Treatment of focal segmental glomerulosclerosis

Control of Podocyte and Glomerular Capillary Wall Structure and Elasticity by WNK1 Kinase

Cytoskeletal structure and its regulation are essential for maintenance of the differentiated state of specific types of cells and their adaptation to physiologic and pathophysiologic conditions. Renal glomerular capillaries, composed of podocytes, endothelial cells, and the glomerular basement membrane, have distinct structural and biophysical properties and are the site of injury in many glomerular diseases. Calcineurin inhibitors, immunosuppressant drugs used for organ transplantation and auto-immune diseases, can protect podocytes and glomerular capillaries from injury by preserving podocyte cytoskeletal structure. These drugs cause complications including hypertension and hyperkalemia which are mediated by WNK (With No Lysine) kinases as well as vasculopathy with glomerulopathy. WNK kinases and their target kinases oxidative stress-responsive kinase 1 (OSR1) and SPS1-related proline/alanine-rich kinase (SPAK) have fundamental roles in angiogenesis and are activated by calcineurin inhibitors, but the actions of these agents on kidney vasculature, and glomerular capillaries are not fully understood. We investigated WNK1 expression in cultured podocytes and isolated mouse glomerular capillaries to determine if WNK1 contributes to calcineurin inhibitor-induced preservation of podocyte and glomerular structure. WNK1 and OSR1/SPAK are expressed in podocytes, and in a pattern similar to podocyte synaptopodin in glomerular capillaries. Calcineurin inhibitors increased active OSR1/SPAK in glomerular capillaries, the Young’s modulus (E) of glomeruli, and the F/G actin ratio, effects all blocked by WNK inhibition. In glomeruli, WNK inhibition caused reduced and irregular synaptopodin-staining, abnormal capillary and foot process structures, and increased deformability. In cultured podocytes, FK506 activated OSR1/SPAK, increased lamellipodia, accelerated cell migration, and promoted traction force. These actions of FK506 were reduced by depletion of WNK1. Collectively, these results demonstrate the importance of WNK1 in regulation of the podocyte actin cytoskeleton, biophysical properties of glomerular capillaries, and slit diaphragm structure, all of which are essential to normal kidney function.

APOL1 risk variants affect podocyte lipid homeostasis and energy production in focal segmental glomerulosclerosis

Lipotoxicity was recently reported in several forms of kidney disease, including focal segmental glomerulosclerosis (FSGS). Susceptibility to FSGS in African Americans is associated with the presence of genetic variants of the Apolipoprotein L1 gene (APOL1) named G1 and G2. If and how endogenous APOL1 may alter mitochondrial function by the modifying cellular lipid metabolism is unknown. Using transgenic mice expressing the APOL1 variants (G0, G1 or G2) under endogenous promoter, we show that APOL1 risk variant expression in transgenic mice does not impair kidney function at baseline. However, APOL1 G1 expression worsens proteinuria and kidney function in mice characterized by the podocyte inducible expression of nuclear factor of activated T-cells (NFAT), which we have found to cause FSGS. APOL1 G1 expression in this FSGS-model also results in increased triglyceride and cholesterol ester contents in kidney cortices, where lipid accumulation correlated with loss of renal function. In vitro, we show that the expression of endogenous APOL1 G1/G2 in human urinary podocytes is associated with increased cellular triglyceride content and is accompanied by mitochondrial dysfunction in the presence of compensatory oxidative phosphorylation (OXPHOS) complexes elevation. Our findings indicate that APOL1 risk variant expression increases the susceptibility to lipid-dependent podocyte injury, ultimately leading to mitochondrial dysfunction.

Mild electrical stimulation with heat shock attenuates renal pathology in adriamycin-induced nephrotic syndrome mouse model

Nephrotic syndrome (NS) is a renal disorder that is characterized by massive proteinuria, hypoalbuminemia and edema. One of the main causes of NS is focal segmental glomerulosclerosis (FSGS), which has extremely poor prognosis. Although steroids and immunosuppressants are the first line of treatment, some FSGS cases are refractory, prompting the need to find new therapeutic strategies. We have previously demonstrated that an optimized combination treatment of mild electrical stimulation (MES) and heat shock (HS) has several biological benefits including the amelioration of the pathologies of the genetic renal disorder Alport syndrome. Here, we investigated the effect of MES + HS on adriamycin (ADR)-induced NS mouse model. MES + HS suppressed proteinuria and glomerulosclerosis induced by ADR. The expressions of pro-inflammatory cytokines and pro-fibrotic genes were also significantly downregulated by MES + HS. MES + HS decreased the expression level of cleaved caspase-3 and the number of TUNEL-positive cells, indicating that MES + HS exerted anti-apoptotic effect. Moreover, MES + HS activated the Akt signaling and induced the phosphorylation and inhibition of the apoptotic molecule BAD. In in vitro experiment, the Akt inhibitor abolished the MES + HS-induced Akt-BAD signaling and anti-apoptotic effect in ADR-treated cells. Collectively, our study suggested that MES + HS modulates ADR-induced pathologies and has renoprotective effect against ADR-induced NS via regulation of Akt-BAD axis.

