Three groups of human podocytes were treated with control, IL-4, and IL-4 plus dexamethasone (DEX), respectively. We performed whole-transcriptome sequencing to identify differentially expressed genes (DEGs) between the groups. We investigated relevant biological pathways using Gene Ontology (GO) enrichment analyses. We also attempted to compare and validate the DEGs with the genes listed in PodNet, a literature-based database on mouse podocyte genes. A total of 176 genes were differentially expressed among the three groups. GO analyses showed that pathways related to cytoskeleton organization and cell signaling were significantly enriched. Among them, 24 genes were listed in PodNet, and 12 of them were previously reported to be associated with IL-4-induced changes in human podocytes. Of the 12 genes, the expression levels of BMP4, RARB, and PLCE1 were reversed when podocytes were simultaneously treated with DEX. In conclusion, this study explored changes in the transcriptome profiles of human podocytes treated with IL-4. Few genes were reported in previous studies and were previously validated in experiments with human podocytes. We speculate that IL-4 may exert pathogenic effects on the transcriptome of human podocytes, and a few genes may be involved in the pathogenesis.

Spontaneous remission of minimal change nephrotic syndrome in an elderly man

Minimal change nephrotic syndrome (MCNS) cases achieving spontaneous remission without external factors are rarely reported. We report a case of MCNS that achieved spontaneous remission without external factors that triggered its onset. An 82-year-old male patient was admitted to the hospital for close examination of nephrotic syndrome. Renal biopsy was performed and MCNS was diagnosed. Owing to the patient's age and history of foot and microvascular arteriovenous thrombosis, we did not start immunosuppressive drugs, including steroids, and opted for conservative management. After conservative treatment, proteinuria gradually decreased, and the patient achieved complete remission. Given that the patient had a history of urinary protein and thrombosis, recurrence of MCNS was considered again this time. In addition, the involvement of external factors that trigger the onset of MCNS was not found. In conclusion, in elderly-onset MCNS, clinicians generally hesitate to initiate treatment with an immunosuppressive drug, containing steroids, because of its many complications. Thus, our data provide valuable insight into MCNS.

A global antiB cell strategy combining obinutuzumab and daratumumab in severe pediatric nephrotic syndrome

BACKGROUND

Steroid-sensitive nephrotic syndrome (SSNS) is, in most patients, a chronic disease with 80% experiencing at least one relapse after first flare. B cell depletion using rituximab is effective in preventing relapse in steroid-dependent (SDNS) patients but fails to maintain long-term remission following B cell recovery, possibly due to development of autoreactive long-lived plasma cells. We investigated sequential combination of antiCD20 antibody targeting all B cell subsets, and antiCD38 antibody with high plasma cell cytotoxicity in patients with uncontrolled SDNS after failure of one or several attempts at B cell depletion.

METHODS

Fourteen patients with median disease duration 7.8 years received 1000 mg/1.73 m² obinutuzumab followed by 1000 mg/1.73 m² daratumumab 2 weeks later. Oral immunosuppression was discontinued within 6 weeks, and biological monitoring performed monthly until B cell recovery.

RESULTS

Median age at treatment was 11.0 [IQR 10.4-14.4] years. B cell depletion was achieved in all patients, and B cell reconstitution occurred in all at median 9.5 months after obinutuzumab injection. After median follow-up 20.3 months (IQR 11.5-22.6), 5/14 patients relapsed including 4 within 100 days following B cell repletion. Relapse-free survival was 60% at 24 months from obinutuzumab infusion. Mild infusion reactions were reported in 3/14 patients during obinutuzumab and 4/14 during daratumumab infusions. Mild transient neutropenia (500-1000/mm³) occurred in 2/14 patients. Intravenous immunoglobulins were given to 12/14 patients due to hypogammaglobulinemia. Low IgA and IgM levels were noted in 8 and 14 patients, respectively. No severe infection was reported.

CONCLUSION

Global antiB cell strategy combining obinutuzumab and daratumumab induces prolonged peripheral B cell depletion and remission in children with difficult-to-treat SDNS.

A review of nephrotic syndrome and atopic diseases in children

Pediatric nephrotic syndrome (NS) is a common and recurrent glomerular disease in childhood. Furthermore, 50–70% of children with NS have increased total IgE in peripheral blood and a variety of clinical manifestations of atopic diseases. Hence, NS has many similarities with atopic diseases. However, no study has revealed a clear link between these two diseases. The present review discusses the correlation between pediatric NS and atopic diseases in children from three aspects: pathogenesis, cytokine change, and treatment. There are similar changes in T cells in terms of pathogenesis, with Th1/Th2 dysfunction and Treg cell function downregulation. Cytokine changes are similar and manifest as an increase in Th2 cytokines, TNF-α and TGF-β1, and a decrease in IL-10. Glucocorticoids, immunosuppressants and biological agents are used for the treatment of these two diseases. Therefore, it was speculated that NS and atopic diseases may be the same kind of disease, have a similar pathogenesis, and only exhibit different clinical manifestations due to different affected parts of the disease.