Clinical and pathological features of idiopathic membranous nephropathy with focal segmental sclerosis

Background

The goal of this study was to investigate the clinical and pathological features and prognosis of idiopathic membranous nephropathy (IMN) with focal segmental lesions.

Methods

In our hospital, 305 patients with nephrotic syndrome confirmed as IMN by renal biopsy were divided into a non-focal segmental lesion group (FSGS- group) and a focal segmental glomerulosclerosis (FSGS) group (FSGS+ group) and retrospectively analyzed. In all, 180 patients were followed for periods ranging from 6 months to 2 years. The general clinicopathological data of both groups were compared, and the effects of different treatment schemes on the prognosis of both groups were observed.

Results

The FSGS+ group had a longer disease course, higher blood pressure levels, and higher serum creatinine and β₂-microglobulin levels than did the FSGS- group (all P < 0.05). Pathologically, the FSGS+ group had increased glomerular sclerosis, glomerular mesangial hyperplasia, and acute and chronic tubular lesion rates (all P < 0.05). The remission rate was lower in the FSGS+ group than in the FSGS- group (64.7% vs 82.2%) and, among patients in the FSGS+ group, was lower in patients treated with calmodulin inhibitors than in those treated with cyclophosphamide (P < 0.01). Survival analysis showed that the FSGS+ group had a poor prognosis (χ² = 4.377, P = 0.036), and risk factor analysis suggested that age at renal biopsy (P = 0.006), 24-h urinary protein quantity (P = 0.01), chronic tubulointerstitial lesions (P = 0.055), and FSGS lesions (P = 0.062) were risk factors for worsening renal condition; furthermore, 24-h urinary protein quantity was an independent risk factor for worsening renal condition.

Conclusions

Membranous nephropathy with FSGS is a risk factor, but not an independent risk factor, for IMN. Patients with membranous nephropathy with FSGS often present hypertension and tubule injury. The nonselective drug cyclophosphamide is preferred, and calcineurin inhibitors should be used with caution.

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.”

Clinical study on Yishen Qufeng Shengshi Recipe () for glomerular proteinuria patients: A randomized controlled trial

OBJECTIVE

To explore the therapeutic effect of Yishen Qufeng Shengshi Recipe (, YQSR) in patients with glomerular proteinuria METHODS: A total of 145 patients with glomerular proteinuria were selected and randomly assigned to the treatment group (108 cases) and the control group (37 cases) according to a random number table in a ratio of 3:1. All patients received conventional and symptomatic treatment. In addition, patients in the treatment and control groups were given YQSR (200 mL, twice per day, orally) and losartan (50 mg/d orally), respectively for 6 months. The 24-h urine protein quantity, blood urea nitrogen, and serum creatinine in the two groups were measured at multiple time points before and after treatment.

RESULTS

At the end of the study, 5 cases were lost to follow-up in the treatment group and 1 in the control group. Finally, the statistical data included 103 cases in the treatment group and 36 cases in the control group. The total effectiveness after 2, 4, and 6 months was 81.6% (84/103), 87.4% (90/103), and 92.2% (95/103), respectively, in the treatment group and 47.2% (17/36), 55.6% (20/36), and 61.1% (22/36), respectively, in the control group, with significant difference between the two groups (P<0.01 at all observation points). In the treatment group, the curative effect after 6 months was better than that after 2 months (P<0.05). The 24-h urine protein quantity was significantly lower in the treatment group at 3, 4, 5, and 6 months than that in the control group (P<0.05 or P<0.01, respectively) CONCLUSION: YQSR could significantly reduce the amount of glomerular proteinuria in the early stage.

Guidelines on the Use of Therapeutic Apheresis in Clinical Practice-Evidence-Based Approach from the Writing Committee of the American Society for Apheresis: The Seventh Special Issue

The American Society for Apheresis (ASFA) Journal of Clinical Apheresis (JCA) Special Issue Writing Committee is charged with reviewing, updating, and categorizing indications for the evidence-based use of therapeutic apheresis in human disease. Since the 2007 JCA Special Issue (Fourth Edition), the Committee has incorporated systematic review and evidence-based approaches in the grading and categorization of apheresis indications. This Seventh Edition of the JCA Special Issue continues to maintain this methodology and rigor to make recommendations on the use of apheresis in a wide variety of diseases/conditions. The JCA Seventh Edition, like its predecessor, has consistently applied the category and grading system definitions in the fact sheets. The general layout and concept of a fact sheet that was used since the fourth edition has largely been maintained in this edition. Each fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis in a specific disease entity. The Seventh Edition discusses 87 fact sheets (14 new fact sheets since the Sixth Edition) for therapeutic apheresis diseases and medical conditions, with 179 indications, which are separately graded and categorized within the listed fact sheets. Several diseases that are Category IV which have been described in detail in previous editions and do not have significant new evidence since the last publication are summarized in a separate table. The Seventh Edition of the JCA Special Issue serves as a key resource that guides the utilization of therapeutic apheresis in the treatment of human disease. J. Clin. Apheresis 31:149-162, 2016. © 2016 Wiley Periodicals, Inc.

Cyclosporine A protects podocytes by regulating WAVE1 phosphorylation

Accumulating evidence suggests that podocytes are direct targets of many classic antiproteinuric drugs. The immunosuppressive drug cyclosporine A (CsA), which is a calcineurin inhibitor, is used to treat proteinuric kidney diseases. One novel mechanism by which CsA reduces proteinuria is by directly stabilizing the podocyte cytoskeleton. Previous studies showed that calcineurin can directly regulate WAVE1 within mouse striatal slices. In this study, WAVE1 was expressed in podocytes and was localized in the podocyte cell bodies and foot processes (FPs). WAVE1 expression increased in both in vivo and in vitro models of puromycin aminonucleoside (PAN)-induced podocyte injury. CsA restored WAVE1 expression and also partially rescued the disordered F-actin arrangement after PAN injury. Co-immunoprecipitation assays showed that calcineurin directly interacted with WAVE1 and regulated WAVE1 phosphorylation in podocytes. Synaptopodin is a well-characterized target of CsA. WAVE1 overexpression and synaptopodin knockdown experiments directly demonstrated that WAVE1 expression is not dependent on synaptopodin expression, and vice versa. Overexpression of WAVE1 using a WAVE1 plasmid disrupted F-actin structure and promoted podocyte migration compared with the empty vector group. Therefore, WAVE1 may be a novel molecular target for the maintenance of podocyte FPs and for antiproteinuric treatment in the future.

Scavengers of reactive oxygen species, paracalcitol, RhoA, and Rac-1 inhibitors and tacrolimus inhibit angiotensin II-induced actions on glomerular permeability

Systemic infusions of ANG II rapidly induce large, dynamic increases in the permeability of the glomerular filtration barrier (GFB) in rats. After binding to its receptor(s), ANG II generates reactive oxygen species (ROS) and produces Ca2+ influx into cells, leading to activation of a plethora of signaling cascades, including, e.g., calcineurin and small GTPases, such as Rac-1 and RhoA. In the present study we sought to interact with some of these cascades to test potential novel antiproteinuric agents. In anesthetized Wistar rats, the left urether was cannulated for urine collection, and blood access was achieved. Rats were infused with ANG II (16 ng·kg−1·min−1) alone, or together with the ROS scavengers tempol or dimethylthiourea (DMTU) or the D-vitamin analog paracalcitol, the RhoA-kinase inhibitor Y-27632, the Rac-1 inhibitor NSC-23766, or the calcineurin inhibitor tacrolimus. FITC-Ficoll-70/400 (mol.radius 10–80 Å) and 51Cr-EDTA were infused throughout the experiment. Plasma and urine samples were taken during baseline and at 5 and 15 min after the start of the infusions and analyzed by high-performance size-exclusion chromatography for determination of glomerular sieving coefficients (θ) for Ficoll10–80Å. ANG II infusion into rats caused marked increases in glomerular permeability to large Ficoll molecules (Ficoll50–80Å), which were abrogated by the ROS scavenger tempol and partly by DMTU. Paracalcitol, RhoA, and Rac-1 inhibition, and, to some extent tacrolimus, but not prostacyclin, could also inhibit the glomerular permeability actions of ANG II. Our data suggest that cellular ROS generation and active Ca2+ signaling are involved in ANG II-induced increases in glomerular permeability.