Autoimmunity in Focal Segmental Glomerulosclerosis: A Long-Standing Yet Elusive Association

Focal segmental glomerulosclerosis (FSGS) is a histological term that describes a pathologic renal entity affecting both adults and children, with a wide array of possible underlying etiologies. Podocyte damage with scarring, the hallmark of this condition, leads to altered permeability of the glomerular barrier, which may result in massive proteinuria and relentless renal function deterioration. A definite cause of focal segmental glomerulosclerosis can be confirmed in a minority of cases, while most forms have been traditionally labeled as primary or idiopathic. Despite this definition, increasing evidence indicates that primary forms are a heterogenous group rather than a single disease entity: several circulating factors that may affect glomerular permeability have been proposed as potential culprits, and both humoral and cellular immunity have been implicated in the pathogenesis of the disease. Consistently, immunosuppressive drugs are considered as the cornerstone of treatment for primary focal segmental glomerulosclerosis, but response to these agents and long-term outcomes are highly variable. In this review we provide a summary of historical and recent advances on the pathogenesis of primary focal segmental glomerulosclerosis, focusing on implications for its differential diagnosis and treatment.

Rituximab in adult minimal change disease and focal segmental glomerulosclerosis - What is known and what is still unknown?

Primary forms of minimal change disease and focal segmental glomerulosclerosis are rare podocytopathies and clinically characterized by nephrotic syndrome. Glucocorticoids are the cornerstone of the initial immunosuppressive treatment in these two entities. Especially among adults with minimal change disease or focal segmental glomerulosclerosis, relapses, steroid dependence or resistance are common and necessitate re-initiation of steroids and other immunosuppressants. Effective steroid-sparing therapies and introduction of less toxic immunosuppressive agents are urgently needed to reduce undesirable side effects, in particular for patients whose disease course is complex. Rituximab, a B cell depleting monoclonal antibody, is increasingly used off-label in these circumstances, despite a low level of evidence for adult patients. Hence, critical questions concerning drug-safety, long-term efficacy and the optimal regimen for rituximab-treatment remain unanswered. Evidence in the form of large, multicenter studies and randomized controlled trials are urgently needed to overcome these limitations.

Emerging drugs for treatment of focal segmental glomerulosclerosis

BACKGROUND

Glomerulosclerosis represents the final stage of glomerular injury during the course of kidney disease and can result from a primary disturbance in disorders like focal segmental glomerulosclerosis or a secondary response to tubulointerstitial disease. Overall, primary focal glomerulosclerosis (FSGS), the focus of this review, accounts for 10-20% of patients of all ages who progress to end stage kidney disease. There are no FDA approved therapeutic options that effectively prevent or delay the onset of kidney failure.

AREAS COVERED

Current immunosuppressive therapy and conservative management including inhibitors of the renin-angiotensin-aldosterone axis and sodium-glucose cotransporter are reviewed. FSGS is now recognized to represent a heterogeneous entity with multiple underlying disease mechanisms. Therefore, novel approaches targeting the podocyte cytoskeleton, immunological, inflammatory, hemodynamic and metabolic pathways are highlighted.

EXPERT OPINION

A number of factors are driving the development of drugs to treat focal segmental glomerulosclerosis in particular and glomerulosclerosis in general including growing awareness of the burden of chronic kidney disease, improved scientific understanding of the mechanism of injury, and the development of noninvasive profiles to identify subgroups of patients with discrete mechanisms of glomerular injury.

Effects of tristetraprolin on doxorubicin (adriamycin)-induced experimental kidney injury through inhibiting IL-13/STAT6 signal pathway

To study the effects of Tristetraprolin (TTP) on Doxorubicin (DOX)-induced experimental kidney injury (KI). DOX was used to induce kidney injury in Balb/c male mice (in vivo) and in human kidney proximal tubular epithelial cell line (HK-2) and normal rat kidney epithelial cell line (NRK-52E) (in vitro). Body weight of experimental mice were recorded daily. Histological changes were observed using hematoxylin-eosin (HE) staining, and levels of blood urea nitrogen, serum creatinine and serum cystatin C in KI mice, and MDA, LDH and SOD in cells were detected using the corresponding kits. Meanwhile, the 2, 7-dichlorodihydrofluorescein diacetate (DCF-DA) fluorescent staining was used to assess intracellular levels of reactive oxygen species (ROS). TTP and Kim-1 expressions were measured by immunohistochemistry and western blot. The TNF-α, IL-1β and IL-6 levels were evaluated by ELISA. Expressions of IL-13, STAT6, p-STAT6, Bcl-2, Bax, cleaved-caspase3 were detected using western blot, respectively. Cell Counting Kit-8 (CCK-8) was conducted for analyzing cell viability, and cells apoptosis were assessed by DAPI staining and flow cytometry. DOX treatment decreased body weight and aggravated renal injury without changes in water and food intake. DOX significantly reduced TTP expression, stimulated IL-13/STAT6 pathway and elevated the levels of several factors related to renal injury, including inflammatory response, oxidative stress and cell apoptosis, which were significantly restored by the treatment of overexpression TTP in vitro. Overexpression of TTP significantly reduces DOX-induced adverse outcomes so as to prevent renal injury. Inhibition of IL-13/STAT6 pathway may be the functional mechanism under TTP in experimental KI.