Combination of pulse methylprednisolone infusions with cyclosporine-based immunosuppression is safe and effective to treat recurrent focal segmental glomerulosclerosis after pediatric kidney transplantation

BACKGROUND

Recurrence of focal segmental glomerulosclerosis (FSGS) in pediatric kidney allografts is associated with poor graft survival. Several therapeutic regimens have been proposed, with conflicting results.

METHODS

Ten pediatric patients with recurrent FSGS after kidney transplantation were treated with a protocol of methylprednisolone (MP) infusions in combination with cyclosporine (CsA)-based immunosuppression. The patients received a drug regimen with infusions of 20 mg/kg MP on three consecutive days at week 1, week 3, and week 5, and then monthly until six months after transplantation. If a complete or partial remission (PR) was obtained, MP pulse continued every three months until 24 months after transplantation. The CsA dose was adjusted according to AUC0-4.

RESULTS

Seven of 10 patients (70%) achieved complete remission (CR) with stable renal function within 18 months of beginning of treatment. One of two patients with PR entered CR 3.5 yr after transplantation. One patient lost her graft due to recurrence four months after transplantation. After observation for 26-119 months, seven patients maintained remission with normal glomerular filtration rate. Few major side effects were observed in association with the high-dose MP infusion therapy.

CONCLUSIONS

MP infusion therapy in combination with CsA-based immunosuppression could be safe and effective in treating recurrent FSGS after kidney transplantation.

Is There a Role for Mammalian Target of Rapamycin Inhibition in Renal Failure due to Mesangioproliferative Nephrotic Syndrome?

Primary glomerulonephritis stands as the third most important cause of end-stage renal disease, suggesting that appropriate treatment may not be as effective as intended to be. Moreover, proteinuria, the hallmark of glomerular damage and a prognostic marker of renal damage progression, is frequently resistant to thorough control. In addition, proteinuria may be the common end pathway in which different pathogenetic mechanisms may converge. This explains why immunosuppressive and nonimmunosuppressive approaches are partly not sufficient to halt disease progression. One of the commonest causes of primary glomerulonephritis is mesangioproliferative glomerulonephritis. Among the triggered intracellular pathways involved in mesangial cell proliferation, the mammalian target of rapamycin (mTOR) plays a critical role in cell growth, in turn regulated by many cytokines, disbalanced by the altered glomerulopathy itself. However, when inhibition of mTOR was studied in rodents and in humans with primary glomerulonephritis the results were contradictory. In light of these controversial data, we propose an explanation for these results, to dilucidate under which circumstances mTOR inhibition should be considered to treat glomerular proteinuria and finally to propose mTOR inhibitors to be prospectively assessed in clinical trials in patients with primary mesangioproliferative glomerulonephritis, for which a satisfactory standard immunosuppressive regimen is still pending.

Early treatment with everolimus exerts nephroprotective effect in rats with adriamycin-induced nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) is a clinical state characterized by massive proteinuria and excessive fluid retention. The effects of early versus late treatment with low or high doses of oral everolimus, a mammalian target of rapamycin inhibitor, on proteinuria in NS have not been previously described.

METHODS

The effects of early treatment (2 days prior to NS induction) versus late treatment (beginning 2 weeks following the establishment of NS) with a low (20 mg/L) or high (100 mg/L) dose of everolimus for 5-7 weeks on proteinuria and nephrin/podocin abundance were assessed in male adult SD rats with adriamycin-induced NS.

RESULTS

Adriamycin caused a significant increase in daily and cumulative proteinuria throughout the experimental period. Early, and to a lesser extent late treatment, with a low dose of everolimus, significantly decreased both daily and cumulative proteinuria and improved renal function. The anti-proteinuric effects of low-dose everolimus were associated with restoration of the disruptive glomerular nephrin/podocin abundance. In contrast, administration of a high dose of everolimus resulted in a decrease in proteinuria in NS rats, subsequently to deterioration of renal function.

CONCLUSIONS

Early, and to a lesser extent late treatment, with a low but not a high dose of everolimus is effective in reducing proteinuria in nephrotic rats. The mechanism may be via nephrin/podocin protection.

The podocyte as a direct target of immunosuppressive agents

Podocytes play a key role in maintaining the blood-urine barrier for high-molecular-weight proteins. They are considered to be terminally differentiated, and podocyte loss cannot be compensated by regenerative proliferation. Various diseases leading to podocyte damage and loss result in proteinuria and cause nephrotic syndrome. Therefore, direct therapeutical strategies to protect podocytes in disease situations are a logical concept to prevent disease or to delay disease progression. Acquired podocytopathies like idiopathic focal segmental glomerulosclerosis and minimal change disease are historically considered as immunological diseases. Therefore, immunosuppressive agents such as steroids and calcineurin inhibitors are the commonly used treatment strategies. However, the causative disease mechanisms behind these treatment strategies remain elusive. Recent evidence shows that immunosuppressive agents, in addition to the effect on the immune system, directly influence the unique structure and function of podocytes. In this context, the actin cytoskeleton of the podocyte and cytokines such as vascular endothelial growth factor play a pivotal role. In this review, we summarize the direct effects on podocytes obtained in vivo and in vitro after treatment with calcineurin inhibitors, mTOR inhibitors and glucocorticoids. These direct effects could play a key role in the treatment concepts of podocytopathies with an important impact on the long-term renal function in patients with pharmacological immunosuppression.

Guidelines on the use of therapeutic apheresis in clinical practice--evidence-based approach from the Apheresis Applications Committee of the American Society for Apheresis

The American Society for Apheresis (ASFA) Apheresis Applications Committee is charged with a review and categorization of indications for therapeutic apheresis. Beginning with the 2007 ASFA Special Issue (fourth edition), the subcommittee has incorporated systematic review and evidence-based approach in the grading and categorization of indications. This Fifth ASFA Special Issue has further improved the process of using evidence-based medicine in the recommendations by refining the category definitions and by adding a grade of recommendation based on widely accepted GRADE system. The concept of a fact sheet was introduced in the Fourth edition and is only slightly modified in this current edition. The fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis. The article consists of 59 fact sheets devoted to each disease entity currently categorized by the ASFA as category I through III. Category IV indications are also listed.

Specialized roles for cysteine cathepsins in health and disease

Cathepsins were originally identified as proteases that act in the lysosome. Recent work has uncovered nontraditional roles for cathepsins in the extracellular space as well as in the cytosol and nucleus. There is strong evidence that subspecialized and compartmentalized cathepsins participate in many physiologic and pathophysiologic cellular processes, in which they can act as both digestive and regulatory proteases. In this review, we discuss the transcriptional and translational control of cathepsin expression, the regulation of intracellular sorting of cathepsins, and the structural basis of cathepsin activation and inhibition. In particular, we highlight the emerging roles of various cathepsin forms in disease, particularly those of the cardiac and renal systems.

Activation of NFAT signaling in podocytes causes glomerulosclerosis

Mutant forms of TRPC6 can activate NFAT-dependent transcription in vitro via calcium influx and activation of calcineurin. The same TRPC6 mutants can cause FSGS, but whether this involves an NFAT-dependent mechanism is unknown. Here, we generated mice that allow conditional induction of NFATc1. Mice with NFAT activation in nascent podocytes in utero developed proteinuria and glomerulosclerosis postnatally, resembling FSGS. NFAT activation in adult mice also caused progressive proteinuria and FSGS. Ultrastructural studies revealed podocyte foot process effacement and deposition of extracellular matrix. NFAT activation did not initially affect expression of podocin, synaptopodin, and nephrin but reduced their expression as glomerular injury progressed. In contrast, we observed upregulation of Wnt6 and Fzd9 in the mutant glomeruli before the onset of significant proteinuria, suggesting a potential role for Wnt signaling in the pathogenesis of NFAT-induced podocyte injury and FSGS. These results provide in vivo evidence for the involvement of NFAT signaling in podocytes, proteinuria, and glomerulosclerosis. Furthermore, this study suggests that NFAT activation may be a key intermediate step in the pathogenesis of mutant TRPC6-mediated FSGS and that suppression of NFAT activity may contribute to the antiproteinuric effects of calcineurin inhibitors.

Enzymatic disease of the podocyte

Proteinuria is an early sign of kidney disease and has gained increasing attention over the past decade because of its close association with cardio-vascular and renal morbidity and mortality. Podocytes have emerged as the cell type that is critical in maintaining proper functioning of the kidney filter. A few genes have been identified that explain genetic glomerular failure and recent insights shed light on the pathogenesis of acquired proteinuric diseases. This review highlights the unique role of the cysteine protease cathepsin L as a regulatory rather than a digestive protease and its action on podocyte structure and function. We provide arguments why many glomerular diseases can be regarded as podocyte enzymatic disorders.