Management and treatment of glomerular diseases (part 2): conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

In November 2017, the Kidney Disease: Improving Global Outcomes (KDIGO) initiative brought a diverse panel of experts in glomerular diseases together to discuss the 2012 KDIGO glomerulonephritis guideline in the context of new developments and insights that had occurred over the years since its publication. During this KDIGO Controversies Conference on Glomerular Diseases, the group examined data on disease pathogenesis, biomarkers, and treatments to identify areas of consensus and areas of controversy. This report summarizes the discussions on primary podocytopathies, lupus nephritis, anti-neutrophil cytoplasmic antibody-associated nephritis, complement-mediated kidney diseases, and monoclonal gammopathies of renal significance.

Role of Podocyte Injury in Glomerulosclerosis

Finding new therapeutic targets of glomerulosclerosis treatment is an ongoing quest. Due to a living environment of various stresses and pathological stimuli, podocytes are prone to injuries; moreover, as a cell without proliferative potential, loss of podocytes is vital in the pathogenesis of glomerulosclerosis. Thus, sufficient understanding of factors and underlying mechanisms of podocyte injury facilitates the advancement of treating and prevention of glomerulosclerosis. The clinical symptom of podocyte injury is proteinuria, sometimes with loss of kidney functions progressing to glomerulosclerosis. Injury-induced changes in podocyte physiology and function are actually not a simple passive process, but a complex interaction of proteins that comprise the anatomical structure of podocytes at molecular levels. This chapter lists several aspects of podocyte injuries along with potential mechanisms, including glucose and lipid metabolism disorder, hypertension, RAS activation, micro-inflammation, immune disorder, and other factors. These aspects are not technically separated items, but intertwined with each other in the pathogenesis of podocyte injuries.

Levamisole in Children with Idiopathic Nephrotic Syndrome: Clinical Efficacy and Pathophysiological Aspects

Steroid sensitive nephrotic syndrome is one of the most common pediatric glomerular diseases. Unfortunately, it follows a relapsing and remitting course in the majority of cases, with 50% of all cases relapsing once or even more often. Most children with idiopathic nephrotic syndrome respond initially to steroid therapy, nevertheless repeated courses for patients with relapses induce significant steroid toxicity. Patients with frequent relapses or steroid dependency thus require alternative treatment, such as cyclophosphamide, cyclosporine, tacrolimus, mycophenolate mofetil, levamisole, or rituximab. To reduce the relapse rate, several drugs have been used. Among these, levamisole has been considered the least toxic and least expensive therapy. Several randomized controlled trials (RCT) showed that levamisole is effective in reducing the relapse risk in steroid sensitive forms of nephrotic syndrome with a low frequency of side effects. Levamisole is a synthetic imidazothiazole derivative with immune-modulatory properties. In this article, we review recent data from randomized trials and observational studies to assess the efficacy of levamisole in frequently relapsing nephrotic syndrome and steroid-dependent nephrotic syndrome.

Outcomes of Older Patients (≥60 years) with New-Onset Idiopathic Nephrotic Syndrome Receiving Immunosuppressive Regimen: A Multicentre Study of 116 Patients

Because of its rarity, renal presentation and outcomes of idiopathic nephrotic syndrome (INS; minimal changes disease or focal and segmental glomerulosclerosis) has poorly been described in elderly patients, precluding an individualized therapy procedure. Whether immunosuppressive regimens formerly designed in children and young adults are safe and efficient in elderly remains elusive. In a large multicentric retrospective study that included 116 patients with INS and onset ≥ 60 years of age, we showed that cumulative incidence of renal response was 95% after frontline therapy, with an age-dependent median time-to-response (60 days before 70 years of age at the onset vs. 120 days after; p = 0.03). Cumulative incidence of relapse was 90% at 7 years, with relapse occurring continuously over time. After a median follow-up of 34 months (IQR (12; 57)), 7 patients had died (6%) and 5 reached end-stage renal disease. Complications were highly prevalent: diabetes mellitus (23.3%), hypertension (24.1%), infection requiring hospitalization (21.6%) and acute kidney injury (9.5%). Thus, in older patients with INS and receiving steroids, renal response is delayed and relapse is the rule. Alternative immunosuppressive regimens, including B-cells depleting agents as frontline therapy, should be tested in this subset of patients to improve the mid- to long-term outcomes.