Proteinuria: an enzymatic disease of the podocyte?

Proteinuria is a major health-care problem that affects several hundred million people worldwide. Proteinuria is a cardinal sign and a prognostic marker of kidney disease, and also an independent risk factor for cardiovascular morbidity and mortality. Microalbuminuria is the earliest cue of renal complications of diabetes, obesity, and the metabolic syndrome. It can often progress to overt proteinuria that in 10-50% of patients is associated with the development of chronic kidney disease, ultimately requiring dialysis or transplantation. Therefore, reduction or prevention of proteinuria is highly desirable. Here we review recent novel insights into the pathogenesis and treatment of proteinuria, with a special emphasis on the emerging concept that proteinuria can result from enzymatic cleavage of essential regulators of podocyte actin dynamics by cytosolic cathepsin L (CatL), resulting in a motile podocyte phenotype. Finally, we describe signaling pathways controlling the podocyte actin cytoskeleton and motility and how these pathways can be manipulated for therapeutic benefit.

Molecular genetic analysis of podocyte genes in focal segmental glomerulosclerosis--a review

This review deals with podocyte proteins that play a significant role in the structure and function of the glomerular filter. Genetic linkage studies has identified several genes involved in the development of nephrotic syndrome and contributed to the understanding of the pathophysiology of glomerular proteinuria and/or focal segmental glomerulosclerosis. Here, we describe already well-characterized genetic diseases due to mutations in nephrin, podocin, CD2AP, alpha-actinin-4, WT1, and laminin beta2 chain, as well as more recently identified genetic abnormalities in TRPC6, phospholipase C epsilon, and the proteins encoded by the mitochondrial genome. In addition, the role of the proteins which have shown to be important for the structure and functions by gene knockout studies in mice, are also discussed. Furthermore, some rare syndromes with glomerular involvement, in which molecular defects have been recently identified, are briefly described. In summary, this review updates the current knowledge of genetic causes of congenital and childhood nephrotic syndrome and provides new insights into mechanisms of glomerular dysfunction.

An update on the treatment options for focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is not a disease but a lesion initially affecting the podocyte. Various factors may induce 'secondary' FSGS, including defects in molecules that contribute to the podocyte slit diaphragm permselectivity to albumin. They do not represent indications for immunosuppression and require symptomatic treatment only, comprising angiotensin 2 and endothelin antagonists. Primary (idiopathic) FSGS is possibly but not certainly of immunologic origin, owing to an elusive glomerular permeability factor (GPF), explaining relapse on a renal transplant and justifying an immunosuppressive treatment. The best prognostic feature of primary nephrotic FSGS is its response to corticosteroids. Alkylating agents are mostly ineffective in steroid-resistant forms. An association of corticosteroids and cyclosporine A (CsA) remains the mainstay of treatment, with a good tolerability when CsA dosage is low. A definite advantage of tacrolimus on CsA has not yet been established. Sirolimus appears ineffective and potentially harmful. Azathioprine is not indicated. A number of mostly uncontrolled trials indicate that mycophenolate mofetil might find an adjunctive place in the treatment. Plasmapheresis is of no avail outside the special case of relapse in a transplanted kidney. Immunoabsorption of the GPF has not led to practical treatment options. Anecdotal reports on rituximab are as yet too few to determine whether this monoclonal anti-CD20 antibody will find a place in the treatment of primary FSGS.

Complete remission of nephrotic syndrome in an infant with focal segmental glomerulosclerosis: is it renin-angiotensin blockade?

Nephrotic syndrome presenting in the first year of life is often challenging, with substantial risk of progression to end-stage renal disease (ESRD). Focal segmental glomerulosclerosis (FSGS) comprises up to 20% of biopsy-proven glomerular disease in children and adults. We report on a 9-month-old infant who presented with nephrotic syndrome, hypertension and progressive deterioration of renal function due to FSGS. As immunosuppressive agents are often unsuccessful in treating this condition, we adopted renoprotection as the mainstay treatment for this patient, through rigorous control of blood pressure and proteinuria with a multi-drug regimen including renin-angiotensin axis blockade. Initially, there was partial improvement, with a gradual decline in proteinuria and a concomitant rise in the glomerular filtration rate, before the disease eventually passed into complete clinical and laboratory remission. We speculate that infants with steroid-resistant nephrotic syndrome due to FSGS may benefit from tight control of hypertension, mainly though early blockade of the renin-angiotensin axis. We believe that its renoprotecive mechanism counteracts the deleterious effects of both hypertension and proteinuria, thereby not only preventing progressive renal disease, but even paving the way for a remission, as in our patient. To the best of our knowledge, this is the first report of an infant with nephrotic syndrome (NS) due to FSGS that passed into complete remission while the patient was on renoprotective measures including the use of angiotensin-converting enzyme inhibitors (ACEis).

The actin cytoskeleton of kidney podocytes is a direct target of the antiproteinuric effect of cyclosporine A

The immunosuppressive action of the calcineurin inhibitor cyclosporine A (CsA) stems from the inhibition of nuclear factor of activated T cells (NFAT) signaling in T cells. CsA is also used for the treatment of proteinuric kidney diseases. As it stands, the antiproteinuric effect of CsA is attributed to its immunosuppressive action. Here we show that the beneficial effect of CsA on proteinuria is not dependent on NFAT inhibition in T cells, but rather results from the stabilization of the actin cytoskeleton in kidney podocytes. CsA blocks the calcineurin-mediated dephosphorylation of synaptopodin, a regulator of Rho GTPases in podocytes, thereby preserving the phosphorylation-dependent synaptopodin-14-3-3 beta interaction. Preservation of this interaction, in turn, protects synaptopodin from cathepsin L-mediated degradation. These results represent a new view of calcineurin signaling and shed further light on the treatment of proteinuric kidney diseases. Novel calcineurin substrates such as synaptopodin may provide promising starting points for antiproteinuric drugs that avoid the serious side effects of long-term CsA treatment.

Corticosteroid-resistant nephrotic syndrome with focal and segmental glomerulosclerosis : an update of treatment options for children

Corticosteroid-resistant nephrotic syndrome (CRNS) with focal and segmental glomerulosclerosis (FSGS) is a heterogeneous disorder and the most severe and frequent type of all glomerulopathies in children leading to end-stage renal failure. The podocyte is at the center of development and progress of FSGS; this unique cell type plays a major role in the integrity of glomerular structure and permeability. The rate of complete remission of CRNS after induction therapy using different immunosuppressant agents is reported to range between 30% and 84%, depending on the treatment schedule and on the underlying defects of FSGS. Children with genetic types of FSGS barely respond to immunosuppressant therapies and over-treatment prior to transplantation should be avoided. The response of children with an idiopathic type of FSGS to immunosuppressants is superior to those with genetic FSGS. However, many children with idiopathic FSGS do not enter complete remission if they are under-treated, for example, with short-term immunosuppressant monotherapies. If immunosuppressant treatment fails, these patients will have to undergo renal transplantation. However, as unknown pathogenetic mechanisms may persist, more than one-third of these patients with idiopathic FSGS develop a rapid recurrence of CRNS that responds poorly to further long-term therapeutic attempts. In contrast with previously published data, this review takes into account recently identified genetic etiologies of CRNS, and superior results with long-term combination therapy in idiopathic forms to avoid over- and under-treatment.

Rituximab failed to improve nephrotic syndrome in renal transplant patients with recurrent focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) recurs in 30% of patients with FSGS receiving a first renal transplant and in over 80% of patients receiving a second transplant after a recurrence. Recurrence often leads to graft failure. The pathogenesis remains unknown and may involve a circulating permeability factor that initiates injury to the glomerular capillary. There are anecdotal reports of pediatric patients with posttransplant lymphoproliferative disorder (PTLD) and recurrent FSGS who have had remission of proteinuria after treatment with rituximab. These observations have prompted speculation that B cells may play a role in the pathogenesis of recurrent FSGS. We report four consecutive adult patients with early recurrent FSGS refractory or dependent on plasmapheresis who received rituximab (total dose 2000-4200 mg). None of the patients treated with rituximab achieved remission in proteinuria, and one patient experienced early graft loss. In these four adult renal transplant patients with recurrent FSGS, rituximab failed to diminish proteinuria.

Renin-angiotensin axis blockade reduces proteinuria in presymptomatic patients with familial FSGS

Familial and genetic forms of focal segmental glomerulosclerosis (FSGS) are associated with six different mutations in genes affecting the podocyte (NPHS2, ACTN4, CD2AP, WT1, TRPC6, and PLCE1). Immunosuppressive agents are often unsuccessful in treating this condition. Data regarding the efficacy of renoprotection through blockage of the renin-angiotensin axis is lacking. We describe three children from two different families with familial FSGS in whom partial to complete remission of proteinuria was attained through early blockade of the renin-angiotensin axis. In addition, there was no deterioration of renal function. We speculate that presymptomatic patients with normal renal function who have genetic or familial FSGS may benefit from early blockade of the renin-angiotensin axis and that this may also prevent progressive renal disease.