B cell phenotype in pediatric idiopathic nephrotic syndrome

BACKGROUND

A pathogenic role of B cells in non-genetic nephrotic syndrome has been suggested by the efficacy of rituximab, a B cell depleting antibody, in maintaining a prolonged remission. However, little information is available on B cell homeostasis in nephrotic syndrome patients.

METHODS

We retrospectively analyzed by flow cytometry the distribution of different B cell subpopulations in 107 steroid-sensitive and in 6 genetic steroid-resistant nephrotic syndrome pediatric patients, compared with age- and sex-matched controls.

RESULTS

Fifty-one steroid-sensitive patients at disease onset, before starting immunosuppression, presented significantly increased levels of total, transitional, memory, and switched memory B cells compared to controls. Oral immunosuppression strongly affected transitional and mature B cell levels in 27 patients in relapse and also in 29 patients in remission, whereas memory B cells were significantly higher compared to controls during relapse, despite the immunosuppressive treatment, and were normalized only in patients in remission. Children with genetic forms of steroid-resistant nephrotic syndrome presented no differences in B cell profile from controls.

CONCLUSIONS

Our study indicates that memory B cells, more than other B cell subsets, are increased and appear to be pathogenically relevant in steroid-sensitive nephrotic syndrome pediatric patients.

Rituximab modulates T- and B-lymphocyte subsets and urinary CD80 excretion in patients with steroid-dependent nephrotic syndrome

BACKGROUND

Rituximab, a monoclonal antibody targeting B lymphocytes, effectively sustains remission in steroid-dependent nephrotic syndrome (SDNS). We studied its effects on lymphocyte subsets and urinary CD80 excretion (uCD80) in patients with SDNS.

METHODS

Blood and urine samples were collected from 18 SDNS patients before rituximab, and after 1 month and 1 year or at first relapse. T and B lymphocytes and uCD80 were determined by flow cytometry and ELISA, respectively.

RESULTS

Treatment was associated with reduction in counts of Th17, Th2, and memory T cells, and increased T-regulatory (Treg) cells. The Th17/Treg ratio declined from baseline (median 0.6) to 1 month (0.2, P = 0.006) and increased during relapse (0.3, P = 0.016). Ratios of Th1/Th2 cells at baseline, 1 month after rituximab, and during relapse were 7.7, 14.0 (P = 0.0102), and 8.7, respectively. uCD80 decreased 1 month following rituximab (45.5 vs. 23.0 ng/g creatinine; P = 0.0039). B lymphocytes recovered earlier in relapsers (60.0 vs.183.0 days; P < 0.001). Memory B cells were higher during relapse than remission (29.7 vs.18.0 cells/µL; P = 0.029).

CONCLUSION

Rituximab-induced sustained remission and B-cell depletion was associated with reduced numbers of Th17 and Th2 lymphocytes, and increased Treg cells; these changes reversed during relapses. Recovery of B cells and memory B cells predicted the occurrence of a relapse.

[Current insights about recurrence of glomerular diseases after renal transplantation]

Recurrence of glomerular disease after renal transplantation is a frequent cause of graft loss. Incidence, risk factors and outcome of recurrence are widely due to the underlying glomerular disease. Graft biopsy analysis is required to confirm the definitive diagnosis of recurrence and to start an appropriate therapy that, in some cases, remains challenging to prevent graft failure. Increased use of protocol biopsy and recent advances in our understanding of the pathogenesis of some glomerular diseases with the identification of some relevant biomarkers provide a unique opportunity to initiate kidney-protective therapy at early stages of recurrence on the graft. This review summarizes our current knowledge on the management of many recurrent primary and secondary glomerulonephritis after kidney transplantation.

Understanding Podocyte Biology to Develop Novel Kidney Therapeutics

Over the past two decades it has become increasing clear that injury and loss of podocytes is an early and common clinical observation presented in many forms of glomerulopathy and chronic kidney disease. Identification of disease-causing monogenic mutations in numerous podocyte-expressed genes as well as studies conducted using preclinical animal models have shown that the podocyte plays a central role in establishing kidney dysfunction. In this review, we summarize current knowledge regarding the potential for podocyte-targeted therapies and give our view on how a deeper understanding of the molecular makeup of the podocyte will enable future therapeutic interventions. Specifically, we recount some of the currently described podocentric strategies for therapy and summarize the status and evolution of various model systems used to facilitate our understanding of the molecular and functional underpinnings of podocyte biology.