Efficacy of steroid pulse, plasmapheresis, and mizoribine in a patient with focal segmental glomerulosclerosis

There have been few reports on successful treatment for focal segmental glomerulosclerosis (FSGS) complicated by leukoencephalopathy. We report the efficacy of the steroid pulse and mizoribine (MZB) combined with plasmapheresis (PP) for a case of FSGS with leukoencephalopathy induced by cyclosporine (CyA). The patient was a 4-year-old boy with FSGS who presented with steroid-resistant nephrotic syndrome (NS) and was treated with CyA. On the 7th day after starting CyA, he complained of one visual disorder, and hypertension and tonic convulsions were observed. Electroencephalography (EEG) revealed generalized slow waves, and magnetic resonance imaging (MRI) disclosed high signal intensity in the white matter. A diagnosis of leukoencephalopathy induced by CyA was made on the basis of these findings with the improvement in clinical manifestations upon discontinuation of CyA. We treated the patient with steroid pulse therapy and MZB combined with PP, and the proteinuria gradually decreased and only microscopic hematuria remained. We report that steroid pulse and MZB combined with PP may be an effective treatment in a patient with FSGS complicated by CyA-induced leukoencephalopathy.

Guidelines on the use of therapeutic apheresis in clinical practice—Evidence-based approach from the apheresis applications committee of the American society for apheresis

The American Society for Apheresis (ASFA) Apheresis Applications Committee is charged with a review and categorization of indications for therapeutic apheresis. This elaborate process had been undertaken every 7 years resulting in three prior publications in 1986, 1993, and 2000 of "The ASFA Special Issues." This article is the integral part of the Fourth ASFA Special Issue. The Fourth ASFA Special Issue is significantly modified in comparison to the previous editions. A new concept of a fact sheet has been introduced. The fact sheet succinctly summarizes the evidence for the use of therapeutic apheresis. A detailed description of the fact sheet is provided. The article consists of 53 fact sheets devoted to each disease entity currently categorized by the ASFA. Categories I, II, and III are defined as previously in the Third Special Issue. However, a few new therapeutic apheresis modalities, not yet approved in the United States or are currently in clinical trials, have been assigned category P (pending) by the ASFA Clinical Categories Subcommittee. The diseases assigned to category IV are discussed in a separate article in this issue.

Bigenic mouse models of focal segmental glomerulosclerosis involving pairwise interaction of CD2AP, Fyn, and synaptopodin

Focal segmental glomerulosclerosis (FSGS) is the most common primary glomerular diagnosis resulting in end-stage renal disease. Defects in several podocyte proteins have been implicated in the etiology of FSGS, including podocin, alpha-actinin-4, CD2-associated protein (CD2AP), and TRPC6. Despite our growing understanding of genes involved in the pathogenesis of focal segmental sclerosis, the vast majority of patients with this disease, even those with a familial linkage, lack a clear genetic diagnosis. Here, we tested whether combinations of genetic heterozygosity (bigenic heterozygosity) that alone do not result in clinical kidney disease could function together to enhance susceptibility to glomerular damage and FSGS. Combinations of Cd2ap heterozygosity and heterozygosity of either synaptopodin (Synpo) or Fyn proto-oncogene (Fyn) but not kin of IRRE like 1 (Neph1) resulted in spontaneous proteinuria and in FSGS-like glomerular damage. These genetic interactions were also reflected at a functional level, as we found that CD2AP associates with Fyn and Synpo but not with Neph1. This demonstrates that bigenic heterozygosity can lead to FSGS and suggests that combined mutations in 2 or multiple podocyte genes may be a common etiology for glomerular disease.

Effect of immunoadsorption on refractory idiopathic focal and segmental glomerulosclerosis

A case of a young adult with refractory nephrotic syndrome due to focal segmental glomerulosclerosis is reported. Several treatments had been used without success including steroids, cyclophosphamide, cyclosporine A, tacrolimus, and mycophenolate mofetil. Immunoadsorption was performed as a last resort to manage the nephrotic syndrome, which led to a drastic urinary protein reduction. We review the literature supporting immunoadsorption in primary focal segmental glomerulosclerosis.